Characterization and purification of polymorphic arylalkylamine N-acetyltransferase from the American cockroach, Periplaneta americana.

We separated two forms of arylalkylamine N-acetyltransferase (AANAT) from various organs of the American cockroach, Periplaneta americana. Both forms of the enzyme had an equivalent molecular mass of 28 kDa. One form isolated from the testicular accessory glands had high enzyme activity at acidic pHs. The isoelectric point was 5-6 and the substrate specificity was wider than the other type. The other isolated form from female midguts had a higher level of enzyme activity at basic pHs. These findings suggested that P. americana contains polymorphic AANAT, as is the case in Drosophila melanogaster. These forms differed not only in pH specificity, and substrate specificity but in chromatographic behavior and kinetic properties. Most of the organs we examined contained a mixture of the two forms since two types of AANAT activity were separated in different chromatographic fractions when two pH conditions were used for activity measurement.     

Effects of intervals between jumps or bouts on osteogenic response to loading.

Prolonged loading repetitions can diminish the mechanosensitivity of bones, and increased intervals between loading might restore sensitivity. This study was designed to investigate the effects of intervals between loadings or bouts on osteogenic response. Forty female Fisher 344 rats aged 5 wk were divided into a control group and three exercise groups: 20 jumps in a single bout with a 3-s (S3) or 30-s (S30) jump interval, or 20 jumps in 2 bouts (10 x 2) separated by a 6-h interval with a 3-s jump interval (D3). After 8 wk of training, the bone masses per body weight of the femur and tibia were significantly greater in the three exercise groups than in the control group, and these values were also greater in S30 than in S3, although they were at the same level in D3 and S3. These data suggest that a longer interval (30 s) between individual loading had more effective anabolic effects on bone than a shorter interval (3 s).     

Glycyrrhizic acid and its hydrolysate as mineralocorticoid agonist

Mineralocorticoid activity of glycyrrhetinic acid (GR) was studied in vivo (electrical potential difference in rat rectum) and in vitro (brush border Mg2+-HCO3- ATPase in rat small intestine, kidney cytosol binding of GR with and without RU-28362, anti-glucocorticoid compound) in order to clarify the mechanism of mineralocorticoid-like activity of GR. Scatchard analysis of [3H]aldosterone showed that Kd of higher affinity site (type I) 6.0 X 10(-9) M, Bmax 1.0 X 10(-14) mol/mg protein, and Kd of lower affinity site (type II) 1.6 X 10(-7) M, Bmax 7.5 X 10(-14) mol/mg protein. GR competed for [3H]aldosterone binding sites in kidney cytosol at the concentration of 10(4) times as that of unlabeled aldosterone. RU-28362 displaced aldosterone binding curve, whereas GR binding kinetic was not affected by this compound. Adrenalectomy caused a significant fall in brush border Mg2+-HCO3- ATPase activity (75% reduction compared with the initial level) which was not restored by GR administration. Electrical potential differences in the adrenalecomized rats were significantly lower than those in the control rats, which did not increase after GR administration.     

Effects of Exogenous Amino Acids on Iron Uptake in Relation to their Effects on Photoperiodic Flowering in Lemna paucicostata 6746

The flowering of Lemna paucicostata 6746 grown on 14-h photoperiodwas enhanced by the addition of high concentrations of ironto the medium, which also increased the endogenous iron concentration.The addition of asparagine, aspartate, glutamate, -alanine,glycine or serine to the medium also increased the endogenousiron level, resulting in the promotion of flowering. In contrast,the addition of cysteine, cystine, glutamine, arginine, threonineor phenylalanine lowered the endogenous iron level, resultingin the inhibition of flowering. Glycine and asparagine added to the medium during an inductive96-h dark period did not promote iron uptake and had no effecton flowering, but when added during the subsequent 120-h lightperiod, they promoted both iron uptake and flowering response.The increase in the endogenous iron level seems to favor floraldevelopment rather than induction of photoperiodic floweringof Lemna paucicostata 6746. (Received September 8, 1986; Accepted March 31, 1987)     

Evaluation of radiation dose resulting from the ingestion of [3H]- and [14C]thymidine in the rat

Average doses to rat tissues from the ingestion of 2-[14C]thymidine were compared with those from methyl-[3H]thymidine or 6-[3H]thymidine. Among the three precursors, [14C]thymidine gave the highest dose to spleen and small intestine. The doses to other tissues from [14C]thymidine were almost the same or lower as compared with those from [3H]thymidine, irrespective of the 9 times higher beta-ray energy of 14C than that of 3H. In the case of [14C]thymidine, most of the dose was given by radioactivity incorporated into the organic tissue constituents (non-volatile radioactivity). In the case of [3H]thymidine, however, the dose contributions by non-volatile radioactivity were very small and the major contributions were rather from volatile radioactivity (3HHO), formed by degradation of [3H]thymidine. No significant difference in their total doses was found between the two [3H]precursors, but the dose from non-volatile radioactivity alone was 2-3 times higher with methyl-[3H]thymidine than with 6-[3H]thymidine. Estimates of the dose to cell nuclei in various tissues after the ingestion of [3H]thymidine were also made in order to predict more precisely possible radiation hazards.     

