The influence of gamma radiation on arachidonic acid release and prostacyclin synthesis

Cultured pulmonary artery endothelial cells produce PGI₂ as their primary prostaglandin. Conditions which inhibit cell division have been shown to accelerate the synthesis of this compound. Exposure of endothelial cells to γ raidation results in an irreversible cessation of growth and enhanced production of PGI₂. The level of PGI₂ measured after radiation exposure exceeds that observed in cultures rendered quiescent by serum reduction. This indicates a role for γ radiation in the elevation of PGI₂ levels which is distinct from its effect on cell division. Result presented indicate that exposure to γ radiation does not, in and of itself, elevate PG levels but capacitates cells for enhanced production when presented with appropriate stimuli. Increased PGI₂ synthesis appears to be a result of an observed increase in arachidonic acid release and an activation of cyclooxygenase.     

In situ measurement of filtering rates of the salp, Thalia democratica, on phytoplankton and bacteria

Salps were gently captured in a perspex chamber by a SCUBA diver,who then injected a suspension of ¹⁴C-labeled phytoplanktonand ³H-labeled bacteria into the chamber. After 0.5 h incubationin situ, filtering rates were estimated from incorporation ofthe two isotopes, and expressed as a function of each salp'ssize. Both bacteria and phytoplankton were grazed by Thalia,the latter at higher rates. Weight-specific grazing rates increasedwith increasing size of salp. Estimated hourly rations rangedfrom 1% of bodily C for small Thalia feeding only on phytoplanktonto 8% of bodily C for large Thalia feeding on all particulateorganic C. The method gave repeatable results for Thalia, butwas unsatisfactory for the pteropod, Cavolinia. ¹Present address: Institute of Marine Resources, A-018, Universityof California, San Diego, Scripps Institution of Oceanography,La Jolla, CA 92093, USA.     

Relationship of chin spot size to dominance in the black-chinned mouthbrooding cichlid fish (Sarotherodon melanotheron)

Aggressive interactions of male Sarotherodon melanotheron were studied to determine the communicative value of chin spot size in relation to dominance. In addition, the effects of residency and size on the aggressiveness of this fish were determined. Two-factor analysis of variance was used for frequencies of each modal action pattern for residency and size. Results show that residency played a major role in the outcome of an aggressive interaction, whereas size had little effect. Dominance of each experimental fish was calculated using Barlow & Ballin's (1976) dominance index. A chin spot ratio was obtained by dividing the chin spot area by the total surface area of the individual fish. Simple linear regression was conducted to determine if dominance and chin spot size were correlated and a positive linear relationship was found to exist between the two variables.     

Excitotoxic Brain Injury Suppresses Striatal High-Affinity Glutamate Uptake in Perinatal Rats

In immature rodent brain, the glutamate receptor agonist N-methyl-D-aspartate (NMDA) is a potent neurotoxin. In postnatal day (PND)-7 rats, intrastriatal injection of 25 nmol of NMDA results in extensive ipsilateral forebrain injury. In this study, we examined alterations in high-affinity [3H]glutamate uptake (HAGU) in NMDA-lesioned striatum. HAGU was assayed in synaptosomes, prepared from lesioned striatum, the corresponding contralateral striatum, or unlesioned controls. Twenty-four hours after NMDA injection (25 nmol), HAGU declined 44 +/- 8% in lesioned tissue, compared with the contralateral striatum (mean +/- SEM, n = 6 assays, p less than 0.006, paired t test). Doses of 5-25 nmol of NMDA resulted in increasing suppression of HAGU (5 nmol, n = 3; 12.5 nmol, n = 3; and 25 nmol, n = 5 assays; p less than 0.01, regression analysis). The temporal evolution of HAGU suppression was biphasic. There was an early transient suppression of HAGU (-28 +/- 4% at 1 h; p less than 0.03, analysis of variance, comparing changes at 0.5, 1, 2, and 3 h after lesioning); 1 or 5 days postinjury there was sustained loss of HAGU (at 5 days, -56 +/- 11%, n = 3, p less than 0.03, paired t test, lesioned versus contralateral striata).(ABSTRACT TRUNCATED AT 250 WORDS)     

Medroxyprogesterone acetate and the nuclear uptake of testosterone and its metabolites by brain, pituitary gland and genital tract in male cynomolgus monkeys.

