Isometric strength and occupational muscle disorders

In two longitudinal studies, initial muscle strength and endurance of the shoulder-forearm muscles were related to deterioration of shoulder-neck-arm disorders after one year. Group I (n = 32) worked in the automobile industry assembling car motors. Their work was performed when standing and walking, and implied varied postures and exertion of external forces. Group II (n = 96) worked in the electronics industry assembling printed circuit boards. They worked sitting down and were exposed mainly to postural static loads. Muscle strength was negatively related to deterioration in group I but no such relationship was found in group II. The mechanism of occupational muscular injury is discussed, and it is suggested that mechanical overstress of the musculoskeletal system causes injury in occupations where external forces are exerted. The mechanism of injury in static, postural loads remains to be explained.     

Effects of Benzo(a)pyrene on Seabass (Dicentrarchus labrax L.): Biomarkers,Growth and Behavior

The main purpose of this study was to investigate the effects of benzo(a)pyrene (BaP) on seabass (Dicentrarchus labrax) juveniles using parameters at different levels of biological organization. Liver antioxidant status, BaP biotransformation and accumulation, growth, and behavior were determined in juveniles after 28 d exposure to BaP (1–16 μ g/l). Liver ethoxyresorufin O-deethylase increased in seabass exposed to 1–8 μ g/l of BaP. Liver glutathione S-transferases and catalase activities were significantly increased at 4 and 8 μ g/l, but a slight decrease was observed at the highest concentrations tested. Bile BaP metabolites were significantly different from the control group at 1 and 16 μ g/l BaP. Liver BaP metabolites and lipid peroxidation significantly increased at 8 and 16 μ g/l BaP. These results suggest that BaP metabolites' accumulation induces oxidative damage in seabass liver. Body weight and length increase were significantly reduced in fish exposed to BaP, with LOECs of 16 and 4 μ g/l, respectively. Food intake and swimming velocity were significantly decreased after exposure to BaP, with LOEC values of 16 and 8 μ g/l, respectively. Results suggest that at concentrations of BaP equal or higher than 8 μ g/l, the detoxification capacity decreases, an accumulation of liver BaP metabolites occurs causing lipid peroxidation, affecting growth and swimming capability of fish.     

CLUSTER ANALYSIS OF GROUP TYPES IN SOUTHERN RIGHT WHALE (EUBALAENA AUSTRALIS)

Groups of Eubalaena australis in the Gulf of San Jose, Argentina were characterized and classified. A one-zero sampling method was used for collecting data. A distance matrix was calculated with the 124 groups recorded and 10 characters including composition, size, activities, belly-up and tail-up positions, flipper and tail slaps, and breaching. Cluster analysis separated groups into 12 types. Six low-interaction group types were differentiated primarily by their composition, and extent of swimming and resting behaviors. Six interaction group types were characterized by the presence of whales in the belly-up position, by group size, by the absence of females with calves, and by sexual activity. Some interpretations of the possible functional meaning of the observed group types are discussed.     

Is it advantageous for Atlantic salmon to be triploid at lower temperatures?

Marine organisms living at low temperatures tend to have larger genomes and larger cells which suggest that these traits can be beneficial in colder environments. In fish, triploidy (three complete sets of chromosomes) can be induced experimentally following fertilization, which provides a model system to investigate the hypothesis that larger cells and genomes offers a physiological advantage at low temperatures. We tested this hypothesis by measuring metabolic rates and swimming performance of diploid and triploid Atlantic salmon (Salmo salar) post smolts acclimated to 3 or 10.5 °C. At 10.5 °C, triploids had significantly lower maximum metabolic rates which resulted in a lower aerobic scope compared to diploids. In addition, triploids initiated ram ventilation at lower swimming speeds, providing further evidence of a reduced capacity to meet oxygen demands during strenuous activity at 10.5 °C. However, at 3 °C, metabolic rates and critical swimming speeds were similar between both ploidies, and as expected substantially lower than at 10.5 °C. Therefore, triploidy in colder environments did not provide any advantage over diploidy in terms of metabolic rate traits or swimming performance in Atlantic salmon. We therefore conclude that traits, other than aerobic scope and swimming performance, contribute to the trend for increased cell and genome size in marine ectotherms living in cold environments.