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Biomedical subjects

M Sarkar

Publications and source records attributed to M Sarkar.

At least 19 recordsLinked to original sources
PubMed2006

Tuning the size and optical properties in molecular nano/microcrystals: manifestation of hierarchical interactions.

Intermolecular interactions, such as hydrogen bonding, dipolar and van der Waals, occurring in molecular crystals cover a range of magnitudes. As the crystal evolves from a relatively softer state in the nanoscopic size regime to a harder one in the microcrystalline and bulk solid state, the impact of the hierarchy of intermolecular interactions can be expected to emerge in a progressive fashion. The strongest interactions alone would be manifested at small sizes; as the crystal grows, the effect of the weaker ones will be added on, with the bulk crystals exhibiting the cumulative impact of the different interactions. We demonstrate this phenomenon through investigations of the solution, colloid, and solid state of a novel zwitterionic molecule based on the diaminodicyanoquinodimethane framework. A reprecipitation-digestion protocol is developed for the fabrication of nano/microcrystals of varying sizes. Microscopic and spectroscopic characterizations reveal tuning of the size and optical properties of this material. The optical absorption of the colloidal particles evolves with size towards that of the bulk solid, the emission showing a steady enhancement of intensity. Crystallographic investigations coupled with semiempirical computations provide a viable model to describe the range of observations in terms of the gradual accumulation of hierarchical intermolecular interactions.

Computer Simulation↗
PubMed2005

Is the yak (Poephagus grunniens L.) really a seasonal breeder?

Yaks are considered to be seasonally polyestrous and breeding occurs from July to November. Here we show that some yaks in peak non-breeding season do exhibit cyclic luteal activity without exhibiting any behavioral signs around expected estrus. A total of eight non-lactating yaks were selected from the Yak Farm belonging to National Research Centre on Yak for various sets of experiments. The animals were maintained as per semi range system of management. They were allowed to graze during daytime and fed concentrate mixture @2 kg/animal/day as per standard farm practices of the center. Blood samples were collected on alternate days for 30 days by jugular venipuncture from the yaks during peak breeding season (July to November) and from the same yaks in non-breeding season (February to March). The plasma samples were analysed for progesterone and estradiol-17beta by RIA and EIA procedures, respectively. During breeding season, the mean plasma progesterone at estrus was basal (<or=0.2 ng/ml) and there after started to increase and reached a peak at days 15-16 of the cycle and then declined rapidly to basal levels at estrus. Mean plasma estradiol-17beta concentrations were high at estrus and then declined to basal level at days 2-3 of the cycle. The mean plasma estradiol-17beta concentrations stayed low for the remaining part of the estrous cycle except for a small elevation, which was exhibited between days 6 and 12 of the cycle. During non-breeding season, in 50% of the animal studied, plasma progesterone and estradiol-17beta levels were at basal level. However, in the remaining animals distinct luteal activity was recorded in terms of plasma progesterone profile. High concentrations of progesterone were maintained in one animal, which suggested existence of cystic corpus luteum. The trend of progesterone and estradiol-17beta profiles in other three animals indicated that they could be cycling although they did not exhibit estrus symptoms. It was concluded from the present study that with improved nutritional support some yaks exhibit estrous cyclicity even during the non-breeding period of the year.

Animals↗
PubMed2005

Application of sensitive enzymeimmunoassays for oxytocin and prolactin determination in blood plasma of yaks (Poephagus grunniens L.) during milk let down and cyclicity.

Highly sensitive and specific enzymeimmunoassays for oxytocin and prolactin determination in yak plasma using the biotin-streptavidin amplification system and the second antibody coating technique were validated and applied for determining their profiles during milk let down and cyclicity in yaks. Oxytocin EIA was conducted taking duplicate 200 microl of unknown plasma samples and standards per well. The lowest detection limit was 0.2 pg/well, which corresponded to 1pg/ml plasma. Prolactin EIA was carried out directly in 50 microl of yak plasma. The sensitivity of EIA procedure was 5 pg/well prolactin, which corresponded to 0.1 ng/ml plasma. Mean plasma prolactin concentrations although high at estrus were not statistically different (P > 0.05) from the hormone concentrations on other days. Mean plasma prolactin concentrations during non-breeding season were significantly higher (P < 0.001) than that recorded in breeding season. Oxytocin and prolactin profiles were also obtained in two yaks before, during and after milking. A sharp release of oxytocin and prolactin shortly after udder stimulation was observed. High levels of oxytocin and prolactin were maintained during milking, falling sharply thereafter.

Animals↗
PubMed2005

[Computer-assisted arthrodesis of the sacroiliac joint].

