Biomedical subjects

P K Majumder

Publications and source records attributed to P K Majumder.

At least 19 recordsLinked to original sources

PubMed2002

In vivo modulation of androgen receptor by androgens.

AIM: To study the effect of androgen and antiandrogen on the level of androgen receptor (AR) mRNA. METHODS: The total RNA was extracted from the prostate and analyzed by slot blot analysis. The blots were hybridized with AR cDNA probe and 1A probe (internal control) and autoradiography was performed. The intensity of signal was measured with a densitometer and the ratio of AR RNA and 1A RNA was calculated. RESULTS: Androgenic deprivation produced by castration decreased the weight of the prostate and increased the levels of AR mRNA. Treatment of the castrated rats with testostrone increased the weight of prostate and decreased the levels of AR mRNA. Treatment of normal rats with flutamide decreased the weight of the gland and increased the levels of AR mRNA. CONCLUSION: Androgens produce proliferative effect on the prostate and negatively regulate the AR transcription.

Animals↗

PubMed2001

Targeting of protein kinase C delta to mitochondria in the oxidative stress response.

The cellular response to oxidative stress includes the release of mitochondrial cytochrome c and the induction of apoptosis. Here we show that treatment of diverse cells with hydrogen peroxide (H2O2) induces the targeting of protein kinase C delta (PKCdelta) to mitochondria. The results demonstrate that H2O2-induced activation of PKCdelta is necessary for translocation of PKCdelta from the cytoplasm to the mitochondria. The results also show that mitochondrial targeting of PKCdelta is associated with the loss of mitochondrial transmembrane potential and release of cytochrome c. The functional importance of this event is also supported by the demonstration that H2O2-induced apoptosis is blocked by the inhibition of PKCdelta activation and translocation to mitochondria. These findings indicate that mitochondrial targeting of PKCdelta is required, at least in part, for the apoptotic response of cells to oxidative stress.

3T3 Cells↗

PubMed2000

Mitochondrial translocation of protein kinase C delta in phorbol ester-induced cytochrome c release and apoptosis.

Apoptosis is induced by the release of cytochrome c from mitochondria to the cytoplasm. The present studies demonstrate that the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) induces translocation of protein kinase C (PKC) delta from the cytoplasm to mitochondria. The results also show that translocation of PKCdelta results in release of cytochrome c. The functional significance of this event is further supported by the demonstration that PKCdelta translocation is required for TPA-induced apoptosis. These findings demonstrate that translocation of PKCdelta to mitochondria is responsible, at least in part, for inducing cytochrome c release and apoptosis.

Apoptosis↗

PubMed2000

Regulation of the rapamycin and FKBP-target 1/mammalian target of rapamycin and cap-dependent initiation of translation by the c-Abl protein-tyrosine kinase.

The c-Abl protein-tyrosine kinase is activated by ionizing radiation and certain other DNA-damaging agents. The rapamycin and FKBP-target 1 (RAFT1), also known as FKBP12-rapamycin-associated protein (FRAP, mTOR), regulates the p70S6 kinase (p70(S6k)) and the eukaryotic initiation factor 4E (eIF4E)-binding protein 1 (4E-BP1). The present results demonstrate that c-Abl binds directly to RAFT1 and phosphorylates RAFT1 in vitro and in vivo. c-Abl inhibits autophosphorylation of RAFT1 and RAFT1-mediated phosphorylation p70(S6k). The functional significance of the c-Abl-RAFT1 interaction is further supported by the finding that eIF4E-dependent translation in mouse embryo fibroblasts from Abl(-/-) mice is significantly higher than that compared in wild-type cells. The results also demonstrate that exposure of cells to ionizing radiation is associated with c-Abl-mediated binding of 4E-BP1 to eIF4E and inhibition of translation. These findings with the c-Abl tyrosine kinase represent the first demonstration of a negative physiologic regulator of RAFT1-mediated 5' cap-dependent translation.

Animals↗

PubMed2000

Functional interaction between RAFT1/FRAP/mTOR and protein kinase cdelta in the regulation of cap-dependent initiation of translation.

