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Biomedical subjects

R Datta

Publications and source records attributed to R Datta.

At least 91 records · Page 5Linked to original sources
PubMed1990

Role of merocyanine dye as a proton pump in photovoltage generation.

A novel photoelectrochemical cell using a proton pump mechanism in the aggregated planar structure of oxidised cholesterol incorporating merocyanine dyes is reported. Lipid dye binding, as verified from spectral studies and photoisomerisation of the dye, is responsible for this photovoltage generation whose magnitude and storage duration are related to the equilibrium constant of dye-lipid binding through an empirical formula.

Biological Transport↗
PubMed1990

Transcriptional and posttranscriptional regulation of macrophage-specific colony stimulating factor gene expression by tumor necrosis factor. Involvement of arachidonic acid metabolites.

The effects of tumor necrosis factor (TNF) on the regulation of macrophage-specific colony stimulating factor (CSF-1) gene expression have been studied in HL-60 cells during monocytic differentiation. CSF-1 transcripts were undetectable in uninduced HL-60 cells, reached maximal levels by 3 h of exposure to TNF, and returned to that of control cells by 24 h. Transcriptional run-on analysis demonstrated that exposure to TNF stimulated the rate of CSF-1 gene transcription by 6.4-fold. The combination of a protein synthesis inhibitor, cycloheximide, and TNF increased levels of CSF-1 mRNA compared with treatment by TNF alone. We also studied the signal transduction mechanisms responsible for regulating TNF-induced CSF-1 mRNA levels. Both 4-bromophenacyl bromide and quinacrine, inhibitors of phospholipase A2 activity, blocked TNF-induced increases in CSF-1 transcripts in a concentration-dependent manner, while caffeic acid and nordihydroguaiaretic acid, inhibitors of the 5-lipoxygenase pathway, had no detectable effect on induction of CSF-1 RNA. PGE2 or dibutyryl cAMP treatment of HL-60 cells in the presence of TNF blocked the expression of CSF-1 mRNA in a dose-dependent manner. These findings suggest that the increase in CSF-1 RNA observed during TNF treatment is regulated, at least in part, by both transcriptional and posttranscriptional mechanisms, and that PGE2 and cAMP regulate transcriptional activation of the CSF-1 gene by TNF.

Acetophenones↗
PubMed1990

Induction of c-fos gene expression by arabinofuranosylcytosine in human KG-1 leukemia cells.

Previous studies have demonstrated that the c-fos proto-oncogene is expressed during induction of differentiation and as an immediate early response to growth factors. The present results demonstrate that exposure of human KG-1 myeloid leukemic cells to 1-beta-D-arabinofuranosylcytosine (ara-C) was associated with increases in c-fos gene expression. This effect was dependent on the concentration and time of ara-C treatment. The level of c-fos transcripts was maximal after 6 hr of exposure to 5 x 10(-6) M ara-C and subsequently declined to that in untreated cells. Nuclear run-on assays demonstrated low to undetectable levels of c-fos gene transcription in untreated KG-1 cells. In contrast, treatment with 5 x 10(-6) M ara-C for 6 hr was associated with increases in transcription of this gene. Although superinduction of c-fos expression has been observed at the post-transcriptional level in the presence of protein synthesis inhibition, this effect was not detectable in ara-C-treated KG-1 cells. These combined results demonstrate that ara-C increased c-fos mRNA levels in KG-1 cells and that this effect was associated with transcriptional activation of the c-fos gene.

Blotting, Northern↗
PubMed1990

Induction of monocytic differentiation by tumor necrosis factor in phorbol ester-resistant KG-1a cells.

Tumor necrosis factor (TNF) is a regulatory cytokine that has pleiotropic effects on hematopoietic cell growth and differentiation. The present studies have examined the effects of TNF on the differentiation of phorbol-ester resistant human KG-la leukemia cells. Treatment with 100 U/mL of TNF or 33 nM 12-O-tetradecanoylphorbol-13-acetate (TPA) had no detectable effect on the growth of KG-1a cells. In contrast, TNF, but not TPA, induced cellular aggregation and expression of the ICAM-1 adhesion molecule in KG-1a cells. Furthermore, KG-1a cells responded to TNF, but not to TPA, with a partial down-regulation of c-myc mRNA levels and induction of M-CSF gene transcription. Previous work suggested that TNF induces M-CSF gene expression through activation of phospholipase A2 and eicosanoid production. The present studies also demonstrate that TNF stimulated phospholipase A2 activity. In contrast, there was no detectable increase in phospholipase A2 activity following TPA treatment. These results indicate that: 1) certain characteristics of the differentiated monocytic phenotype were induced by TNF in the phorbol ester-resistant KG-1a line, and 2) treatment with TNF and not TPA was associated with activation of phospholipase A2 during induction of monocytic differentiation in these cells.

