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Biomedical subjects

S Sahu

Publications and source records attributed to S Sahu.

At least 55 records · Page 3Linked to original sources
PubMed1977

Lipid chemotaxins isolated from culture filtrates of Escherichia coli and from oxidized lipids.

Lipid extracts of sterile culture filtrates of Escherichia coli were shown to contain approximately 75% of the chemotactic activity for human polymorphonuclear leukocytes and rabbit alveolar macrophages. Fractionation and purification of these lipids revealed the presence of many unknown lipids of widely different properties, but all were anionic and at very low concentrations, chemotactic. The only one of active molecules that could be identified was an unsaturated ultraviolet-absorbing hydroxy fatty acid, which, following catalytic reduction with hydrogen, was found to be hydroxyeicosanoic acid. This fatty acid's chromatographic behavior was very similar to that of 12-hydroxy-5,8,10,14-eicosatetraenoic acid (HETE), which is a potent chemotaxin for polymorphonuclear leukocytes and macrophages. Unknown chemotaxins could be generated by the oxidation of known unsaturated lipids. Prostaglandins A2 and E2 produced potent chemotaxins upon aerobic oxidation. Malonaldehyde, a peroxidation product of unsaturated lipids, when reacted with phosphatidylethanolamine in aerobic conditions, also produced strong chemotactic agents. The chemotactic activity of these products could be destroyed by catalytic reduction with hydrogen and by methylation with dry methanolic HCl. These data indicate that the nonenzymatic oxidation of unsaturated lipids generates some products that are potent chemotaxins for mammalian inflammatory cells.

Animals↗
PubMed1977

Lipid composition of airway secretions from patients with asthma and patients with cystic fibrosis.

Lipids from the particulate material obtained from pulmonary lavage of patients with asthma and cystic fibrosis were isolated and characterized. In both cases, lipids constituted 30 to 40 per cent of the dry insoluble material and phosphatidylcholine was the predominant lipid. Significant amounts of phosphatidylethanolamine and phosphatidyglycerol were present. Hexosyl ceramides, spingomyelin, phosphatidylinositol, phosphatidylserine, and lyso(bis)phosphatidic acid were present as minor lipid components. Appreciable quantities of neutral lipids were also found. Significant amounts of lysophosphatides and free fatty acids were present only in the lavage sediment from patients with asthma, and not in patients with cystic fibrosis. Phosphatidylcholine, lysophosphatidycholine, sphingomyelin, and phosphatidylglycerol of asthmatic lavage, but not cystic lavage, were highly saturated, containing mostly palmitic acid.

Adolescent↗
PubMed1977

Histochemical studies on the spinal cord of the Indian buffalo (Bubalus bubalis).

The distribution pattern of glycogen, alkaline phosphatase and acid phosphatase has been studied and recorded in normal and operated spinal cord of the Indian buffalo (Bubalus bubalis). Based on the observations, the following conclusions have been arrived at i) Glycogen is present in the cytoplasm and on the surface of the spinal neurons. Following injury, it is depleted from these sites. ii) Alkaline phosphatase is located in the nucleus and on the neuronal surface. It is not traceable at these sites following spinal cord injury. iii) Acid phosphatase is mostly confined to the neuronal cytoplasm and tends to increase in injured neurons.

Acid Phosphatase↗
PubMed1976

Light-induced absorption changes in photosystem I at low temperatures.