Hormones and growth factors induce protein translation in part by phosphorylation of the eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). The rapamycin and FK506-binding protein (FKBP)-target 1 (RAFT1, also known as FRAP) is a mammalian homolog of the Saccharomyces cerevisiae target of rapamycin proteins (mTOR) that regulates 4E-BP1. However, the molecular mechanisms involved in growth factor-initiated phosphorylation of 4E-BP1 are not well understood. Here we demonstrate that protein kinase Cdelta (PKCdelta) associates with RAFT1 and that PKCdelta is required for the phosphorylation and inactivation of 4E-BP1. PKCdelta-mediated phosphorylation of 4E-BP1 is wortmannin resistant but rapamycin sensitive. As shown for serum, phosphorylation of 4E-BP1 by PKCdelta inhibits the interaction between 4E-BP1 and eIF4E and stimulates cap-dependent translation. Moreover, a dominant-negative mutant of PKCdelta inhibits serum-induced phosphorylation of 4E-BP1. These findings demonstrate that PKCdelta associates with RAFT1 and thereby regulates phosphorylation of 4E-BP1 and cap-dependent initiation of protein translation.

Androstadienes↗

PubMed2000

Observations on EGFR gene amplification and polymorphism in prostatic diseases.

This study was designed to determine the amplification and polymorphism of epidermal growth factor receptor (EGFR) gene in prostatic diseases like benign hypertrophy (BPH) and carcinoma (CaP). The EGFR gene was found to be amplified in grade IV BPH as compared to grade II BPH. Digestion of genomic DNA with MspI and HpaII revealed the presence of a 5kb band following southern blot analysis. This 5kb band was present in all the CaP cases and in one out of three BPH cases. It is possible that such a polymorphism is associated with the type or extent of tumor progression.

Aged↗

PubMed1999

Activation of p38 mitogen-activated protein kinase by PYK2/related adhesion focal tyrosine kinase-dependent mechanism.

The stress-activated p38 mitogen-activated protein kinase (p38 MAPK), a member of the subgroup of mammalian kinases, appears to play an important role in regulating inflammatory responses, including cytokine secretion and apoptosis. The upstream mediators that link extracellular signals with the p38 MAPK signaling pathway are currently unknown. Here we demonstrate that pp125 focal adhesion kinase-related tyrosine kinase RAFTK (also known as PYK2, CADTK) is activated specifically by methylmethane sulfonate (MMS) and hyperosmolarity but not by ultraviolet radiation, ionizing radiation, or cis-platinum. Overexpression of RAFTK leads to the activation of p38 MAPK. Furthermore, overexpression of a dominant-negative mutant of RAFTK (RAFTK K-M) inhibits MMS-induced p38 MAPK activation. MKK3 and MKK6 are known potential constituents of p38 MAPK signaling pathway, whereas SEK1 and MEK1 are upstream activators of SAPK/JNK and ERK pathways, respectively. We observe that the dominant-negative mutant of MKK3 but not of MKK6, SEK1, or MEK1 inhibits RAFTK-induced p38 MAPK activity. Furthermore, the results demonstrate that treatment of cells with 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid, tetra(acetoxymethyl)-ester, a membrane-permeable calcium chelator, inhibits MMS-induced activation of RAFTK and p38 MAPK. Taken together, these findings indicate that RAFTK represents a stress-sensitive mediator of the p38 MAPK signaling pathway in response to certain cytotoxic agents.

Animals↗

PubMed1999

Bcl-xL blocks activation of related adhesion focal tyrosine kinase/proline-rich tyrosine kinase 2 and stress-activated protein kinase/c-Jun N-terminal protein kinase in the cellular response to methylmethane sulfonate.

The stress-activated protein kinase/c-Jun N-terminal protein kinase (JNK) is induced in response to ionizing radiation and other DNA-damaging agents. Recent studies indicate that activation of JNK is necessary for induction of apoptosis in response to diverse agents. Here we demonstrate that methylmethane sulfonate (MMS)-induced activation of JNK is inhibited by overexpression of the anti-apoptotic protein Bcl-xL, but not by caspase inhibitors CrmA and p35. By contrast, UV-induced JNK activity is insensitive to Bcl-xL. The results demonstrate that treatment with MMS is associated with an increase in tyrosine phosphorylation of related adhesion focal tyrosine kinase (RAFTK)/proline-rich tyrosine kinase 2 (PYK2), an upstream effector of JNK and that this phosphorylation is inhibited by overexpression of Bcl-xL. Furthermore, overexpression of a dominant-negative mutant of RAFTK (RAFTK K-M) inhibits MMS-induced JNK activation. The results indicate that inhibition of RAFTK phosphorylation by MMS in Bcl-xL cells is attributed to an increase in tyrosine phosphatase activity in these cells. Hence, treatment of Bcl-xL cells with sodium vanadate, a tyrosine phosphatase inhibitor, restores MMS-induced activation of RAFTK and JNK. These findings indicate that RAFTK-dependent induction of JNK in response to MMS is sensitive to Bcl-xL, but not to CrmA and p35, by a mechanism that inhibits tyrosine phosphorylation and thereby activation of RAFTK. Taken together, these findings support a novel role for Bcl-xL that is independent of the caspase cascade.

