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Biomedical subjects

J Singh

Publications and source records attributed to J Singh.

At least 289 records · Page 16Linked to original sources
PubMed1997

Effects of silymarin on UDP-glucuronic acid and glucuronidation activity in the rat isolated hepatocytes and liver in relation to D-galactosamine toxicity.

Influence of silymarin on UDP-glucuronic acid (UDPGA) and glucuronidation activity of freshly isolated rat hepatocytes in suspension and in rat liver in vivo was examined. Viability of the hepatocytes (> 85%) was not altered in Hank's balanced salt solution at least for 4 hr at 37 degrees C under oxygen. Silymarin at 0.4 mM depleted UDPGA by more than 60% at the end of 4 hr of incubation, the fall in nucleotide pool was rapid and concentration (0.1-0.4 mM)-dependent. The rate of glucuronidation of 3-OH- benzo(a)pyrene (3-OH-BP) determined simultaneously was also reduced significantly; silybin being 3-times more effective than silymarin. Combination of flavonoids with D-galactosamine (GalN) further attenuated the glucuronidation functions of the cells. The flavonoids also offered strong inhibition of UDP-glucose dehydrogenase (UDP-GDH) activity in the liver cytosolic fraction while the activity in hepatocytes was not affected even after 4 hr of incubation. Interestingly, the GalN- induced strong inhibition of UDP-GDH in isolated hepatocytes was completely abolished by flavonoids. Decrease in UDPGA appeared neither due to the activation of UDPGA-pyrophosphatase activity nor to the inhibition of UDP-GDH activity in hepatocytes. Further, the flavonoids also inhibited hepatic UDP-glucuronyltransferase activity towards 3-OH-BP (UGT) both in vitro and in intact cells. On the contrary, silymarin administered (70 mg/kg body wt; i.p.) to rats for 3 hr increased the hepatic UDPGA by 2-fold while GalN (400 mg/kg body wt) reduced the nucleotide content to 50% of control. Coadministration of silymarin and GalN restored the UDPGA content significantly while the activities of UDP-GDH and UGT were comparable to the untreated control. The results indicated that silymarin elicits differential effects on the rate of glucuronidation and contents of UDPGA in the isolated rat hepatocytes and in liver. The flavonoid counteracted D-GalN-induced lowering of UDPGA presumably by relieving UDP-GDH of in vivo inhibition affected by GalN-metabolite.

Animals↗
PubMed1997

A study on interrelationship of 60 HIV positive cases with coexistent oral candidosis and tuberculosis.

Sixty HIV seropositive cases studied of inter-relationship of coexistent infections with tuberculosis and oral candidosis. Presence of oral candidosis either symptomatic/asymptomatic as revealed on microbiological studies have been recorded and the significance discussed. Presence of oral candidosis apparent of nonapparent with heavy growth, yield on culture in HIV seropositive cases could be considered a pointer of conversion of HIV infection to a disease. This observation needs further evaluation. Relevant literature reviewed briefly.

AIDS-Related Opportunistic Infections↗
PubMed1997

Multiple myeloma complicating HIV-infection. A case report.

A case of multiple myeloma associated with HIV disease and hepatosplenomegaly presented to us as pyrexia of unknown origin, is reported. Because of paucity of such cases in the literature, the case is dealt in detail and the literature reviewed briefly.

Adult↗
PubMed1997

Differential biochemical response of freshly isolated rat hepatocytes to paracetamol, carbon tetrachloride and D-galactosamine toxicity.

