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Biomedical subjects

P D Gupta

Publications and source records attributed to P D Gupta.

At least 37 records · Page 2Linked to original sources
PubMed1997

Changes in structural and functional properties of rat intestinal brush border membrane during starvation.

Changes in surface area of microvilli, fluidity of brush border membrane and transport of L-amino acids through intestinal epithelial cells were studied in wellfed and starved (2,4 and 6 days) rats. The surface area of microvilli per unit area of intestinal epithelial cells increased during starvation. Studies with fluoroprobes - pyrene, 1-anilinonaphthalene-8-sulphonate and 1,6-diphenyl-1,3,5-hexatriene, showed increased fluidity of brush border membrane on progressive starvation. Transport of five amino acids representing five different transport systems was studied during starvation in everted intestinal sleeves. Transport of L-proline, glycine and L-glutamic acid which represent imino, glycine and acidic systems respectively increased significantly in Na+-dependent pathway whereas transport of L-lysine representing basic system increased significantly in Na+-independent pathway during starvation.

Amino Acids↗
PubMed1997

Role of transglutaminase in keratinization of vaginal epithelial cells in oestrous cycling rats.

Aspects of the regulation of calcium dependent transglutaminase (TGase) enzyme in the terminally differentiating vaginal epithelial cells (VEC) from cycling and oestradiol primed ovariectomized (OVX) rats are described. There is a significant increase in the TGase activity and a quantitative rise in its cross-linked sigma(tau-glutamyl)lysine covalent product in the VEC of oestrus rats. A similar phenomena was also evident in the oestradiol primed OVX rats. However, in the VEC of the diestrus/unprimed OVX rats, the enzyme activity and its cross-linked product tend to be at its basal level. An increase of TGase activity in the keratinized layers of the oestrus VEC was observed. Immunohistochemical localization data parallel the biochemical measurements. These findings suggest that TGase activity may be associated with the differential status of the cell and primarily aids in the conferring structural stability and integrity to the stratified VEC. Aggregates of the keratin tonofilament bundles which are covalently cross-linked by the formation of sigma(tau-glutamyl)lysine in the oestrus vagina renders them resistant to denaturant and proteolytic treatments.

Animals↗
PubMed1997

Induction of phosphoinositide-mediated signal transduction pathway by 17 beta-oestradiol in rat vaginal epithelial cells.

In the present study, the induction of the phosphoinositide signal transduction pathway by 17 beta-oestradiol has been demonstrated in rat vaginal epithelial cells (VEC). We have shown an increase in the metabolism of phosphoinositol lipids by 3H-myoinositol incorporation as well as production of inositol phosphate in VEC in vivo and in vitro following oestradiol administration. Concomitant changes in intracellular calcium levels have also been observed under the influence of oestradiol. To rule out the effects of cytokines, parallel studies were performed using primary cultures of VEC. Oestradiol-induced calcium uptake was seen even in the presence of actinomycin D and cycloheximide which inhibit transcription and translation respectively. Calcium uptake was blocked by neomycin, an inhibitor of phosphoinositol lipid metabolism, and by the oestrogen receptor antagonist tamoxifen. Results suggest that oestradiol induces second messenger pathways in the VEC through specific receptors. Implications of these observations in cellular differentiation processes are discussed.

Animals↗
PubMed1997

Differential reduction in the expression of keratin polypeptides in human gastric carcinomas.

Phenotypic expression of keratin polypeptides is known to be dependent on various factors, one of which is malignant transformation. In this study, we compared the pattern of expression of keratin polypeptides between control and malignant gastric tissues by employing different morphological and biochemical techniques. The results indicated preferential decrease of acidic keratin polypeptides in malignant gastric tissues. The nonmalignant gastric tissues expressed four keratin polypeptides-two acidic and two basic-whereas in the gastric adenocarcinomas expression of only two basic polypeptides was observed. Marked variation of keratin expression between the control and malignant gastric tissues not only highlights its clinical value as a support to diagnosis but also elucidates the underlying changes due to malignant transformation.

Adenocarcinoma↗
PubMed1997

Responsiveness of vaginal cells to estradiol during postnatal development of rat.

Ontogeny of responsiveness to hormones is mainly regulated by the presence of receptors; their type, number, and location in the hormone target cells. Some of these parameters have been used to study the responsiveness of rat vagina to estradiol. The estrogen binding sites (EBS) in the cytosol of rat vagina are present immediately at birth, however the animal becomes responsive to the hormone only after 25 +/- 5 d of age. The authors demonstrate how the serum and tissue levels of estradiol affect the EBS in this tissue during the postnatal development of the rat. The various responses observed after a single i.p. injection of estradiol in the immature rats are explained based on the status of the binding sites for estrogen in this tissue.

