Ultrastructural muscle damage in young vs. older men after high-volume, heavy-resistance strength training.

This study assessed ultrastructural muscle damage in young (20-30 yr old) vs. older (65-75 yr old) men after heavy-resistance strength training (HRST). Seven young and eight older subjects completed 9 wk of unilateral leg extension HRST. Five sets of 5-20 repetitions were performed 3 days/wk with variable resistance designed to subject the muscle to near-maximal loads during every repetition. Biopsies were taken from the vastus lateralis of both legs, and muscle damage was quantified via electron microscopy. Training resulted in a 27% strength increase in both groups (P < 0.05). In biopsies before training in the trained leg and in all biopsies from untrained leg, 0-3% of muscle fibers exhibited muscle damage in both groups (P = not significant). After HRST, 7 and 6% of fibers in the trained leg exhibited damage in the young and older men, respectively (P < 0.05, no significant group differences). Myofibrillar damage was primarily focal, confined to one to two sarcomeres. Young and older men appear to exhibit similar levels of muscle damage at baseline and after chronic HRST.     

A Practical Approach to Evaluation of the Germicidal Efficiency of a General Purpose Military Disinfectant

The bactericidal activity of a general purpose disinfectant consisting of 25% sodium-o-phenylphenolate and 75% sodium-4- and 6-chloro-2-phenylphenolate was evaluated by a simulated in-use, surface-square dilution method. Common floor (asphalt, rubber, and unglazed tiles) and wall (stainless steel tile, ceramic tile, and painted wood) surfaces of various porosities and compositions were selected to simulate actual-use conditions.

The method used consisted of inoculating the surfaces of 1-in. square sections of floor and wall covering with a test organism, air-drying the inoculated surface, applying the disinfectant, allowing it to act for 10 min, and recovering the survivors by plating. Confirmatory results of the standard phenol coefficient and use-dilution tests indicated 700 ppm of the disinfectant to be a safe use concentration. The in-use surface-square dilution studies have shown that this is a more than adequate safe concentration for stainless steel, both glazed and unglazed ceramic tile, and nonwaxed surface of asphalt tile. However, concentrations ranging between 2,500 and 6,000 ppm for plastic-fortified rubber tile, 1,500 and 2,000 ppm for waxed asphalt tile, and 2,000 ppm for painted wood were required to achieve 99.9% reduction of either Salmonella choleraesuis or Salmonella schottmuelleri. These results indicate that a disinfectant concentration derived from the Association of Official Agricultural Chemists use-dilution test cannot always be relied upon to provide a dependable index to actual safe use-dilution when a disinfectant is supplied to certain wall or floor surfaces.

     

Microdistribution of Faunal Assemblages at Deep-Sea Hydrothermal Vents in the Southern Ocean

Chemosynthetic primary production by microbes supports abundant faunal assemblages at deep-sea hydrothermal vents, with zonation of invertebrate species typically occurring along physico-chemical gradients. Recently discovered vent fields on the East Scotia Ridge (ESR) in the Southern Ocean represent a new province of vent biogeography, but the spatial dynamics of their distinct fauna have yet to be elucidated. This study determines patterns of faunal zonation, species associations, and relationships between faunal microdistribution and hydrothermal activity in a vent field at a depth of 2,400 m on the ESR. Remotely operated vehicle (ROV) dives obtained high-definition imagery of three chimney structures with varying levels of hydrothermal activity, and a mosaic image of >250 m² of seafloor co-registered with temperature measurements. Analysis of faunal microdistribution within the mosaiced seafloor reveals a consistent pattern of faunal zonation with increasing distance from vent sources and peak temperatures. Assemblages closest to vent sources are visibly dominated by a new species of anomuran crab, Kiwa n. sp. (abundance >700 individuals m⁻²), followed by a peltospiroid gastropod (>1,500 individuals m⁻²), eolepadid barnacle (>1,500 individuals m⁻²), and carnivorous actinostolid anemone (>30 individuals m⁻²). Peripheral fauna are not dominated by a single taxon, but include predatory and scavenger taxa such as stichasterid seastars, pycnogonids and octopus. Variation in faunal microdistribution on chimneys with differing levels of activity suggests a possible successional sequence for vent fauna in this new biogeographic province. An increase in δ³⁴S values of primary consumers with distance from vent sources, and variation in their δ¹³C values also indicate possible zonation of nutritional modes of the vent fauna. By using ROV videography to obtain a high-resolution representation of a vent environment over a greater extent than previous studies, these results provide a baseline for determining temporal change and investigations of processes structuring faunal assemblages at Southern Ocean vents.     

Genetic relatedness to sisters' children has been underestimated

Males of many species help in the care and provisioning of offspring, and these investments often correlate with genetic relatedness. For example, many human males invest in the children of sisters, and this is especially so where men are less likely to share genes with children of wives. Although this makes qualitative sense, it has been difficult to support quantitatively. The prevailing model predicts investment in children of sisters only when paternity confidence falls below 0.268. This value is often seen as too low to be credible; so investment in sisters'' children represents an unsolved problem. I show here that the prevailing model rests on a series of restrictive assumptions that underestimate relatedness to sisters'' children. For this reason, it understates the fitness payoff to men who invest in these children. This effect can be substantial, especially in societies with low confidence in paternity. But this effect cannot be estimated solely from confidence in paternity. One must also estimate the probability that two siblings share the same father.     