Differential response of freshly isolated rat hepatocytes to paracetamol (acetaminophen, AAP), carbon tetrachloride (CCl4) and D-galactosamine (GalN) was examined. The viability of the cells in suspension culture was not altered for 4 hr when incubated in Hank's balanced salt solution (HBSS) supplemented with 4.2 mM NaHCO3, 10 mM HEPES buffer and 0.5% bovine serum albumin. AAP induced time and dose dependent depletion of GSH as an early manifestation of AAP toxicity. Hepatocytes exposed to AAP exhibited lower lactate dehydrogenase (LDH) activity released into the medium than in controls. This was due to the interaction of a reactive metabolite of AAP, i. e. N-acetyl p-benzoquinoneimine (NAPQI) with cell proteins. Hepatocytes isolated from rats pretreated with 3-methylcholanthrene expressed higher sensitivity to AAP toxicity at least by a factor of 5. Furthermore, AAP-induced toxicity was not found to be related to any lipoperoxidative stress. CCl4 on the other hand elicited a highly lipoperoxidative response in hepatocytes and consequent leakage of cellular enzymes with lengths of incubation. Again the sensitivity of the response to CCl4 was enhanced remarkably in hepatocytes isolated from phenobarbital- pretreated rats; LDH leakage increased by 3-fold and thio-barbituric acid reactive substances by 25-fold. Unlike the two toxicants, galactosamine depleted UDP-glucuronic acid in a concentration and time-related manners. The differential biochemical response of hepatocytes to three hepatotoxicants investigated may prove useful as rapid in vitro screen for selection of compounds of hepatoprotective potentials.

Acetaminophen↗
PubMed1997

Silymarin mediated differential modulation of toxicity induced by carbon tetrachloride, paracetamol and D-galactosamine in freshly isolated rat hepatocytes.

Influence of silymarin on the modulation of hepatotoxicity induced by carbon tetrachloride (CCl4), paracetamol (AAP) and D-galactosamine (GalN) was examined in freshly isolated rat hepatocytes in suspension culture. While the three hepatotoxicants produced differential biochemical response, the flavone was able to restore biochemical alterations only in hepatocytes exposed to CCl4 and AAP induced toxicity. Silymarin at 0.4 mM was able to counteract lipid peroxidation and enzyme leakage induced by 3 mM CCl4 The flavone also offered protection by more than 60% in hepatocytes isolated from PB pre-treated rats where CCl4 at 2 mM produced enhanced toxicity over hepatocytes isolated from untreated control rats. Similarly, the flavone protected AAP-induced GSH depletion by more than 75% in hepatocytes isolated from untreated and 3-methylcholanthrene treated rats. However, instead of protecting GalN-induced depletion of UDP-glucuronic acid in hepatocytes, the flavone itself reduced the nucleotide content very rapidly compared to GalN, the later exerted time dependent effect. Silymarin at 0.4 mM reduced UDPGA by more than 60%. The results suggested that freshly isolated hepatocytes in suspension culture offer a simple and convenient method for evaluation of pharmaceutical agents of antihepatotxic potentials against various hepatotoxicants.

Acetaminophen↗
PubMed1997

Dietary and physiological studies to investigate the relationship between calcium and magnesium signalling in the mammalian myocardium.

This study employs both dietary and physiological studies to investigate the relationship between calcium (Ca2+) and magnesium (Mg2+) signalling in the mammalian myocardium. Rats maintained on a low Mg2+ diet (LMD; 39 mg Kg-1 Mg2+ in food) consumed less food and grew more slowly than control rats fed on a control Mg2+ diet (CMD; 500 mg Kg-1 Mg2+ in food). The Mg2+ contents of the heart and plasma were 85 +/- 3% and 34 +/- 6.5%, respectively relative to the control group. In contrast, Ca2+ contents in the heart and plasma were 177 +/- 5% and 95 +/- 3%. The levels of potassium (K+) was raised in the plasma (129 +/- 16%) and slightly decreased in the heart (88 +/- 6%) compared to CMD. Similarly, sodium (Na+) contents were slightly higher in the heart and lowered in the plasma of low Mg2+ diet rats compared to control Mg2+ diet rat. Perfusion of the isolated Langendorff's rat heart with a physiological salt solution containing low concentrations (0-0.6 mM) of extracellular magnesium [Mg2+]o resulted in a small transient increase in the amplitude of contraction compared to control [Mg2+]o (1.2 mM). In contrast, elevated [Mg2+]o (2-7.2 mM) caused a marked and progressive decrease in contractile force compared to control. In isolated ventricular myocytes the L-type Ca2+ current (ICa,L) was significantly (p < 0.001) attenuated in cells dialysed with 7.1 mM Mg2+ compared to cells dialysed with 2.9 microM Mg2+. The results indicate that hypomagnesemia is associated with decreased levels of Mg2+ and elevated levels of Ca2+ in the heart and moreover, internal Mg2+ is able to modulate the Ca2+ current through the L-type Ca2+ channel which in turn may be involved with the regulation of contractile force in the heart.

