AMP deaminase, 5′-nucleotidase and adenosine deaminase in rat myocardial tissue in myocardial infarction and hypothermia

Summary AMP deaminase, 5-nucleotidase and adenosine deaminase have been estimated in skeletal muscle and myocardial tissue in normal rats and in rats subjected to experimental myocardial infarction or hypothermia. A difference in the enzyme distribution was found between the right and left ventricles in the normal rat. A decrease in the activity of 5-nucleotidase and an increase in the activity of adenosine deaminase were observed in infarcted myocardial tissue. The activity of all 3 enzymes was found to be depressed in the myocardium in rats subjected to hypothermia. These results are discussed in relation to adenosine production and its beneficial effects.     

Changes in activity levels of AMP deaminase and adenosine deaminase in the Indian apple snail,Pila globosa (Swainson) during starvation and aestivation stress

Summary Activity levels of AMP deaminase and adenosine deaminase have been studied in hepatopancreas, foot and mantle tissues ofPila globosa with reference to starvation and aestivation. The activity levels of both enzymes were decreased in all the tissues of aestivating snails while in starved animals AMP deaminase activity was increased, in contrast to the decreased adenosine deaminase activity.Acknowledgments. K. Srinivasa Moorthy and B. Kasi Reddy are thankful to the Department of Science and Technology, New Delhi for the financial assistance. Reprint requests should be addressed to C.S.C.     

Human adenosine deaminase and chromosome 20

Summary In patients exhibiting in marrow cells deletion of the long arm of chromosome 20, the specific activities of adenosine deaminase in cells of the peripheral blood are normal. This suggests that the gene for adenosine deaminase is not localized to the distal segment of the long arm of this chromosome.This work was supported by Grants from the National Health and Medical Research Council of Australia and the Anti-Cancer Council of Victoria.     

Changes in adenylate cyclase and 5-nucleotidase activities in liver membranes from alloxan diabetic rats

Liver membrane adenylate cyclase activity was significantly higher and 5'-nucleotidase activity significantly lower in alloxan diabetic rats compared with normal rats.     

Adenosine uptake in pyrimidine 5'-nucleotidase deficient human erythrocytes via a high affinity transport system

Using a pulse-labeling technique, 14C-adenosine uptake into pyrimidine 5'-nucleotidase (P5N) deficient erythrocytes (RBC) was found to be impaired. The Lineweaver-Burk plot showed Km values of 2.0 X 10(-3) mM and 0.2 X 10(-3) mM for normal RBC and P5N deficient RBC, respectively. These results indicate that P5N is one of regulators of the adenosine transport system and/or is associated with adenosine carrier protein.     

Occurrence of sepiapterin deaminase in the normal type silkworm,Bombyx mori

Summary Sepiapterin deaminase was prepared from the normal strain of the silkworm, Bombyx mori. After inhibition experiments, this enzyme was found to have the same properties as that isolated from the lemon mutant strain. Several new inhibitors and their K₁ values are described for the deaminase.The authors wish to thank Dr Wm. Gyure, Cape Cod Hospital, Hyannis, Massachusetts, USA, for his help in preparing this report.     

Histochemical demonstration of differences in AMP deaminase activity in rat skeletal muscle-fibres

Summary The histochemical method for AMP deaminase confirms that rat slow-twitch fibres contain less AMP deaminase activity than fast-twitch fibres. However, the enzyme appears similarly localized in all fibre types.This study was supported by NIH grant AM 21617.     

Histochemical demonstration of differences in AMP deaminase activity in rat skeletal muscle-fibres

The histochemical method for AMP deaminase confirms that rat slow-twitch fibres contain less AMP deaminase activity than fast-twitch fibres. However, the enzyme appears similarly localized in all fibre types.     

5'-Nucleotidase activity in liver homogenates of rats treated with CCl4, colchicine, cycloheximide, emetine, ethanol, ethionine and 5-fluorotryptophan

5'-Nucleotidase activity an enzyme marker of the plasma membranes, increases in female rat liver homogenates following ethionine administration, while homogenates from males show no changes. Treatment with CCl4, colchicine, cycloheximide, emetine, ethanol and 5-fluorotryptophan does not significantly modify the 5'-nucleotidase activity of liver homogenates of either female or male rats.     

Ischemic myocardial injury in cultured heart cells: In situ lysosomal damage

Summary Primary cultures of rat myocardial cells which were subjected to oxygen and glucose deprivation, 2 conditions associated with ischemia, were evaluated for alterations in lysosomal integrity. A photometric technique measured changes in latent acid phosphatase activity and lysosomal membrane permeability.Acknowledgments: The authors thank Dora Fernandez for skillful technical assistance. Research was supported by a grant from the National Heart, Lung, and Blood Institute, HL 18647.     

