世居及移居高原青少年最大有氧能力的特征

本文报道海拔３４１７ｍ和４２８０ｍ地区世居藏族和移居汉族青少年运动状态下心肺功能的对比研究。结果显示：３４１７ｍ和４２８０ｍ世居藏族的最大氧耗量、无氧阈值及最大心输出量都明显大于汉族,血氧饱和度（Ｓａｏ２）随运动负荷的增加而降低。海拔３４１７ｍ藏、汉族的△Ｓａｏ２分别为７．４６％和１０．０３％,４２８０ｍ处为８．５７％和１３．７５％,最大心率随海拔升高而下降。研究提示,藏族青少年有较高的最大有氧能力,反映了他们对低氧环境的适应优势。     

Sperm cryopreservation of African catfish, Clarias gariepinus: cryoprotectants, freezing rates and sperm:egg dilution ratio

Methods for cryopreserving spermatozoa and optimizing sperm:egg dilution ratio in African catfish Clarias gariepinus were developed. Five percent to 25% DMSO and methanol were tested as cryoprotectants, by diluting semen in Ginzburg fish ringer and freezing in 1-milliliter cryovials in a programmable freezer. To avoid an excess of spermatozoa per egg, post-thaw semen was diluted 1:20, 1:200 or 1:2,000 before fertilization. Highest hatching rates were obtained by spermatozoa frozen in 10% methanol and post-thaw diluted to 1:200. Then, slow freezing rates (-2, -5 or -10 degrees C/min) to various endpoint temperatures (range -25 to -70 degrees C) before fast freezing in liquid nitrogen (LN2) were evaluated. Hatching rates equal to control (P > 0.05) were obtained by spermatozoa frozen at -5 degrees C/min to -45 to -50 degrees C and at -10 degrees C/min to -55 degrees C. In 3-step freezing programs, at -5 degrees C/min, the effect of holding spermatozoa for 0, 2 or 5 min at -30, -35 or -40 degrees C before fast freezing in LN2 was analyzed. Hatching rates equal to control (P > 0.05) were produced by spermatozoa frozen to, and held at, -35 degrees C for 5 min and at -40 degrees C for 2 or 5 min. Finally, frozen spermatozoa (10% methanol, -5 degrees C/min, 5-min hold at -40 degrees C, LN2, post-thaw diluted to 1:200) were tested in on-farm fertilization conditions. Again, no difference (P > 0.05) in hatching rate was observed between frozen and fresh spermatozoa. Cryopreservation offers utility as a routine method of sperm storage and management for catfish.     

The phylogeny of the ant tribe Formicini (Hymenoptera: Formicidae) with the description of a new genus

Abstract. The holarctic ant tribe Formicini is revised, the new genus Bajcaridris described, and possible phylogenetic relationships are discussed. The subgenus Iberoformica is synonymized with Formica. A synopsis, diagnosis and keys to the genera are provided.     

Effectiveness of a reserve network for the conservation of the endemic marsupial Micoureus travassosi in Atlantic Forest remnants in southeastern Brazil

Habitat loss and fragmentation are serious threats to biodiversity conservation in the Atlantic Forest. A network of protected reserves is essential to the protection of native fauna and flora. However, internal and external factors may threaten the preservation of biota, thus population viability analyses (PVA) are important tools in reserve design and management planning. A PVA was carried out, using the computer package VORTEX, to assess the effectiveness of the reserve network of Rio de Janeiro State in Brazil in retaining viable populations of the endemic marsupial Micoureus travassosi. The PVA takes into account demographic, genetic and environmental stochastic events and catastrophes (fire). Rio de Janeiro state has 31 reserves, and 20 of those were considered to retain viable populations for 100 years, whereas eight were predicted to suffer from genetic decay, two from both genetic decay and demographic stochasticity, and one of them probably has an extinct population. The minimum area of suitable habitat needed to maintain a minimum viable population of M. travassosi is estimated at 3600ha. Sensitivity analysis was run for mortality, sex ratio, percentage of reproductive females, inbreeding depression and probability of catastrophes, and suggests that inbreeding depression is important in small population sizes, whereas the effects of catastrophes were significant only for large populations. Although the model indicates that some populations will suffer from demographic and/or genetic stochasticity, the reserve network of Rio de Janeiro state will likely keep M. travassosi's populations for the next 100 years.     