Animals↗
PubMed1997

Characterization of gpt deletion mutations in transgenic Chinese hamster cell lines.

The transgenic cell lines G12 and G10, each with a bacterial gpt gene stably integrated at a single but different position in the Chinese hamster genome, were evaluated for deletion of the gpt transgene following exposures to several clastogens. More than 150 independently cloned G12 and G10 6-thioguanine-resistant mutants have been characterized by polymerase chain reaction (PCR) amplification and Southern blots in this study. Despite differences in the integration sites for the gpt gene in the G12 and G10 cells, PCR amplification of the gpt gene from both cell lines can be performed using the same single set of primers. By PCR deletion screening, about 20% of recovered spontaneous 6-thioguanine resistant (6TG) gpt G12 mutants had deleted the transgene, whereas the deletion mutant frequency was increased to about 50% of the X-ray- and bleomycin-induced G12 mutants. In contrast, both spontaneous and induced deletion frequencies are considerably higher for the G10 cell line. Among spontaneous G10 mutants, up to 50% have deleted the gpt transgene, whereas almost all of the X-ray- and bleomycin-induced G10 mutants have lost the integrated gene sequence. These results are discussed in the context of the transgene integration sites and the influences of the surrounding genome that may render certain genetic regions prone to deletion.

Alanine Transaminase↗
PubMed1997

Epidemiology of endemic viral hepatitis in an urban area of India: a retrospective community study in Alwar.

In a community study during a reference period of 1 year, 192 cases of jaundice were detected in an urban population of 69,440 in Alwar, Rajasthan. Detected by paramedics and confirmed by physicians, these cases gave an annual incidence of 2.76 (95% CI: 2.37-3.15) per 1000 population. At least one of these patients died, giving a case fatality ratio of 0.6%. The jaundice cases occurred in all areas investigated, and affected all socioeconomic strata. About 94% of the affected families had only single cases. Although cases occurred throughout the year, more than 59% occurred during June-September, which are the summer and monsoon months. The incidence was highest (5.23 per 1000) among under-5-year-olds and declined progressively and significantly thereafter. Males had a higher incidence than females at all ages; the differences were not significant. Blood samples from 56 cases who had jaundice in the last 3 months of the reference period were tested for markers of viral hepatitis. Of these, 18 (32.1%), 1 (1.8%), 0, 2 (3.6%), and 4 (7.1%) were found to have hepatitis A, B, C, D and E, respectively. The etiology of the remaining 31 cases (55%) could not be established; previously, they would have been included in the NANB (non-A, non-B) category, inflating its proportion. Hepatitis A (HA) was the predominant type; being comparatively mild, it is perhaps underrepresented in hospital-based data. Many HA cases were in adults, which may be the beginning of an age shift of HA to the right owing to improvements in living standards of the study population. Five cases were carriers of hepatitis B virus (HBV), indicating the importance of HBV infection in India as well. Finally, the study found the annual incidence of laboratory-supported cases of viral hepatitis to be 1.24 (95% CI: 0.98-1.5) per 1000 population, which suggests that it is a major public health problem in India.

Adolescent↗
PubMed1997

Assessment of iodine deficiency in selected blocks of east and west Champaran districts of Bihar.

OBJECTIVE: A survey conducted in 1964 reported a goitre prevalence of 40.3% in East and West Champaran districts of Bihar. No recent survey has been documented on the prevalence of iodine deficiency in these districts. The present study was therefore undertaken (i) to assess the prevalence of IDD in these districts, and (ii) to estimate the iodine content of salt consumed by population. METHODOLOGY: In each district, one block was selected. In each block more than 630 children in the age group of 6-12 years were included in the study and were clinically examined. Urine samples were collected from 261 children and were analyzed using standard laboratory procedures. A total of 456 salt samples were collected from children and 35 from traders from the two districts and analyzed using the standard iodometric titration method. RESULTS: The total goiter prevalence was 11.6%. The percentage of children with < 2, 2.0-4.9, 5.0-9.9 and > or = 10 mcg/dl of urinary iodine excretion level were 12.3, 13.4, 23.4 and 51.0, respectively. The median urinary iodine excretion of the children was 10.0 mcg/dl. None of the families were consuming salt with a nil iodine content and about 29.3%, were consuming salt with less than 15 ppm of iodine. Of the 35 salt samples collected from traders, all had iodine and about 17% had less than 15 ppm of iodine. CONCLUSION: The study stresses the need for strengthening the existing system of monitoring of quality of salt being provided in the East and West Champaran districts by Government of Bihar.

