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Biomedical subjects

A K Verma

Publications and source records attributed to A K Verma.

At least 73 records · Page 4Linked to original sources
PubMed1994

Non-AP-1 tumor promoter 12-O-tetradecanoylphorbol-13-acetate-responsive sequences in the human ornithine decarboxylase gene.

To define the mechanisms of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced transcription of the ornithine decarboxylase (ODC) gene, we isolated a genomic clone (hODC41B) of ODC from a human leukocyte genomic DNA library. The restriction endonuclease map, in comparison with the previously published sequences of the human ODC gene, indicated that hODC41B contained a 15.7-kb sequence that extended from the sixth exon to about 10 kb upstream of the ODC gene. A 2.5-kb genomic fragment containing the 5' flanking region and the first exon was subcloned and sequenced. Sequence analysis revealed multiple putative promoter/enhancer elements (a TATA box, a CAAT box, 17 GC boxes, and a cAMP-responsive element) but no consensus AP-1 sequences (TGAGTCA) in the 2.5-kb 5' flanking region. However, three AP-1 sequences were located in introns 3, 5, and 11. We constructed a series of chimeric genes containing part of the first exon and increasingly longer 5' flanking sequences of the ODC gene fused to either bacterial chloramphenicol acetyltransferase (CAT) or luciferase reporter genes. TPA inducibility was determined by transient transfection and measurement of CAT or luciferase expression in HeLa cells. The induction of CAT activity by TPA decreased with decreasing lengths of the 5' flanking sequences up to nt -82. The TPA induction from the construct -72 ODC CAT was threefold to sevenfold, and the TPA inducibility of the same fragment was about ninefold to 30-fold with the luciferase reporter gene. Further deletion analysis revealed TPA-responsive sequences in ODC nt -42 to +54. Gel mobility shift assays using alpha-32P-end labeled ODC nt -42 to +60 revealed that nt -42 to +60 specifically bound HeLa cell nuclear proteins. HeLa cell nuclear protein binding to ODC nt -42 to +60 could not be completely competed by AP-1-, AP-2-, AP-3-, or SP1-responsive sequences.

Base Sequence↗
PubMed1994

Management of giardiasis by an immuno-modulatory herbal drug Pippali rasayana.

Pippali rasayana (PR), an Ayurvedic herbal medicine, prepared from Piper longum (Pippali) and Butea monosperma (Palash), and prescribed for the treatment of chronic dysentery and worm infestations was tested for anti-giardial and immuno-stimulatory activity in mice, infected with Giardia lamblia trophozoites. It produced up to 98% recovery from the infection. The rasayana had no killing effect on the parasite in vitro. It induced significant activation of macrophages as evidenced by increased macrophage migration index (MMI) and phagocytic activity. Enhancement of host resistance could be one of the possible mechanisms contributing towards the recovery of animals from the giardial infection.

Adjuvants, Immunologic↗
PubMed1994

The mechanism of the inhibition of squamous differentiation of rat tracheal 2C5 cells by retinoic acid.

Retinoic acid (RA) plays an essential role in maintaining normal differentiation of tracheal epithelial cells. During vitamin A deficiency, tracheocytes undergo squamous metaplasia, an abnormal differentiation that can be reversed by RA. We used rat tracheal 2C5 cells to study the mechanism of inhibition of squamous differentiation by RA. 2C5 cells grown to confluence in the presence of serum underwent squamous differentiation as marked by an increase in their level of crosslinked envelope formation. The serum-induced crosslinked envelope formation was blocked by RA in 2C5 cells with an ED50 < 0.1 nM. However, the activity of the crosslinking enzyme, keratinocyte transglutaminase, did not correlate with the formation of crosslinked envelopes in 2C5 cells. Changes in biochemical markers of squamous differentiation such as an altered expression of specific cytokeratins also accompanied serum-induced squamous differentiation of 2C5 cells. The expression of the keratin squamous differentiation markers (i.e. K13) were inhibited by RA, although the ED50 for K13 expression was > 1 nM. The different dose responses for RA inhibiting differentiation markers suggests multiple mechanisms of regulation by RA. These results indicate that 2C5 cells remain responsive to differentiation factors such as RA and serum despite being an immortalized cell line.

