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1.
The study was conducted in filarial endemic area for various clinical presentations and diagnosis of occult filariasis. A total of 157 cases of various clinical presentations namely tropical pulmonary eosinophilia, monoarthritis, polyarthritis, glomerulonephropathy, tenosynovitis, inguinal lymphadenopathy, generalised lymphadenopathy, retroperitonial lymphadenopathy, endomyocardial fibrosis and acute conjunctivitis were screened for filarial antigen and antibody by enzyme linked immunosorbent assay (ELISA). Out of 157 cases, 107 cases were positive for antigen or antibody, suggesting the role of filarial infection in these clinical presentations. All the 107 cases were treated with diethylcarbamazine citrate (DEC) and some of the patients who were followed showed relief in signs and symptoms. Hence assay of filarial antigen and/or antibody may be useful for diagnosing occult filarial syndromes for better management and further appropriate treatment.  相似文献   

2.
The effect of sodium pentosan polysulphate (SPP), was studied in relation to certain blood and erythrocyte membrane parameters in calcium oxalate stone forming rats. Calcium oxalate stones were induced by feeding the rats with 3% w/w sodium glycollate. Fibrinogen, haemoglobin and serum protein levels did not show any variation with the treatment procedures. Serum mucoprotein and protein bound carbohydrates-hexosamine and sialic acid-were increased significantly in the rats receiving calculogenic (CPD) and attained nearly normal levels with SPP treatment. In contrast, hexuronic acid level was decreased in the CPD group and SPP administration increased the level of hexuronic acid in the treated groups. Erythrocyte membrane Ca2+-ATPase activity was increased in stone forming rats and SPP administration brought a reduction in the above enzyme activity. Changes in Membrane Mg2+- and Na+, K+-ATPases were minimal. Membrane cholesterol and phospholipids were also raised significantly in stone formers, SPP treatment reduced the membrane cholesterol levels in both controls and stone formers. Phospholipids were also decreased moderately. The above observations suggest that SPP is safe for administration in urolithiatic condition without adverse effects.  相似文献   

3.
Calcium—activated neutral proteases (CANP) were examined in the subcellular fractions of the skeletal muscle from Duchenne muscular dystrophy patients and healthy individuals. Both and m CANP were detected in subcellular fractions of skeletal muscle. An increase in the quantity of CANP in subcellular particles of DMD muscle was observed. A 33 fold rise in the concentration of calcium in nuclei of dystrophic muscle was noted followed by cytosol, myofibrils, microsomes and mitochondria.  相似文献   

4.
A potent hypoglycaemic principle was isolated by us earlier from the seeds of fenugreek. We have now investigated its hypocholesterolemic effect. Hypercholesterolemia was induced in two groups of rabbits (5 each) by feeding orally cholesterol 100 mg/kg/day for one week. From 8th day group I animals (controls) received the same dose of cholesterol for 4 more weeks. Group II animals (treated) were given along with the same dose of cholesterol fenugreek principle at 50 mg/kg/day for 4 weeks. Fenugreek principle not only prevented the elevation of serum cholesterol, (LDL+VLDL)c, triacylglycerols and the ratios of total cholesterol/HDLc and (LDL+VLDL)c/HDLc, but also brought down most of these values. Blood glucose levels were normal. The study shows that the same hypoglycaemic principle has hypocholesterolemic effect also.  相似文献   

5.
The microbicidal capacity of polymorphonuclear leucocytes of diabetic and control subjects was evaluated by estimating the release of lysosomal enzymes viz beta-glucuronidase, lysozyme, acid phosphatase, alkaline phosphatase, in response to a particulate stimulus-serum treated zymosan (STZ). The cells untreated and pretreated with cytochalasin B were exposed to STZ The total enzyme activities were estimated after cell lysis. The total enzyme activities were not altered in diabetic subjects as compared to control subjects. The release of lysosomal enzymes by cells pretreated with cytochalasin B was high as compared to untreated cells. The release of lysosomal enzymes from the cells isolated from diabetic patients, untreated and pretreated with cytochalasin B was reduced as compared to controls. The findings of the present study that the total lysosomal enzyme activities are normal while the release of these enzymes in response to stimulus is impaired in diabetics, suggest that the bactericidal capacity of these cells which involves phagocytosis is impaired in these patients.  相似文献   

6.
The urinary excretion patterns of N-acetyl-β-D-glucosaminidase (NAG), alanine aminopeptidase (AAP) and protein/creatinine ratio (UP/UCR) were studied in 133 diabetic subjects under treatment, 7 patients with established diabetic nephropathy (DN) and 79 carefully selected (age-matched) healthy subjects. NAG, AAP and UP/UCR were highly elevated in DN, while in diabetics urinary NAG levels correlated well with the degree of long-term metabolic control indicated by glycosylated hemoglobin (GHB or Hba1). Both AAP and UP/UCR were found to be more sensitive than NAG, but less specific. Urinary NAG and AAP assays thus offer simple, sensitive and non-invasive techniques for prognostic indication of the onset of microangiopathic changes in long-term diabetic subjects.  相似文献   

7.
Zinc (Zn), copper (Cu), magnesium (Mg) and retinol levels were studied in serum and tissue of the patients with prostatic carcinoma (Ca), benign hyperplasia (BHP) and control subjects. Zinc and retinol levels were low in both serum and tissues of patients with carcinoma, while in BHP, both zinc and retinol level were decreased. Copper levels were high in serum and tissues of both BHP as well as carcinoma patients. Magnesium levels were elevated in both serum and tissues of cancerous patients. The results indicate that Zn, Cu, and Mg metabolism is disturbed in malignancy.  相似文献   

8.
Serum phenytoin levels were measured in grand mal epilepsy patients receiving diphenyl hydantoin. The drug levels were correlated with various biochemical parametres. A linear relationship between the levels of diphenyl hydantoin and creatinine was observed. This positive correlation coefficient was found to be statistically signifficant. This correlation may be related to a positive Jaffe’s reaction seen with the chromogen diphenyl hydantoin.  相似文献   

