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Biomedical subjects

B R Singh

Publications and source records attributed to B R Singh.

At least 91 records · Page 5Linked to original sources
PubMed1988

Molecular topography of toxic shock syndrome toxin 1 as revealed by spectroscopic studies.

Molecular characterization of toxic shock syndrome toxin 1 has been carried out and compared with a group of functionally related staphylococcal enterotoxins. The secondary structure analysis of the far-UV circular dichroic spectrum of toxic shock syndrome toxin 1 revealed 6.25% alpha-helix, 51.25% beta-pleated sheets, 9.0% beta-turns, and 33.5% random coils. The pattern, in general, was similar to the staphylococcal enterotoxins. Four antigenic sites have been predicted for toxic shock syndrome toxin 1 by using the secondary structure information in combination with the hydrophilicity calculation. The location of the antigenic sites, in general, agrees with the experimental results. Topographical analysis of the tyrosine residues as determined by second-derivative UV spectroscopy [Ragone, R., Colonna, G., Balestrieri, C., Servillo, L., & Irace, G. (1984) Biochemistry 23, 1871-1875] showed that six of nine tyrosine residues are exposed to aqueous solvent. Tryptophan fluorescence quenching studies with an anionic surface quencher, I-, and a neutral quencher, acrylamide, revealed that almost all of the tryptophan residues are buried in the protein matrix as their accessibility to the surface quencher is very low (17%). Since there are only three tryptophan residues in the amino acid sequence of the toxic shock syndrome toxin 1 and there is a tyrosine residue (Tyr-15, Tyr-115, and Tyr-153) next to each of the tryptophan residues (Trp-14, Trp-116, and Trp-154), it appears the tyrosine residues not exposed to the aqueous solvent are those next to the tryptophan residues. Functional implications of the topography of the tryptophan and tyrosine residues are assessed.

Bacterial Toxins↗
PubMed1988

Structural analysis of staphylococcal enterotoxins B and C1 using circular dichroism and fluorescence spectroscopy.

Secondary and tertiary structural parameters of two functionally and serologically related proteins, staphylococcal enterotoxins B and C1, have been determined by using circular dichroism and fluorescence spectroscopy. The secondary structures derived from the respective far-UV circular dichroic spectra were 9.5% alpha-helix, 55.0% beta-pleated sheets, 16.5% beta-turns, and 19.0% random coils for enterotoxin B and 15.0% alpha-helix, 38.0% beta-pleated sheets, 25.5% beta-turns, and 21.5% random coils for staphylococcal enterotoxin C1. The values matched well with the secondary structures derived from the amino acid sequences (Chou and Fasman method). Seven antigenic sites have been predicted for both staphylococcal enterotoxins B and C1 by using the hydrophilicity and the secondary structure information. Three of these antigenic sites appear similar. Fluorescence quantum yield of the single tryptophan residue (Trp-197) of both the enterotoxins showed the tryptophan residue in staphylococcal enterotoxin B to be approximately 46% more fluorescent than in staphylococcal enterotoxin C1. Tryptophan fluorescence quenching by the surface quencher I- and the neutral quencher acrylamide revealed that the single tryptophan residue in each of the enterotoxins is buried in the protein matrix and is not accessible to the surface quencher I-. The tryptophan residue in staphylococcal enterotoxin C1 is 14% less accessible to acrylamide than in staphylococcal enterotoxin B. The data, in general, reflect several similarities and significant differences between the two related enterotoxins.

Amino Acid Sequence↗
PubMed1987

Purification and spectroscopic properties of 124-kDa oat phytochrome.

A simplified procedure for the isolation and purification of 124-kDa phytochrome from etiolated Avena seedlings has been developed using the method of ammonium sulfate back-extraction. After hydroxyapatite chromatography of seedling tissue extracts, the pooled phytochrome was subjected to ammonium sulfate back-extraction instead of the usual application to an Affi-Gel Blue column. The resulting phytochrome had specific absorbance ratios (SAR = A666/A280) ranging from 0.85 to 0.95. Subsequent Bio-Gel filtration chromatography yielded highly pure 124-kDa phytochrome with SAR values ranging from 0.99 to 1.13. The absorption maxima of 124-kDa phytochrome were at 280, 379, and 666 nm for the red absorbing form of phytochrome (Pr) and at 280, 400 and 730 nm for the far-red absorbing form (Pfr). The A730/A673 ratio in Pfr was found to be 1.5 to 1.6. The mole fraction of Pfr under red light photoequilibrium was 0.88. No dark reversion was detected within 5 h at 3 degrees C. A photoreversible far-uv-circular dichroism was observable with all phytochrome preparations examined. Fluorescence and phosphorescence lifetimes were measured to further characterize the differences between the phytochromes prepared under different conditions. The Trp fluorescence and phosphorescence lifetimes of Pr and Pfr with the chromophore "X", probably polyphenolic in nature, were significantly shorter than those of phytochrome without the contaminant X. The short lifetime of the fluorescence of the Pr chromophore is attributable to X in the former.

Circular Dichroism↗
PubMed1979

Oxygen uptake capacity of the amphibious fish - Amphipnous cuchia (Ham) (Symbranchiformes, Amphipnoidae).

