Aggression persists after ovariectomy in female rats

Aggression occurs not only in males but also in females, however, under different sex-specific stimulus and endocrine conditions. After being housed with males, female rats exhibit frequent and intense aggressive behavior toward unfamiliar rats. However, the female residents primarily attack female intruder rats, while the male residents attack males and not females. Altering the hormonal condition of the intruders can modify the behavior that they provoke from the residents. Castration of the male intruders reduces aggression from male residents, but ovariectomy of the female intruders does not alter the behavior of the female residents. Treatment of the gonadectomized intruders with gonadal steroids significantly alters the response of the male residents. Resident-intruder aggressive behavior depends on the presence of the testes in the male residents but not on the ovaries or on lactation in the female residents. Even 7 weeks after ovariectomy the female residents continue to show aggressive behavior toward female intruders. In the same time period the castrated male residents show a marked decrease in aggressive and sexual behavior.     

Prostaglandin induction of spawning behavior in Cichlasoma bimaculatum (Pisces cichlidae)

Prostaglandin (PG) stimulates female spawning behavior in goldfish and in some other teleosts in which female reproductive behaviors consist of postovulatory oviposition acts. This study examined the effects of PG on female sexual behavior in a teleost fish, Cichlasoma bimaculatum, in which female reproductive behaviors involve both preovulatory courtship and substrate cleaning behaviors, and post-ovulatory oviposition behavior. In females of established pairs, PGF2 alpha injection (5 micrograms, im) at any stage of the spawning cycle, or in the parental phase, rapidly induced substrate cleaning which soon merged into oviposition behavior (without egg release). These results support a role for PG in oviposition behavior of Cichlasoma. However, indomethacin (1 mg, ip), a PG synthesis inhibitor, did not block oviposition in ovulated females which had begun to spawn. Indomethacin may not have lowered PG levels sufficiently. Alternatively, as shown by J.J. Polder (1971, Neth. J. Zool. 21, 265), oviposition behavior may be induced or maintained by other factors associated with the spawning situation.     

Hymenolepis diminuta: Worm loss and worm weight loss in long-term infections of the rat

Infections of one and two Hymenolepis diminuta established in newly weaned rats continued to grow for the duration of the experiment (238 days), whereas infections of 5 worms per rat became asymptotic around Day 55 postinfection and remained at or below this level thereafter as shown by biomass and mean weight per worm measurements. Infections of 50 worms established in newly weaned rats became asymptotic around Day 28 postinfection and thereafter worms were lost from the rats. Initially the biomass fell with the loss of worms, but by Day 56 a new lower biomass persisted for the remainder of the infection period. This level was maintained, despite diminishing numbers of worms, due to the growth of surviving individuals to a weight exceeding the original weight at maturity by a factor of more than 2. Experiments using rats that were mature at the time of infection demonstrated that the same response occurred, but approximately 3 weeks earlier.     

An improved purification method for cytosolic malate dehydrogenase from several sources

A new purification method for cytosolic malate dehydrogenases from several sources has been developed. The procedure, employing chromatographies on 5'AMP-Sepharose, DEAE-Sephacel and Blue-Sepharose, allows for a rapid isolation of the enzyme (approximately 40 hours), in large quantities, with good yields (45-54%). The specific activity of final preparations were around 1300 I.U./mg and were judged homogeneous by polyacrylamide gradient gel and sodium dodecyl sulfate polyacrylamide gel electrophoresis, high performance size exclusion chromatography and isoelectric focusing.