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Biomedical subjects

S Pillai

Publications and source records attributed to S Pillai.

At least 127 records · Page 7Linked to original sources
PubMed1988

Biochemical and morphological characterization of growth and differentiation of normal human neonatal keratinocytes in a serum-free medium.

Growth and differentiation of keratinocytes in a serum-free medium (keratinocyte growth medium or KGM) was studied and compared to that under conditions in which serum and feeder cell layers were used. Cells were grown in KGM containing 0.1 mM calcium (KGM/low calcium), KGM containing 1.2 mM calcium (KGM/normal calcium), or Dulbecco's modified Eagles medium containing 5% fetal calf serum and 1.8 mM calcium in presence of mitomycin treated 3T3 M cells (DMEM/5% FCS). Plating efficiency and rate of growth were similar in the three media till confluence. In postconfluent cultures, protein and DNA content of cells attached to the plate in KGM/low-calcium dishes decreased as an increased number of cells were shed into the medium. Cell shedding was much less evident in the presence of normal calcium. Cells grown in KGM/low calcium had a higher rate of cell proliferation (3H-thymidine incorporation into cellular DNA) than cells grown in normal calcium. Transglutaminase activity, involucrin content, and cornified envelope formation were greatest in cells grown in KGM/normal calcium, intermediate in cells grown in DMEM/5% FCS, and least in cells grown in KGM/low calcium. Keratin profiles from cells grown in KGM/low calcium showed a lower percentage of high molecular weight bands compared to the keratin profiles from cells grown in the presence of normal calcium. Keratinocytes in KGM/low calcium grew as a monolayer of cuboidal cells with few features of differentiation, whereas cells grown in KGM/normal calcium stratified into multilayered islands (3-5 layers) surmounted by 2-4 layers of enucleated cells with thickened cornified envelopes. Cells grown in KGM/normal calcium also contained tonofilaments and lamellar bodies unlike cells grown in KGM/low calcium. Cells grown in DMEM/5% FCS also formed stratified layers comparable to cells grown in KGM/normal calcium but lacked cornified cells, keratohyalin granules, tonofilament bundles, and lamellar bodies. These studies indicate the usefulness of serum-free conditions for the culture of human keratinocytes and confirm the importance of extracellular calcium in keratinocyte differentiation.

Cell Differentiation↗
PubMed1988

Vitamin D and epidermal differentiation: evidence for a role of endogenously produced vitamin D metabolites in keratinocyte differentiation.

Vitamin D3 is produced in the skin. It is metabolized primarily in the liver to the major circulating form 25-hydroxy vitamin D3, [25(OH)D3] which is metabolized in the kidney to produce the biologically active form of the hormone, 1,25-dihydroxy vitamin D3, [1,25(OH)2D3]. The skin not only participates in the production of vitamin D3 but also contains receptors for 1,25(OH)2D3 suggesting a role of this hormone in the growth and differentiation of this tissue. 1,25(OH)2D3 appears to play a role in epidermopoiesis and melanin pigmentation. Recently, using cultures of neonatal human foreskin keratinocytes, we have demonstrated that these cells produce abundant quantities of 1,25(OH)2D3 from 25(OH)D3. The production of 1,25(OH)2D3 varies with the degree of differentiation of keratinocytes and is regulated by exogenous 1,25(OH)2D3. 1,25(OH)2D3 induces differentiation possibly because of its ability to increase intracellular free calcium levels. A tentative model is provided to demonstrate potential mechanisms by which 1,25(OH)2D3-induced changes in intracellular calcium could regulate epidermal differentiation.

Animals↗
PubMed1988

Relationship of steroid dose to degree of posterior subcapsular cataracts in nephrotic syndrome.

Forty-five patients with nephrotic syndrome were included in our study. Of these, 30 received adrenocorticosteroid therapy and 15 did not. The ages of the patients ranged from 11 months to 27 years and the duration of steroid therapy from 2 1/2 years to 20 years. Seventeen patients (38%) showed posterior subcapsular cataract (PSC) formation and, of these, seven patients (41%) showed reversal of PSC. There was no statistical correlation between the total dose of steroids and the degree of PSC. An individual susceptibility may be an important factor in the production of PSC. None of the patients had visual acuity less than 20/30.

