In situ cardiac performance of Atlantic cod (Gadus morhua) at cold temperatures: long-term acclimation, acute thermal challenge and the role of adrenaline

The resting and maximum in situ cardiac performance of Newfoundland Atlantic cod (Gadus morhua) acclimated to 10, 4 and 0°C were measured at their respective acclimation temperatures, and when acutely exposed to temperature changes: i.e. hearts from 10°C fish cooled to 4°C, and hearts from 4°C fish measured at 10 and 0°C. Intrinsic heart rate (f(H)) decreased from 41 beats min(-1) at 10°C to 33 beats min(-1) at 4°C and 25 beats min(-1) at 0°C. However, this degree of thermal dependency was not reflected in maximal cardiac output (Q(max) values were ~44, ~37 and ~34 ml min(-1) kg(-1) at 10, 4 and 0°C, respectively). Further, cardiac scope showed a slight positive compensation between 4 and 0°C (Q(10)=1.7), and full, if not a slight over compensation between 10 and 4°C (Q(10)=0.9). The maximal performance of hearts exposed to an acute decrease in temperature (i.e. from 10 to 4°C and 4 to 0°C) was comparable to that measured for hearts from 4°C- and 0°C-acclimated fish, respectively. In contrast, 4°C-acclimated hearts significantly out-performed 10°C-acclimated hearts when tested at a common temperature of 10°C (in terms of both Q(max) and power output). Only minimal differences in cardiac function were seen between hearts stimulated with basal (5 nmol l(-1)) versus maximal (200 nmol l(-1)) levels of adrenaline, the effects of which were not temperature dependent. These results: (1) show that maximum performance of the isolated cod heart is not compromised by exposure to cold temperatures; and (2) support data from other studies, which show that, in contrast to salmonids, cod cardiac performance/myocardial contractility is not dependent upon humoral adrenergic stimulation.

eIF4E is an important determinant of adhesion and pseudohyphal growth of the yeast S. cerevisiae

eIF4E, the cytoplasmatic cap-binding protein, is required for efficient cap-dependent translation. We have studied the influence of mutations that alter the activity and/or expression level of eIF4E on haploid and diploid cells in the yeast S. cerevisiae. Temperature-sensitive eIF4E mutants with reduced levels of expression and reduced cap-binding affinity clearly show a loss in haploid adhesion and diploid pseudohyphenation upon starvation for nitrogen. Some of these mutations affect the interaction of the cap-structure of mRNAs with the cap-binding groove of eIF4E. The observed reduction in adhesive and pseudohyphenating properties is less evident for an eIF4E mutant that shows reduced interaction with p20 (an eIF4E-binding protein) or for a p20-knockout mutant. Loss of adhesive and pseudohyphenating properties was not only observed for eIF4E mutants but also for knockout mutants of components of eIF4F such as eIF4B and eIF4G1. We conclude from these experiments that mutations that affect components of the eIF4F-complex loose properties such as adhesion and pseudohyphal differentiation, most likely due to less effective translation of required mRNAs for such processes.

Emergence of Blastoschizomyces capitatus yeast infections, Central Europe

We report 5 cases of disseminated infection caused by Blastoschizomyces capitatus yeast in central Switzerland. The emergence of this yeast in an area in which it is not known to be endemic should alert clinicians caring for immunocompromised patients outside the Mediterranean region to consider infections caused by unfamiliar fungal pathogens.