Aging↗
PubMed1997

Cell death in exorbital lachrymal gland of anophthalmic mutant rat during postnatal development.

Regression in the exorbital lachrymal gland was observed in congenital blind mutant rats lacking eyeballs and optic nerves. The morphological changes during postnatal development in acinar cells of the lachrymal gland of mutant rats were compared with those of normal rats at day 13 (before the opening of the eyes), day 30 (15 days after opening of the eyes) and the adult (90 days). Atrophy of the lachrymal gland is most likely to be associated with absence of functional signals. During regression, there is a massive elimination of cells from the acini; no fibrosis or immune reaction (lymphocytic infiltration) was observed in the gland. This atrophy in the lachrymal gland of blind rats was not associated with the biochemical markers of apoptosis. Present observations indicate that cell elimination from the lachrymal gland in blind rats is a special type of apoptosis, where cell homeostasis is not required.

Animals↗
PubMed1996

Application of an eosin B dye method for estimating a wide range of proteins.

We describe a detailed procedure for estimating a wide range of proteins by the eosin B dye method. At acidic pH, eosin B binds to proteins and absorption of the protein-dye complex at 536-544 nm is proportional to the concentration of the proteins. Inorganic and organic acids are used for the assay, the optimum concentration of acid for each assay differs from acid to acid. This method provides minimal interference with commonly used compounds in protein purification and biomolecules like DNA, RNA, lipids, carbohydrates and minerals which are generally present in biological fluids. This method is applicable for estimating proteins in tissue homogenates, isolated proteins and various biological fluids.

Acids↗
PubMed1996

Keratins and skin disorders.

The epidermal keratinocytes express two major pairs of keratin polypeptides. One pair (K5/K14) expressed specifically in basal generative compartment and the other (K1/K10) expressed specifically in the differentiating suprabasal compartment. The switch in the expression of the keratins from proliferating to differentiating compartment indicates the changes that occur in the keratin filament organization which in turn influences the functional properties of the epidermis. Proper regulation of keratin gene expression and the filament organization are absolutely necessary for normal functioning of the skin. Keratin gene mutations can influence the filament integrity thereby causing several heritable blistering disorders of the skin such as epidermolysis bullosa, bullous icthyosiform erythroderma, etc. Changes in the keratin gene expression may lead to incomplete differentiation of the epidermal keratinocyte, causing hyperproliferative diseases of the skin such as psoriasis, carcinomas, etc. This review briefly describes the changes in keratin structure or gene expression that are known to result in various disorders of the skin.

Gene Expression↗
PubMed1996

Hormone-induced changes in cell shape: role of cytoskeletal proteins.

Shape is a characteristic phenotype for a given cell. It is affected by various physiological and pathological factors. Hormones, which are the chemical messengers affecting a wide range of biological phenomena, also alter cell morphology by influencing the expression and post-translational modifications of cytoskeletal proteins. The assembly/disassembly of cytoskeletal proteins and their interactions with intracellular components, the plasma membrane and extracellular matrix, is mainly responsible for determining cell shape. The role of hormones in the induction of altered cell shape due to changes in the cytoarchitecture in varied biological tissues under both in vivo and in vitro conditions, are discussed in this review.

Animals↗
PubMed1995

Modulation of apoptosis by starvation: morphological and biochemical study of rat intestinal mucosa.

Morphology at light and electron microscopic levels, expression and activation of transglutaminase and DNA fragmentation at internucleosomal sites were used as markers to study the effect of starvation on the apoptosis of small intestinal epithelial cells. The cells entering apoptotic programme in well-fed animals undergo many morphological changes in apical cytoplasm involving alterations in actin cytoskeleton organisation which may cause a discharge of microvilli. Some free floating cells in the intestinal lumen show characteristics of apoptotic cell death, e.g. shrinkage of cell and peripheral condensation of chromatin, while mitochondria and lysosomes remain unchanged. Apoptotic bodies are also seen in scanning electron micrographs. During progressive starvation, epithelial cells do not enter the apoptotic cell death programme. Biochemical markers for apoptosis such as increased transglutaminase activity and DNA fragmentation are clearly discernible in normally fed animals. The percentage of cells labelled immunohistochemically by antibody against transglutaminase decreased during starvation while DNA fragmentation was absent. The exact mechanism for suppressing apoptosis in intestinal cells under starvation is not known. However, the data presented here support the existence of such a regulatory process.

Journal Article↗
PubMed1994

Modulation of cytosolic RNase activity by endogenous RNase inhibitor in rat vaginal epithelial cells on estradiol administration.

The cytosolic, alkaline RNase in rat vaginal epithelial cells (VEC) from normal, immature rats was found to be present largely in the free, active form unlike in many other mammalian tissues where it is known to be present in a latent form as a complex with RNase inhibitor (RNasin). Estradiol (E2) administration induced expression of RNasin activity in the VEC from such animals and caused virtually total inhibition of cytosolic RNase activity in these cells by 12 h after the hormone injection. These changes may have metabolic implications in relation to other biochemical events stimulated by estradiol in rat VEC.

