Effect of spike disease on the 5′-and 3′-nucleotidase activities in sandal plants

Summary In the sandal plant affected by spike disease, caused by mycoplasma-like organisms, the changes occurring in the 5-and 3-nucleotidase activities were studied and their possible significance discussed.     

Detection of pyrimidine 5′-nucleotidase deficiency using1H-or31P-nuclear magnetic resonance

Summary We describe here a further Japanese family with pyrimidine 5-nucleotidase (P5N) deficiency diagnosed using a nuclear magnetic resonance (NMR) spectrum, in Kumamoto prefecture where two families having the disease have been reported before. The specific spectra in¹H-NMR of P5N deficient erythrocytes were due to three methyl protons of CDP-choline at 3.22 ppm and to H-2, H-8 and ribose-1 of pyrimidine nucleotide phosphate(s) in the lower fields (at 5.82 and 8.00 ppm). The other specificities in³¹P-NMR spectra were due to CDP-choline, CDP-ethanolamine and UDP-glucose. Those spectra were not detected in other types of hemolytic anemia.     

Evidence for essential catalytic determinants for human erythrocyte pyrimidine 5′-nucleotidase

Human erythrocyte pyrimidine 5′-nucleotidase, PN-I, catalyzes the dephosphorylation of pyrimidine nucleoside monophosphates. The enzyme also possesses phosphotransferase activity, transferring phosphate groups between pyrimidine nucleoside monophosphates and various pyrimidine nucleosides. Deficiency of the enzyme activity is associated with a hemolytic anemia. PN-I cDNA has been expressed in Escherichia coli, yielding a fully active recombinant enzyme, which was purified to homogeneity and extensively characterized. Multiple sequence alignment of PN-I and homologues proteins revealed the existence of conserved regions, whose importance in catalysis was examined by performing experiments designed to intercept covalent intermediates as strongly suggested by our previous kinetic studies. Furthermore, a functional analysis of the enzyme was carried out through site-directed mutagenesis designed on the basis of the sequence of the identified conserved regions as well as mutations observed in PN-I-deficient patients.Received 25 March 2005; received after revision 3 May 2005; accepted 13 May 2005     

Effect of dexamethasone on Fc γ receptor expression in foetal and neonatal rat gut

Summary When injected into 12-day-old suckling rats, dexamethasone caused a precocious disappearance of Fc receptors from enterocytes of the proximal small intestine. However, dexamethasone appeared to be necessary for the maintenance or production of such receptors in foetal rat gut cultured in vitro.Supported by an award from the Science and Engineering Research Council.     

Effect of 3,5,3′-tri-iodothyronine on cellular growth and oxygen consumption in neonatal rat brain

Summary The effect of thyroid deficiency and treatment with tri-iodothyronine (T₃) on oxygen consumption by neonatal (6-day-old and 15-day-old) rat brain was examined using glutamate, -hydroxybutyrate, succinate and ascorbate+TMPD as substrates. The respiration rates decreased significantly in 15-day-old hypothyroid pups. Treatment of normal and of hypothyroid pups with T₃ resulted in a significant increase in the respiration rate at both ages. Respiration rates with glucose as the substrate were not affected under these conditions.     

Synthesis of 5′-deoxypyridoxal derivatives

Summary A convenient synthesis of 5-deoxypyridoxal derivatives is described. The method involves catalytic hydrogenolysis of the corresponding 5-phosphorylated derivatives; products are obtained in high yields.Supported by PHS Grant No. 5429-16-9.     

Effect of α-methyl-DOPA on myocardial catecholamines

Résumé L'-méthyl-DOPA, même à doses élevées et/ou répétées, ne modifie pas significativement l'activité vasopressive totale — estimée sur la pression arérielle du rat décérébré et démédullé — des amines catéchiques cardiaques. La quantité de noradrénaline libérée du coeur de cobaye 1 h à 6 jours après administration d'-méthyl-DOPA y est remplacée par une quantité équipressive d'-méthyl-noradrénaline.     

Regional pattern and heat-resistance of brain 5′-deoxy-5′-methylthioadenosine phosphorylase

Summary The distribution of 5-deoxy-5-methylthioadenosine (MTA) phosphorylase in 10 pig brain areas was determined. The observed regional differences of the enzymatic activity seem to reflect more the pattern of brain spermine distribution rather than that of spermidine. Moreover, comparative studies on the heat-resistance of MTA phosphorylase extracted from the whole brain of various species suggest structural differences in the enzyme molecules occurring in the brains of different animals.     