Light-induced absorption changes associated with the primary photochemical reaction and dark relaxation in Photosystem I were measured at various low temperatures. A possible temperature-dependent long-range electron tunneling process was suggested to account for the unique temperature dependence of the dark decay process. The kinetics of the light-induced absorption changes are in good agreement with the light-induced EPR changes reported earlier (Ke, B., Sugahara, K., Shaw, E.R., Hansen, R. E., Hamilton, W. D. and Beinert, H. (1974) Biochim, Biophys. Acta 368, 401--408) for the same Photosystem I subchloroplast fragment at comparable temperatures. All absorption changes between 400 and 725 nm at 86degreesK have identical kinetics. The light-minus-dark difference spectrum is very similar to that of P-700 at room temperature, with an additional prominent positive change at 690 nm. Possible contributions by P-430 to the blue and red spectral changes were discussed. It was demonstrated that the intensity of the measuring beam has a drastic effect on the light-induced absorption changes of Photosystem I at low temperatures. Various pretreatments of the Photosystem I fragments such as those that photochemically (or chemically) oxidize the primary donor or photoreduce the primary acceptor abolish the subsequent photochemical reaction. Continuous illumination of the Photosystem I fragments before and during freezing has the same effect. In the temperature range of --20 to --60degreesC, an unusual counter absorption change as well as a counter EPR change were observed.

2,6-Dichloroindophenol↗
PubMed1976

Structural studies on a glycoprotein isolated from alveoli of patients with alveolar proteinosis.

A major glycoprotein 36 000 molecular weight) has been isolated from lung lavage of patients with alveolar proteinosis and found to contain five residues of hydroxyproline, fifty residues of glycine, three residues of methionine, 3 mol of sialic acid, 4.4 mol of mannose, 4.0 mol of galactose, 6.0 mol of glucosamine, and 1 mol of fucose. Cyanogen bromide (CNBr) treatment of the glycoprotein resulted, as expected, in four peptides of apparent molecular weights of 18 000, 12 000, 5000 and 1000, respectively. The chemical compositions of the CNBr peptides indicate the presence of hydroxyproline and high amounts of glycine in all but one of the peptides; two of the four CNBr peptides contain carbohydrate. Gel filtration, acrylamide gel electrophoresis and end-group analyses of the native glycoprotein and its CNBr peptides indicate that the peptides are homogeneous. End-group analyses of the CNBr cleavage products assign the 18 000 molecular weight peptide to the NH2-terminal portion and the 1000 molecular weight peptide to the COOH-terminal portion of the native glycoprotein molecule. Pronase digestion of the 36 000 molecular weight glycoprotein, followed by gel filtration and cation exchange chromatography, resulted in two fractions. One fraction was acidic and contained all the carbohydrate, a high content of aspartic acid and no hydroxyproline. The other fraction was basic and contained 8.4% hydroxyproline, 14% proline, 28% glycine and no carbohydrate, suggesting the presence of collagen-like sequence in the peptide chain. Paper electrophoresis of the basic fraction demonstrated two components, the amino acid compositions of which are identical to those of collagen. Partial amino-terminal sequence analysis of one of the CNBr peptides (18 000 molecular weight) indicated the presence of -Fly-Pro-HyP-Gly-sequence in the peptide chain, which confirms our suggestion that collagen-like regions are present in the native glycoprotein molecule. Limited acid hydrolysis of the acidic fraction and subsequent fractionation of the acid hydrolysate using Dowex column yielded a fraction which produced brown colour with ninhydrin reagent. Paper chromatography of this fraction demonstrated a large component which also stained brown with ninhydrin reagent. After acid hydrolysis, this component was found to consist of equal amounts of asparitic acid and glucosamine, indicating that the N-acetylglucosamine of the oligosaccharides is linked to the asparagine residue of the peptide. No serine or threonine linkages are present.

Amino Acids↗
PubMed1976

Redox titration of fluorescence yield of photosystem II.