9.
Blood haemoglobin, serum iron, iron binding capacity, transferrin saturation and ferritin levels were determined in two groups of mothers as well as their cords—strict vegetarians (lactovegetarians) and non-vegetarians (omnivores), closely comparable in age, weight, parity and gestation period but differing in their diet and food habits. All these parameters, except total iron binding capacity, were found to be significantly lower in vegetarian mothers and their cords as compared to nonvegetarian mothers and their cords, respectively, despite receiving supplemental iron for six months. Further, there was a greater incidence of anemia and iron deficiency in mothers consuming only vegetarian diet. Moreover, a significant correlation existed between mother's ferritin to cord ferritin confirming that maternal iron deficiency does affect neonatal iron status. All these observations suggest that strict vegetarian mothers as well as their newborns have a greater incidence and risk of anemia and iron deficiency.  相似文献   

10.
The present studies with aluminium chloride given in drinking water showed marked inhibition in the activities of intestinal brush border membrane marker enzymes, namely alkaline phosphatase, acetyl cholinesterase, γ-glutamyl transpeptidase and sucrase. Moreover, a significant depression in the levels of membrane constituents, viz phospholipids, cholesterol, hexoses and sialic acid following aluminium chloride treatment was also observed. On the basis of these studies it may be concluded that if aluminium is taken in high quantities it may alter the structure and functioning of the intestinal brush border membrane, which in turn may lead to the improper digestion and reduced nutrient uptake from the small intestine.  相似文献   

11.
Uterine fluid, basically the endometrial secretion, is in dynamic exchange by influx and efflux with the oviducal and cervical fluids. During investigation the uterine fluid of both parous and IUCD women was collected and evaluated for inorganic phosphorus and cholesterol. The results of parous women were compared with the results of IUCD women. The trend of fluctuation in inorganic phosphorus concentration during different phases of menstrual cycle were same in both parous and IUCD women. But there was an increase in concentration in case of IUCD women in all stages of the menstrual cycle. After comparison with parous women a decrease in uterine fluid cholesterol concentration during proliferative period and increase during luteal period of IUCD women was observed. This increase in inorganic phosphorus and decrease and an increase in cholesterol concentration in IUCD women might be responsible in making uterine fluid environment unfavourable for sperm survival and blastocyst implantation.  相似文献   

12.
Membrane hydrophobicity and slalidase activity of normal Poly morphonuclear Leucocyte were significantly enhanced when incubated with DSF. As a consequence, internalisation ofE. coli andS. aureus (opsonised or unopsonised) were greatly dimnished, internalisation ofE. coli being higher in either category. Although, increase in hydrophobicity of the membrane correlated well with the time of decrease of particle internalisation (both at 30 min.), enhancement of sialidase activity did not coincide with the said alterations.  相似文献   

13.
Fuchs (2010 Fuchs, C. 2010. Labor in information capitalism and on the Internet. The Information Society 26:179–196.[Taylor & Francis Online], [Web of Science ®] , [Google Scholar], 2012 Fuchs, C. 2012. With or without Marx? With or without capitalism?: A re-joinder to Adam Arvidsson and Eleanor Colleoni. tripleC 10 (2):633–45. [Google Scholar]) argues that users of social media produce value and surplus value in the Marxian sense. Arvidsson and Colleoni (2012 Arvidsson, A., and E. Colleoni. 2012. Value in information capitalism and on the Internet. The Information Society 28:135–50.[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) critique this hypothesis, claiming that Marx's theory of value is irrelevant to the regime of value production on social media platforms in particular and in informational capitalism in general. They claim that the affective relations and financial speculations that generate value on social media are not dependent on labor time. This article critically engages Fuchs, and Arvidsson and Colleoni, by revisiting Marx's theory of value. Contra Fuchs, we argue that audiences do not produce value and surplus value—neither for social nor for mass media. Contra Arvidsson and Colleoni, we argue that so-called affective relations (philia) do not produce value either. Instead we demonstrate that social media generate revenue from four primary sources—by leasing advertisement space to generate advertisement rent, by selling information, by selling services to advertisers, and by generating profits from fictitious capital and speculative windfalls. All four, we argue, can be adequately explained by Marx's theory of value.  相似文献   

14.

Introduction:

Intensive exercising may significantly damage muscles which is reflected in pain, fatigue and the increase of muscle proteins concentrations in blood such are creatinin kinase (CK), lactic dehydrogenase (LD), myoglobin (MB) and other biochemical parameters including urea serum concentration (SU). Biochemical markers vary with age, sex, race, muscle mass, physical activity and climate conditions. They also assist us in determining the limit between the capacity for adaptation to given training process which results in supercomepensation and in condition of overtraining (OT), in the case of load that exceeds the physiologic potential of regeneration. Concerning the problem of diagnosis and explanation of the symptoms of overtraining, markers that can apply reliably and with sufficient sensitivity and simplicity of interpretation in the praxis are sought. It is critical to take into account difference among individuals and groups that could hamper the interpretation.

The most frequently used markers:

The most frequently used biomarkers that provide us with the information on physical activity and on the amount of load through exercise are CK, SU and LD. Level of serum retaining kinas has been measured and interpreted for years as part of different scientific and professional investigations and presents one of basic parameters for determining the level of muscle damage. It reaches maximal concentration of the fourth day of exercising which depends on the type of exercise and the nature of stress triggered by exercise but also on individual characteristics.The level of serum urea presents marker of nitric compounds metabolism and is the principle chemical substance in the urine of mammals. It is thus possible to draw a parallel between the increases of serum urea concentration on increased degradations of proteins. Significant fall of serum amino acid levels occurs after sixty to seventy minutes of exercising with the increase of urea and free tyrosine and these changes have high correlation with the duration and intensity of.LD changes are important index of well-trained sportsmen and their capability to withstand the pace and force during strain in the training process. The level of LD is a good index of exercise intensity and marker of metabolic exchange in tissues whose concentration in serum is dependent of cell damage.

