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S Das

Publications and source records attributed to S Das.

At least 361 records · Page 20Linked to original sources
PubMed1995

Borrelia burgdorferi genes selectively expressed in the infected host.

An immunological screening strategy was used to select microbial genes expressed only in the host. Differential screening of a Borrelia burgdorferi (the Lyme disease agent) expression library identified a gene (p21) encoding a 20.7-kDa antigen that reacted with antibodies in serum from actively infected mice but not serum from mice immunized with heat-killed B. burgdorferi. Selective expression of p21 in the infected host was confirmed by Northern blot analysis and RNA PCR. Further differential screening of the expression library identified at least five additional B. burgdorferi genes are selectively expressed in vivo. This screening method can be used to identify genes induced in vivo in a wide variety of pathogenic microorganisms for which a gene transfer system is not currently available.

Amino Acid Sequence↗
PubMed1995

Mitochondrial VDAC can be phosphorylated by cyclic AMP-dependent protein kinase.

The voltage dependent anion channel (VDAC) of the outer membrane of mitochondria is thought to play a role in transport of metabolites including ATP across mitochondrial membrane and modulate mitochondrial functions such as respiration. However, regulation of this anion channel is only poorly understood. In this paper we demonstrate that VDAC purified from rat liver mitochondria can be phosphorylated by the catalytic subunit of cAMP dependent protein kinase (PKA). PKA phosphorylates VDAC linearly up to fifteenfold in sixty minutes. The level of VDAC phosphorylation increases to twofold and sevenfold of control value after ten and thirty minutes of reaction, respectively. Data presented here suggest the possibility that voltage dependent anion channel of the outer membrane of mitochondria may be a target of PKA in vivo.

Animals↗
PubMed1995

DNA fingerprinting of Brassica juncea cultivars using microsatellite probes.

The genetic variability in the Brassica juncea cultivars was detected by employing in-gel hybridization of restricted DNA to simple repetitive sequences such as (GATA)4, (GACA)4 and (CAC)5. The most informative probe/enzyme combination was (GATA)4/EcoRI, yielding highly polymorphic fingerprint patterns for the B. juncea cultivars. This technique was found to be dependable for establishing the variety specific patterns for most of the cultivars studied, a prerequisite for germplasm preservation. The results of the present study were compared with those reported in our earlier study in which random amplification of polymorphic DNA (RAPD) was used for assessing the genetic variability in the B. juncea cultivars.

Base Sequence↗
PubMed1995

Open-loop simulations of the primate saccadic system using burst cell discharge from the superior colliculus.

Saccade-related burst neurons (SRBNs) in the monkey superior colliculus (SC) have been hypothesized to provide the brainstem saccadic burst generator with the dynamic error signal and the movement initiating trigger signal. To test this claim, we performed two sets of open-loop simulations on a burst generator model with the local feedback disconnected using experimentally obtained SRBN activity as both the driving and trigger signal inputs to the model. First, using neural data obtained from cells located near the middle of the rostral to caudal extent of the SC, the internal parameters of the model were optimized by means of a stochastic hill-climbing algorithm to produce an intermediate-sized saccade. The parameter values obtained from the optimization were then fixed and additional simulations were done using the experimental data from rostral collicular neurons (small saccades) and from more caudal neurons (large saccades); the model generated realistic saccades, matching both position and velocity profiles of real saccades to the centers of the movement fields of all these cells. Second, the model was driven by SRBN activity affiliated with interrupted saccades, the resumed eye movements observed following electrical stimulation of the omnipause region. Once again, the model produced eye movements that closely resembled the interrupted saccades produced by such simulations, but minor readjustment of parameters reflecting the weight of the projection of the trigger signal was required. Our study demonstrates that a model of the burst generator produces reasonably realistic saccades when driven with actual samples of SRBN discharges.

Algorithms↗
PubMed1995

Transovarial transmission of Nosema locustae (Microsporida: Nosematidae) in the migratory locust Locusta migratoria migratorioides.

Nosema locustae, a microsporidian parasite of locusts and grasshoppers, was transovarially transmitted to the progeny of infected Locusta migratoria reared for up to F14 generations. The mortality of infected progeny in each generation was higher than that of uninfected controls and ranged from 67.6% to 95.5%. Infected female survivors transmitted the microsporidium to the progeny via eggs. The developing eggs harboured vegetative stages of N. locustae, and development of the microsporidium occurred during embryonation. Spores accumulated in the yolk and, after blastokinesis, both the yolk and the spores were enclosed in the midgut of the embryo. Germinated spores infected the functional midgut epithelium and invaded internal tissues. The mortality of newly hatched instars was high when embryonic tissue had been infected during development.

Animals↗
PubMed1995

Acute and subchronic effects of clozapine on licking in rats: tolerance to disruptive effects on number of licks, but no tolerance to rhythm slowing.

