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Biomedical subjects

S Ghosh

Publications and source records attributed to S Ghosh.

At least 559 records · Page 31Linked to original sources
PubMed1995

Identification of a 148-kDa surface lectin from Giardia lamblia with specificity for alpha-methyl-D-mannoside.

A lectin specific for alpha-methyl-D-mannoside was purified from the membrane extract of Giardia lamblia by a combination of gel filtration chromatography on Sephadex G-75 and Superose 6-HR 10/30. The homogeneity of the lectin was established by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The molecular mass of the native protein was 148 kDa. The lectin agglutinated rabbit erythrocytes in the presence of Ca2+ at 37 degrees C and pH 7.0. The maximum activity of the lectin was obtained after trypsin treatment. The inhibition study clearly suggests that the binding site of the lectin recognizes alpha-methyl-D-mannoside as the immunodominant sugar.

Animals↗
PubMed1995

Molecular cloning and sequence analysis of a seed-expressed acyl carrier protein (ACP) gene from Brassica campestris (Agrani).

We describe here the nucleotide sequence of the Brassica campestris ACPSF1 gene which encodes a seed-expressed acyl carrier protein (ACP). The 3600 bp sequence consists of 1740 bp upstream of the translation start codon, 828 bp spanning the coding region which is interrupted by three introns and 1032 bp downstream of the stop codon. Using a ACPSF1 gene-specific probe, transcripts could be detected in developing seeds, but not in leaves. The gene is now the only known member that represents group I seed-expressed ACP multigene family of Brassica species. The 5' flanking sequence of the ACPSF1 gene was examined for putative transcriptional regulatory elements. A sequence alignment of the 5' flanking regions of the available seed-expressed ACP genes of Brassica species showed some conserved regions which might have some common regulatory significance.

Acyl Carrier Protein↗
PubMed1995

Embryonic lethality and liver degeneration in mice lacking the RelA component of NF-kappa B.

NF-kappa B, which consists of two polypeptides, p50 (M(r) 50K) and p65/RelA (M(r) 65K), is thought to be a key regulator of genes involved in responses to infection, inflammation and stress. Indeed, although developmentally normal, mice deficient in p50 display functional defects in immune responses. Here we describe the generation of mice deficient in the RelA subunit of NF-kappa B. Disruption of the relA locus leads to embryonic lethality at 15-16 days of gestation, concomitant with a massive degeneration of the liver by programmed cell death or apoptosis. Embryonic fibroblasts from RelA-deficient mice are defective in the tumour necrosis factor (TNF)-mediated induction of messenger RNAs for I kappa B alpha and granulocyte/macrophage colony stimulating factor (GM-CSF), although basal levels of these transcripts are unaltered. These results indicate that RelA controls inducible, but not basal, transcription in NF-kappa B-regulated pathways.

Animals↗
PubMed1995

Renal and hepatic family 3A cytochromes P450 (CYP3A) in spontaneously hypertensive rats.

Troleandomycin (TAO), a selective family 3A cytochromes P450 (CYP3A) inhibitor, decreases enhanced in vivo corticosterone 6 beta-hydroxylation and blood pressure in spontaneously hypertensive rats (SHR). Corticosterone 6 beta-hydroxylation was measured in liver and kidney microsomes, to determine ontogeny and the effect of TAO on CYP3A activity at the organ level. SHR kidney CYP3A activity increased from 4 to 8 weeks, stabilized at 11 and 16 weeks, and was much higher than in control (Wistar-Kyoto, WKY) rats at all ages. Hepatic activity showed less consistency in strain difference. TAO produced a relatively large decrease in renal CYP3A activity compared with liver. Although renal CYP3A mRNA was not present in sufficient quantity for detection by northern blot analysis of total RNA, its presence was demonstrated in SHR by reverse transcriptase-polymerase chain reaction amplification. Correlations between renal CYP3A activity and systolic blood pressure in SHR and WKY rats with variations in age, strain and drug treatment are consistent with the role of the enzyme in the pathogenesis of blood pressure elevation in SHR.

Animals↗
PubMed1995

Photo-effect in phospholipid liposome containing riboflavin.

The photovoltage developed in a photoelectrochemical cell consisting of riboflavin (RFN), a neutral dye and phospholipid (PL) liposome in aqueous solution has been found to correlate with the Stern-Volmer constant (KSV) or quenching-rate constant (Kq) of RFN-PL studied by fluorescence spectra. A possible mechanisms of photovoltage generation suggests the photo-induced electron transfer from PL to RFN in liposome through the excited state molecular interaction.

