Exercise-induced muscle damage: effects of light exercise on damaged muscle.

The effects of performing light eccentric exercise (LB) during the period of recovery from a heavy eccentric exercise bout (HB) were studied. An experimental and a control group, each consisting of nine college age volunteers (seven women, two men) performed two HB--HB1 and HB2--14 days apart, using the elbow flexor and extensor muscles of one arm. The experimental group performed an additional LB on the day following the first HB. HB1 resulted in muscle soreness, muscle weakness, changes in elbow joint flexibility, and large delayed increases in serum creatine kinase (CK) activity. The HB2 produced smaller changes in all parameters, indicating that adaptation to the effects of eccentric exercise had occurred in the muscle. The LB did not alter muscle soreness, strength or elbow flexibility, but did reduce or delay CK activity increase after HB1. The LB had no apparent effect on adaptation to HB2.     

The Ulva connection: marine algae subsidize terrestrial predators in coastal Peru

How can terrestrial animals survive in a desert with scant primary productivity? The Peruvian coastal desert is hyper‐arid, but faces one of the world's most productive marine ecosystems, the Peru–Chile cold current. Given the stark difference in productivity between these adjacent ecosystems, we expected to find strong linkages connecting the terrestrial and marine food web. We investigated how marine resources are incorporated in the diet, and influence the distribution of terrestrial consumers (geckos, scorpions, solifuges and darkling beetles). Stomach contents from geckos, and δ¹³C and δ¹⁵N values of geckos and other terrestrial consumers suggest that marine green algae of the genus Ulva provide energy and nutrients to the terrestrial food web. Isotopic values suggest that amphipods, which feed on stranded Ulva, make marine resources available to terrestrial predators by moving between the intertidal and supratidal zones. The relative contribution of terrestrial and algal carbon sources varied among terrestrial predators, because scorpions assimilated a lower proportion of energy from Ulva than did geckos and solifuges. These δ¹³C patterns reflected differences in the spatial distribution of consumers. Our study supports the idea that in places where ecosystems with contrasting productivity levels are spatially juxtaposed, it is not possible to understand the structure and dynamics of food webs without taking into account the effects of energy and nutrients flowing from adjacent ecosystems. In contrast to other studied systems, especially those in Baja California, our site in Peru receives very little rainfall and the amount of precipitation is not affected by El Niño events. The near absence of rainfall promotes an extreme dependence of terrestrial consumers on marine resources, and causes permanent indirect food‐web effects that are affected by temporal variability in marine productivity, rather than temporal patterns of plant growth.     

Novel technology for the provision of power to implantable physiological devices.

We report the development of a novel technology that enables the wireless transmission of sufficient amounts of power to implantable physiological devices. The system involves a primary unit generating the magnetic field and a secondary pickup unit deriving power from the magnetic field and a power conditioner. The inductively coupled system was able to supply a minimum of 20 mW at all locations and pickup orientations across a rat cage, although much higher power of up to 10 W could be achieved. We hypothesized that it would be possible to use this technology to record a high-fidelity ECG signal in a conscious rat. A device was constructed in which power was utilized to recharge a battery contained within a telemetry device recording ECG signal sampled at 2,000 Hz in conscious rats (200-350 g) living in their home cage. Attributes of the ECG signal (QT, QRS, and PR interval) could be obtained with a high degree of accuracy (<1 ms). ECG and heart rate changes in response to treatment with the beta blocker propranolol and the proarrhythmic alkaloid aconitine were measured. Transmitters were implanted for up to 4 mo, and the characteristic circadian variation in heart rate was recorded. Such technology allows potentially lifetime monitoring without the need for implant refurbishment. The ability to provide suitable power levels to implanted devices without concern to the orientation of the device and without causing heating provides the basis for the development of new devices to record or influence physiological signals in animals or humans over significantly longer time periods than can currently be accommodated.     

Antigenic determinants of two components of proteoglycan complex from bovine cartilage

The immunological properties of a glycoprotein fraction and of proteoglycan subunits obtained from bovine nasal cartilage by nondisruptive methods of isolation have been studied. Using the techniques of hemagglutination and hemagglutination inhibition, we found that the glycoprotein contains most of the species-specific determinants, whereas the proteoglycan subunits contain most of the cross-reacting ones.     

