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Biomedical subjects

A Singh

Publications and source records attributed to A Singh.

At least 631 records · Page 35Linked to original sources
PubMed1988

Phase characteristics of positional isomers of 1,2-di(heptacosadiynoyl)-sn-glycero-3-phosphocholine; tubule-forming phosphatidylcholines.

We have examined the phase behavior of positional isomers of a polymerizable diacetylenic phospholipid, 1,2-di(heptacosadiynoyl)-sn-glycero-3-phosphocholine which has the diacetylene in varying position along the acyl chains. Upon cooling multilamellar vesicles (MLVs) through the liquid-crystalline to gel phase transition, all isomers examined spontaneously formed hollow, cylindrical microstructures (or tubules). Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FTIR) have been used to characterize positional isomers of this lipid in an effort to understand the effect of diacetylenic position on the molecular characteristics of tubule formation. Calorimetric results indicate that moving the position of the diacetylene along the acyl chain results in the alternation of the exotherm observed for the hydrated transition temperature associated with tubule formation, with higher transition temperatures (Tm) observed from isomers with an even number of methylenes between the diacetylene groups and the glycerol backbone. As the diacetylene is moved toward either end of the acyl chain, even with the observed alternation, the Tm was observed to increase. Calorimetric results of dry members of this series reveal an exotherm during cooling, the same temperature at which fully hydrated samples form tubules. This suggests that there is little difference in the phase behavior observed upon cooling the hydrated tubules and the dry diacetylenic material. FTIR results support the high degree of conformational order observed in tubules of this isomer series as a very strong CH2 wagging progression is observed between 1375 and 1200 cm-1. In addition, the C-H stretch region (3000 cm-1 to 2800 cm-1) indicates tight acyl chain packing with many all-trans segments. These results provide further evidence that tubules are uniquely crystalline microstructures and that this inherent crystallinity, and the formation of tubules is not affected by diacetylenic position.

Calorimetry, Differential Scanning↗
PubMed1988

Structure of a novel human granulocyte peptide with anti-ACTH activity.

We report the purification, structure and biological properties of a peptide of novel sequence from human granulocytes that inhibits ACTH stimulated synthesis of corticosterone in rat adrenal cell suspensions. The peptide HP-4 is homologous to a previously described human granulocyte peptide HP-1 that has no anti-ACTH activity.

Adrenal Glands↗
PubMed1988

Changes in nutrient intakes of conditioned men during a 5-day period of increased physical activity and other stresses.

Nutrient intakes and selected blood and urinary constituents of 16 Navy servicemen were obtained before and during a period of 113 hours of physical activity, sleep deprivation, and psychological stress, to document the dietary adaptation of physically conditioned men to an extended period of hard physical work and other stresses. Food intakes were monitored by 1-day diet records prior to and by direct observation during the period. The factorial method was used to calculate energy expenditure. Carbohydrates provided 45 and 43% of the total energy intake before and during the experiment. Protein intakes and intakes of all the vitamins and minerals studied exceeded the Recommended Dietary Allowances, both before and during the period. Total energy intake averaged 18.7 MJ.d-1 before and 24.4 MJ.d-1 during the experiment. Body weight increased significantly by 2.7 +/- 0.4 kg (mean +/- s.e.) during the experiment (p less than 0.0001). There was a significant correlation (r = 0.74; p less than 0.001) between the change in body weight and urinary sodium from before to after the experiment suggesting that increased dietary sodium may have contributed to the weight gain. A significant increase in plasma volume (11.9 +/- 3.2%; p less than 0.0003) provided further support that the observed weight gain was due to sodium intake rather than a positive energy balance. In conclusion, conditioned men increased food consumption adequately to meet increased energy demands.

Adult↗
PubMed1988

Differential scanning calorimetric study of the thermotropic phase behavior of a polymerizable, tubule-forming lipid.

A comparative study of the polymorphism exhibited by the polymerizable, tubule-forming phospholipid 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3- phosphocholine (DC23PC) and its saturated analog 1,2-ditricosanoyl-sn-glycero-3-phosphocholine (DTPC) in aqueous suspension is reported. Differential scanning calorimetry (DSC), as well as freeze-fracture electron microscopy and Raman spectroscopy, have been used to study the influence on phase behavior of rigid diacetylene groups in the fatty acyl chains of a phosphatidylcholine. DTPC large multilamellar vesicle (MLV) and small unilamellar vesicle (SUV) suspensions were found to retain liposome morphology after chain crystallization had occurred. In marked contrast, diacetylenic DC23PC suspensions do not maintain liposomal morphology in converting to the low temperature phase. Large MLVs of DC23PC with outer diameters in excess of 1 micron convert to a gel phase with cylindrical or tubular morphology at 38 degrees C, just a few degrees below the lipid's chain melting temperature (TM(H), i.e. temperature of an endothermic event observed during a heating scan) of 43.1 degrees C. Unlike the large MLVs, small MLVs or SUVs of DC23PC, with diameters of 0.4 +/- 0.3 micron and 0.04 +/- 0.02 micron, respectively, exhibit metastability in the liquid-crystalline state for several tens of degrees below the chain melting temperature prior to converting to a gel phase which, by electron microscopy, manifests itself as extended multilamellar sheets. Raman data collected at TM(H) -40 degrees C demonstrate that the gel state formed by DC23PC is very highly ordered relative to that of DTPC, suggesting that special chain packing requirements are responsible for the novel phase behavior of DC23PC.

