Enhanced reproductive responses to melatonin in juvenile Siberian hamsters.

Reproductive responses to melatonin (Mel) exposure were assessed in male Siberian hamsters gestated in long (16 h light/day; 16L) or short (8 h light/day; 8L) day lengths (DLs). Hamsters were maintained in constant light beginning at 14 days of age (day 14) and were infused for 3 successive days beginning on day 18, 25, or 32 with long (12 h/day) or short (6 h/day) durations of Mel or saline. Two weeks later, testis and body weights were determined. Responsiveness to Mel was enhanced in hamsters beginning shortly after weaning and was influenced by photoperiodic history. Gonadal growth in 16L hamsters was inhibited by 12-h Mel infusions initiated on day 18 or day 25, but infusions initiated on day 32 were ineffective. Hamsters gestated in 8L were not responsive to Mel treatments initiated on day 18, but discriminated 12-h from 6-h infusions at day 25 and manifested reduced gonadal growth after 12-h Mel infusions on day 32. Hamsters born in 8L to dams judged as photoinsensitive to short DLs did not respond to 12-h infusions on day 32 as inhibitory signals. We propose that maternal Mel secretion provides juvenile males with a photoperiodic history, which allows them to compare gestational with early postweaning Mel signals and thereby program seasonally appropriate developmental trajectories.

Suprachiasmatic nucleus and photoperiodic regulation of gonadal development in the Siberian hamster, Phodopus sungorus.

Photoregressed Siberian hamsters exposed at 19 days of age to constant light for 24 h manifested increased testicular development 16 days later. Hamsters that sustained lesions of the suprachiasmatic nucleus (SCN) 3 days after the light pulse had significantly heavier gonads than did sham-operated animals or hamsters pinealectomized at 19 days of age. Enhanced reproductive development after SCN ablation is not due solely to lesion-induced elimination of melatonin secretion. SCN neural activity beginning 3 days after the light pulse is not necessary for light-induced gonadal growth.

Gonadal growth and hormone concentrations in photoregressed Siberian hamsters: pinealectomy versus photostimulation.

In Siberian hamsters, long and short durations of nightly melatonin secretion are associated with testicular regression and development, respectively; surprisingly, the absence of a nightly melatonin signal induced by pinealectomy is less effective than a short (4-6 h) melatonin duration for promoting gonadal development. We compared the patterns of serum FSH and prolactin concentrations underlying pinealectomy-induced and photostimulated testicular growth in juvenile hamsters. Pinealectomy in photoinhibited hamsters on Day 18 produced significant gonadal development compared to that in short-day controls by Day 23. By Day 28, however, testes weights of pinealectomized hamsters were significantly lower than those of intact hamsters transferred to a long photoperiod. Pinealectomy was associated with significant elevations in serum FSH and prolactin concentrations over baseline by Day 21, but peak values were attenuated compared with those induced by exposure to long days. FSH titers of pinealectomized animals were significantly lower than those of photostimulated animals between Days 21 and 30 but were significantly greater on Days 35 and 40; prolactin values were comparable in pinealectomized and photostimulated hamsters between Days 21 and 25 but were significantly lower in the former group thereafter. Blunted elevation of FSH and prolactin secretion may underlie the slower rates of gonadal maturation observed in pinealectomized, juvenile hamsters. The neuroendocrine systems of pinealectomized hamsters appear to be in a state intermediate between those characteristic of hamsters kept in long and in short day lengths.

Sustained hormonal responses of Siberian hamsters (Phodopus sungorus) to a single longer day at weaning.

Siberian hamsters undergo gonadal development for several weeks after exposure to a single longer day at weaning. To characterize changes in gonadotropin secretion after a single acute light stimulus, hamsters housed in a long photoperiod (16L:8D) were given a single longer day (20L:4D) or maintained in the 16L:8D photoperiod at 19 days of age and transferred to a short photoperiod (8L:16D) on Day 20. Elevated plasma FSH concentrations were detected in male hamsters at 5, 7, and 12 but not at 17 days after the single longer day. Melatonin treatment during light exposure and on two succeeding nights blocked the stimulatory effect of light on the reproductive axis; melatonin injections limited to one night were marginally effective. Pinealectomy during the dark phase of the photocycle and the resultant truncation of the melatonin signal for one night did not stimulate a greater degree of gonadal development than pinealectomy during the light phase. We conclude that the single extra 4-h light pulse at weaning alters hypothalamic-pituitary function for approximately 2 wk. Trophic effects of the light pulse appear to be mediated by suppression of melatonin secretion for several days; one truncate melatonin signal is not sufficient to simulate the effects of a single long day on the reproductive axis.

In situ observations of aerosol and chlorine monoxide after the 1991 eruption of mount pinatubo: effect of reactions on sulfate aerosol.

Highly resolved aerosol size distributions measured from high-altitude aircraft can be used to describe the effect of the 1991 eruption of Mount Pinatubo on the stratospheric aerosol. In some air masses, aerosol mass mixing ratios increased by factors exceeding 100 and aerosol surface area concentrations increased by factors of 30 or more. Increases in aerosol surface area concentration were accompanied by increases in chlorine monoxide at mid-latitudes when confounding factors were controlled. This observation supports the assertion that reactions occurring on the aerosol can increase the fraction of stratospheric chlorine that occurs in ozone-destroying forms.

Chemical loss of ozone in the arctic polar vortex in the winter of 1991-1992.

