Purine metabolic enzymes in lymphocytes. I. Adenosine deaminase and purine nucleoside phosphorylase activities in mouse lymphocyte subpopulations

The distribution of adenosine deaminase (ADA) and purine nucleoside phosphorylase (PNP) activities in lymphoid organs and lymphocyte subpopulations in mice, and the effect of phytohemagglutinin P (PHA-P) and concanavalin A (Con A) on the enzyme activities were studied. ADA activity was distributed equally in cells from all organs used and no mouse strain differences were observed. In contrast, PNP activity varied with the mouse strain, being highest in C57BL/6 mice and lowest in BALB/c mice, and with the organ in ICR mice, being high in peripheral blood lymphocytes and spleen lymphocytes, low in mesenteric lymph node cells and absent or very weak in thymus cells. T and B lymphocytes were prepared from spleen of ICR mice. High ADA activity was found in both T and B lymphocytes, whereas PNP activity in the T lymphocytes was about one-third of that in the B lymphocytes. PNP activity in thymus cells was increased to the normal level of T lymphocytes in the spleens by cultivation without stimulant. The development of PNP activity in thymus cells was partially inhibited by Con A but was not affected by PHA-P. ADA activity in thymus cells was enhanced by in vitro stimulation with PHA-P but not with Con A. In contrast, in spleen lymphocytes the development of ADA activity was enhanced by stimulation with PHA-P and Con A, and that of PNP activity was enhanced by PHA-P but not by Con A.     

Some Problems in the Assay Method of HMG-CoA Reductase Activity in Sweet Potato in the Presence of Other HMG-CoA Utilizing Enzymes

In addition to HMG-CoA reductase, another HMG-CoA utilizing enzyme is present in the Mt fraction of sweet potato root tissue and its activity interferes with the assay to HMG-CoA reductase activity.     

Fractal property of eye movements in schizophrenia

 On the basis of a temporal model of animal behavior we conducted temporal analysis of eye movements in schizophrenic subjects (n=10) and normal controls (n=10). We found a fractal property in schizophrenic subjects, the fixation time of eye movement during reading ambiguous and difficult sentences showing a clear inverse power law distribution. An exponential distribution of a nonfractal nature was found in normal controls. Received: 21 July 1995/Accepted in revised form: 30 April 1996     

Calcium influx in a single rat basophilic leukemia cell as revealed with a digital imaging fluorescence microscope

Using a digital imaging fluorescence microscope, we have detected a rapid transient increase in the free cytosolic calcium concentration in a single rat basophilic leukemia cell (RBL-2H3) after antigen stimulation. Calcium ions were transported very rapidly (within 1 s) after a lag time (about 10 s at 37 degrees C) from the external environment into the cytoplasm. On the basis of the present experimental results we conclude that the gradual changes in the overall fluorescence intensity observed for a cell suspension are due to the distribution of different lag times shown by different cells as to the calcium influx through membrane calcium channels.     

Influence of stress on the maturity of T-cells

Stress is known to influence the immune function via an effect on the central nervous system. We previously presented data showing that stress alters the population of T-cell subsets in mice. The variations of T-cell subsets in the thymus, peripheral blood, and spleen in mice similarly stressed by immobilization or by unavoidable and opioid-dependent stress were measured by flow cytometry using the monoclonal antibodies anti-L3T4, anti-Lyt 1, anti-Lyt 2 and anti-Thy 1, 2. Immobilization stress was applied for three days and T-cell subsets were measured on the days 1, 2 and 3, as well as on day 7 after release from immobilization. Lyt 2-positive cells in the thymus were the most sensitive to stress, showing significant variations. The proportion of immature T-cells increased in the thymus, blood and spleen of the stressed mice. When diazepam or naloxone were administered 30 min before the initiation of stress, these variations tended to decrease. Thus, the ratio of T-cell subsets varied with the duration of immobilization stress. This appeared to be partly mediated by the opioid system and the central nervous system.     

Alterations in cardiac function and subcellular membrane activities after hypervitaminosis D3

The present study was designed to induce massive accumulation of calcium in the myocardium and to evaluate the effect of calcium overload on myocardial contractile function and biochemical activity of cardiac subcellular membranes. Rats were treated with an oral administration of 500,000 units/kg of vitamin D₃ for 3 consecutive days, and their hearts were sampled on the 5th day for biochemical analysis. On the 4th and 5th days, heart rate, mean aortic pressure, left ventricular systolic pressure and left ventricular dP/dt were significantly lowered in vitamin D₃-treated rats, demonstrating the existence of appreciable myocardial contractile dysfunction. Marked increases in the myocardial calcium (67-fold increase) and mitochondrial calcium contents (24-fold increase) were observed by hypervitaminosis D3. Mitochondrial oxidative phosphorylation and ATPase activity were significantly reduced by this treatment. A decline in sarcolemmal Na⁺, K⁺-ATPase activity was also observed, while relatively minor or insignificant changes in calcium uptake and ATPase activities of sarcoplasmic reticulum were detectable. Electron microscopic examination revealed calcium deposits in the mitochondria after vitamin D₃ treatment. The results suggest that hypervitaminosis D₃ produces massive accumulation of calcium in the myocardium, particularly in the cardiac mitochondrial membrane, which may induce an impairment in the mitochondrial function and eventually may lead to a failure in the cardiac contractile function.     