Calorimetry, Differential Scanning↗
PubMed1988

Cystine calculi: clinical management and in vitro observations.

Although cystine stones account for 1 to 3 per cent of renal calculi, many of these patients are difficult to manage because of recurrent urolithiasis. Seven cases of homozygous cystinuria are summarized. The evolution to the present treatment of percutaneous extraction and chemolysis appears to be the preferred form of treatment although extracorporeal shock wave lithotripsy (ESWL) may also be utilized. In addition, in vitro experiments were conducted to study the effectiveness of different chelating agents and buffers at different urinary pHs. The effect of cystinuric and noncystinuric urines was also evaluated.

Acetylcysteine↗
PubMed1988

Effect of sodium lauryl sulphate and nickel alone and in combination on the skin of guinea pigs.

Guinea pig skin was treated with 50 mg/kg sodium lauryl sulphate (SLS) and nickel (Ni) alone and in combination (50 mg/kg SLS and 50 mg/kg Ni) for 7 and 14 days. Release of acid phosphatase, alkaline phosphatase, aspartate aminotransferase, alanine aminotransferase, beta-glucuronidase, lactic dehydrogenase and malic dehydrogenase was observed, following treatment with SLS and Ni alone or in combination. Similarly, the skin contents of amino nitrogen and sulphydryl groups also increased significantly. These alterations were slightly more marked when the skin was treated simultaneously with the combination of SLS and Ni. The present study suggests that industrial workers or populations exposed simultaneously to SLS and Ni are more prone to dermal irritation or inflammation.

Acid Phosphatase↗
PubMed1988

A prototype device for nonimmersion shock wave lithotripsy using ultrasonography for calculus localization.

Extracorporeal shock wave lithotripsy has revolutionized the clinical treatment of renal calculi. A device was constructed with a spark gap for shock wave generation and a water-filled ellipsoidal reflector to focus the shock wave energy. A membrane coupled the device to the pig and an ultrasonic transducer was used for stone visualization. Initial in vitro experiments and in vivo studies using dwarf pigs demonstrated fragmentation of calculi.

Animals↗
PubMed1988

Oncocytic cardiomyopathy syndrome.

The case presented is the first report of oncocytic cardiomyopathy associated with congenital heart disease. The clinical presentation was typical of hypoplastic left heart syndrome, and the oncocytic cardiomyopathy was an unexpected finding at autopsy. The associated lesions of oncocytic metaplasia in thyroid and pituitary gland have been previously reported. Maternal serology and viral cultures from the infant were negative, indicating that the oncocytic lesions were not secondary to congenital viral infection. We support the theory that oncocytic cardiomyopathy is a hamartomatous lesion, and propose as a paradigm the association between cardiac rhabdomyoma and tuberous sclerosis. Careful follow-up of surgically "cured" oncocytic cardiomyopathy should uncover oncocytomas in other organs later in life.

Female↗
PubMed1988

Nutritional survey of the US Navy SEAL trainees.

The nutritional status of 267 male US Navy Sea, Air, and Land (SEAL) trainees was assessed to determine dietary patterns. Diet records, blood samples, 24-h urine collections, and physical characteristics were analyzed. Energy intake was 3886 +/- 73 kcal/d (SEM) with 15.7 +/- 0.2, 42.9 +/- 0.6, and 41.2 +/- 0.5% of the energy derived from protein, carbohydrate (CHO), and fat, respectively. Mean cholesterol intake (1008 +/- 35.7 mg/d [SEM]) exceeded the US Dietary Goal (less than or equal to 300 mg/d) and serum cholesterol concentration was 5.25 +/- 0.41 mmol/L (SEM). Over 38% of the trainees had cholesterol concentrations greater than 5.3 mmol/L, an indicator of high risk for cardiovascular disease. Mean sodium intake was 250 +/- 22 mmol/d. Over 86% of the trainees consumed greater than 144 mmol/d. Urinary Na excretion was high (146.7 +/- 6.7 mmol/d [SEM]) and correlated with Na intake (r = 0.365; p = 0.001). Potassium and selected vitamin intakes approximated the Military Recommended Dietary Allowances. Fat, cholesterol, and Na intakes were high relative to the dietary goals. Whether more dietary CHO would improve performance in endurance training remains to be determined.

Cholesterol, Dietary↗