Search PubMed⌕ Search

Biomedical subjects

A Kumar

Publications and source records attributed to A Kumar.

At least 361 records · Page 20Linked to original sources
PubMed1999

Alignment of the B" subunit of RNA polymerase III transcription factor IIIB in its promoter complex.

TFIIIB, the central transcription initiation factor of the eukaryotic nuclear RNA polymerase (pol) III is composed of three subunits: the TATA-binding protein; Brf, the TFIIB-related subunit; and B", the Saccharomyces cerevisiae, TFC5 gene product. The orientation of the B" subunit within the TFIIIB-DNA complex has been analyzed at two promoters by two approaches that involve site-specific photochemical protein-DNA cross-linking: a collection of B" internal and external deletion proteins has been surveyed for those deletions that alter the interaction of B" with DNA or change the orientation of B" relative to DNA; a method for regionally mapping cross-links between specific DNA sites and (32)P-end-labeled protein has also been applied. The results map an N-proximal segment of B" to the upstream end of the TFIIIB-DNA complex and amino acids 299-315 to the principal DNA-contact site, approximately 8 base pairs upstream of the TATA box. The analysis also indicates that a segment comprising amino acids 316-434 loops away from DNA, and locates the C-proximal 170 amino acids of B" downstream of the TATA box. Examination of two-cross-link products formed by DNA with adjacent and nearby photoactive nucleotides supports the conclusion that Brf and B" share an extended interface along the length of the TFIIIB-DNA complex.

Base Sequence↗
PubMed1999

Tubulointerstitial nephritis antigen: an extracellular matrix protein that selectively regulates tubulogenesis vs. glomerulogenesis during mammalian renal development.

Tubulointerstitial nephritis antigen (TIN-ag) is an extracellular matrix protein and is expressed in the renal tubular basement membranes. Its role in metanephric development was investigated. TIN-ag cDNA, isolated from the newborn mouse library, had an ORF of 1,425 nucleotides, a putative signal sequence, and an ATP/GTP-binding site. The translated sequence had approximately 80% identity with rabbit TIN-ag. Among various tissues, TIN-ag mRNA was primarily expressed in the newborn kidney. In the embryonic metanephros, TIN-ag expression was confined to the distal convolution or pole of the S-shaped body, the segment of the nascent nephron that is the progenitor of renal tubules. Treatment with TIN-ag antisense oligodeoxynucleotide induced dysmorphogenesis of the embryonic metanephroi, malformation of the S-shaped body, and a decrease in the tubular population, whereas the glomeruli were unaffected. Treatment also led to a decrease of TIN-Ag mRNA, de novo synthesis of TIN-ag protein, and its antibody reactivity. The mRNA expression of glomerular epithelial protein 1 (a marker for renal podocytes), anti-heparan-sulfate-proteoglycan antibody reactivity, and wheat germ agglutinin lectin staining of the metanephros were unaffected. The anti-TIN-ag antibody treatment also caused deformation of the S-shaped body and a reduction in the tubular population, whereas the glomeruli were unchanged. The data suggest that the TIN-ag, unlike other basement membrane proteins, selectively regulates tubulogenesis, whereas glomerulogenesis is largely unaffected.

Amino Acid Sequence↗
PubMed1999

Molecular cytogenetics of a de novo interstitial deletion of chromosome arm 6q in a developmentally normal girl.

Using fluorescence in situ hybridization and microsatellite analysis, we have characterized a de novo interstitial deletion on the long arm of chromosome 6 [46,XX,del(6) (q23.3q24.2)] in a developmentally normal girl with very mild phenotypic abnormalities. The deletion was paternal in origin and was between markers WI-5023 and D6S1042. The size of the deletion was estimated to be approximately 4-5 Mb. The normal phenotype in this patient might be the result of imprinting of paternal copies of genes located in the segment 6q23. 3-q24.2. Alternatively, the genes located in the segment 6q23.3-q24. 2 might not be subject to dosage effects and therefore the haploinsufficiency of genes in this segment might not have phenotypic consequences.

Child, Preschool↗
PubMed1999

Age of onset of depression and quantitative neuroanatomic measures: absence of specific correlates.

