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Biomedical subjects

U Kumar

Publications and source records attributed to U Kumar.

At least 73 records · Page 4Linked to original sources
PubMed1997

Purification and partial characterization of chromogranin-A from human brain.

Chromogranin A was purified from post-mortem human brain tissue, obtained at autopsy by a three step chromatography procedure to a single band purity on SDS gel electrophoresis at 68 kDa. Purified protein was further characterized by immunoblotting using a mouse anti-chromogranin A monoclonal antibody LK2H10, which recognizes the 68 kDa chromogranin A in human brain. The results demonstrate a simple protocol of preparing CgA from the human brain. Chromogranin plays a very important role in various neurological disorder and has been examined immunohistochemically in Alzheimer's disease, Parkinson's disease, Pick's disease. The procedure of purification may be useful in further defining its biological function, biochemistry and physiological significance in the central nervous system and may be useful in delineating the molecular pathology of certain neurological disorders.

Animals↗
PubMed1997

Ligand binding pocket of the human somatostatin receptor 5: mutational analysis of the extracellular domains.

The ligand binding domain of G protein-coupled receptors for peptide ligands consists of a pocket formed by extracellular and transmembrane domain (TM) residues. In the case of somatostatin (SRIF), however, previous studies have suggested that the binding cavity of the octapeptide analog SMS201-995 (SMS) is lined by residues in TMs III-VII. The additional involvement of the extracellular domains for binding SMS or the natural SRIF ligands (SRIF-14, SRIF-28) has not been clarified. Using a cassette construct cDNA for the human somatostatin 5 receptor (sst5R), we systematically examined the role of exofacial structures in ligand binding by creating a series of mutants in which the extracellular portions have been altered by conservative segment exchange (CSE) mutagenesis for the extracellular loops (ECLs) and by deletion (for the NH2-terminal segment) or truncation analysis (ECL3). CHO-K1 cells were stably transfected with wild type or mutant human sst5R constructs, and agonist binding was assessed using membrane binding assays with 125I-LTT SRIF-28 ligand. Deletion of the NH2 terminus or CSE mutagenesis of ECL1 and ECL3 produced minor 2-8-fold decreases in affinity for SRIF-14, SRIF-28, and SMS ligands. Truncation of ECL3 to mimic the size of this loop in sst1R and sst4R (the two subtypes that do not bind SMS) did not interfere with the binding of SMS, SRIF-14, or SRIF-28. In contrast, both ECL2 mutants failed to bind 125I-LTT SRIF-28. Immunocytochemical analysis of nonpermeabilized cells with a human sst5R antibody revealed that the mutant receptors were targeted to the plasma membrane. Labeled SMS (125I-Tyr3 SMS) also failed to bind to the mutant ECL2 receptors. These results suggest a potential contribution of ECL2 (in addition to the previously identified residues in TMs III-VII) to the SRIF ligand binding pocket.

Amino Acid Sequence↗
PubMed1997

Pure tone audiometry and impedance screening of school entrant children by nurses: evaluation in a practical setting.

BACKGROUND: Screening for hearing loss in English children at entry to school (age 5-6 years) is usually by pure tone audiometry sweep undertaken by school nurses. This study aimed to compare the validity and screening rates of pure tone audiometry with impedance screening in these children. METHODS: Two stage pure tone audiometry and impedance methods of screening were compared in 610 school entry children from 19 infant schools in north east England. Both procedures were completed by school nurses. The results of screening were validated against subsequent clinical assessment, including otological examination and actions taken by an independent assessor. RESULTS: Both methods produced broadly similar validation indices after two stages of screening: sensitivity was 74.4% for both methods; specificity was 92.1% and 90.0%; and predicted values of a positive test 43.2% and 37.6% respectively for pure tone audiometry and impedance methods. Single stage screening in both methods produced higher sensitivity but lower specificity and predictive values of a positive test than two stage screening. Screening rates were appreciably higher with impedance methods than with pure tone audiometry. CONCLUSIONS: In choosing the method to be used, it must be borne in mind that the impedance method is technically more efficient but takes longer than pure tone audiometry screening. However, the latter method allows opportunity for other health inquiries in these children.

