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Biomedical subjects

S Mukherjee

Publications and source records attributed to S Mukherjee.

At least 127 records · Page 7Linked to original sources
PubMed1999

beta-arrestin-dependent desensitization of luteinizing hormone/choriogonadotropin receptor is prevented by a synthetic peptide corresponding to the third intracellular loop of the receptor.

Desensitization is a ubiquitous response of guanine nucleotide-binding protein-coupled receptors (GPCRs) characterized by the waning of effector activity despite continued presence of agonist. Binding of an arrestin to the activated, often phosphorylated GPCR triggers desensitization. We reported for the luteinizing hormone/choriogonadotropin receptor (LH/CG R) that beta-arrestin tightly bound to porcine ovarian follicular membranes mediates agonist-dependent desensitization of LH/CG R-stimulated adenylyl cyclase (AC) activity (Mukherjee, S., Palczewski, K., Gurevich, V. V., Benovic, J. L., Banga, J. P., and Hunzicker-Dunn, M. (1999) Proc. Natl. Acad. Sci. U. S. A. 96, 493-498). We now show that addition of a synthetic peptide corresponding to the entire third intracellular loop (3i) of the LH/CG R completely and specifically reverses desensitization of AC activity, with an ED50 of 10 microM but does not modulate basal, hCG-stimulated, or forskolin-stimulated AC activities. beta-Arrestin binds selectively to the 3i peptide coupled to activated Sepharose. Desensitization of LH/CG R-stimulated AC activity is rescued when the 3i peptide is preincubated with exogenous beta-arrestin. These results show that endogenous beta-arrestin participates in cell-free desensitization of agonist-dependent LH/CG R-stimulated AC activity in follicular membranes by interacting directly with the 3i loop of the receptor, thereby preventing Gs activation.

Amino Acid Sequence↗
PubMed1999

Parameter convergence and learning curves for neural networks.

We revisit the oft-studied asymptotic (in sample size) behavior of the parameter or weight estimate returned by any member of a large family of neural network training algorithms. By properly accounting for the characteristic property of neural networks that their empirical and generalization errors possess multiple minima, we rigorously establish conditions under which the parameter estimate converges strongly into the set of minima of the generalization error. Convergence of the parameter estimate to a particular value cannot be guaranteed under our assumptions. We then evaluate the asymptotic distribution of the distance between the parameter estimate and its nearest neighbor among the set of minima of the generalization error. Results on this question have appeared numerous times and generally assert asymptotic normality, the conclusion expected from familiar statistical arguments concerned with maximum likelihood estimators. These conclusions are usually reached on the basis of somewhat informal calculations, although we shall see that the situation is somewhat delicate. The preceding results then provide a derivation of learning curves for generalization and empirical errors that leads to bounds on rates of convergence.

Algorithms↗
PubMed1999

Characterization of a neutralization-escape variant of SHIVKU-1, a virus that causes acquired immune deficiency syndrome in pig-tailed macaques.

A chimeric simian-human immunodeficiency virus (SHIV-4) containing the tat, rev, vpu, and env genes of HIV type 1 (HIV-1) in a genetic background of SIVmac239 was used to develop an animal model in which a primate lentivirus expressing the HIV-1 envelope glycoprotein caused acquired immune deficiency syndrome (AIDS) in macaques. An SHIV-infected pig-tailed macaque that died from AIDS at 24 weeks postinoculation experienced two waves of viremia: one extending from weeks 2-8 and the second extending from week 18 until death. Virus (SHIVKU-1) isolated during the first wave was neutralized by antibodies appearing at the end of the first viremic phase, but the virus (SHIVKU-1b) isolated during the second viremic phase was not neutralized by these antibodies. Inoculation of SHIVKU-1b into 4 pig-tailed macaques resulted in severe CD4(+) T cell loss by 2 weeks postinoculation, and all 4 macaques died from AIDS at 23-34 weeks postinoculation. Because this virus had a neutralization-resistant phenotype, we sequenced the env gene and compared these sequences with those of the env gene of SHIVKU-1 and parental SHIV-4. With reference to SHIV-4, SHIVKU-1b had 18 and 6 consensus amino acid substitutions in the gp120 and gp41 regions of Env, respectively. These compared with 10 and 3 amino acid substitutions in the gp120 and gp41 regions of SHIVKU-1. Our data suggested that SHIVKU-1 and SHIVKU-1b probably evolved from a common ancestor but that SHIVKU-1b did not evolve from SHIVKU-1. A chimeric virus, SHIVKU-1bMC17, constructed with the consensus env from the SHIVKU-1b on a background of SHIV-4, confirmed that amino acid substitutions in Env were responsible for the neutralization-resistant phenotype. These results are consistent with the hypothesis that neutralizing antibodies induced by SHIVKU-1 in pig-tailed macaque resulted in the selection of a neutralization-resistant virus that was responsible for the second wave of viremia.