The purpose of our study was to examine the relationship between volumetric neuroanatomic measures and age of onset of illness in subjects with late-life major depression. Our sample was composed of 51 elderly subjects with Major Depressive Disorder who were scanned using a 1.5-tesla GE magnetic resonance imaging scanner with head coil. Absolute total and focal brain volumes were obtained together with quantified estimates of high intensity lesions. The relationship of these measures to onset age was examined using a regression while adjusting for subjects' current age and total intracranial volume. There was no significant linear relationship between age of onset of the first episode and any of the neuroanatomic measures examined. These data do not support the notion that neuroanatomical contributions to depression increase with a later age of onset of illness.

Brain↗
PubMed1999

Sustained suppression of plasma HIV RNA is associated with an increase in the production of mitogen-induced MIP-1alpha and MIP-1beta.

The chemokine receptor CCR5 has been shown to be a major coreceptor for HIV-1. The chemokines that bind to this receptor (MIP-1alpha, MIP-1beta, and RANTES) are potent inhibitors of HIV replication and may play an important role in the pathophysiology of HIV disease. We investigated the effect of potent antiretroviral therapy (ritonavir and saquinavir) on the production of MIP-1alpha, MIP-1beta, and RANTES in 19 HIV-infected patients who had sustained decreases in plasma HIV RNA levels (<200 copies/ml). Chemokine concentrations were measured in serum, plasma, and PHA-stimulated PBMCs at baseline and 24 and 48 weeks after initiating therapy. MIP-1alpha, MIP-1beta, and RANTES levels in serum and plasma did not significantly change in the 48-week period. In contrast, MIP-1alpha and MIP-1beta secreted by PHA-stimulated PBMCs increased at 24 weeks, with this increase sustained at 48 weeks, whereas no significant change was observed in PHA-induced RANTES production. A significant positive correlation was found between the changes in PHA-induced chemokine production and baseline CD4+ T cell counts. These data demonstrate that sustained suppression of viral replication by potent antiretroviral therapy has a potentially beneficial effect on chemokine production and early initiation of this therapy appears to confer a more favorable chemokine profile.

Anti-HIV Agents↗
PubMed1999

Cloning of rat fibrillin-2 cDNA and its role in branching morphogenesis of embryonic lung.

Fibrillin-2 is an extracellular matrix protein. It is associated with elastic fibers in several tissues and is believed to serve as a ligand for alphavbeta3 integrin, the latter being a known morphogen. In this study, the role of fibrillin-2 in lung development was investigated. Also, rat fibrillin-2 cDNA was isolated and sequenced and its spatiotemporal expression determined. It had approximately 88% homology with human fibrillin-2 and had Ca(2+) binding epidermal growth factor-like domains, transforming growth factor-beta binding protein motifs, and two RGD binding sites. Northern blot analysis revealed an approximately 10-kb transcript, and fibrillin-2 expression was developmentally regulated, and it paralleled that of tropoelastin. At day 13 of gestation, fibrillin-2 was expressed in the mesenchyme and at the epithelial:mesenchymal interface. From day 13 to 19 of gestation, its expression intensified and was confined around the tracheobronchial airways, while it lessened during the postnatal period. Immunoprecipitation revealed an approximately 350-kDa band by SDS-PAGE. Treatment with fibrillin-2 antisense oligodeoxynucleotide induced dysmorphogenesis of the lung explants. They were smaller and had rudimentary lung bud branches, collapsed conducting airways, and loose expanded mesenchyme. Concomitantly, fibrillin-2 mRNA, antibody reactivity in the explants, and fibrillin-2-specific radioincorporation were reduced. Anti-alphav and -laminin antibody reactivity and their respective incorporated specific radioactivities were unaltered. These data indicate that fibrillin-2 modulates organogenesis of the lung in the context of epithelial:mesenchymal interactions. Conceivably, the collapse of the conducting airways may also be related to the perturbed biology of the fibrillin-2 interacting protein, i.e., elastin, the latter being critical for the normal biophysiology of the lungs.

Actins↗
PubMed1999

Interferon-gamma inhibits CD44-hyaluronan interactions in normal human B lymphocytes.