Child↗
PubMed1996

Replication across O6-methylguanine by human DNA polymerase beta in vitro. Insights into the futile cytotoxic repair and mutagenesis of O6-methylguanine.

Replication in vivo across unrepaired O6-methylguanine (m6dG) lesions by mammalian DNA polymerase beta (pol beta) during short patch repair may contribute to the cytotoxicity and mutagenesis of m6dG. We have employed in vitro steady state kinetic analysis to investigate the replication of oligonucleotide templates containing site-specific m6dG by human pol beta. Our results show that m6dG is a strong but not absolute block to replication by pol beta. pol beta exhibits mixed kinetic discrimination during overall replication across dG and m6dG. pol beta preferentially inserts dTMP rather than dCMP opposite m6dG. However, pol beta extends from the dC-m6dG base pair more efficiently than from the dT-m6dG base pair. This is in strong contrast to other polymerases such as the exonuclease-deficient Klenow fragment of Escherichia coli DNA polymerase I (exo-KF) that preferentially extends dT-m6dG by a factor of 10 over dC-m6dG. When both insertion and extension are considered, pol beta has a 15-fold overall preference for incorporation of the mutagenic substrate dTTP rather than the nonmutagenic substrate dCTP during replication across m6dG. This suggests that pol beta, in concert with the T:G-specific thymine DNA glycosylase, may be intricately involved in the futile cytotoxic repair induced by m6dG. Our results also suggest that replication across m6dG by pol beta may contribute to m6dG-induced G --> A transition mutations.

Base Sequence↗
PubMed1996

Secretion and serotonin release in the isolated rat lacrimal gland: the effects of substance P and calcitonin gene-related peptide.

A close anatomical relationship between nerves containing substance P and calcitonin gene-related peptide (CGRP) and mast cells containing serotonin has been demonstrated in the rat lacrimal gland. This study investigates the potential for peptidergic regulation of lacrimal mast cells by examining the actions of substance P, CGRP and serotonin on protein and peroxidase secretion from isolated lacrimal segments and on substance P and CGRP to release serotonin from the lacrimal mast cells. Substance P, CGRP and serotonin evoked marked increases in total protein and peroxidase from the lacrimal. Sodium cromoglycate, a mast cell stabilizer, significantly reduced or blocked the secretory responses elicited by these agonists. Chromatographic analysis using electrochemical detection revealed that substance P, but not CGRP, augmented the release of serotonin from the gland. The substance P evoked peroxidase secretion and serotonin release was blocked by CGRP and by sodium cromoglycate. These results support a role for mast cells in the regulation of lacrimal secretion and suggest a novel regulatory interaction between substance P and CGRP in the control of lacrimal function through a neuro-immune interaction.

Animals↗
PubMed1996

Short stature and growth hormone therapy. A national study of physician recommendation patterns.

OBJECTIVE: To determine current expert opinion and recommendations regarding the controversial issue of the use of growth hormone (GH) to treat short children who do not have classical GH deficiency (non-GHD children). STUDY DESIGN: Analysis of a national survey mailed to 534 US physician experts on the management of short stature (pediatric endocrinologists) with a response rate of 81.3%. MAIN OUTCOME MEASURE: The experts' GH treatment recommendations. RESULTS: The physicians reported that approximately 58% of their current patients undergoing GH therapy have classical GH deficiency, while 42% have other conditions. The proportion of physicians who recommended GH treatment of short non-GHD children ranged from 1% to 74% over all case scenarios presented. The likelihood of GH being recommended depended on the physiological growth characteristics of the child (ie, the child's height, growth rate, and predicted adult height), contingency factors (ie, strong family wishes or a reduction in GH cost), and physician beliefs (ie, the impact of short stature on well-being, the effectiveness of GH therapy). Each of these factors exerted highly significant, independent, and additive effects on decisions to recommend GH. CONCLUSION: Our results indicate that many pediatric endocrinologists consider GH treatment appropriate for selected short non-GHD children, going beyond current Food and Drug Administration-approved indications for GH. Decisions to recommend GH for a non-GHD child rest on a combination of medical, social, and perceptual factors; variations in treatment patterns stem from variations in these influences. Future GH use will likely be determined not only by the results of controlled trials, but also by family preferences, producer pricing, and physician perceptions of the value of height and GH therapy.