Effects of oxytocin on semen release response in African catfish (Clarias gariepinus)

In silurid fishes, semen collection is practically impossible, even after hormonal stimulation. Instead, males are killed and testes macerated to obtain sperm. To understand the endocrine control of semen release in catfishes, we investigated the role of smooth muscle contractors in semen release and semen quality of African catfish (Clarias gariepinus). In in vitro experiments, testis slices were incubated with oxytocin (1 and 10 IU), isotocin (2 and 20 ug), vasopressin (0.2 and 2 ug), epinephrine (1 and 10 ug), PGF2alpha (1 and 10 ug), purified Clarias LH (300 ng) and partly purified Clarias pituitary extract (containing 300 ng LH). Only oxytocin increased sperm concentration of the medium (assessed by optical density measurements) compared to control incubations. Oxytocin was then tested in vivo in two groups of fish: normal males, and males that had been treated with 17alpha-methyltestosterone during larval stages to inhibit seminal vesicle development (MT males). Both groups of fish received two doses of carp pituitary suspension (8 and 10 mg/kg, respectively i.m.) with or without subsequent oxytocin treatment (5 IU/kg i.v.; cPS-OT treatment and cPS treatment, respectively). There was no effect of oxytocin on the number of strippable males. Of cPS and cPS-OT treated fish, 87% MT males and 60% normal males were strippable. The stripped semen volume was low in both groups but MT males produced higher (P < 0.001) hatching rates (63.1%) than did normal males (2.1%).     

Sex differences in the rate of fatigue development and recovery

Background

Many musculoskeltal injuries in the workplace have been attributed to the repetitive loading of muscle and soft tissues. It is not disputed that muscular fatigue is a risk factor for musculoskeltal injury, however the disparity between gender with respect to muscular fatigability and rate of recovery is not well understood. Current health and safety guidelines do not account for sex differences in fatiguability and may be predisposing one gender to greater risk. The purpose of this study was to quantify the sex differences in fatigue development and recovery rate of lower and upper body musculature after repeated bouts of sustained isometric contractions.

Methods

Twenty-seven healthy males (n = 12) and females (n = 15) underwent bilateral localized fatigue of either the knee extensors (male: n = 8; female: n = 8), elbow flexors (male: n = 8; female: n = 10), or both muscle groups. The fatigue protocol consisted of ten 30-second sub-maximal isometric contractions. The changes in maximum voluntary contraction (MVC), electrically evoked twitches, and motor unit activation (MUA) were assessed along with the ability to control the sustained contractions (SLP) during the fatigue protocol using a mixed four-factor repeated measures ANOVA (gender × side × muscle × time) design with significance set at p < 0.05.

Results

There was a significant loss of MVC, MUA, and evoked twitch amplitude from pre- to post-fatigue in both the arms and legs. Males had greater relative loss of isometric force, a higher rate of fatigue development, and were less capable of maintaining the fatiguing contractions in the legs when compared to the females.

Conclusion

The nature of the induced fatigue was a combination of central and peripheral fatigue that did not fully recover over a 45-minute period. The results appear to reflect sex differences that are peripheral, and partially support the muscle mass hypothesis for explaining differences in muscular fatigue.

     

Sperm cryopreservation affects postthaw motility, but not embryogenesis or larval growth in the Brazilian fish Brycon insignis (Characiformes)

Sperm cryopreservation is an important method for preserving genetic information and facilitating artificial reproduction. The objective was to investigate whether the cryopreservation process affects postthaw sperm motility, embryogenesis, and larval growth in the fish Brycon insignis. Sperm was diluted in methyl glycol and Beltsville Thawing solution, frozen in a nitrogen vapor vessel (dry shipper) and stored in liquid nitrogen. Half of the samples were evaluated both subjectively (% of motile sperm and motility quality score—arbitrary grading system from 0 [no movement] to 5 [rapidly swimming sperm]) and in a computer-assisted sperm analyzer (CASA; percentage of motile sperm and velocity). The other half was used for fertilization and the evaluation of embryogenesis (cleavage and gastrula stages), hatching rate, percentage of larvae with normal development and larval growth up to 112 days posthatching (dph). Fresh sperm was analyzed subjectively (percentage of motile sperm and motility quality score) and used as the control. In the subjective analysis, sperm motility significantly decreased from 100% motile sperm and quality score of 5 in fresh sperm to 54% motile sperm and quality score of 3 after thawing. Under computer-assisted sperm analyzer evaluation, postthaw sperm had 67% motile sperm, 122 μm/sec of curvilinear velocity, 87 μm/sec of straight-line velocity and 103 μm/sec of average path velocity. There were no significant differences between progenies (pooled data) for the percentage of viable embryos in cleavage (62%) or gastrula stages (24%) or in the hatching rate (24%), percentage of normal hatched larvae (93%), larval body weight (39.8 g), or standard length (12.7 cm) at 112 days posthatching. Based on these findings, cryopreserved sperm can be used as a tool to restore the population of endangered species, such as B. insignis, as well as for aquaculture purposes, without any concern regarding quality of the offspring.