Conclusion:

There is not a single, unique parameter that would provide enough valuable information for the estimation of the quality of exercising, amount of load and identification of overtraining. Delayed measurement of biomarkers is far from ideal, but it is obvious that the amount of stress/ load in training is the most important factor for the development of state of overtraining. Daily body weight control, diet, biochemical indices values and the input of water should be known and standardized before measurements. For the most of parameters determination of basal levels are needed in specific populations for more accurate interpretation and evaluation of results. The sampling process itself should be under the most strict conditions of standardization by repeating measurement at least every third day. Dependence of mentioned parameters (SU, CK, LD) on exercise intensity varies among individuals and without these additional measurements and subpopulation evaluations it is difficult to come to conclusions with certainty as well as to come to conclusions on causative correlations of training load and dynamic in biochemical parameters.Biochem Med (Zagreb) 2013 Jun; 23(2): A57–A58. Published online 2013 Jun 15. doi: 10.11613/BM.2013.027

Common sports injuries

Miljenko FranićAuthor information Copyright and License information DisclaimerDubrava University Hospital, ZagrebCorresponding author: rh.dbk@cinarfm©Copyright by Croatian Society of Medical Biochemistry and Laboratory MedicineThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Sports injuries are injuries that occur in athletic activities and can be broadly classified as either traumatic or overuse injuries. Traumatic injuries because of the dynamic and high collision are nature of some sports. Overuse injuries cause wear and tear on the body, particularly on joints subjected to repeated activity.At every age, competitive and recreational athletes sustain a wide variety of soft tissue, bone, ligament, tendon and nerve injuries, caused by direct trauma or repetitive stress. Different sports are associated with different patterns and types of injuries, whereas age, gender and type of activity influence the prevalence of injuries. Sports trauma commonly affects joints of the extremities or the spine.The hip, knee and ankle are at risk of developing osteoarthritis (OA) after injury or in the presence of malalignment, especially in association with high impact sport. Spine pathologies are associated more commonly with certain sports. Upper extremity syndromes caused by a single stress or by repetitive micro-trauma occur in a variety of sports.Random control trials expose some subjects, but not others, to an intervention. This is more clinical in nature and not typically appropriate for the study of injury patterns. Cohort studies monitor both injured and non-injured athletes, thereby providing results on the effects of participation. Case-control studies monitor only those athletes who suffered an injury. The Ideal study would be Cohort design conducted over several teams, with longitudinal prospective data collection and one recorder where possible, as well as uniformity of injury definition across sports so comparisons between studies can be made accurately.Physical injury is an inherent risk in sports participation and, to a certain extent, must be considered an inevitable cost of athletic training and competition. Injury may lead to incomplete recovery and residual symptoms, drop out from sports, and can cause joint degeneration in the long term.Advances in arthroscopic techniques allow operative management of most intraarticular post-traumatic pathologies in the lower and upper limb joints, but long-term outcomes are not available yet. It is important to balance the negative effects of sports injuries with the many benefits that a serious commitment to sport brings.Biochem Med (Zagreb) 2013 Jun; 23(2): A58–A59. Published online 2013 Jun 15. doi: 10.11613/BM.2013.027

Determination of sample size and number of study groups in sport studies

Mladen PetrovečkiAuthor information Copyright and License information DisclaimerDepartment of Laboratory Diagnosis, Dubrava University Hospital, Zagreb, Croatia, and Department of Medical Informatics, Rijeka University School of Medicine, RijekaCorresponding author: rh.irdem@pnedalm;©Copyright by Croatian Society of Medical Biochemistry and Laboratory MedicineThis is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.  相似文献   

15.
20 male dogs weighing 20–25 kg were assigned an exercise schedule for 2 months. Blood samples were collected before exercise and again at the end of the exercise schedule, thus each dog served as its own control. Physical exercise caused a significant reduction in total lipids, total cholesterol and low density lipoprotein (LDL) cholesterol, whereas unesterified cholesterol (UC), high density lipoprotein (HDL) and very low density lipoprotein (VLDL) cholesterol remained unaffected. However, the ratio of HDL cholesterol to LDL cholesterol raised significantly from 0.36±0.01 to 0.58±0.01. Aerobic exercise also resulted in an increase in creatinine phosphokinase (CPK) level. The results show that aerobic exercise programme can significantly affect serum cholesterol and lipoprotein concentration.  相似文献   

16.
Circadian periodicity of plasma lipid peroxides and serum ascorbic acid and uric acid levels were studied in one hundred renal stone formers (55 women and 45 men; age 20–60 years) and 50 clinically healthy volunteers (21 women and 29 men; age 21–45 years) with diurnal activity from 06:00 to 22:00 and nocturnal rest. A marked circadian variation was demonstrated by population-mean-cosinor for all studied variables in stone formers and healthy subjects. By comparison to the healthy controls, parameter tests indicate that the stone formers had a higher MESOR (±SE) of MDA (2.90 ± 0.03 vs. 2.28 ± 0.06; F = 94.929, p < 0.001), a lower MESOR of serum ascorbic acid (0.722 ± 0.010 vs. 0.839 ± 0.10; F = 32.083, p < 0.001), and a similar MESOR of serum uric acid. Furthermore, the patients also differed from the healthy subjects in terms of their circadian amplitude and acrophase (tested jointly) of all three variables (p < 0.001). The demonstration herein of a circadian rhythm in MDA, serum ascorbic and uric acid suggests that these variables could also serve as markers to optimize the timing of treatment and to assess the patient’s response to treatment for further management.  相似文献   

17.
This commentary supplements the work of a creative practice research project that generates new ways of thinking about innovation and entrepreneurial processes. Our creative method, underwritten by the logic of sensation and presented in film format, operates as an alternative form of research in these fields, where results are normally conveyed in book or journal paper. Film-based research has developed distinctive qualitative, empirical and theoretical vocabularies that can expand the nature and range of evidence, argument and expression across the broad range of innovation and entrepreneurship studies. 600 Mills, the film that accompanies this paper, is available at https://doi.org/10.1080/08109028.2017.1336011.  相似文献   

18.
Determining the thermal conductivity of iron alloys at high pressures and temperatures are essential for understanding the thermal history and dynamics of the Earth''s metallic cores. The authors summarize relevant high-pressure experiments using a diamond-anvil cell and discuss implications of high core conductivity for its thermal and compositional evolution.

