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U Kumar

Publications and source records attributed to U Kumar.

At least 37 records · Page 2Linked to original sources
PubMed2001

Somatostatin suppresses endothelin-1-induced rat hepatic stellate cell contraction via somatostatin receptor subtype 1.

BACKGROUND & AIMS: Hepatic stellate cells (HSCs) are considered therapeutic targets to decrease portal hypertension. To elucidate some of the hemodynamic effects of somatostatin (SST) on portal pressure, the presence and function of SST receptors (SSTRs) on HSCs were investigated. METHODS: SSTR messenger RNA expression, and SSTR presence was investigated using reverse-transcription polymerase chain reaction, real-time quantitative polymerase chain reaction, Western blotting, and immunohistochemistry. The function of SSTRs was studied by examining the effects of SST and specific SSTR agonists on endothelin-1(ET-1)-induced HSC contraction. RESULTS: Specific amplicons for SSTR subtypes 1, 2, and 3 were demonstrated in rat liver and in activated HSCs. The presence of SSTR subtypes 1, 2, and 3 was confirmed by Western blotting. With immunohistochemistry, a strong staining of HSCs was obtained for SSTR subtypes 1, 2, and 3 in CCl4-treated rats, but not in normal rat liver. Incubation of HSCs on collagen gels with buffer, 10(-8) mol/L SST, and 2 x 10(-8) mol/L ET-1 resulted in collagen surface area decreases of 5.5% +/- 3.3%, 6.8% +/- 4.4%, and 49.8% +/- 8.3%, respectively. Relative contraction of gels preincubated with 10(-8) mol/L SST followed by 2 x 10(-8) mol/L ET-1 or vice versa as compared with maximal contraction (100%) with 2 x 10(-8) mol/L ET-1 were 72.6% +/- 17.9% and 76.2% +/- 12.6%, respectively (P < 0.05). SSTR agonist 1, but not SSTR agonist 2 or 3, was able to counteract the contractile effect of ET-1. CONCLUSIONA: Activated rat HSCs bear SSTR subtypes 1, 2, and 3. SST causes significant partial inhibition of ET-1-induced contraction of activated HSCs, mainly by stimulation of SSTR subtype 1.

Animals↗
PubMed2001

Laparoscopic approach to adrenal carcinoma.

There is general agreement on the suitability of the laparoscopic approach for benign adrenal lesions but controversy about using laparoscopy for suspected adrenal malignancy. This article reviews the literature on laparoscopic adrenalectomy for cancer: the operative techniques and indications and contraindications.

Adrenal Gland Neoplasms↗
PubMed2001

Effects of fibrin glue on injured rabbit ureter.

BACKGROUND AND OBJECTIVE: Fibrin glue is used as a hemostatic agent, has potential as a tissue adhesive, and may promote tissue healing. The histologic effects of fibrin glue on the ureter have not yet been fully investigated. We studied the effect of fibrin glue on the thickness of various layers of injured and uninjured ureters and its effect on vessel density in the rabbit model. MATERIALS AND METHODS: Rabbits were divided into two groups. The ureters were exposed using a midline abdominal incision. In the study group, one of the ureters was crushed, and fibrin glue was instilled around both ureters. In the control group, one of the ureters was crushed, but no fibrin glue was instilled. The animals were sacrificed at 6 weeks and the ureters examined histologically. Using NIH Image Analysis solftware, the thickness of the urothelium, muscular, and adventitial layers and the cross-sectional area of the ureters were measured. The vessel density of the ureters was also assessed. RESULTS: Whereas the thickness of the epithelium was increased in the crushed ureters treated with fibrin glue (20.7 microm v 15.3 microm), the thickness was reduced in the uncrushed ureters treated with fibrin glue compared with controls (16.3 microm v 19.8 microm). There was no statistically significant difference in the thickness of the muscular or adventitial layers in the study and control groups. There was a reduction in the cross-sectional area of the uncrushed ureters treated with fibrin glue compared with controls (7,095 microm2 v 9,409 microm2). In addition, the vessel density in the crushed ureters was reduced in ureters treated with fibrin glue compared with controls (0.00067/microm2 v 0.00108/micro2). In the uncrushed ureters, the difference was not statistically significant. CONCLUSIONS: Fibrin glue has potential as an adhesive agent in the ureter and may promote healing. It may affect epithelial layer thickness and vessel density of the ureter, but these effects were variable. Fibrin glue does not appear to have significant effects on the ureteral muscular and adventitial layers or on the overall cross-sectional area of all three layers. These results indicate that fibrin glue does not appear to have a detrimental effect on the ureter.

Animals↗
PubMed2001

Somatostatin is required for masculinization of growth hormone-regulated hepatic gene expression but not of somatic growth.