Effects of L-aspartic acid,L-asparagine and/or L-asparaginase on forced swimming-induced immobility,analgesia, and decrease in rectal temperature in rats

Summary The effect of L-aspartic acid, L-asparagine and/or L-asparaginase were compared with those of imipramine on immobility, number of defecations, increase of nociceptive threshold, and hypothermia, induced by forced swimming in rats. L-Aspartic acid was found to be as effective as imipramine in reducing the effects of forced swimming, presumable by normalizing the decreased level of endogenous L-aspartic acid, due to the inhibition of L-asparaginase activity and/or by stimulated the inhibited enzyme. The other treatments antagonized the immobility, but not the increased number of defecations. All compounds abolished the elevation of nociceptive threshold and hypothermia.     

Adenosine deaminase activity in peripheral blood cells from SJL/J mice

Summary Adenosine deaminase (ADA) activities were measured in peripheral blood cells of SJL/J mice, and compared with those of C57BL/6J animals. No association was observed between the levels of lymphocyte or erythrocyte ADA and immunologic abnormalities in SJL/J mice nor was evidence obtained to suggest a relationship between ADA activity and tumorigenesis in this strain.This work was supported in part by a University College Faculty Research Grant.     

Effect of pyrophosphate and orotidine monophosphate on cytosine deaminase regulatory properties

The maximal velocity of the reaction (Vmax) and the half-saturation constant (K0.5) values of the S. typhimurium cytosine deaminase were altered in the presence of its effectors, pyrophosphate and orotidine monophosphate. From the kinetics of orotidine monophosphate inhibition of cytosine deaminase, it was characterized as a mixed-type noncompetitive inhibitor.     

Kinetic study of membrane 5'-nucleotidase activity in cultured diploid cells]

5'-nucleotidase activity of cultured diplo?d cells was measured using intact suspended cells. This depended on the substrate amount, but did not vary with Mg ++ concentration-Kinetic data were determined using Con. A,a specific inhibitor.     

Human adenosine deaminases ADA1 and ADA2 bind to different subsets of immune cells

At sites of inflammation and tumor growth, the local concentration of extracellular adenosine rapidly increases and plays a role in controlling the immune responses of nearby cells. Adenosine deaminases ADA1 and ADA2 (ADAs) decrease the level of adenosine by converting it to inosine, which serves as a negative feedback mechanism. Mutations in the genes encoding ADAs lead to impaired immune function, which suggests a crucial role for ADAs in immune system regulation. It is not clear why humans and other mammals possess two enzymes with adenosine deaminase activity. Here, we found that ADA2 binds to neutrophils, monocytes, NK cells and B cells that do not express CD26, a receptor for ADA1. Moreover, the analysis of CD4+ T-cell subset revealed that ADA2 specifically binds to regulatory T cells expressing CD39 and lacking the receptor for ADA1. Also, it was found that ADA1 binds to CD16? monocytes, while CD16+ monocytes preferably bind ADA2. A study of the blood samples from ADA2-deficient patients showed a dramatic reduction in the number of lymphocyte subsets and an increased concentration of TNF-α in plasma. Our results suggest the existence of a new mechanism, where the activation and survival of immune cells is regulated through the activities of ADA2 or ADA1 anchored to the cell surface.     

Effect of pyrophosphate and orotidine monophosphate on cytosine deaminase regulatory properties

Summary The maximal velocity of the reaction (V_max) and the half-saturation constant (K_0.5) values of theS. typhimurium cytosine deaminase were altered in the presence of its effectors, pyrophosphate and orotidine monophosphate. From the kinetics of orotidine monophosphate inhibition of cytosine deaminase, it was characterized as a mixed-type noncompetitive inhibitor.     

Hepatic blood flow in acute myocardial ischemia

Hepatic blood flow was monitored in cats during myocardial ischemia (MI). Increased plasma CPK activity, the S-T segment of the electrocardiogram, and hepatic flow was reduced by 5 h to 40% of control. The results suggest that MI can influence organs distant from the original ischemic episode.     

Level of marker enzymes in spermatogenesis on administration of PGF2 alpha in rats.

Intraperitoneal administration of PGF 2 alpha in rats significantly increased testicular acid phosphatase (p less than 0.05), decreased hyaluronidase (p less than 0.05), whereas the activities of 5'-nucleotidase, N-acetyl-B-glucosaminidase, B-galactosidase and uridine diphosphatase remained unaffected.     

Free thyroxine in myocardial infarction

High values for the free thyroxine fraction were found in the serum of 24 patients during the early phase of myocardial infarction. A strong correlation between the free thyroxine fraction and free fatty acids suggests that they compete for protein binding sites. The increase in free thyroxine may have undesirable effects on myocardial oxygen demand during acute myocardial infarction.     

Plasma adenosine concentrations are elevated in Dahl salt-sensitive rats

We measured plasma levels of adenosine in Dahl salt-sensitive rats (DS) and Dahl salt-resistant rats (DR) to examine the potential role of adenosine in cardiovascular regulation in this type of hypertension. Plasma adenosine concentrations were significantly higher in DS than in DR. The NaCl content in the diet did not affect plasma adenosine concentration in either DS or DR. Significant positive correlation was found between adenosine concentrations and systolic blood pressure when the data for DS and DR were analyzed together. These results suggest that adenosine may play an important role in the pathophysiology of hypertension in DS.