高原低氧适应动物新疆灰旱獭右心室重构的组织学改变

目的探讨新疆灰旱獭高原低氧适应性改变致右心室重构组织学改变。方法应用免疫组化技术检测新疆灰旱獭右心室缝隙连接蛋白43(CX43)蛋白表达,同时应用HE染色和Masson染色观察心室肌结构和纤维化程度变化。结果心肌细胞肥大,胶原纤维增多,右心室肥厚指数、体重指数明显增高。CX43蛋白表达减少和(或)分布的改变。结论高原低氧致新疆灰旱獭右心室结构重构,可作为研究高原低氧适应性机制的理想动物模型。     

The annual cycle of growth rate and biomass change in Planktothrix spp. in Blelham Tarn, English Lake District

SUMMARY 1. The changes in the vertical distributions of red coloured Planktothrix rubescens and green P. agardhii filaments in Blelham Tarn, English Lake District, were related to vertical profiles of temperature and light attenuation and to continuous records of the surface irradiance and windspeed, from August 1999 to October 2000. 2. The potential growth rate of each organism was calculated from the irradiance and temperature at 0.5 m depths and hourly intervals throughout the year, using algorithms determined from growth rates in culture. The analyses indicated that there was sufficient irradiance for growth, integrated over the 24‐h cycle, at depths down to the metalimnion where the Planktothrix populations stratified in summer. The compensation depth for growth by P. rubescens reached a maximum of 9.3 m in spring and midsummer, and fell to a minimum of 1.6 m in midwinter; the corresponding values for P. agardhii were 7.9 and 0.5 m. 3. The mixed depth (z_m) exceeded the critical depth for growth (z_b) by P. rubescens (the condition preventing population increase) on only 3 days of the year; for P. agardhii, however, z_m exceeded z_b on 31 days, contributing to its faster decline. The stratified population of P. rubescens was the major cause of light attenuation during the summer of 2000, and resulted in competitive exclusion of P. agardhii. 4. The calculated growth rates integrated over the depth of the water column in Blelham Tarn equalled, or exceeded, the measured changes of the populations during periods when they were increasing, during summer and autumn. Close agreement between the two values was found for much of the year when allowance was made for dilution of the lake population by rainfall over the watershed. During periods of rapid decline, of P. agardhii in September 1999, P. rubescens in December 1999 and both in July–August 2000, additional losses (e.g. by chytrid parasitism and grazing) are invoked.     

Evidence of high annual growth rate for lichens in the maritime Antarctic

On Livingston Island (South Shetland Islands, Antarctica) young moraines, now roughly 45 years old, were investigated in 1991 and 2002. More than 500 thalli of the 6 most abundant species, Acarospora macrocyclos, Bellemerea sp. Buellia latemarginata, Caloplaca sublobulata, Rhizocarpon geographicum and Usnea antarctica, previously measured in 1991, were measured again in 2002, which allowed an accurate measure of thallus growth rates. From our results, we believe it important to emphasize that: (1) lichen colonization probably took place at the end of the 1950s, soon after the last glacier retreat. (2) No relation between thallus growth rate and boulder size could be established. (3) Higher annual growth rates than those previously estimated were observed for R. geographicum and Bellemerea sp. and the former had one of the highest growth rates ever reported for this species. We speculate whether this high growth rate may be related to the rapid retreat of the Livingston Island ice cap and glaciers during the last recent years, and which have been attributed to climate warming on the Antarctic Peninsula region.     

Model for bacterial culture growth rate throughout the entire biokinetic temperature range.

The "square-root" relationship proposed by Ratkowsky et al. (J. Bacteriol. 149:1-5, 1982) for modeling the growth rate of bacteria below the optimum growth temperature was extended to cover the full biokinetic temperature range. Two of the four parameters of this new nonlinear regression model represent minimum and maximum temperature bounds, respectively, for the predicted growth of the culture. The new model is easy to fit and has other desirable statistical properties. For example, the least-squares estimators of the parameters of the model were almost unbiased and normally distributed. The model applied without exception to all bacterial cultures for which we were able to obtain data. Results for 30 strains are reported.     

