Reduced oxygen at high altitude limits maximum size

The trend towards large size in marine animals with latitude, and the existence of giant marine species in polar regions have long been recognized, but remained enigmatic until a recent study showed it to be an effect of increased oxygen availability in sea water of a low temperature. The effect was apparent in data from 12 sites worldwide because of variations in water oxygen content controlled by differences in temperature and salinity. Another major physical factor affecting oxygen content in aquatic environments is reduced pressure at high altitude. Suitable data from high-altitude sites are very scarce. However, an exceptionally rich crustacean collection, which remains largely undescribed, was obtained by the British 1937 expedition from Lake Titicaca on the border between Peru and Bolivia in the Andes at an altitude of 3809 m. We show that in Lake Titicaca the maximum length of amphipods is 2-4 times smaller than other low-salinity sites (Caspian Sea and Lake Baikal).     

Purification of antifreeze proteins by adsorption to ice

Antifreeze proteins (AFPs) can protect organisms from freezing injury by adsorbing to ice and inhibiting its growth. We describe here a method where ice, grown on a cold finger, is used to selectively adsorb and purify these ice-binding proteins from a crude mixture. Type III recombinant AFP was enriched approximately 50-fold after one round of partitioning into ice and purified to homogeneity by a second round. This method can also be used to purify non-ice-binding proteins by linkage to AFP domains as demonstrated by the recovery of a 50 kDa maltose-binding protein-AFP fusion from a crude lysate of Escherichia coli.     

Methyl t-butyl ether mineralization in surface-water sediment microcosms under denitrifying conditions

Mineralization of [U-(14)C]methyl t-butyl ether (MTBE) to (14)CO(2) without accumulation of t-butyl alcohol (TBA) was observed in surface-water sediment microcosms under denitrifying conditions. Methanogenic activity and limited transformation of MTBE to TBA were observed in the absence of denitrification. Results indicate that bed sediment microorganisms can effectively degrade MTBE to nontoxic products under denitrifying conditions.     

Higher-accuracy method for measuring minichromosome stability in Saccharomyces cerevisiae

The minichromosome maintenance assay isfrequently used to characterize mutations genetically that affect the initiation of DNA replication or to decipherfunctional components in autonomously replicating sequences. The assay determines minichromosome loss by measuring the percentage of plasmid-containing cells in cultures after a period of growth in nonselective medium. Here we analyze data acquisition errors that contribute to the low accuracy of the routine versions of the assay. We propose modifications that eliminate errors in the acquisition of two variables and significantly improve the accuracy of the assay.     

Circadian rhythms during cycling exercise and finger-tapping task

The aim of this study was to follow the circadian fluctuation of the spontaneous pedal rate and the motor spontaneous tempo (MST) in a sample of highly trained cyclists. Ten subjects performed five test sessions at various times of day. During each test session, subjects were required to perform (i) a finger-tapping task, in order to set the MST and (ii) a submaximal exercise on a cycle ergometer for 15 min at 50% of their W_max. For this exercise, pedal rate was freely chosen. Spontaneous pedal rate and heart rate (HR) were measured continuously.

The results demonstrated a circadian variation for mean oral temperature, HR, and MST. Under submaximal exercise conditions, HR showed no significant time-of-day influence although spontaneous pedal rate changed significantly throughout the day. Circadian rhythm of oral temperature and pedal rate were strongly correlated. Moreover, a significant positive correlation was found between MST and pedal rate. Both parameters may be controlled by a common brain oscillator. MST, rest HR, and pedal rate changes follow the rhythm of internal temperature, which is considered to be the major marker in chronobiology, therefore, if there is a relation between MST and pedal rate, we cannot rule out partial dependence of both parameters on body temperature.     

Effects of a hypocaloric,low-carbohydrate diet on weight loss,blood lipids,blood pressure,glucose tolerance,and body composition in free-living overweight women