Adolescent↗
PubMed1988

Transient lenticular opacification following trabeculectomy.

Permanent lens changes may occur following filtering procedures for glaucoma, most often within a few years after the surgery. We present a case in which transient lenticular opacification occurred two days after trabeculectomy without intraoperative injury to the lens. The patient regained her preoperative vision 2 weeks postoperatively. We postulate that such reversible lenticular opacities may be due to changes in lens metabolism associated with hypotony.

Adolescent↗
PubMed1987

The effect of vitamin D status on cutaneous sterologenesis in vivo and in vitro.

Recent studies have shown that cutaneous sterologenesis is autonomous from the influence of circulating sterols, and that the epidermis is an important site of sterologenesis which is regulated by permeability barrier requirements. In addition to barrier function, an additional, important function of the epidermis is to synthesize sterol precursors of vitamin D3. The present study was designed, first, to determine whether vitamin D status and/or circulating levels of 1,25-dihydroxyvitamin D3 might play a role in regulating cutaneous sterol synthesis in vivo and, second, whether 1,25-dihydroxyvitamin D3 modulates sterologenesis in cultured human keratinocytes. Hairless mice were maintained on a vitamin D-deficient diet in the dark and supplemented with various doses of vitamin D3/day. Despite demonstrating serum 25-hydroxyvitamin D3 levels ranging from less than 10 to 343 ng/ml, the incorporation of tritiated water into cholesterol and total nonsaponifiable lipids in both the epidermis and dermis was similar in the four groups of animals. Likewise, administration of various doses of 1,25-dihydroxyvitamin D3 to vitamin D-deficient mice resulted in serum levels of 1,25-dihydroxyvitamin D3 ranging from less than 10 to 85 pg/ml; yet, cholesterol and total nonsaponifiable lipid synthesis was similar in both the dermis and epidermis in all groups of animals. Moreover, administration of 0.6 micrograms/kg per day of 1,25-dihydroxyvitamin D3 to 'normal' vitamin D-replete mice also had no effect on cutaneous sterol synthesis. Furthermore, conversion of 7-dehydrocholesterol to cholesterol in vitamin D-deficient vs. supplemented animals did not differ. Finally, addition of 1,25-dihydroxyvitamin D3 to cultured keratinocytes over a concentration range of 10(-12)-10(-7) M did not affect sterologenesis, except at supraphysiologic doses (10(-7) M). Together, these results suggest that vitamin D status does not influence sterol synthesis in the skin.

Animals↗
PubMed1987

Myristoylation and the post-translational acquisition of hydrophobicity by the membrane immunoglobulin heavy-chain polypeptide in B lymphocytes.

Membrane immunoglobulin heavy chain in pre-B and in B cells is initially synthesized as a relatively hydrophilic protein that is nonetheless stably anchored in the endoplasmic reticulum membrane. In B cells, but not in pre-B cells, the membrane immunoglobulin heavy chain is post-translationally converted to a relatively hydrophobic form that partitions into the oil phase when solubilized with the phase-separating detergent Triton X-114. Covalent myristoylation of the membrane and secretory forms of immunoglobulin heavy chains as well as of light chains was observed in B cells. Myristoylation of the membrane immunoglobulin heavy chain correlates with its transport to the cell surface and its post-translational conversion to a relatively hydrophobic form. This post-translational modification is hydroxylamine resistant and may be responsible for the assembly and transport of membrane immunoglobulin to the cell surface in B cells.

Animals↗
PubMed1987

Complete evulsion of the globe and optic nerve.

A 17-year-old boy had an evulsion of globe and optic nerve from an automobile accident. Computed tomography showed a severed optic nerve on the injured side. A visual field defect was demonstrated in the other eye.

Accidents, Traffic↗
PubMed1986

Production of biologically active fragments of parathyroid hormone by isolated Kupffer cells.

