Constancy of synaptic ribbon numbers in the retina of the arctic chary,Salvelinus alpinus

Synopsis At high latitudes, such as in Iceland, the daily photoperiod varies from almost continuous darkness in winter to virtually constant light in summer. Previous studies of detailed retinal structure in vertebrates have shown significant daily and annual effects of photoperiod. We sampled arctic charr in Iceland during the summer, including fish that were both light- and dark-adapted, during both day and night. We observed retinomotor responses characteristic of light- and dark-adaptation, but found no difference in the number of synaptic ribbons in the retina. The morpho-physiological changes, appearing as retinomotor responses, are thus not expressed at the synaptic level.     

Carbohydrate ingestion and muscle glycogen depletion during marathon and ultramarathon racing

Two studies were undertaken to characterize the effects of carbohydrate ingestion on fuel/hormone response to exercise and muscle glycogen utilization during prolonged competitive exercise. In study 1, eighteen subjects were divided into three groups, matched for maximum oxygen consumption (VO2max) and blood lactate turnpoint. All subjects underwent a 3-day carbohydrate (CHO) depletion phase, followed by 3 days of CHO loading (500-600 g.day-1). During the race, the groups drank either 2% glucose (G), 8% glucose polymer (GP), or 8% fructose (F). Muscle biopsies were performed before and after the race and venous blood was sampled before and at regular intervals during the race. In study 2, eighteen subjects divided into 2 matched groups ingested either a 4% G or 10% GP solution during a 56 km race. Despite significantly greater CHO ingestion by GP and F in study 1 and by GP in study 2, blood glucose, free fatty acids and insulin concentrations, muscle glycogen utilization and running performance were not different between groups. These studies show (i) that hypoglycaemia is uncommon in athletes competing in races of up to 56 km provided they CHO-load before and ingest a minimum of 10 g CHO.h-1 during competition; (ii) that neither the amount (10 g vs 40 g.h-1) nor the type of carbohydrate (G vs GP vs F) has any effect on the extent of muscle glycogen depletion or running performance in matched subjects racing over distances up to 56 km.     

Oxidation of exogenous carbohydrate during prolonged exercise: the effects of the carbohydrate type and its concentration.

We studied rates of exogenous carbohydrate (CHO) oxidation during 90 min of cycling exercise in trained cyclists exercising at 70% of maximal oxygen consumption (VO2max) when they ingested glucose, sucrose, or glucose polymer solutions at concentrations of 7.5%, 10% or 15%. Drinks were labelled with [U-14C]glucose or sucrose and were ingested at a rate of 100 ml.10 min-1. Rates of oxidation of the ingested CHO were calculated from the specific radio-activity of the labelled CHO, expired 14CO2 and carbon dioxide output (VCO2). Total CHO oxidation, determined from oxygen consumption and VCO2 was not influenced by CHO type or concentration. Gastric emptying (P = 0.01) and the rate of exogenous CHO oxidation (P = 0.028) was greatest for the glucose polymer solutions, and least for glucose. Although gastric emptying (P = 0.006) decreased with increasing CHO concentration, CHO delivery to the intestine and exogenous CHO oxidation increased linearly with increasing CHO concentration. The percentage of the CHO delivered to the intestine that was oxidized ranged from 30.0% for 7.5% CHO to 38.1% for 15% CHO. Our results indicated that the rate of gastric emptying for CHO was not controlled to provide a constant rate of energy delivery as is commonly believed and that factors subsequent to gastric emptying limit the rate of exogenous CHO oxidation from the ingested solution.     

Nuclear-encoded subunits of human cytochrome c oxidase: SstI restriction fragment length polymorphism

A DNA polymorphism of the nuclear-encoded subunit Va of the human cytochrome c oxidase (COX), a mitochondrial respiratory enzyme, is reported. No polymorphism was detected in genes for the subunits IV and Vb of the same enzyme.     

The effect of experimental induced hypocalcaemia on uterine activity in the sow during parturition and post-partum

Uterine activity was measured by monitoring intrauterine pressure changes using ballon-tipped catheters placed in the lumen. An infusion rate of Na(2)EDTA of 35 mg/Kg/h gave a chelation rate equivalent to the rate of calcium mobilisation, and when infused at a level greater than this, resulted in a reduction in plasma calcium concentrations and a concomitant reduction in uterine activity. In three of the four sows infused intrapartum, there was complete cessation of uterine activity; however, plasma calcium concentrations of less than 6 mg 100 ml resulted in a reduction in uterine activity at this stage of parturition. The uterus of the sow post-partum appeared to be more sensitive to the effects of hypocalcaemia with reduced uterine activity when plasma calcium concentrations fell below 8.2 mg 100 ml and complete cessation of activity between 6 and 7 mg 100 ml . Although there was evidence of a delay in the expulsion of piglets in the hypocalcaemic sows, there was no evidence of an increased number of stillborn piglets compared with the two control sows.     