Calcium-Calmodulin-Dependent Protein Kinases↗

PubMed1998

Comparative analysis of epidermal growth factor receptor mRNA levels in normal, benign hyperplastic and carcinomatous prostate.

Epidermal growth factor receptor (EGFR), a mediator of mitogenic activity of epidermal growth factor and transforming growth factor-alpha, has been shown to be associated with tumour progression. We have detected a level of EGFR transcript in normal, hyperplastic (BPH) and carcinomatous (CaP) prostate tissues by cytoplasmic dot hybridization. Our results show that the majority of CaP cases (62% of untreated cases and 71% of treated cases) were positive for EGFR mRNA while about 50% of normal and BPH cases were positive for EGFR mRNA. The level of EGFR transcript was significantly higher in the untreated CaP group as compared to the normal group (P < 0.05), while the difference in the normal and BPH groups was not statistically significant.

Adult↗

PubMed1998

Detection of receptor transcripts for androgen, epidermal growth factor and basic fibroblast growth factor in human prostate postmortem.

RNA isolated from frozen human postmortem prostate tissue was evaluated for its utility in molecular biological studies based on RNA analysis. Our results on slot-blot analysis show the presence of receptor transcripts for androgen, epidermal growth factor and basic fibroblast growth factor in postmortem prostate tissue obtained 20-120 hrs after death. However, the RNA in these samples was found to be degraded as revealed by the absence of ribosomal bands on gel electrophoresis. AR mRNA was found to be present in one of the five samples when analysed by northern blotting.

Adult↗

PubMed1997

Androgen receptor mRNA detection in the human foetal prostate.

In order to get an insight into androgen-mediated differentiation and development of the prostate, we detected the androgen receptor (AR) mRNA in the urogenital sinus of human foetuses at 12 and 16 weeks of gestation. Cytoplasmic dot hybridization using radiolabelled cDNA probe for human androgen receptor (AR) was performed. The AR mRNA could be detected at 12 weeks of gestation and its level was higher at 16 weeks of gestation.

Autoradiography↗

PubMed1997

Anti-steroidogenic activity of the petroleum ether extract and fraction 5 (fatty acids) of carrot (Daucus carota L.) seeds in mouse ovary.

The petroleum ether extract and fraction 5 (fatty acids) of carrot seeds arrested the normal estrus cycle of adult mouse and reduced the weight of ovaries significantly. The cholesterol and ascorbic acid content in ovaries were significantly elevated due to the treatment with extract and fraction 5 (fatty acids) of carrot seeds. The significant inhibition of delta 5,3-beta-hydroxy steroid dehydrogenase and glucose-6-phosphate dehydrogenase, the two key enzymes involved in ovarian steroidogenesis, were also observed in mouse ovaries after 15 days of treatment. Results of this study revealed that the fraction 5 (fatty acids) present in carrot seeds acts as an antisteroidogenic agent.

Alkanes↗

PubMed1997

Androgen deprivation causes up-regulation of androgen receptor transcript in the rat prostate.

We have studied the effect of androgenic deprivation on the level of androgen receptor transcript in the rat ventral prostate. The rats were treated with estradiol benzoate, flutamide and [D Trp6, des Gly10]gonadotropin releasing hormone (GnRH) for different time periods. These treatments produced a significant decrease in the weight of prostate. Total RNA isolated from the ventral prostates was hybridized with the cDNA probe for androgen receptor. Densitometric analysis of the autoradiographic signal revealed a rise in the level of androgen receptor RNA following treatment of rats with estradiol benzoate and flutamide. Treatment of rats with [D Trp6, des Gly10] GnRH brought about a transient rise in the level of androgen receptor RNA. Thus, our results indicate that androgenic deprivation up-regulates the level of androgen receptor transcript.

Androgens↗

PubMed1997

Androgen receptor transcript level in benign hypertrophy and carcinoma of the human prostate.

