Intracellular Ca2+ concentration and the antidiuretic hormone-induced increase in water permeability: effects of ionophore A23187 and quinidine

The hydroosmotic responses induced by oxytocin and 8-bromo-cyclic AMP, in frog and toad urinary bladders, were recorded minute by minute. 3HHO and 45Ca unidirectional fluxes as well as prostaglandin B2 liberation were also measured. It was observed that: (1) Addition of the calcium ionophore A23187 or quinidine to the serosal bath inhibited the response to oxytocin, but not to 8-bromo-cyclic AMP, while increasing prostaglandin E1 liberation into the serosal but not into the mucosal bath. (2) Addition of A23187 to the mucosal bath induced a transient and temperature-dependent inhibition of the response elicited by 8-bromo-cyclic AMP. The time-course of this reduction in water permeability and its sensitivity to medium temperature were similar to those observed after the withdrawal of agonist, but clearly different of those observed after intracellular acidification. (3) The hydroosmotic response was also transitorily inhibited when the Ca2+ concentration was step-changed in the mucosal bath. (4) When added to the mucosal or to the serosal baths, the ionophore increased either the apical or the laterobasal Ca2+ permeabilities. It is concluded that manipulation of intracellular Ca2+ interferes with the hydroosmotic response at two different levels. (1) A first target point located 'pre-cyclic-AMP production'. This effect would be mediated by prostaglandin liberation. (2) A second target point located after cyclic AMP production and before the 'temperature-dependent rate-limiting step'. This effect is probably related to the mechanism controlling the insertion and removal of water channels.     

Clinal variation in carapace shape in the South American freshwater crab,Aegla uruguayana (Anomura: Aeglidae)

South America has been influenced by different geoclimatic events ever since its separation from Africa. The inland water fauna has evolved in response to the changing landscape. Currently, there are indications of variations in populations, occurring to different degrees that would indicate a clinal pattern in morphology. Among South America's fauna, the freshwater anomuran, Aegla, is an enigmatic group as a result of its endemicity and is composed of only one genus. Of all the species in this family, Aegla uruguayana has the broadest distribution. Its native habitats have been influenced by several marine transgressions during the Miocene–Quaternary Periods; thus, it is likely that their current distribution has been more recent. Its habitat spreads across a number of isolated basins and sub‐basins that display distinct degrees of isolation/connection, making clinal variation patterns in the morphology of this species possible. The present study aimed to evaluate the pattern of carapace shape variation in A. uruguayana and how it relates to the isolation and/or connection of populations from different basins and sub‐basins, allowing the determination of any extant clinal patterns. The specimens studied belong to 25 separate populations, representing all areas in which the species currently exists. A total of 523 crabs were analyzed. We identified 13 landmarks and four semi‐landmarks in the carapace. The aeglids were divided into seven size intervals to avoid an allometry effect. In each size category, shape relationships analyzed by principal component analysis suggest a geographical pattern corresponding to the distribution of the populations studied. An evaluation of covariation between body shape and geographical coordinates reveals a strong pattern and shows that population distribution had a significant effect on species morphology. Additionally, according to covariance analysis, the variation in shape was not associated with the environmental variables studied. We observed a clinal pattern throughout the species distribution, which could be attributed to genetic drift. It is possible that this process is being amplified by the geographical isolation of the basins, differences in environmental characteristics, and low dispersal ability. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 914–930.     

Modelling ultraviolet exposures in a school environment.

A technique has been developed to represent erythemally effective ultraviolet radiation exposure within a school environment. The technique models the erythemally effective exposure onto a horizontal plane representation of a mapped school environment located in Hervey Bay (25 degrees S, 153 degrees E), Australia. The input parameters used to model the ultraviolet exposures received within the school playground included the measured sky view, ground albedo and standing surface albedo. Estimates of the erythemally effective ultraviolet exposure received within the school playground during morning tea and lunch time meal breaks during a winter and summer school day are presented. The influence of tree shade and building structure was found to vary significantly with solar zenith angle modelled over the winter and summer school meal break times with horizontal plane exposures predicted to vary from between 0 and 7 SED at different locations within the playground. The technique presented provides a method that can be followed to examine the effect of surrounding buildings and surface structures of real environments on the predicted horizontal plane ultraviolet exposure.     

