Muscle damage and repair in voluntarily running mice: strain and muscle differences

Summary Soleus, extensor digitorum longus and tibialis anterior muscles of mice voluntarily running in wheels for periods of 5 to 120 days were studied in spaced serial and serial cross-sections. Shortly after the onset of running and during the next 2 weeks, degeneration, necrosis, phagocytosis and regeneration of muscle fibers, satellite cell proliferation and cellular infiltration were found in soleus muscles of mice from all strains investigated (CBA/J, NMRI, C57b, NIH, SWS and Balb/c). Tibialis anterior but not extensor digitorum longus muscles were also damaged. Predominantly high-oxidative fibers were affected (both slow-oxidative and fast oxidative glycolytic in soleus, fast-oxidative glycolytic in tibialis anterior). Denervated soleus muscles that had been passively stretched during running were not damaged. Evidence was found that, during the early period of running, split fibers form by myogenesis within (regeneration) or outside (satellite cell proliferation) necrotic muscle fiber segments. Split fibers persisted in solei of long-term (2 to 3 months) exercised CBA/J but not NMRI mice. In 6 out of 20 solei of CBA/J runners exercised for 2 months or longer, fiber-type grouping was observed in the areas where extensive damage usually occurred in the early periods. The results show that different muscles are damaged and repaired to varying degrees and that marked interstrain and inter-individual differences are present. It appears that acute muscle injury occurring upon onset of voluntary running is a usual event in the adaptation of muscles to altered use.     

Changes in muscle activation,oxygenation, and morphology following a fatiguing repetitive forward reaching task in young adult males and females

We sought to evaluate sex-specific 1) muscle activation patterns, hemodynamics, and swelling responses to short-cycle repetitive fatigue; 2) relationships between muscular responses and perceived fatigability. Asymptomatic participants (N = 26, 13 females) completed a repetitive pointing task until 8/10 on the Borg CR10 scale. Upper trapezius (UT), supraspinatus (SUPRA), and biceps brachii (BIC) muscle activation, activation variability (CV), median power frequency (MdPF) and thickness, and UT oxygenation were recorded. Males had higher BIC CV, UT and SUPRA MdPF, and UT and BIC thickness. Longer time to fatigue-terminal was correlated to greater SUPRA activation increase (ρ = 0.624) and BIC MdPF decrease (ρ = -0.674) in males, while in females it was correlated to greater (ρ = -0.657) and lower (ρ = 0.683) decrease of SUPRA and BIC CV, respectively. Male’s greater increase in SUPRA thickness correlated to greater increase in UT thickness and tissue oxygenation index, and to lower increase of UT deoxyhemoglobin. Females’ greater decrease of SUPRA MdPF correlated to greater decrease of UT MdPF, while greater UT activation increase was related to lower UT thickness increase. Results suggest that despite comparable time to fatigue-terminal, males have greater force-generating capacity and neuromuscular reliance on recruitment and excitation rates, while females have greater reliance on activation variability. Further, there are relationships between hemodynamic and swelling patterns in males, while there are relationships between activation and swelling patterns in females. Although there were no differences in experimental task-induced changes, there are sex-specific relationships between muscular patterns and perceived fatigability, which may help explain sex-specific mechanisms of musculoskeletal disorders.     

Effect of Elevated CO2 on Photosynthesis and Chlorophyll Fluorescence of Rose Plants Grown at High Temperature and High Photosynthetic Photon Flux Density

Gas exchange and chlorophyll (Chl) fluorescence were measured on young mature leaves of rose plants (Rosa hybrida cvs. First Red and Twingo) grown in two near-to-tight greenhouses, one under control ambient CO₂ concentration, AC (355 µmol mol^–1) and one under CO₂ enrichment, EC (700 µmol mol^–1), during four flushes from late June to early November. Supply of water and mineral elements was non-limiting while temperature was allowed to rise freely during daytime. Leaf diffusive conductance was not significantly reduced at EC but net photosynthetic rate increased by more than 100 %. Although the concentration of total non-structural saccharides was substantially higher in the leaves from the greenhouse with EC, _PS2 (quantum efficiency of radiation use) around noon was not significantly reduced at EC indicating that there was no down-regulation of electron transport. Moreover, CO₂ enrichment did not cause any increase in the risk of photo-damage, as estimated by the 1 – q_P parameter. Non-photochemical quenching was even higher in the greenhouse with EC during the two summer flushes, when temperature and photosynthetic photon flux density (PPFD) were the highest. Hence rose photosynthesis benefits strongly from high concentrations of atmospheric CO₂ at both high and moderate temperatures and PPFD.     

Ploidy and strain differences in seed germination of Glycine wightii at different pH levels

Summary Seeds from 27 wild strains (18 tetraploids and 9 diploids) of Glycine weightii were germinated at a pH range of 5 to 8. The differences in germination (%) between all the strains were highly significant but between pH levels they were only nearly significant (P=0.067) with no interaction between pH levels and strains. Mean germination (%) for all tetraploids seems to be slightly higher ( 2%) than that for all diploids, especially at pH's 5, 7 and 8 but this may be due to the significantly longer time ( one day) it took tetraploids to complete germination. The apparent inverse relationship between seed weight and germination (%) was not significant.Mean germination time was highly significant for strains, pH's and their interaction. Increasing mean germination (%) resulted in decreasing mean germination time among strains. Large seeds took less time to germinate especially those from some of the tetraploid strains. This indicates that it is possible to produce a variety with high germination (%), fast germination rate and possibly large seeds. If the marked difference in pH tolerance among strains will prove to be mainly hereditary, then it will be also possible to select for either specific pH tolerance or tolerance at a wide range of pH.     