In order to assess the effects of the atypical neuroleptic clozapine on orolingual competence in rats, tongue function was measured by quantitating the rhythm of tongue movements after acute (1.0, 3.0, 6.0 mg/kg) or subchronic intraperitoneal treatment (1.5, 3.0, 4.5 mg/kg, each dose for at least 7 days) with the drug. Thirsty rats were trained to lick water from a force-sensing disk by thrusting the tongue through a 12-mm-diameter hole to strike the horizontal disk located 5 mm below the hole. Number of licks in 2 min and rhythm of tongue movements (as determined by Fourier analysis of the force-time signal) were each dose dependently reduced in the acute dose-effect phase of the study. In the subchronic study number of licks exhibited tolerance, but the slowing of lick rhythm did not show tolerance. An acute dose range of the serotonin antagonist ritanserin (0.5, 1.0, 2.0, 4.0 mg/kg) was also studied in the same rats. Ritanserin had no effect on any of the measures of orolingual function. The clozapine result was replicated in a second study using younger, drug naive rats. The results for clozapine were contrasted with previous reports indicating that haloperidol has little effect on lick rhythm. Additional discussion evaluated the possible contribution of neurotransmitter receptors on motor neurons of the hypoglossal nucleus to the observed rhythm slowing induced by clozapine.

Animals↗
PubMed1995

Nitric oxide: its identity and role in blood pressure control.

In response to biochemical factors like catecholamines, bradykinins, histamine and physical factors like shear stress, endothelial cells release a non prostanoid factor, called endothelium derived relaxing factor (EDRF), which relaxes vascular smooth muscle. Since this discovery in 1980, many additional agents have been shown to stimulate release of EDRF from endothelium. Biological and chemical evidence has supported the proposal that EDRF is actually nitric oxide (NO). Research on the synthesis, inhibition and physiological roles of nitric oxide (NO) has led to studies of its involvement in blood pressure homeostasis and immune functions.

Animals↗
PubMed1995

A survey of health professionals' views on possible changes in the provision and organisation of antenatal care.

OBJECTIVE: To ascertain the views of midwives, obstetricians and general practitioners (GPs) on possible changes in the provision of antenatal care, and to describe any differences in attitude between the three professional groups. DESIGN: survey using postal questionnaire. SETTING: Three hospitals in south-east London. PARTICIPANTS: The questionnaire was sent to 251 midwives, 50 obstetricians, and 438 GPs. The overall response rate was 70%. MEASUREMENTS: A questionnaire asking whether the health professionals would like to see, were undecided, or would not like to see, 12 possible changes in the provision of antenatal care. FINDINGS: The changes that most health professionals wanted to see were individualised visit schedules and an increase in continuity of care-giver. There were significant differences between the three professional groups for 11 of the 12 possible changes, with midwives being the group most keen, and GPs tending to be the least keen, to see change. KEY CONCLUSIONS: It is important to recognise and address the different views of midwives, obstetricians and general practitioners at this time when major changes in the organisation of antenatal care are being planned or implemented. IMPLICATIONS FOR PRACTICE: Differences in attitudes between health professionals need to be addressed when planning changes in the provision of antenatal care.

Attitude of Health Personnel↗
PubMed1995

The pupillary light response: assessment of function mediated by intracranial retinal transplants.

We have adapted a pupillometry measurement system to test the functional efficacy of retinae previously transplanted over the midbrain of neonatal rats in mediating a pupillary light reflex in the host eye. This has permitted us to examine factors influencing various parameters of the response, and to study transplant-mediated responses in comparison with responses mediated by way of the normal consensual pathway. Despite the unusual location of these transplanted retinae and the absence of supportive tissues normally associated with retinae in situ, it is clear that pupilloconstriction in the host eye can be elicited by transplant illumination. Under the optimal conditions here defined, response parameters for individual animals were stable with repeated testing over extended periods. When considered as individual cases, response amplitude, constriction rate and response latency were intensity dependent, although responses elicited by transplant illumination were less sensitive than normal, typically by 2-3 log units. Large-amplitude transplant-mediated pupillary responses could, however, be elicited repeatedly throughout long trains of stimuli, unlike normal responses, which rapidly failed to recover to baseline under similar test conditions. Finally, even though some cellular elements of the visual cycle are absent in transplanted retinae, pupilloconstriction in the host eye could be elicited repeatedly by transplant illumination as long as two years after transplantation took place. These observations indicate the applicability of this preparation as an assay for the effects of experimental manipulations on information processing and response plasticity in the visual system, and as a tool for examining, in general, the necessary conditions for optimal function of grafts that work by synthesizing and relaying neural signals.

Anesthesia↗
PubMed1995

Expression of the Alzheimer amyloid-promoting factor antichymotrypsin is induced in human astrocytes by IL-1.

The amyloid deposits of Alzheimer's disease contain, in addition to the beta protein (A beta), lesser amounts of other proteins including the protease inhibitor alpha 1-antichymotrypsin (ACT). We have recently shown that ACT acts as a pathological chaperone, binding to the beta protein and strongly promoting its polymerization into amyloid filaments in vitro. The data of this paper show that ACT synthesis is induced in cultured human astrocytes by IL-1, a lymphokine whose expression is strongly up-regulated in microglial cells in affected areas of Alzheimer's disease brain. Furthermore, unfractionated glial cultures containing both astrocytes and microglia from human cortex (which develops amyloid in Alzheimer's disease) spontaneously express IL-1 and ACT as they reach confluence. In contrast, confluent mixed glial cultures similarly prepared from human cerebellum or brain stem, or from rat brain-tissues not prone to amyloid formation-do not express ACT unless supplemented with exogenous IL-1. The same regional difference in IL-1 expression by microglia is seen in vivo in Alzheimer's disease. These results indicate that the IL-1-induced expression of ACT may help direct the region-specific production of mature amyloid filaments in the Alzheimer brain.

