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Biomedical subjects

S Long

Publications and source records attributed to S Long.

At least 109 records · Page 6Linked to original sources
PubMed1983

Renal acid excretion in the domestic fowl.

1. In order to assess the role of uricotelism in net renal acid excretion, blood and ureteral urine samples were collected from five hens fed a commercial poultry feed (Diet A) and five hens fed a protein-rich, Na-poor feed (Diet B). All samples were analysed for pH, PCO2, ammonium, phosphate, uric acid and urates (UA + U) and inulin. 2. On Diet A, average pH in venous blood was 7.42, while urinary pH (pHu) ranged from 4.74 to 7.25. At average pHu (6.10), uric acid accounted for 52% of total acid excreted, H2PO4 for 20% and NH4 for 28%. Net acid excretion in ureteral urine was 345 muequiv h-1 kg body weight-1, or 5-10 times that observed in ureotelic vertebrates (amphibians and mammals). 3. The relative contributions of these urinary buffers to net renal acid excretion changed with pHu. Significant negative correlations exist between pHu and both total phosphate and ammonium excretion rates (P less than 0.001). Excretion rates of (UA + U) showed a positive correlation (P less than 0.05) with pHu. 4. Feeding on Diet B revealed the homeostatic power of the avian kidney. Blood pH and PCO2 were not changed relative to values in hens fed the control diet while striking increases in excretion rates of all urinary buffers (except HCO3) were observed. Average pHu fell to 5.12, and the average net renal acid excretion rate doubled.

Acid-Base Equilibrium↗
PubMed1982

Acid-base balance and urinary acidification in birds.

This essay will treat, first, the defended parameters of acid-base status in avian blood and their modification under conditions pertinent to the life of birds, and, second, urinary acidification and its role in maintenance of acid-base balance. Of the two topics, urinary acidification is of particular interest to the author, has received less sustained attention experimentally and has been infrequently reviewed (Sykes, 1971), so it will receive attention here. The reports cited in the essay concern primarily adult birds outside periods of egg-laying.

Acid-Base Equilibrium↗
PubMed1982

A study of ultrastructure of egg shell of Schistosoma japonicum. I. Transmission electron microscopic observation of S. japonicum egg.

Ultrathin sections of egg shell of S. Japonicum were observed. The micropores and network of microcanals were first reported in egg shell of S. japonicum. Both the micropores and microcanals are lined by a membrane being continous with the inner layer of egg shell and filled with materials coming from inside of the egg. As in the egg of S. mansoni, the possibility of micropores and microcanals that may play an important role as natural channels in secreting materials such as soluble antigens and histolytic enzymes... etc., is discussed.

Animals↗
PubMed1982

Solvent Production and Morphological Changes in Clostridium acetobutylicum.

The morphological and cytological changes which occurred in Clostridium acetobutylicum P262 during the production of acetone, butanol, and ethanol in an industrial fermentation medium were identified and correlated with the growth and physiological changes. The swollen, cigar-shaped clostridial forms were involved in the conversion of acids to neutral solvents, and there was a correlation between the number of clostridial forms and the production of solvents. Sporulation mutants which were unable to form clostridial stages (cls mutants) did not produce solvents. Oligosporogenous mutants which showed reduced clostridial stage formation produced intermediate levels of solvents. Sporulation mutants blocked after the clostridial stage, which were unable to form mature spores (spo mutants), produced normal levels of solvents.

Journal Article↗
PubMed1982

Renal electrolyte handling, acid-base status, and urinary acidification in Bufo marinus.

In hydrated toads reabsorption of 92% of filtered bicarbonate produces a urine of pH at 22 degrees C. Average blood-to-urine pH gradient is 0.8-0.9 U under these conditions but may reach 3-4 U. Net acid excretion rate in hydrated animals is approximately 30 mu eq . h-1 . kg-1. Flow-independent acid excretion is a negative nonlinear function of urinary pH and passes from positive to negative values in the range of normal urinary pH due to rapid rise in [HCO3-] and slower decline in [NH4+]. [H2PO4-] accounts for only 10-20% of buffer-bound acid excreted. Sulfate loading in Cl-restricted toads is without effect on blood pH but produces significant reduction in blood [Cl-]/[Na+] and in urinary pH, and increased urinary [K+] and net acid secretion rates relative to controls. These renal responses are diminished or absent during sulfate loading in Cl-rich toads. In both groups [Cl-] shows significant positive correlation with pH in sulfate-containing urines. These results are discussed in the context of the nonhomeostatic model of urinary acidification developed in mammals.

Acid-Base Equilibrium↗
PubMed1982

Bicarbonate reabsorption and potassium handling in isolated perfused kidneys of Bufo marinus.