Decreased intracellular free magnesium in erythrocytes of spontaneously hypertensive rats

Using 31p-NMR (the phosphorus nuclear magnetic resonance) spectroscopy, we measured intracellular free Mg levels in the erythrocytes of untreated (n = 7) and diltiazem-treated spontaneously hypertensive rats (SHR) (n = 8), and compared them with age-matched Wistar-Kyoto rats (WKY) (n = 10). The intracellular free Mg levels were significantly (p less than 0.01) decreased in untreated SHR compared with those in control WKY. A successful antihypertensive treatment with diltiazem increased the intracellular free Mg levels compared with untreated SHR (p less than 0.05). Furthermore, an inverse correlation was observed between intracellular free Mg levels and blood pressure levels in all groups (r = -0.48, p less than 0.01, n = 25). These observations suggest that abnormalities of intracellular Mg metabolism may be, in part, related to the development or the maintenance of hypertension in SHR.     

Inhibition of tyrosine autophosphorylation of the solubilized insulin receptor by an insulin-stimulating peptide derived from bovine serum albumin

A polypeptide from a tryptic digest of bovine serum albumin potentiates glucose oxidation stimulated by insulin in isolated rat adipocytes. We studied whether this effect is related to a modification of the insulin receptor kinase. In a solubilized rat adipocytes receptor system, the peptide caused dose-dependent inhibition of the stimulation by insulin of phosphorylation of the 95,000 dalton subunit of insulin receptor. The peptide also inhibited stimulation by vanadate of tyrosine autophosphorylation of the beta subunit of the receptor, though it enhanced vanadate-stimulated glucose oxidation. During the phosphorylation reaction, no phosphorylated forms of the peptide could be detected. The peptide had no effect on dephosphorylation of the phosphorylated beta subunit of the insulin receptor. These results strongly suggest that the inhibition of phosphorylation by the peptide is due not to either simple substrate competition or activation of phosphoprotein phosphatase, but to specific inhibition of tyrosine-specific protein kinase.     

Cloning of a Vero toxin (VT2) gene from a VT2-converting phage isolated from Escherichia coli 0157: H7

Abstract A Vero toxin (VT2 or Shiga-like toxin II)-converting phage was isolated from Escherichia coli 0157: H7 strain J-2. Nontoxigenic E. coli C600 produced VT2 when lysogenized with the toxin-converting phage. Eco RI fragments of the phage DNA were ligated with Eco RI-digested pBR322 or pUC118 and were transformed into E. coli MC1061 or MV1184. Transformants exhibiting VT2 production commonly contained a 4.6 kb Eco RI fragment. It was found that a 2.3 kb Kpn I- Sph I fragment coded VT2 production and that this fragment hybridized weakly with the 2.1 kb fragment encoding VT1.     

A new gene controlling the frequency of cell division per round of DNA replication in Escherichia coli

Summary A novel mutant of Escherichia coli, named cfcA1, was isolated from a temperature-sensitive dnaB42 strain, and found to have the following characteristics. Division arrest and lethality induced by inhibition of DNA replication was reduced and delayed in the cfcA1 dnaB42 strain, as compared with the parental dnaB42 strain. Two types of inhibition of division induced by the addition of nalidixic acid or hydroxyurea were suppressed by the cfcA1 mutation. Under permissive conditions for DNA replication, the colony forming ability of cfcA1 cells was significantly reduced as compared with that of cfc ⁺ cells; conversely the division rate of cfcA1 cells was higher than that of cfc ⁺ cells. The cfcA1 mutation partially restored division arrest induced in the thermosensitive ftsZ84 mutant at the restrictive temperature and suppresed the UV sensitivity of the lon mutation. The mutation was mapped at 79.2 min on the E. coli chromosome. Taking these properties into account, it is hypothesized that the cfcA gene is involved in determining the frequency of cell division per round of DNA replication by interacting with the FtsZ protein which is essential for cell division.