Animals↗
PubMed1994

Retinoic acid nuclear receptors and tumor promotion: decreased expression of retinoic acid nuclear receptors by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate.

During studies to determine the mechanism of tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA), we found that TPA downregulates mouse epidermal retinoic acid nuclear receptors (RAR), a superfamily of nuclear steroid/thyroid receptors implicated in mediating effects of retinoic acid (RA). Application of TPA to mouse skin decreased the binding of [3H]RA to RAR from mouse epidermal nuclear extracts. In this experiment, 20 nmol of TPA was applied to mouse skin and 3.5 h later binding of [3H]RA to RAR was analyzed by chromatography on a size-exclusion column. TPA treatment resulted in an approximately 67% decrease in the specific binding of [3H]RA to RAR. In a more detailed time course, application of 20 nmol of TPA to mouse skin led to 20, 36, 92 and 0% decrease in the binding of [3H]RA to mouse epidermal RAR at 2, 4, 12 and 72 h after treatment respectively. Okadaic acid, an inhibitor of protein phosphatases 1 and 2A but a mouse skin tumor promoter, also inhibited the binding of RA to RAR. RAR alpha and RAR gamma, but not RAR beta mRNA, could be detected in mouse epidermis. In addition, RA nuclear receptor RXR alpha was also expressed in the mouse epidermis. As determined by Northern blot analysis of total as well as poly(A)+ RNA, application of 10 nmol of TPA to mouse skin led to decreased expression of RAR alpha, RAR gamma and RXR alpha mRNA at 3.5 h after treatment. The effect of TPA on the attenuation of RAR expression was specific. Specific binding of RA to RAR was decreased when TPA-induced expression of the c-fos, c-jun and ornithine decarboxylase gene was increased. Downregulation of RAR(s) may be an essential component of the mechanism of mouse skin tumor promotion.

Animals↗
PubMed1994

Involvement of protein kinase C in the transcriptional regulation of 12-O-tetradecanoylphorbol-13-acetate-inducible genes modulated by AP-1 or non-AP-1 transacting factors.

The involvement of protein kinase C (PKC), a 12-O-tetradecanoylphorbol-13-acetate (TPA) receptor, in the transcriptional regulation of TPA-inducible genes was determined. Expression plasmids harboring full-length or kinase domain of PKC alpha and PKC delta (PKC alpha K and PKC delta K) were constructed. Transient transfection of PKC alpha K and PKC delta K into COS cells resulted in approximately 20- and 16-fold increase in phospholipid-, calcium-independent protein kinase activity. To determine the effects of overexpression of PKC alpha K and PKC delta K on the AP-1-mediated TPA-inducible genes, we transfected into COS cells the PKC alpha K or PKC delta K expression plasmids with collagenase chloramphenicol acetyltransferase (CAT) reporter construct containing one TPA responsive element (TRE), or a construct containing five synthetic TRE linked to a thymidine kinase promoter. PKC alpha K or PKC delta K overexpression resulted in a comparable increase (approximately 4-fold) in CAT activity. However, CAT activity was not increased after transfection of PKC constructs with non-TPA responsive thyroid hormone responsive elements CAT construct (delta MTV-TyRE-pCAT). We also found that deletion of the AP-1-like motif in the SV40 promoter abolished the PKC alpha K or PKC delta K-induced activity of luciferase (luc) reporter constructs. Overexpression of full-length PKC delta in COS cells also increased the activity of the CAT construct with TRE after TPA treatment. We determined the effects of overexpression of PKC alpha K and PKC delta K on transcription of the ornithine decarboxylase (ODC) gene, which has a non-AP-1 TRE. Cotransfection of PKC alpha K or PKC delta K expression plasmids with a TPA-inducible ODC luc construct (-72/+130-ODC-luc) into HeLa cells resulted in an increased luc activity. These results indicate that both PKC alpha (calcium dependent) and PKC delta (calcium independent) may mediate the transcription of TPA-inducible genes through both AP-1 and non-AP-1 sequences.

Animals↗
PubMed1994

Fine needle aspiration cytology of salivary gland lesions.

