The role of GABA in dyskinesias induced by chemical stimulation of the striatum

The gamma aminobutyric acid (GABA) antagonists picrotoxin and bicuculline were injected into the striatum of rats via chronic cannulae. Dyskinesias were produced by these drugs which could be blocked by their injection combined with GABA. The intrastriatal (i.s.) injection of a cholinergic drug, carbachol, also produced dyskinesias which were blocked by GABA. The use of i.s. injection of GABA antagonists to produce an animal model of Huntington's chorea is discussed.     

Effect of extracellular pH on growth and proton motive force of Bacteroides succinogenes, a cellulolytic ruminal bacterium.

The utilization of cellulose or cellobiose by Bacteroides succinogenes S85 was severely inhibited at pH values of less than 5.7. Since low pH inhibited the utilization of both cellobiose and cellulose, changes in cellulase activity could not explain the effect. At an extracellular pH of 6.9, the pH gradient (delta pH) across the cell membrane was only 0.07 U. As extracellular pH declined from 6.9 to 5.7, intracellular pH decreased to a smaller extent than extracellular pH and delta pH increased. Below pH 5.7, there was a linear and nearly proportional decrease in intracellular pH. B. succinogenes took up the lipophilic cation tetraphenylphosphonium ion (TPP+) in the presence of cellobiose, and uptake was sensitive to the ionophore valinomycin. As pH was decreased with phosphoric acid, the cells lost TPP+ and electrical potential, delta psi, decreased. From extracellular pH 6.9 to 5.7, the decrease in delta psi was compensated for by an increase in delta pH, and the proton motive force ranged from 152 to 158 mV. At a pH of less than 5.7, there was a large decrease in proton motive force, and this decrease corresponded to the inhibition of cellobiose utilization.     

Control of a teleost social signal

Territorial male Haplochromis burtoni (Teleostei; Cichlidae) have a dark facial stripe, the 'eyebar', which can appear and disappear within seconds, independently of other coloration patterns. It is used to signal territory ownership and aggressive intent. Some males, called 'barless', have functional melanophores in the eyebar region but never display this pattern, because melanin in eyebar pigment cells is never dispersed. The eyebar melanophores are controlled by a specialized branch of the maxillary nerve. Lesioning the 'eyebar nerve' resulted in immediate melanin dispersion and consequent darkening of the eyebar pattern, and it abolished the normal paling response in all behavioral situations. Nerve lesion produced similar results in both barred and barless males, except that the coloration of the denervated eyebar in barless males was more similar to camouflage markings than to the conspicuous black eyebar used as a social signal. Electrical stimulation of the maxillary nerve produced melanin aggregation. Photoelectric recordings of this paling response revealed no differences between barred and barless males, or between the eyebar and other facial chromatophores that do not function as visual displays. Thus, the difference in the physiological state of eyebar melanophores in intact barred and barless males cannot be explained by differences in peripheral nerve anatomy or physiology.     

Epidemiology of tegumentary leishmaniasis in Mérida, Venezuela. I. Diversity and dispersion of phlebotomine species at 3 altitude levels and its possible role in the transmission of the disease

As part of an epidemiological study on leishmaniasis in Merida, Venezuela, the diversity and dispersion of sandflies species found in 15 localities between 175 m and 1,960 m.a.s.l., are presented. From 7,126 collected sandflies (5,132 female and 1,994 male), 24 species were identified, 10 of them recognized as anthropophilic. The relation species-altitude is presented, and the species composition found in human dwellings, periodomestic and sylvatic areas, are recorded. The possible role of the identified species on the transmission of leishmaniasis in the andean region, is discussed.     

Evaluation of a possible functional relationship between chemical structure of intestinal brush border and immunity to Trichinella spiralis in the rat

Primary exposure to Trichinella spiralis in the rat, while immunizing against reinfection, induces changes in the carbohydrate structure of intestinal brush border membranes. Immunity is expressed in heightened resistance to mucosal invasion by L1 larvae, and the change in structure is evident in reduced membrane binding of the lectin, wheat germ agglutinin. The possibility that altered membrane composition is a requisite for expression of immunity was hypothesized and this was evaluated by correlating the maximum, specific binding of wheat germ agglutinin by isolated brush border membranes with (1) the expression of immunity acquired passively through serum transfer, and (2) the loss of immunity acquired from serial infections terminated in the intestinal phase. The hypothesis was further evaluated by determining whether the change in membrane structure represents a stimulus-specific response. We observed that (1) passively acquired immunity was not associated with a reduction in lectin binding and (2) short-term exposure to the intestinal stages of T. spiralis led to a reduction in lectin binding that was detectable at a time when rats were incapable of resisting reinfection. The change in lectin binding associated with trichinosis also accompanied infection with Nippostrongylus brasiliensis. Results uniformly support the conclusion that immunity to T. spiralis is independent of brush border membrane changes reflected in reduced binding of wheat germ agglutinin.     

Further observations of stage-specific effects seen after short-term hypophysectomy in the rat.

Although hypophysectomy has been a popular tool to study the effects of hormone deprivation as well as concomitant or subsequent hormone supplementation, there is relatively little morphological information available on the structural manifestation of pituitary removal on the testis. In the report, changes, in addition to those previously reported after short-term (6 days) hypophysectomy in the rat (Russell and Clermont, 1977), are described. Membrane-bound vacuoles (primarily) appeared within the basal region of the Sertoli cell at approximately the level of Sertoli-Sertoli junctions. In stages VIII through XI elongating spermatids were abnormal and manifested manchette indentation of the nucleus, a variety of other abnormal head shapes, acrosomal breaks and enlargement of the subacrosomal space. These defects were interpreted as the effect of declining hormonal levels in stage VII on spermatids that had survived the stage VII hormone sensitivity known to occur with severe hormone depletion. Abnormalities in the flagellum involving the mitochondrial sheath and fibrous sheath were detected. Preleptotene spermatocytes degenerated and could be identified in the process of doing so near the base of the seminiferous epithelium. The contact of preleptotene spermatocytes with the basal lamina was also significantly reduced. The results show that both Sertoli cell and germ cell abnormalities were present although germ cell abnormalities could be a secondary consequence of lack of appropriate stimulation of the Sertoli cell. Degeneration of basal compartment germ cells shows that germ cells other than those located in the adluminal compartment are vulnerable to hormonal withdrawal. The question of how hormone effects are mediated in the testis at midcycle to produce these effects is discussed.     

Effects of combined administration ofl-tryptophan and tricyclic antidepressants on α2- and β-adrenoceptors and monoamine levels in rat brain

In order to test whether co-administration of a serotonin precursor with antidepressant drugs could potentiate the effects of the antidepressants on monoamines or adrenoceptors in rat brain,l-tryptophan (20 mg/kg) was administered to rats daily for 7 or 15 days, either alone or in combination with desipramine (10 mg/ kg) or amitriptyline (10 mg/kg). After treatment withl-tryptophan for 7 days, increases were observed in rat hypothalamic and frontal cortex 5-hydroxy-3-indoleacetic acid levels as well as in hypothalamic dopamine and nucleus accumbens 3,4-dihydroxyphenylacetic acid levels. After 15 days, hippocampal -adrenoceptor density was found to be decreased. There was no evidence of potentiation of desipramine or amitriptyline action whenl-tryptophan was administered in combination with the antidepressants. On the contrary, the antidepressants appeared to interact withl-tryptophan to reduce its effects.