Amino Acid Sequence↗
PubMed1999

Endocytic sorting of lipid analogues differing solely in the chemistry of their hydrophobic tails.

To understand the mechanisms for endocytic sorting of lipids, we investigated the trafficking of three lipid-mimetic dialkylindocarbocyanine (DiI) derivatives, DiIC16(3) (1,1'-dihexadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate), DiIC12(3) (1,1'- didodecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate), and FAST DiI (1,1'-dilinoleyl-3,3,3', 3'-tetramethylindocarbocyanine perchlorate), in CHO cells by quantitative fluorescence microscopy. All three DiIs have the same head group, but differ in their alkyl tail length or unsaturation; these differences are expected to affect their distribution in membrane domains of varying fluidity or curvature. All three DiIs initially enter sorting endosomes containing endocytosed transferrin. DiIC16(3), with two long 16-carbon saturated tails is then delivered to late endosomes, whereas FAST DiI, with two cis double bonds in each tail, and DiIC12(3), with saturated but shorter (12-carbon) tails, are mainly found in the endocytic recycling compartment. We also find that DiOC16(3) (3,3'- dihexadecyloxacarbocyanine perchlorate) and FAST DiO (3, 3'-dilinoleyloxacarbocyanine perchlorate) behave similarly to their DiI counterparts. Furthermore, whereas a phosphatidylcholine analogue with a BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) fluorophore attached at the end of a 5-carbon acyl chain is delivered efficiently to the endocytic recycling compartment, a significant fraction of another derivative with BODIPY attached to a 12-carbon acyl chain entered late endosomes. Our results thus suggest that endocytic organelles can sort membrane components efficiently based on their preference for association with domains of varying characteristics.

Animals↗
PubMed1999

A direct role for arrestins in desensitization of the luteinizing hormone/choriogonadotropin receptor in porcine ovarian follicular membranes.

The luteinizing hormone/choriogonadotropin (LH/CG) receptor (R) is a heptahelical R that, upon agonist binding, activates the stimulatory guanine nucleotide-binding protein (Gs) and the downstream effector adenylyl cyclase (AC). Like other G protein-coupled Rs, the LH/CG R subsequently exhibits reduced agonist-dependent effector activity, or desensitization, in response to saturating agonist. Unlike desensitization of many other G protein-coupled Rs, the in vivo desensitization response of LH/CG R-stimulated AC activity of ovarian follicles to the preovulatory surge of LH can be mimicked under cell-free conditions. Based on evidence that porcine ovarian follicular membranes unexpectedly contained beta-arrestin-1, the role of arrestins in desensitization of the LH/CG R was investigated. Results showed that neutralizing arrestin antibodies blocked the development of desensitization and that desensitization was rescued with a synthetic peptide corresponding to the antibody-binding epitope on beta-arrestin-1. These results suggest that endogenous beta-arrestin-1 participates in agonist-dependent desensitization of the LH/CG R. Addition of recombinant purified beta-arrestin-1 mimicked human chorionic gonadotrophin to promote desensitization of human chorionic gonadotrophin-stimulated AC activity, in the presence of the ATP phosphorylation antagonist adenylyl-imidodiphosphate, with an ED50 of approximately 0.1 nM. Increased levels of an 87-kDa protein reactive with glycoprotein hormone R-reactive antibody, consistent with the LH/CG R, coimmunoprecipitated with follicular membrane beta-arrestin-1 in response to LH/CG R activation compared with unactivated R. Taken together, these results show that ovarian follicles contain membrane-associated beta-arrestin-1, that beta-arrestin-1 participates in agonist-dependent desensitization of the LH/CG R, and that the trigger for beta-arrestin-1 binding to the LH/CG R appears to be R activation.

Adenylyl Imidodiphosphate↗
PubMed1999

Non-Alcoholic Steatohepatitis (NASH).