The synthetic progestin, medroxyprogesterone acetate (MPA), is used to treat male sex offenders, and it is also suppresses sexual activity in male monkeys. To examine the possibility that MPA may act as an anti-androgen in the primate brain, 4 intact male cynomolgus monkeys were given MPA (40 mg i.m.) once a week for 16 weeks, while 4 control males received i.m. injections of vehicle. All males were then castrated and 3 days later were given 3 mCi [3H]testosterone ([3H]T) i.v.; 1 h after injection males were killed, and radioactivity in nuclear pellets obtained from the hypothalamus (HYP), preoptic area (POA), amygdala (AMG), septum, pituitary gland and genital tract was analyzed by HPLC. Concentrations of [3H]T and [3H]dihydrotestosterone in nuclear pellets were 65-96% lower in MPA-treated males than in controls (P less than 0.001), but the aromatized metabolite, [3H]estradiol, which was the major form of radioactivity present in nuclear pellets from HYP, POA and AMG, was unchanged. There were no differences in concentrations of [3H]T in supernatants from the tissues of MPA-treated and control males. Because the reduced nuclear uptake of androgen in brain occurred in males whose androgen-dependent behavior had been suppressed by MPA treatments, it is proposed that MPA may have anti-androgenic effects at the level of the cell nucleus in brain regions that control behavior.     

Factors affecting the reproductive success of the crab spider Misumenoides formosipes: the covariance between juvenile and adult traits

Summary To examine the importance of covariance between stages in traits related to foraging, we quantified the relationships between reproductive success and sizerelated variability in weight gain in juvenile and adult instars of the crab spider Misumenoides formosipes (Araneae: Thomisidae). Prereproductive weight and fecundity are both highly correlated with carapace width, a linear measure of size which does not change within an instar. In field populations, adult females with larger carapaces gain more weight and are more likely to reproduce than females with smaller carapaces. The growth rate of spiders fed ad libitum in the laboratory is unrelated to size, suggesting that size-related differences in the field are due to variation in prey-capture success. Adult females with a carapace width less than 3.4 mm comprised 22% of the population, but were never found to reproduce. Of the individuals that did reproduce, a 17% increase in carapace width resulted in a 100% increase in fecundity. Juvenile stages must be examined to understand adult foraging and reproductive success, because the net weight gained by juvenile instars determines adult size. The final weight gained by spiders in the antepenultimate and penultimate instars explained nearly all the variation in carapace width in the penultimate and adult instars, respectively. We found that constraints on foraging in late juvenile stages are different from the adult stage. Penultimate foraging behavior differs from that of adults, because of constraints on foraging in the period preceding ecdysis. Additionally, in both late juvenile instars, carapace width had little or no effect on the final weight gained within the instar suggesting that factors that affect foraging are different between the juvenile and adult stages. These analyses stress the fact that to fully understand the effects of foraging on reproductive success, we must examine stage-specific constraints throughout an organism's life history.     

A METHOD FOR ESTIMATING MASS OF LARGE PINNIPEDS

Fifty-two male elephant seals were weighed and photographed at Año Nuevo State Reserve, California, to establish a predictive relationship between photographically measured morphological variables (length, side area, and girth area) and body mass. Regression of mass on these variables revealed that side area, roughly equivalent to a longitudinal cross-section, was the most useful single variable for predicting mass, and that adding the other two variables to side area slightly improved the accuracy of the photogrammetric technique. Curvilinear regressions based on a power model provided the best predictive relationships. This technique may prove useful for estimating body mass of other pinnipeds.     

Histidine utilization by Alcaligenes eutrophus: Regulation of histidase formation under heterotrophic conditions of growth

Histidine supported good growth of Alcaligenes eutrophus strain H 16 as a nitrogen source, but only poor growth as a carbon and energy source. The facultative chemolithoautotrophic bacterium was also able to utilize urocanic acid, the first intermediate of histidine catabolism. The products of histidine degradation were ammonium, formate and glutamate. Three enzymes of the pathway, histidase, urocanase and formiminoglutamate hydrolase, were present in histidine-grown cells. Two types of spontaneous mutants, derived from the wild type, were characterized by an increased growth rate on histidine. One of these types was found to produce histidase constitutively and at a higher activity compared with the parental strain. The second type of mutant had apparently gained an improved histidine uptake system, which is supposed to be growth rate-limiting in the wild type. From the physiological studies the conclusion was drawn that the control of histidine-degrading enzymes is based on induction by urocanate and catabolite repression by carbon sources supporting fast growth, such as succinate or pyruvate. Ammonium was found not to affect catabolite repression, however, we obtained evidence that histidine uptake is subject to a nitrogen control.Abbreviation CTAB hexadecyltrimethylammonium bromide