The thermal conductivity of iron alloys is a key to understanding the mechanism of convection in the Earth''s liquid core and its thermal history. The Earth''s magnetic field is formed by a dynamo action that requires convection in the liquid core. Present-day outer core convection can be driven by the buoyancy of light-element-enriched liquid that is released upon inner core solidification in addition to thermal buoyancy associated with secular cooling. In contrast, before the birth of the inner core, the core heat loss must be more than the heat conducted down the isentropic gradient in order to drive convection by thermal buoyancy alone, which can be a tight constraint upon the core thermal evolution.Recent mineral physics studies throw the traditional value of the Earth''s core thermal conductivity into doubt (Fig. ​(Fig.1).1). Conventionally the thermal conductivity of the outer core had been considered to be ∼30 W m−1 K−1, an estimate based on shock experiments and simple physical models including the Wiedemann-Franz law: κel = LTρ−1, where κel, L, T and ρ are electronic thermal conductivity, Lorenz number, temperature and electrical resistivity, respectively [1]. Such relatively low core conductivity indicates that liquid core convection could have been driven thermally even with relatively slow cooling rate. However, in 2012–2013, our conventional view was challenged by both computational and experimental studies showing much higher core conductivity [2–4].Open in a separate windowFigure 1.(a) Electrical resistivity and (b) thermal conductivity values at the top of the Earth''s core in the literature [1,2,4–7,9,16]. Filled symbols were calculated on the basis of the Wiedemann-Franz law with ideal Lorenz number (L0 = 2.44 × 10−8 W Ω K−2). Gray bands indicate (a) the range of saturation resistivity [9] and (b) thermal conductivity computed from the saturation resistivity and the Wiedemann-Franz law.Since then, experimental determinations of the thermal conductivity of iron and alloys have been controversial (Fig. ​(Fig.1).1). Ohta et al. [5] measured the electrical resistivity of iron under core conditions in a laser-heated diamond-anvil cell (DAC). The results demonstrate relatively high thermal conductivity of ∼90 W m−1 K−1 for liquid Fe-Ni-Si alloy based on their measured resistivity for pure iron, Matthissen''s rule and Wiedemann-Franz law, which is compatible with ab initio simulations [2,4]. On the other hand, flash laser-heating and fast thermal radiation detection experiments demonstrated the low core conductivity of 20–35 W m−1 K−1 based on finite element method simulations [6,7], in accordance with the traditional estimate [1]. Since transport properties that describe non-equilibrium phenomena are difficult to measure, the fact that determinations of the iron conductivity under core conditions have become viable these days is a remarkable success in mineral physics. Nevertheless, the discrepancy in core conductivity makes a big difference in the expected age of the inner core, mechanism of liquid core convection and thermal history [3].Despite a number of subsequent studies based on a variety of different techniques, we still see a dichotomy of proposed core conductivity values (Fig. ​(Fig.1).1). The ‘saturation’ resistivity, which is derived from the fact that the mean free path of electron–phonon interaction cannot be longer than the interatomic distance, gives the lower bound for conductivity. Such saturation resistivity lies between two clusters of reported high and low resistivity values. While the resistivity saturation is important in highly resistive transition metals and their alloys [3,8] (Fig. ​(Fig.2),2), the conventional estimate [1] did not include the effect of saturation in their models, which resulted in much higher resistivity than the saturation value and hence low core conductivity. The core electrical resistivity measured by recent DAC experiments [3,5,9] shows resistivity saturation (Fig. ​(Fig.2),2), demonstrating the high core conductivity as far as the Wiedemann-Franz law holds with ideal Lorenz number (Fig. ​(Fig.1).1). Additionally, since temperature has a large effect on resistivity, temperature gradient in a laser-heated sample is an issue. An internally-resistance-heated DAC provides homogenous and stable sample heating and is thus a promising technique for conductivity measurements at high pressure and temperature (P–T) [9]. The validity of the Wiedemann-Franz law under extreme conditions has also been an issue. Simultaneous measurements of the electrical resistivity and the thermal conductivity of iron alloy under core high P–T conditions will provide decisive evidence for it.Open in a separate windowFigure 2.Temperature response of the electrical resistivity of (a) fcc iron estimated at 1 bar [8] (blue curve) and (b) hcp iron at 115 GPa [5]. Red curve and black line with gray uncertainty band indicate the predicted resistivity based on the Bloch-Grüneisen model with and without the resistivity saturation, respectively.As introduced above, the most recent high P–T measurements for Fe containing 2, 4, 6.5 wt.% Si using an internally-resistance-heated DAC have demonstrated that the thermal conductivity of Fe-12.7 wt.% (22.5 at.%) Si is ∼88 W m−1 K−1 at core-mantle boundary (CMB) conditions when the effects of resistivity saturation, melting and crystallographic anisotropy at measurements are taken into account [9] (Fig. ​(Fig.1).1). Thermal conductivity of Fe-10 at.% Ni-22.5 at.% Si alloy, a possible outer core composition, could be ∼79 W m−1 K−1 considering the impurity effect of Ni [10]. Si exhibits the largest ‘impurity resistivity’, indicating that the 79 W m−1 K−1 is the lower bound for the thermal conductivity of the Earth''s liquid core. The core thermal evolution models by Labrosse [11] demonstrated that if liquid core convection has been driven by thermal buoyancy with the core thermal conductivity of 79 W m−1 K−1 at the CMB and no radiogenic heating in the core, the CMB temperature is calculated to be ∼5500 K at 3.2 Ga and ∼4800 K at 2.0 Ga. Such high CMB temperature suggests that the whole mantle was fully molten until 2.0–3.2 Ga. It is not consistent with geological records, calling for a different mechanism of core convection.Chemical buoyancy may be an alternate means of driving convection in the core from the early history of the Earth. It has been proposed that the compositional buoyancy in the core could arise from the exsolution of MgO, SiO2 or both [12–14]. Recent core formation models based on the core-mantle distributions of siderophile elements suggest that core metals segregated from silicate at high temperatures, typically at 3000–4000 K and possibly higher [13,15], which enhances the incorporation of lithophile elements including Si and O, and possibly Mg into metals. It is suggested that the (Si, O)-rich liquid core may have become saturated with SiO2 upon secular cooling [14]. Indeed, the original core compositions proposed in recent core formation models include Si and O beyond the saturation limit at CMB conditions [15], i.e. 136 GPa and 4000 K, leading to SiO2 crystallization [13]. The rate of SiO2 crystallization required to sustain geodynamo is as low as 1 wt.% per 109 years, which corresponds to a cooling rate of 100–200 K Gyr−1 [14]. The most recent model of the core compositional evolution by Helffrich et al. [13] showed that MgO saturation follows SiO2 saturation only when >1.7 wt.% Mg in the core. If this is the case, in addition to solid SiO2, (Mg, Fe)-silicate melts exsolve from the core and transfer core-hosted elements such as Mo, W and Pt to the mantle. The core-derived silicate melts may have evolved toward FeO-rich compositions and now represent the ultra-low velocity zones above the CMB.  相似文献   

