Studies on phosphatidylinositol phosphodiesterase (phospholipase C type) of Bacillus cereus. II. In vivo and immunochemical studies of phosphatase-releasing activity.

Protein synthesis in the cultured rat pineal gland was monitored during the course of N-acetyltransferase induction by (l-isoproterenol or dibutyryl cyclic AMP. The incorporation of labeled amino acids into gland protein was essentially linear over a 6-h experimental period. Examination of the newly synthesized proteins by polyacrylamide gel electrophoresis and autoradiography did not reveal the appearance nor the disappearance of any specific protein(s) caused by (l-isoproterenol or (l)-propranolol. The lack of stimulation of synthesis of any specific protein was further demonstrated by constant ratio of incorporation in double-label experiments. Either 2μm (l)-isoproterenol or 1 mm dibutyryl cyclic AMP stimulated protein synthesis 20–40%. This increase was not due to an enhanced uptake of precursor radiolabeled amino acids by the glands when incubated with the β-agonist or cyclic AMP derivative. The stimulation of protein synthesis caused by (l)-isoproterenol was abolished by the β-antagonist (l)-propranolol. These results suggest that β-agonists may increase pineal gland protein synthesis through their relevant receptor and the generation of cyclic AMP. This increase in synthesis appears to be general and no selective elevation increase in any one band was observed.     

Design,synthesis, and structure–activity relationships of dihydrofuran-2-one and dihydropyrrol-2-one derivatives as novel benzoxazin-3-one-based mineralocorticoid receptor antagonists

Dihydrofuran-2-one and dihydropyrrol-2-one derivatives were identified as novel, potent and selective mineralocorticoid receptor (MR) antagonists by the structure-based drug design approach utilizing the crystal structure of MR/compound complex. Introduction of lipophilic substituents directed toward the unfilled spaces of the MR and identification of a new scaffold, dihydropyrrol-2-one ring, led to potent in vitro activity. Among the synthesized compounds, dihydropyrrol-2-one 11i showed an excellent in vitro activity (MR binding IC₅₀ = 43 nM) and high selectivity over closely related steroid receptors such as the androgen receptor (AR), progesterone receptor (PR) and glucocorticoid receptor (GR) (>200-fold for AR and PR, 100-fold for GR).     

Ventilatory and heart rate responses to hypoxia in well-trained judo athletes

Twenty-four active judo athletes were examined by an isocapnic progressive hypoxia test. The results of ventilatory and heart rate responses to hypoxia were analyzed by the hyperbolic equations, VE = VO + AVE/(PETO2 - CVE) and HR = HRO + AHR/(PETO2 - CHR), respectively, where VE and HR are observed ventilation and heart rate, VO and HRO the horizontal asymptote in ventilation and heart rate for infinite end-tidal PO2 (PETO2), AVE and AHR the slope constant indicating the magnitude of hypoxic sensitivity, and CVE and CHR the vertical asymptote in PETO2 for infinite ventilation and heart rate. AVE was further re-calculated after VE was normalized for a 70 kg body mass, using an allometric coefficient, and was defined as AVEN. 1) AVE and AVEN significantly increased with increasing body weight (BW) as has been reported previously, but no such correlation was found between AHR and BW. 2) VO2 at rest was found to be positively correlated with AVE and AVEN but not with AHR. 3) The relationship between AVE and AHR was not significant. Thus, the characteristic feature seen in hypoxic ventilatory activity was not accompanied by a similar trend in heart rate response.     

