Effects of pup sucking behaviour on inhibition of sexual behaviour and ovulatory secretion of LH in lactating rats.

The time-interval between parturition and the display of sexual receptivity varied between 13.5 +/- 0.7 and 35.9 +/- 2.5 days in rats with litters of between 1 and 24 pups. Body weight gain decreased and the avidity of pup sucking behaviour, measured by the latency before the pups, placed on the ventrum of an anaesthetized mother, attached to a nipple of the mother, increased as litter size increased. Litter-shifting procedures, which introduced asynchrony between the lactational age of the mother and the age of the pups, produced deficiencies in sucking behaviour and did not prolong the time-interval between parturition and the display of sexual receptivity by the mother. By keeping the lactational age of the mother in synchrony with the age of the pups and depriving the pups of maternal contact and nutrition every alternate day, the time-interval between parturition and the display of sexual receptivity by the mother was prolonged by 17 days, the avidity of pup sucking behaviour markedly enhanced and the body weight gain of the pups retarded in comparison with mothers and pups continuously living together. The results show that the display of the first postlactational behavioural oestrus and surge of pituitary LH secretion can be greatly delayed by an increase in the avidity of pup sucking behaviour.

The effect of naloxone on sexual behavior in female rats depends on the site of injection.

Intraperitoneal injections of the opiate receptor antagonist naloxone (0.1, 1, 5 or 10 mg) had no effects on sexual behavior in ovariectomized female rats made either partially or fully receptive by injections of ovarian hormones. Intracerebroventricular (i.c.v.) injections of naloxone (10, 50 or 100 micrograms) had no effects on the behavior of partially receptive rats and in fully receptive rats an i.c.v. injection of a high dose of naloxone (100 micrograms) inhibited the behavior. Intrathecal (i.t.) injections of naloxone (50 or 100 micrograms) facilitated sexual behavior in partially receptive rats while i.t. injections of even very high doses of naloxone (500 micrograms) had no behavioral effects in fully receptive rats. Thus, the effects of naloxone on female sexual behavior depend on the site of injection.

[The fight over dentistry 1919-1924]. / Dentiststriden 1919-1924.

In the history of many professions there are periods of more or less pronounced borderline fights against other professions and/or charlatans. This article is about such an example from the profession of dentistry in Sweden. From the middle of the second decade of this century, there was an increasing discrepancy between the need for dental care and the too low number of dentists. Furthermore: the majority of the Swedish people could not afford dental care at all. In the public debate the concept "dental misery" was created. In 1919 a famous Swedish paediatric professor, Isak Jundell, presented a debate article in "Allmänna Svenska Läkartidningen" (Journal of the Swedish Medical Association), with a proposal for building up a corps of dental assistants with shorter training than dentists, but still with competence for tooth cleaning, extraction and some operative dentistry. The aim of the proposal was to give people easier available and cheaper dental care. The dental profession had been questioned and threatened and the reaction from the advocates of the dentists was immediate and intense. Now followed an almost five year long struggle, with the Swedish Dental Association on one side and parts of the medical profession, dental technicians, even some dentists and a number of politicians on the other. The controversy ended up in the Swedish Parliament in 1924 where many members in both the chambers had signed motions concerning authorisation of dental technicians. The dentists won the fight thanks to the resolution in the Parliament not to authorise the technicians. But still more important, from a social political point of view, was a statement from the Parliament with a commission to the Government to analyse the prerequisites for building up a Public Dental Health Service organisation in Sweden. After a series of committees this was finally a reality fourteen years later, in 1938, when the Parliament in a resolution initiated "folktandvården".

Antagonism between bacteria and fungi on decomposing aquatic plant litter.

Bacterial and fungal decomposers of aquatic plant litter may exhibit either synergistic or antagonistic interactions, which are likely to influence microbial growth as well as the decomposition of litter and, eventually, the carbon metabolism of aquatic systems. To elucidate such interactions, we inoculated decomposing Phragmites culms in microcosms with fungal isolates and with natural communities of bacteria and fungi in different combinations. The development of fungal and bacterial biomass and the carbon dynamics were studied during several months of degradation. The results show a bilateral antagonistic relationship between bacteria and fungi. After 3 months, fungal biomass accumulation was approximately 12 times higher in the absence than in the presence of bacteria. Bacterial biomass accumulation was about double in the absence of fungi compared to when fungi were present. Similar interactions developed between a natural assemblage of bacteria and five different fungal strains isolated from Phragmites litter (three identified hyphomycetes and two unidentified strains). Despite the great difference in biomass development between the treatments, the carbon metabolism was similar regardless of whether fungi and/or bacteria were present alone or in coexistence. We suggest that the antagonism between bacteria and fungi is an important controlling factor for microbial colonization and growth on aquatic plant litter.