OBJECTIVE: Current reports suggest the presence of androgen receptor (AR) defects in prostate cancer. We have detected the AR mRNA in normal, benign hypertrophied (BPH) and carcinomatous (CaP) prostate tissues and evaluated the difference in the level of AR transcript in these groups. MATERIALS AND METHODS: Cytoplasmic dot hybridization assay was used to measure the levels of AR mRNA in 21 normal, 45 BPH and 30 CaP specimens. Tissue samples of 14 CaP patients receiving endocrine treatment were also analyzed. Blots were autoradiographed and the intensity of the signal was measured by densitometry. RESULTS AND CONCLUSIONS: The majority of cases in all the 3 groups were positive for the AR mRNA. All the patients who had received endocrine treatment were also positive for the AR mRNA. The level of the AR mRNA was significantly higher in BPH and treated CaP cases as compared to normal cases (p < 0.05). Among the CaP cases the level of AR transcript was significantly higher in the treated group as compared to the untreated group.

Adult↗

PubMed1995

Cardiovascular and respiratory changes following exposure to a synthetic toxin of Ptychodiscus brevis.

The present study demonstrated cardiorespiratory effects of a synthetic phosphorus-containing ichthyotoxic metabolite elaborated by the marine dinoflagellate Ptychodiscus brevis in anaesthetised cats. The metabolite at a dose of 0.25-1.5 mg/kg i.v., resulted in a dose-dependent fall in blood pressure and such vasodepressor effect was associated with bradycardia. There is initial respiratory apnoea followed by increased rate and depth of respiration (hyperapnoea) following the administration of the toxin. The hypotensive response was accompanied by a decrease in aortic baroreceptor activity. The ECG showed atrioventricular conduction block, arrhythmia and depression of S-T segment and T wave which indicated coronary insufficiency. Vasodepressive property of the toxin is presumably muscarinic in nature as atropine counteracted the vasodepression.

Animals↗

PubMed1995

Prostate gland: structure, functions and regulation.

The prostate gland plays an important role in male reproduction. It secretes enzymes, lipids, amines and metal ions essential for the normal function of spermatozoa. Development, differentiation and maintenance of the prostate gland depend on steroid and peptide hormones. Beside hormones growth factors also regulate the prostate gland. This review will focus on the structure, functions and mode of regulation of the prostate gland.

Animals↗

PubMed1995

Inhibitory effects of formaldehyde on the reproductive system of male rats.

Formaldehyde, when administered to rats at a dose of 10 mg/kg body weight/day for a period of 30 days, resulted in a significant fall in sperm motility, viability and count. In addition, the DNA content was significantly lower in testis and prostate while the tissue protein content of prostate and epididymis had decreased in the treated rats. In vitro exposure to formaldehyde also inhibited the sperm motility and viability.

Animals↗

PubMed1983

Correlation between nuclear glucocorticoid receptor levels and casein gene expression in murine mammary gland in vitro.

The relationship between nuclear binding of glucocorticoid-receptor complex and casein gene expression was studied in organ culture of the whole mammary gland of the mouse. Pyridoxal 5'-phosphate was used as a modulatory agent for measuring nuclear binding of the receptor complex. Addition of 2 mM and 5mM pyridoxal-5'-P in the medium (Waymouth's MB752/1) resulted in 4- and 12-fold increase of its concentration in the glands incubated with insulin, prolactin, and hydrocortisone. Pyridoxal-5'-P also caused a 52% and 92% inhibition of nuclear binding of [3H]dexamethasone in the glands at 2 mM and 5 mM concentration in the presence of the same hormones in the medium. Corresponding to the reduced nuclear binding of the receptor complex casein mRNA levels, measured by a specific cDNA probe was reduced 86% and over 90% in the glands exposed to 2 mM and 5 mM pyridoxal-5'-P, respectively, in presence of insulin, prolactin, and hydrocortisone in the medium. Withdrawal of pyridoxal-5'-P from the medium restored nuclear binding of the receptor complex near the level of control glands incubated only with the hormones. mRNA casein levels also increased in the gland in the pyridoxal-5'-P-free medium containing the same hormones. This indicates that pyridoxal-5'-P does not alter the specific hormone responsiveness of the mammary cells and its action mediated at the level of the glucocorticoid receptor can influence hormone-inducible expression of the casein genes. Thus, glucocorticoid plays a major role in the multiple hormone regulation of the milk protein gene(s). The findings also suggest that the breast tissue concentration of the vitamin B6 derivative may influence the physiology of lactation in nursing mothers.

Animals↗