Cleavage of parathyroid hormone (PTH) by isolated Kupffer cells from rat liver was examined. Iodinated PTH labeled at position 43 was converted into two radioactive fragments which were shown by Edman degradation to have residues 35 and 38 as their NH2 termini. Cleavage at these positions is characteristic of cathepsin D. Amino-terminal fragments were detected by bioassay of fractions obtained by high performance liquid chromatography. These fragments eluted in positions characteristic of the 1-34 and 1-37 peptides also previously shown to be produced by purified cathepsin D. The putative 1-37 fragment was rapidly converted to 1-34 upon digestion with cathepsin D, whereas the putative 1-34 fragment was not further digested by this enzyme, behavior previously shown to be characteristic of 1-37 and 1-34 bovine PTH. Fragmentation of PTH as measured by generation of fragments soluble in trichloroacetic acid was inhibited by methylamine, monensin, and ammonium chloride. In addition, monensin significantly inhibited production of both carboxyl- and amino-terminal fragments. Finally, active PTH fragments were also produced by elicited peritoneal macrophages. It is concluded that Kupffer cells, and other macrophages, can produce active fragments of PTH which appear in the medium. These fragments may be generated by cathepsin D within the cells.

Adenylyl Cyclases↗
PubMed1985

ATP activation of protein degradation by extracts of crude and purified lysosomal preparations.

Activation of proteolysis by ATP was studied in lysates of crude and purified lysosomal preparations from liver and kidney at acid pH. In the crude system, from kidney, it was found that ATP activates proteolysis over a concentration range of 0.1-2 mM. Up to 4-fold activation was observed. GTP and CTP also activated proteolysis, but to a lesser extent. Proteolysis was inhibited by vanadate and molybdate. Fractionation of the kidney lysosomes on Percoll gradients produced two fractions containing lysosomal marker enzymes. Most of the acid phosphatase and the acid pyrophosphatase were found in the lighter band, while most of the beta-galactosidase and cathepsin activity was found in a more dense band. Proteolysis by lysates of both fractions was activated by ATP and inhibited by vanadate and molybdate. In the dense band proteolysis was also nearly totally blocked by pepstatin, and was enhanced by an inhibitor of pyrophosphatases, sodium fluoride. ATP also activates proteolysis in crude lysosomes from liver, but upon fractionation of this tissue it was found that all the lysosomal enzyme markers are present in the dense fraction obtained from the Percoll gradient. Again, proteolysis by lysates of the purified fractions was activated by ATP and inhibited by vanadate and molybdate. These data indicate that ATP can activate proteolysis at acid pH in a lysosomal milieu containing enzymes which also catalyze its breakdown. In the kidney there may be two lysosomal compartments which separate the enzymes catalyzing ATP breakdown from the proteolytic enzymes, but this is not essential for ATP activation as shown by the data from the liver and the crude lysosomal fractions.

Adenosine Diphosphate↗
PubMed1985

Effects of ATP, vanadate, and molybdate on cathepsin D-catalyzed proteolysis.

The effects of ATP, vanadate, and molybdate on cathepsin D-catalyzed hydrolysis of proteins and peptides were examined. Hydrolysis of bovine serum albumin, hemoglobin, parathyroid hormone, and a synthetic octapeptide was activated by ATP. Degradation of the protein substrates all had similar ATP concentration dependence, but the magnitude of the activation varied. Kinetic constants for ATP activation were obtained with a synthetic substrate. ATP increased kcat from 0.4 to 2 s-1 but did not change KM. Kact for ATP was 800 microM. Studies with pepstatin-Sepharose confirm that ATP does not alter the substrate binding site on cathepsin D. Pepsin, a homologous aspartate protease, was not activated by ATP. It was also found that vanadate and molybdate inhibit cathepsin D-catalyzed proteolysis. However, this inhibition was dramatically dependent on substrate concentration and was eliminated at high substrate. Hydrolysis of the synthetic peptide was not inhibited at concentrations of molybdate below 50 microM, and above this concentration the peptide precipitated. Protein substrates were also found to precipitate in the presence of molybdate. The ATP dependence of the enzyme was not altered by molybdate or vanadate. These results suggest that inhibition by vanadate and molybdate is related to interactions with the substrate rather than with cathepsin D. It is concluded that ATP activation of cathepsin D may play a physiological role in regulation of proteolysis in lysosomes, but that vanadate and molybdate inhibition of lysosomal proteolysis does not establish ATP dependence.

Adenosine Triphosphate↗
PubMed1985

Decreased prolactin secretion in childhood obesity.

