Apparent co-operative effect of hydrogen carbonate (HCO-3) on pigeon kidney pyruvate carboxylase

Kinetic methods have been used to determine the interrelationship between HCO-3, pyruvate and acetyl-CoA and their effect on pigeon kidney pyruvate carboxylase (pyruvate: CO2 ligase [ADP], EC 6.4.1.1). HCO-3 shows a negative co-operative effect (biphasic kinetics with two different Km values). Pyruvate influences the attachment of HCO-3 to this enzyme. The same has been shown for acetyl-CoA. Contrary to the results of other investigators no co-operative effect was seen with pyruvate even at different concentrations of acetyl-CoA. HCO-3 itself shows hardly any effect on the homotropic positive co-operativity (sigmoidal kinetics) of acetyl-CoA. The negative co-operative effect of HCO-3 could not be removed even at saturating concentrations of pyruvate and/or acetyl-CoA, which is also supported by the n and Rs values. The results of this communication bring out differences between pigeon kidney pyruvate carboxylase and pyruvate carboxylase from other sources. It is also suggested that there may be different allosteric and regulatory sites for acetyl-CoA, HCO-3 and pyruvate.     

Limited Lead Selection for Estimation of Body Surface Potential Maps in Electrocardiography

Body surface potential mapping has shown promise as a technique to improve the resolution and accuracy of diagnostic electrocardiography, but the cost and effort required to obtain maps have made wide spread use impractical. As a step toward a practical system, the problems of redundancy and uniqueness of electrocardiographic signal information contained in large numbers of leads were investigated. An algorithm for optimal selection of a limited number of leads was developed. Data obtained from 132 human subjects including some with normal electrocardiograms (ECG) as well as some with abnormal ECGs, were used in the study. Estimation of body surface potentials from limited leads was evaluated using three criteria, including rms error, mean correlation coefficient between limited lead and total lead maps, and error to signal power ratio. Using 30 leads the average rms error was 32 ?V, average correlation coefficient was .983 and noise to signal power was 3.5% in the presence of 20 ?V rms noise. Another finding was that optimal sites are not unique, i.e., different sets of optimal sites may be found which perform equally well. This result has practical implications for the design of lead systems for estimating maps on the critically ill and on patients undergoing stress tests.     

Evaluation of iron pyrites as sulphur fertilizer

A field experiment was conducted for three consecutive winter crop seasons commencing in 1979–80 on the Typic Ustochrept of Pura to evaluate iron pyrites as S fertilizer. Four crops viz, wheat, chickpea, mustard and Egyptian clover were tested for their responsiveness to added pyrites. All the crops responded significantly to added pyrites. Mustard proved most sensitive to S deficiency in soil and wheat the least. Between the two legumes, Egyptian clover was more sensitive to S stress than chickpea. Average biomass production by Egyptian clover was highest followed by wheat, mustard and chickpea. Mustard and Egyptian clover required more S to achieve maximum biomass production compared with wheat and chickpea but they also recovered from the soil a large proportion of added S than wheat and chickpea. Addition of pyrites increased availability of S in soil. Pyrites enhanced mobilization of soil P and its utilization by the crops.     

Low-titer cold-hemagglutinin disease. Mechanism of hemolysis and response to corticosteroids

We studied two patients with a low-titer cold-hemagglutinin disease syndrome to investigate the mechanism of hemolysis and the therapeutic response to corticosteroids. The antierythrocyte antibody was of the IgM class, had a high thermal amplitude and had enough activity of 37 degrees C to account for the hemolysis. The capacity of peripheral blood monocytes to increase the osmotic fragility of C3-coated erythrocytes suggests that macrophage interaction with C3-coated erythrocytes explains the observed in vivo spherocytosis. Both patients responded to high-dose corticosteroids. The data suggest that the steroid effect is probably due to alteration of macrophage complement-receptor function. These studies demonstrate the importance of antibody activity at body temperature in producing hemolysis, particularly in this variant of cold-hemagglutinin disease. The response to steroids suggests the efficacy of corticosteroid therapy in alleviating hemolysis due to macrophage recognition of erythrocytes coated with IgM and C3.     

Responses of different types of connective tissue to hormone administration

The lysosomal glycosidase activity of the eye tissues (the sclera and cornea), the bone tissues and cartilage were studied. The intraperitoneal injection of tyrocalcitonine (TCT), deoxycorticosterone (DOCS), hydrocortisone (HC), and somatotropic hormone (STH) influenced both the activity of beta-galactosidase, beta-glucosidase, and hyaluronidase, the the functional state of thy lysosomal membranes of the connective tissues under investigation. GC and STH caused stabilization, whereas DOCS and large doses of TCT--a labilizing effect on the lysosomal membranes and tissues understudy. The absolute activity of the enzymes in the homogenates decreased after the HC and STH injection. DOCS produced an opposite effect.