Biomedical subjects

Indrajit Chowdhury

Publications and source records attributed to Indrajit Chowdhury.

5 recordsLinked to original sources

PubMed2006

Molecular cloning and sequence analysis of the cDNA encoding thyroid-stimulating hormone beta-subunit of common duck and mule duck pituitaries: in vitro regulation of steady-state TSHbeta mRNA level.

For better understanding of phylogenetic diversity and evolution of pituitary thyroid-stimulating hormone (TSH) in birds, we have cloned the cDNAs encoding TSH beta subunit (TSHbeta), by reverse transcription-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE) from two species of domestic ducks, common duck (Tsaiya duck and Pekin duck) (Anas platyrhynchos domesticus) and mule duck (hybrid of male muscovy duck Cairina moschata and female A. platyrhynchos domesticus). The nucleotide sequences of isolated TSHbeta cDNAs of the two species of ducks are identical, with each including 66 bp of 5'-untranslated region (UTR), 402 bp of coding region, and 82 bp 3'-UTR followed by 18 bp poly A tract. The deduced TSHbeta subunit of the ducks contains 134 amino acids consisting of a putative signal peptide of 19 amino acids and a putative mature protein of 115 amino acids. However, the TSHbetas of common duck and mule duck differ from the TSHbeta of muscovy duck in one amino acid at position 97 of the mature protein: isoleucine for common duck and mule duck, and valine for muscovy duck. Our findings thus demonstrate that inter-genus variation of TSHbeta exists in Family Anatidae, and that TSHbeta gene in the mule duck is preferentially transcribed from the maternal genome rather than from the paternal genome. TSHbeta mRNA expressions were investigated by culturing common duck pituitaries with various doses of hormones. Thyrotropin-releasing hormone (TRH) stimulated, while thyroid hormones, triiodothyronine (T(3)) and thyroxine (T(4)), inhibited the TSHbeta mRNA levels, in dose-related manners. The findings thus support that the mode of regulation of TSH gene expression in hypothalamo-pituitary-thyroid axis in birds is similar to that in mammals. Cortisol and corticosterone decreased the steady-state TSHbeta mRNA levels at the pituitary level, in a dose-related manner, the first-time demonstration in vertebrates. The results may suggest that glucocorticoids exert suppressive action directly at pituitary level in modulation of steady-state TSHbeta mRNA level.

Amino Acid Sequence↗

PubMed2006

Apoptosis of rat granulosa cells after staurosporine and serum withdrawal is suppressed by adenovirus-directed overexpression of prohibitin.

Prohibitin (Phb1) is a highly conserved mitochondrial protein that is associated with granulosa cell differentiation, atresia, and luteolysis. Although prohibitin has been implicated in the suppression of apoptosis in mammalian cells, its specific role in programmed cell death in granulosa cells is unknown. In the present study, we examined the role of prohibitin in mediating staurosporine (STS) and serum withdrawal induced apoptosis in undifferentiated rat granulosa cells. Treatment of granulosa cells isolated from immature rat ovaries with STS and/or serum withdrawal induced a rapid decrease in the transmembrane potential of mitochondria, resulting in increased prohibitin content and induced apoptosis in a time- and dose-dependent manner. Infection of granulosa cells with a Phb1 adenoviral construct resulted in overexpression of prohibitin that markedly attenuated the ability of STS and serum withdrawal to induce apoptosis via the intrinsic apoptotic pathway. To determine the site of action of Phb1, granulosa cells were transfected with a prohibitin-eGFP fusion construct, and the fusion protein expression patterns were analyzed by fluorescence microscopy and Western blot analysis of cell fractionated samples. These studies indicated that the prohibitin-eGFP fusion protein moved from the cytoplasm into the mitochondria. However, no prohibitin-eGFP fusion protein was observed in the nucleus in response to the STS-induced apoptotic stimulus. This result was corroborated by Western blot analysis with green fluorescent protein-specific antibody. Furthermore, the prohibitin-eGFP fusion protein also inhibited programmed cell death. These results provide evidence that prohibitin could serve an antiapoptotic role in undifferentiated granulosa cells.

Adenoviridae↗

PubMed2006

Current concepts in apoptosis: the physiological suicide program revisited.