Animals↗
PubMed1994

Estradiol-regulated transamidation of keratins by vaginal epithelial cell transglutaminase.

We have observed a marked increase in the activity of transglutaminase (EC 2.3.2.13) in rat vaginal epithelial cells in a time-dependent manner during estradiol-induced terminal differentiation. The increased transglutaminase activity facilitates a post-translational modification, transamidation of keratins by the formation of an isopeptide sigma (tau-glutamyl) lysine. This isopeptide was recovered from the urea-soluble and -insoluble fractions of keratins. The formation of sigma (tau-glutamyl) lysine was significantly reduced in rats primed with progesterone or tamoxifen-estradiol. These in vivo experiments were further confirmed by in vitro studies using the reconstituted keratin filaments, which demonstrated a remarkable acceleration in the formation of covalent cross-links mediated by vaginal epithelial cell transglutaminase obtained from rats primed with estradiol. By specifically modifying the lysine residues of the keratins with 2,4-pentanedione the aggregation of keratin filaments was inhibited. These findings reflect that the vaginal epithelial cell transglutaminase obtained from rats which is regulated by estradiol plays a key role in the process of terminal differentiation of rat vaginal epithelial cells.

Amides↗
PubMed1994

Tampering with cytokeratin expression results in cell dysfunction.

Role of cytokeratins in early embryogenesis in Xenopus and mouse, regeneration of liver and keratinization of epithelial cells in adult animals have been worked out by manipulating RNA expression as well as protein synthesis using chemical modulators, antibodies, antisense DNAs or by transgenic expression. Irrespective of the various responses of cells/tissue to the altered keratin network system, keratins help in providing architecture and a definite cellular organisation to the tissue as a whole, by controlling morphogenetic migration of cells. The role of cytokeratins in the morphogenetic movements provides mechanical integrity and endurance to the cells.

Animals↗
PubMed1994

Association of transglutaminase with the reconstituted keratin filaments isolated from rat vaginal epithelial cells.

We report a novel association of the calcium dependent cross-linking enzyme, transglutaminase (TGase) with the urea soluble reconstituted keratin filaments (RKF) isolated from the rat vaginal epithelial cells (VEC). This was ascertained by measuring the activity using 14C-spermidine incorporation and also by an increase in keratin filament aggregation by the addition of only TGase cofactor-calcium. These events were specifically inhibited by the treatment of calcium chelator, EDTA at a concentration > 2 mM as well as by pretreating the RKF with histamine, a TGase substrate inhibitor. The association was also exemplified by immunoblotting analysis where a specific and preferential polypeptide of molecular weight 58 kDa cross-reacted with TGase antibody amongst the other keratins. This phenomenon was not seen in the keratins isolated from skin, a non-targeting tissue for estradiol action.

Actin Cytoskeleton↗
PubMed1994

Ultrastructural evidence for the presence of crystalline structures in pig vaginal epithelial cells.

Terminally differentiated intermediate layers of vaginal epithelial cells from the late follicular phase of the pig show crystalline structures. Analysis of two dimensional images by transmission electron microscopy revealed that these structures are composed of rhomboid subunits. The longer side measures 26 nm whereas the smaller side measures 24 nm. The angles between the sides are 100 degrees and 80 degrees. These structures are not associated with any cellular structures and are not evident in other phases of the oestrous cycle. Structurally, they do not match with Reinke's crystals and are probably regulated by hormones.

Animals↗
PubMed1994

Multiple roles of intermediate filaments.

The widespread distribution, diversity of types, and highly conserved features of intermediate filaments (IFs) and the diversity of associated proteins indicate multiple roles for IFs in the nucleus and the cytoplasm of eukaryotic cells. Traditional functions include maintenance of cell shape, cell locomotion, movement and positioning of organelles and guiding cell development. Recent studies indicate some of these functions can now be expanded. Currently available information shows that IFs are important to nuclear function and cell division, to transport between the nucleus and cytoplasm, to the mechanical integrity of cells and tissues, to reorganization of the cytoplasm and chromatin in response to intercellular signals, and to embryonic and cellular differentiation.

Animals↗
PubMed1994

Keratins as markers in odontogenesis--an immunocytochemical experimental study in rats.

The expression and distribution of keratins within different layers of enamel organs of embryonic and neonatal rats studied by using indirect immunoperoxidase and immunofluorescent techniques in paraffin-embedded tissues employing specific antibodies revealed Keratin positivity in odontoblastic layer, oral epithelium and dental lamina in primitive stages; other odontogenic tissues showed negative reaction.

Animals↗