Behavioral motifs and neural pathways coordinating O2 responses and aggregation in C. elegans

BACKGROUND: Simple stimuli can evoke complex behavioral responses coordinated by multiple neural circuits. O(2) is an important environmental variable for most animals. The nematode C. elegans avoids high O(2), and O(2) levels regulate its foraging and aggregation. RESULTS: Here, we dissect aggregation and responses to O(2) gradients into behavioral motifs and show how O(2) responses can promote aggregation. To remain in a group, C. elegans continually modify their movement. Animals whose heads emerge from a group will reverse or turn, thereby returning to the group. Re-entry inhibits further reversal, aiding retention in the group. If an animal's tail exits a group during a reversal, it switches to forward movement, returning to the group. Aggregating C. elegans locally deplete O(2). The rise in O(2) levels experienced by animals leaving a group induces both reversal and turning. Conversely, the fall in O(2) encountered when entering a clump suppresses reversal, turning, and high locomotory activity. The soluble guanylate cyclases GCY-35 and GCY-36, which are expressed in head and tail neurons, promote reversal and turning when O(2) rises. Avoidance of high O(2) is also promoted by the TRP-related channel subunits OCR-2 and OSM-9, and the transmembrane protein ODR-4, acting in the nociceptive neurons ASH and ADL. Both O(2) responsiveness and aggregation can be modified by starvation, but this is regulated by natural variation in the npr-1 neuropeptide receptor. CONCLUSIONS: Our work provides insights into how a complex behavior emerges from simpler behavioral motifs coordinated by a distributed circuit.     

Atmospheric CO2 concentration, N availability, and water status affect patterns of ergastic substance deposition in longleaf pine (Pinus palustris Mill.) foliage

 Leaf chemistry alterations due to increasing atmospheric CO₂ will reflect plant physiological changes and impact ecosystem function. Longleaf pine was grown for 20 months at two levels of atmospheric CO₂ (720 and 365 μmol mol^–1), two levels of soil N (4 g m^–2 year^–1 and 40 g m^–2 year^–1), and two soil moisture levels (– 0.5 and – 1.5 MPa) in open top chambers. After 20 months of exposure, needles were collected and ergastic substances including starch grains and polyphenols were assessed using light microscopy, and calcium oxalate crystals were assessed using light microscopy, scanning electron microscopy, and transmission electron microscopy. Polyphenol content was also determined using the Folin-Denis assay and condensed tannins were estimated by precipitation with protein. Evaluation of phenolic content histochemically was compared to results obtained using the Folin-Denis assay. Total leaf polyphenol and condensed tannin content were increased by main effects of elevated CO₂, low soil N and well-watered conditions. Elevated CO₂ and low soil N decreased crystal deposition within needle phloem. Elevated CO₂ had no effect on the percentage of cells within the mesophyll, endodermis, or transfusion tissue which contained visible starch inclusions. With respect to starch accumulation in response to N stress, mesophyll > endodermis > transfusion tissue. The opposite was true in the case of starch accumulation in response to main effects of water stress: mesophyll < endodermis < transfusion tissue. These results indicate that N and water conditions significantly affect deposition of leaf ergastic substances in longleaf pine, and that normal variability in leaf tissue quality resulting from gradients in soil resources will be magnified under conditions of elevated CO₂. Received: 5 November 1996 / Accepted: 7 March 1997     

Linking intra‐specific trait variation and plant function: seed size mediates performance tradeoffs within species

Substantial intra‐specific trait variation exists within plant communities, and in theory this variation could influence community dynamics. Although recent research has focused on intra‐specific variation in traits themselves, it is the influence of this variation on plant performance that makes intra‐specific trait variation relevant to ecological dynamics within or among species. Understanding the links between trait and performance variation, and the role of traits in mediating relationships among multiple components of performance, is critical for assessing the importance of intra‐specific trait variation for community dynamics. Seed size is thought to affect aspects of plant performance including fecundity, seedling growth, dispersal and tolerance of natural enemies. For two tropical tree species, we assessed how seed size was related to performance variation within each species and determined whether intra‐specific trait variation mediates intra‐specific performance tradeoffs. We used field seed rain collection to characterize size‐dependent outcomes of dispersal, sowed seeds of known size in soil collected near or far from conspecifics to characterize susceptibility to soil pathogens, and monitored growth of seedlings from seeds of known size. We found that intra‐specific seed size variation caused intra‐specific performance variation. The degree of trait‐based performance variation was consistently smaller than the degree of trait variation, and seed size influenced different components of performance for each species. One species exhibited a tradeoff in which small seeds had a fecundity advantage (more seedlings per unit reproductive mass) but produced smaller seedlings, whereas the other species exhibited a tradeoff in which small seeds dispersed to areas of low conspecific density but were less tolerant of density‐responsive natural enemies. Our results indicate that a single trait can influence multiple components of performance and can mediate different tradeoffs in co‐occurring species. Complex and heterogeneous effects of a single trait in multidimensional niche space may favour inter‐specific niche differentiation and coexistence.