Nonhormonal basis of maternal behavior in the rat

Rats were tested for induction of maternal behavior by exposing them to young pups continously for 10 to 15 days. Nonpregnant intact, ovariecto-mized. and hypophysectomized females were studied, as well as intact and castrated males. Nearly all the animals exhibited the four main items of maternal behavior and there were only minor differences in the latencies for the onset of maternal behavior among the various groups. It is concluded that all rats have a basic level of maternal responsiveness which is independent of hormonal stimulation.     

Inhibitory centers in sexual behavior in the male rat

Small lesions placed near the diencephalic, mesencephalic junction, in either the lateral or medial mammillary region, resulted in an increase of copulatory behavior. This increase was expressed both by increased numbers of copulation plugs formed per 14-day interval and by increased percentage of days on which copulation occurred. Inhibitory structures thus form an essential part of the circuitry involved in mediation of sex behavior in the male.     

Maternal behavior in the rat: facilitation through gonadectomy

Virgin rats were ovariectomized and tested for induction of maternal behavior by being housed with neonatal young. A postoperative interval of 8 weeks yielded an average latency for the onset of maternal behavior significantly lower than that for intact controls or for virgin females ovariectomized 4 weeks before testing. Replacement of estrogen in the group ovariectomized for 8 weeks or injection of the estrogen antagonist ethamoxytriphetol (MER-25) in the group ovariectomized for 4 weeks changed the average latencies accordingly. Parallel results were obtained for males that were castrated 4 or 8 weeks before testing. It is concluded (i) that maternal behavior is under gonadal control and that this control is normally inhibitory; and (ii) that only after long-term removal of the gonads, resulting presumably in the complete clearance of estrogen and testosterone, is the maternal mediating system finally released from steroid suppression.     

Estrous cycle in the rat: effects on self-stimulation behavior

The performance of female rats, in pressing a bar for electrical stimulation of the hypothalamus, changes during the estrous cycle. Highest barpressing rates accompany the appearance of vaginal cornification. This increase is not an artifact of increased spontaneous activity at estrus, although the factors underlying these changes in activity may also mediate the changes in self-stimulation behavior.     

Operant behavior changes norepinephrine metabolism in rat brain

Rats performing a lever-pressing response for water reward in an operant situation, when compared with control groups, showed an increase in brain norepinephrine metabolism. One control group included rats which were handled and deprived of water in the same way as the experimental group but were not trained to perform the operant task. We conclude that performance in an operant situation affects norepinephrine metabolism.     

Agnonistic behavior in organized and disorganized cotton rat populations

Agonistic interaction rate is significantly lower in groups of caged cotton rats (Sigmodon hispidus) from naturally occurring organized populations than in groups composed of strangers. Some type of social structure is apparently present between animals sharing a common area under natural conditions. After a 24-hour period, there is no significant difference in the behavior of the two groups, an indication that a social structure is rapidly formed in the disorganized groups.     

Sexual behavior: ultrasonic postejaculatory song of the male rat

During the refractory period that follows ejaculation, the male rat regularly emits 22-kilohertz vocalizations. These cease after about three-fourths of the total period has elapsed, and this corresponds to an "absolute refractory period" during which the male cannot spontaneously initiate copulation. Similar 22-kilohertz vocalizations occur in other social contexts, and in general they appear to be desist-contact signals.     

Prenatal alcohol exposure alters adult expression of sexually dimorphic behavior in the rat

Saccharin preference and performance in a Lashley III maze were found to be altered in adult male and female rats that had been exposed to alcohol during gestation. Specifically, the sexual dimorphism normally observed in both behaviors was absent in fetal alcohol-exposed animals. The lack of sexual dimorphism appeared to result from a masculinization of the exposed females and a feminization of the exposed males.     

Evidence for mate fidelity in the gray seal

Colonially breeding gray seals are polygynous. Males are larger than females, compete with each other for position among aggregated females, and contribute no parental care. Genetic analysis of pups born on the island of North Rona, Scotland, reveals large numbers of full siblings, although dominant males father disproportionately few of these. This result cannot be explained by mating patterns based solely on male dominance and the spatio-temporal organization of the breeding colony. Instead, many full siblings must result from choices favoring previous parental combinations. Thus, polygyny and partner fidelity appear to operate simultaneously in this breeding colony.     