19.
A flow redirection and single cell immobilization method in a microfluidic chip is presented. Microheaters generated localized heating and induced poly(N-isopropylacrylamide) phase transition, creating a hydrogel that blocked a channel or immobilized a single cell. The heaters were activated in sets to redirect flow and exchange the fluid in which an immobilized cell was immersed. A yeast cell was immobilized in hydrogel and a 4′,6-diamidino-2-phenylindole (DAPI) fluorescent stain was introduced using flow redirection. DAPI diffused through the hydrogel and fluorescently labelled the yeast DNA, demonstrating in situ single cell biochemistry by means of immobilization and fluid exchange.The ability to control microfluidic flow is central to nearly all lab-on-a-chip processes. Recent developments in microfluidics either include microchannel based flow control in which microvalves are used to control the passage of fluid,1 or are based on discrete droplet translocation in which electric fields or thermal gradients are used to determine the droplet path.2, 3 Reconfigurable microfluidic systems have certain advantages, including the ability to adapt downstream fluid processes such as sorting to upstream conditions and events. This is especially relevant for work with individual biomolecules and high throughput cell sorting.4 Additionally, reconfigurable microfluidic systems allow for rerouting flows around defective areas for high device yield or lifetime and for increasing the device versatility as a single chip design can have a variety of applications.Microvalves often form the basis of flow control systems and use magnetic, electric, piezoelectric, and pneumatic actuation methods.5 Many of these designs require complicated fabrication steps and can have large complex structures that limit the scalability or feasability of complex microfluidic systems. Recent work has shown how phase transition of stimuli-responsive hydrogels can be used to actuate a simple valve design.6 Beebe et al. demonstrated pH actuated hydrogel valves.7 Phase transition of thermosensitive poly(N-isopropylacrylamide) (PNIPAAm) using a heater element was demonstrated by Richter et al.8 Phase transition was also achieved by using light actuation by Chen et al.9 Electric heating has shown a microflow response time of less than 33 ms.11 Previous work10 showed the use of microheaters to induce a significant shift in the viscosity of thermosensitive hydrogel to block microchannel flow and deflect a membrane, stopping flow in another microchannel. Additionally, Yu et al.12 demonstrated thermally actuated valves based on porous polymer monoliths with PNIPAAm. Krishnan and Erickson13 showed how reconfigurable optically actuated hydrogel formation can be used to dynamically create highly viscous areas and thus redirect flow with a response time of  ～ 2?s. This process can be used to embed individual biomolecules in hydrogel and suppress diffusion as also demonstrated by others.15, 16 Fiddes et al.14 demonstrated the use of hydrogels to transport immobilized biomolecules in a digital microfluidic system. While the design of Krishnan and Erickson is highly flexible, it requires the use of an optical system and absorption layer to generate a geometric pattern to redirect flow.This paper describes the use of an array of gold microheaters positioned in a single layer polydimethylsiloxane (PDMS) microfluidic network to dynamically control microchannel flow of PNIPAAm solution. Heat generation and thus PNIPAAm phase transition were localized as the microheaters were actuated using pulse width modulation (PWM) of an applied electric potential. Additionally, hydrogel was used to embed and immobilise individual cells, exchange the fluid parts of the microfluidic system in order to expose the cells to particular reagents to carry out an in situ biochemical process. The PDMS microchannel network and the microheater array are shown in Figure ​Figure11.Open in a separate windowFigure 1A sketch of the electrical circuit and a microscope image of the gold microheaters and the PDMS microchannels. The power to the heaters was modulated with a PWM input through a H-bridge. For clarity, the electrical circuit for only the two heaters with gelled PNIPAAm is shown (H1 and V2). There are four heaters (V1-V4) in the “vertical channels” and three heaters (H1-H3) in the “horizontal” channel.The microchannels were fabricated using a patterned mould on a silicon wafer to define PDMS microchannels, as described by DeBusschere et al.17 and based on previous work.10 A 25 × 75 mm glass microscope slide served as the remaining wall of the microchannel system as well as the substrate for the microheater array. The gold layer had a thickness of 200 nm and was deposited and patterned using E-beam evaporation and photoresist lift-off.21 The gold was patterned to function as connecting electrical conductors as well as the microheaters.It was crucial that the microheater array was aligned with an accuracy of  ～ 20μm with the PDMS microchannel network for good heat localization. The PDMS and glass lid were treated with plasma to activate the surface and alignment was carried out by mounting the microscope slide onto the condenser lens of an inverted microscope (TE-2000 Nikon Instruments). While imaging with a 4× objective, the x, y motorized stage aligned the microchannels to the heaters and the condenser lens was lowered for the glass substrate to contact the PDMS and seal the microchannels.Local phase transition of 10% w/w PNIPAAm solution in the microchannels was achieved by applying a 7 V potential through a H-bridge that received a PWM input at 500 Hz which was modulated using a USB controller (Arduino Mega 2650) and a matlab (Mathworks) GUI. The duty cycle of the PWM input was calibrated for each microheater to account for differences in heater resistances (25?