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Biomedical subjects

M Bagchi

Publications and source records attributed to M Bagchi.

At least 109 records · Page 6Linked to original sources
PubMed1992

Preconditioning of heart by repeated stunning: adaptive modification of myocardial lipid membrane.

Recent studies indicate that preconditioning of a heart by repeated stunning protects it from subsequent ischemic injury. Such myocardial preservation is likely to be due to adaptive modification of lipid composition and dynamic structure of cellular membrane. To test this hypothesis, swine heart was subjected to four episodes of 5 min stunning by LAD occlusion, followed by 10 min of reperfusion after each stunning. Heart was then made regionally ischemic for 60 min by LAD occlusion, followed by 6 h reperfusion. Control heart was perfused for 60 min, followed by 60 min ischemia and 6 h reperfusion. Free fatty acids (FFA) accumulated in control heart during ischemia as expected, which was further enhanced by reperfusion. The FFA level was also enhanced during ischemia in stunned myocardium. However, this FFA level was almost restored during reperfusion. The levels of polyunsaturated fatty acids (PUFA) such as oleate, linoleate, and arachidonate followed a similar pattern. Membrane fluidity, monitored by fluorescence polarization, was decreased during ischemia and reperfusion in the unstunned heart, with the corresponding increase in microviscosity. The increased microviscosity was significantly reduced by stunning. Since FFA are presumably generated from membrane phospholipids, these results suggest that stunning may cause the incorporation of a greater proportion of PUFA in membrane phospholipids, leading to preservation of membrane phospholipids and maintaining the membrane fluidity, which may be at least partially responsible for the attenuation of ischemic reperfusion injury.

Adaptation, Physiological↗
PubMed1991

Phosphorylation of small molecular weight polypeptides in the iris-ciliary complex, aqueous humor and vitreous humor.

The polypeptides of vitreous humor, aqueous humor and iris-ciliary complex cells of eyes were phosphorylated with [gamma-32P]ATP without exogenous protein kinase. Phosphorylated polypeptides were analyzed by sodium dodecyl sulfate gel electrophoresis and autoradiography. The phosphorylated polypeptides of rabbit vitreous humor showed many high molecular weight prominent bands, but no detectable phosphoproteins were found in the 12 kDa or lower range. Bovine vitreous humor has predominantly acidic polypeptides and some of them are below 20 kDa. Rabbit and bovine iris-ciliary complex and rabbit aqueous humor showed a prominent common 4 kDa phosphopolypeptide which could also be synthesized by cloned populations of cells from the bovine iris and the rabbit iris-ciliary body. It is possible that the 4 kDa phosphopolypeptide of the aqueous humor is synthesized by the iris-ciliary complex cells.

Adenosine Triphosphate↗
PubMed1991

Studies on the possible role of vitreous humor on protein synthesis and morphology of organ cultured adult rabbit lens. II. Epithelial cells.

The protein synthetic activities of epithelial cells of lenses organ-cultured without adhered vitreous humor manifest significant increase compared to the epithelial cells of lenses incubated with attached vitreous humor. This effect is not due to trauma of vitreous removal, as the addition of freeze-dried vitreous humor to the culture medium of lenses without attached vitreous humor could inhibit protein synthesis. However, the protein synthesis inhibitor in the vitreous humor has no visible effect on the lens morphology. It was also found that the factor from vitreous humor has no effect on mRNA production or cell-free protein synthesis. Thus, it seems that the effect on protein synthesis must be mediated via some other pathway.

Animals↗
PubMed1991

Effect of vitreous humor on the organ cultured rabbit ocular lens. III. Morphology and elemental analysis.