247 salivary gland lesions were subjected to fine needle aspiration (FNA) cytology; 179 were designated as neoplastic lesions and 68 as non-neoplastic. Based on cytomorphologic features, the neoplastic and non-neoplastic lesions were subcategorised. All but 36 of the neoplastic lesions were subjected to histopathologic study. The overall diagnostic accuracy of FNA cytology for neoplastic lesions was 91%. The sensitivity rate for detecting malignant tumours was 87.8% and the specificity 98.0%. There was 100% sensitivity for cytodiagnosis of benign tumours. The high sensitivity and specificity of cytodiagnosis makes FNA cytology a valuable diagnostic modality in the evaluation of salivary gland lesions.

Adenocarcinoma↗
PubMed1994

Pre and postoperative median nerve conduction in patients with pituitary tumour.

A study of median nerve sensory conduction at the wrist was performed in 34 patients with pituitary adenomas prior to and following surgery. In 31 patients this was done bilaterally. They included 11 patients with acromegalic features, 3 of whom had features of carpal tunnel syndrome. Six out of 11 (55%) acromegalics had abnormal latencies and conduction velocities pre-operatively. Among the remaining patients only 3 had conduction delay pre-operatively. Postoperative improvement in conduction velocity and latency was recorded in 24 patients although significant improvement was observed in only 13 patients. All 3 patients with carpal tunnel syndrome had significant improvement in conduction velocities and latencies following the surgery. There was no definite relationship between conduction velocity and the pre-operative hormonal profile.

Acromegaly↗
PubMed1993

A highly active 120-kDa truncated mutant of the plasma membrane Ca2+ pump.

A truncated mutant (hPMCA4b(ct120)) of the plasma membrane Ca2+ pump was expressed in COS-1 cells. The full-length pump (hPMCA4b) consisted of 1205 residues, and the mutant lacked 120 residues (including the 28-residue calmodulin-binding inhibitory domain) at the COOH terminus. To characterize this construct, Ca2+ transport was determined in a microsomal fraction. Phosphate was added to increase Ca2+ uptake, and specificity was enhanced by adding thapsigargin to inhibit the endoplasmic reticulum Ca2+ pump. The mutant showed a similar level of expression as hPMCA4b and a Ca2+ affinity and Ca2+ transport activity about equal to that of hPMCA4b when hPMCA4b was activated. Addition of the synthetic peptide C28R2, corresponding to the calmodulin binding region of the pump, inhibited the mutant and restored the non-activated state of the enzyme. In these respects, the truncated mutant acted like hPMCA4b, when hPMCA4b had been proteolyzed to cleave a bond between the calmodulin binding region and the NH2-terminal portion of the molecule. This indicates that the effects of proteolysis are due to removal of the COOH terminus and not to rearrangement of the two fragments. Since the truncated mutant was fully active and its tryptic digestion resulted in the appearance of the expected 81- and 76-kDa active fragments, we concluded that the COOH-terminal portion which is missing cannot be important in synthesis or proper folding of the enzyme.

Alternative Splicing↗
PubMed1993

Randomized phase I chemoprevention dose-seeking study of alpha-difluoromethylornithine.