Mating behavior: facilitation in the female rat after cortical application of potassium chloride

Mating behavior in ovariectomized female rats treated with estrogen can be greatly enhanced by subcutaneous injections of progesterone. Application of potassium chloride to the cortex of females previously treated with estrogen can also induce greatly increased sexual receptivity as indicated by the lordosis response. This facilitation of mating behavior by a treatment known to cause functional decortication suggests that mechanisms mediating female mating behavior are under tonic inhibition by an inhibitory system which involves the cerebral cortex.     

Evidence for olfactory function in utero

Pregnant rats received 2-[14C]deoxy-D-glucose (2DG) intravenously on the last day of gestation, and their fetuses were delivered 1 hour later by cesarean section. Fetal brains showed high 2DG uptake spread throughout the accessory olfactory bulb and little or no differential uptake in the main olfactory bulb. These findings demonstrate that functional activity occurs in the accessory olfactory bulb in utero and suggest that the accessory olfactory system may be the pathway by which fetal rats detect the odor quality of their intrauterine milieu.     

Evidence for new sources of NOX in the lower atmosphere

Laboratory studies show that the reaction of short-lived O2(B3Sigmau) molecules (lifetime approximately 10 picoseconds) with N2 and the photodissociation of the N2:O2 dimer produce NOx in the stratosphere at a rate comparable to the oxidation of N2O by O(1D). This finding implies the existence of unidentified NOX sinks in the stratosphere. The NO2 observed in this experiment is isotopically heavy with a large 15N/14N enhancement. However, photodissociation of this NO2 unexpectedly produced NO molecules with a low 15N/14N ratio. The diurnal odd-nitrogen cycle in the stratosphere will be marked by a complex isotope signature that will be imprinted on the halogen and HOX catalytic cycles.     

Scheiner's Halo: Evidence for Ice Ic in the Atmosphere

Refraction of sunlight at the angle of minimum deviation between octahedral faces of crystals of ice Ic in the upper atmosphere could produce a halo around the sun or the moon at 27.46 degrees . Crystals of hexagonal ice having low-index faces cannot produce a halo of this radius. It is therefore suggested that Scheiner's halo, which has been reported at least four times since 1629 at 28 degrees from the sun, is due to ice Ic. If this is correct, it is apparently the first evidence that ice Ic occurs naturally and that liquid water can freeze to ice Ic.     

Evidence for the effects of a superantigen in rheumatoid arthritis

While studying the alpha beta T cell receptor repertoire in rheumatoid arthritis (RA) patients, we found that the frequency of V beta 14+ T cells was significantly higher in the synovial fluid of affected joints than in the peripheral blood. In fact, V beta 14+ T cells were virtually undetectable in the peripheral blood of a majority of these RA patients. beta-chain sequences indicated that one or a few clones dominated the V beta 14+ population in the synovial fluid of individual RA patients, whereas oligoclonality was less marked for other V beta's and for V beta 14 in other types of inflammatory arthritis. These results implicate V beta 14-bearing T cells in the pathology of RA. They also suggest that the etiology of RA may involve initial activation of V beta 14+ T cells by a V beta 14-specific superantigen with subsequent recruitment of a few activated autoreactive v beta 14+ T cell clones to the joints while the majority of other V beta 14+ T cells disappear.     

Norepinephrine-sensitive adenylate cyclases in rat brain: relation to behavior and tyrosine hydroxylase

Responses of norepiniephrine sensitive adeniosinie 3',5'-monophosphate (cyclic AMP)-generating systems in combined midbrain-striatal slices of four rat strains correlate positively with spontaneous behavioral activity and negatively with levels of midbrain and striatal tyrosine hydroxylase. Responses of cerebral cortical norepinephrine-sensitive cyclic AMP systems correlate negatively with spontaneous behavioral activity antd positively with midbrain and striatal tyrosine hydroxylase. Such correlations were not found with responses of the cyclic AMP- generatinlg systems to isoproterenol, adenosine. veratridine or of an adenosne and norepinephrine combination.     

Evidence for black holes

Black holes are common objects in the universe. Each galaxy contains large numbers-perhaps millions-of stellar-mass black holes, each the remnant of a massive star. In addition, nearly every galaxy contains a supermassive black hole at its center, with a mass ranging from millions to billions of solar masses. This review discusses the demographics of black holes, the ways in which they interact with their environment, factors that may regulate their formation and growth, and progress toward determining whether these objects really warp spacetime as predicted by the general theory of relativity.