Audiometry, Pure-Tone↗
PubMed1997

Expression of the five somatostatin receptor (SSTR1-5) subtypes in rat pituitary somatotrophes: quantitative analysis by double-layer immunofluorescence confocal microscopy.

Using quantitative double-label fluorescence immunocytochemistry and confocal microscopy, we have analysed the pattern of expression of SSTR1-5 in normal rat pituitary somatotrophes. Antipeptide rabbit polyclonal antibodies were produced against the extracellular domains of SSTR1-5. SSTR antigens were colocalized in GH positive cells using rhodamine conjugated secondary antibody for SSTRs and FITC-conjugated secondary antibody for GH. SSTR5 was the predominant subtype which was expressed in 86 +/- 9.7% of GH cells followed by SSTR2 in 42 +/- 6.4% of GH positive cells. SSTR4 and SSTR3 were modestly expressed in 23 +/- 4.7% and 18 +/- 3.2% of somatotrophes respectively whereas SSTR1 was the least expressed subtype occurring in only 5 +/- 1.2% of somatotrophes. These results demonstrate variable expression of the 5 SSTRs in somatotrophes. The preponderance of the SST-28 preferring SSTR5 subtype correlates with the reported higher potency of SST-28 than SST-14 for inhibiting GH secretion.

Animals↗
PubMed1996

Free radicals in the neurotoxic actions of beta-amyloid.

The fragment of the beta-amyloid protein that contains the peptide sequence 25 to 35 of the parent compound, increases cytosolic calcium and is directly cytotoxic to neurons in tissue culture. The cytotoxic action of beta-amyloid has been considered to be the primary determinant of the neurodegeneration observed in Alzheimer's disease. The cytotoxic effects of beta-amyloid 25-35 or beta-amyloid 1-40 added to primary cultures of rat hippocampal or cortical neurons can be reduced or prevented by anti-oxidant lazaroid drugs such as U-74500A, U-78517F, or U-83836E. beta-amyloid 25-35 evokes an immediate increase in cytosolic calcium when added to suspensions of PC 12 cells, and is cytotoxic to PC 12 cells in tissue culture. Both the calcium-elevating and the cytotoxic actions of beta-amyloid 25-35 on PC 12 cells are reduced or prevented by lazaroid anti-oxidant drugs. Since the lazaroids have been shown to scavenge free radical species, the present results indicate that the actions of beta-amyloid 25-35 on calcium regulation and on cell survival are mediated by free radicals.

Amyloid beta-Peptides↗
PubMed1996

Purification and characterization of chromogranin-A from the adrenal gland of human and bovine.

In the present study, we report a simple, highly reproducible procedure for the purification of chromogranin A. A three step column chromatography of supernatant from human and bovine provided a major single band at M(r) 67 and two minor bands at low molecular mass. Identity of the major and minor bands of CgA was confirmed by western blotting using LK2H10, a monoclonal antibody against chromogranin A. Recognition of smaller fragments in the final preparation in both species by antibody to chromogranin A may suggest that these are the proteolytic breakdown product of the main protein. Bovine adrenal gland was found to be many fold richer in chromogranin than human adrenal gland. The simplification of the purification procedure for CgA may now help in elucidating further physiological function of this protein.

Adrenal Glands↗
PubMed1996

Agonist-dependent regulation of cloned human somatostatin receptor types 1-5 (hSSTR1-5): subtype selective internalization or upregulation.

Agonist regulation of somatostatin receptors (SSTRs) was investigated in stable CHO-K1 cells individually expressing the 5 human (h) SSTR subtypes. hSSTR 2,3,4, and 5 displayed rapid agonist-dependent internalization of [125I] LTT SST-28 ligand in a time- and temperature-dependent manner over 60 min. Maximum internalization of radioligand occurred with hSSTR3 (78%) followed by hSSTR5 (66%), hSSTR4 (29%) and hSSTR2 (20%). In contrast, hSSTR1 displayed virtually no internalization. Prolonged agonist treatment led to differential upregulation of some of the SSTRs. After 22 h, hSSTR1 was upregulated at the membrane by 110%, hSSTR2 and hSSTR4 by 26% and 22% respectively, whereas hSSTR3 and hSSTR5 showed little change. Agonist-induced recruitment of hSSTR1 to the membrane was confirmed by immunocytochemistry with hSSTR1 antibodies. These results show that SST regulates all 5 hSSTRs by differential subtype selective internalization or upregulation. Subtype selectivity for internalization and upregulation is inversely related.

