Sexual size dimorphism and male contest in wild Siamese fighting fish

Larger males of the wild Siamese fighting fish Betta splendens were more successful in male contests. There were no differences in fighting duration among treatments. Comparing agonistic behaviour between large and small males in ±1 and ±2 S.D treatments, larger males attacked, chased and performed total agonistic behaviour more than smaller males. There were no differences between larger and smaller males concerning other agonistic behaviour during fighting. Females presented with two potential mates of different sizes did not prefer larger males.     

A critical evaluation of the use of filipin-permeabilized rat hepatocytes to study functions of the endoplasmic reticulum in situ

We have used transmission (TEM) and scanning electron microscopy (SEM) and leakage of lactate dehydrogenase (LDH; EC 1.1.1.27) to evaluate two published procedures which use filipin to render isolated rat hepatocytes permeable to ionic substrates. Cells treated by the procedure of Jorgenson and Nordlie retained less than 10 per cent of their LDH. TEM revealed severe damage to the internal structure of these cells, which included swelling, disintegration and extensive vesicularization of the endoplasmic reticulum (ER). Hepatocytes treated with filipin by the procedure of Gankema et al. retained 65-75 per cent of their LDH and displayed incomplete but highly variable permeability to Trypan blue. SEM revealed the loss of microvilli, other signs of swelling, and the presence of large lesions in the plasma membrane. TEM revealed signs of cell swelling, but the nuclei and the mitochondria were only moderately altered. The rough ER was not swollen, but significant fragmentation was evident and characteristic stacks of lamellar ER were never seen. We conclude that useful information about the functions of the ER in situ cannot be obtained from studies of filipin-treated cells. Our results indicate that retention of LDH is not a sufficient criterion of preservation of cell morphology and that staining with Trypan blue may significantly underestimate the permeability of cells to small ionic metabolites.     

Environmental factors influencing the occurrence of juvenile fish in the mangroves of Pagbilao,Philippines

128 fish species belonging to 54 families were collected from the mangroves of Pagbilao. Ambassis kopsi (Ambassidae) was the most abundant species.Fourteen environmental factors were correlated to the catch per unit time for some species. The occurrence of A. kopsi was positively correlated to nitrate in the water, carbon in the sediments and litter fall. Out of the 8 species investigated, 6 were positively correlated to litter fall. Three species showed positive correlation to phosphate in the water, two to organic carbon in the sediments, nitrate, silicate and pH, and one to salinity and carotenoids in water. The biomass of the total catch was correlated to carbon in the sediments and litter fall.     

Regulation of blue-green algal buoyancy and bloom formation by light,inorganic nitrogen,C02, and trophic level interactions

In highly eutrophic ponds, buoyancy of the gas-vacuolate blue-green alga Anabaenopsis Elenkinii (Miller) was regulated by complex interactions between chemical and physical parameters, as well as by biological interactions between various trophic levels. Algal buoyancy and surface bloom formation were enhanced markedly by decreased light intensity, and to a lesser extent by decreased CO₂ availability and increased availability of inorganic nitrogen. In the absence of dense populations of large-bodied Cladocera, early season blooms of diatoms and green algae reduced light availability in the ponds thus creating conditions favorable for increased buoyancy and bloom formation by A. Elenkinii. The appearance of blue-green algal blooms could be prevented by a reduced density of planktivorous fish, which allowed development of dense cladoceran populations. The cladocerans limited the growth of precursory blooms of diatoms and green algae, and given the resulting clear-water conditions, buoyancy of A. Elenkinii was reduced, and blue-green algal blooms never appeared.     

Effect of transforming growth factor beta (TGF-β) on ATP citrate lyase in isolated hepatocytes

Summary Transforming growth factor beta (TGF-) activates ATP citrate lyase in freshly isolated rat liver hepatocytes in a time dependent manner. Maximal stimulation of the enzyme occurred with less than thirty minutes of incubation of the cells with TGF-. The half maximal effect on the enzyme determined in hepatocytes incubated with TGF- for 10 min at 37°C was elicited by TGF- concentrations in the 10^–11 – 10^–12 M range. The potential role of TGF- stimulation of ATP citrate lyase activity in new membrane synthesis is discussed.     

