The antimutagenic effect of selenium on 7,12-dimethylbenz(a)anthracene and metabolites in the amesSalmonella/microsome system

The antimutagenic effect of selenium as sodium selenite, sodium selenate, selenium dioxide, and seleno-methionine was studied in the AmesSalmonella/microsome mutagenicity test using 7,12-dimethylbenz(a)anthracene (DMBA) and some of its metabolites. Selenium (20 ppm) as sodium selenite reduced the number of histidine revertants on plates containing up to 100 μg DMBA/plate. Increasing concentrations of selenium as sodium selenite, sodium selenate, and selenium dioxide up to 40 ppm Se progressively decreased the number of revertants caused by 50 μg DMBA. DMBA and its metabolites 7-hydroxymethyl-12-methylbenz(a)anthracene, 12-hydroxymethyl-7-methylbenz(a)anthracene, and 3-hydroxy-7,12-dimethylbenz(a)anthracene were mutagenic forSalmonella typhimurium TA100 in the presence of an S-9 mixture. Selenium supplementation as Na₂SeO₃ reduced the number of revertants induced by these metabolites to background levels. The antimutagenic effect of inorganic selenium compounds cannot be explained by toxicity of selenium as determined by viability tests withSalmonella typhimurium TA100. Selenium supplementation in all forms examined, except sodium selenate, decreased the rate of spontaneous reversion. Selenium as sodium selenate was slightly mutagenic at concentrations of 4 ppm or less. Higher concentration of Na₂SeO₄ inhibited the mutagenicity of DMBA. The present studies support the anticarcinogenic potential of selenium and indicate that form and concentration are important factors in this trace element's efficacy.     

Oocyte-follicle cell relationships in a starfish

Summary The follicle cells which surround the oocytes of starfish are known to both release the hormone 1-methyladenine and to respond to it by an active movement which forms a component of the spawning response to the hormone. In Patiria miniata these flagellated cells are located peripheral to the oocyte and have long cytoplasmic processes which penetrate the vitelline layer to the egg surface to form an adhering zonule-like junction. Within the follicle cell cytoplasm are located elongate filamentous bands which appear to represent a component of the contractile mechanism that mediates follicle cell response to 1-methyladenine. These bands do not resemble the filaments of vertebrate smooth muscle cells (quantity, distribution and size of filaments; lack of dense bodies in the filament mass), nor the contractile units of the superficial epithelium of lower vertebrate follicles.This investigation was supported by grants HD-07194 and HD-12499 from the National Institutes of Health. We are indebted to Mr. James D. Huber for able technical assistance     

The first optic ganglion of the bee

Summary The arrangement of first and second order neurons in an optic cartridge and the topographical relationships of the second order neurons within a cartridge and to groups of surrounding cartridges have been analyzed in the visual system of the bee, Apis mellifera, from light and electron microscope studies on Golgi preparations. At the level of the monopolar cell body layer, the nine retinula cell fibres of each ommatidium, the six short visual fibres arranged in a circle surrounding the three long visual fibres, become cartridges as a consequence of the appearance of the second order neurons (L-fibres) which join the R-fibre bundles. Two of the four different L-fibre types, L-1 and L-2, remain together in the centre of the cartridge throughout the lamina. The axons of the L-3 and L-4 fibres, however, have their position integrated into the circle formed by the endings of the short visual fibres. On the basis of further examination of light and especially electron microscopical Golgi material, the different L-fibres can be classified into four types which appear in each cartridge. The clear stratification in the first synaptic region (A, B and C) seems to be the best criterion for a morphological classification since such a classification necessarily also includes a functional basis. According to a naming system based on the position of the lateral processes, L-fibres with side branches in strata A, B and C are called L-1 fibres. Fibres with lateral processes in strata A and B are L-2 fibres; monopolar cell fibres with branches only in the second stratum B are L-fibres of type 3; and all monopolar cells with branches only in stratum C are called L-4 fibres. In addition to the branching pattern covering only the parent cartridge, two of the four fibre types (L-2 and L-4) have long collaterals reaching neighbouring cartridges: L-2 in stratum A and L-4 in stratum C. These collaterals presumably form a substrate for lateral interactions.     