Pulsatile growth hormone (GH) secretion differs between males and females and regulates the sex-specific expression of cytochrome P450s in liver. Sex steroids influence the secretory dynamics of GH, but the neuroendocrine mechanisms have not been conclusively established. Because periventricular hypothalamic somatostatin (SST) expression is greater in males than in females, we generated knockout (Smst(-/-)) mice to investigate whether SST peptides are necessary for sexually differentiated GH secretion and action. Despite marked increases in nadir and median plasma GH levels in both sexes of Smst(-/-) compared with Smst(+/+) mice, the mutant mice had growth curves identical to their sibling controls and retained a normal sexual dimorphism in weight and length. In contrast, the liver of male Smst(-/-) mice was feminized, resulting in an identical profile of GH-regulated hepatic mRNAs between male and female mutants. Male Smst(-/-) mice show higher expression of two SST receptors in the hypothalamus and pituitary than do females. These data indicate that SST is required to masculinize the ultradian GH rhythm by suppressing interpulse GH levels. In the absence of SST, male and female mice exhibit similarly altered plasma GH profiles that eliminate sexually dimorphic liver function but do not affect dimorphic growth.

Animals↗
PubMed2001

Inhibitory effect of 1-benzyl-5[(C)-2,6-dimethyl-1,5-heptadienyl] imidazole (KK-42) on desert locust, Schistocerca gregaria forsk.

Imidazole compound KK-42 was tested for its inhibitory effect on Schistocerca gregaria. The compound caused 80% mortality after 19 days of treatment with 100 microg of KK-42/insect. It also caused the production of deformed adults at even lower doses. Ecdysteroid content, when estimated by RIA, declined due to KK-42 treatment in both haemolymph and ovaries of the insect. Reduction in ecdysteroid titer was maximum at 100 microg of KK-42/insect. The value estimated by RIA was 0.34 ng/pL haemolymph as compared to 0.97 ng/microL in case of controls. Similarly,ecdysteroid content of ovaries detected was 0.48 ng/mg in treated ones as compared to 0.61 ng/mg in controls. Histological studies, however, revealed no alteration in the ovarian tissues due to KK-42 treatment.

Animals↗
PubMed2001

Covert bacteriuria in nephrotic syndrome.

Prevalence of covert bacteriuria in patients of nephrotic syndrome admitted for kidney biopsy was studied in 205 patients. Age ranged from 10 years to 65 years. 148 patients were male and 57 were female. Prevalence of covert bacteriuria was found in 38 patients (18.53%). In bacteriuric patients 30 were male, 8 were female. Escherichia coli was the commonest organism grown in bacteriuric patients (30 or 78.9%). Serum albumin was low and 24-hour urinary protein excretion was high in bacteriuric patients in comparison to abacteriuric patients. In bacteriuric patients membranous nephropathy was the commonest histopathological finding present in 15 patients (39.47%).

Adolescent↗
PubMed2000

Receptors for dopamine and somatostatin: formation of hetero-oligomers with enhanced functional activity.

Somatostatin and dopamine are two major neurotransmitter systems that share a number of structural and functional characteristics. Somatostatin receptors and dopamine receptors are colocalized in neuronal subgroups, and somatostatin is involved in modulating dopamine-mediated control of motor activity. However, the molecular basis for such interaction between the two systems is unclear. Here, we show that dopamine receptor D2R and somatostatin receptor SSTR5 interact physically through hetero-oligomerization to create a novel receptor with enhanced functional activity. Our results provide evidence that receptors from different G protein (heterotrimeric guanine nucleotide binding protein)-coupled receptor families interact through oligomerization. Such direct intramembrane association defines a new level of molecular crosstalk between related G protein-coupled receptor subfamilies.

Animals↗
PubMed2000

Subtypes of the somatostatin receptor assemble as functional homo- and heterodimers.

The existence of receptor dimers has been proposed for several G protein-coupled receptors. However, the question of whether G protein-coupled receptor dimers are necessary for activating or modulating normal receptor function is unclear. We address this question with somatostatin receptors (SSTRs) of which there are five distinct subtypes. By using transfected mutant and wild type receptors, as well as endogenous receptors, we provide pharmacological, biochemical, and physical evidence, based on fluorescence resonance energy transfer analysis, that activation by ligand induces SSTR dimerization, both homo- and heterodimerization with other members of the SSTR family, and that dimerization alters the functional properties of the receptor such as ligand binding affinity and agonist-induced receptor internalization and up-regulation. Double label confocal fluorescence microscopy showed that when SSTR1 and SSTR5 subtypes were coexpressed in Chinese hamster ovary-K1 cells and treated with agonist they underwent internalization and were colocalized in cytoplasmic vesicles. SSTR5 formed heterodimers with SSTR1 but not with SSTR4 suggesting that heterodimerization is a specific process that is restricted to some but not all receptor subtype combinations. Direct protein interaction between different members of the SSTR subfamily defines a new level of molecular cross-talk between subtypes of the SSTR and possibly related receptor families.