Ω to 52?Ω) due to varying lengths of on-chip connections and slight fabrication inconsistencies, as well as for different flow conditions during device operation. Additionally, thermal cross-talk between heaters required decreasing the PWM input significantly when multiple heaters were activated simultaneously. This allowed confining the areas of cross-linked PNIPAAm to the microheaters, allowing the fluid in other areas to flow freely.By activating the heaters in sets, it was possible to redirect the flow and exchange the fluid in the central area. Figure ​Figure22 demonstrates how the flow direction in the central microchannel area was changed from a stable horizontal flow to a stable vertical flow with a 3 s response time, using only PNIPAAm phase transition. Constant pressures were applied to the inlets to the horizontal channel and to the vertical channels. Activating heaters V1-4 (Figure ​(Figure2,2, left) resulted in flow in the horizontal channel only. Likewise, activating heaters H1 and H2 allowed for flow in the vertical channel only. In this sequence, the fluid in the central microchannel area from one inlet was exchanged with fluid from the other inlet. Additionally, by activating heater H3, a particle could be immobilised during the exchange of fluid as shown in Figure ​Figure33 (top).Open in a separate windowFigure 2Switching between fluid from the horizontal and the vertical channel using hydrogel activation and flow redirection with a response time of 3 s. A pressure of 25 mbar was applied to the inlet of the horizontal channel and a pressure of 20 mbar to the vertical channel. The flow field was determined using particle image velocimetry, in which the displacement of fluorescent seed particles was determined from image pairs generated by laser pulse exposure. Processing was carried out with davis software (LaVision).Open in a separate windowFigure 3A series of microscope images near heater H3 showing: (1a)-(1c) A single yeast cell captured by local PNIPAAm phase transition and immobilized for 5 min before being released. (2a) A single yeast cell was identified for capture by embedding in hydrogel. (2b) The cell as well as the hydrogel displayed fluorescence while embedded due to the introduction of DAPI in the surrounding region. (2c) The diffusion of DAPI towards the cell as the heating power of H3 is reduced after 15 min, showing a DAPI stained yeast cell immobilized.Particle immobilisation in hydrogel and fluid exchange in the central area of the microfluidic network were used to carry out an in situ biochemical process in which a yeast cell injected through one inlet was stained in situ with a 4′,6-diamidino-2-phenylindole (DAPI) solution (Invitrogen), which attached to the DNA of the yeast cell.18 A solution of yeast cells with a concentration of 5 × 107cells/ml suspended in a 10% w/w PNIPAAm solution was injected through the horizontal channel. A solution of 2μg/l DAPI in a 10% w/w PNIPAAm solution was injected through the vertical channel. A single yeast cell was identified and captured near the central heater, and by deactivating the heaters in the vertical channel, DAPI solution was introduced in the microchannels around the hydrogel. After immobilising the cell for 15 min, the heater was deactivated, releasing the cell in the DAPI solution. This process is shown in Figure ​Figure33 (bottom). The sequence of the heater activation and deactivation in order to immobilize the cell and exchange the fluid is outlined in the supplementary material.21Eriksen et al.15 demonstrated the diffusion of protease K in the porous hydrogel matrix,19 and it was therefore expected that DAPI fluorescent stain (molecular weight of 350 kDa, Ref. 20) would also diffuse. DAPI diffusion is shown in Figure 3(2b) in which the yeast cell shows fluorescence while embedded in the hydrogel. The yeast cell was released by deactivating the central heater and activating all the others to suppress unwanted flow in the microchannel. As a result, the single cell was fully immersed in the DAPI solution. Immobilization of a single cell allows for selection of a cell that exhibits a certain trait and introduction of a new fluid while maintaining the cell position in the field of view of the microscope such that a biochemical response can be imaged continuously.In summary, a microfluidic chip capable of local heating was used to induce phase transition of PNIPAAm to hydrogel, blocking microchannel flow, and thereby allowing for reconfigurable flow. Additionally, the hydrogel was used to embed and immobilise a single yeast cell. DAPI fluorescent stain was introduced using flow redirection, and it stained the immobilized cell, showing diffusion into the hydrogel. The versatile design of this microfluidic chip permits flow redirection, and is suitable to carry out in situ biochemical reactions on individual cells, demonstrating the potential of this technology for forming large-scale reconfigurable microfluidic networks for biochemical applications.  相似文献   

