Reproductive activity and physiological status of the calanoid copepods Calanus helgolandicus and Calanoides carinatus under food-limiting conditions

The reproductive activity and the physiological state of the calanoid copepods Calanus helgolandicus and Calanoides carinatus were investigated off the coast of NW Spain during autumn to evaluate the effect of short food resources on both populations. Phytoplankton biomass was low, and neither phytoplankton size distribution nor composition was suitable to support high reproductive rates. Accordingly, egg production rates (EPR) were much lower than maximum rates for both species, pointing to food limitation. The reproductive index (RI), which represents the proportion of females with mature gonads, was < 50% at each of the three zones into which the sampling area was divided (coast, shelf and ocean). Potential recruitment rates were very low except at some nearshore stations, where the highest concentrations of chlorophyll-a (Chl-a), diatoms, dinoflagellates and large cells were found. EPR of C. helgolandicus and C. carinatus were correlated with phytoplankton biomass and unaffected by temperature. Phytoplankton carbon ingestion explained ca. 50% of the variability in EPR for both species. At most of the stations, herbivory was insufficient to cover the carbon requirements for reproduction and respiration, so females probably fed on heterotrophic prey to meet their demands. However, given the low fecundity observed, this omnivorous diet did not seem to be optimum for reproduction, and a severe food limitation is thus suggested. Furthermore, the high C/N values measured point to a notable lipid storage, but given the low EPR found, lipid reserves were probably invested into female maintenance rather than into gonad maturation. C. helgolandicus and C. carinatus populations did not mirror phytoplankton biomass distribution, but they correlated well when considering only copepodites V (CV). The CV could be preparing for the overwintering, storing lipid reserves to ensure a successful diapause, and they could also be advected by the poleward current detected during the study. Females showed a diel feeding rhythm, with highest ingestion rates during night. From our results, it follows that C. helgolandicus and C. carinatus females did not perform diel vertical migrations. We suggest that this behaviour is likely due to the food-limiting conditions, which make it more advantageous to remain at the surface during daytime.     

Determination of deuterium-labeled tryptophan in proteins by means of high-performance liquid chromatography and thermospray mass spectrometry

In order to develop direct methods for determining the extent of metabolic incorporation of isotopically labeled amino acids into a protein, the determination of deuterated tryptophan in [2H5]tryptophan-bacteriorhodopsin was investigated. The isotopically modified protein was subjected to alkaline hydrolysis. After phenyl isothiocyanate derivatization of the hydrolysate, the mixture was separated by reversed-phase liquid chromatography. Field desorption mass spectrometry and thermospray mass spectrometry were investigated for their ability to determine the ratio between [2H5]tryptophan and total tryptophan in the collected fractions. In order to check the procedure a set of known tryptophan/[2H5]tryptophan mixtures were passed through the same derivatization, HPLC separation, and lyophilization procedure as used for the biological samples.     

Studies on ulcerative dermal necrosis of salmonids

Fourteen fresh run salmon Satmo salar L. with early extant lesions of ulcerative dermal necrosis (UDN) were kept in separate tanks and treated with zinc free malachite green. Ten of the fish were held at 10° C and 4 at 2° C. The treatment precluded infection with Saprolegnia fungus and allowed natural resolution of the lesions. There was a marked difference in rate of healing between warm and cold water conditions.
Histological examination of healing lesions at different stages showed that there was a primary invasion of cuboidal epithelium over the collagen scar followed by a phase of disorganized proliferation which eventually organized itself into normal epithelium. Melanocytes were very obvious in the dermis of healing lesions.     

cDNA sequence and predicted primary structure of the gamma subunit from the ATP synthase from Chlamydomonas reinhardtii

The 1701-base nucleotide sequence (not including the poly(A) tail) of a cDNA for the gamma subunit of the ATP synthase from Chlamydomonas reinhardtii was determined. A start translation sequence, 23 bases in from the 5' end, initiates an 1074-base-long open reading frame. The sequence of the first 21 amino acids at the amino-terminal end of the mature gamma subunit from C. reinhardtii was determined and compared to the deduced amino acid sequence of the open reading frame. From this it was determined that the mature protein contains 323 amino acids, with the first 35 amino acids probably being part of the transit peptide. The length of the mature protein is the same as that for the mature gamma subunit from spinach, for which only a few of the amino acids of the transit peptide are known. The similarity of the two mature proteins at the nucleotide level is 56% while at the amino acid level it is 77%. In addition, the 3 cysteines, which in spinach are involved in the energy-linked catalytic functions of the ATP synthase, are conserved in the predicted amino acid sequence for the gamma subunit from C. reinhardtii. In contrast, the mature C. reinhardtii gamma subunit contains 3 additional cysteine residues not found in the spinach gamma subunit.     

Fibronectin initiates fibrin production by rabbit corneal endothelial cells in vitro

Confluent rabbit corneal endothelial cells incubated in the absence of serum do not produce fibrinogen. When exogenous fibronectin is added to these cultures, fibrinogen production is observed. Fibronectin concentrations stimulate fibrinogen synthesis by endothelial cells in a dose-response fashion. This direct interaction of fibronectin and fibrinogen may be important in both wound healing processes and pathological states.     

Cl- transport in apical plasma membrane vesicles isolated from bovine tracheal epithelium

Gradually altered synthetic entities were employed as molecular probes, and arachidonic acid, ADP, human alpha-thrombin and the Ca2+ ionophore A23187 as aggregation-inducing agents, in a comprehensive study on the response profile of human blood platelets with an emphasis on the effects of exogenous and increased intracellular Ca2+. Corroborating further previous conclusions, some representative carbamoylpiperidine derivatives, at concentrations effecting substantial inhibition of ADP-induced aggregation, failed to retain that effect when 5.0 mM Ca2+ was introduced into the otherwise identical test medium; reference compounds chlorpromazine and propranolol registered corresponding inhibitory patterns. At increased concentrations the compounds' inhibitory potency was regenerated even in the presence of 5 mM Ca2+. In fact, in sufficiently high concentrations, the compounds were even capable of inhibiting aggregation elicited by 15 microM of the ionophore A23187; so did chlorpromazine and propranolol. Another set of congeners revealed the striking sensitivity of ionophore A23187-induced human blood platelet aggregation to the surface active potencies of inhibitor molecules. The loss in inhibitory potency was directly related to the lesser hydrophobic character of the molecule.     

Three phenotypes of glucosephosphate isomerase in sheep: improved staining recipe

Contrary to results published recently, we observe three, rather than two, phenotypes for the enzyme glucosephosphate isomerase (EC 5.3.1.9) from sheep. The phenotypic electrophoretic patterns conform to the patterns observed for this dimeric enzyme in other species. Genotype frequencies in a flock of Southdowns do not deviate significantly from those predicted under the assumption of the Hardy-Weinberg equilibrium. A remarkable observation is that the electrophoretically distinct phenotypes of GPI are largely or entirely obliterated by the addition of 1-10 mmol/l MgCl2 to the electrophoretic buffers. Modification of the usual staining recipe for GPI result in greater resolution and shorter staining times.