BACKGROUND: alpha-Difluoromethylornithine (DFMO) is an irreversible inhibitor of ornithine decarboxylase (ODC), the key enzyme in mammalian polyamine biosynthesis. Levels of ODC are closely related to tumor promotion, and inhibition of ODC is associated with suppression of tumor development in laboratory animals. DFMO has shown a dose-response effect in tumor inhibition in mice. PURPOSE: A randomized phase I study of DFMO was conducted to determine the lowest daily oral dose that can achieve at least 50% inhibition of ODC activity induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in human skin, with minimal clinical toxicity (grade 1 or lower; Eastern Cooperative Oncology Group [ECOG]). METHODS: Cancer patients entered in steps 1 and 2 of the study had been treated and had no clinical evidence of cancer. In step 1, 13 patients received 0.125, 0.25, 0.5, or 0.75 g/m2 DFMO four times a day. In step 2, 13 patients received 0.125 or 0.25 g/m2 four times a day or 0.5 or 1.0 g/m2 every day. The 26 patients treated in steps 1 and 2 (range, < 1-6 months) had colon, prostate, or bladder cancer. In step 3, six cancer-free subjects at risk for colorectal cancer received 0.5 g/m2 every day for 5-12 months. To evaluate the effectiveness of DFMO in reducing TPA-induced ODC activity, we calculated the percent change from pretreatment ODC levels in skin biopsy specimens and the percentage of subjects with at least a 50% reduction in ODC levels. RESULTS: In step 1 of the study, treatment-limiting audiotoxicity was observed at the three highest doses. Because the only dose with no major toxic effects in step 2 was 0.5 g/m2 every day, that dose was administered in step 3, with no major toxic effects. Seven subjects treated with 0.5 g/m2 every day had pretreatment ODC levels in the normal range; five averaged a reduction in ODC activity of at least 50%. DFMO had linear pharmacokinetics over the entire dose range. When 0.5 g/m2 was given every day, the peak plasma concentration was 47.1 +/- 5.1 microM at 3-4 hours (monthly mean +/- SE, 14.5 +/- 5.2 microM); half-life was 3.5 hours; and area under the curve for plasma concentration x time for a single dose of DFMO was 311 +/- 39 microM x hour. CONCLUSIONS: These data support phase II chemoprevention studies with DFMO given at a dose of 0.5 g/m2 every day. IMPLICATIONS: Studies investigating prevention of cancers with DFMO are under consideration.

Adult↗
PubMed1993

Testicular cytology in azoospermia.

Two hundred-seventy-five azoospermic males were subjected to fine-needle aspiration (FNA) cytologic study of testis with the aim of determining the cause of azoospermia; 534 aspirates from these patients were classified as follows: normal spermatogenesis (162), hypospermatogenesis (mild, moderate, or severe, 226), absence of spermatogenesis (130), maturation arrest (36), Sertoli-cell-only syndrome (14), and Leydig-cell hyperplasia (3). The morphology of cells was excellent in the cytologic preparations and various spermatogenic cells and Sertoli cells were easily recognized. Leydig cells were uncommonly seen, except in cases of Leydig-cell hyperplasia. Degenerative changes, possibly due to obstruction, were seen in 104 cases. The procedure was well tolerated by the patients. We conclude that FNA cytology is a useful investigative modality in the evaluation of azoospermic males.

Biopsy, Needle↗
PubMed1993

Aspiration cytology of maxillary myxoma.

Fine-needle aspiration was used to diagnose a case of maxillary myxoma. Abundant mucoid material was obtained. Microscopic examination showed three-dimensional fibrillary myxoid fragments entangling spindle-shaped, stellate, and fusiform cells with round to oval monomorphic nuclei. A striking feature was delicately branching capillaries. The diagnosis was subsequently confirmed on histology and histochemistry.

Adult↗
PubMed1993

Transrectal fine needle aspiration of prostate.

56 patients with prostatic enlargement were subjected to transrectal fine needle aspiration (FNA) of prostate. The cytologic diagnosis was correlated with histology in 55 cases. Benign prostatic hyperplasia (BPH) was diagnosed in 44 cases. In 18 of these, there was associated chronic prostatitis in three cases acute prostatitis and in two cases granulomatous prostatitis. One case of tuberculous prostatitis and 11 cases of prostatic carcinoma could also be diagnosed on cytologic basis. There was only one false negative and no false positive cytodiagnosis was made.

Adenocarcinoma↗
PubMed1992

Overexpression of the erythrocyte plasma membrane Ca2+ pump in COS-1 cells.

A full-length cDNA corresponding to the hPMCA4 plasma membrane Ca2+ pump was assembled and expressed in COS-1 cells. The original sequence of hPMCA4 gave a very low expression. The mutation of the initiation translation site of this sequence to the consensus A/G-X-X-AUG-G increased the production of the protein. The Ca2+ pump activity in transfected cells was 1.5-3.5-fold higher than in controls. The Ca(2+)-dependence and the calmodulin stimulation of hPMCA4 expressed in COS-1 cells were comparable with those of the erythrocyte Ca2+ pump. Immunohistochemistry experiments showed that most of the expressed protein remained in intracellular membranes. Possible explanations for this targeting of the pump are discussed.