The interaction of CD44 with its ligand hyaluronan (HA) plays a vital role in lymphopoiesis, lymphocyte homing, T cell activation, and metastasis. This study addresses the effect of cytokines involved in B cell growth on CD44-HA interactions in normal human B cells. Activation of B lymphocytes with LPS, pokeweed mitogen, or anti-IgM antibodies with or without IL-2 or IL-4 failed to induce HA adhesion. Stimulation of B cells with the phorbol ester PMA, however, induced strong HA recognition, which was inhibited by IFN-gamma and to some extent by IL-4. Investigation of the potential molecular mechanism involved revealed that PMA-induced HA adhesion correlated with enhanced expression of CD44-H- and V6-containing isoforms, as determined by flow cytometry, and the differential induction of V4- and V5-containing isoforms, as determined by reverse transcriptase-based polymerase chain reaction analysis. The inhibition of PMA-induced adhesion by IFN-gamma and IL-4 correlated with the downregulation of CD44 H expression and altered usage of exons V4 and V5. However, changes in the electrophoretic mobility of CD44 proteins, as a measure of posttranslational modifications, were not detected in response to PMA and IFN-gamma or PMA and IL-4. These results suggest that the inhibition of PMA-induced HA adhesion by IFN-gamma and IL-4 may influence B cell migration through their ability to downregulate CD44-HA interactions.

B-Lymphocytes↗
PubMed1999

Beta-sheet breaker peptide inhibitor of Alzheimer's amyloidogenesis with increased blood-brain barrier permeability and resistance to proteolytic degradation in plasma.

Short synthetic peptides homologous to the central region of Abeta but bearing proline residues as beta-sheet blockers have been shown in vitro to bind to Abeta with high affinity, partially inhibit Abeta fibrillogenesis, and redissolve preformed fibrils. While short peptides have been used extensively as therapeutic drugs in medicine, two important problems associated with their use in central nervous system diseases have to be addressed: (a) rapid proteolytic degradation in plasma, and (b) poor blood-brain barrier (BBB) permeability. Recently, we have demonstrated that the covalent modification of proteins with the naturally occurring polyamines significantly increases their permeability at the BBB. We have extended this technology to iAbeta11, an 11-residue beta-sheet breaker peptide that inhibits Abeta fibrillogenesis, by covalently modifying this peptide with the polyamine, putrescine (PUT), and evaluating its plasma pharmacokinetics and BBB permeability. After a single intravenous bolus injection in rats, both 125I-YiAbeta11 and 125I-PUT-YiAbeta11 showed rapid degradation in plasma as determined by trichloroacetic acid (TCA) precipitation and paper chromatography. By switching to the all D-enantiomers of YiAbeta11 and PUT-YiAbeta11, significant protection from degradation by proteases in rat plasma was obtained with only 1.9% and 5.7% degradation at 15 min after intravenous bolus injection, respectively. The permeability coefficient x surface area product at the BBB was five- sevenfold higher in the cortex and hippocampus for the 125I-PUT-D-YiAbeta11 compared to the 125I-D-YiAbeta11, with no significant difference in the residual plasma volume. In vitro assays showed that PUT-D-YiAbeta11 retains its ability to partially inhibit Abeta fibrillogenesis and dissolve preformed amyloid fibrils. Because of its five- to sevenfold increase in permeability at the BBB and its resistance to proteolysis in the plasma, this polyamine-modified beta-sheet breaker peptide may prove to be an effective inhibitor of amyloidogenesis in vivo and, hence, an important therapy for Alzheimer's disease.

Alzheimer Disease↗
PubMed1999

Regulation of CD44-hyaluronan interactions in Burkitt's lymphoma and Epstein-Barr virus-transformed lymphoblastoid B cells by PMA and interleukin-4.