The purpose of the current study was to examine the effects of a very low-carbohydrate diet on weight loss and biochemical parameters in overweight women. Twenty women completed an 8-week trial that reduced their daily carbohydrate intake from 232 to 71 g (p < 0.05) and reduced energy by 2,644 kJ/day (8,384 to 5,740 kJ, p < 0.001). The average weight loss was 5.0 kg (p < 0.0001), with a net decrease in body mass index of 1.82 kg/m2, a loss of 3.4% body fat (4 kg, p < 0.0001), and a loss of 1.0 kg lean mass (p < 0.05). There were no significant changes in fasting blood glucose, fasting serum insulin, oral glucose tolerance, free or total insulin-like growth factor-1, or total IGFBP-3. Systolicblood pressure decreased by an average of 9.0 mmHg (1 mmHg = 133.322 Pa) (p < 0.01) and diastolic blood pressure decreased by 7 mmHg (p < 0.05). Total cholesterol decreased 1.2 mM (p < 0.001), all of which was accounted for by a decrease in low-density lipoprotein cholesterol (p < 0.001) with no change in high-density lipoprotein cholesterol (baseline, 1.17 mM; week 8, 1.22 mM). Total triacylglycerol decreased 0.6 mM (p < 0.01), and the ratio of triacylglycerol/HDL also significantly decreased (baseline, 1.40; week 8, 0.87; p < 0.001). Serum beta-hydroxybutyrate concentrations rose significantly by week 2 and declined thereafter but remained significantly higher than baseline values for the duration of the intervention. Therefore, carbohydrate restriction to 70 g or less with concomitant energy restriction, without changes in protein or fat consumption, promotes weight loss, and improvements in body composition, blood pressure, and blood lipids without compromising glucose tolerance in moderately overweight women.     

Rescue of the neural tube defect of loop-tail mice by a BAC clone containing the Ltap gene

The mouse mutant loop-tail (Lp) is an accepted model for the study of neural tube defects (NTDs) in humans. Whereas Lp/+ heterozygotes show a mild tail defect (looped), homozygous Lp/Lp embryos show a very severe form of NTD, with a completely open neural tube from the hindbrain region to the caudal portion of the spinal cord (craniorachischisis). We have recently identified a positional candidate for Lp on chromosome 1, designated as Ltap. Here, we have used an in vivo complementation approach in transgenic mice to attempt to correct the looped-tail phenotype with a bacterial artificial chromosome clone (BAC280A23) that harbors a full-length copy of the Ltap gene. Genotype:phenotype correlations in Lp/+ heterozygotes carrying BAC280A23 show that this clone can rescue the looped-tail phenotype in two independent founder lines (P < 0.05 and P < 0.0001). Importantly, BAC280A23 is also observed to rescue the lethal NTD of Lp/Lp homozygotes, because several viable transgenic Lp/Lp mice could be identified and appeared normal (P < 0.05). Results from these gain-of-function transgenic animals strongly suggest that the positional candidate Ltap present in this BAC is indeed the gene that is defective in loop-tail.     

The theory of DNA separation by capillary electrophoresis

The Human Genome has been sequenced in large part owing to the invention of capillary electrophoresis. Although this technology has matured enough to allow such amazing achievements, the physical mechanisms at play during separation have yet to be completely understood and optimized. Recently, new separation regimes and new physical mechanisms have been investigated. The use of free-flow electrophoresis and new modes of pulsed-field electrophoresis have been suggested, while we have observed a shift towards single nucleotide polymorphism analysis and microchip technologies. A strong theoretical basis remains essential for the efficient development of new methods.     

Protein--protein interaction maps: a lead towards cellular functions

The availability of complete genome sequences now permits the development of tools for functional biology on a proteomic scale. Several experimental approaches or in silico algorithms aim at clustering proteins into networks with biological significance. Among those, the yeast two-hybrid system is the technology of choice to detect protein-protein interactions. Recently, optimized versions were applied at a genomic scale, leading to databases on the web. However, as with any other 'genetic' assay, yeast two-hybrid assays are prone to false positives and false negatives. Here we discuss these various technologies, their general limitations and the potential advances they make possible, especially when in combination with other functional genomics or bioinformatics analyses.     

Circadian fluctuations in the muscular efficiency of athletes: with sleep versus sleep deprivation

The influence of time of day on muscular performance was studied. From part of the results of two different studies (EAS et EPS), the effects of sleep deprivation were appreciated. Seven times over the 24-h period, developed torque and myoelectric activity were estimated during maximal isometric voluntary contractions using an isokinetic dynamometer: elbow flexion for EAS in standardised sleep, and knee extension for EPS in complete sleep deprivation. The results showed nycthemeral changes in torque in both conditions (p < 0.005), with maximal values recorded at the beginning of night. Although during sleep deprivation (EPS) the rhythm followed neurophysiological factors, during EAS, this rhythm was accounted for by the variations in the contractile state of muscle.