The variable fluorescence yield of photosystem II is dependent on the redox state of the fluorescence quencher molecule or the primary electron acceptor of the system. We have carried out redox titrations of fluorescence yield of a photochemically active photosystem-II reaction-center particle and have measured the redox potential of the photosystem-II primary acceptor.During reductive titrations using dithionite as the reductant, only a single quenching transition was observed. For instance, at pH 7.0, the midpoint potential of the fluorescence transition is -325 mV, and those at a pH between 6.0 and 7.5 are consistent with a pH dependence of about 60 mV/pH unit. At a given pH, the midpoint potential of the transition closely corresponds to that of the most negative transition previously measured in unfractionated chloroplasts (both by chemical reductive titration). Oxidative titrations using ferricyanide as the oxidant yielded hysteresis in the titration curves.Similar changes in fluorescence yield were observed in redox titrations by electrochemical reduction or oxidation. Electrochemical reductive and oxidative titrations yielded reversible transitions, contrary to the hysteresis observed during chemical oxidative titration. From coulometric-titration data, we have estimated that most likely one electron is involved in the redox transition of the fluorescence-quencher or primary-electron-acceptor molecule of photosystem II. These findings are consistent with the current proposal that a membrane-bound plastoquinone functions as the primary acceptor of photosystem II.

Journal Article↗
PubMed1976

Lipids found in pulmonary lavage of patients with alveolar proteinosis and in rabbit lung lamellar organelles.

Lipids from the insoluble material obtained by pulmonary lavage of 6 patients with alveolar proteinosis and from lamellar organelles of normal rabbit lungs were isolated and characterized. In both types of samples, dipalmitoylphosphatidylcholine was the predominant lipid. Phosphatidylethanolamine, phosphatidylglycerol, lysophosphatidylglycerol, and 2 glycolipids, GM3 and GL1 were also present in both types of preparations. Sphingomyelin, lysophosphatidylcholine, lysophosphatidylethanolamine, phosphatidyl-N, N-dimethylethanolamine, phosphatidylserine, and lyso(bis)phosphatidic acid were found in the sedimented lavage material from humans but were not detected in lamellar organelles from rabbits. Significant quantities of neutral lipids were present in the lavage material, but only trace amounts, mainly as cholesterol and triglycerides, were detected in lamellar organelles. Phosphatidylcholine and the 2 glycolipids contained mostly saturated fatty acids and essentially no polyunsaturated fatty acids. Sphingomyelin, lysophosphatidycholine, and phosphatidyl-N, N-dimethylethanolamine, found only in the lavage, were also highly saturated. In addition to the fact that several phospholipids found in the lavage were not present in lamellar organelles, another striking difference between the lipids from these 2 sources was that phosphatidylglycerol of lamellar organelles contained predominantly palmitic acid, whereas the phosphatidylglycerol obtained by lavage of humans contained large amounts of stearic and oleic acids.

Animals↗
PubMed1975

Crosslinking and carbohydrate studies on the hydroxylated glycopeptides which accumulate in alveoli and lamellar bodies.

These data suggest that the alveolar lining layer and lamellar body membranes contain the same saline-insoluble proteins, two of which are unusual in that they contain hydroxyproline and large amounts of glycine. Neither the function nor the origin of these glycopeptides has been established, and we are currently evaluating methods of stimulating their production in animals for further study.

Animals↗
PubMed1972

Quantum accumulation in photosynthetic oxygen evolution.

Three independent methods have been used to determine the size of the quantum accumulation unit in green plant photosynthesis. This unit is defined as that group of pigment molecules within which quantal absorption acts must take place leading to the evolution of a single O(2) molecule. All three methods take advantage of the nonlinearity of oxygen yield with light dose at very low dosages. The experimental values of this unit size, based on an assumed model for the charge cooperation in O(2) evolution, ranging from 800 to 1600, suggest that there is either limited energy transfer between energy-trapping units or chemical cooperation among oxygen precursors formed in several neighboring energy-trapping units. Widely diffusible essential precursors to molecular oxygen are ruled out by these results. Inhibition studies show that O(2) evolution is blocked when 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) is added to chloroplasts after two preliminary flashes and before a third flash which would have yielded O(2) in the absence of DCMU. This experiment is interpreted as evidence that the site of DCMU inhibition is on the oxidizing side of system II. Pretreatment of chloroplasts with large concentrations of Tris, previously believed to destroy O(2) evolution by blocking an essential reaction in the electron chain between water and system II, may be alternately interpreted as promoting the dark reversal of the system II light-induced electron transfer.

Chloroplasts↗