In this study, we investigated the regulation of CD44-hyaluronan (HA) interactions in a panel of EBV+ Burkitt's lymphoma (BL) and lymphoblastoid B cell lines (B-LCL) generated by in vitro EBV transformation of normal human B cells. The results show that among B cell mitogens, phorbol 12-myristate 13-acetate (PMA) alone induced strong HA recognition in EBV+ BL-30/B95-8 cells. Among the cytokines that affect B cell growth and differentiation, IL-4 alone induced HA recognition in BL-30/B95-8 cells. Attempts to delineate the molecular mechanism for this increased HA adhesion in BL-30/B95-8 cells revealed an enhanced expression of CD44 H, isoforms containing V3, V6, and V9 exons, alterations in the splicing pattern of the V4 exon, and the increased electrophoretic mobility of the CD44 H protein. In contrast, the ability to recognize HA was not observed in B-LCL cells stimulated with either PMA or IL-4, even though these cells respond to IL-4, as observed by upregulation of CD23 expression. The molecular pathways that regulate CD44 expression and CD44-mediated HA binding may be selectively inactivated in B-LCL cells. These results may have implications with respect to the generation and spread of B cell tumors.

B-Lymphocytes↗
PubMed1999

Prostatic human kallikrein 2 inactivates and complexes with plasminogen activator inhibitor-1.

Human kallikrein 2 (hK2) is a serine protease expressed predominantly in the prostate which has 80% homology to prostate-specific antigen (PSA). hK2 is an active trypsin-like protease which has been shown by immuno-histochemical staining to be more highly expressed in prostate carcinoma than in benign prostate tissue. Unlike PSA, hK2 activates pro-PSA , pro-hK2 and the zymogen form of urokinase-type plasminogen activator (uPA), an extracellular protease correlated with prostate cancer and metastasis. We show here that hK2 rapidly forms a complex with plasminogen activator inhibitor-1 (PAI-1), the primary inhibitor of uPA in tissues. In addition, hK2 inactivated 6 to 7 mol of PAI-1 by cleavage at Arg346-Met347 for every mole of hK2-PAI-1 complex formed. In contrast with hK2, PSA neither complexed with nor inactivated PAI-1. PAI-1 inhibited hK2 comparably with protein C inhibitor (PCI) and at least 20 times more rapidly than alpha1-anti-chymotrypsin (ACT). N-Terminal sequencing shows that hK2 forms a covalent complex with PAI-1, PCI and ACT after cleavage at Arg346-Met347, Arg354-Ser355 and Leu358-Ser359, respectively. During complex formation, hK2 inactivated PAI-1 but did not inactivate ACT or PCI. Our current results suggest that the increased hK2 expression in prostate cancer tissues could influence cancer biology not only by activation of uPA but also by inactivation of its primary inhibitor, PAI-1.

Humans↗
PubMed1999

Do we have a less severe form of Kawasaki disease or is it the gammaglobulin effect?

This study was undertaken to evaluate the incidence of coronary artery aneurysms (CAA) in Kawasaki disease (KD). We reviewed the clinical and echocardiographic findings of 135 children who presented to our center with KD between December 1986 and December 1997. The age of onset ranged between 3months to 13 years (median 2 years). The male to female ratio was 1.54:1. All patients received intravenous Gammaglobulin (IVGG) during the acute stage. The echocardiogram, which was done between 2-3 weeks of the onset of fever, was normal in 106 patients (78.5%). Follow-up studies over a period of 6 months to 1 year remained normal. Minimal right or left coronary artery wall ectasia without dilatation or aneurysm formation was seen in 16 (11.85%). Follow-up of these patients showed disappearance of these changes over 6 weeks to 6 months. One patient (0.74%) had generalised dilatation of all the coronary arteries during the acute stage. This has normalized over a period of 9 months. A total of 10 (7.4%) had CAA during the acute stage. On follow-up of 8 of these patients for an average 3 months to 1.5 years all CAA regressed completely. One patient had residual Giant CAA after 1 year follow-up. One patient with CAA was lost to follow-up. One patient (0.74%) had pericardial effusion and another one (0.74%) had mitral incompetence during the acute stage only, both had no coronary involvement. None of our patients had cardiac failure, arrhythmia, myocardial infarction or death. We conclude that coronary artery changes due to KD are less common and less severe in our patients than those seen in other studies. We speculate that this can be related partly to the early administration of IVGG. The difference in incidence of CAA secondary to KD among different racial groups warrants more detailed genetic studies.

Adolescent↗
PubMed1999

Recombinant soluble form of PSGL-1 accelerates thrombolysis and prevents reocclusion in a porcine model.

