The role of environmental sodium chloride relative to calcium in gill morphology of freshwater salmonid fish

Summary Ultrastructure, distribution and abundance of cell types were examined in the gills of two freshwater salmonid species, Salmo fario and Salmo gairdneri, in media of selected ion content. In plain hard water (PW) with high concentrations of Ca²⁺, Na⁺, and Cl^-, gill chloride cells (CC) were confined to trailing edges and interlamellar regions of filaments whereas in mountain soft water (MW) with low concentrations of Ca²⁺, Na⁺, and Cl^-, CC were more numerous on filaments and covered lamellae, particularly along trailing edges. CC also appeared on lamellae of PW trout acclimated to soft water in a pond. This proliferation was not alleviated when ambient Ca²⁺ levels were raised (MW + Ca²⁺) but regressed in elevated NaCl media (MW + NaCl). The regression process involved an initial covering of CC by pavement cells followed by cytolysis and then eventual disappearance of CC. In MW, mucous cells were distributed mainly on trailing edges and, to a lesser extent, leading edges of filaments; they were absent from lamellae regardless of external ion levels.The results of this study shed some light on the functional significance of CC in freshwater fish. It is suggested that proliferation of CC is an adaptive response to dilute freshwater (i.e. [NaCl]<0.1 mequiv·1^-1).     

Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance

During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports.     

Cellobiose metabolism in Erwinia: genetic study

Summary The study of mutants of Erwinia specifically unable to ferment cellobiose indicates that the mutations are clustered between arg and ile on the chromosome of this organism. In vivo cloning of the genes responsible for cellobiose utilization lead to a plasmid, pBEC2, which complements all Erwinia Clb^- specific mutants. When introduced into wild-type E. coli it allows this organism to use cellobiose, arbutin and salicin; it also complements bglB and bglC mutants of Escherichia coli indicating that arbutin and salicin utilization is due to the products of the pBEC2 cloned genes. From the characterization of mutants pleiotropically affected in the utilization of various carbon sources, including cellobiose, arbutin and salicin, it is proposed that the three--glucosides are substrates of the phosphoenolpyruvate-dependent phosphotransferase system (PTS).     

Stimulation par la lumière rouge lointain de la synthèse de la δ-aminolévulinate déshydratase des cotylédons de radis

Stimulation of de novo synthesis of δ-aminolevulinate dehydralasc of radishes grown under far-red light .
Density labelling studies of δ-aminolevulinate dehydratase (ALAD) in cotyledons of radish ( Raphanus sativus L. cv. Longue Rave Saumonée) seedlings demonstrate that far-red light stimulates de novo synthesis of ALAD and that the turn-over of this enzyme is very poor. Cycloheximide reduces considerably both the increase of ALAD activity and the incorporation of deuterium in ALAD, which indicates that ALAD synthesis depends upon cytoplasmic ribosomes.     

Use of microcalorimetry for the characterization of marine metabolic activity at the water-sediment interface

Metabolic processes occurring at the sea-water-sediment interface were studied using a circulation flow microcalorimeter. A methodology was developed to characterize rapid and global changes in metabolism and energy flow, not easily detectable with reductionist approaches. Sea water was pumped continuously, 5–10 mm above the sediment, in experimental microcosms; a 100-μm filter prevented passage of meiofauna. This “circulating interface” was taken through the microcalorimeter and from there to an oxygen electrode, and was returned to the microcosm. The microcosms were experimentally eutrophicated using peptone (4 mg·ml ^?1). The relationship between heat production and oxygen tension in the circulating interface has been compared with ATP production, ¹⁴CO₂ and [¹⁴C]particulate matter turnovers. Initial heat steady-state production rises to a peak of 130 to 180 μW·ml^?1 in 6 to 8 h after peptone treatment. The microcalorimetric peak is closely correlated with ¹⁴CO₂ turnover and partially correlated with micro-events on the pO₂ curve. ATP concentration and particulate-¹⁴C turnover increase constantly and then stabilize, with the establishment of a new heat production steady state. The approach provides an indication of the temporal behaviour of complex mixtures of microorganisms and ciliates at the water-sediment interface, and gives holistic measurements of energy flow after induced perturbation (eutrophication) of the ecosystem. Although many problems remain to be solved in this field, it is shown here that flow microcalorimetric measurements can be used to monitor the effects of addition of reagents like pollutants and nutrients.     

Biological and physical properties of a beta-endorphin analog containing only D-amino acids in the amphiphilic helical segment 13-31

Our approach to the modeling of beta-endorphin has been based on the proposal that three basic structural units can be distinguished in the natural peptide hormone: a highly specific opiate recognition sequence at the N terminus (residues 1-5) connected via a hydrophilic link (residues 6-12) to a potential amphiphilic helix in the C-terminal residues 13-31. Our previous studies showed the validity of this approach and have demonstrated the importance of the amphiphilic helical structure in the C terminus of beta-endorphin. The present model, peptide 5, has been designed in order to evaluate further the requirements of the amphiphilic secondary structure as well as to determine the importance of this basic structural element as compared to more specific structural features which might occur in the C-terminal segment. For these reasons, peptide 5 retains the three structural units previously postulated for beta-endorphin; the major difference with regard to previous models is that the whole C-terminal segment, residues 13-31, has been built using only D-amino acids. In aqueous buffered solutions as well as in 2,2,2-trifluoroethanol-containing solutions, the CD spectra of peptide 5 show the presence of a considerable amount of left-handed helical structure. Enzymatic degradation studies employing rat brain homogenate indicate that peptide 5 is stable in this milieu. In delta- and mu-opiate receptor-binding assays, peptide 5 shows a slightly higher affinity than beta-endorphin for both receptors while retaining the same delta/mu selectivity. In opiate assays on the guinea pig ileum, the potency of peptide 5 is twice that of beta-endorphin. In the rat vas deferens assay, which is very specific for beta-endorphin, peptide 5 displays mixed agonist-antagonist activity. Most remarkably, peptide 5 displays a potent opiate analgesic effect when injected intracerebroventricularly into mice. At equal doses, the analgesic effect of peptide 5 is less than that of beta-endorphin (10-15%) but longer lasting. In conjunction with our previous model studies, these results clearly demonstrate that the amphiphilic helical structure in the C terminus of beta-endorphin is of predominant importance with regard to activity in rat vas deferens and analgesic assays. The similarity between the in vitro and in vivo opiate activities of beta-endorphin and peptide 5, when compared to the drastic change in chirality in the latter model, demonstrates that even a left-handed amphiphilic helix formed by D-amino acids can function satisfactorily as a structural unit in a beta-endorphin-like peptide.