Distribution of ions and volume regulation of epithelial cells of lenses cultured in the presence and absence of vitreous humor were examined. Ion levels of the epithelial cells were measured using energy dispersive x-ray analysis(EDX) and computer-assisted morphometry was used for volume measurements. Data from these experiments revealed that the epithelial cells in the pre-equatorial region of lenses cultured without attached vitreous humor are larger and have significantly altered ionic balance. The cell volumes and ionic balances of central epithelial cells of the lenses cultured without attached vitreous humor also displayed discernible changes. However, overall data indicated that the epithelial cells in the pre-equatorial regions of the lenses are most susceptible to the effects of vitreous humor. Experiments performed in our laboratory have demonstrated that vitreous humor contains some factor(s) which can effectively inhibit protein synthesis. It was also reported that this factor(s) is not a direct inhibitor of protein synthesis. Therefore it was assumed that the inhibition of protein synthetic activity was mediated via some other pathway. One of these possible routes could be altered cytoplasmic ion fluxes. Earlier we reported that the ion levels of the lenses cultured with or without adhered vitreous humor were similar. Ion levels were measured from intact lenses. It is possible that there were regional differences in ion levels, which could be masked in whole lenses. It is also known that the epithelial cells are major participant in ion-pump activity, whereas cortical and nuclear areas of the lens may not contribute significantly to the ion transport. It has also been proposed that the epithelial cells of the pre-equatorial region are the main site of the Na+, K+ pump. Variation in ion levels of the epithelial cells could also affect protein synthesis activities of the lens. To test these possibilities, experiments were performed to measure ion levels in various areas of the lenses by energy dispersive x-ray analysis techniques. Altered cytoplasmic ion level can also change the volumes of the epithelial cells. This possibility was investigated by employing computer-assisted morphometry in measurements of two- and three-dimensional parameters of the lens epithelial cells and capsule.

Animals↗
PubMed1991

The effects of iris-ciliary complex on the organ cultured rabbit ocular lens.

Freshly isolated rabbit lenses were cultured with and without attached iris-ciliary (IC)-complex for 24 hours in TC-199 medium. Subsequent morphological analysis revealed that the IC-complex cannot be maintained in serum-free medium. In addition an observed effect of the IC-complex on the co-cultured lenses could not be due only because of the cellular degeneration of the IC-complex. To test this possibility lenses with attached IC-complexes were incubated in 20% serum-containing TC-199 medium. The IC-complex cultured in 20% serum containing medium retained its normal morphology. However co-cultured lens cells displayed vacuoles and other signs of degeneration. The protein synthetic and Na+/K+ pump activities of these lenses were also significantly depressed. These data indicated that the observed effects of IC-complex on the lens were not due to its cellular degradation. Preliminary experiments showed that the IC-complex contains water soluble factor(s) which could effectively inhibit lens protein synthesis and Na+/K+ pump.

Animals↗
PubMed1991

Elemental profiles in Emory mouse lens.

Energy dispersive x-ray microprobe analysis was used to determine the distribution of chloride, potassium, phosphorus and sulfur in the epithelial cells of the lenses obtained from 3 to 7 month old Emory mice and 7 month old cataract resistant strain of Emory mice. Rapidly frozen lenses were fractured in the frozen state and lyophilized. The anterior epithelial cells were analyzed from equator to equator. The results show that the epithelial cells of the 7 month old Emory mouse lens have considerably higher amounts of chloride, sulfur, potassium and phosphorus. Presence of increased amount of potassium in the epithelial cells is intriguing. The data obtained from these experiments show that the changes in the elemental levels of epithelial cells are similar to observed alteration found in the lens fiber mass of 7 month old Emory mouse.

Animals↗
PubMed1989

Effects of free radicals on the fluidity of myocardial membranes.

Free radicals, including superoxide anions (O2.-), hydroxyl radical (HO.), and hypohalite radical (OCl.), as well as oxidants such as hydrogen peroxide (H2O2) and hypochlorous acid (HOCl), have been indicated in the pathogenesis of myocardial ischemic and reperfusion injury. In this report, we compared the integrity of the myocardial membrane when exposed to these free radicals/oxidants. Isolated rat heart membrane preparations were exposed to chemically generated free radicals with or without their respective scavengers. Membrane fluidity was monitored by fluorescence polarization using the diphenylhexatriene probe, as well as by electron spin resonance (ESR) spectroscopy using 2,2,6,6-tetramethyl piperidine-n-oxyl as the spin labeling agent. HO., H2O2, and OCl. + HOCl increased the fluorescence polarization (FP) and microviscosity significantly by 1.7-fold, 1.8-fold, and 1.7-fold, respectively, as compared to an only 1.2-fold increase in FP by O2.-. O2.- did not alter the fatty acid profiles of the membrane phospholipids. However, HO. and H2O2 reduced the arachidonic acid contents in phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylinositol (PI). These radicals also stimulated the lipid peroxidation by several-fold, while that by O2.- was only insignificant. These results suggest that HO. and H2O2 decreased the membrane fluidity and induced lipid peroxidation by releasing the arachidonic acid from PC, PE, and PI.