Kinetics↗
PubMed1995

Two distinct Raf domains mediate interaction with Ras.

A key event for Ras transformation involves the direct physical association between Ras and the Raf-1 kinase. This interaction promotes both Raf translocation to the plasma membrane and activation of Raf kinase activity. Although substantial experimental evidence has demonstrated that Raf residues 51-131 alone are sufficient for Ras binding, conflicting observations have suggested that the Raf cysteine-rich domain (residues 139-184) may also be important for interaction with Ras. To clarify the role of the Raf cysteine-rich domain in Ras-Raf binding, we have compared the ability of two distinct Raf fragments to interact with Ras using both in vitro Ras binding and in vivo Ras inhibition assays. First, we determined that both Raf sequences 2-140 and 139-186 (designated Raf-Cys) showed preferential binding to active, GTP-bound Ras in vitro. Second, we observed that Raf-Cys antagonized oncogenic Ras(Q61L)-mediated transactivation of Ras-responsive elements and focus-forming activity in NIH 3T3 cells and insulin-induced germinal vesicle breakdown in Xenopus laevis oocytes in vivo. This inhibitory activity suggests that Raf-Cys can interact with Ras in vivo. Taken together, these results suggest that Ras interaction with two distinct domains of Raf-1 may be important in Ras-mediated activation of Raf kinase activity.

3T3 Cells↗
PubMed1995

Mitochondrial VDAC can be phosphorylated by cyclic AMP-dependent protein kinase.

The voltage dependent anion channel (VDAC) of the outer membrane of mitochondria is thought to play a role in transport of metabolites including ATP across mitochondrial membrane and modulate mitochondrial functions such as respiration. However, regulation of this anion channel is only poorly understood. In this paper we demonstrate that VDAC purified from rat liver mitochondria can be phosphorylated by the catalytic subunit of cAMP dependent protein kinase (PKA). PKA phosphorylates VDAC linearly up to fifteenfold in sixty minutes. The level of VDAC phosphorylation increases to twofold and sevenfold of control value after ten and thirty minutes of reaction, respectively. Data presented here suggest the possibility that voltage dependent anion channel of the outer membrane of mitochondria may be a target of PKA in vivo.

Animals↗
PubMed1995

I kappa B-beta regulates the persistent response in a biphasic activation of NF-kappa B.

We have cloned the cDNA encoding I kappa B-beta, one of the two major I kappa B isoforms in mammalian cells. The recombinant I kappa B- beta protein interacts with equal affinity to p65 and c-Rel and does not exhibit a preference between these Rel proteins. Instead the primary difference between I kapp B-alpha and I kappa B-beta is in their response to different inducers of NF-kappa B activity. One class of inducers causes rapid but transient activation of NF-kappa B by primarily affecting I kappa B-alpha complexes, whereas another class of inducers causes persistent activation of NF-kapa B by affecting both I kappa B-alpha and I kappa B-beta complexes. Therefore, the overall activation of NF-kappa B consists of two overlapping phases, a transient phase mediated through I kappa B-alpha and a persistent phase mediated through I kappa B-beta.

Amino Acid Sequence↗
PubMed1995

Structure of NF-kappa B p50 homodimer bound to a kappa B site.

The 2.3-A crystal structure of the transcription factor NK-kappa B p50 homodimer bound to a palindromic kappa B site reveals that the Rel homology region folds into two distinct domains, similar to those in the immunoglobulin superfamily. The p50 dimer envelopes an undistorted B-DNA helix, making specific contacts along the 10-base-pair kappa B recognition site mainly through loops connecting secondary structure elements in both domains. The carboxy-terminal domains form a dimerization interface between beta-sheets using residues that are strongly conserved in the Rel family.

Amino Acid Sequence↗
PubMed1995

Epidemiologic study of diet and coronary risk factors in relation to central obesity and insulin levels in rural and urban populations of north India.

