Biomedical subjects

S Kotecha

Publications and source records attributed to S Kotecha.

44 records · Page 3Linked to original sources

PubMed1994

Pharmacological modulation of platelet-derived growth factor (B) mRNA expression in alveolar macrophages and adherent monocytes.

The macrophage profibrotic cytokine, Platelet Derived Growth Factor B [PDGF(B)], is thought to play a central role in orchestrating the fibrotic response in the pathogenesis of cryptogenic fibrosing alveolitis. In this study, we have asked if drugs that increase intracellular cAMP and are commonly administered to patients with lung disease have the ability to downregulate PDGF(B) mRNA. Incubation of human alveolar macrophages from healthy smokers in the presence of dibutyryl cAMP prevented the previously reported dexamethasone-induced increase in PDGF(B) mRNA (P < 0.05). Similarly, the combination of aminophylline (2.5 mM) and salbutamol (1 microM) prevented the adherence-dependent increase in PDGF(B) mRNA in adherent human peripheral blood monocytes (P < 0.05), whilst causing an increase in the mRNA expression of the cAMP-dependent gene c-fos (P = 0.059), and an increase in the intracellular concentration of cAMP (P = 0.05). Finally, the presence of a lower concentration of aminophylline (0.25 m) in conjunction with salbutamol (1 microM) also prevented the dexamethasone-induced increase in PDGF(B) mRNA in alveolar macrophages from healthy smokers (P < 0.05). Stimulation by these drugs was not associated with a change in the abundance of the mRNA of the house-keeping gene, glyceraldehyde-3-phosphate dehydrogenase. We speculate that drugs, which increase intracellular cAMP, may provide a novel therapeutic avenue whereby PDGF(B) expression in patients with cryptogenic fibrosing alveolitis may be reduced.

Base Sequence↗

PubMed1994

Molecular characterization of Xenopus laevis DP proteins.

It is widely believed that in mammalian cells the cellular transcription factor (DRTF1/E2F integrates cell-cycle events with the transcription apparatus by interacting with important regulators of the cell cycle, such as the retinoblastoma gene product (pRb) and related proteins, cyclins, and cyclin-dependent kinases. Here, we have defined DRTF1/E2F in Xenopus laevis that, like its mammalian counterpart, specifically binds to the E2F site, is regulated during development, and interacts with pRb and related proteins. We have isolated cDNAs that encode the functional homologue of mammalian DP-1, X1 DP-1, together with a close relative, X1 DP-2. X1 DP-1, which is highly conserved with murine DP-1, is a major DNA binding component of X1 DRTF1/E2F. Both DP-1 and DP-2 synergistically interact with members of the E2F family of proteins, E2F-1, E2F-2, and E2F-3, to generate DNA binding complexes that specifically recognize the E2F site and functionally interact with E2F-1 in E2F site-dependent transcriptional activation of cellular genes. DP-1 and DP-2 encode maternally stored transcripts that are expressed during early development. In the adult however, the expression of DP-1 and DP-2 is tissue restricted. This study therefore defines a new family of transcription factors, the DP proteins, members of which can interact combinatorially with E2F proteins to generate an array of DNA binding complexes that integrate cell-cycle progression with the transcription apparatus through the E2F binding site. The tissue-specific expression of DP family members suggests that the combination of DP/E2F heterodimers that constitute DRTF1/E2F is influenced by the phenotype of the cell.

Amino Acid Sequence↗

PubMed1994

Platelet-derived growth factor-beta mRNA in human alveolar macrophages in vivo in asthma.

Collagen deposition and myofibroblast proliferation beneath the epithelial basement membrane in patients with asthma is now increasingly recognized, although the molecular pathogenesis remains obscure. We have evaluated messenger ribonucleic acid (mRNA) expression of the profibrotic cytokine, platelet-derived growth factor-beta (PDGF-beta), in alveolar macrophages obtained following fibreoptic bronchoscopy and bronchoalveolar lavage in patients with asthma. Three subject groups were studied: 1) asthmatics using regular inhaled glucocorticoid medication (ASTST, n = 9), 2) asthmatics using intermittent inhaled beta 2-agonist therapy only (ASTBR, n = 10); 3) nonasthmatic control volunteers (n = 10). Alveolar macrophage mRNA was extracted and PDGF-beta mRNA quantified by reverse-transcriptase polymerase chain reaction (PCR) (RT-PCR) and expressed as the ratio to that of a control gene glyceraldehyde-3-phosphate dehydrogenase (GAPDH). There were no significant differences in PDGF-beta mRNA expression between the groups, or between all asthmatic (n = 19) and control subjects. Furthermore, there was no correlation between alveolar macrophage PDGF-beta mRNA expression and airway spirometry, or duration of glucocorticoid usage or dose. Thus, in contrast to other fibrotic lung diseases, we found little evidence of enhanced expression of PDGF-beta mRNA in alveolar macrophages in clinically stable bronchial asthma.