Optimal Sequencing Strategies for Surveying Molecular Genetic Diversity

Two commonly used measures of genetic diversity for intraspecies DNA sequence data are based, respectively, on the number of segregating sites, and on the average number of pairwise nucleotide differences. Expressions are derived for their variance in the presence of intragenic recombination for a panmictic population of fixed size that is at neutral equilibrium at the region sequenced. We show that, in contrast to the slow decrease in variance with increasing sample size, if the recombination rate is nonzero, the asymptotic rate of decrease of variance with increasing sequence length, for fixed sample size, is quite rapid. In particular, it is close to that which would be obtained by sequencing independent chromosome regions. The correlation between measures of diversity from linked regions is also examined. For a given total number of bases sequenced in a particular region, optimal sequencing strategies are derived. These typically involve sequencing relatively few (three to 10) long copies of the region. Under optimal strategies, the variances of the two measures are very similar for most parameter values considered. Results concerning optimal sequencing strategies will be sensitive to gross departures from the underlying assumptions, such as population bottlenecks, selective sweeps, and substantial population substructure.     

Likelihoods and simulation methods for a class of nonneutral population genetics models

Methods for simulating samples and sample statistics, under mutation-selection-drift equilibrium for a class of nonneutral population genetics models, and for evaluating the likelihood surface, in selection and mutation parameters, are developed and applied for observed data. The methods apply to large populations in settings in which selection is weak, in the sense that selection intensities, like mutation rates, are of the order of the inverse of the population size. General diploid selection is allowed, but the approach is currently restricted to models, such as the infinite alleles model and certain K-models, in which the type of a mutant allele does not depend on the type of its progenitor allele. The simulation methods have considerable advantages over available alternatives. No other methods currently seem practicable for approximating likelihood surfaces.     

Mechanism of activation of cyclic GMP-dependent protein kinase from rat liver by multiple modulators

A number of polyanionic compounds, including DNA, RNA and polyglutamate, were shown to exhibit protein kinase stimulatory modulator activity as they were required for cyclic GMP to stimulate the phosphorylation of various cationic substrates by rat liver cyclic GMP-dependent protien kinase. Anionic proteins (casein, phosvitin) were phosphorylated poorly by the enzyme and their phosphorylation was not stimulated by the stimulatory modulators. Studies of the mechanism of action suggest that the modulators interact directly with the substrates to form a complex which is a better substrate than free histone. The observed effect of modulator is complex as it depends on the ratio of modulator to histone and the resultant state of the complex formed (better or poorer substrate than free histone). The observed effect is also dependent on the properties of the histone substrate as Michaelis-Menten kinetics are not observed in the phosphorylation of arginine-rich histone in the absence or presence of cyclic GMP.     

Ecological zones rather than molecular forms predict genetic differentiation in the malaria vector Anopheles gambiae s.s. in Ghana

The malaria mosquito Anopheles gambiae s.s. is rapidly becoming a model for studies on the evolution of reproductive isolation. Debate has centered on the taxonomic status of two forms (denoted M and S) within the nominal taxon identified by point mutations in the X-linked rDNA region. Evidence is accumulating that there are significant barriers to gene flow between these forms, but that the barriers are not complete throughout the entire range of their distribution. We sampled populations from across Ghana and southern Burkina Faso, West Africa, from areas where the molecular forms occurred in both sympatry and allopatry. Neither Bayesian clustering methods nor F(ST)-based analysis of microsatellite data found differentiation between the M and S molecular forms, but revealed strong differentiation among different ecological zones, irrespective of M/S status and with no detectable effect of geographical distance. Although no M/S hybrids were found in the samples, admixture analysis detected evidence of contemporary interform gene flow, arguably most pronounced in southern Ghana where forms occur sympatrically. Thus, in the sampled area of West Africa, lack of differentiation between M and S forms likely reflects substantial introgression, and ecological barriers appear to be of greater importance in restricting gene flow.