Target size analysis by radiation inactivation: a large capacity tube rack for irradiation in a Gammacell 220

Target size analysis by radiation inactivation is now a well-established method to study structure-function relationships in biologically active macromolecules without prior purification or even solubilization. Recently, it was reported that a relatively low-dose-rate but commonly available gamma source such as the Gammacell 220 (Atomic Energy of Canada, Ltd.) can be used to carry out radiation inactivation experiments providing it is appropriately calibrated with enzymes of known radiation sensitivities (G. Beauregard and M. Potier (1982) Anal. Biochem. 122, 379-384). In this report, a tube rack designed to fit into the irradiation chamber of the Gammacell 220 which allows five experiments (at 30 tubes per experiment) to be carried out simultaneously with both standard and unknown samples is described. The dose rates delivered at different positions in the rack were determined by irradiating rat liver cytosolic neuraminidase, an enzyme of known radiation sensitivity. A better than 2.7% agreement was obtained between experimental dose rate and computed values from isodose curves previously published by other authors (O. A. Curzio and H. O. Quaranta (1982) Int. J. Appl. Radiat. Isot. 33, 1-3).     

Characteristics and determinants of osmotic lysis in chromaffin granules

(1) Using isolated bovine chromaffin granules, we demonstrate that osmotic lysis is not a random process and establish the osmotic pressure dependence of osmotic lysis in chromaffin granules, the so-called osmotic fragility curve. (2) We show by measuring the release of constituents of the granule core and correlating these with changes in spectroscopic parameters (turbidity and endogenous catecholamine fluorescence), that the latter can be safely used to measure lysis. (3) Within a particular granule population, noradrenaline granules lyse at higher osmolarities than adrenaline granules, suggesting a higher core osmolarity of the noradrenaline granules. (4) The size distribution of chromaffin granules as a function of lysis was determined by the use of whole mount electron microscopy. It is shown that the mean size of chromaffin granules decreases as a function of lysis. (5) On the basis of theoretical considerations three alternative models of the sequence of osmotic lysis in chromaffin granules are proposed. The experimental results best support a model which postulates that during partial osmotic lysis, granule membranes reseal into smaller vesicles after graded release of contents. The osmotic fragility would represent several cycles of lysis and resealing and would not be a reflection of the distribution of osmotic pressures in the granule population.     

Production of Reactive Oxygen Species and Release of l-Glutamate During Superoxide Anion-Induced Cell Death of Cerebellar Granule Neurons

Abstract: Enhanced production of superoxide anion (O₂⁻) is considered to play a pivotal role in the pathogenesis of CNS neurons. Here, we report that O₂⁻ generated by xanthine (XA) + xanthine oxidase (XO) triggered cell death associated with nuclear condensation and DNA fragmentation in cerebellar granule neuron. XA + XO induced significant increases in amounts of intracellular reactive oxygen species (ROS) before initiating loss of cell viability, as determined by measurement of 6-carboxy-2',7'-dichlorodihydrofluorescein diacetate, di(acetoxymethyl ester) (C-DCDHF-DA) for O₂⁻ and other ROS and hydroethidine (HEt) specifically for O₂⁻ by using fluorescence microscopy and flow cytometry. Catalase, but not superoxide dismutase (SOD), significantly protected granule neurons from the XA + XO-induced cell death. Catalase effectively reduced C-DCDHF-DA but not HEt fluorescence, whereas SOD reduced HEt but not C-DCDHF-DA fluorescence, indicating that HEt and C-DCDHF-DA fluorescence correlated with O₂⁻ and hydrogen peroxide, respectively. The NMDA antagonist MK-801 prevented the death. XA + XO induced an increase in l -glutamate release from cerebellar granule neurons. These results indicate that elevation of O₂⁻ induces cell death associated with increasing ROS production in cerebellar granule neurons and that XA + XO enhanced release of l -glutamate.     

Size of prey ingested by whitefish,Coregonus sp., larvae. Are Coregonus larvae gape-limited predators?

The feeding ecology of whitefish, Coregonus , larvae in oligotrophic Lake Sarnen and eutrophic Lake Hallwil is presented, taking into consideration the size of the prey ingested in relation to the mouth size of larvae and to the availability of zooplankton.
When larvae grow from 10 to 16 mm their mouth width increases from 500 to 1000 μm while their gape height, with the mouth open at 45 and 90°, increases from 200 to 400 μm and from 400 to 700 μm, respectively, whichever lake is considered.
The differences found in the mean prey width between the two lakes arise in part from the composition of diets, and in part from differences in size of the available prey organisms. Whatever the origin of the larvae and the taxon we consider, larvae seem to ingest the most abundant prey size without selecting the biggest ones available even if, from a mechanical point of view, they would be able to ingest them.
Taking into account the generally low density of zooplankton in the uppermost layer of the lake, we conclude that whitefish larvae eat in the manner such as to decrease the cost of prey capture, in terms of energy and time, by choosing the more abundant prey available.     