20.
Morphological plasticity is an important survival strategy for bacteria adapting to stressful environments in response to new physical constraints. Here, we demonstrate Escherichia coli morphological plasticity can be induced by switching stress levels through the physical constraints of periodic micro-nanofluidic junctions. Moreover, the generation of diverse morphological aberrancies requires the intact functions of the divisome- and elongasome-directed pathways. It is also intriguing that the altered morphologies are developed in bacteria undergoing morphological reversion as stresses are removed. Cell filamentation underlies the most dominant morphological phenotypes, in which transitions between the novel pattern formations by the spatial regulators of the divisome, i.e., the Min system, are observed, suggesting their potential linkage during morphological reversion.Most bacteria have evolved sophisticated systems to manage their characteristic morphology by orchestrating the spatiotemporal synthesis of the murein sacculus (peptidoglycan exoskeleton), which is known to be the stress-bearing component of cell wall and presides over de novo generation of cell shape.1 Morphological plasticity is attributed to a bacterial survival strategy as responding to stressful environments such as innate immune effectors, antimicrobial therapy, quorum sensing, and protistan predation.2 It comes of no surprise that stress-induced diversified morphology and mechanisms, ascribed to shape control and determination, have drawn great attention in both fundamental and clinical studies.3–6 The molecular mechanism to form filamentous bacteria has been revealed that both β-lactam antibiotics3 and oxidative radicals produced by phagocytic cells5 trigger the SOS response, promoting cell elongation by inactivating cell division via the blockade of tubulin-like FtsZ, known as the divisome initiator. While apart from the scenario of length control by the divisome-directed filamentation, the elongasome assembled by proteins associated with actin-like MreB complex1,7,8 helps the insertion of peptidoglycans into lateral cell wall, suggesting the role in the determination of cell diameter during cell elongation.Recently, additional mechanisms other than the divisome/elongasome-directed pathways of shape maintenance are discovered to regenerate normal morphology de novo from wall-less lysozyme-induced (LI) spheroplasts of E. coli via a plethora types of aberrant division intermediates.9 Similar morphological reversion from different aberrant bacterial shapes has been observed as squashed wild-type bacteria generated through sub-micron constrictions are released into connected microchambers.10 Previous work using the microfluidic approach focuses on the septation accuracy and robustness of constricted bacteria,11 but the reversion process of stress-released bacteria is not well studied and analyzed. In particular, the aberrant bacterial shape is mainly branched-type with bent and curved variants in the reverting bacteria, analogous to the aberrant intermediate found in the morphological reversion of LI spheroplasts with PBP5-defective mutant.9 Since bacteria suffering from starvation12 or confronting mechanical stresses exerted by phagocytosis and protistan grazing6 can induce morphological alterations, one could manipulate the stress levels of physical constraints by adopting repeated structures of sub-micron constricted channels (nanoslits) and microchambers,10,11 to select and enrich bacteria converting to specified aberrant intermediates. The stress incurred by the nanoslit on bacteria is about the mechanical intervention over de novo synthesis of the cell wall, which is the major factor causing morphological aberrancy, while the second environmental stress comes from bacterial growth in the restricted space of microchamber as bacteria proliferate to full confluency, resulting in growth pressure of high population density, nutrient deficiency, and the size reduction of bacteria.Here, we report the selection of distinctive bacterial morphologies by size shrinkage in the outlet cross-section (W × H = 1.5 × 1.5 μm) of the terminal microchamber in the periodic structures of nanoslit-microchamber (Figs. 1(a) and 1(b)). The fluidic structures were micropatterned on fused silica wafers by photolithography, fabricated through reactive ion etching (RIE) and inductively coupled plasma (ICP) etching, and encapsulated by cover glasses coated with polydimethylsiloxane (PDMS) or polysilsesquioxane (PSQ) layer as described earlier.13,14 Two days after the outgrowth of Escherichia coli (imp4213 [MC4100 ΔlamB106 imp4213]) loaded to the microfluidic device at 25 °C, bacteria started to penetrate into the nanoslit as they proliferated to full confluency in the first microchamber (Fig. 1(c)). It takes about 10 days for bacteria traversing 500 μm long (5 repeated nanoslit-microchamber units) via proliferations and being released from the outlet of the terminal microchamber. The narrowed outlet allows only bacteria with smaller diameters to be squeezed into the spacious and nutrient-rich region, thus it acts as a spatial filter to avoid the passage of branching bacteria with cross-sectional size larger than that of the outlet. The rationale of this design is to select aberrant bacteria prone to promote de novo shape regeneration other than the branched-type, which is the dominant morphology of reverting bacteria in the prior microfluidic constriction study.10 As anticipated, the stress-released bacteria through the narrowed outlet are therefore mostly filamentous (see statistical analysis for cell morphology in the supplementary material).15 However, it is noted that the aberrant morphology of lemon-like shape with tubular poles (Figs. 1(d-1), 1(d-3), and 1(d-11)) is developed about 3 h after the stress-released bacteria escaped through the outlet. Though the generation of the lemon-like aberrancy in bacteria has been reported in PBP5/7-defective E. coli mutant subjected to a high-level inhibition of both MreB and FtsZ, while the same mutant treated with low-level MreB inhibitor, together with antagonized-FtsZ, displays filamentous shape with varying diameters,16 these morphological aberrances can be observed in our system (Figs. 1(d-2) and 1(d-12)). Besides, a high-level inhibition of MreB in E. coli with an intact divisome function is known to cause round bacteria, resembling to the cell morphology of the bacteria shown in Fig. 1(d-4). Interestingly, parallel experiments using bacteria mutants carrying impaired regulatory functions in either the divisome (Min−) or the elongasome (MreB−) do not develop morphological plasticity (supplementary Fig. S1).15 Taken together, the filamentous and lemon-like variants selected from our microfluidic platform, while elaborating the morphological plasticity and reverting progression, require both the functional divisome/elongasome. Alternatively, the selection by the spatial filter does not fully exclude cells with aberrant shapes such as the branched-type with initial budding (Fig. 1(d-7)), cells with asymmetric cross-section perpendicular to the longitudinal axis (Figs. 1(d-2), 1(d-8), 1(d-9), 1(d-9′), and 1(d-10)), and those resembling to the morphological phenotypes of the division intermediates reported in the LI-spheroplasts carrying genetic defects on some non-cytoskeletal proteins (Figs. 1(d-5) and 1(d-6)). In particular, intracellular vesicles and cell autolysis are observed in some reverting bacteria (Figs. 1(d-5) and 1(d-6)), which are reminiscent to the phenomena reported in the division intermediates of the LI-spheroplasts lacking stress response system (Rcs) or some accessory proteins (PBP1B and LpoB). Unlike the bacteria grow with odd shapes under the stress of nanofluidic confinement only10 (Fig. 1(c)), all the morphological aberrancy reported here are developed in the reverting bacteria, which grow in the spacious and nutrition-rich environment and are free from physical constraints. Further investigations over the expression levels of the divisome/elongasome networks and the stress-response system in bacterial cells subjected to micro-nanofluidic junctions could be insightful in understanding their role in bacterial shape control.9Open in a separate windowFIG. 