In situ measurements of chlorine monoxide, bromine monoxide, and ozone are extrapolated globally, with the use of meteorological tracers, to infer the loss rates for ozone in the Arctic lower stratosphere during the Airborne Arctic Stratospheric Expedition II (AASE II) in the winter of 1991-1992. The analysis indicates removal of 15 to 20 percent of ambient ozone because of elevated concentrations of chlorine monoxide and bromine monoxide. Observations during AASE II define rates of removal of chlorine monoxide attributable to reaction with nitrogen dioxide (produced by photolysis of nitric acid) and to production of hydrochloric acid. Ozone loss ceased in March as concentrations of chlorine monoxide declined. Ozone losses could approach 50 percent if regeneration of nitrogen dioxide were inhibited by irreversible removal of nitrogen oxides (denitrification), as presently observed in the Antarctic, or without denitrification if inorganic chlorine concentrations were to double.

Androgenic induction of brain sexual dimorphism depends on photoperiod in meadow voles.

Male meadow voles maintained in a long photoperiod (LP) from birth have heavier brains than do females, but in short photoperiods (SP) this sex dimorphism is absent. Testosterone propionate (TP) administration on the second day of postnatal life produced significant increases in brain weight of LP but not SP females at 35 days of age. Short daylengths reduce the responsiveness of the meadow vole nervous system to the masculinizing effects of perinatal testosterone and may, in part, mediate the seasonally reduced sex difference in brain weight.

Knife cuts lateral but not dorsal to the hypothalamic paraventricular nucleus abolish gonadal responses to photoperiod in female hamsters (Mesocricetus auratus).

Horizontal and parasagittal knife cuts in the hypothalamus of female hamsters (Mesocricetus auratus) were employed to investigate the neural pathways that mediate gonadal responses to photoperiod. Bilateral horizontal knife cuts placed dorsal to the paraventricular nucleus (PVN) did not prevent short-day-induced acyclicity and uterine regression. On the other hand, regardless of photoperiod, animals with bilateral parasagittal knife cuts placed lateral to the PVN continued to exhibit regular 4-day estrous cycles and stimulated uteri. Thus, parasagittal cuts prevented the effects of short days on reproductive physiology. This finding suggests that the lateral efferent projections from the PVN represent an important component of the neural pathway mediating reproductive photoperiodism in female hamsters.

Intrafamilial associations of cholesterol and triglyceride among related and unrelated household members.

The purpose of this report was to assess intrafamilial associations of lipids between related and unrelated household members seen in the course of a population-based survey of lipids in schoolchildren and their parents. Fasting plasma total cholesterol and triglyceride levels were measured in 6,857 and 3,079 adults. Age effects were removed for each sex-race group using a third-degree polynomial regression of lipid on age; the residuals were then used as observations in the analyses. For both cholesterol and triglyceride, significant positive correlations existed between father and son, father and daughter, mother and son, and mother and daughter. For both cholesterol and triglyceride, although the mother-child correlations were stronger than those for father-child, they were not significantly different. There were no significant correlations between step, foster, or adoptive parents and children. For cholesterol in sibships of size two, intrasibship correlations for fully related siblings were 0.333, for half-sibs 0.164, and for unrelated sibs, 0.085. Consistently closer intrafamilial cholesterol and triglyceride associations between related than unrelated family members, and the strong parental effects on cholesterol and triglyceride indicate, in aggregate, that a considerable proportion of the variation of cholesterol and triglyceride can be explained by genetic factors.

Mariner 6 and mariner 7 ultraviolet spectrometer: in-flight measurements of simulated jupiter atmosphere.

An experiment has been performed in interplanetary space which closely simulates the observations that would be madef by an ultraviolet spectrometer observing the atmospheres of the jovian planets. A mixture of ammonia, nitrogen, and hydrogen was released from the Mariner spacecraft, and spectra were recorded while these gases were illuminated by sunlight. The principal emissions observed were the HI 1216-angstrom Lyman-alpha line, the H(2) B-X Lyman bands, and the NH c-a and A-X bands.

Mariner 6 and 7 ultraviolet spectrometers.

The ultraviolet spectrometers that observed the atmosphere of Mars in July and August of 1969 consist of a planetary coronagraph and an Ebert-Fastie monochromator. The spectral range 1100-4300 A was measured using two photomultiplier tubes, one with a cesium iodide photocathode, the other with a bialkali photocathode. These tubes were operated with fixed high voltage supplies and charge sensitive amplifiers. The instruments were calibrated by comparison with a tungsten lamp, a sodium salicylate screen, and a flowing nitric oxide cell. The instruments were able to satisfactorily reject off-axis light at a distance of 6600 km and measure the emission spectrum of the upper atmosphere 170 km above the surface.

Mariner 6: ultraviolet spectrum of Mars upper atmosphere.

Emission features from ionized carbon dioxide and carbon monoxide were measured in the 1900- to 4300-angstrom spectral region. The Lyman alpha 1216-angstrom line of atomic hydrogen and the 1304-, 1356-, and 2972-angstrom lines of atomic oxygen were observed.

Ultraviolet Emissions Observed near Venus from Mariner V.

A Lyman-alpha airglow of atomic hydrogen measured in the outer atmosphere of Venus showed that atomic hydrogen is present. The variation as a function of height indicates that the temperature of the upper atmosphere of Venus is lower than that of Earth. An ultraviolet airglow of atomic oxygen was not found. An ultraviolet nightglow was observed on the dark limb.