Fiber type composition and capillary density in relation to submaximal number of repetitions in resistance exercise

The purpose of this study was to investigate the relationship between skeletal muscle fiber type composition and the maximum number of repetitions performed during submaximal resistance exercise. Twelve young men performed a maximum repetitions test at 85% of 1 repetition maximum (1RM) in the leg press, which was repeated after 1 week. Seven days after the second 85% 1RM test, they performed a maximum repetitions test at 70% of 1RM in the leg press. This test, at 70% 1RM, was repeated 7 days later. One week before the initiation of the testing sessions, a biopsy sample was obtained from the vastus lateralis muscle and analyzed for fiber type distribution, fiber cross-sectional area, and capillary density (capillaries x mm(2)). A low and nonsignificant relationship was found between the fiber type distribution or percent fiber type area and the number of repetitions performed at either 70% or 85% 1RM. Moreover, the number of repetitions performed at 70% or 85% of 1RM was not related significantly with 1RM strength. In contrast, the number of repetitions performed at 70% 1RM was significantly correlated with the number of capillaries per mm(2) of muscle cross-sectional area (r = 0.70; p = 0.01). These results suggest that fiber type composition is not the major biological variable regulating the number of repetitions performed in submaximal resistance exercise. Rather, it seems that submaximal strength performance depends on muscle capillary density, which is linked with the endurance capacity of the muscle tissue.     

Aggression and composition of conflicting pairs in Green monkeys

The aggressive behaviour of Green monkeys (Chlorocebus aethiops) maintained in corrals of Adler Primate Center was studied. The influence of the composition conflicting pairs, the quality of their relationships as well as the relatedness and hierarchic relations between the antagonists on the intensity and structure of aggressive relationships was investigated. It was found that the frequency of contact forms of aggression was not dependent on the composition of conflicting pairs of animals. At the same time, the frequency of non-contact forms of aggression was influenced by such parameters as the membership of antagonists in the same or different gender categories, belonging to one or different matrilines, as well as the quality of relationships and the rank of antagonists.     

Home-range use, activity, and density of caracal in relation to prey density

Two male and three female caracal Felis caracal were radio-tracked over a 1-year period in arid shrub on the west coast of South Africa, by day and night over at least 130 days for each caracal, and uninterrupted for up to 120 h at a time. These results, on short-term use of space, were related to concurrent availability of prey. The use by caracal of specific plant communities showed a significant positive correlation to prey biomass of rodents. Males had much larger home-ranges (26.9±0.75 km²) than females (7.39±1.68 km²). Male home-ranges overlapped completely with those of females, whereas female ranges overlapped between 0 and 19%. Caracal were active by night and day; onset of activity was affected more by ambient temperature (T_A) than photoperiod. Caracal were active significantly longer on nights colder than 20°C. Females ceased activity at T_A > 20°C, males at T_A > 22°C. Males foraged faster than females (667 vs. 312 m h⁻¹) and moved more than twice the distance of females during an active period. Calculated density of caracal was between 0.23 and 0.47 km⁻².     

Thermogenic side effects to migratory predisposition in shorebirds

In the calidrine sandpiper red knot (Calidris canutus), the weeks preceding takeoff for long-distance migration are characterized by a rapid increase in body mass, largely made up of fat but also including a significant proportion of lean tissue. Before takeoff, the pectoral muscles are known to hypertrophy in preparation for endurance flight without any specific training. Because birds facing cold environments counterbalance heat loss through shivering thermogenesis, and since pectoral muscles represent a large proportion of avian body mass, we asked the question whether muscle hypertrophy in preparation for long-distance endurance flight would induce improvements in thermogenic capacity. We acclimated red knots to different controlled thermal environments: 26 degrees C, 5 degrees C, and variable conditions tracking outdoor temperatures. We then studied within-individual variations in body mass, pectoral muscle size (measured by ultrasound), and metabolic parameters [basal metabolic rate (BMR) and summit metabolic rate (M(sum))] throughout a 3-mo period enclosing the migratory gain and loss of mass. The gain in body mass during the fattening period was associated with increases in pectoral muscle thickness and thermogenic capacity independent of thermal acclimation. Regardless of their thermal treatment, birds showing the largest increases in body mass also exhibited the largest increases in M(sum). We conclude that migratory fattening is accompanied by thermoregulatory side effects. The gain of body mass and muscle hypertrophy improve thermogenic capacity independent of thermal acclimation in this species. Whether this represents an ecological advantage depends on the ambient temperature at the time of fattening.     