西沙群岛东岛小军舰鸟繁殖种群的初步观察

2003年3-4月对西沙群岛的鸟类资源进行了考察,在西沙群岛的东岛发现小军舰鸟(Fregata minor)繁殖,为迄今所知该种在我国仅有的繁殖记录。野外观察共发现7个巢,其中5个巢中途毁损,另见幼鸟13只,非繁殖雄性个体2只。还观察到小军舰鸟与红脚鲣鸟相互影响的负面行为,如抢食、窃巢材等。调查结果显示,西沙群岛小军舰鸟分布范围现已缩小,而且种群数量显著下降。     

Blinded sample size recalculation in multiple composite population designs with normal data and baseline adjustments

The increasing interest in subpopulation analysis has led to the development of various new trial designs and analysis methods in the fields of personalized medicine and targeted therapies. In this paper, subpopulations are defined in terms of an accumulation of disjoint population subsets and will therefore be called composite populations. The proposed trial design is applicable to any set of composite populations, considering normally distributed endpoints and random baseline covariates. Treatment effects for composite populations are tested by combining p-values, calculated on the subset levels, using the inverse normal combination function to generate test statistics for those composite populations while the closed testing procedure accounts for multiple testing. Critical boundaries for intersection hypothesis tests are derived using multivariate normal distributions, reflecting the joint distribution of composite population test statistics given no treatment effect exists. For sample size calculation and sample size, recalculation multivariate normal distributions are derived which describe the joint distribution of composite population test statistics under an assumed alternative hypothesis. Simulations demonstrate the absence of any practical relevant inflation of the type I error rate. The target power after sample size recalculation is typically met or close to being met.     

The ant Lasius niger shows no relationship between task efficiency and body size variation among workers

In ants, workers of different sizes may perform various tasks, even in so-called monomorphic species with relatively low body size variation. However, it is unclear if the body size diversity of monomorphic workers correlates with task efficiency, especially in stressful contingencies. Here we tested if the body size variation of workers corresponds with its efficiency in transferring pupae. Transferring brood is a pre-set behavioral response to stress, e.g. suboptimal temperature. Here we applied a laboratory experiment simulating nest damage. The study was performed on the common garden ant (Lasius niger (Linnaeus, 1758)) – a species with no distinct worker subcastes. The efficiency of workers was measured as the latency of transferring pupae from a lit part of the experimental colony to a darkened part, while the body size diversity was expressed as the within-colony coefficient of variation in head width. We did not find any significant correlation between efficiency and body size variation. Summarizing the existing studies and the present results, we propose the hypothesis that the body size diversity of L. niger may have implications for workers’ division of labor but not for their task efficiency in a stressful contingency.     

Shrinking body size and climate warming: Many freshwater salmonids do not follow the rule

Declining body size is believed to be a universal response to climate warming and has been documented in numerous studies of marine and anadromous fishes. The Salmonidae are a family of coldwater fishes considered to be among the most sensitive species to climate warming; however, whether the shrinking body size response holds true for freshwater salmonids has yet to be examined at a broad spatial scale. We compiled observations of individual fish lengths from long-term surveys across the Northern Hemisphere for 12 species of freshwater salmonids and used linear mixed models to test for spatial and temporal trends in body size (fish length) spanning recent decades. Contrary to expectations, we found a significant increase in length overall but with high variability in trends among populations and species. More than two-thirds of the populations we examined increased in length over time. Secondary regressions revealed larger-bodied populations are experiencing greater increases in length than smaller-bodied populations. Mean water temperature was weakly predictive of changes in body length but overall minimal influences of environmental variables suggest that it is difficult to predict an organism's response to changing temperatures by solely looking at climatic factors. Our results suggest that declining body size is not universal, and the response of fishes to climate change may be largely influenced by local factors. It is important to know that we cannot assume the effects of climate change are predictable and negative at a large spatial scale.     

不同粒径口蹄疫病毒样颗粒-ZIF-8复合物诱导小鼠的体液免疫效果分析

为进一步提高口蹄疫(foot-and-mouthdisease,FMD)病毒样颗粒(virus-likeparticles,VLPs)疫苗的免疫效果,本研究采用仿生矿化方法,将Zn2+和2-甲基咪唑按照不同浓度配比制备了不同粒径的FMDV VLPs-沸石咪唑骨架-8 (zeolitic imidazolate framework-8, ZIF-8)复合物,以探究尺寸效应对免疫效果的影响。结果显示,成功制备出3种不同粒径的FMDV VLPs-ZIF-8,粒径分别约为70、100、1 000 nm。细胞毒性和组织病理学试验表明,3种复合物均具有良好的生物安全性。小鼠免疫试验表明,3种复合物均能明显提高中和抗体和特异性抗体水平,并且随着复合物体积的减小,其免疫效果也随之增强。本研究表明,ZIF-8包封FMDV VLPs可显著增强其免疫效果,且具有尺寸依赖性。     

Distribution of mRNAs Encoding the Peroxisome Proliferator-Activated Receptor α, β, and γ and the Retinoid X Receptor α, β, and γ in Rat Central Nervous System

Abstract: We report the isolation, by RT-PCR, of partial cDNAs encoding the rat peroxisome proliferator-activated receptor (PPAR) isoforms PPARα, PPARβ, and PPARγ and the rat retinoid X receptor (RXR) isoforms RXRα, RXRβ, and RXRγ. These cDNAs were used to generate antisense RNA probes to permit analysis, by the highly sensitive and discriminatory RNase protection assay, of the corresponding mRNAs in rat brain regions during development. PPARα, PPARβ, RXRα, and RXRβ mRNAs are ubiquitously present in different brain regions during development, PPARγ mRNA is essentially undetectable, and RXRγ mRNA is principally localised to cortex. We demonstrate, for the first time, the presence of PPAR and RXR mRNAs in primary cultures of neonatal meningeal fibroblasts, cerebellar granule neurons (CGNs), and cortical and cerebellar astrocytes and in primary cultures of adult cortical astrocytes. PPARα, PPARβ, RXRα, and RXRβ mRNAs are present in all cell types, albeit that PPARα and RXRα mRNAs are at levels near the limit of detection in CGNs. PPARγ mRNA is expressed at low levels in most cell types but is present at levels similar to those of PPARα mRNA in adult astrocytes. RXRγ mRNA is present either at low levels, or below the level of detection of the assay, for all cell types studied.