Biomedical subjects

S Dasgupta

Publications and source records attributed to S Dasgupta.

At least 127 records · Page 7Linked to original sources

PubMed1991

The Escherichia coli cell cycle: one cycle or multiple independent processes that are co-ordinated?

In the life cycle of a bacterium there are several key processes: cellular growth, chromosome replication and decatenation, nucleoid partition, septum formation, and cell division. These processes have to be carefully controlled and co-ordinated both with respect to each other and to the growth of the cell, and could be viewed as parts of a single cycle in which each step is dependent upon the previous one. Alternatively, they could be independently controlled and carefully tuned to each other without actually constituting a true cycle. In this review, using Escherichia coli as model system, we discuss these two ways of describing the bacterial life cycle. The evidence supporting independent control of the processes is presented, and some of the key questions in the elucidation of the regulation of the bacterial life cycle are discussed.

Biological Evolution↗

PubMed1991

Herpes simplex virus type 1-specific cytotoxic T lymphocytes recognize immediate-early protein ICP27.

The identity of herpes simplex virus type 1 (HSV-1) antigens that serve as targets for cytotoxic T lymphocytes (CTL) and their ability to induce protective immunity remain uncertain. In this article, we report the identification of the immediate-early protein ICP27 as a CTL antigen in H-2d mice but not in H-2k or H-2b mice. Calculation of the frequencies of H-2d-restricted virus-specific CTL demonstrated that approximately one-fourth of the total HSV-1-specific response was directed against ICP27. To define the location of this CTL epitope, four truncated derivatives of the ICP27 gene which place the epitope in a 217-amino-acid region (amino acids 189 to 406) near the central portion of the protein were constructed. Mice immunized with ICP27 were able both to induce HSV-1-specific CTL and to survive a lethal intraperitoneal challenge with virulent HSV-1. However, neither appreciable antibody nor delayed-type hypersensitivity responses were induced in immunized mice, and they were also unable to clear a local epithelial virus challenge. It appears that ICP27, although capable of inducing several aspects of the immune response, is by itself unable to provide complete immunity.

Animals↗

PubMed1991

Characterization of 2S seed storage protein of Brassica campestris and its antigenic homology with seed proteins of other Cruciferae.

The low molecular weight seed storage protein of Brassica campestris has been isolated and its amino acid composition determined. Antibody raised against this low molecular weight protein has been used to compare the antigenic similarity between the low molecular weight storage proteins of different Cruciferae seeds by immunoprecipitation and Western blotting. These studies revealed the existence of antigenically homologous proteins of identical molecular weights in seeds of other Cruciferae but absent in some other dicots like mung bean and tobacco seeds.

Amino Acids↗

PubMed1991

A disialoganglioside of the globo-series from chicken skeletal muscle.

We have isolated a disialoganglioside of the globo-series from chicken pectoral muscle. The compound was obtained by extraction followed by ion-exchange and silicic acid column chromatography and judged to be pure by thin-layer chromatography in three solvent systems. The structure of the ganglioside was determined by carbohydrate and ceramide composition analysis, sequential exoglycosidase digestion, methylation analysis, and 500-MHz 1H-NMR spectroscopy to be: (formula; see text) Analysis of the ceramide moiety indicated d18:1 sphingosine as the long-chain base, and C16:0, C18:0, C18:1, and C20:0 as the prevalent fatty acids. This glycolipid is only the second ganglioside of the globo-series, and the first disialo member of the series, found in chicken muscle.

Animals↗

PubMed1990

Biosynthesis of GM1b and similar neolactoseries gangliosides by a partially purified chicken skeletal muscle sialyltransferase. Effect of sphingomyelin and acetylcholine.

An alpha 2----3 glycolipid galactosyl sialyltransferase (SAT3/4) has been partially purified from embryonic chicken skeletal muscle. It is preserved in 50 mM Hepes buffer (pH 6.8) containing 1% Triton CF-54 and 20% glycerol at -70 degrees C for a period of 6 months without loss of activity. The SAT3+4 preparation transfers sialic acid to nLcOse4Cer, nLcOse6Cer and GgOse4Cer with respective Km values of 1.4, 0.83 and 0.45 mM. The activity is stimulated 2-3-fold at high substrate concentration and 6-8-fold at low substrate concentration; 0.01 and 0.005 mumol for asialo GM1 and 0.025 and 0.01 mumol for other glycolipids in the presence of phosphatidylcholine (PC) and sphingomyelin (SM) at an optimum concentration 0.75%. A higher concentration is inhibitory. SM from chicken muscle is more effective than that from bovine brain and the stimulation is qualitatively proportional to that of the saturated fatty acyl content of SM. Free fatty acids (palmitic and stearic), their sodium salts, other choline compounds including choline chloride, phosphorylcholine and acetylcholine either do not have any effect or are inhibitory. Acetylcholine, even in the presence of SM and PC, is strongly inhibitory (70%).