Blotting, Northern↗
PubMed1990

Regulation of jun-B gene expression by 1-beta-D-arabinofuranosyl-cytosine in human myeloid leukemia cells.

The jun-B gene is a member of the jun family of immediate early response genes that regulate cellular responses to growth factors. The present studies have examined the effects of 1-beta-D-arabinofuranosylcytosine (ara-C) on jun-B expression in human KG-1 myeloid leukemia cells. The results demonstrate that ara-C increases jun-B mRNA levels. The level of jun-B transcripts was maximal after 12 hr of exposure to 10(-5) M ara-C and persisted through 72 hr. Nuclear run-on assays demonstrated that ara-C treatment is associated with an increased rate of jun-B gene transcription. The results also demonstrate that ara-C-induced jun-B mRNA levels are regulated by a posttranscriptional mechanism. The level of jun-B transcripts in ara-C-treated cells was superinduced by inhibition of protein synthesis. Moreover, cycloheximide prolonged the half-life of ara-C-induced jun-B transcripts. These results, thus, demonstrate that ara-C induces expression of the jun-B gene in KG-1 cells and that this effect is mediated by transcriptional and posttranscriptional mechanisms.

Cycloheximide↗
PubMed1989

Enterically transmitted non-A, non-B hepatitis: recovery of virus-like particles from an epidemic in south Delhi and transmission studies in rhesus monkeys.

An epidemic of viral hepatitis, serologically characterized as due to non-A, non-B hepatitis, occurred in a village of South Delhi, India, in December, 1986, through January, 1987. Water contaminated with fecal matter was the apparent source of infection. Disease-associated virus-like particles were detected by immune electron microscopy in the feces of three patients within 5 days of illness. The virus-like particles were agglutinated by autologous acute-phase serum but not by convalescent serum. Rhesus monkeys inoculated with particle-containing fecal suspensions developed biochemical and morphologic features of acute, self-limited hepatitis. The findings in the present study and in earlier investigations of sporadic non-A, non-B hepatitis suggest that (i) the epidemic form and a proportion of sporadic cases of this infection in India may be related, both being enterically transmitted and associated with infection by a 27- to 32-nm virus-like particle, (ii) antibody responses to this virus occur early in disease and are transient and (iii) the rhesus monkey may prove to be a suitable model for studies of epidemic non-A, non-B hepatitis.

Adolescent↗
PubMed1988

Significance of maternal and infant serum antibodies to hepatitis B core antigen in hepatitis B virus infection of infancy.

The significance of IgM and IgG class antibodies to hepatitis B virus (HBV) core component (anti-HBc) was investigated in a study of maternal-fetal HBV transmission. An IgM anti-HBc response was lacking in the majority (49/53) of HBV-infected infants. This antibody thus cannot be used as an indicator of transplacental infection. However, most infants who became HBsAg positive during the first 6 months of life acquire infection in the perinatal period rather than transplacentally. Passively transferred maternal IgG anti-HBc in the infant and additional IgM anti-HBc positively in the carrier mother have no modulating influence on HBV infection of infants born to HBV carrier women.

Age Factors↗
PubMed1988

Adjuvant postoperative external beam radiotherapy in head and neck cancer.

The optimum postoperative dose for local or regional disease control was retrospectively assessed in 70 patients with head and neck cancer given adjuvant external beam radiotherapy. Actuarial 2-year survival rates with no evidence of disease (NED) according to stage were 75%, 59%, and 72% for stages II, III, and IV, respectively. Primary tumor/regional failure and distant metastasis adversely affected prognosis. Patients had an actuarial 2-year NED of 80% when the dose to the primary tumor/upper neck was greater than or equal to 60 Gy but was 53% when the dose was less than 60 Gy. Two-year NED was 85% in those patients given greater than 50 Gy to the lower neck and 62% when less than or equal to 50 Gy was used. Based on these results, a total dose of at least 60 Gy to the primary tumor bed and upper neck and greater than 50 Gy to the lower neck whenever adjuvant postoperative irradiation is administered for subclinical disease is recommended.