Arthrodesis of the sacroiliac joint (SI) usually requires a large surgical exposure using the lateral approach. Computer-assisted surgery based on intraoperative 3D fluoroscopy imaging can reduce the approach to stab incisions. The clinical example shows the insertion of two screws and a cylindrical bone graft to achieve an arthrodesis of the SI joint. The intraoperatively navigated placement of implants and bone graft was performed only by stab incisions.

Adult↗
PubMed2005

Timing of ovulation in relation to onset of estrus and LH peak in yak (Poephagus grunniens L.).

The objective of the study was to determine the timing of ovulation in relation to onset of estrus and the preovulatory LH peak in yaks. For this purpose, a sensitive LH enzymeimmunoassay previously established in buffaloes was successfully validated for measuring the hormone in yak plasma. Plasma LH and progesterone were estimated from blood samples collected from eight non-lactating cycling yaks at 2 h intervals after estrus onset until 6 h after ovulation (ovulation was confirmed by palpation of ovaries per rectum). The mean+/-S.E.M. preovulatory plasma LH peak was 10.11+/-0.35 ng/ml with the values ranging from 8.75 to 11.51 ng/ml in individual yaks. The mean+/-S.E.M. duration of the LH surge was 7.25+/-0.55 h with a range of 6-10 h. Onset of LH surge (mean+/-S.E.M.) occurred 3.0+/-0.65 h after the onset of estrus. Mean plasma progesterone stayed low (<0.25 ng/ml) during the entire duration of sampling. Ovulation occurred 30.5+/-0.82 h (range, 28-34 h) after the onset of estrus and 20.25+/-1.03 h after the end of LH surge. The occurrence of the LH peaks within a narrow time frame of 4-8h post estrus onset in yaks could have contributed to the animals ovulating within a narrow time interval.

Animals↗
PubMed2005

Circadian variations in plasma concentrations of melatonin and prolactin during breeding and non-breeding seasons in yak (Poephagus grunniens L.).

Circadian variations of plasma melatonin and prolactin concentrations were determined during breeding as well as non-breeding seasons in yak. Blood samples (5 ml) were collected during different phases of estrous cycle, viz. early (0-6 days), mid (7-12 days) and late luteal (13-19 days) at 2 h interval for 24 h from eight yaks during one breeding month (November); the same yaks were bled at 2 h interval during one non-breeding month (February) for 24 h. Plasma melatonin concentrations rose sharply (P < 0.01) after sunset to record peak concentrations between midnight and 2 a.m. declining sharply thereafter in both breeding as well as non-breeding seasons. Basal melatonin concentrations were recorded between 0600 and 1600 h. Stage of luteal phase did not influence the diurnal hormone change (P < 0.01). In the breeding season, mean plasma prolactin concentrations displayed circadian variations with maximum value at 0400 h (41.22+ /- 1.5 ng/ml) and minimum at 1400 h (12.0 +/- 4.02 ng/ml). In the non-breeding season plasma prolactin concentrations showed circadian variation with maximum value at 0000 h (59.9 +/- 10.5 ng/ml) and minimum at 1200 h (32.13 +/- 3.2 ng/ml). A positive correlation in breeding (r = 0.75) and in non-breeding season (r = 0.65) between circadian changes in mean plasma prolactin and melatonin concentrations were seen. Circadian changes of mean plasma melatonin concentrations during breeding and non-breeding seasons were not different (P > 0.05). However, mean plasma prolactin concentrations were found to be higher (P < 0.01) in the non-breeding season. Three conclusions were drawn from the study: (i) melatonin and prolactin concentrations followed a circadian pattern of secretion (ii) melatonin and prolactin secretion may be closely interrelated and (iii) higher prolactin concentrations during the non-breeding season could be due to nutritional and environmental stress and hence might be contributing to lack of cyclicity.

Animals↗
PubMed2004

Effects of gold on testicular steroidogenic and gametogenic functions in immature male albino rats.

The present study was undertaken to evaluate the effects of gold chloride, a metallic earth salt, on steroidogenic and gametogenic functions of testis in immature rats. Immature rats of Wistar strain, were injected (s.c.) with gold chloride at the dose of 0.3 mg and 0.5 mg/kg body weight/day for 26 days. All the treated animals along with the vehicle-treated controls were sacrificed 24 hours after last injections. Testicular steroidogenic activity was evaluated by measuring the activities of two steroidogenic key enzymes, Delta5-3beta-hydroxysteroid dehydrogenase (Delta5-3beta-HSD) and 17-beta hydroxysteroid dehydrogenase (17-beta HSD). Gametogenic capacity was determined by counting the number of germ cells at stage VII of seminiferous cycle. Plasma levels of testosterone (T) was measured by radioimmunoassay (RIA). Administration of gold chloride at a dose of 0.3 mg/ kg body weight for 26 days led to insignificant changes of testicular Delta5-3beta-HSD,17beta-HSD activities and gametogenesis along with plasma T. In contrast 0.5 mg gold chloride treatment for 26 days caused a significant increase in plasma T (p < 0.001) along with stimulation of testicular Delta5-3beta-HSD activity (p < 0.001) and 17beta-HSD activity (p < 0.001). Gametogenic activity exhibited a significant increase in the number of step 7 spermatids (7Sd) (p < 0.001) at stage VII of seminiferous cycle when compared to control. The results of our experiment suggest that gold chloride treatment might be associated with significant stimulatory effects on testicular activities. Furthermore, since hormonal changes, altered steroidogenic enzymes and gametogenic activities were evident to a specific dose of gold chloride treatment, our data may have some clinical implication on the stimulation of fertility.