Acetylcholine↗

PubMed1990

Regulation of the calcium-activated neutral proteinase (CANP) of bovine brain by myelin lipids.

Since calcium-activated neutral proteinase (CANP; calpain) activation occurs at the plasmalemma and the enzyme is found in myelin, we examined myelin lipid activation of brain CANP. Purified lipids were dried, sonicated and incubated with purified myelin CANP. The CANP was assayed using [14C]azocasein as substrate and the Ca2+ concentration ranged from 2 microM for muCANP to 5 mM for mCANP. Phosphatidylinositol (PI), phosphatidylserine (PS) and dioleoylglycerol stimulated the mCANP activity by 193, 89 and 78%, respectively. PI stimulated both m- and muCANP in a concentration-dependent manner, while phosphatidylcholine was least effective. Cerebroside and sulfatide at higher concentrations (750 microM) were stimulatory. The phospholipid (PL)-mediated activation was inhibited by the PL-binding drug trifluoperazine. PI reduced the Ca2+ requirement for CANPs significantly (20-fold). These results suggest that acidic lipids and particularly acidic phospholipids activate membrane CANP.

Animals↗

PubMed1990

Ganglioside-modulated proteolysis by Ca2(+)-activated neutral proteinase (CANP): a role of glycoconjugates in CANP regulation.

We examined ganglioside modulation of the activity of the millimolar Ca2(+)-sensitive form (mCANP) of calcium-activated neutral proteinase (CANP), which is enriched in myelin, from brain. GM1, GD1a, GT1a, GM2, and GM4 produced a concentration-dependent increase of mCANP activity. GD1a stimulated the greatest increase of enzyme activity (107%), followed by GT1a, whereas GD1b was inhibitory (56%). GM1, GM2, and GM4 stimulated but less so than GD1a and GT1a. Free N-acetylneuraminic acid, asialo-GM1, GM3, and a ganglioside mixture containing GM1, GD3, GD1a, and GD1b had no effect. The ganglioside-mediated modulation was not affected by trifluoperazine and chlorpromazine (phospholipid-binding antagonists). The mCANP Ca2+ requirement was significantly reduced in the presence of stimulatory gangliosides, and this increased sensitivity varied (10-50-fold) with ganglioside structure. Gangliosides may interact with membrane mCANP and modulate its proteolytic action.

Animals↗

PubMed1990

The predicted amino acid sequence of a centrosphere protein in dividing sea urchin eggs is similar to elongation factor (EF-1 alpha).

Monoclonal antibody (SU5), prepared from isolated mitotic spindles of sea urchin eggs, stained centrospheres preferentially and recognized a 50K (K = 10(3) Mr) polypeptide on immunoblots. Three positive clones were isolated by screening a lambda gt11 cDNA expression library prepared from sea urchin egg mRNA with SU5. One clone containing a 1.8-kb (1 kb = 10(3) base-pairs) insert was selected for further characterization. The beta-galactosidase fusion protein encoded by the cDNA clone had an apparent relative molecular mass of 150K, indicating that the inserted cDNA produced an estimated 34K of polypeptide. A single 2.2-kb RNA transcript was detected in sea urchin embryos using the cDNA clone as a probe. The cDNA fragment was sequenced and the nucleotide sequence was used to predict the amino acid sequence of the open reading frames in the clone. The putative gene product shows striking similarity to the peptide chain elongation factor (EF-1 alpha) from yeast, fungus, shrimp, insect, mouse and human.

Amino Acid Sequence↗

PubMed1990

Pediatric ocular trauma--a clinical presentation.

A year long study of ocular injuries in children below the age of 15 years was conducted in the Ophthalmology Department of a general hospital. Fortyfour cases were studied. Of these 45.45% were in the age group of 6-10 years. The male to female ratio was 5.28 : 1. Pointed objects viz. sticks, wires etc. were found to be the common causative agents; the recent trend being of bow and arrow injuries. Ocular perforation was observed in 28 cases. On follow up of all the cases with ocular trauma, only 12 patients were found to have a visual acuity better than 6/18; perception of light was absent in 7 patients. A need for increased parental awareness and supervision of children is stressed upon.