Adolescent↗
PubMed1987

Elective postoperative external radiotherapy after hysterectomy in early-stage carcinoma of the cervix. Is additional vaginal cuff irradiation necessary?

This retrospective study of 44 patients who received postoperative radiotherapy soon after hysterectomy for early Stage IB to IIA carcinoma of the cervix was undertaken to determine the need for additional vaginal cuff irradiation (AVCI) following external pelvic irradiation (EPI). The reasons for adjuvant radiotherapy administration were mostly the nonradical type of performed hysterectomy or the presence of adverse prognostic histopathologic features. The overall survival and local control rates were 80% (35/44) and 89% (39/44) at 2 years and 63% (26/41) and 80% (33/41) at 5 years, respectively. Although the 2-year results seemed to indicate that AVCI was necessary, this was not supported by the obtained longer term data. Moreover, it appeared that AVCI could perhaps be safely done after EPI, when occult early-stage cervical carcinoma was found after total abdominal hysterectomy. Data from this study and the literature concerning AVCI's appropriate role in this particular disease condition are discussed.

Carcinoma↗
PubMed1985

Modulation of acetone-butanol-ethanol fermentation by carbon monoxide and organic acids.

Metabolic modulation of acetone-butanol-ethanol fermentation by Clostridium acetobutylicum with carbon monoxide (CO) and organic acids is described. CO, which is a known inhibitor of hydrogenase, was found to be effective in the concentration range of dissolved CO corresponding to a CO partial pressure of 0.1 to 0.2 atm. Metabolic modulation by CO was particularly effective when organic acids such as acetic and butyric acids were added to the fermentation as electron sinks. The uptake of organic acids was enhanced, and increases in butyric acid uptake by 50 to 200% over control were observed. Hydrogen production could be reduced by 50% and the ratio of solvents could be controlled by CO modulation and organic acid addition. Acetone production could be eliminated if desired. Butanol yield could be increased by 10 to 15%. Total solvent yield could be increased 1 to 3% and the electron efficiency to acetone-butanol-ethanol solvents could be increased from 73 to 78% for controls to 80 to 85% for CO- and organic acid-modulated fermentations. Based on these results, the dynamic nature of electron flow in this fermentation has been elucidated and mechanisms for metabolic control have been hypothesized.

Journal Article↗
PubMed1984

Control of Carbon and Electron Flow in Clostridium acetobutylicum Fermentations: Utilization of Carbon Monoxide to Inhibit Hydrogen Production and to Enhance Butanol Yields.

Extracts prepared from non-solvent-producing cells of Clostridium acetobutylicum contained methyl viologen-linked hydrogenase activity (20 U/mg of protein at 37 degrees C) but did not display carbon monoxide dehydrogenase activity. CO addition readily inhibited the hydrogenase activity of cell extracts or of viable metabolizing cells. Increasing the partial pressure of CO (2 to 10%) in unshaken anaerobic culture tube headspaces significantly inhibited (90% inhibition at 10% CO) both growth and hydrogen production by C. acetobutylicum. Growth was not sensitive to low partial pressures of CO (i.e., up to 15%) in pH-controlled fermentors (pH 4.5) that were continuously gassed and mixed. CO addition dramatically altered the glucose fermentation balance of C. acetobutylicum by diverting carbon and electrons away from H(2), CO(2), acetate, and butyrate production and towards production of ethanol and butanol. The butanol concentration was increased from 65 to 106 mM and the butanol productivity (i.e., the ratio of butanol produced/total acids and solvents produced) was increased by 31% when glucose fermentations maintained at pH 4.5 were continuously gassed with 85% N(2)-15% CO versus N(2) alone. The results are discussed in terms of metabolic regulation of C. acetobutylicum saccharide fermentations to achieve maximal butanol or solvent yield.

Journal Article↗