Sex differences in the response to environmental cues regulating seasonal reproduction in birds

Although it is axiomatic that males and females differ in relation to many aspects of reproduction related to physiology, morphology and behaviour, relatively little is known about possible sex differences in the response to cues from the environment that control the timing of seasonal breeding. This review concerns the environmental regulation of seasonal reproduction in birds and how this process might differ between males and females. From an evolutionary perspective, the sexes can be expected to differ in the cues they use to time reproduction. Female reproductive fitness typically varies more as a function of fecundity selection, while male reproductive fitness varies more as a function sexual selection. Consequently, variation in the precision of the timing of egg laying is likely to have more serious fitness consequences for females than for males, while variation in the timing of recrudescence of the male testes and accompanying territory establishment and courtship are likely to have more serious fitness consequences for males. From the proximate perspective, sex differences in the control of reproduction could be regulated via the response to photoperiod or in the relative importance and action of supplementary factors (such as temperature, food supply, nesting sites and behavioural interactions) that adjust the timing of reproduction so that it is in step with local conditions. For example, there is clear evidence in several temperate zone avian species that females require both supplementary factors and long photoperiods in order for follicles to develop, while males can attain full gonadal size based on photoperiodic stimulation alone. The neuroendocrine basis of these sex differences is not well understood, though there are many candidate mechanisms in the brain as well as throughout the entire hypothalamo-pituitary-gonadal axis that might be important.     

Effects of Rhinoncomimus latipes on the growth and reproduction of Persicaria perfoliata,an invasive plant in North America

Native to Asia, mile-a-minute Persicaria perfoliata, is an invasive weed in North America, and the weevil Rhinoncomimus latipes is a host-specific insect agent which occurs widely in China. We conducted a common garden experiment to compare P. perfoliata plant responses of native and invasive populations to herbivory by the weevils from different origins. We found weevils from Hunan, Hubei and Heilongjiang Provinces had strong, moderate and weak ability to suppress host plant, respectively. Weevils from Hunan and Hubei Provinces had stronger impact on the growth of both native and invasive plant populations than the weevil from Heilongjiang Province. The losses in seed output of invasive plants were also significantly greater than natives in the weevil treatments. Our results suggested that the weevil population from Hunan Province may be the most suitable for the control of mile-a-minute, while the population from Heilongjiang Province may be the least suitable due to climate matching.     

Early behavioral development and temperamental traits in mother- vs peer-reared rhesus monkeys

Behavioral characteristics (“traits”) of 24 mother-reared and 24 nursery/peer-reared rhesus monkey infants were assessed via rating scales from the third through the seventh month of life while housed with their rearing partners, and from months 8–10 after all animals had been placed in novel peer groups. The animals were also tested at 8 months of age on the Bayley Scales of Infant Development adapted for nonhuman primates. During the early period effects noted were primarily developmental. Peer-reared animals were rated as increasingly less cautious and more attentive to the outside environment over time, while mother-reared infants declined in ratings of dependence on their mothers. All animals were rated as increasingly active and excitable, and less fearful, over time. For the period of months 8–10, peer-reared animals showed higher confidence ratings in month 10, and all animals showed a decline in attachment to cagemates. Mother-reared animals showed more hostility to the examiner during Bayley testing, whereas peer-reared animals showed more fear. Sex effects included greater ratings for independence from mothers, greater activity over both the early and later periods, greater excitability, greater attentiveness to the extra-cage environment, less cautiousness, and better performance on one Bayley problem for females.     

Dental microwear in anubis and hybrid baboons (Papio hamadryas, sensu lato) living in Awash National Park, Ethiopia

We describe dental microwear in baboons (Papio hamadryas sensu lato) from the anubis-hamadryas hybrid zone of Awash National Park, Ethiopia, outline its variation with sex and age, and attempt to relate the observed microwear pattern to environment and diet. Casts of the maxillary second molar of 52 adult and subadult individuals of both sexes were examined with a scanning electron microscope at x 500. Digitized micrographs were taken at a consistent location on facet 9, and microwear was recorded with an image analysis software package. Univariate and multivariate statistics were used to investigate the shape, size, and density of microwear features. The overall pattern of microwear exhibits an unusual combination of high feature density, with numerous small pits and relatively wide striations, and a high correlation between width of pits and striations across individuals. We interpret this pattern as predominantly the consequence of abrasion by relatively small-caliber environmental grit when accidentally ingested with tough foods such as dried seeds and fruits, as expected in a terrestrial omnivore living in a dusty habitat. Statistical analysis revealed no significant differences between groups defined by sex, age, or troop membership, a result consistent with qualitative observations of feeding habits in this population, and which lends no support to the hypothesis that the longer jaws of adult males should result in longer striations. A trend towards greater feature density in females, however, might be due to limited sexual dinichism, and merits further investigation.