Animals↗
PubMed1989

Elemental and structural studies of the rat galactose cataract.

A series of rat galactose lenses, from 1 to 20 days on the 50% galactose diet, were frozen in the whole eye, and fractured from pole to pole in the frozen state. Lyophilized half-lenses were prepared for analysis by energy dispersive spectrometry (EDS). Following elemental analysis, some specimens were embedded and sectioned for histological studies. Elemental X-ray maps, and/or profiles, were made for K, Na, Cl, Ca, P, and S. As early as two days on the galactose diet, a crescent-shaped region ("streak") of Cl, Na, and Ca gain, and K loss develops near the equatorial surface. Between this region and the equatorial surface are the nucleated differentiating fiber cells which maintain low Cl, Na, and Ca, and high K (viable equatorial zone, VEZ). With time the "streak" expands anteriorly, centrally and posteriorly, eventually (by 20 days) including most of the lens. The VEZ, including the epithelium, however, is non-reactive to the galactose diet, which is deleterious to the fully differentiated fiber cells. Eventually, the VEZ undergoes a characteristic morphological change, apparently due in part to changes in its physical environment.

Animals↗
PubMed1989

Studies on the possible role of vitreous humor on the protein synthesis and clarity of the organ cultured ocular lens.

Contralateral lenses were organ cultured with or without attached vitreous humor (VH) for up to two days. The lenses without attached VH showed significantly higher rate of protein synthesis. This increase was not only due to the trauma of vitreous stripping, since lenses without attached VH, but co-cultured with VH, showed protein synthetic activity similar to that of lenses with attached VH. The removal of VH from lenses does not significantly alter Na+/K+ balance of the lenses, although these lenses showed slight equatorial opacities. It was also found that freeze dried VH can inhibit lens protein synthesis, indicating VH contains some water soluble molecule with protein synthesis inhibitory activity.

Animals↗
PubMed1989

Steroid-induced myocardial preservation is associated with decreased cell membrane microviscosity.

Reperfusion of ischemic myocardium is associated with phospholipid degradation and corresponding changes in membrane fluidity. Dexamethasone (1.25 mg/kg i.v.) was evaluated in the pig, with pretreatment of the animal 1 1/2 hours before ischemic insult. The isolated perfused in vivo pig heart model was subjected to 60 minutes of regional ischemia of the left anterior descending coronary artery. The ischemic heart was then subjected to 60 minutes of global hypothermic cardioplegic arrest followed by 60 minutes of reperfusion, including reperfusion of the ischemic left anterior descending coronary artery region. Phospholipase A2, arachidonic acid, total free fatty acids, myocardial microviscosity, coronary blood flow, myocardial oxygen consumption, creatine kinase release, and regional and global myocardial function were measured. Dexamethasone pretreatment resulted in dramatic inhibition of phospholipase A2 activity accompanied by a reduction in arachidonic acid and total free fatty acid levels. Myocardial microviscosity (the inverse of membrane fluidity) was significantly increased only in untreated animals. Coronary blood flow and myocardial oxygen consumption were maintained at preischemic levels only in the dexamethasone-treated animals and were significantly reduced in the control group. Creatine kinase release increased nearly six times in control animals only while remaining stable in the dexamethasone-treated group, and regional and global myocardial contractility and compliance were improved dramatically in the dexamethasone-treated animals. These results indicate that dexamethasone enhances myocardial function by preserving membrane structure through inhibition of phospholipase activation, thereby preventing phospholipid degradation and maintaining membrane integrity and fluidity.