The pineal gland of the mole-rat (Spalax ehrenbergi,Nehring)

Summary A comparative investigation of the distribution of monoaminergic neurons in non-malacostracan crustaceans was performed with the histochemical fluorescence method of Falck-Hillarp.Two fluorophores were found: the more widespread of the two emits a green fluorescence; and the more sparsely distributed emits a yellow to brown-yellow fluorescence.Specific green fluorescent areas were shown to exist in the protocerebrum. The central body and the optic ganglia of the compound eye (where present) are always fluorescent. Moreover, the centre of the nauplius eye may have a green fluorophore, as in ostracods, and a neuropile area, here called the frontal area. These neuropile centres are known from ordinary histological studies of the nervous system. In addition, there are specific monoaminergic centres, such as the so-called dorsal area of phyllopods and anostracans as well as the copepod specific areas. Specific monoaminergic areas appear in the deutocerebrum and the suboesophageal ganglion where they are particularly well developed.Presumed sensory neurons in the cavity receptor organ of Artemia salina are shown to be monoaminergic. Monoaminergic sensory neurons have not been described previously in Arthropods.Presumed motor innervation of hind-gut and trunk muscles is also found, and it is concluded that in crustaceans neurons of every type (sensory, internuncial, motor) may be monoaminergic.We have enjoyed unrestricted laboratory facilities at the Department of Histology, Faculty of Medicine, and with great pleasure express our sincere thanks to Prof. Bengt Falck. — Grants from the Swedish Natural Science Research Council (2760-007), the Swedish Medical Research Council (04X-712), the Royal Swedish Academy of Science (Hierta-Retzius), the Royal Physiographic Society of Lund, and the University of Lund supported the work.     

Mapping of neurons in the gravity receptor system of the octopus statocyst by iontophoretic cobalt staining

Summary The presence of uni-, bi- and multipolar neurons beneath the hair cell epithelium of the Octopus gravity receptor system has been demonstrated by iontophoretic cobalt staining. Counts give an average number of 1,940 neurons per macula. Whether the hair cells are primary of secondary sensory cells is discussed.This work was supported by grant Wo 160/3 of the Deutsche Forschungsgemeinschaft (DFG) to H.G.W. Thanks are due to the Director and staff of the Zoological Station in Naples for their hospitality and help     

Time- and dose-dependent influence of ouabain on the ultrastructure of optic neurones

The cardiac glycoside ouabain was injected into the eye-bulb of the teleost fish, Carassius carassius. Three doses of ouabain were used: 10(-4) M, 10(-5) M, 10(-6) M. The final concentrations in the vitreous body of the eye were approximately 3-10(-5) M, 3-10-6 M and 3-10-7 M, respectively. After 8 hrs, 1, 2, 4, 6 and 8 days the ultrastructural alterations of retinal ganglion cells, the optic axons near the bulb and the terminal segments in the optic tectum were studied. The high doses of ouabain induced an early necrobiosis of the cell bodies in the retina followed by degeneration in the nerve. This is characterized as a protracted form of Wallerian degeneration. The significance of the inhibition of Na+ -K+-activated ATPase at the perikaryal level for both the integrity of axonal morphology and the axonal flow is discussed.     

基于SD的生态安全指标阈值的确定及应用——以上海崇明岛为例

结合区域复合生态系统的特点,建立由经济、人口、资源、环境和生态5个子系统71个参数构成的上海崇明岛区域生态安全的系统动力学模型,并以变量"净GDP"为参考依据,通过情景仿真进行生态安全趋势分析和方案比较,确定生态安全的指标阈值;通过系统模拟对阈值进行验证,认为阈值在反映系统动态发展趋势上,是一定发展模式下的生态安全的特征参照系。这一尝试克服了目前生态安全指标阈值的研究中以参照法为主的静态性缺憾。将确定的阈值应用于崇明岛生态安全的评价和因子分析中,发现由于崇明岛生态岛的定位和生态保障措施的实施,近几年生态安全综合得分呈现逐步提高的特点,但目前(2007年)得分为0.523,仍处于中等水平;并以阈值为标准的因子检验发现各主要安全因子差异较大,主要的制约因子主要体现为环境治污水平和能源利用等方面。     

Acetic acid and acidification accelerate chronological and replicative aging in yeast

Comment on: Murakami C, et al. Cell Cycle 2012; 11:3087-96.     

Reconfiguration of a Multi-oscillator Network by Light in the Drosophila Circadian Clock

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林农复合经营生态体系的研究

林农复合经营以生态经济学的原理,运用现代生物和生态工程方法技术,组成林、农、牧、副、渔有机结合的复合生产体系。它突破了传统林业的单一生产方式,形成以林为主的一个复合的、开放的、具有整体效应的生态系统。这种复合系统能有效地提高土地资源利用率,促进太阳能和有关物质在系统内的多次循环利用,实现整个系统在空间和时间上的高效利用。多年来的研究表明,这种由多种产业部