Average rates of bicarbonate reabsorption, normalized for glomerular filtration rates, rose linearly with perfusate [HCO3-] of 6-21 mM with a constant bicarbonate/creatinine clearance ratio of 0.06, similar to the in vivo value. Maximal rates of bicarbonate reabsorption occurred at 20-25 mM HCO3- perfusate. At 3 mM perfusate [K+], normalized rates of potassium reabsorption were constant from filtered perfusates mimicking metabolic acidosis, and from control perfusates; during perfusion with alkalotic Ringer solutions net potassium secretion was observed. Elevation of perfusate [K+] to 10 mM in alkalotic Ringer significantly decreased maximal rates of bicarbonate reabsorption. Overall, the pattern of bicarbonate reabsorption in toad kidneys perfused at 6-21 mM HCO3- was similar to that observed in acid-base disturbances of metabolic origin in mammals, while the pattern of potassium excretion showed significant differences in these two vertebrate classes.

Animals↗
PubMed1981

Regulation of exoprotease production by temperature and oxygen in Vibrio alginolyticus.

The production of an extracellular collagenase and alkaline protease by Vibrio alginolyticus during stationary phase was inhibited by a temperature shift from 30 to 37 degrees C and by a lack of oxygen. The stability of the exoproteases was unaffected by incubation at 37 degrees C and aeration. The optimum growth temperature for the V. alginolyticus strain was 33.5 degrees C and there was no difference in the growth rate at 30 and 37 degrees C. Aeration enhanced the rate of growth of exponential phase cells. Temperature and oxygen did not affect the growth of stationary phase cells when the exoproteases were being produced. Macromolecular synthesis in stationary phase cells was not affected by temperature. There was no rapid release of the exoproteases after temperature shift down and chloramphenicol inhibited the production of the enzymes when added at time of temperature shift down from 37 to 30 degrees C. The regulation of exoprotease production by temperature and oxygen was specific and has implications regarding the ecology of V. alginolyticus. Cerulenin, quinacrine and O-phenanthroline inhibited the production of the exoproteases.

Cerulenin↗
PubMed1981

Regulation of extracellular alkaline protease activity by histidine in a collagenolytic Vibrio alginolyticus strain.

Vibrio alginolyticus synthesized an inducible extracellular collagenase in a peptone medium during the stationary growth phase. These cultures also possessed extracellular alkaline serine protease activity. The alkaline protease activity did not require a specific inducer and it was produced in tryptone or minimal media. The collagenase was not produced in either the tryptone or minimal media. The alkaline protease activity was sensitive to catabolite repression by a number of carbon sources, including glucose, and by amino acids and ammonium ions. Cyclic AMP, dibutyryl cyclic AMP and cyclic GMP did not relieve catabolite repression. Histidine and urocanic acid stimulated the production of alkaline protease activity in tryptone and minimal media. Other compounds associated with the histidine utilization (hut) pathway did not increase alkaline protease activity. Histidine reversed the repression of alkaline protease activity by glucose of (NH4)2SO4 in minimal medium. Histidine and the compounds associated with the hut pathway inhibited collagenase production.

Amino Acids↗
PubMed1980

Mitral valve vegetations in bacterial endocarditis resembling left atrial myxoma.

A patient with Staphylococcus aureus endocarditis is reported whose echocardiogram closely resembled that found in left atrial myxoma. Because of severe mitral incompetence, the valve was replaced using cardiopulmonary bypass and at operation a large 3 cm friable vegetation was found attached to the posterior leaflet of the mitral valve. Histological examination showed changes typical of bacterial endocarditis with no evidence of myxoma.

Aged↗
PubMed1978

Autonomic receptor functions of the human ureter: an in vitro study.

The autonomic receptor functions of ureteral smooth muscle were studied in vitro on strips of human ureter obtained at surgery. A dose-dependent, reproducible, contraction response to 5-hydroxytryptamine (Serotonin, 5-HT) was demonstrated. This response could be blocked by methysergide. Responses to acetylcholine and to drugs stimulating adrenergic receptor functions were also found, but they were weak and inconsistent. This suggests that contraction of ureteral smooth muscle is mediated through receptors which are sensitive to 5-hydroxytryptamine.

Acetylcholine↗
PubMed1977

The involvement of the plasma membrane in the development of Dictyostelium discoideum. I. Purification of the plasma membrane.

A method for the isolation and purification of plasma membranes of Dictyostelium discoideum by equilibrium centrifugation on sucrose followed by Renografin continuous density gradients has been developed and monitored both with electron microscopy and a number of enzyme assays. On electron microscopy, the final plasma membrane fractions are judged to be freethe basis of of nuclei, rough endoplasmic reticulum, lysosomes and peroxisomes. Some profiles of the mitochondrial inner membranes are found within the plasma membrane fractions, but this contamination has been estimated to be only 5%. On the basis on enzyme assays, the plasma membrane fractions contain all the 5'-nucleotidase activity in the final gradients and are free of catalase, acid phosphatase and malate dehydrogenase activity (markers for peroxisomes, lysosomes, soluble enzymes and the matrix of mitochondria). Their content of glucose-6-phosphatase is reduced by more than 70%. The large majority of RNA and DNA have been removed from the preparation.

Animals↗