1.(a) Schematics of the microfluidic device used in this study with an H-shaped geometry (left upper panel), where repeated nanoslit (L×W×H = 50×10×0.4 μm)−microchamber (L×W×H = 50×50×1.5 μm) structures are bridged between two arms of the H-shaped microchannels (left lower panel and enlarged view in right panel). (b) Top-view layout of an individual channel in (a) with close view of the outlet in the terminal microchamber (orange: nanoslits; blue: microchambers). (c) Fluorescence micrograph of E. coli imp4213 penetrating a nanoslit (scale bar: 5 μm). (d) Bright-field micrographs for various cell morphology of the selected imp4213 released from the outlet (magenta arrows: cells with vesicles; scale bar: 5 μm). (e) Sequential bright-field micrographs of morphological reversion. T1–T3 indicate the time after bacteria escaping from the outlet. T1: 3 h; T2: 6 h; T3: 24 h. Scale bar: 10 μm.During the morphological reversion, the stress-released bacteria rapidly increase their size in the first 3 h after escaping from the terminal microchamber (T1 in Fig. 1(e)). Some filamentous bacteria even grow over 50 μm long, though such a morphological phenotype implicates the cessation of functional divisome. With active growth and proliferation, the progeny of stress-released bacteria increase their population but gradually reduce their size about 6 h after being released from the constriction stress (T2 in Fig. 1(e)). Fig. ​Fig.22 displays the marginal histograms for different shape factors, where Fig. 2(a) is the plot of the minimal Feret diameter (cell diameter) versus Feret diameter (cell length), i.e., the shortest versus the longest distance between any two points with parallel tangents along the cell peripheral, respectively, indicating that cell diameters are larger for reverting bacteria at T1 (mean ± S.E.M. = 1.89 ± 0.08 μm) with respect to T2 (1.51 ± 0.06 μm). Moreover, the histogram of Feret diameter depicts two major populations of the cell length for reverting bacteria at T1, which mostly resume to typical cell length at T2 (the median of Feret diameter = 3.33 μm; see statistical analysis for Fig. ​Fig.22 in the supplementary material).15 The shape factors of circularity (4π × [area]/[perimeter]2) and aspect ratio ([major axis]/[minor axis] for the cell geometry fitted to an ellipse) confirm the existence of dual populations for bacteria at T1 as well (Fig. 2(b)). About 24 h after escaping (T3 in Fig. 1(e)), almost all the progeny of stress-released bacteria regained the rod shape.Open in a separate windowFIG. 2.Marginal histograms for shape factors measured from the reverting imp4213 at T1 and T2. (a) Minimal Feret diameter (cell diameter) versus Feret diameter (cell length). (b) Circularity versus aspect ratio. N = 366 for T1 and N = 494 for T2.The bacterial size reduction of filamentous and lemon-like shape variants, though involving negative control of the divisome positioning by the spatial regulators of MinCDE system,17 is not completely understood as to how they coordinate in aberrant geometries. Besides, the filamentation of stress-released bacteria during the period of T1 to T2 implicates the inhibition of functional divisome. With minimal perturbation of the divisome by leaky expression of GFP-MinD and MinE (imp4213/Plac-gfpmut2::minD minE), the patterning dynamics of GFP-MinD in different bacterial morphology were time-lapse imaged during morphological reversion. Intriguingly, more than the standing-wave-like pattern of MinD denoted in filamentous E. coli,18 we discovered bidirectional drifting of two standing-wave-like patterns of MinD occur in most reverting bacteria filaments (supplementary Figs. S2(a) and S2(b)).15 The bidirectional drifting in the longitudinal direction of the cells may be emanating from the cell poles (the blue upper panel of Fig. 3(a) and supplementary Fig. S2(c)15) and the cylinder region (the blue lower panel of Fig. 3(a) and supplementary Fig. S2(d)15). Furthermore, the MinD pattern transitions from the standing to traveling waves are occasionally observed (the lower panel of Figs. 3(a) and supplementary Fig. S2(e)15). Notably, the standing-wave-like MinD patterns exhibit bidirectional drifting along the cell longitudinal direction and intermittently change directions, implying the competition between coexisting MinD patterns can be supported under filamentous geometry. Despite there have been observations of multiple wave-packet of traveling waves in filamentous cells,19 the mixture of distinct wave-like MinD patterns have never been experimentally reported. While most intriguingly, multiple drifting movements of wave-like MinD patterns potentiate the mitigation of periodic minima in time-averaged Min gradient in the reverting filamentous bacteria, suggesting the disability of proper divisome positioning for recovering the typical rod shape. Apart from the wave-like movements, amoeba-like motion of Min proteins has been shown in vitro upon synthetic minimal system, but never been verified in vivo.20 Strikingly, here amoeba-like motion of MinD is the dominant mode in lemon-like bacteria and the transitions between wave-like patterns and amoeba-like motion are supported even under filamentous geometry (Figs. 3(b) and 3(c), Multimedia view).Open in a separate windowFIG. 3.Kymographs for GFP-MinD dynamics in selected imp4213 cells during morphological reversion: (a) Mixture modes of standing wave packets and traveling wave. The left panel is the stacked fluorescence micrograph displaying cell shape (scale bar = 5 μm). The kymograph is derived from the filamentous cell indicated by the green arrow (scale bar: 120 s horizontal; 5 μm vertical), where the lower panel follows the upper panel in time. The yellow windows indicate bidirectional-drifting standing wave packets, while the green indicates traveling waves (see also supplementary Fig. S2).15 (b) Sequential fluorescence micrographs of GFP-MinD in lemon-shape imp4213 show amoeba-like motion, with the first left a bright-field image (scale bar: 10 μm). (c) Mixed modes of amoeba-like motion and waves in selected filamentous imp4213 cell indicated by the green arrow in the left panel (scale bar = 5 μm). The filamentous cells depicted in (a) and (c) locate at the top region while the lemon-shape cell in (b) at the central region of the movie (time stamp in min:s). (Multimedia view) [URL: http://dx.doi.org/10.1063/1.4892860.1]In summary, we have demonstrated that the development of bacterial morphological plasticity can be stress-induced by periodic physical constraints with intact functions of the divisome and elongasome-directed pathways. Through size exclusion, the constricted outlet structure designed in our microfluidic device is useful in selecting bacteria with plethora morphological aberrancies other than the branched type. Interestingly, disparate morphological changes, rather than those being directly induced under a stressful environment, can be generated in the stress-released bacteria experiencing morphological reversion. Further, the discovery of novel transitions between the Min patterns in most reverting bacteria implicates its regulatory effect of cell filamentation. However, by exploiting the micro-nanofluidic approach, further investigations of the mechanism underlying the development of morphological plasticity in bacteria adapting to physical constraints are expected in future studies to gain more insights into the molecular basis of shape generation.  相似文献   

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