Animals↗
PubMed1988

The role of the iris-ciliary complex in the control of protein synthesis by the organ cultured rabbit ocular lens.

When freshly isolated rabbit lenses were co-cultured with iris-ciliary body (IC), the protein synthetic activity of these lenses decreased significantly. The inhibitory effect is temporal as longer incubation showed greater inhibition. it was also found that the presence of IC in the culture medium increases the sodium ion levels in the lenses and causes some decrease in the potassium ion levels. Both the protein synthetic activity and cation levels of the lenses cocultured with IC are at least partially reversible. It seems that the IC-derived factor(s) has a molecular weight of more than 1 kDa. It is not clear from these experiments whether the altered cation balance is responsible for the inhibition of the protein synthesis.

Animals↗
PubMed1988

Study of experimental cataract produced by sugar alcohols in the organ-cultured mammalian ocular lens.

Freshly isolated rabbit lenses were cultured in isosmolar TC-199 medium or hyperosmolar medium containing 180 mM sorbitol or mannitol. These experiments were performed to investigate the probable effects of hyperosmolar media on lens clarity and the ability of lens fiber cells to synthesize membrane intrinsic protein, MP-26. The data from these experiments show that incubation in hyperosmolar medium causes depressed MP-26 synthesis, whereas the presence of sugar alcohols in the culture medium induced anterior and posterior subcapsular opacities. The cation levels of lenses incubated in iso- and hyperosmolar medium were also measured. Data from these experiments revealed that although the experimental lenses display prominent opacities, their cation levels are generally similar to those of control lenses. It is proposed that the observed lens opacities are due to the presence of sugar alcohols in the culture medium and not to hyperosmolar shock.

Animals↗
PubMed1987

Iris-ciliary complex inhibits protein synthesis by organ cultured mammalian ocular lens cells.

Freshly isolated rabbit ocular lenses with or without adhering iris-ciliary complex were organ cultured. It was found that lenses with iris-ciliary complex showed decreased protein synthetic ability. Vimentin, a cytoskeletal protein and MP-26, a membrane associated protein, were used as markers for protein synthetic activity. Removal of the iris-ciliary complex at least partially restores the protein synthetic capability of the lens. The ocular lenses cultured with iris-ciliary complex for 48 hr showed marked equatorial opacities.

Animals↗
PubMed1986

An intrinsic membrane glycoprotein of the lens.

A major glycoprotein of relative molecular weight of 130,000 daltons of chick lens cell membranes was identified by Concanavalin-A staining and enriched for by Con A-Sepharose chromatography. Using both Con A binding and immunological analyses with a specific polyclonal antibody, the glycoprotein was detected in chick lens epithelium, annular pad, cortex and nucleus. Localization to the plasma membranes of lens cells was demonstrated by immunofluorescence. A similar protein, which cross-reacts with the antibody to the chick protein and also binds Con A was demonstrated in human and bovine lenses.

Animals↗
PubMed1985

Effect of hyperosmolar medium on the protein synthesis and morphology of epithelial cells of the cultured rabbit lens.

The effects of hyperosmolar medium on the lens epithelial cell protein synthesis and morphology were studied. It was found that the hyperosmolar medium inhibits protein synthesis, and the high molecular weight proteins were more susceptible to the osmolar shock than were the low molecular weight proteins. Fine structure analysis of the epithelial cells of the lenses incubated in hyperosmolar medium showed that the osmolar shock caused a reduction in the amount of rough endoplasmic reticulum and polysomes; some chromosome clumping was also evident. Whether the morphological changes observed were directly related to the decrease in the rate of protein synthesis is not clear.

Animals↗
PubMed1985

Vimentin synthesis by ocular lens cells.

A study of the synthesis of the intermediate filament protein, vimentin, is reported here. The following systems were examined: the epithelial cells of the organ-cultured rabbit lens, the epithelial and cortical fiber cells of the organ-cultured adult chicken lens and the epithelial cells of the rabbit lens grown in tissue culture. Vimentin is actively synthesized by all of the above mentioned cells.

Animals↗