Studies on evolutionary and selective properties of hypercycles using a Monte Carlo method

Summary The most relevant properties of hypercycles were previously studied mainly from a theoretical point of view. We have developed a Monte Carlo method simulating hypercyclic organization to obtain information about the dynamics of this prebiotic organization. Nucleation, growth, and selective properties have been tested and the results obtained are in good agreement with those of the theoretical predictions. The influence of hypercyclic organization of the error threshold has also been studied. As a consequence of the emergence of a hypercycle, the value of this threshold decreases. The amount of this decrease depends on the population size. Moreover, for some interval of quality factor values, either the hypercycle organization or an error catastrophe can be produced, depending on the initial conditions. The influence of these phenomena on both the dynamic behavior and evolutionary advantages of the hypercycle, as well as their decisive roles on genome size, are discussed.Presented at the FEBS Symposium on Genome Organization and Evolution, held in Crete, Greece, September 1–5, 1986     

Binding of flunitrazepam to differentiating neurons cultured in a chemically defined,hormone-supplemented medium

[³H]Flunitrazepam (FNZ) binding to cortical neurons from fetal rat brain was investigated in vitro. The use of a synthetic medium specific for neurons made it possible to plot a developmental curve of³H-FNZ binding in an almost pure neuronal culture. Detectable specific binding was present in vitro at time 0 (that is, the 16th gestational day). A progressive increase of binding, due to an increment in the number of recognition sites, was observed on the subsequent days. The affinity of the specific binding sites to³H-FNZ was enhanced by the addition of exogenous GABA, whereas the density was not affected.     

Daucus carota cells contain a dihydrofolate reductase: thymidylate synthase bifunctional polypeptide

Dihydrofolate reductase (DHFR) and thymidylate synthase (TS) activities from cell suspension cultures of Daucus carota were shown to copurify on (NH₄)₂SO₄ fractionation, DEAE Sephadex and methotrexate-Sepharose affinity chromatography and to share approximately the same M_r(183 kDa and 185 kDa respectively) as judged by gel filtration on Sephacryl S-200.The copurified protein migrated as a single band on polyacrylamide gel electrophoresis under denaturing conditions.Both activities could be eluted from the same position of the native gel.Moreover, methotrexate-resistant cell lines which overproduce DHFR revealed to have a parallel higher level of TS. It is therefore proposed and discussed that in carrot, similarly to protozoa, TS and DHFR are present on a single bifunctional polypeptide of 58 kDa.     

Effects of lignin on the anaerobic degradation of (ligno) cellulosic wastes by rumen microorganisms

Summary There appeared to be a clear correlation between the lignin content (% of TS) of several waste and natural materials and their degradability by rumen microorganisms. Materials with lignin contents higher than 25% were not degraded within 72 h. The effects of Kraft pine lignin and some lignin monomers on filter paper degradation, methane production and CMCase activity were tested. Testing these compounds in concentrations comparable to natural conditions showed minor effects. At higher concentrations p-coumaric acid strongly inhibited cellulose degradation and methane production in batch cultures. Influence of lignin compounds on degradation is discussed in relation to structural effects and enzyme or growth inhibition.     

Distribution of polyamines and their related catabolic enzyme in etiolated and light-grown leguminosae seedlings

Diamine-oxidase (DAO; EC 1.4.3.6) activity and di-and polyamine levels were estimated along the epicotyl and root of light-grown and etiolated lentil (Lens culinaris Medicus) and pea (Pisum sativum L.) seedlings. The activity of DAO was higher in etiolated epicotyls than in lightgrown ones. In both species there was a positive correlation between DAO activity and the diamine (putrescine and cadaverine) levels along the whole epicotyl and root. Polyamine (spermine and spermidine) distribution seemed to be associated with the meristematic and elongating zone of the epicotyl and root. The physiological function of DAO is discussed in relation to its possible role in providing hydrogen peroxide to peroxidase-dependent reactions occurring in the cell wall.Abbreviations CAD cadaverine - DA diamine - DAO diamine oxidase - PA polyamine - PUT putrescine - SPD spermidine - SPM spermine     

A BASIC microcomputer program to calculate the secondary structure of proteins from their circular dichroism spectrum

A BASIC program (CDPROT) has been developed to calculate thesecondary structure of proteins from their far UV circular dichroismspectrum. This implementation can use different reference spectra,calculated either from model polypeptides or proteins of knowntertiary structure. Apart from obtaining the a-helical, ß-structure,ß-turns or random percentages which would generatethe spectrum of best fit with respect to the experimental measures,CDPROT represents on screen both theoretical and experimentalspectra indicating the root-mean-square error. The provisionof additional reference spectra by the user is also considered,and another program (STOREREF) performs the editing in an adequateformat for CDPROT. Received on March 8, 1988; accepted on June 3, 1988