Adult↗

PubMed1993

Pharmacological modulation of c-fos mRNA expression in the HL60 and U937 cell lines.

A variety of drugs known to act via increasing intracellular cAMP are used in the treatment of asthma. In this study we asked whether anti-asthma drugs are capable of altering gene activation. We determined whether phosphodiesterase inhibitors, either alone or in combination with adrenoceptor agonists, were able to alter the abundance of mRNA of the cAMP responsive gene c-fos in the cell-lines HL60 and U937. Incubation of cells with phosphodiesterase inhibitors aminophylline, theophylline or pentoxyphylline all resulted in an increase in c-fos mRNA. Further upregulation of c-fos mRNA abundance was observed when the cells were stimulated with the combination of aminophylline and adrenoceptor agonists with beta 2-agonist activity. These increases in c-fos mRNA were accompanied by increases in intracellular concentration of cAMP. These data suggest that in these in vitro models, combinations of beta 2-adrenoceptor agonists and phosphodiesterase inhibitors can increase intracellular cAMP and affect gene activation.

Adrenergic beta-Agonists↗

PubMed1992

Muscle-specific expression of SRF-related genes in the early embryo of Xenopus laevis.

We have isolated two members of the RSRF protein family, SL-1 and SL-2, in Xenopus laevis. Both proteins contain SRF-type DNA binding domains and are related to the human protein, RSRFC4. SL-1 constitutes a novel member of the RSRF family whilst SL-2 is similar to human RSRFC4 throughout its length. SL-1 protein recognizes the consensus DNA sequence CTA(A/T)4TAR in vitro and can bind to the same regulatory sites as other A/T-rich sequence-specific binding activities, such as the muscle-specific regulatory factor, MEF-2. Transcription of both Xenopus genes is restricted to the somitic mesoderm of early embryos and subsequently to the body muscle (myotomes) of the tadpole. In contrast, both genes are expressed ubiquitously in the adult frog. A binding activity, antigenically related to both human RSRFC4 and the SL-2 gene product, is detected in Xenopus embryos and after gastrulation is localized to embryonic muscle. An indistinguishable binding activity is detected in many adult frog tissues. We conclude that the RSRF genes undergo a dramatic switch in their patterns of expression during development. We suggest that RSRF proteins may regulate muscle-specific transcription in embryos, but acquire other roles during the course of development.

Amino Acid Sequence↗

PubMed1988

Dietary and other characteristics relevant for coronary heart disease in men of Indian, West Indian and European descent in London.

The origins of the high standardized mortality ratio (SMR) for coronary heart disease (CHD) among Indians in Britain, and the low SMR for West Indian immigrants, have been explored by a community survey in London. Serum lipoproteins, plasma glucose, haemostatic factors and other putative risk characteristics were measured in 75 Indian, 64 European and 24 West Indian men aged 45-54 years. These represented 81% of men registered with a general practice and resident within a defined area. In 51 men, diet was assessed by 5-day weighed inventory. Plasma phospholipid fatty acids (PFA) were measured in 18 Indians and 19 Europeans with dietary records. The relatively high HDL and HDL2-cholesterol concentrations, low LDL-cholesterol concentration, reduced fat intake, increased ratio of dietary polyunsaturated/saturated fat, relatively frequent use of alcohol, and lack of obesity in West Indians accorded with their low SMR from CHD. By contrast, only the relatively low HDL and HDL2-cholesterol concentrations, infrequency of alcohol consumption, and lower proportion of PFA as n-3 fatty acids of marine origin afforded explanations for the high SMR of Indians. Hyperglycaemia appeared similarly prevalent in Indians and West Indians, but less common in Europeans. Of the haemostatic factors, West Indians had a relatively low VIIc (not statistically significant), while Indians had an increased platelet count and reduced platelet volume. Improved understanding of these ethnic differences in CHD mortality may depend upon elucidation of the contrasts in HDL-cholesterol concentration.