Cell cycle model for growth rate and death rate in continuous suspension hybridoma cultures

As a result of recent advances in flow cytometry, renewed interest is shown in modeling the kinetic behavior of cells in culture on the basis of cell cycle parameters. An important but often overlooked kinetic variable in hybridoma cultures is the cell death rate. Not only the overall cell growth but also the kinetics of nutrient metabolism and monoclonal antibody production have been shown to depend on the cell death rate in continuous suspension hybridoma cultures. The present study shows that the death rate in hybridoma cultures is proportional to the fraction of cells arrested in the G(1) phase of the cell cycle. The steady-state cell age distributions in the various phases of the division cycle have been calculated analytically. A simple mathematical model has been used to produce the profiles of the cycling and arrested cell fractions with respect to the dilution rate. The calculated steady-state growth rate, death rate, and viability profiles are shown to be in agreement with recently published experimental data from continuous suspension hybridoma cultures. (c) 1992 John Wiley & Sons, Inc.     

Coupling among growth rate response, metabolic cycle, and cell division cycle in yeast

We studied the steady-state responses to changes in growth rate of yeast when ethanol is the sole source of carbon and energy. Analysis of these data, together with data from studies where glucose was the carbon source, allowed us to distinguish a "universal" growth rate response (GRR) common to all media studied from a GRR specific to the carbon source. Genes with positive universal GRR include ribosomal, translation, and mitochondrial genes, and those with negative GRR include autophagy, vacuolar, and stress response genes. The carbon source-specific GRR genes control mitochondrial function, peroxisomes, and synthesis of vitamins and cofactors, suggesting this response may reflect the intensity of oxidative metabolism. All genes with universal GRR, which comprise 25% of the genome, are expressed periodically in the yeast metabolic cycle (YMC). We propose that the universal GRR may be accounted for by changes in the relative durations of the YMC phases. This idea is supported by oxygen consumption data from metabolically synchronized cultures with doubling times ranging from 5 to 14 h. We found that the high oxygen consumption phase of the YMC can coincide exactly with the S phase of the cell division cycle, suggesting that oxidative metabolism and DNA replication are not incompatible.     

提高人工饲养条件下喜马拉雅旱獭成活率的几点体会

喜马拉雅旱獭（Marmota himalayaana）属啮齿目（Rodentia）松鼠科（Sciuridae）旱獭属（Marmnota）的大型地栖性啮齿动物,为青藏高原特有种,是我国和青海省哺乳动物资源开发利用的重点对象之一。近年来应用旱獭制作人类疾病的动物模型的研究越来越深入,乙肝病毒感染动物模型——中国旱獭的研究（国家自然科学基金项目,30271170）正在进行,对其的需求量越来越大,对动物的质量要求也越来越高。     

Apple dwarfing rootstocks and interstocks affect the type of growth units produced during the annual growth cycle: precocious transition to flowering affects the composition and vigour of annual shoots

Background and Aims: Precocious flowering in apple trees is often associated witha smaller tree size. The hypothesis was tested that floral evocationin axillary buds, induced by dwarfing rootstocks, reduces thevigour of annual shoots developing from these buds comparedwith shoots developing from vegetative buds. Methods: The experimental system provided a wide range of possible treevigour using ‘Royal Gala’ scions and M.9 (dwarfing)and MM.106 (non-dwarfing) as rootstocks and interstocks. Second-yearannual shoots were divided into growth units corresponding toperiods (flushes) of growth namely, vegetative spur, extensiongrowth unit, uninterrupted growth unit, floral growth unit (bourse)and extended bourse. The differences between the floral andvegetative shoots were quantified by the constituent growthunits produced. Key Results: The dwarfing influence was expressed, firstly, in reduced proportionsof shoots that contained at least one extension growth unitand secondly, in reduced proportions of bicyclic shoots (containingtwo extension growth units) and shoots with an uninterruptedgrowth unit. In treatments where floral shoots were present,they were markedly less vigorous than vegetative shoots withrespect to both measures. In treatments with M.9 rootstock,vegetative and floral shoots produced on average 0·52and 0·17 extension growth units, compared with 0·77extension growth units per shoot in the MM.106 rootstock treatment.Remarkably, the number of nodes per extension growth unit wasnot affected by the rootstock/interstock treatments. Conclusions: These results showed that rootstocks/interstocks affect thetype of growth units produced during the annual growth cycle,reducing the number of extension growth units, thus affectingthe composition and vigour of annual shoots. This effect isparticularly amplified by the transition to flowering inducedby dwarfing rootstocks. The division of annual shoot into growthunits will also be useful for measuring and modelling effectsof age on apple tree architecture.     