Genetics of social behaviour in charrs (Salvelinus species)

Juvenile brook charr (Salvelinus fontinalis) are territorial and have high levels of agonistic behaviour. Juvenile lake charr (S. namaycush) rarely show any indication of territoriality and have very low levels of agonistic behaviour. The inheritance of behaviour in their reciprocal hybrids was investigated by multivariate stepwise discriminant analysis. Lateral display, charge, chase, and forage composed the first canonical axis (87.2% of total dispersion). Pooled hybrid means were closer to that of brook charr, suggesting either directional dominance or modification of the behaviour of hybrids in response to water flow. The mean values of reciprocal hybrids were skewed towards the maternal parent, suggesting a maternal effect in the phenotypic expression of behaviour in these fish.     

GOLPH3L antagonizes GOLPH3 to determine Golgi morphology

GOLPH3 is a phosphatidylinositol-4-phosphate (PI4P) effector that plays an important role in maintaining Golgi architecture and anterograde trafficking. GOLPH3 does so through its ability to link trans-Golgi membranes to F-actin via its interaction with myosin 18A (MYO18A). GOLPH3 also is known to be an oncogene commonly amplified in human cancers. GOLPH3L is a GOLPH3 paralogue found in all vertebrate genomes, although previously it was largely uncharacterized. Here we demonstrate that although GOLPH3 is ubiquitously expressed in mammalian cells, GOLPH3L is present in only a subset of tissues and cell types, particularly secretory tissues. We show that, like GOLPH3, GOLPH3L binds to PI4P, localizes to the Golgi as a consequence of its PI4P binding, and is required for efficient anterograde trafficking. Surprisingly, however, we find that perturbations of GOLPH3L expression produce effects on Golgi morphology that are opposite to those of GOLPH3 and MYO18A. GOLPH3L differs critically from GOLPH3 in that it is largely unable to bind to MYO18A. Our data demonstrate that despite their similarities, unexpectedly, GOLPH3L antagonizes GOLPH3/MYO18A at the Golgi.     

Application of an optimized marker amplification protocol in immunohistochemistry — a valuable tool for visualizing antigenic sites of low signal strength or sparse distribution

Amplification of immunohistochemical markers received considerable attention during the 1980s and 1990s. The amplification approach was largely abandoned following the development of antigen retrieval and reporter amplification techniques, because the latter were incorporated more easily into high throughput automated procedures in industrial and diagnostic laboratories. There remain, however, a number of instances where marker amplification still has much to offer. Consequently, we examined experimentally the utility of an optimized marker amplification technique in diagnostically relevant tissue where either the original signal strength was low or positive sites were visible, but sparsely distributed. Marker amplification in the former case not only improved the visibility of existing positive sites, but also revealed additional sites that previously were undetectable. In the latter case, positive sites were rendered more intense and therefore more easily seen during low magnification examination of large areas of tissue.     

Survival and behavior of juvenile steelhead trout (Oncorhynchus mykiss) in two estuaries in Oregon, USA

Anadromous salmonids are viewed as a prized commodity and cultural symbol throughout the Pacific coast of North America. Unfortunately, several native salmonid populations are threatened or at risk of extinction. Despite this, little is known about the behavior and survival of these fish as the juveniles transition from freshwater to the ocean. Our primary objectives were to estimate survival of juvenile steelhead migrating between trapping sites and the ocean and evaluate whether survival in the estuary varies temporally (within a year) or spatially (within and between estuaries) within the same distinct population segment. We also evaluated whether flow or fork length were correlated with survival and collected information on variables that have been demonstrated to affect smolt survival in other studies to lend insight regarding differences in survival estimates between basins. We compared run timing, migration rate, survival, condition factor, age composition and time of residence in the estuary for steelhead outmigrants from each basin and measured parasite loads in outmigrating steelhead to evaluate potential differences in parasite density and parasite community between basins. In 2009, we implanted acoustic transmitters in 139 wild steelhead smolts in two small rivers on the Oregon Coast. In general, only 40–50 % of the wild steelhead smolts tagged at upstream smolt traps were detected entering the ocean. The majority of mortality occurred in the lower estuary near the ocean. Wild steelhead smolts typically spent less than 1 day in the estuary in both basins. Using similar data from previous studies in the Nehalem and Alsea basins, we showed that survival appears to be negatively correlated with flow in most releases, and in 2009 fork length was not correlated with survival. Our observations provide baseline information on factors that could influence smolt survival through the estuary as well as smolt to adult survival in these basins, and emphasize the importance of monitoring smolt survival in the estuary.