17-Hydroxysteroid Dehydrogenases↗
PubMed2004

Synchronization of ovulation in yaks (Poephagus grunniens L.) using PGF(2alpha) and GnRH.

The objective of this study was to test the efficacy of estrus synchronization in yaks using the Ovsynch protocol. To eight non-lactating cycling yaks were administered GnRH analogue followed by PGF(2alpha) analogue treatment 7 days later and further injected with a second injection of same GnRH analogue 2 days after the PGF(2alpha) analogue administration. Ovulation was detected by rectal palpation at 2 h intervals from the initial signs of estrus till ovulation. For LH and progesterone the blood samples were collected at 15 min intervals starting from 1 h prior to the second injection of GnRH analogue until 6 h later and further at 2 h intervals till 2 h after the ovulation. Ovulation was detected in seven out of eight yaks after Ovsynch treatment. The mean time interval from the second GnRH injection to ovulation was 24.8+/-1.95 h with a range of 20-34 h and the mean interval from the LH peak and ovulation was 19.96+/-1.91 h with a range of 14-29 h. The high degree of ovulation synchronization could be attributed to the highly synchronized LH peaks in the treated animals. It was concluded that this estrus synchronization protocol could be applied for fixed time AI in yak.

Animals↗
PubMed2004

[Complications of malignant tumors--pathological fractures].

Advances in the treatment of tumors have improved the life expectancy of cancer patients appreciably. As a consequence the incidence of bone metastases has also increased. Surgical interventions must achieve a maximal palliative effect with minimal morbidity and mortality. Major objectives are reduction of pain while preserving stability and function. Surgical treatment of primary and secondary bone tumors is complicated and thus also burdened with complications. However, interdisciplinary therapy comprising surgical resection and stabilization, radiotherapy and/or chemotherapy improves life expectancy and the quality of life of the cancer patient.

Bone Neoplasms↗
PubMed2003

A comparative study of variation in codon 33 of the rpoS gene in Escherichia coli K12 stocks: implications for the synthesis of sigma(s).

The Escherichia coli rpoS gene encodes an RNA polymerase sigma factor (sigma S or sigma(S)) required for the expression of stationary-phase genes. In the first published rpoS sequence from E. coli K-12 codon 33 is given as CAG. However, several subsequent independent studies found the amber codon TAG at this position ( rpoSAm). Besides this amber codon, other codons such as TAT have also been found at this location in rpoS. Comparative genome analysis now leads us to propose TAG as the parental codon 33 in rpoS in E. coli K-12. Five different stocks of the strain W3110, which differ in the levels of sigma(S) protein they express, were investigated. We sequenced the rpoS gene from these, and found a T at nucleotide position 97 in four out of the five stocks and a G at position 99 in three out of the five. W1485, a parental strain of W3110, and W3350, a derivative of W3110, are also rpoSAm mutants. Such rpoSAm mutants would be expected to show no RpoS activity. The retention of partial or intermediate sigma(S) activity by suppressor-free rpoSAm mutants is therefore puzzling. We propose that a functional, N-terminally truncated, sigma(S) (Delta1-53sigma(S)) can be translated from a Secondary Translation Initiation Region (STIR) located downstream of the amber codon 33. It has recently been reported that a fragment of RpoS (Delta1-53sigma(S)) that lacks the first 53 amino acids is functional when synthesized in vivo. Taken together, our results support the hypothesis that the original codon 33 of the rpoS gene in E. coli K-12 strains is the amber codon TAG.

Bacterial Proteins↗
PubMed2003

Structural requirements for Arabidopsis beta1,2-xylosyltransferase activity and targeting to the Golgi.