Sex steroids, growth and condition of Arctic charr broodstock during an annual cycle

Changes in plasma concentrations of sex steroids, growth rate and condition of repeat spawning (3+) male and female Arctic charr were studied throughout an annual reproductive cycle. Individually marked fish (mean weight approx. 500 g) were held under conditions of liberal food supply, constant temperature (4° C) and simulated natural photoperiod (Tromsø, 70° N). Once each month fish were weighed, measured and blood samples taken for steroid analysis. Plasma concentrations of testosterone (T), 11-ketotestosterone (11-KT) and oestradiol-17β (E₂) were determined using radioimmunoassay (RIA). Both male and female fish displayed distinct seasonal changes in plasma concentrations of sex steroids, growth rate and condition. From February (minimal concentrations) to March all sex steroids increased slightly and these elevated concentrations were maintained until May. Thereafter, there was a second, and far more pronounced, increase in plasma steroid concentrations which culminated in peak steroid concentrations in September–October. There was then a rapid decline during the spawning period. In winter, growth rate and condition were generally low, then increased during the spring, reached a peak during the summer, and then declined with the onset of autumn. During spring (March–May), the frequency distributions of plasma testosterone concentrations in both male and female fish were bimodal. The fish of the upper modal group of the distribution had significantly higher growth rates and condition than those in the lower modal group. In summer and early autumn (June–September) the association between T and growth rate changed. Significant negative correlations between T and growth rates were observed in females. There was an increase in endocrine activity, indicated by elevated plasma sex steroid concentrations in March, 7–8 months prior to maturation. It is suggested that this may be one factor influencing the onset of spring growth and energy deposition among maturing charr.     

Direct and indirect calorimetry measurements during the annual growth cycle of juvenile frogs Rana ridibunda P

A thermodynamic study of the energetic metabolism in juvenile amphibians was conducted over an annual cycle of growth. The total energy flux (delta H = enthalpy variation) was measured with direct microcalorimetry and accounted for the sum of all metabolic pathways. Indirect calorimetry, oxygen consumption measurements (VO2), provides the values for the oxidative metabolism-dependent energy. A comparison between the results of both techniques simultaneously performed, provides for the calculation of the energetic efficiency, which indicates the respective importance of aerobic and anaerobic metabolisms during the annual biological cycle. It is clear that oxidative metabolism does not represent all, nor even a constant percentage of the total energy production of the frog, Rana ridibunda. The ration (Formula: see text) varied between 0.72 and 1.00, according to the season and the feeding or fasting periods. These results are discussed with special reference to the ecophysiology and behaviour of this species.     

Evolution of the genomic recombination rate in murid rodents

Although very closely related species can differ in their fine-scale patterns of recombination hotspots, variation in the average genomic recombination rate among recently diverged taxa has rarely been surveyed. We measured recombination rates in eight species that collectively represent several temporal scales of divergence within a single rodent family, Muridae. We used a cytological approach that enables in situ visualization of crossovers at meiosis to quantify recombination rates in multiple males from each rodent group. We uncovered large differences in genomic recombination rate between rodent species, which were independent of karyotypic variation. The divergence in genomic recombination rate that we document is not proportional to DNA sequence divergence, suggesting that recombination has evolved at variable rates along the murid phylogeny. Additionally, we document significant variation in genomic recombination rate both within and between subspecies of house mice. Recombination rates estimated in F(1) hybrids reveal evidence for sex-linked loci contributing to the evolution of recombination in house mice. Our results provide one of the first detailed portraits of genomic-scale recombination rate variation within a single mammalian family and demonstrate that the low recombination rates in laboratory mice and rats reflect a more general reduction in recombination rate across murid rodents.     

Reproductive synchrony and annual variation in foetal growth rate in the long-fingered bat (Miniopterus schreibersii)

Mating in the long-fingered bat (Miniopterus schreibersii) from the East Cape region of South Africa occurred during a four-week period in April and May, and implantation was delayed until August. Analyses of foetal age and estimated dates of conception indicate that after implantation, the progression of pregnancy within the population was synchronous both within and between years. It is suggested that implantation, probably initiated by increasing day length, occurred at about the same time throughout the population and thus synchronized reproduction. In the final month of pregnancy foetal growth rate and, consequently, the timing of parturition in the three years of the study varied. These variations were correlated with variations in rainfall and it is suggested that the failure of the November rains in 1990 would have caused a reduction in insect abundance and that this was responsible for the decrease in foetal growth rate and the delay in parturition.     

