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.     

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.     

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.     

A new regulatory element that augments the Tax-dependent enhancer of human T-cell leukemia virus type 1 and cloning of cDNAs encoding its binding proteins.

The Tax protein of human T-cell leukemia virus type 1 (HTLV-1) trans activates the 21-bp enhancer of HTLV-1. A sequence of more than two copies of the 21-bp enhancer is efficiently activated by Tax, but one copy is not activated extensively. Another sequence (TRE-2, positions -163 to -117) adjacent to the 21-bp enhancer in the long terminal repeat of HTLV-1 can enhance a single copy of the 21-bp enhancer activity in trans activation by Tax. This sequence contains motifs related to the Ets- and NF-kappa B-binding sequences, but mutations at these sites indicated that neither is responsive to cooperation with the 21-bp enhancer. A deletion mutation of TRE-2 identified 25 bases at positions -158 to -134 (TRE-2S) as an essential sequence, and TRE-2S was sufficient to give maximum cooperation with one copy of the 21-bp enhancer in trans activation by Tax protein. Using TRE-2S as a probe, we screened a cDNA library of HUT102 cells by the Southwestern (DNA-protein) procedure and isolated two cDNA clones, THP-1 and -2. These two clones encode TRE-2S-binding proteins, and they differ by only an extra 17 amino acids in THP-2. Both THP proteins contain five zinc finger motifs which are strikingly similar to those of the GLI family, an amplified gene product in glyoma cells. The binding site of THP-1 and -2 was GAACCACCCA in TRE-2S, which is highly homologous to the GLI-binding site. These results suggest that binding of THP to TRE-2S may be involved in cooperation with one copy of the 21-bp enhancer in responding to Tax trans activation.     

Preparation of immobilized enzyme with high activity using affinity tag based on proteins A and G

Affinity tag AG consisting of immunoglobulin G (lgG)-binding domains of protein A from Staphylococcus aureus (EDABC) and those of protein G from Streptococcus strain G148 (C2C3) were used to facilitate immobilization of beta-galactosidase (betagal) from Escherichia coli. Poly(methylmethacrylate/N-isopropylacrylamide/methacrylic acid) [P(MMA/NIPAM/MAA)] and poly(styrene/N-isopropylacrylamide/methacrylic acid) [P(St/NIPAM/MAA)] latex particles, which show thermosensitivity, were used as support materals to prepare affinity adsorbents. Human gamma-globulin (HgammaGb), whose major fraction is lgG, was used as an affinity ligand and was covalently immobilized onto the both latex particles by the carbodiimide method under various conditions. A fusion protein, AGbetagal, was immobilized at pH 7.3 by the specific binding of affinity tag to these affinity adsorbents. The amount of adsorbed AGbetagal per unit amount of immobilized HgammaGb, namely, efficiency of ligand utilization, was strongly affected by the type of latex particles and pH value for HgammaGb immobilization. The efficiency of ligand utilization was maximum in the affinity adsorbents prepared at pH 6.0 to 7.0, and that in the HgammaGb-P(MMA/NIPAM/MAA) latex particles was high. This result could be explained by the conformation and orientation of immobilized HgammaGb molecules. Immobilized AGbetagal retained approximately 75% of its activity in solution and the binding is stable enough to allow repeated use. These results clearly demonstrate that combination of the affinity tag AG and the affinity adsorbents, based on the thermosensitive latex particles, offers a simple and widely applicable method for preparation of immobilized enzyme with high activity. (c) 1995 John Wiley & Sons, Inc.     

Isolation and characterization of a succinimide variant of methionyl human growth hormone.

Deamidation of asparagine and glutamine residues, isomerization of aspartic acid side chains, and racemization of the L- to the D-form of the amino acids are common spontaneous chemical reactions known to occur in proteins. Previous studies have implicated succinimides as intermediates in these reactions; however, the evidence has been indirect. Our results demonstrate, for the first time, the presence of a succinimide intermediate in an intact protein. The succinimide (cyclic imide) variant was isolated from thermally stressed recombinant methionyl human growth hormone (hGH) by high performance anion-exchange chromatography, further purified by reversed-phase high performance liquid chromatography, and analyzed by tryptic mapping. A later eluting tryptic peptide, compared with the native T12 peptide (residues 128-134, Leu-Glu-Asp-Gly-Ser-Pro-Arg), was analyzed by mass spectrometry (MS). This variant had a protonated molecular mass of 755.3 atomic mass units (u), as compared with 773.3 u for the native T12 peptide. A difference of 18 u, a loss of water, is consistent with the formation of a succinimide intermediate at Asp-130 of methionyl hGH. MS/MS analysis of the cyclic imide-containing peptide verified that the modification occurred at Asp-130. A difference of 18 u was also observed for the intact cyclic imide methionyl hGH variant (22,238 u), as measured by electrospray mass spectrometry, compared with native methionyl hGH (22,256 u).     

Multiple cyclic nucleotide phosphodiesterase activities from rat tissues and occurrence of a calcium-plus-magnesium-ion-dependent phosphodiesterase and its protein activator.

1. Supernatant fluids from rat cerebral cortex, cerebellum, kidney, heart and liver contained more phosphodiesterase activity hydrolysing cyclic GMP than that hydrolysing cyclic AMP when assayed with sub-saturating concentrations of substrate. 2. These activities were resolved into several fractions by Sephadex G-200 gel filtration; no two tissues had similar activity profiles. 3. With every tissue examined, a fraction (fraction II) with a molecular weight of about 150,000 was obtained which hydrolysed cyclic GMP preferentially at sub-saturating substrate concentrations in the presence of micromolar concentration of Ca2+, millimolar concentration of Mg2+ and a protein activator. 4. The activity of fraction II accounted for about 60 percent in liver, more than 80 percent in heart and cerebellum, and almost 100 percent in cerebral cortex of the total activity for cyclic GMP hydrolysis, calculated from the activity profiles. 5. Km values of fraction II samples from kidney, heart and liver for cyclic GMP were 1.3, 1.7 and 5 muM respectively. 6. 3-Isobutyl-1-methylxanthine inhibited hydrolysis of cyclic GMP by fraction II with an I50 value of 3muM for heart and liver and 50 muM for cerebrum. 7. The activator protein, with an estimated molecular weight of about 30,000 was isolated from all the tissues listed in 1.8. The concentrations of activator protein and of the isolated enzyme, fraction II, did not correspond exactly.