The yeast G-protein homolog is involved in the mating pheromone signal transduction system.

I have isolated a new type of sterile mutant of Saccharomyces cerevisiae, carrying a single mutant allele, designated dac1, which was mapped near the centromere on chromosome VIII. The dac1 mutation caused specific defects in the pheromone responsiveness of both a and alpha cells and did not seem to be associated with any pleiotropic phenotypes. Thus, in contrast to the ste4, ste5, ste7, ste11, and ste12 mutations, the dac1 mutation had no significant effect on such constitutive functions of haploid cells as pheromone production and alpha-factor destruction. The characteristics of this phenotype suggest that the DAC1 gene encodes a component of the pheromone response pathway common to both a and alpha cells. Introduction of the GPA1 gene encoding an S. cerevisiae homolog of the alpha subunit of mammalian guanine nucleotide-binding regulatory proteins (G proteins) into sterile dac1 mutants resulted in restoration of pheromone responsiveness and mating competence to both a and alpha cells. These results suggest that the dac1 mutation is an allele of the GPA1 gene and thus provide genetic evidence that the yeast G protein homolog is directly involved in the mating pheromone signal transduction pathway.     

广东哺乳类及两栖类寄生吸虫四新种的记述（吸虫纲：蹲茎科,蛙蠕科）

作者在广东省梅县市发现四个吸虫新种:1.鼠丽色吸虫,新种Reesella ratta sp. nov., 2.后囊蛙蠕吸虫,新种Batrachotrema optstosacca sp. nov., 3.梅县后平睾吸虫,新种Opisthioparorchis meixianensis sp. nov., 4.大卵后平睾吸虫,新种Opisthioparorchis megaloonos sp. nov.,它们分别归隶于蹲茎科Cathaemasiidae及蛙蠕科Bstrachotrematidae。模式标本保存于中山医科大学寄生虫学研究所。     

Chronopharmacological study of furosemide in rats: (II). Influence of beta-adrenoceptor blockade

We have previously demonstrated a time-dependent variability in the diuretic effect of furosemide in rats. The present study was undertaken to evaluate the influence of beta-adrenoceptor blockade on these time-dependent variations. Furosemide (5 mg/kg) was administered intra-arterially in Wistar rats at 1000 hrs (03HALO) or at 2200 hrs (15HALO) with pretreatment with either propranolol (10 mg/kg) or atenolol (10 mg/kg). Urine was collected for 60 min after furosemide administration and urinary excretion of sodium and furosemide were determined respectively. Propranolol pretreatment abolished the temporal variations observed in urine volume, urinary sodium and furosemide levels during the observation periods. With atenolol pretreatment, however, all these variables were significantly greater at 1000 hrs (03HALO) than at 2200 hrs (15HALO) as observed in the previous study. These results suggest that the beta-adrenoceptor-mediated stimuli, which is blocked by propranolol but not by atenolol, is responsible for the time-dependent changes in the diuretic effect of furosemide.     

Secondary release of thromboxane A2 in aerosol leukotriene C4-induced bronchoconstriction in guinea pigs

Effect of a thromboxane synthetase inhibitor (OKY-046) on bronchoconstriction induced by aerosol leukotriene C4 and histamine was studied in anesthetized, artificially ventilated guinea pigs in order to examine whether secondary release of thromboxane A2 is produced by aerosol leukotriene C4 or not. 0.01–1.0μg/ml of leukotriene C4 and 12.5–400μg/ml of histamine inhaled from ultrasonic nebulizer developed for small animals caused dose-dependent increase of pressure at airway opening (Pao) which is considered to be an index representing bronchial response. Pretreatment of the animals with intravenous OKY-046 (100mg/kg) significantly reduced the airway responses produced by inhalation of 0.1, 0.33 and 1.0μg/ml of leukotriene C4, while the pretreatment did not affect the histamine dose-response curve. Based on these findings and previous reports (6, 7), it is suggested that aerosol leukotriene C4 activates arachidonate cyclooxygenase pathway including thromboxane A2 synthesis and the released cyclooxygenase products have bronchodilating effect as a whole     

Chronopharmacology of trichlormethiazide in rats; (II). Examination in aged rats

We have previously demonstrated a time-dependent variability in the diuretic effects of trichlormethiazide, a thiazide diuretic agent, in young rats. The study suggested that the time-dependent variations in urinary trichlormethiazide and susceptibility of renal tissues to the agent might be involved in this phenomenon. The present study was undertaken to test a hypothesis that such a daily variation in the effects of trichlormethiazide is blunted by age. Trichlormethiazide (0.5 and 2.0 mg/kg) was given orally at 1200 hrs (day trial) or at 2400 hrs (night trial) in young (10-11 week old) and aged (23-24 month old) Wistar rats. Urine was collected for 8 hours after the agent and urinary excretions of sodium, chloride and trichlormethiazide were determined. Urine volume and urinary excretions of sodium, chloride and trichlormethiazide following the agent were significantly greater at 1200 hrs than at 2400 hrs in the young rats. However these administration time-dependent changes in the effects of trichlormethiazide and its urinary amount diminished in the aged rats. In the day and night trials, there were significant correlations between urinary trichlormethiazide and its effects (urine volume, urinary sodium and chloride) in both groups of rats. The regression lines in each parameter of two trials differed in the young, but not in the aged group of rats. These data indicate that the mode of the time-dependent changes in the effects of trichlormethiazide is altered in aged Wistar rats. Dampening of the time-dependent variations in urinary trichlormethiazide and susceptibility to the agent might be involved in these chronopharmacological alterations in aged rats.     