Dry weight and chemical composition (CHN) in relation to population density of cultivatedTisbe holothuriae (Copepoda,Harpacticoida)

The harpacticoid copepodTisbe holothuriae was cultivated at different densities in a running-water system. Dry weight and chemical composition (CHN) of both females and egg-sacs have been determined. Dry weight decreased significantly with increasing density from 3,48 to 1.94μg in egg-sacs, and from 10.80 to 6.58μg in females. Increasing density in both egg-sacs and females results in decrease of carbon, nitrogen and hydrogen contents, expressed as a percentage of dry weight of egg-sacs and females, respectively. Carbon decreases from 52.56 to 50.57% (egg-sacs) and 45.80 to 39.95% (⧫), nitrogen from 12.63 to 11.94% and 10.72 to 9.73% and hydrogen from 9.08 to 7.78% and 7.47 to 6.17%. The dry weight and elemental compositions of the egg-sacs varied in accordance with that of the females, however, a higher percentage of elemental content was observed in egg-sacs. The energy equivalents were calculated from the carbon content. This indicates that more energy was transferred from the maternal body into egg-sacs. The ratio of carbon to nitrogen did not show any marked variations; no clear relation appeared between C:N and density, indicating a relatively constant chemical composition in both females and egg-sacs.     

Volume to density relation in adult human bone tissue

Uniformity of tissue mineralisation is a strongly debated issue, due to its relation with bone mechanical behaviour. Bone mineral density (BMD) is measured in the clinical practice and is applied in computational application to derive material proprieties of bone tissue. However, BMD cannot identify if the variation in bone density is related to a modification of tissue mineral density (TMD), a change in bone volume or a combination of the two. This study was aimed to investigate whether TMD can be assumed as a constant in adult human bone (trabecular and cortical).A total number of 115 cylindrical bone specimens were collected. An inter-site analysis (96 specimens, 2 donors) was performed on cortical and trabecular specimens extracted from different anatomical sites. An intra-site study (19 specimens, 19 donors) was performed on specimens extracted from femoral heads. Bone volume fraction (BV/TV) was computed by means of a micro-computed tomography. Furthermore, ash density (ρ_ash) was measured. TMD was computed as the ratio between ρ_ash and BV/TV.It was found that the TMD of trabecular (1.24±0.16 g/cm³) and cortical (1.19±0.06 g/cm³) bone were not statistically different (p=0.31). Furthermore, the linear regression between ρ_ash and BV/TV was statistically significant (r²=0.99, p<0.001). Intra- and inter-site analyses demonstrated that the mineral distribution was independent of the extraction site.The present study suggests that TMD can be assumed reasonably constant in non-pathological adult bone tissue. Consequently, it is suggested that TMD can be managed as a constant in computational models, varying only BV in relation to clinical densitometric analysis.     

Modelling hand skin temperature in relation to body composition

Skin temperature is a challenging parameter to predict due to the complex interaction of physical and physiological variations. Previous studies concerning the correlation of regional physiological characteristics and body composition showed that obese people have higher hand skin temperature compared to the normal weight people. To predict hand skin temperature in a different environment, a two-node hand thermophysiological model was developed and validated with published experimental data. In addition, a sensitivity analysis was performed which showed that the variations in skin blood flow and blood temperature are most influential on hand skin temperature. The hand model was applied to simulate the hand skin temperature of the obese and normal weight subgroup in different ambient conditions. Higher skin blood flow and blood temperature were used in the simulation of obese people. The results showed a good agreement with experimental data from the literature, with the maximum difference of 0.31 °C. If the difference between blood flow and blood temperature of obese and normal weight people was not taken into account, the hand skin temperature of obese people was predicted with an average deviation of 1.42 °C. In conclusion, when modelling hand skin temperatures, it should be considered that regional skin temperature distribution differs in obese and normal weight people.     

Factors causing variation in flock size: Decision making to join a foraging flock

In order to clarify the temporal variation of flock size, we examined factors that cause the temporal variation of foraging flock size in a wintering population of the Yellow-throated bunting (Emberiza elegans). We conducted field observations to examine whether the flock size varies greatly and whether non-random associations between individuals exist. We confirmed that flock size varied greatly and some individuals showed non-random associations with other flock members. Then, we carried out computer simulations that assume stochastic risky situation, the condition of hunger level and non-random associations between individuals. In the simulation, the condition of hunger level caused the variation of flock size. However, the distribution of flock size differed from observed ones. When the condition of non-random association was added to the simulation, the variation of flock size became large and the distribution of flock size was similar to that of the observed one. In wintering flocks of Yellow-throated bunting, each individual attempts to forage in an optimal flock size. However, if they are extremely starved, it is suggested that they adopt a conditional strategy to join a flock independently of the flock size to acquire the energy necessary for survival. Simultaneously, they may decide to forage under the effect of non-random association between individuals.     

Photosynthetic electron transport in relation to thylakoid membrane composition and organization

Abstract. A review is given of the organization and properties of thylakoid membrane proteins and lipids as a basis for understanding the factors which regulate the light reactions of photosynthesis. Particular emphasis is placed on the lateral organization of the major intrinsic multipeptide complexes and on the importance of diffusional processes in controlling the kinetics of electron transport and the distribution of light energy between photosystems 1 and 2.     