In a population survey of 162 rural and 152 urban subjects aged 26-65 years at Moradabad, the findings are compared with existing data on Indian immigrants to Britain and United States. In comparison with rural subjects, urban subjects had a higher prevalence of coronary artery disease (8.6 vs. 3.0%) and diabetes (7.9 vs 2.5%), higher blood pressures, total and low density lipoprotein cholesterol, triglycerides and postprandial 2-h blood glucose and plasma insulin similar to observations made in UK in immigrants compared to Europeans. Fasting plasma insulin and high density lipoprotein cholesterol levels in urban subjects were comparable with rural subjects. Mean body weights were significantly higher in urban women, but not in men, than in rural subjects. However the body mass index (22.9 +/- 4.2 vs. 21.6 +/- 2.4 kg/m2) and waist-hip girth ratio (0.89 +/- 0.10 vs. 0.86 +/- 0.07) were significantly higher in urban men compared to rural men without such differences in women. Underlying these differences in risk factors, urban subjects had three times better socioeconomic status than rural subjects and were eating higher total and saturated fat, cholesterol and refined carbohydrates and lower total and complex carbohydrates compared to rural men and women. Energy expenditure during routine and spare time physical activity was significantly higher in rural compared to urban subjects. Those patients who had risk factors, showed lesser physical activity and had greater adverse factors in the diet compared to subjects without risk factors. Body mass index and waist-hip girth ratio in patients with risk factors were significantly higher than in subjects without risk factors. The findings suggest that decreased consumption of total and saturated fat and increased physical activity may be useful for prevention of coronary artery disease among urbans as well as in immigrants.

Adult↗
PubMed1995

Relationships between solution thermodynamics and hydrogen-bond patterns of crystalline dialkylhydroxypyridone iron chelators and their formic acid solvates.

1,2-Dialkyl-3-hydroxy-4-pyridones (DAHPs) are iron chelators that are being considered for oral administration for the treatment of anemias. They form 1:1 solvates with formic acid (DAHP-F). The lower DAHP homologues, differing in the alkyl chain length in the 1- and/or 2-positions, have known crystal structures and hydrogen-bond patterns. The main objective of this work is to investigate the influences of the hydrogen-bond patterns and the position and chain length of the alkyl groups on the free energies, enthalpies and entropies of solvation of the nonsolvates in formic acid, and of desolvation of the solvates in water at 25 degrees C. The standard free energy changes for desolvation of the solvates in water and for solvation of the nonsolvates in formic acid differed for different alkyl chain lengths at the 2-position but not at the 1-position. In contrast, the calorimetric enthalpies and entropies of solvation fell into two distinct classes, depending on the hydrogen-bond patterns of the solvates: that is, compounds which form 18-membered hydrogen-bonded rings, and a compound that forms a 10-membered hydrogen-bonded ring. The equilibrium constants for solid-state solvation indicated an approximately twofold greater solvating tendency for the 2-ethyl DAHPs than for the 2-methyl DAHPs. The mass transfer coefficient for the aqueous dissolution of each solvate was usually lower than that for the corresponding nonsolvate. The results provide links between molecular structure, crystal structure, and solution properties among the DAHP series.

Alkylation↗
PubMed1995

Relationships between crystal structures, thermal properties, and solvate stability of dialkylhydroxypyridones and their formic acid solvates.

Four 1,2-dialkyl-3-hydroxy-4-pyridones (DAHPs), which are iron chelators potentially suitable for oral administration, and their formic acid solvates (DAHP-Fs) were examined in powder form by powder X-ray diffraction (PXD), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and hot-stage microscopy (HSM). The experimental PXD pattern of each DAHP-F is different from that of the corresponding DAHP, indicating different crystalline phases. The PXD patterns calculated from the published crystal structures closely resemble the corresponding PXD patterns determined experimentally, indicating that the powdered materials studied are structurally identical with the single crystals previously examined. The DAHPs have similar DSC profiles consisting of melting followed by vaporization. The DSC profiles of the DAHP-Fs share five common features: melting and desolvation of the solvate, crystallization of the nonsolvate, vaporization of the released formic acid, melting of the nonsolvate, and vaporization of the nonsolvate. The weight loss steps in TGA indicate that each DAHP-F contains 1 mol of formic acid/mol of DAHP. The threshold temperature for desolvation of each DAHP increases with decreasing length of the hydrogen bond between the pyridone carbonyl oxygen and the formic acid carboxyl proton, corresponding to an increase in solvate stability. Thus, the relative stabilities of the solvates are delineated and are related to the length of the hydrogen bond between the DAHP and the formic acid molecules.

Calorimetry, Differential Scanning↗