Dimerization↗
PubMed2000

Sequence, expression and reconstitution of an HCV genome from a British isolate derived from a single blood donation.

Morphological analysis of hepatitis C virus and development of antiviral drugs to eradicate this agent have been seriously hampered by the low viraemias observed during natural infection and the unavailability of a cell culture system for virus propagation. Recently a low-grade hepatitis has been reported in chimpanzees after intrahepatic transfection of full-length synthetic HCV RNA and successful infections shown to be critically dependent on the integrity and genetic homogeneity of the reconstituted clone. In this study we describe and characterize a full HCV RNA sequence derived from a case of chronic sporadic hepatitis. The genotype was shown to be 1a with a low level of intraclonal sequence heterogeneity, and processing of both structural and nonstructural proteins has been documented. The assembly of the full genome has also been achieved. The low level of intraclonal variation observed may reflect infection with a single isolate and the fact that cloning was performed on virus obtained from a single blood donation makes this clone a good candidate for future in vivo and in vitro transfection studies.

Animals↗
PubMed2000

Simple nephrectomy: transperitoneal approach.

Transperitoneal laparoscopic nephrectomy is performed much as originally described by Clayman and associates, although preoperative embolization of the kidney is no longer routine. Some surgeons use a hand-assisted technique, especially in difficult cases or when the organ is being removed intact, as in live-donor nephrectomy.

Adult↗
PubMed1999

Agonist-dependent up-regulation of human somatostatin receptor type 1 requires molecular signals in the cytoplasmic C-tail.

We have previously reported that the human somatostatin receptor type 1 (hSSTR1) stably expressed in Chinese hamster ovary-K1 cells does not internalize but instead up-regulates at the membrane during continued agonist treatment (1 microM somatostatin (SST)-14 x 22 h). Here we have investigated the molecular basis of hSSTR1 up-regulation. hSSTR1 was up-regulated by SST in a time-, temperature-, and dose-dependent manner to saturable levels, in intact cells but not in membrane preparations. Although hSSTR1 was acutely desensitized to adenylyl cyclase coupling after 1 h SST-14 treatment, continued agonist exposure (22 h) restored functional effector coupling. Up-regulation was unaffected by cycloheximide but blocked by okadaic acid. Confocal fluorescence immunocytochemistry of intact and permeabilized cells showed progressive, time-dependent increase in surface hSSTR1 labeling, associated with depletion of intracellular SSTR1 immunofluorescent vesicles. To investigate the structural domains of hSSTR1 responsible for up-regulation, we constructed C-tail deletion (Delta) mutants and chimeric hSSTR1-hSSTR5 receptors. Human SSTR5 was chosen because it internalizes readily, displays potent C-tail internalization signals, and does not up-regulate. Like wild type hSSTR1, Delta C-tail hSSTR1 did not internalize and additionally lost the ability to up-regulate. Swapping the C-tail of hSSTR1 with that of hSSTR5 induced internalization (27%) but not up-regulation. Substitution of hSSTR5 C-tail with that of hSSTR1 converted the chimeric receptor to one resembling wild type hSSTR1 (poor internalization, 71% up-regulation). These results show that ligand-induced up-regulation of hSSTR1 occurs by a temperature-dependent active process of receptor recruitment from a pre-existing cytoplasmic pool to the plasma membrane. It does not require new protein synthesis or signal transduction, is sensitive to dephosphorylation events, and critically dependent on molecular signals in the receptor C-tail.

Adenylate Cyclase Toxin↗
PubMed1999

Localization of Niemann-Pick C1 protein in astrocytes: implications for neuronal degeneration in Niemann- Pick type C disease.

Niemann-Pick type C disease (NP-C) is an inherited neurovisceral lipid storage disorder characterized by progressive neurodegeneration. Most cases of NP-C result from inactivating mutations of NPC1, a recently identified member of a family of genes encoding membrane-bound proteins containing putative sterol sensing domains. By using a specific antipeptide antibody to human NPC1, we have here investigated the cellular and subcellular localization and regulation of NPC1. By light and electron microscopic immunocytochemistry of monkey brain, NPC1 was expressed predominantly in perisynaptic astrocytic glial processes. At a subcellular level, NPC1 localized to vesicles with the morphological characteristics of lysosomes and to sites near the plasma membrane. Analysis of the temporal and spatial pattern of neurodegeneration in the NP-C mouse, a spontaneous mutant model of human NP-C, by amino-cupric-silver staining, showed that the terminal fields of axons and dendrites are the earliest sites of degeneration that occur well before the appearance of a neurological phenotype. Western blots of cultured human fibroblasts and monkey brain homogenates revealed NPC1 as a 165-kDa protein. NPC1 levels in cultured fibroblasts were unchanged by incubation with low density lipoproteins or oxysterols but were increased 2- to 3-fold by the drugs progesterone and U-18666A, which block cholesterol transport out of lysosomes, and by the lysosomotropic agent NH4Cl. These studies show that NPC1 in brain is predominantly a glial protein present in astrocytic processes closely associated with nerve terminals, the earliest site of degeneration in NP-C. Given the vesicular localization of NPC1 and its proposed role in mediating retroendocytic trafficking of cholesterol and other lysosomal cargo, these results suggest that disruption of NPC1-mediated vesicular trafficking in astrocytes may be linked to neuronal degeneration in NP-C.