Blood Coagulation Tests↗

PubMed1986

Measurement of glycosylated haemoglobins and glycosylated plasma proteins in animal models with diabetes or inappropriate hypoglycaemia.

Stable glycosylated haemoglobins and glycosylated plasma proteins were determined by affinity chromatography using Glycogel B in animal models with diabetes or inappropriate hypoglycaemia. Adult Aston ob/ob mice and C57BL/KsJ db/db mice exhibited 1.5-1.9 fold increases of body weight, 2.5-3.4 fold elevations of plasma glucose and 20.9-29.3 fold elevations of plasma insulin. Glycosylated haemoglobins and glycosylated plasma proteins were raised 7.2-8.2 fold and 6.6-6.7 fold respectively. In adult NEDH rats, administration of streptozotocin or implantation of transplantable insulinoma fragments produced reciprocal changes in insulin and glucose concentrations either resulting in the onset of insulin deficiency (5.9 fold decrease) and hyperglycaemia (3.2 fold increase) by 2 days, or hyperinsulinaemia (2.1 fold increase) and hypoglycaemia (1.4 fold decrease) by 6 and 8 days, respectively. Glycosylated plasma proteins were increased (1.2 fold) rapidly after streptozotocin treatment followed by glycosylated haemoglobins (1.6 fold increase) after 8 days. In contrast, the decreases in glycosylated plasma proteins and glycosylated haemoglobins (4.4 fold and 1.4 fold, respectively) in insulinoma-bearing rats preceded the demonstration of hypoglycaemia by 5 and 2 days, respectively. Glycosylated plasma proteins in insulinoma-bearing rats returned to pretransplantation values at 10-16 days. Good correlations were observed in mice and rats between glucose and both glycosylated haemoglobins (r = 0.92 and r = 0.90, respectively) and glycosylated plasma proteins (r = 0.85 and r = 0.93), and between the glycosylated blood proteins themselves (r = 0.95 and r = 0.91). The results show that the measurement of glycosylated blood proteins by affinity chromatography using Glycogel B provides a sensitive and reliable indicator of the recent glycaemic environment.

Animals↗

PubMed1980

Resistance of the peptidyltransferase centre of rabbit ribosomes to attack by nucleases and proteinases.

Larger ribosomal subparticles (L-subparticles) of rabbit ribosomes were treated with either ribonucleases (I or T1) or proteinases (trypsin or chymotrypsin), and their capacity to function in poly(U)-directed polyphenylalanine synthesis and in the puromycin reaction was investigated. The effects of pretreatment of L-subparticles on the reconstruction of active subparticles from core-particles derived by treatment with 2.75 M-NH4Cl/69 mM-MgCl2 and split-protein fractions were also examined. The protein moiety of proteinase-treated L-subparticles was analysed by one-dimensional sodium dodecyl sulphate/polyacrylamide- and two-dimensional polyacrylamide-gel electrophoresis. The introduction of 16--100 scissions in the RNA moiety had no effect on the activity of the L-subparticles in polyphenylalanine synthesis, and there was no effect on the stability of L-subparticles to high-salt shock treatment and a marginal effect on the reconstruction of L-subparticles from high-salt-shock core-particles and split-protein fractions. In contrast, L-subparticles treated with low amounts of trypsin (0.56 ng of trypsin/microgram of L-subparticle) were inactive in polyphenylalanine synthesis, and their capacity to function in partial-reconstruction experiments was diminished. Activity in the puromycin reaction was increased by 70% as a result of trypsin treatment (280 ng of trypsin/microgram of L-subparticle). At least two of the acidic proteins implicated in the translocation function were not affected by trypsin treatment. Trypsin-treated L-subparticles had lost their capacity to bind the smaller ribosomal subparticle (S-subparticle). The protein(s) needed for S-subparticle binding were shown to be present in high-salt-shock cores. At least six proteins associated with the core-particles were attack during trypsin treatment of L-subparticles. An examination of L-subparticles isolated from trypsin-treated polyribosomes showed that the amount of trypsin necessary to decrease the activity of the subparticle by 50% was about twice that needed in the treatment of L-subparticles alone. The largest protein of rabbit L-subparticles (approx. 51 000 daltons) was cleaved in a stepwise fashion by trypsin to fragments of approx. 40 000 daltons. This protein was also cleaved by chymotrypsin.

Acyltransferases↗