Apoptosis, or programmed cell death (PCD), involves a complex network of biochemical pathways that normally ensure a homeostatic balance between cellular proliferation and turnover in nearly all tissues. Apoptosis is essential for the body, as its deregulation can lead to several diseases. It plays a major role in a variety of physiological events, including embryonic development, tissue renewal, hormone-induced tissue atrophy, removal of inflammatory cells, and the evolution of granulation tissue into scar tissue. It also has an essential role in wound repair. The various cellular and biochemical mechanisms involved in apoptosis are not fully understood. However, there are two major pathways, the extrinsic pathway (receptor-mediated apoptotic pathway) and the intrinsic pathway (mitochondria-mediated apoptotic pathway), which are both well established. The key component in both is the activation of the caspase cascade. Caspases belong to the family of proteases that ultimately, by cleaving a set of proteins, cause disassembly of the cell. Although the caspase-mediated proteolytic cascade represents a central point in the apoptotic response, its initiation is tightly regulated by a variety of other factors. Among them, Bcl-2 family proteins, TNF and p53 play pivotal roles in the regulation of caspase activation and in the regulation of apoptosis. This review summarizes the established concepts in apoptosis as a physiological cell suicide program, highlighting the recent and significant advances in its study.

Animals↗

PubMed2005

Molecular cloning and sequence analysis of a cDNA encoding pituitary thyroid stimulating hormone beta-subunit of the Chinese soft-shell turtle Pelodiscus sinensis and regulation of its gene expression.

A cDNA encoding thyroid stimulating hormone beta-subunit (TSHbeta) was cloned from pituitary of the Chinese soft-shell turtle, Pelodiscus sinensis, and its regulation of mRNA expression was investigated for the first time in reptile. The Chinese soft-shell turtle TSHbeta cDNA was cloned from pituitary RNA by reverse transcription and polymerase chain reaction (RT-PCR), and rapid amplification cDNA end (RACE) methods. The Chinese soft-shell turtle TSHbeta cDNA consists of 580-bp nucleotides, including 67-bp nucleotides of 5'-untranslated region (UTR), 402-bp of the open reading frame, and 97-bp of 3'-UTR followed by a 14 poly (A) trait. It encodes a precursor protein molecule of 133 amino acids with a putative signal peptide of 19 amino acids and a putative mature protein of 114 amino acids. The number and position of 12 cysteine residues, presumably forming six disulfide bonds, one putative asparagine-linked glycosylation site, and six proline residues that are found at positions for changing the backbone direction of the protein have been conserved in the turtle as in other vertebrate groups. The deduced amino acid sequence of the Chinese soft-shell turtle TSHbeta mature protein shares identities of 82-83% with birds, 71-72% with mammals, 49-57% with amphibians, and 44-61% with fish. The Chinese soft-shell turtle pituitaries were incubated in vitro with synthetic TRH (TSH-releasing hormone), thyroxine and triiodothyronine at doses of 10(-10) and 10(-8)M. TRH stimulated, while thyroid hormones suppressed, TSHbeta mRNA levels in dose-related manner. The sequences of cDNA and its deduced peptide of TSHbeta as well as the regulation of its mRNA level were reported for the first time in reptile.

Amino Acid Sequence↗

PubMed2004

Effects of leptin and neuropeptide-Y on transcript levels of thyrotropin beta and common alpha subunits of rat pituitary cells in vitro.

Leptin and neuropeptide-Y (NPY) are indicated to play a role in hypothalamo-pituitary-thyroid (HPT) axis in relation to regulation of energy homeostasis mediated through acting at hypothalamic synthesis and release of thyrotropin (TSH)-releasing hormone (TRH). Whether leptin and NPY also act at pituitary level in HPT axis remains unknown. This study aimed at investigating whether or not leptin and NPY exert actions at pituitary in modulation of transcript levels of TSHbeta and the common pituitary glycoprotein hormone alpha (PGHalpha) subunits. The dispersed pituitary cells from 6 wk old male Wistar rats were incubated with or without TRH, leptin or NPY of 10(-8) M and 10(-10) M for 6 h at 37 degrees C in medium-199 under aeration of 95% O2 and 5% CO2. The mRNA levels of TSHbeta and PGHalpha subunits of the incubated cells were measured by reverse transcription-polymerase chain reaction. The results revealed that leptin stimulated, while NPY inhibited, TSHbeta mRNA levels in a dose-related manner. Both leptin and NPY increased alpha subunit mRNA levels. It is demonstrated for the first time that both leptin and NPY exert a direct action at rat pituitary affecting steady-state levels of mRNA of TSHbeta and PGHalpha subunits. The present study supports that both leptin and NPY act at the pituitary as well besides the hypothalamus in HPT axis in relation to regulation of energy homeostasis.

Analysis of Variance↗