Non-alcoholic steatohepatitis (NASH) is an increasingly common cause of persistently abnormal liver tests. Establishing a diagnosis of NASH requires the secure exclusion of alcohol abuse and hepatitis C as an alternate cause of liver injury. The gold standard of diagnosis is liver biopsy. Unfortunately, NASH, although a common entity, is without a satisfactory treatment. Weight reduction, optimum blood glucose control, and elimination of medications implicated in causing the disorder are sensible first steps in treatment. Drug therapy should not be used unless there is histologic evidence of necro-inflammatory injury and/or fibrosis. Ursodeoxycholic acid (UDCA) has been reported to be of benefit in non-controlled trials and anecdotal case reports. Our approach is to use ursodeoxycholic acid in a dose of 15 mg/kg, and to monitor serial liver enzyme tests. Predictable normalization of liver tests often results, but relentless progression of liver injury can occur in the face of consistently normal liver tests. Close follow-up is mandatory after establishing a diagnosis of NASH. Newer, more effective drugs are needed to treat NASH in a controlled trial environment.

Journal Article↗
PubMed1999

Synthesis of E- and Z-pyrazolylacrylonitriles and their evaluation as novel antioxidants.

A facile synthesis of (Z)- and (E)-2-(5-arylpyrazol-3-yl)-3-(pyrrol-2-yl)acrylonitriles and (Z)-2-(1,3-diarylpyrazol-5-yl)-3-pyrrol-2-yl)acrylonitriles, and isomerisation of (Z)-2-(5-arylpyrazolyl)acrylonitriles to (E)-2-(5-arylpyrazolyl)acrylonitriles under basic conditions have been reported. (Z)-2-(1,3-Diarylpyrazolyl)acrylonitriles did not undergo isomerisation under the similar conditions. New compounds were identified on the basis of their spectral data (1H-, 13C-, 1H-1H COSY, NOESY, NOE, HMQC NMR, IR, UV and EI mass). The structures of one acrylonitrile and five of their precursor 6-arylpyran-2-ones and cyanomnethylpyrazoles were confirmed by X-ray crystallographic studies. Effects of pyrazolylacrylonitriles and their precursors on rat liver-microsomal lipid peroxidation were evaluated in vitro with a view to establish structure activity relationship and to identify a lead compound.

Acrylonitrile↗
PubMed1999

Sex-specific alterations in chromatin conformation of the brain of aging mouse.

Chromatin conformation has been analysed in the brain cortex of adult (24+/-2 weeks) and old (65+/-4 weeks) male and female mice. Nuclei purified from different groups of mice were digested with MNase and DNase I for varying time periods (0-90 min), and with endogenous endonucleases for 1 h. MNase and DNase I digestion kinetics showed that the percentage of acid solubility of chromatin was relatively lower in old than adult and in female than male. This was further supported by electrophoretic analysis of nuclease digested DNA fragments. When the nuclei were incubated with only Ca2+ or Mg2+, no endonuclease digestion was observed. However, under similar conditions, the liver DNA was cleaved substantially. When divalent cations were added together, they activated endogenous endonucleases and digested the brain chromatin. The activity of Ca2+/Mg2+-dependent endogenous endonucleases was higher in male than female. Thus the accessibility of chromatin to MNase, DNase I and endogenous endonucleases was higher in male than female, and MNase as well as DNase I were more active in adult than old. Such sex- and age-dependent conformation of chromatin may attribute to differential expression of genes in the mouse brain.

Aging↗
PubMed1999

Age-dependent degradation of amyloid precursor protein in the post-mortem mouse brain cortex.

We have examined the degradation of amyloid precursor protein (APP) in the brain cortex of adult (24 +/- 2) and old (58 +/- 2) mice at different post-mortem time intervals (0, 1.5, 3, 6, 12 and 24 h). The brain cortex extract was prepared and processed for immunoblotting using antibodies against N-terminal 47-62 amino acids (Asp29) and central 301-316 amino acids containing Kunitz protease inhibitor (KPI) domain (Asp45) of APP. Asp29 (N-terminal) recognizes two bands of 140 and 112 kDa. The amount of 140 kDa is relatively higher in adult than old. The level of 112 kDa is 1.6 times lower in adult than old. It shows no remarkable change with varying post-mortem time. On the other hand, Asp45 (KPI) detects two bands of 110 and 116 kDa. While 116 kDa disappears rapidly after death of the animal, 110 kDa shows no remarkable change with different post-mortem periods. Further incubation of the disrupted tissue at 4 degrees C for 24 h and immunoblot analysis with Asp29 (N-terminal) shows 112 kDa in both ages but 58.5 kDa in adult and 70 kDa in old only. Analysis with Asp45 (KPI) shows only 54 kDa which increases after 3 h in adult but decreases significantly after 1.5 h and becomes undetectable at 24 h in old. Thus the present findings indicate that APP is degraded in a precise pattern and it depends on cellular intactness, post-mortem period and age of the animal.