Kinetics of the hydrolysis of monodispersed dihexanoyllecithin catalyzed by the phospholipase A2 from Agkistrodon halys blomhoffii venom

The hydrolysis of 1,2-dihexanoyl-sn-glycero-3-phosphorylcholine (diC6PC), catalyzed by the phospholipase A2 from the venom of Agkistrodon halys blomhoffii, was studied at 25 degrees C and the ionic strength of 0.1 in the presence of 3-33.3 mM Ca2+, which can saturate the Ca2+-binding site of the enzyme. The initial velocity data, obtained at various concentrations of the substrate below the critical micelle concentration (cmc), were analyzed according to the Michaelis-Menten equation. The pH-dependence curve of the Km value exhibited only one transition below pH 8. The analytical results indicated that the pK value of 6.30 of an ionizable group changed to 6.54 on the binding of the monodispersed substrate. This ionizable group was assigned as the alpha-amino group on the basis of its pK value, which had been determined from the pH dependence of the binding constant of monodispersed n-dodecylphosphorylcholine (n-C12PC) (Ikeda and Samejima (1981) J. Biochem. 90, 799-804, and Haruki et al. (1986) J. Biochem. 99, 99-109). The pH-dependence curve of the kcat value exhibited two transitions, below pH 6.5 and above pH 9.5. The analytical results indicated the participation of two ionizable groups with pK values of 5.55 and 10.50. Deprotonation of the former and protonation of the latter group were found to be essential for the catalysis. The former ionizable group was assigned as His 48 in the active site on the basis of its pK value, which had been determined from the pH dependence of the binding constant of Ca2+ (Ikeda et al. (1981) J. Biochem. 90, 1125-1130).(ABSTRACT TRUNCATED AT 250 WORDS)     

Primordial germ cells and lymphomyeloid system in the embryos of the Aleutian skate,Bathyraja aleutica

Organogenesis in embryos (1 and 5 mm-disk widths) of the Aleutian skate,Bathyraja aleutica was described histologicaily in complete serial paraffin sections. Special attention was paid to localization of primordial germ cells (PGC) and development of lymphoid tissues. The embryo of 1 mm-disk width was at the somite stage with no evidence of organogenesis. PGC, gathered in the genital ridge, were seen in the somatic mesodermal layer as well as in the mesenchyme between the endoderm and splanchnic mesoderm of the 1 mm-embryo. Most of the visceral organs were developing in the embryo of 5 mm-disk width. With respect to the development of immune system, two pairs of thymus anlagen, filled with numerous thymic lymphocytes, were recognized in the pharyngeal region. A small focus of numerous immature blood cells appeared to be an anlage of the spleen was found between the stomach and the liver.     

Reactivation of Cytoplasmic Streaming in a Tonoplast-Permeabilized Cell Model of Acetabularia

To find whether cytoplasmic streaming in Acetabularia is controlledby Ca²⁺, a tonoplast-permeabilized cell model was prepared usinga vacuolar perfusion technique. The cytoplasmic streaming remainedalmost normal after perfusion with EGTA medium (10 mM EGTA,40 mM PIPES, 5mM MgCl₂ and 800 mM sorbitol, pH 6.9), but stoppedwithin 10 min when saponin medium (EGTA medium plus 50 µg/mlsaponin, 50 µg/ml hexokinase and 5 mM glucose) was perfused.This model system was reactivated with a solution containing0.5 mM ATP and different concentrations of Ca²⁺ (reactivationmedium). With the reactivation medium at pCa 6–5, theresumed streaming lasted for about 10 min before the cytoplasmaggregated. At pCa 4–3, the streaming was observed onlyfor a few minutes because the cytoplasm aggregated quickly.At pCa 7, no reactivated movement was observed. Reactivationwas not induced in an ATP- or Mg²⁺-deficient medium even inthe presence of an adequate concentration of Ca²⁺, and was inhibitedby 50 µg/ml cytochalasin B or 1 mM N-ethylmaleimide. We concluded from these observations that the cytoplasmic streamingin Acetabularia is very likely to be driven by the actomyosinsystem in the presence of Mg-ATP and Ca²⁺ at pCa 6–5. (Received October 31, 1984; Accepted April 1, 1985)