Dopamine produces muscle contractions and modulates motoneuron-induced contractions inAplysia gill

1. Dopamine has been reported to exist in unusually large quantities in Aplysia gill. The physiological role of this neurotransmitter in this organ was examined. 2. The addition of dopamine to a gill perfusate results in the contractions of the lateral and medial external pinnule muscles, the circular and longitudinal muscles of the afferent vessel, and the circular muscles of the efferent vessel. 3. Dopamine-induced contractions persist after chemical synaptic transmission is eliminated in the gill. This suggests that excitatory dopamine receptors are present on gill smooth muscle fibers themselves. 4. Dopamine also potentiates the gill response to action potentials in single identified gill motoneurons. Evidence presented suggests that muscle contractions and modulation of motoneuron contractions are independent phenomena. 5. While modulation may in part be mediated by increases in excitatory junction potential (EJP) amplitude, in many cases large increases in muscle contractions occur while the enhancement of EJPs is disproportionately small. 6. Dopamine's ability to produce muscle contractions suggests that there may be dopaminergic motoneuron innervation of the gill. We suggest that dopamine's modulatory actions may be mediated via modification of excitation-contraction coupling in smooth muscle fibers.     

Effects of heavy metals on structure,function, and metabolism of ciliated respiratory epithelium in vitro

Summary Tracheal explants were used to evaluate the relative ciliostatic and cytotoxic potential of heavy metal salts (cadmium chloride, chromium chloride, nickel chloride, and copper sulfate). Explants from hamster, rat, and guinea pig were all sensitive to the metals, though guinea pig explants showed the greatest difference between the untreated and metal treated tissues. Dosage levels were 50, 100, and 500μM, for 24 to 148 h. Cadmium caused the greatest degree of ciliostasis and cell necrosis. Copper was less toxic, and nickel and chromium caused marginal damage when tested at 100μM or lower. In each instance, damage became detectable at approximately 24 to 48 h and was nearly stabilized by 72 h. A significant loss of ciliary motion was always accompanied by a decrease in metabolic activity (dehydrogenase activity and ATP content). Transmission and scanning electron microscopy revealed a severely necrotic epithelium after exposure to cadmium, with only subtle morphological alterations after exposure to other metals. With all of the treatments there was no overt structural damage to cilia and little alteration in membranes of cells remaining in the epithelium. Some coagulation or vacuolization was noted in cadmium and copper treated explants but most cellular organelles did not display obvious damage. The most significant changes in the tracheal epithelium exposed to heavy metal salts in vitro were a loss of ciliary motion and a decrease in total ATP content. This study was supported in part by Grant HL 26880 from the National Heart, Lung and Blood Institute, Bethesda, MD.     

3H-noradrenaline metabolism in the isolated epididymal and prostatic portions of the rat vas deferens

The spontaneous ³H-noradrenaline efflux from the isolated epididymal and prostatic portions of the rat vas deferens, was investigated. The spontaneous tritium efflux was higher in the epididymal portion than in the prostatic one from normal animals. Such differences were abolished after castration. On the other hand, acetylsalicylic acid enhanced the total tritium efflux only in the epididymal portion, whereas phentolamine and phenoxybenzamine increased the total tritium efflux from the two portions of the rat vas deferens in both experimental groups. The prostatic portion released a similar amount of ³H normetanephrine than the apididymal end, whereas other metabolic fractions (3,4-dihydroxyphenylglycol; 3,4-dihydroxymandelic acid and O-methylated deaminated metabolites) were smaller in the prostatic portion in comparison with the epididymal portion from control vas deferens. The results presented in the isolated rat vas deferens suggest the existence of a prostaglandin as well as an alpha adrenoceptive modulation of the spontaneous total tritium efflux.     

Taxonomy of nonfermentative bacilli: The IIk-2 group

Twenty-two strains of the Center for Disease Control’s IIk-2 group of nonfermentative Gram-negative, weakly pigmented (yellow) bacteria were examined in respect to phenotypic features, DNA base composition, and both intra-and extra-group DNA-DNA hybridizations. Eighteen of the 22 strains appeared to be members of one taxon. This taxon is phenotypically not similar to two genera,Acinetobacter andMoraxella, which have similar base compositions. It does, however, have phenotypic features and base composition compatible with those of the genusFlavobacterium.     

Thermoregulatory behavior of juvenile cromileptes altivelis (serranidae), a tropical marine fish

Ten juvenile Cromileptes altivelis were tested individually for 3-day periods in electronic shuttleboxes to measure their thermoregulatory behavior. The fish voluntarily occupied a 21–27°C span, out of a potentially available 0–50°C range. The mean final thermal preferendum was 24.5°C for all individuals. The thermoregulatory performance of this species is similar to that of cool temperate freshwater fishes.     

Effect of temperature on locomotor activity in the goldfish (Carassius auratus) and the bluegill (Lepomis macrochirus): Presence of an ‘activity well’ in the region of the final preferendum

Goldfish (Carassius auratus) and bluegill sunfish (Lepomis macrochirus) were placed in aquaria where their locomotor activity was monitored by photocells, and tested at various acclimation temperatures over a range encompassing their final thermal preferenda. Activity was pooled over 24-hour periods to eliminate any circadian rhythm effects. Both species exhibited an activity well of reduced locomotor activity in the region of the final preferendum. Goldfish, tested either singly or in groups of 2–5 individuals, exhibited a social-interaction effect which became more pronounced at higher temperatures. These results are discussed in relation to a thermokinetic interpretation of thermo-regulatory behavior in fishes, and to the correspondence between thermal preferenda and thermal optima.     

Thermoregulatory behavior of the bluespotted sunfish,Enneacanthus Gloriousus

Twenty bluespotted sunfish, Enneacanthus gloriosus, were individually tested for thermoregulatory behavior in an electronic shuttlebox. The first fishes of this genus to be tested for thermoregulatory behavior, these individuals were captured near the northern limit of their zoogeographic range, in northeastern Pennsylvania. The mean final preferendum from pooled data of all 20 fish was 28.5°C; there were no significant differences between day and night.