Chronopharmacological study of furosemide; (VIII) influence of feeding restriction

We have previously reported that a time-dependent variation is observed in the diuretic effect of furosemide and the light-dark cycle is a potent zeitgeber for this chronopharmacological phenomenon of the agent in rats. The present study was undertaken to examine whether a time of food intake is another zeitgeber for this event. In study I, rats were maintained with free access to food for 3 weeks. Furosemide (30 mg/kg) was given orally at 12 am or 12 pm. Urine was collected for 8 hours after the agent and urinary excretion of sodium and furosemide were determined. Thereafter, these rats were maintained under a daytime-restricted feeding schedule (9 am-11 am) for 3 weeks (study II) and a night-time-restricted feeding schedule (9 pm-11 pm) for 3 weeks (study III). The identical protocol of study I was repeated at the end of study II and III. Diuretic effect of furosemide and its urinary excretion were significantly greater at 12 am than at 12 pm in study I and III. However such an administration time-dependent change in the effect of furosemide and its urinary amount disappeared in study II. These data indicate that a time of food intake is another potent zeitgeber for the time-dependent variation in the diuretic effect of furosemide.     

von Willebrand factor. A reduced and alkylated 52/48-kDa fragment beginning at amino acid residue 449 contains the domain interacting with platelet glycoprotein Ib

We have purified a reduced and alkylated tryptic fragment of von Willebrand factor (vWF) which migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a 52/48-kDa doublet, but behaved as a single 46-kDa species after partial deglycosylation. After extensive treatment with denaturants, the 52/48-kDa polypeptide retained its ability to inhibit ristocetin-induced platelet aggregation in the presence of native vWF, as well as aggregation induced by desialylated vWF alone. Therefore, the 52/48-kDa polypeptide interacts with the platelet glycoprotein Ib receptor even in the absence of ristocetin. Both the 52/48- and the 46-kDa species inhibited ristocetin-induced binding of the intact molecule to platelets, but did not affect thrombin-induced binding. Determination of the NH2-terminal sequence of both members of the doublet gave identical results: VTLNPSDPEHCQ. This provided additional evidence that differences between the doublet constituents were only of carbohydrate composition and established the position of this peptide within the vWF polypeptide chain of approximately 2050 amino acid residues as beginning with the residue tentatively designated 449. These studies suggest that native conformation is not necessary for binding of vWF to platelets at the glycoprotein Ib receptor and that a linear amino acid sequence following residue 449 defines a domain responsible for this interaction.     

Physical locus of the DNA polymerase gene and genetic maps of bacteriophage T5 mutants.

Segments of DNA that contained the DNA polymerase gene of bacteriophage T5 were isolated. The physical locus of the gene was identified by transforming Escherichia coli with purified DNA fragments generated by restriction enzyme digestions, and the transformed cells were used to rescue amber mutants of T5 with mutations in the gene for DNA polymerase. The method is applicable to any other gene that has mutations with low reversion frequencies. We studied the following mutations of the T5 DNA polymerase gene, reading from left to right by the standard convention (D. J. McCorquodale, Crit. Rev. Microbiol. 4:101-159, 1975): D7, D8, aml, ts5E-ts53, am6, and D9. These loci were found to reside within three pieces of DNA with a total length of 3,600 base pairs. Because the structural gene for T5 DNA polymerase is estimated to be 2,600 base pairs long, the whole structural gene may reside in these segments. These are located 58.3 to 61.3% of the distance from the left end of the DNA. The left-end piece of the DNA (1,100 base pairs) containing the polymerase gene has loci D7 and D8, and the right-end piece (1,600 base pairs) has locus D9, according to the results of the transformation assay. These results are consistent with the genetic map.     

Multiple catalytic properties of the purified and reconstituted cytochrome P-450 (P-450sccII) system of pig testis microsomes

The catalytic properties of the testis microsomal P-450, termed P-450sccII, have been studied in a refined assay system which consists of P-450sccII (13 nmol of P-450 heme/mg of protein) and its reductase has been purified extensively from pig testis. The results indicated that P-450sccII was highly active in catalyzing hydroxylation of 11 beta-hydroxyprogesterone at the 17 alpha-position to give 21-deoxycortisol and cleavage of 17 alpha-hydroxyprogesterone at the 17-20 bond to give androstenedione with turnover numbers of 25 and 30 mol/min X mol of P-450, respectively. In contrast, many physiologically important corticosteroids we tested were found to be poor substrates for both the hydroxylase and lyase reactions. The possible reason for the importance of these substrate specificity of P-450sccII in production of both corticosteroids and androgens in the endocrine tissues is discussed. P-450sccII also catalyzed conversion of testosterone to androstenedione, but 18O experiments failed to show incorporation of atmospheric oxygen into the androstenedione formed. However, this does not preclude the possibility that the P-450-bound intermediate gem-diol stereoselectively dehydrates to give the nonlabeled ketosteroid. In addition to these steroid-oxidizing activities, P-450sccII revealed considerable specificities toward various xenobiotics, suggesting that P-450sccII and liver microsomal P-450 are basically similar as regards enzymatic functions and activities.