Animals↗
PubMed1992

The housefly (Musca domestica) as a carrier of pathogenic microorganisms in a hospital environment.

Houseflies have long been regarded as potential carriers of microorganisms. Since pathogenic microorganisms are widespread in the hospital environment, there is abundant opportunity for flies to become contaminated and, in turn, to contaminate the patient environment. In the present study, an attempt was made to isolate and identify pathogenic bacteria, fungi and parasites from the housefly Musca domestica collected in the surgical ward of the All India Institute of Medical Sciences Hospital and also in a remote residential area located 5 km from the hospital. A total of 113 flies were collected: 65 from a surgical ward (test) and 48 from a residential area for comparison. Ten genera of bacteria were isolated from the test group of flies compared with nine from the control group. In primary isolations, it was observed that the load of bacteria carried by the test group of flies was significantly more (P less than 0.001) than for the control flies. Pseudomonas aeruginosa, Enterococcus faecalis and viridans streptococci were isolated only from the test flies. The isolation rate of Staphylococcus aureus was significantly higher (P less than 0.001) in test houseflies than in the control houseflies. There was no significant difference in isolation of parasitic ova and cysts from test and control houseflies. Candida spp. were isolated in almost equal numbers from both groups of houseflies, yet none of these was Candida albicans. Houseflies therefore may act as vectors of potentially pathogenic bacteria in a hospital environment.

Animals↗
PubMed1992

Expression of retinoic acid nuclear receptors and tissue transglutaminase is altered in various tissues of rats fed a vitamin A-deficient diet.

The effects of vitamin A nutritional status on the levels of expression of retinoic acid nuclear receptors (RAR), and the retinoic acid-responsive gene, tissue transglutaminase, were determined in rats. Weanling male Sprague-Dawley rats fed a vitamin A-deficient diet for approximately 7 wk developed vitamin A deficiency, as confirmed by the depletion of liver retinol and retinyl palmitate. Controls were fed the same diet supplemented with 24 mg/kg retinyl acetate. The levels of expression of RAR beta mRNA were approximately 80% lower in bladder, brain, liver, lung and trachea and those of RAR gamma mRNA were approximately 50% lower in bladder, lung and trachea of rats fed the vitamin A-deficient diet than in controls. The levels of expression of RAR alpha mRNA were approximately 90% lower in brain and approximately 30% greater in liver, kidney, intestine and lung of rats fed the vitamin A-deficient diet. Vitamin A deficiency also resulted in reduced expression of tissue transglutaminase in the bladder, lungs and trachea, which paralleled the effects observed for RAR beta and RAR gamma. When vitamin A-deficient rats were subsequently fed a retinol-deficient diet supplemented with retinoic acid for 4 wk, the expression of RAR (beta and gamma) and tissue transglutaminase returned to the control levels. These results indicate that vitamin A nutritional status in rats influences the expression of both RAR and tissue transglutaminase in certain tissues.

Animals↗
PubMed1992

Some effects of vitamin A deficiency on the isolated rat lung alveolar type II cell.

Alveolar Type II cells were isolated from control and vitamin A deficient rats and allowed to form a monolayer in plastic dishes for 16-18 hours. The vitamin A content (retinol plus retinyl palmitate) of deficient cells was 50-75% less than in control cells on a per mg protein basis. Isolated Type II cells took up [3H]-retinol, synthesized [3H]-retinyl palmitate, and after 4 hours, 24% of the radioactivity in the Type II cells was [3H]-retinoic acid. Deficiency did not appear to alter retinoic acid synthesis. Phosphatidylcholine (PC) and disaturated phosphatidylcholine (DSPC) synthesis, were slightly less in deficient cells compared to control (95 and 85% respectively). In addition, 10(-6) M and 10(-5) M retinoic acid in the reaction media stimulated both PC and DSPC synthesis by 120-140% in control cells. The stimulating effect of retinoic acid was present in deficient cells as well, but less pronounced (120% with 10(-5) M). Vitamin A deficient Type II cells also had less basal levels of both tissue transglutaminase and epidermal transglutaminase activity than control cells.

Animals↗