Variation in length and age at sexual maturity of Atlantic groundfish: a reply

Synopsis The assertion has been made by Halliday (1987) that trends in size and age at maturity of Atlantic groundfish published by Beacham (1983a, b, c, d, e, f) are artifacts induced by errors in determining the sex of an individual, distinguishing between immature and mature fish, sampling fish outside of the regular spawning season, and by nonrandom sampling of the population. In particular, Halliday asserts that for the Atlantic argentine,Argentina silus analysis, the conclusions of Beacham (1983a) that: (1) median length at sexual maturity declined over time; and (2) males matured at older ages than did females are invalid owing to biases in both sampling and analysis. In fact, if some of the biases indicated by Halliday were significant, then the decline in median length at sexual maturity is enhanced and the conclusions of Beacham (1983a) reinforced. Size and age at sexual maturity are dynamic characters in many vertebrate populations, and the fact that they should change for Atlantic groundfish should not be surprising given variable exploitation patterns in the fisheries since 1960.     

Diel food utilization by woundfin,Plagopterus argentissimus,in Virgin River,Arizona

Synopsis Woundfin, Plagopterus argentissimus, fed predominantly on simuliid larvae during the day, and shifted to the larger Hydropsyche spp. at night. Ephemeropteran larvae were eaten nearly uniformly throughout the 24 hour period. Mean weight of food consumed varied from 20–40 mg per individual (0.7–2.5% body weight) throughout the 24 h period. Our estimated daily ration of about 8% body weight, at temperatures that varied between 15–25°C, is based upon our measure of mean gut contents over a 24h period, combined with intestinal evacuation rates suggested for other cyprinids in the literature. The relatively continuous feeding pattern suggests a foraging strategy that would minimize competition with other species for food during June, a period of minimum annual food abundance in Virgin River.     

Relative cytotoxicity of psychotropic drugs in cultured rat hepatocytes

The relative cytotoxic effects of ten psychotropic drugs were assessed in rat hepatocyte monolayer cultures. Clear concentration-related toxicity was seen in the narrow range of 10^–5M to S × 10^–5M. The four cytotoxicity endpoints chosen were: release of the cytosolic enzyme, lactate dehydrogenase, and impairment of biosynthesis and secretion of proteins, bile acids and glycerolipids. LDH leakage and inhibition of protein secretion into the culture medium proved to be the parameters which allowed the best differentiation between the test compounds. The inhibition of glycerolipid secretion was the most sensitive test in relation to concentration and time of exposure. Based on the effects of these endpoints, the following ranking of relative in vitro toxicity, using equimolar drug concentrations, could be established: clomipramine > imipramine = thioridazine > chlorpromazine > amitriptyline = fluperlapine > haloperidol > promazine > clozapine sulpiride. This ranking order of in vitro cytotoxicity correlated well with the potential of the drugs to impair liver function in man. Only clozapine had to be classified as a false negative. There was, however, no correlation between the cytotoxicity and the intracellular accumulation of the test drugs. Furthermore, the comparison of the data obtained with psychotropics with the data from five other amphiphilic cationic drugs was consistent with the widely accepted concept of a direct toxic interaction of the drugs with cytomembranes. This nonspecific toxicity of the membrane-active drugs was further corroborated by a positive correlation between their potential to induce LDH leakage in hepatocytes and their ability to induce hemolysis in red cells. In conclusion, the results obtained in our study strongly suggest that it is possible to assess the relative cytotoxicity of psychotropic drugs in rat hepatocyte cultures. It is proposed that this in vitro system provides a useful tool to evaluate new drugs at an early stage of their development, and to identify the most promising candidates within a class of structurally related compounds. In addition, it allows information to be obtained on possible mechanisms of cytotoxicity.Abbreviations AIB aminoisobutyric acid - AMT amitriptyline - BSA bovine serum albumin - CLP clomipramine - CLZ clozapine - CPZ chlorpromazine - FLU fluperlapine - HAL haloperidol - HC₅₀ dose causing 50% hemolysis - IMP imipramine - LDH lactate dehydrogenase - PZ promazine - SUL sulpiride - TCA trichloroacetic acid - TRZ thioridazine