Age Factors↗
PubMed1999

Role of peripheral benzodiazepine receptors on secretion of surfactant in guinea pig alveolar type II cells.

Granular type II cells located in the alveolar epithelium synthesize and secrete pulmonary surfactant and have specialized ion transport system. Alveolar type II cells are stimulated to secrete pulmonary surfactant by a variety of agonists. One mechanism by which extracellular signals are perceived by cells is the mobilization of intracellular Ca2+. Peripheral benzodiazepine receptors (PBRs) are present in both peripheral tissues and central nervous system. We have previously reported the presence of high density PBRs in lung and alveolar type II cells. It is known that both PBRs and beta-adrenergic receptors (beta-ARs) play an important role in cellular Ca2+ transport. Furthermore, we have suggested earlier that PBRs are someway functionally associated with the beta-ARs. The objective of the present study was to determine whether PBRs play any role in the secretion of surfactant by alveolar type II cells. Alveolar type II cells were isolated from normal weanling guinea pigs by panning method and incubated with 3H-palmitic acid in minimum essential medium to synthesize labelled dipalmitoyl phosphatidylcholine (DPPC). After washing, the cells were treated at 37 degrees C for one hour with 10 microM isoproterenol (IP) in the presence and absence of 10 microM Ro 5-4864, an agonist for PBRs. After one hour, the release of labelled DPPC in the medium was analyzed. The control cells released DPPC without any addition of a ligand. However, the treatment of cells with IP, Ro 5-4864 and IP + Ro 5-4864 caused 24, 52 and 17]% increase in the secretion of DPPC, respectively. In another experiment, type II cells were loaded with Fura-2 dye and treated with either IP or epineprine or Ro 5-4864. Both isoproterenol and epinephrine caused a significant increase in the level of cytosolic free Ca2+. However, Ro 5-4864 caused not only a decrease in the level of cytosolic free Ca2+ but also counteracted the stimulatory effect of IP. This may suggest that while ligands for ARs stimulate Ca2+ release into cytosol, the ligand for PBRs stimulates efflux of Ca2+ in alveolar type cells. Thus, the increased secretion of surfactant by the ligand of PBRs in alveolar type II cells may be mediated through its effects on increased Ca2+ efflux.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1999

The appropriateness of western models of parent involvement in Calcutta, India. Part 2: Implications of family roles and responsibilities.

As the initial stage of an evaluation of services offered to families at Shishu Sathi, West Bengal, by Spastics Society of Eastern India, a partial replication of a study from Guyana was undertaken. The overall aim was to examine the extent to which it is realistic and practicable to apply Western models of parental participation in intervention with families in West Bengal, in terms of the extent to which the project families meet requirements implicit in these Western models. The results are presented in two papers. Part 1 examined parents' beliefs concerning child development and the effects of teaching on children's development. This paper explores the division of roles and responsibilities within families in relation to demands on family members and the time available to parents for active participation in a parent involvement project. The results of the study demonstrate that, whilst mothers' domestic responsibilities are particularly onerous, their roles and those of other family members varied according to the type of family structure. Implications for service delivery and involvement of the wider family are discussed.

Adult↗
PubMed1999

The appropriateness of western models of parent involvement in Calcutta, India. Part 1: Parents' views on teaching and child development.

As the initial stage of an evaluation of services offered to families at Shishu Sathi, West Bengal, by Spastics Society of Eastern India, a partial replication of a Guyanese study was undertaken. The results are presented in two papers. This paper (part 1) examines parents' beliefs concerning child development and the effectiveness of teaching. Part 2 explores roles and responsibilities within families in relation to the time available to parents for active participation in a parent involvement project. The aim is to find out in terms of the above issues whether, and to what extent, it is appropriate to apply Western models of Intervention with families in West Bengal. The findings suggest that strong similarities exist between parents' beliefs in this study, the Guyanese sample, and Western expectations, concerning child development and the effects of teaching, though with certain interesting exceptions. Possible reasons for these differences are discussed along with implications for the design and delivery of services.

Adult↗
PubMed1999

Absence of a relationship between endometriosis and the N314D polymorphism of galactose-1-phosphate uridyl transferase in a UK population.