Characterization of a beta1,2-xylosyltransferase from Arabidopsis thaliana (AtXylT) was carried out by expression in Sf9 insect cells using a baculovirus vector system. Serial deletions at both the N- and C-terminal ends proved that integrity of a large domain located between amino acid 31 and the C-terminal lumenal region is required for AtXylT activity expression. The influence of N-glycosylation on AtXylT activity has been evaluated using either tunicamycin or mutagenesis of potential N-glycosylation sites. AtXylT is glycosylated on two of its three potential N-glycosylation sites (Asn51, Asn301, Asn478) and the occupancy of at least one of these two sites (Asn51 and Asn301) is necessary for AtXylT stability and activity. Contribution of the N-terminal part of AtXylT in targeting and intracellular distribution of this protein was studied by expression of variably truncated, GFP-tagged AtXylT forms in tobacco cells using confocal and electron microscopy. These studies have shown that the transmembrane domain of AtXylT and its short flanking amino acid sequences are sufficient to specifically localize a reporter protein to the medial Golgi cisternae in tobacco cells. This study is the first detailed characterization of a plant glycosyltransferase at the molecular level.

Amino Acid Sequence↗
PubMed2003

Protection of adrenocortical activity by dietary casein in ether anaesthetized rats.

Adrenal delta5-3beta-hydroxysteroid dehydrogenase (delta5-3beta-HSD) activity and serum corticosterone level were significantly higher in rats fed with 5% casein or 4% albumin diets after 1 hr of ether anaesthetic stress as compared to the controls, 5% casein and 20% casein (equivalent to 4% albumin) respectively. Ether anaesthesia to 20% casein fed rats caused no change in adrenal delta5-3beta-HSD activity and serum corticosterone level when compared with controls fed 20% casein diet. The results suggest that high milk protein diet may prevent acute stress effects by protecting adrenocortical activity. The present investigation opens up a new area of management of stress.

3-Hydroxysteroid Dehydrogenases↗
PubMed2001

Interleukin-8 administration enhances venous thrombosis resolution in a rat model.

BACKGROUND: Therapy for deep vein thrombosis (DVT) resolution in those patients in whom a complication or contraindication to anticoagulation occurs is limited. As prior work suggests that thrombus maturation involves early influx of neutrophils (PMN) and neovascularization, we hypothesized that administering the proinflammatory/proangiogenic chemokine interleukin (IL)-8 might accelerate thrombus resolution. MATERIALS AND METHODS: An established rodent model of DVT (inferior vena cava [IVC] ligation) was used whereby daily intravenous recombinant human IL-8 (1 microg) or vehicle control was administered, with sacrifice at 4 and 8 days. Prior to sacrifice and at harvest, duplex ultrasound of the DVT and femoral venous pressure measurements were performed. Thrombi were analyzed by immunohistochemical techniques for PMN, monocytes, and neovascularization; for chemokines, by enzyme-linked immunoassay; and fibrosis, by hydroxyproline assay and trichrome staining. RESULTS: IL-8 accelerated thrombus dissolution 4 days after IVC ligation, with 6-fold increased thrombus blood flow by duplex ultrasound and a 23% increased absolute femoral venous pressure compared with controls (both P < 0.05). These findings may be partially explained by the fact that animals receiving IL-8, as compared with controls, had 2.5-fold greater thrombus neovascularization (with a trend continuing to 8 days) and increased PMN at 4 days. Thrombus vascular endothelial growth factor was significantly reduced at 8 days postligation, while monocyte chemotactic protein-1 and macrophage inflammatory protein-1alpha were not altered by IL-8 administration. At 8 days post-IVC-ligation, fibrosis was 12-fold greater with IL-8 treatment compared with controls. CONCLUSIONS: A proinflammatory/proangiogenic thrombus milieu, as conferred by IL-8, enhances thrombus resolution and underscores the important relationship between neovascularity and inflammation.

Animals↗
PubMed2001

A direct injection capillary electrophoretic technique for miniaturized high-throughput metabolic screening of the CYP 3A4 enzyme using quinidine as a probe.

A capillary electrophoresis (CE) method has been developed for the determination of quinidine sulfate (QS) and (3S)-3-hydroxyquinidine (3-OHQ) by direct injection of microsomal incubation mixtures. 3-OHQ is the CYP 3A4 metabolite of QS and hence useful for metabolism screening studies. The method was validated analytically and tested for its effectiveness as a metabolic inhibition model. A linear calibration was found to provide the best fit for the standard curve with an r of 0.9966 and all residuals less than 12%. The percent relative standard deviations (RSDs) of the two controls, 2 and 8 microg/ml were 5.27 and 2.90% and the percent difference from normal (% DFN) were -12.58 and -0.31% respectively. The limit of quantitation (LOQ) in the incubation matrix was 0.5 microg/ml. 3-OHQ formation complied with Michaelis-Menten kinetics and the mean values+/-S.D. of Km and Vmax were 36.98+/-4.62 microg/ml and 321.39+/-3.88 ng/mg/h respectively. Preliminary inhibition studies suggest that the method has adequate sensitivity to screen for high and medium inhibitors of the CYP 3A4 isozyme. The lack of sample preparation coupled with the small sample size capability of CE would enable the direct injection technique to aid in miniaturized high-throughput screening.

Animals↗