Twelve obese patients and 7 control subjects, age and sex matched, whose weights were greater than 200% of ideal weight and 100% of ideal body weight, respectively, underwent intravenous insulin and thyroid releasing hormone (TRH) tests. Serial prolactin growth hormone, insulin, blood sugar, cortisol, glucagon, thyrotropin stimulating hormone, thyroxine, and triiodothyronine were obtained by RIA. Obese patients showed no significant differences from controls in basal and nadir glucose, basal and peak glucagon, cortisol, and thyroid responses to both tests. Basal insulin levels were higher (36 +/- 9.4 vs 10 +/- 2.3 microU/ml, P less than 0.05) and peak growth hormone responses after insulin were lower in the obese group (6.1 +/- 1.1 vs 12.7 +/- 3.7 ng/ml, P less than 0.05) than in controls. Whereas all control subjects had prolactin responses to both tests, five of 12 obese patients had no responses to insulin. Obese patients had lower prolactin responses at 30 minutes after insulin (5.4 +/- 0.7 vs 12.9 +/- 3.7 ng/ml, P less than 0.05) and lower prolactin responses at 60 minutes after TRH (9.9 +/- 1.7 vs 20.4 +/- 5.9 ng/ml, P less than 0.05). Maximum prolactin responses after TRH were lower in obese patients (9.9 +/- 2.0 vs 28.8 +/- 10.9 ng/ml, P less than 0.05). Maximum prolactin responses after insulin were lower in obese patients (6.2 +/- 4.1 vs 28.9 +/- 18.3 ng/ml). Thus prolactin secretion in childhood obesity is decreased after both stimuli, but more so after IV insulin that TRH, and suggests that, as in adult hypothalamic obesity, neuroendocrine regulation of prolactin release in obese children is impaired.

Adolescent↗
PubMed1985

The effects of vanadate and molybdate on cathepsin D; relationship to ATP activation of lysosomal proteolysis.

The effects of the phosphate analogues, vanadate and molybdate, on the ATP-activated enzyme, cathepsin D, were investigated. Both were found to inhibit proteolysis but this appeared to be the result of non-specific interactions with the protein substrates which result in precipitation, rather than interactions with the enzyme. Inhibition of proteolysis was induced by the same concentration of inhibitors as that which induced precipitation (measured by turbidity), and was dependent on the concentration of substrate. Precipitation did not occur at neutral pH but was maximal below pH 5. High concentrations of salt (greater than 1M KC1) prevented precipitation of proteins by vanadate and molybdate and under these conditions little inhibition of proteolysis was observed even at high inhibitor concentrations. Nonetheless, ATP was found to activate proteolysis catalyzed directly by lysosomal enzymes at acid pH, while vanadate and molybdate inhibited proteolysis in this system and induced precipitation of substrate. These results indicate that inhibition of proteolysis at acid pH by vanadate (or molybdate) has no relationship to inhibition of proteases and/or ATP dependence of such enzymes. However, direct activation of cathepsin D in lysosomes by ATP remains a viable hypothesis.

Adenosine Triphosphate↗
PubMed1983

ATP activation of parathyroid hormone cleavage catalyzed by cathepsin D from bovine kidney.

The acid protease which is activated by ATP and which catalyzes production of fragments of parathyroid hormone similar to those produced in vivo was shown to be cathepsin D. Purified cathepsin D from bovine kidney and spleen is activated by ATP and other nucleoside triphosphates, and to a much lesser extent by nucleoside diphosphates and pyrophosphate. These findings suggest that cathepsin D may be involved in parathyroid hormone metabolism in vivo and that this lysosomal enzyme may be regulated by the energy status of the cell.

Adenosine Triphosphate↗
PubMed1983

Sulfated glycosaminoglycans synthesized by fibroblast, smooth muscle and endothelium-like cells grown in culture.

Monolayer cultures of fibroblast, smooth muscle and endothelium-like cells incorporated 35SO2-(4) into glycosaminoglycans of the extracellular, pericellular and intracellular compartments. These glycosaminoglycans have been identified on the basis of electrophoretic mobility, enzymatic degradation with specific mucopolysaccharidases and by the type of degradation products formed. The sulfated glycosaminoglycans from the extracellular pool of the three cell types show a similar composition, while the intracellular and pericellular pools of the three cells have a different glycosaminoglycans composition. They differ in the relative proportion of heparitin sulfate and chondroitin sulfate and in the structure of isomeric chondroitin sulfate.

Animals↗