The O2 uptake capacity of Amphipnous cuchia has been determined in relation to standard temperature of 25 degrees C. The measurement of O2 uptake indicates nearly 75% of the oxygen demand to be met through the air breathing organs and 25% by the skin and vestigeal gill through water in a normal habitat. The total VO2 during aerial-aquatic gas exchange is 60.5 ml/kg/hr. The prevention of surfacing resulted in a lower O2 uptake rate (38.29 ml/kg/hr). During submergence, the utilisation of air sacs for extracting O2 by regular pumping of water in and out is peculiar to the fish. Under normal respiratory conditions (air + water), the slope for O2 uptake through air is 0.72, 0.23 for water and 0.57 for both air + water. The average ratio borne by the fish for aquatic/air breathing (ml/kg/min) is higher in fishes below 60 g body weight, and aquatic respiration predominates in fishes weighing less than 6.0 g.

Animals↗
PubMed1976

Changes in the blood parameters of an air-breathing fish during different respiratory conditions.

Some of the blood parameters recorded in an air-breathing eel, Amphipnous cuchia under normal respiratory condition during non-breeding period (September-April) are haemoglobin (Hb) concentration 19.26%, haematocrit value 56.16%, RBC number 1.71 million/mm3, RBC size 18.86 X 9.70 mum, mean corpuscular haemoglobin (MCH) 113.4 ng, mean corpuscular haemoglobin concentration (MCHC) 34.2%, blood sugar 77 mg% and ascorbic acid 0.435 mg%. The higher concentration of haemoglobin (19.26%) appears to be related to its obligatory air breathing habit and habitat in a water of low oxygen content. Though a definite trend of increase in the haemoglobin and haematocrit concentration with an increase in the body weight of the fish was lacking, variations were clearly marked related to intrinsic activity of the fish connected with different respiratory conditions. Asphyxiation in a submerged but continuous flow of water (liter/h) for 5 1/2 h resulted in an increase in the above-mentioned parameters to an appreciable extent. These increases were 0.23 million/mm3 in the number of erythrocytes, 6.16% in haemoglobin concentration, 10% in haematocrit value, 20% in blood sugar and 35% in ascorbic acid content. The mean corpuscular haemoglobin showed a decline of 6.2%. Exclusive aerial breathing for 5 1/2 h also caused 7.4% increase in haemoglobin concentration, 9.4% in haematocrit value, 0.14 million/mm3 in RBC number, 20% in blood sugar level, 9% in ascorbic acid content but almost no change in mean corpuscular haemoglobin. The average surface area for diffusion of gases appeared to have reduced by 6.8 mum2 per RBC.

Animals↗
PubMed1975

A histochemical study on the respiratory epithelium of an eel fish - Amphipnous cuchia (Ham).

The respiratory epithelium of the air sac and that of the buccal cavity resemble each other in having high vascularization, very small air/blood pathway (below 1 mum), phospholipid, ascorbic acid content and having two morphologically distinct mucous cells. The larger mucous cells appear to secrete strongly acidic sulfated mucopolysaccharides while the smaller ones are responsible for secreting sialic acid containing glycoproteins. Elongated mucous cells with foamy cytoplasm and tapering apex of the vascularised buccal epithelium are similar in histochemical properties to the same type of mucous cells reported in the epidermis of the skin. These cells secrete weakly acid mucopolysaccharides. Negligible number of mucous cells are present along the margin of the fused gill filaments of the gill. Presence of large amount of scattered phospholipid globules in the respiratory epithelium appears to be true of all the air breathing fishes utilising oxygen from air. Foreceful water or air breathing for nearly 5 1/2 h by the fish does not indicate change of phospholipid content of the respiratory epithelium but prevention of surfacing a continuous flow of water system resulted in 35% increase in blood ascorbic acid and more concentration of vitamin C granules along the respiratory epithelium.

Air Sacs↗
PubMed1975

On the muscular fuel of the air sac in an air breathing fish.

The hyohyoideus muscle which is responsible for inflating and contracting the air sac in an air breathing fish, Amphipnous cuchia, belongs to white fibre type as it lacks muscle myoglobin. The muscle shows appreciable amount of glycogen and extracellular phospholipid globules. Staining of I bands in the muscle fibres with Alcian blue (1.0 less than or equal to pH less than or equal to 3.0) indicates presence of acid mucosubstances. The muscle does not show change in phospholipid content at the histochemical level but lowering of glycogen content (25 to 30%) when put to 51/2h of continuted physiological exercise. At the same time, increase in blood sugar level (20 to 30%) possibly indicates utilization of glycogen as the source of energy by the muscle. However, a clear cut priority of glycogen or phospholipid break down for energy source by the muscle could not be established.

Animals↗
PubMed1975

Effect of ACTH and bilateral gonadectomy on the adrenocortical tissue of an air-breathing fish -- Heteropneustes fossilis (Bloch).

The mammalian ACTH (20 I.U.) injected in Heteropneustes fossilis (Bloch) caused hyperplasia of the adrenocortical tissue. The interrenal as well as chrome cells became vacuolated. The interrenal nuclear size increased by 15% as an average than the control fishes. The glycogen granules were found to be absent from the interrenal cells. The effect of bilateral gonadectomy in both sexes has been marked in the gradual decrease of the interrenal nuclear diameter which 12 weeks after the operation, recorded nearly 25% reduction in size. The glycogen content was reduced considerably. Removal of gonads during maturation period bringing inhibition of hyperplasia of the gland at the time of spawning possibly indicates action of gonadal steroids on the physiological alterations of the interrenal cells.

Adrenal Cortex↗