Alzheimer Disease↗
PubMed1995

IS6110 restriction fragment length polymorphism typing of clinical isolates of Mycobacterium tuberculosis from patients with pulmonary tuberculosis in Madras, south India.

SETTING: Madras, India. OBJECTIVE: To explore the utility of a standardized IS6110/PvuII deoxyribonucleic acid (DNA) fingerprinting restriction fragment length polymorphism (RFLP) typing method for distinguishing between isolates of Mycobacterium tuberculosis, and to assess the potential for distinguishing between relapse versus reinfection rates. DESIGN: To assess RFLP heterogeneity in the population, initial isolates, obtained from the sputum of tuberculous 98 patients in diagnosis and follow-up during short-course chemotherapy, were stored and compared. To assess the frequency of disparity between the RFLP type of the initial isolate and one obtained after successful completion of chemotherapy, either during relapse or as an isolated positive culture, 124 isolates comprising 62 such pairs were coded and compared both blind and after decoding. RESULTS: Although a wide variety of DNA band patterns (fingerprints) was present, the isolates from 39 (40%) of the patients showed a single copy of IS6110. Only 15 pairs of coded initial and follow-up isolates could be identified as having the same band pattern when isolates with zero or single bands were excluded. Nevertheless, after decoding, in a retrospective analysis that included all isolates, those isolates that bacteriologically defined a patient's relapse more often showed RFLP type identity with the initial isolate (19 of 30 comparisons) than did isolates that were obtained as isolated positive cultures (3 of 32 comparisons) (X2 P < 0.001). Tests of sensitivity to chemotherapeutic drugs, catalase activity and resistance to thiophene-2-carboxylic acid hydrazide were of minimal value in discriminating between isolates. CONCLUSIONS: Despite the high frequency of single- and zero-band isolates in this population, the discriminatory power of RFLP typing with IS6110 is sufficiently high to be useful for clinical and epidemiological studies.

Adolescent↗
PubMed1995

Initial experience with retroperitoneoscopic nephroureterectomy: use of a double-balloon technique.

OBJECTIVES: To report the initial experience with retroperitoneoscopic nephroureterectomy for symptomatic, end-stage vesicoureteral reflux. METHODS: Two patients underwent a nephroureterectomy by a four-port retroperitoneal laparoscopic approach. In 1 patient, a double-balloon technique was used to dissect the pelvic extraperitoneal space and gain access to the juxtavesical ureter. In the second patient, the distal ureter was mobilized with routine laparoscopic dissection techniques. RESULTS: Operative time was 6 and 5.5 hours, respectively, and mean hospital stay was 4 days. Mean patient follow-up is 17.5 months. CONCLUSIONS: The technique of retroperitoneoscopic nephroureterectomy is in evolution; until now, a major concern has been the inadequate access to the distal ureter through a completely retroperitoneoscopic approach. Described herein is a double-balloon technique that significantly facilitates dissection of the juxtavesical ureter during a retroperitoneal laparoscopic nephroureterectomy.

Adult↗
PubMed1995

Cortical regulation of subcortical dopamine release: mediation via the ventral tegmental area.

In vivo microdialysis was used to determine the extent to which ionotropic glutamate receptors in the ventral tegmental area (VTA) regulate dopamine release in the nucleus accumbens. Coapplication of 2-amino-5-phosphonopentanoic acid (AP5; 200 microM) and 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 50 microM) to the VTA via reverse dialysis decreased extracellular concentrations of dopamine in the nucleus accumbens by approximately 30%. In accordance with previous results, electrical stimulation of the prefrontal cortex increased dopamine release by 60%. Application of AP5 and CNQX to the VTA during cortical stimulation blocked the effect of stimulation on dopamine release. These results indicate that ionotropic glutamate receptors in the VTA are critically involved in basal and evoked dopamine release in the nucleus accumbens and suggest that a glutamatergic projection from the prefrontal cortex regulates the activity of dopaminergic neurons in the VTA.

2-Amino-5-phosphonovalerate↗
PubMed1995

Cardiac involvement and scorpion envenomation in children.

Cardiac complications of 32 children with scorpion envenomation, during a 1-year period from August 1990 to August 1991 were studied. Sixteen children (50 per cent) were diagnosed as having myocarditis; of these in four children the presentation was subclinical. ECG changes were seen in 63 per cent of children envenomed and was a sensitive indicator of myocarditis. Sixty-nine per cent of children with myocarditis had left ventricular dysfunction as shown by echocardiography. Though statistically not significant, there was a correlation between prolonged QTc and LV dysfunction, which needs to be studied further. In those children who came for follow-up, the left ventricular function reversed to normal.

Animals↗