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N Lerner

Publications and source records attributed to N Lerner.

26 records · Page 2Linked to original sources
PubMed1976

Identification of two 5alpha-reduced pregnanes as major metabolites of progesterone in immature rat ovaries (1000 x g supernatant) in vitro.

Incubation of the 1000 x g supernatant obtained from 23-day-old rat ovarian homogenate with labeled progesterone resulted in the production of 3 major metabolites; 5alpha-androstane-3alpha,17beta-diol, and two 5alpha-reduced pregnanes that were identified as 3alpha-hydroxy-5alpha-pregnan-20-one and 3alpha,17alpha-dihydroxy-5alpha-pregnan-20-one. The 3alpha,17alpha-dihydroxy-5alpha-pregnan-20-one has not been hitherto isolated from mammalian ovaries. The steroids were identified by their mobilities on thin-layer and gas-liquid chromatography, by mass spectroscopy, derivative formation and by recrystallization to constant specific activity. In another experiment, incubation of the 1000 x g supernatant from 23-day-old rat ovaries with 3alpha-hydroxy-5alpha-pregnan-20-one as substrate resulted in the production of 5alpha-androstane-3alpha,17beta-diol. It is suggested that 5alpha-androstane-3alpha,17beta-diol is produced in immature rat ovaries by a pathway in which the identified 5alpha-reduced pregnanes serve as intermediates.

Androstane-3,17-diol↗
PubMed1976

Pre-ovulatory changes in steroidogenesis in ovaries from immature rats treated with pregnant mare serum gonadotrophin.

The metabolism of progesterone in the 1000 g supernatant fraction of homogenates of ovaries from PMSG-treated immature rats was determined. As early as 52 h after a single injection of 50 i.u. PMSG, still before the LH surge, 5alpha-pregnane-3alpha, 20alpha-diol was identified as the main metabolite, together with small quantities of 3alpha-hydroxy-kalpha-pregnan-20-one and 5alpha-androstane-3alpha, 17beta-diol. Similar incubations of untreated rat ovaries at the same age did not produce 5alpha-pregnane-3alpha, 20alpha-diol. The quantities of 3alpha-hydroxy-5alpha-pregnan-20-one and 5alpha-androstane-3alpha, 1mbeta-diol were reduced in PMSG-treated rat ovaries as compared with control ovaries. When progesterone metabolism was examined 64 h after PMSG administration, 5-7 h after the peak of LH surge but still before ovulation, 75% of the substrate was converted to 5alpha-pregnane-3alpha, 20alpha-diol, while 3alpha-hydroxy-5alpha-pregnan-20-one as well as 5alpha-androstane-3alpha, 17beta-diol could not be detected.

Age Factors↗
PubMedDate not supplied

Giving the older driver enough perception-reaction time.

Many types of behavior slow with age, and older drivers require more time to process information and make decisions. How greater response time requirements relate to the design of the highway environment and to features of new in-vehicle technologies is discussed. The design requirements for many different aspects of roadway geometrics and traffic control devices are based on design driver perception-reaction times. However, without knowing how much slower older drivers are than the design driver, it is difficult to determine whether they are adequately protected by current design practice and, if not, what the desired change in design should be. Attempts to address this have been hampered by the lack of directly relevant data, the situation-specific nature of certain findings, and the older driver's ability to compensate for declines in basic skills. Also discussed are the promise and problems of new in-vehicle technologies for providing the older driver with adequate time to act. These intelligent vehicle highway systems (IVHS) may speed navigational decision making and recognition of hazards and maneuver requirements. However, the possibility for interfering with quick responding also arises, and IVHS systems might disadvantage the older driver in other ways.

Aged↗