Buoyant density, growth rate, and the cell cycle in Streptococcus faecium.

The buoyant density in rapidly growing Streptococcus faecium 9790 cells varies over the cell cycle, in contrast to the density in Escherichia coli. Buoyant density in S. faecium was measured by using Percoll (Pharmacia Fine Chemicals, Piscataway, N.J.) density gradients. We found that the mean and coefficient of variation of the population density increased with growth rate; and within a population, the mean cell volume, which was measured electronically, increased with density. These results were compared with electron microscopic measurements of the size distributions of cell wall growth sites within each fraction of the density gradient. As the density increased within a population, the frequency of large cells increased and the frequency of newly initiated cell wall growth sites increased. These effects were more marked as the growth rate increased. Next, these data were regrouped by cell size by using the size of the central growth site as an index of cell cycle stage. Each frequency value was weighted by the proportion of the population represented by that density fraction. Then, the average buoyant density was calculated for each value of cell size. In all cell populations, the density decreased and then increased as the central site enlarged. Peripheral growth sites were initiated as density reached a maximum. At faster growth rates, density increased more steeply, and new peripheral growth sites opened up at a higher frequency. We suggest that the rate at which density increases during the cell cycle correlates with the initiation of new cell wall growth sites.     

Changes in inflammatory activity,heart rate variability,and biochemical indices in young athletes during the annual training cycle

Inflammatory activity, heart rate variability (HRV), and biochemical and functional indices were assessed in young ski racers during the preparation, competition, and recovery periods of an annual training cycle. During the preparation period, autohemodilution (decreased red blood cell count (RBC) and hematocrit (Ht) levels) and a decrease in the systemic inflammatory activity (C-reactive protein) occurred, without significant differences in the HRV or serum protein and lipid profile. During the competition period, the systemic inflammatory activity increased by 50% (p = 0.047), eliminating differences from the control group, and the HRV indices (SDNN, HF, TP, and IT) decreased (p ≤ 0.013), indicating an increase in the sympathetic effects on the HRV. During the recovery period, hematological indices (Ht and RBC), inflammatory activity, and fibrinogen levels decreased, and the parasympathetic effects on the heart increased. These findings allowed us to conclude that mental and physical activation led to a moderate increase in the systemic inflammatory activity and a shift in the sympathovagal balance towards increased sympathetic activity, providing a nonspecific contribution to the physiological regulation of biochemical (lipoproteins and immunoglobulins) and hematological indices in the athletes. However, similar changes in many biochemical and hematological indices in both groups during the year indicated the important role of a common, probably seasonal, factor in the regulation.     

Effect of soil nitrogen stress on the relative growth rate of annual and perennial grasses in the Intermountain West

A high relative growth rate (RGR) is thought to be an important trait allowing invasive annual grasses to exploit brief increases in nitrogen (N) supply following disturbance in the Intermountain West. Managing soils for low N availability has been suggested as a strategy that may reduce this growth advantage of annual grasses and facilitate establishment of desirable perennials grasses. The objective of this study was to examine the degree to which soil N availability affects RGR and RGR components of invasive annual and desirable perennial grasses. It was hypothesized that (1) invasive annual grasses would demonstrate a proportionately greater reduction in RGR than perennial grasses as soil N stress increased, and (2) the mechanism by which low N availability decreases RGR of annual and perennial grasses would depend on the severity of N stress, with moderate N stress primarily affecting leaf mass ratio (LMR) and severe N stress primarily affecting net assimilation rate (NAR). Three annual and three perennial grasses were exposed to three levels of N availability. RGR and components of RGR were quantified over four harvests. Moderate N stress reduced RGR by decreasing LMR and severe N stress lowered RGR further by decreasing NAR. However, reduction in RGR components was similar between invasive and natives, and as a consequence, annual grasses did not demonstrate a proportionately greater reduction in RGR than perennials under low N conditions. These results suggest managing soil N will do little to reduce the initial growth advantage of annual grasses. Once perennials establish, traits not captured in this short-term study, such as high tissue longevity and efficient nutrient recycling, may allow them to compete effectively with annuals under low N availability. Nevertheless, if soil N management does not facilitate the initial establishment of perennials in annual grass infested communities, then there is little likelihood that such techniques will provide a long-term benefit to restoration projects in these systems.