BACKGROUND: We investigated whether administration of a soluble recombinant P-selectin glycoprotein ligand-1 chimera (rPSGL-Ig) in conjunction with thrombolytic therapy would enhance thrombolysis by preventing ongoing interactions of leukocytes with platelets and the injured arterial wall. METHODS AND RESULTS: An occlusive thrombus was formed in an internal iliac artery of Yorkshire pigs by placement of a copper coil in the artery under fluoroscopic guidance. Pigs then received heparin and, 15 minutes later, either vehicle or rPSGL-Ig followed by infusion with 25 mg tissue plasminogen activator according to the 90-minute regimen. Blood flow through the artery was monitored by angiography and scored on a scale of 0 to 3. Lysis of the thrombus was accelerated by 70% in pigs treated with rPSGL-Ig 250 microg/kg compared with control (13.3+/-5.0 versus 44. 4+/-13.3 minutes; n=9 each). Eight of 9 control pigs reoccluded in 13.8+/-16.9 minutes after the end of tissue plasminogen activator infusion, whereas no reocclusion was observed in 8 of 9 pigs in the rPSGL-Ig group. When the dose of rPSGL-Ig was increased to 500 microg/kg, time to lysis was shortened by 61% from control (18.0+/-8. 4 versus 46.0+/-8.9 minutes). Reocclusion occurred in 6.0+/-15.2 minutes in control but not in any rPSGL-Ig-treated pig (n=5 each). In addition, near-normal flow (score 2 or 3) after thrombolysis was achieved 59% and 58% faster in the 2 rPSGL-Ig groups than in their respective controls. CONCLUSIONS: Inhibition of leukocyte accumulation at the site of thrombosis with rPSGL-Ig may represent a safe therapeutic intervention that could be important in accelerating thrombolysis, achieving optimal reperfusion, and reducing incidence of acute reocclusion.

Animals↗
PubMed1999

Orphan receptor Arp-1 binds to the nucleotide sequence located between TATA box and transcriptional initiation site of the human angiotensinogen gene and reduces estrogen induced promoter activity.

Human angiotensinogen gene contains a C/A polymorphism at 20 bases upstream from the transcriptional initiation site. This sequence binds to the estrogen receptor when nucleoside A is present at this site and reporter constructs containing human angiotensinogen gene promoter with nucleoside A at -20 are transactivated on co-transfection of estrogen receptor in HepG2 cells followed by estrogen treatment. We show here that orphan receptor, Arp-1, which belongs to the COUP family of transcription factors also binds to this sequence. Co-transfection of Arp-1 reduces estrogen induced promoter activity of reporter constructs containing human angiotensinogen gene promoter. On the other hand co-transfection of Arp-1 does not have a significant effect on estrogen induced promoter activity of reporter constructs containing rat angiotensinogen gene promoter. Our data suggests that human and rat angiotensinogen genes are regulated in a different manner by estrogens.

Angiotensinogen↗
PubMed1999

Outcome of twin pregnancy in a renal transplant recipient treated with tacrolimus.

Our report describes the outcome of a twin pregnancy in a woman who was maintained on tacrolimus after a living related renal transplant. Both babies born at 32 weeks of gestation developed severe respiratory distress requiring ventilator assistance and went on to develop congestive heart failure. Echocardiograms on both babies showed dilated heart chambers. Twin A succumbed to complications, but twin B, who was treated more aggressively with vasopressors, recovered. Autopsy findings on twin A revealed a thrombotic cardiomyopathy with degeneration of cardiac muscle. We believe that the unusual outcome in this set of twins may have been a result of cardiomyopathy secondary to tacrolimus used by the mother during her pregnancy.

Azathioprine↗
PubMed1999

Modulatory potential of Spirulina fusiformis on carcinogen metabolizing enzymes in Swiss albino mice.

The modulatory potential of Spirulina fusiformis was observed on the hepatic and extrahepatic carcinogen metabolizing enzymes in Swiss albino mice at a dose of 800 mg/kg b.w. given orally. A significant reduction in the hepatic cytochrome P-450 content was observed in the group treated with Spirulina in comparison with the control group. The hepatic glutathione S-transferase activity was induced significantly by Spirulina treatment. There was no change in the extrahepatic glutathione S-transferase activity after the animals were fed with Spirulina.

Animals↗