An association between the N314D polymorphism of galactose-1-phosphate uridyl transferase and endometriosis has recently been reported in a North American population. To determine whether such an association exists in the UK population, we genotyped 148 women with sporadic (n = 91) or familial (n = 57) endometriosis, a control population of 95 male blood donors and a control group of 53 women with a normal pelvis at hysterectomy. Heterozygosity for the polymorphism was found in 14.9% (22/148) of affected women, 13.7% (13/95) of male blood donors and 11.3% (6/53) of women with a normal pelvis. There was no statistically significant difference in the frequency of the polymorphism between cases and controls in the UK population, even when the cases were divided into groups of moderate-severe disease, sporadic cases or familial cases. We conclude that the galactose-1-phosphate uridyl transferase N314D polymorphism is unlikely to be associated with endometriosis in the UK population.

Adult↗
PubMed1999

An unusual cause of recurrent abdominal pain.

Abdominal pain is a common complaint with diverse etiologies. We describe an unusual case of recurrent abdominal pain in an adult due to lead poisoning, a condition usually associated with childhood. A previously healthy 42-yr-old man presented with 2 days of severe crampy abdominal pain and a 1-month history of constipation. Physical examination was remarkable for diffuse abdominal pain but peritoneal signs were not present. Blood tests were remarkable for hematocrit of 33 and mean cell volume of 78, with ovalocytes and basophilic stippling on blood smear. Abdominal x-ray showed stool throughout the colon and a nonspecific bowel gas pattern. The patient was treated with intravenous fluids and enemas, and his symptoms resolved within 2 days. Repeat history taking revealed he had been stripping paint from an old Victorian house in the preceding few months. He was discharged after a blood lead level was obtained. Before his clinic appointment he was readmitted 2 days later with recurrent abdominal pain. His blood lead level was elevated at 110 microg/dl (toxic range). After consultation with the Occupational Health and Safety Administration and local poison control service, he was treated with intravenous calcium edetate disodium and intramuscular dimercaprol. He was asymptomatic at discharge, with a level of 56 microg/dl. Two weeks later, a repeat level was elevated at 72 microg/dl, for which he received a 3-wk course of oral dimercaptosuccimer. Subsequent levels were unremarkable, and the patient remains asymptomatic. Abdominal pain secondary to lead poisoning in adults is uncommon. This case highlights the importance of taking a detailed occupational history and appropriately using "routine" blood tests to diagnose a rare condition that presented with a common complaint.

Abdominal Pain↗
PubMed1999

Roles of Gi and Gq/11 in mediating desensitization of the luteinizing hormone/choriogonadotropin receptor in porcine ovarian follicular membranes.

Although desensitization of most guanine nucleotide-binding (G) protein receptors is triggered by phosphorylation of the receptor, desensitization of the LH/CG receptor (-R) in porcine follicular ovarian membranes appears to be independent of LH/CG-R phosphorylation. We therefore evaluated whether desensitization of the LH/CG-R reflected a direct inhibition of adenylyl cyclase (AC) activity by either the alpha-subunit of Gi or betagamma-subunits derived from any of the membrane G proteins activated in response to LH/CG-R activation or whether desensitization reflected a competition between Gs and a G protein that activated phospholipase C for binding sites on the LH/CG-R. The results showed that follicular membrane AC activity was not inhibited upon activation of the LH/CG-R despite evidence that the ACs in follicular membranes, when maximally activated by forskolin, could be inhibited when membrane G proteins were activated by guanyl-5'-yl imidodiphosphate, and that pertussis toxin pretreatment of membranes raised forskolin-stimulated AC activity, consistent with a tonic inhibition of follicular membrane AC activity. Similarly, agonist-stimulated desensitization of LH/CG-R-stimulated AC activity was not inhibited by pertussis toxin. Therefore, desensitization is not the result of inhibition of AC mediated by an inhibitory Gi subunit. Follicular membrane AC was also not inhibited by Gbetagamma subunits freed with activation of Gs Gq/11, or G13, based on the inabilities of exogenous Gbetagamma to promote desensitization and of a protein that sequesters Gbetagamma to inhibit desensitization. Desensitization was also not inhibited by a Gq/11 C-terminal peptide or antiserum directed toward the C-terminus of Gq/11, nor was it reversed with the addition of Gbetagamma to membranes exhibiting desensitized LH/CG-R, suggesting that desensitization is independent of coupling of the LH/CG-R to Gq/11. These results indicate that agonist-dependent desensitization of LH/CG-R-stimulated AC activity is mediated by a unique mechanism.

Adenylate Cyclase Toxin↗