Amino Acid Sequence↗
PubMed1999

Apolipoprotein D gene expression in the rat brain and light and electron microscopic immunocytochemistry of apolipoprotein D expression in the cerebellum of neonatal, immature and adult rats.

Apolipoprotein D gene and protein expression were investigated in the rat brain and cerebellum, respectively, during development. Apolipoprotein D gene expression was first observed in embryonic day 12 rat brain, with a moderate increase in apolipoprotein D messenger RNA levels towards the later part (embryonic days 15-17) of gestation. In the postnatal rat brain, a marked induction of apolipoprotein D messenger RNA occurred at postnatal day 10, with progressively higher levels of apolipoprotein D messenger RNA observed up to postnatal day 20. Somewhat lower, but none the less high, levels of apolipoprotein D messenger RNA continued to be present in brains of adult animals. In the immature cerebellum (day 3 up to one- to two-week-old rats), there were many densely labeled apolipoprotein D-immunoreactive cells that had features of oligodendrocyte precursors. Purkinje neurons showed apolipoprotein D immunoreactivity in one- to two-week-old animals, after which there appeared to be some decrease in staining. Oligodendrocytes in the cerebella of two-week-old animals were strongly apolipoprotein D positive, with immunoreactivity declining in older animals. These results reveal a maturation-associated induction of apolipoprotein D gene expression in the rat brain, and expression of apolipoprotein D in glial (immature oligodendrocyte) cells in the immature cerebellum, followed by specific expression of apolipoprotein D in Purkinje neurons.

Aging↗
PubMed1999

Unusual cases of congenital cholesteatoma of the ear.

Congenital cholesteatoma may originate at various sites in the temporal bone. For example, in the petrous apex, the cerebellopontine angle, the middle ear cavity, the mastoid process or the external auditory canal. The least common site being the mastoid process. We present two cases of congenital cholesteatoma of the mastoid process, each presenting with different symptoms and at different ages. Both patients underwent surgical treatment, which confirmed the diagnosis and radiological findings.

Adolescent↗
PubMed1999

Differential regulation of somatostatin receptor types 1-5 in rat aorta after angioplasty.

Treatment of restenosis after angioplasty with octapeptide somatostatin (SST) analogs has met with variable success. These analogs bind with high affinity to only two SST receptor (SSTR) subtypes (2 and 5), display moderate affinity for SSTR3, and low affinity for SSTR1 and 4. To optimize the vasculoprotective effect of SST, we have investigated the pattern of expression of all five SSTRs in rat thoracic aorta in the resting state and at 15 min, 3, 7, and 14 days after balloon endothelial denudation. SSTR1-5 were analyzed as mRNA by semiquantitative reverse transcriptase-polymerase chain reaction and as protein by immunocytochemistry. All five SSTRs were expressed in rat aorta both as mRNA and protein and displayed a time-dependent, subtype-selective response to endothelial denudation. mRNA for SSTR1 and 2 increased acutely (SSTR1 > SSTR2) on days 3 and 7, coincident with smooth muscle cell (SMC) proliferation, and declined to basal levels by day 14. SSTR3 and 4 displayed a different pattern with a delayed, more gradual increase in mRNA beginning at days 3-7 and continued to increase thereafter. SSTR5 mRNA was constitutively expressed at a low level and showed no change during the 2 wk postinjury period. By immunohistochemistry, SSTR1-5 antigens were localized predominantly in SMC that were present in the media or had migrated into the intima; antigen expression correlated with receptor mRNA expression. Notably, only SSTR1,3,4 were expressed in the intima: SSTR1 and 4 during the proliferative burst and SSTR3 and 4 after proliferation, when SMC migration into the intima continues. These results demonstrate dynamic changes in SSTR1-5 expression after vascular trauma localized to areas of vascular SMC migration and replication. In view of their early and prominent induction, SSTR1 may be the optimal subtype to target for inhibition of myointimal proliferation, and SSTR3 and 4 for migration and remodeling.

Angioplasty, Balloon↗