栖息地特征对褐马鸡种群密度和集群行为的影响

1998-2000年冬季在山西芦芽山自然保护区选择车道沟和梅洞 2个研究地,就栖息地特征对褐马鸡 (Cros soptilonmantchuricum)越冬种群密度和集群大小的影响进行了研究。经χ2 检验,针叶林是褐马鸡冬季经常利用的栖息地类型。对 2个研究地的栖息地结构比较发现,车道沟适宜栖息地的面积较梅洞大,连接性也较好,褐马鸡种群有更为广阔的取食空间和更多的隐蔽场所,而且活动的阻碍也较小;而梅洞栖息地的取食空间较小,隐蔽场所较少,其活动时受到的阻碍也较大。从 2个研究地微生境结构特征的差异,并结合褐马鸡越冬期栖息地选择来看,树高和高层盖度对褐马鸡在 2个栖息地的选择上起重要作用。车道沟乔木较粗大,不但有丰富的食物,而且可提供较好的夜宿条件;高层盖度越大,栖息地的隐蔽条件越好,能吸引更多的褐马鸡个体取食和越冬。研究结果表明,栖息地结构连接性、微生境结构特征的差异以及人为干扰是褐马鸡种群密度和集群行为差异的主要影响因素。     

Phosphatase activity in relation to phytoplankton composition and pH in Swedish lakes

SUMMARY. 1. Potential phosphatase activity and phytoplankton from several lakes of different character were compared in order to evaluate the importance of lake water pH and phytoplankton composition for the activity and pH optimum of lake water phosphatases.
2. In oligotrophic lakes, in which phytoplankton biomass was most often dominated by Ochromonadaceae spp., optimum phosphate activity was found at pH values <6. In eutrophic lakes, where species of Cyanophyceae and Bacillariophyceae dominated the phytoplankton biomass, optimum phosphatase activity was found at pH 7.5 or 8.5.
3. The pH optimum of phosphatase activity often differed from the corresponding lake water pH.
4. Experimental variation in phosphorus availability resulted in predictable changes in phosphatase activity. However, specific phosphatase activity, calculated per biomass of phytoplankton, was dependent on plankton species composition.     

Variation in the diet composition of a generalist predator, the red fox, in relation to season and density of main prey

Diet composition of a generalist predator, the red fox (Vulpes vulpes) in relation to season (winter or summer) and abundance of multi-annually cyclic voles was studied in western Finland from 1983 to 1995. The proportion of scats (PS; a total of 58 scats) including each food category was calculated for each prey group. Microtus voles (the field vole M. agrestis and the sibling vole M. rossiaemeridionalis) were the main prey group of foxes (PS = 0.55) and they frequently occurred in the scats both in the winter and summer (PSs 0.50 and 0.62, respectively). There was a positive correlation between the PSs of Microtus voles in the winter diet of foxes and the density indices of these voles in the previous autumn. Other microtine rodents (the bank vole Clethrionomys glareolus, the water vole Arvicola terrestris and the muskrat Ondatra zibethicus) were consumed more in winter than in summer. The unusually high small mustelid predation by red foxes (PS = approx. 0.10) in our study area gives qualitative support for the hypothesis on the limiting impact of mammalian predators on least weasel and stoat populations. None of the important prey groups was preyed upon more at low than at high densities of main prey (Microtus voles). This is consistent with the notion that red foxes are generalist predators that tend to opportunistically subsist on many prey groups. Among these prey groups, particularly hares and birds (including grouse), were frequently used as food by foxes.     

Encephalization and quantitative brain composition in bats in relation to their life-habits

A quantitative analysis of the brains of 43 bat species is presented. Eleven brain components were studied. The species were arranged according to seven distinct dietary groups and it was found that the relative development of the principal components is related to those groups. The importance of neocorticalization as a reflection of evolution of all the bats in contrast to specialization in some species is stressed. This work gives a clearer view of Chiropteran progressiveness or primitiveness: the insectivorous forms occupy the least advanced, although most specialized, level; the vampires, the carnivorous species and the flying foxes are at the top of the scale. The importance of behaviour and the relative development of the central nervous system in the hierarchial classification of mammals is stressed.     

Nectar sugar composition and concentration in relation to pollination syndromes in Bromeliaceae

A first comprehensive dataset of nectar sugar composition and concentration in Bromeliaceae is presented, covering 111 species belonging to all three subfamilies. Based on this dataset, we examined the relationship between nectar traits and pollination syndromes in the family. Sugars in samples were assayed by high pressure liquid chromatography. All sampled species were grouped into three broad categories (trochilophilous, chiropterophilous, or lepidopterophilous) according to their main pollination mode. Significant differences between the different pollination syndromes were found in nectar sugar composition as well as concentration. For a total of four genera (Guzmania, Pitcairnia, Tillandsia and Vriesea), a comparison of nectar composition showed significant differences between trochilophilous and chiropterophilous species. Data presented here indicate that the characteristics of nectar in Bromeliaceae are predominantly determined by putative adaptations of nectar sugars to preferences of the pollinators rather than by phylogenetic relations.