Tested pH Range Research Articles

Skeletal muscle oxygen availability during respiratory acid-base disturbances in cats

Respiratory acid-base disorders elicit physiological responses that alter O 2 delivery to various tissues. We have used a near infrared (NIR) optical technique to monitor cytochrome a, a 3 oxidation state, tissue O 2 store (relative hemoglobin plus myoglobin oxygenation), and regional blood volume in intact resting skeletal muscle during respiratory acid-base disturbances in anesthetized cats. Hypercapnic acidosis of hypercapnic alkalosis were produced in separate groups of animals by ventilation with increasing concentrations of CO 2 (n = 13) or hyperventilation (n = 8). Respiratory acidosis decreased oxygen availability to hindlimb muscle while respiratory alkalosis did not change tissue oxygenation. Inspired CO 2 progressively decreased muscle blood volume, cytochrome a, a 3 oxidation level, and muscle oxygen store. These optical responses were greatly attenuated both by pre-treatment with bretylium and by hemorrhagic hypotension, suggesting mediation through sympathetic vasoconstriction. Metabolic acidosis, produced by intravenous HCl infusion (n = 8), did not reproduce the hindlimb optical responses mediated by Co 2. These experiments demonstrate that hypercapnic acidosis significantly decreases oxygen supply to resting skeletal muscle in the anethetized cat, probably via neuroregulatory responses to CO 2 which do not depend on changes in arterial [H +] in tested pH range.

Skeletal muscle oxygen availability during respiratory acid-base disturbances in cats

Respiratory acid-base disorders elicit physiological responses that alter O 2 delivery to various tissues. We have used a near infrared (NIR) optical technique to monitor cytochrome a,a 3 oxidation state, tissue O 2 store (relative hemoglobin plus myoglobin oxygenation), and regional blood volume in intact resting skeletal muscle during respiratory acid-base disturbances in anesthetized cats. Hypercapnic acidosis and hypocapnic alkalosis were produced in separate groups of animals by ventilation with increasing concentrations of CO 2 (n = 13) or hyperventilation (n = 8). Respiratory acidosis decreased oxygen availability to hindlimb muscle while respiratory alkalosis did not change tissue oxygenation. Inspired CO 2 progressively decreased muscle blood volume, cytochrome a,a 3 oxidation level, and muscle oxygen store. These optical responses were greatly attenuated both by pre-treatment with bretylium and by hemorrhagic hypotension, suggesting mediation through sympathetic vasoconstriction. Metabolic acidosis, produced by intravenous HCl infusion (n = 8), did not reproduce the hindlimb optical responses mediated by CO 2. These experiments demonstrate that hypercapnic acidosis significantly decreases oxygen supply to resting skeletal muscle in the anesthetized cat, probably via neuroregulatory responses to CO 2 which do not depend on changes in arterial [H +] in the tested pH range.

Chemical behaviour of cytidine 5'-monophospho-N-acetyl-beta-D-neuraminic acid under neutral and alkaline conditions.

The chemical behaviour of CMP-N-acetylneuraminic acid under neutral and different alkaline conditions has been investigated. The products formed were isolated by ion-exchange chromatography and gel filtration and analysed by colorimetric methods, thin-layer chromatography, combined gas-liquid chromatography/mass spectrometry and/or 360-MHz 1H-NMR spectroscopy. A maximum stability of CMP-N-acetylneuraminic acid was observed at pH8-11. In the tested pH range of 6-13, CMP and N-acetylneuraminic acid were formed in variable amounts as decomposition products. 2-Deoxy-2,3-dehydro-N-acetylneuraminic acid was produced at pH greater than 7; the amount of this substance increased with increasing pH. In anhydrous triethylamine its yield was 50%. A new neuraminic acid derivative, N-acetyl-beta-D-neuraminic acid 2-phosphate, could be isolated from the mixture of alkaline decomposition products of CMP-N-acetylneuraminic acid. The yield of this compound was maximum 22% in anhydrous triethylamine. Because 2-deoxy-2,3-dehydro-N-acetylneuraminic acid was formed under simulated physiological conditions, it is assumed that this compound, which occurs in tissues and fluids of man and animals, is derived from CMP-N-acetylneuraminic acid non-enzymically also under conditions in vivo.

Immunodiffusion studies of pneumococcal antigens with special reference to serotype 27.

The antigenic pattern of a pneumococcal strain of serotype 27 used as model was studied by immunodiffusion methods and found to show a complex antigenic structure with a least 21 separate precipitinogens. Strains belonging to type 11, 28 and 29 contained most of the precipitinogens present in the model strain while the antigenic composition of type 3 strain differed more from this strain. Double diffusion studies of capsular polysaccharides prepared by conventional methods revealed the presence of contaminating C‐polysaccharide. Within the tested pH range 4–9 the capsular polysaccharides migrated toward the anode. The electrophoretic migration of the C‐polysaccharide varied with pH. At pH 4–5 it moved slowly toward the cathode which made it possible, by preparative electrophoresis, to obtain capsular polysaccharide free from the contaminating C‐polysaccharide. This procedure is suggested as a final step in isolation of capsular polysaccharides for serological work.