Animals↗
PubMed1995

Hepatitis C virus type I(1a) in northern China.

Twenty-four patients with hepatitis C virus (HCV) antibody from the Chinese North Western province of Jilin were further analysed by the immunoblot assay-2 (RIBA-2), reverse transcription-polymerase chain reaction (RT-PCR) for serum HCV RNA detection, and direct sequence-genotyping. Good concordance was found between the original second generation HCV antibody ELISA, RIBA-2, and serum HCV RNA. The occurrence of genotype I (1a), a genotype not previously reported in China, is described in 5(20.8%) of 24 cases, in association with genotypes II(1b) and III(2a) which were found in 16(66.7%) and 3(12.5%) of 24 cases, respectively. Imported blood products were unlikely to be the source of infection with genotype I (1a) but could not be definitively ruled out.

Base Sequence↗
PubMed1995

Chronic hepatitis C virus infections: predictive value of genotype and level of viraemia on disease progression and response to interferon alpha.

The effects of hepatitis C virus genotype and viraemia on disease outcome in patients with chronic hepatitis C virus infection were studied. Patients infected with genotype 1 tended to develop more severe disease, and to respond less well to interferon (IFN) treatment, but no pretreatment variable successfully predicted either the severity of the disease or the response to IFN. Failure to eliminate the virus during the first three months of therapy, however, predicted a failure to derive long term benefit from the current IFN regime. Hence pretreatment variables cannot be used to determine whether individual patients will respond to IFN, but observations during the first three months of therapy can be used to decide which patients will not respond to prolonged therapy. In these patients consideration should be given to changing the IFN dosing regime or using alternative treatments.

Base Sequence↗
PubMed1995

Hepatitis C virus replication in hepatocellular carcinoma.

Hepatitis C virus (HCV) replication is reported in both tumour and non-tumour tissue in a case of hepatocellular carcinoma. Viral replication was established by showing the presence of minus strand HCV RNA by PCR amplification, after excluding residual reverse transcriptase activity of Taq polymerase. No minus strand was found in serum derived virion RNA. PCR amplified products from both tumour and non-tumour parenchyma were sequenced in the 5' non-coding region and shown to be identical. The genotype of this Indonesian patient was found to be 1b (or II), the most prevalent type in the Far East.

Base Sequence↗
PubMed1995

Family pathology and anorexia in the Indian context.

Frequent associations have been found between family interaction and anorectic behaviour. Family theorists have viewed anorexia as a manifestation of a dysfunctional family system. We report three families of cases of anorexia (one male and two female) where the symptom was a reflection of family pathology and was being maintained by it. The cases emphasize the need to assess families of anorectics in detail and view them in the cultural context of eating.

Adolescent↗
PubMed1995

Trash penis.

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Aortic Aneurysm, Abdominal↗
PubMed1994

Hypervariable region of hepatitis C virus envelope glycoprotein (E2/NS1) in an agammaglobulinemic patient.

In an agammaglobulinemic patient with chronic hepatitis C, a previously identified hypervariable region of the major envelope glycoprotein remained unchanged for 2.5 years. Serum-derived RNA amplified by reverse transcription-polymerase chain reaction was cloned in a bacterial vector, and a minimum of three independent clones were sequenced by dideoxy chain termination reaction. Comparison of consensus sequences from three different time points during the chronic phase of infection showed absolute homology at both amino acid and nucleotide levels. This finding provides support for the role of antibody selection in generating genetic variation and viral persistence; also, it is consistent with the hypothesis that an epitope within this region is the site of virus neutralization. The observations show that the hepatitis seen in hepatitis C virus infection is not dependent on the humoral immune response.

Agammaglobulinemia↗