Adolescent↗

PubMed1990

Management of a case of lagophthalmos by Gillies' method (a case report).

A case of facial palsy with lagophthalmos with exposure keratitis was corrected surgically by a method of temporalis transfer. When the slings were tightened leaving 1 cm gap in the palpebral aperture, lagophthalmos persisted. A secondary tightening procedure causing overlap of the upper lid over the lower yielded good results.

Eyelid Diseases↗

PubMed1989

Cytochrome c oxidase: evidence for interaction of water molecules with cytochrome a.

The resonance Raman spectra of cytochrome c oxidase in protonated buffer compared to that in deuterated buffer indicate that water molecules are near the heme of cytochrome a. Differences in widths of the heme line at 1610 cm-1, after short exposure to D2O, and, additionally, of the heme line at 1625 cm-1, after long exposure, can be accounted for by changes in resonance vibrational energy transfer between modes of cytochrome a2+ and the bending mode of water molecules in the heme pocket. On the basis of the assignment of these modes, we place one water molecule near the vinyl group and one water molecule near the formyl group of the cytochrome a heme. These water molecules may play several possible functional roles.

Animals↗

PubMed1989

Structural characterization of cytochrome c peroxidase by resonance Raman scattering.

Resonance Raman scattering studies are reported on freshly prepared and aged ferric, ligand-free ferrous, and CO-bound ferrous cytochrome c peroxidase. The ferric form of the fresh enzyme has a heme which is penta-coordinate high spin, independent of buffer over the pH range 4.3-7, as determined by well established Raman marker lines. The aged enzyme displays a mixture of spin and coordination states, but it can be stabilized in the penta-coordinate high spin form in the presence of phosphate. These results can be accounted for by considering the size of the channel (6 A wide, 11 A long) between the distal side of the heme and the outer surface of the protein. A phosphate ion may be accommodated in this channel resulting in the stabilization of the distal heme pocket. The ferrous cytochrome c peroxidase in both the ligand-free and CO-bound states has an acidic and an alkaline form. The acidic form has the characteristic spectral features of peroxidases: a high frequency iron-histidine stretching mode (248 cm-1), a high frequency Fe-CO stretching mode (537 cm-1), and a low frequency C-O stretching mode (1922 cm-1). At alkaline pH these frequencies become similar to those of hemoglobin and myoglobin, with the corresponding modes located at 227, 510, and 1948 cm-1, respectively. We attribute the acid/alkaline transition in the ferrous forms of cytochrome c peroxidase to a rearrangement mainly of the proximal side of the heme, culminating in a change of steric interactions between the proximal histidine and the heme or of the hydrogen bonding network involving the proximal histidine. The new data presented here reconcile many inconsistencies reported in the past.

Buffers↗

PubMed1989

Sialylation of lacto-N-neotetraosyl ceramide by a solubilized sialyltransferase(s) from chicken skeletal muscle: effect of phosphatidylcholine and sphingomyelin.

The sialytransferase(s) that transfers sialic acid to lacto-N-neotetraosylceramide and other glycosphingolipids with a galactose nonreducing terminus has been successfully solubilized from embryonic chicken skeletal muscle. The enzyme can be stored in 50 mM HEPES (pH 6.8), 1% Triton CF-54, and 20% glycerol at -70 degrees C for as long as six months. Addition of phosphatidylcholine or sphingomyelin (0.167%) readily reactivates the stored inactive enzymes and such activity persists for about two weeks at 0 degrees-4 degrees C with the peak activity occurring at 1 to 2 days. Sphingomyelin from chicken muscle, which contains mainly C16:0 and C18:0, is 2.1-fold more effective than bovine brain sphingomyelin at the same concentration (0.4%).

Animals↗

PubMed1988

Selective devascularisation of stomach and lienopulmopexy for prevention of bleedings in portal hypertension in children.

