Imidazole antimycotics: selective inhibitors of steroid aromatization and progesterone hydroxylation

Econazole, imazalil, and prochloraz, which have broad spectrum antimycotic activity, are shown to be potent inhibitors of steroid aromatase activity of human placental microsomes. The IC50 values for the inhibition of aromatase activity by econazole, imazalil, miconazole, prochloraz, clotrimazole, ketoconazole, and aminoglutethimide are 0.03, 0.15, 0.6, 0.7, 1.8, 60, and 45 microM, respectively. Econazole and 4-hydroxyandrostenedione also inhibit the steroid aromatase activity of human fetal liver, a finding which suggests that extraplacental aromatase may have many similarities to the placental enzyme. Econazole is a more effective inhibitor of placental aromatization of 19-hydroxyandrostenedione than of androstenedione. This observation is consistent with the competitive nature of the inhibition of aromatase by imidazole antimycotic agents and the reduced affinity of the placental aromatase enzyme for 19-hydroxyandrostenedione compared to androstenedione. The effectiveness of these imidazole antimycotic agents to inhibit the multiple hydroxylations of progesterone which are catalyzed by human fetal adrenal microsomes is also defined. While all of the imidazole antimycotic agents are potent inhibitors of the 16 alpha-, 17 alpha-, and 21-hydroxylations of progesterone, selective inhibitory profiles are apparent. Ketoconazole is a most potent inhibitor of human fetal adrenal progesterone 16 alpha- and 17 alpha-hydroxylases while clotrimazole and imazalil are the most potent inhibitors of progesterone 21-hydroxylase. These results are strongly supportive that imidazole drugs are selective inhibitors not only of steroid aromatase but also of other microsomal steroid hydroxylases.     

Proteolytic activity in anther extracts of fertile and cytoplasmic male sterile petunia

Proteolytic activity is compared in anther extracts from Petunia parodii fertile and cytoplasmic male sterile lines. It is characterized relative to developmental stage of the anthers, effect of variable incubation times, pH of isolation buffers, and degradation of marker proteins. In fertile anthers, proteolytic activity increases at the end of microsporogenesis and peaks early in microgametogenesis. Degradation is most severe in extracts of fertile anthers and in high molecular weight proteins and reaches its maximum within 20 minutes. Degradation of marker proteins is greatest at pH 5.6 to 8.0 in fertile anther extracts and is eliminated under strong acid conditions (pH 2.8 to 4.0) in both fertile and cytoplasmic male sterile anther extracts. Marker proteins degrade more severely in extracts of fertile anthers; however, the order of substrate sensitivity—myosin > phosphorylase b > bovine serum albumin and ovalbumin > β-galactosidase—is the same in extracts from fertile and cytoplasmic male sterile anthers.     

Physiological Studies of Oxygen Protection Mechanisms in the Heterocysts of Anabaena cylindrica

The mechanism of O₂ protection of nitrogenase in the heterocysts of Anabaena cylindrica was studied in vivo. Resistance to O₂ inhibition of nitrogenase activity correlated with the O₂ tension of the medium in which heterocyst formation was induced. O₂ resistance also correlated with the apparent K_m for acetylene, indicating that O₂ tension may influence the development of a gas diffusion barrier in the heterocysts. The role of respiratory activity in protecting nitrogenase from O₂ that diffuses into the heterocyst was studied using inhibitors of carbon metabolism. Reductant limitation induced by 3-(3,4-dichlorophenyl)-1, 1-dimethylurea increased the O₂ sensitivity of in vivo acetylene reduction. Azide, at concentrations (30 mM) sufficient to completely inhibit dark nitrogenase activity (a process dependent on oxidative phosphorylation for its ATP supply), severely inhibited short-term light-dependent acetylene reduction in the presence of O₂ but not in its absence. After 3 h of aerobic incubation in the presence of 20 mM azide, 75% of cross-reactive component I (Fe-Mo protein) in nitrogenase was lost; less than 35% was lost under microaerophilic conditions. Sodium malonate and monofluoroacetate, inhibitors of Krebs cycle activity, had only small inhibitory effects on nitrogenase activity in the light and on cross-reactive material. The results suggest that oxygen protection is dependent on both an O₂ diffusion barrier and active respiration by the heterocyst.     

Mineralocorticoid radioreceptor assay: application to adrenal-regeneration hypertension.

Identification of unknown hormones has traditionally involved utilizing a bioassay to initially detect the hormone and to follow its purification. However, radioreceptor assays may be more useful for this purpose by offering greater sensitivity and precision. A mineralocorticoid radioreceptor assay has been developed for use in conjunction with chromatographic separation of a urinary extract to detect the presence of unknown urinary mineralocorticoids. This assay utilizes competition of the unknown steroid and aldosterone for rat renal cytoplasmic mineralocorticoid receptors to enable mineralocorticoid quantitation in aldosterone equivalents. This assay provides 100 fold increase in sensitivity and a significant increase in precision over the commonly used adrenalectomized rat bioassay. The mineralocorticoid radioreceptor assay has been utilized to assay mineralocorticoid activity in chromatographic fractions of a urinary extract from rats with regenerating adrenals. A large area of mineralocorticoid radioreceptor activity has been identified which possibly represents an unknown mineralocorticoid contributing to the etiology of adrenal regeneration hypertension. This assay is applicable to other syndromes of postulated unknown mineralocorticoid excess, such as human low renin essential hypertension. In addition, similar radioreceptor assays are applicable for the initial detection of any type of hormone activity and for the subsequent purification and identification of this hormone.     

Nucleotide sequence of a cDNA encoding porcine testis 17 alpha-hydroxylase cytochrome P-450.

We describe the isolation and characterization of a cDNA encoding the complete porcine neonatal testis 17 alpha-hydroxylase/C-17,20-lyase cytochrome P-450. The deduced amino acid sequence is 509 amino acids in length.     

中国西北沙漠夜间活动的东鳖甲属昆虫二新种(鞘翅目:拟步甲科:漠甲亚科)

记述中国西北地区东鳖甲属2新种:巴丹东鳖甲A.badainica Ba,Ren&Liu sp.nov.和古尔班东鳖甲A.gurbantunggutica Ba&Ren sp.nov.,提供了主要鉴别特征和形态图,并简要讨论了其昼夜活动规律.     

Haemosporidian Parasites of Antelopes and Other Vertebrates from Gabon,Central Africa

Re-examination, using molecular tools, of the diversity of haemosporidian parasites (among which the agents of human malaria are the best known) has generally led to rearrangements of traditional classifications. In this study, we explored the diversity of haemosporidian parasites infecting vertebrate species (particularly mammals, birds and reptiles) living in the forests of Gabon (Central Africa), by analyzing a collection of 492 bushmeat samples. We found that samples from five mammalian species (four duiker and one pangolin species), one bird and one turtle species were infected by haemosporidian parasites. In duikers (from which most of the infected specimens were obtained), we demonstrated the existence of at least two distinct parasite lineages related to Polychromophilus species (i.e., bat haemosporidian parasites) and to sauropsid Plasmodium (from birds and lizards). Molecular screening of sylvatic mosquitoes captured during a longitudinal survey revealed the presence of these haemosporidian parasite lineages also in several Anopheles species, suggesting a potential role in their transmission. Our results show that, differently from what was previously thought, several independent clades of haemosporidian parasites (family Plasmodiidae) infect mammals and are transmitted by anopheline mosquitoes.