Attitude↗
PubMed1996

X-SITE: use of empirically derived atomic packing preferences to identify favourable interaction regions in the binding sites of proteins.

A new empirically based method for predicting favourable interaction regions within the binding sites of proteins is presented. The method uses spatial distributions of atomic contact preferences derived from a non-homologous dataset of 83 high-resolution protein structures. The contact preferences are obtained for 26 different atom types relative to 163 different types of three-atom fragments. Each fragment consists of a triplet of bonded atoms, 1-2-3, which defines a reference frame for the three-dimensional distributions. In this way, directional, as well as distance, information is retained. Once derived, the distribution can be applied in a predictive manner. Given a protein's binding site, each distribution is transformed on to the three-atom fragments of the constituent residues and, when combined, can identify the favourable interaction regions for each different atom type. These predicted regions can then form the basis either for the modification of known inhibitors or for the search and design of new ones. Five known protein-ligand complexes are used to demonstrate the validity and usefulness of the approach. The results show that the method provides a powerful tool both in understanding how a given ligand exploits the interactions available to it in an active site and in helping to design improved, or novel, protein ligands.

Algorithms↗
PubMed1996

Thyroid-stimulating hormone rapidly stimulates inositol polyphosphate formation in FRTL-5 thyrocytes without activating phosphoinositidase C.

The thyroid-stimulating hormone (TSH) receptor is widely regarded as one of a limited number of G-protein-coupled receptors that activate both adenylate cyclase and phosphoinositidase C (PIC) via G-proteins, but the existing experimental evidence for TSH-stimulated PtdIns(4,5)P2 hydrolysis remains inconclusive. We have compared the effects of TSH and of ATP (acting via P2-purinergic receptors) on the inositol lipids and polyphosphates of [2-3H]inositol-labelled FRTL-5 rat thyroid cells. ATP initiated a rapid decrease in 3H-labelled PtdIns4P and PtdIns(4,5)P2, whereas TSH did not. Stimulation with ATP and, less consistently, with noradrenaline (acting via alpha-adrenergic receptors) provoked rapid formation of Ins(1,4,5)P3, Ins(1,3,4,5)P4, Ins(1,3,4)P3 and Ins(1,4)P2, confirming activation of PtdIns(4,5)P2 hydrolysis. No concentration of TSH provoked detectable accumulation of Ins(1,4,5)P3 or Ins(1,4)P2 during the first few minutes of stimulation. However, an InsP3 [with the chromatographic properties of Ins(1,3,4)P3] and two InsP4 isomers [neither of which was Ins(1,3,4,5)P4] accumulated quickly in TSH-stimulated cells. ATP immediately provoked a large increase in intracellular calcium concentration ([Ca2+]i) in Indo 1-AM-loaded cells. TSH provoked a small and delayed [Ca2+]i elevation in only some experiments. We therefore confirm that activation of P2-purinergic receptors and alpha 1-adrenergic receptors provokes PIC activation, an accumulation of Ins(1,4,5)P3 and its metabolites and rapid [Ca2+]i mobilization in FRTL-5 cells. By contrast, TSH provokes no rapid PIC-catalysed PtdIns(4,5)P2 hydrolysis or immediate [Ca2+]i mobilization. These results fail to support the widespread view that the TSH receptor of FRTL-5 cells signals, in part, through PIC activation. Our results suggest that TSH activates another, still undefined, mechanism that causes accumulation of an InsP3 and two isomers of InsP4.

Adenosine Triphosphate↗