Determination of erythrocyte pyrimidine 5′-nucleotidase activity by31P nuclear magnetic resonance: Comparison of normal controls and multiple sclerosis patients

Summary A technique to assay erythrocyte pyrimidine 5-nucleotidase activity in situ using³¹P nuclear magnetic resonance spectroscopy is presented. The assay is chemically specific, simple and applicable to untreated lysates. A comparison of enzyme levels in normal controls and in multiple sclerosis patients employing the assay yielded no significant differences between both groups. Difficulties encountered in the quantitative analysis of the assay using¹H-NMR spectroscopy are briefly discussed.     

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

Summary 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 K_m values of 2.0×10^–3 mM and 0.2 ×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.     

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

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

The effect of bile salts on thyroxine 5′-monodeiodination in rat liver homogenate

Summary Unconjugated and conjugated bile salts inhibited the conversion of thyroxine to 3,3,5 triiodothyronine in rat liver homogenate.This work was supported in part by a grant from the Imanaga Foundation, Nagoya, Japan.     

Effect of glucose and phloretin-2′-β-D-glucose (phloridzin) on in vitro fertilization of mouse ova

Summary The fertilization ratio of mouse ova in vitro decreased when glucose concentration in the medium was lowered. However, the addition of phloretin-2--D-glucose (phloridzin), known as a glucose uptake inhibitor, restored the fertilization ratio back to the control level. The glucose moiety of the phloridzin seemed to be responsible for this effect.     

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.     

Antiproliferative effects of 4′, 5′-unsaturated adenine nucleosides on leukemia L 1210 cells in vitro

Summary Several 4, 5-unsaturated adenine nucleosides were shown to have antiproliferative activity against L 1210 leukemia cells in vitro. The active nucleosides were cytotoxic to the L 1210 cells as demonstrated by Trypan Blue uptake. The cytotoxicity was not induced by alterations in the ribonucleoside and deoxyribonucleoside triphosphate levels of the L 1210 cells.     

Reaction of pyridoxal-5′-phosphate with γ-carboxyglutamic acid

Summary Pyridoxal-5-phosphate (PLP) reacts with -carboxyglutamic acid (Gla) to form a stable complex absorbing at 325 nm. It is suggested that a condensation occurs in which the formyl group of PLP reacts with the -amino group and the carbon atom of Gla to give a pyrrolidine derivative.     

Effect of radical scavengers on TNFα-mediated activation of the uPA in cultured cells

Active oxygen, produced by cultured cells following stimulation with various growth factors, seems to be involved in signal transduction leading to cellular responses such as gene expression and growth modulation. In the present study, the intracellular oxidation state was measured in immortalized human endothelial cells (ECV304) after treatment with tumor necrosis factor (TNF), using a fluorescent dye and a laser-scanning confocal microscope. The intracellular oxidation state was increased 60 min after the addition of TNF, and this increase was abolished by a radical scavenger, N-acetylcysteine (NAC), which is also a precursor of glutathione, and by pyrrolidine dithiocarbamate (PDTC). TNF increased the steady state level of urokinase-type plasminogen activator (uPA), and NAC inhibited this increase at a dose that also inhibited the increase in the intracellular oxidation state. PDTC, on the other hand, did not affect the induction of the uPA gene by TNF. These results suggest that intracellular glutathione level rather than the oxidation state is necessary for the induction of the uPA gene by TNF.     

Effect of hormones and cyclic AMP on γ-glutamyltranspeptidase activity of rat mammary gland explants

Summary -Glutamyl transpeptidase activity was assayed in midpregnant rat mammary gland explants at 14, 22 and 38 h, in the presence and absence of insulin, prolactin and corticosterone. With these 3 hormones the explants attained the characteristics of a secretory gland after 22 h of tissue culture, at which time the enzyme exhibited its maximal activity. The addition of dibutyryl cyclic AMP in the presence of the 3 hormones produced a significant increase in enzyme activity, which was maximal with a 1 mM concentration of the cyclic nucleotide. A similar effect was observed when theophylline or theophylline plus dibutyryl cyclic AMP were added to the culture medium.This work was supported by grant B1138-8333 from the Departamento de Desarrollo de la Investigación, Universidad de Chile.