Dissatisfied with different operative procedures for prevention of recurrent bleedings in childhood portal hypertension, many surgeons nowadays treat their patients conservatively during episodic attacks and advocate one of the shunt procedures in adolescence when the splenic vein becomes sufficiently widened (more than 1 cm). Even then mortality cannot be avoided in some bad risk patients especially those living in remote villages lacking facilities for blood transfusion and high speed transport service. In this situation thoracic transposition of spleen and lienopulmopexy was advocated by Nylander and Turumen, Auvert, M. Bettex and others. We prefer a further simpler procedure and perform selective devascularisation of stomach and lienopulmopexy. It allows rapid development of collaterals between splenic pulps on the portal side and subpleural venous plexus on the systemic side to achieve effective gastric devascularisation to prevent further bleeding without hindering the existing portal flow through the liver to avoid the possible occurrence of encephalopathy. Of 21 operated cases one died on the 5th postoperative day and the remaining 20 are doing well. 1/2-5 1/2 years' follow-up revealed negligible morbidity and no recurrence of bleeding in any of them. Both procedures work on the same principle.

Child↗

PubMed1988

The role of water near cytochrome a in cytochrome c oxidase.

Resonance Raman scattering studies of cytochrome c oxidase reveal that two vibrational modes narrow upon placing the enzyme in D2O. This is interpreted as evidence for the presence of water molecules near cytochrome a that increase the linewidth of the heme modes due to resonance vibrational energy transfer to the H2O bending mode. From the nature of the modes in which the broadening is detected, it is deduced that the water molecules are located near the formyl and the vinyl substituents of the cytochrome a. The change in width in the formyl mode appears quickly, whereas that in the vinyl mode only develops after extended exposure of the enzyme to D2O. On the basis of these results we propose a new mechanism for proton translocation. In this hypothesis water molecules at the active site become activated and are dissociated into protons and hydroxyl groups due to changes in the pKas of residues near the heme when the redox state of the cytochrome a changes. Structural features of the protein stabilize this charge separation and allow directional migration of protons to the cytosolic side of the inner mitochondrial membrane. It is pointed out that this mechanism may be operative in all proton-translocation complexes, and it is observed that in bacteriorhodopsin, also a proton pump, water molecules are detected near the active site lending support to the generality of this mechanism.

Animals↗

PubMed1988

Tissue ascorbate as a metabolic marker in cadmium toxicity.

Daily subcutaneous injection of cadmium chloride for two weeks to normal and protein restricted rats show significant increase in the wet weight of liver, kidney, adrenal and decrease in pituitary, testis and thyroid, while no significant changes are observed in the brain. The concentration of ascorbic acid (AA) decreased significantly in plasma, liver, kidney, spleen, adrenal, pituitary and brain but increased in testis and thyroid whereas no significant alteration was observed in the pancreas after cadmium treatment in both the dietary regimen. It is apparent that cadmium causes the alteration of AA in different tissues/organs of the body in normal protein dietary state which is further potentiated in protein restricted condition. During stress, the metabolism of different tissues responds differentially as far as their AA concentration is concerned. Therefore the alteration of AA level in the different tissues/organs might have some correlation with the extent of cadmium toxicity.

Adrenal Glands↗

PubMed1988

Effect of combined contraceptive steroid on rat brain ascorbate-acetylcholine with reference to protein restriction.

To evaluate the effects of combined contraceptive steroids on brain ascorbic acid and acetylcholine during protein restriction with respect to normal dietary condition the rats were subjected to normal (18% casein) and protein restricted (5% casein) diet for 28 days. Subsequently they were treated with combined contraceptive steroids for 28 days. Smear study were performed throughout the periods of dietary regimen and the drug treatment. Ascorbic acid and acetylcholine concentration of six discrete regions of brain were estimated from all groups of rats. At normal dietary state the combined contraceptive steroids significantly increase the ascorbic acid and decrease the acetylcholine concentration in the brain areas. At this state diestrus phase was indicated by smear study. After steroid treatment during protein restriction significant decrease of ascorbic acid and significant increase of acetylcholine concentration occurred in the brain areas. Proestrus and estrus phases were continued as indicated by smear study. It may therefore be presumed that contraceptive steroids affect the brain regional ascorbic acid and acetylcholine in an opposite manner during normal and protein restricted dietary condition.

Acetylcholine↗

PubMed1988

Relationship between central cholinergic and GABAergic neurotransmitters activity in the steroid treated rat.

Contraceptive steroid treatment to female rat alters the concentration of acetylcholine and gamma-aminobutyric acid, though not uniformly in most of the brain areas, i.e. in cerebellum, medulla oblongata-pons, hypothalamus, striatum-hippocampus, midbrain-thalamus-subthalamus, and cortex. Both neutrotransmitters vary conjointly in the hypothalamus and striatum-hippocampus after combined steroid treatment. This may indicate a concerted effect on the modulation of gonadotrophin release.

Acetylcholine↗