Differences in ventilatory responses to hypoxia and hypercapnia between normal and judo athletes with moderate obesity

Hypercapnic and hypoxic ventilatory sensitivities were compared in twenty-one judoists and 24 control subjects with similar degrees of moderate obesity. Data from ten non-obese control subjects were also included as a reference. Mean body weight (BW) and % of ideal body weight in the judoists and the obese and non-obese controls were 100 +/- 14.8, 94.4 +/- 5.3 and 63.4 +/- 6.1 (mean +/- SD) kg, and 142.3 +/- 16.7, 142.2 +/- 12.9 and 98.4 +/- 10.7%, respectively. Mean body fat in the judoists was 16.2 +/- 13.9%, being 25.3 +/- 7.7% in the obese control group, the difference being significant (p less than 0.01). Hypercapnic sensitivities in terms of the CO2 ventilatory response slope (S) and its normalized value for 70 kg BW (SN) of the obese controls were higher than the judoists. These findings were also verified by the CO2-occlusion pressure responses. S and SN in the obese controls were significantly correlated with BW and % body fat. However, no positive correlation was found between BW and S or SN in the judoists as well as between lean body mass and S or SN in the obese control. Hypoxic sensitivity in terms of the PETO2-ventilation hyperbola slope (A) and its normalized value (AN) in the obese control was significantly higher than the non-obese control, but the difference from the judoists was not significant. A and AN were found to increase with increasing % body fat in both judoists and obese controls.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exercise and ventilatory chemosensitivities

Although physical training does not affect CO2 chemosensitivity at rest, different kinds of physical training affect hypoxic ventilatory chemosensitivity at rest in different ways. On the other hand, a number of studies indicated that the mechanism of exercise hyperpnea is related to hypoxic chemosensitivity.     

Studies on phosphatidylinositol phosphodiesterase (phospholipase C type) of Bacillus cereus. I. purification, properties and phosphatase-releasing activity.

A phosphatidylinositol phosphodiesterase from the culture broth of Bacillus cereus, was purified to a homogeneous state as indicated by polyacrylamide gel electrophoresis, by ammonium sulfate precipitation and chromatography with DEAE-cellulose and CM-Sephadex. The enzyme (molecular weight: 29000 +/- 1000) was maximally active at pH 7.2-7.5, AND NOT INFLUENCED BY EDTA, ophenanthroline, monoiodoacetate, p-chloromercuribenzoate or reduced glutathione. The enzyme specifically hydrolyzed phosphatidylinositol, but did not act on phosphatidylcholine, phosphatidylethanolamine and sphingomyelin, under the conditions examined. The products from phosphatidylinositol of enzyme reaction were diacylglycerols and a mixture of myoinositol 1- and 1, 2-cyclic phosphates, suggesting that the enzyme was a phosphatidylinositol-specific phospholipase C. The enzyme released alkaline phosphatase quantitatively from rat kidney slices. A kinetic analysis was made on the release of alkaline phosphatase. The results suggest that phosphatidylinositol-specific phospholipase C can specifically act on plasma membrane of rat kidney slices.     

Ventilatory and heart rate chemosensitivity in track-and-field athletes

Fifty-four male track-and-field athletes and 18 male non-athletes were examined by isocapnic progressive hypoxia and CO2 rebreathing tests. Ventilatory and heart rate (HR) responses to hypoxia were analysed by a hyperbolic relationship and the ventilatory response to hypercapnia by a linear regression. The results showed that ventilatory sensitivity during hypoxia was significantly attenuated in the long-distance runners and sprinters compared to the non-athletes. Although heart rate sensitivity during hypoxia in none of the athletes showed a significant difference compared to that of the non-athletes, baseline HR in the long-distance runners was significantly lower than that of the non-athletes. None of the athletes showed significant differences in ventilatory sensitivity during hypercapnia compared to the non-athletes.     

Studies on sphingomyelinase of Bacillus cereus. I. Purification and properties.

A sphingomyelinase was purified 980-fold with recovery of 25.6% from the culture broth of Bacillus cereus, by (NH4)2SO4 precipitation and chromatography on CM-Sephadex, DEAE-cellulose and Sephadex G-75. The purified preparation was free of lipase, protease and other phospholipases. The enzyme specifically hydrolyzed sphingomyelin to ceramide and phosphorylcholine. Lysophosphatidylcholine was also attacked by the enzyme. The enzyme (Mr = 24 000) was maximally active at pH 6-7. Other properties of the enzyme, including hemolytic activity and activation/inhibition studies, are reported.