Influence of neuroendocrine shifts in the pubertal period on the working memory operation in adolescents

It was found that the volume of working memory in adolescents at the initial pubertal stages (II–III) was lower than in adults. Analysis of the event-related potentials (ERPs) in various cortical areas in adolescents when they compared two successive pictures revealed specific features of neurophysiological mechanisms of visual working memory at the early pubertal stages. As compared to adult subjects, the adolescents were characterized by longer latencies and higher amplitudes of the early components of the ERPs. Certain differences were revealed in the functional organization of working memory both at the stages of stimulus fixation and in its comparison with the current information.     

Localization of voltage-sensitive calcium channels along developing neurites: their possible role in regulating neurite elongation

Calcium action potentials were extracellularly recorded from growth cones of differentiated N1E-115 neuroblastoma cells maintained in monolayer cultures. Extracellular recordings along the neurites suggest that voltage-activated Ca²⁺ channels are less abundant in the processes than in the growth cones. In order to investigate if Ca²⁺ entry into the growth cone plays a role in the regulation of neurite growth, we studied the morphological changes induced by experimental conditions which permit calcium entry. Cells were depolarized either by 30 mM potassium (for 10–60 min) or by stimulating the soma (for 20–120 min) with an intracellular electrode. Morphological changes in individual cells were followed by means of time-lapse video recordings. In more than 60% of the experiments, steady-state potassium depolarization induced a pronounced increase of 20–120% in the area of the growth cone. This was frequently associated with neurite elongation. However, such changes could not be detected in the presence of Cd²⁺ concentrations which block the Ca²⁺ channels. Similar results were obtained in the presence of 2 μM of the Ca²⁺ ionophore A-23187 or when the cells were repetitively stimulated (0.2 Hz) in a medium containing 10^?6M TTX and 15 mM TEA. Local microapplication, directly onto single growth cones, of a depolarizing solution containing 5 mM Ca²⁺ also led to similar observations. Scanning electron microscopy indicated that the depolarized growth cone membranes were flattened and contained markedly more rounded protuberances relative to control cultures. Our results indirectly suggest that Ca²⁺ entry might be a trigger in the process of neurite elongation.     

Enzymatic S-de-ethylation and the mechanism of S-dealkylation.

An NADPH- and oxygen-dependent enzymatic system responsible for the formation of acetaldehyde from ethylthioethers is present in the 9000 g supernatant fraction of rat liver. This system appears to be quite similar to the one responsible for the formation of formaldehyde from methylthioethers. Although both of these systems appears to be microsomal mixedoxidase systems, several anomalous findings regarding the mechanism of microsomal S-dealkylation have been observed and have led us to the conclusion that the mechanism of this reaction is more complex than originally believed. A scheme is postulated by which an enzyme in the soluble fraction causes microsomal sulfoxidation of alkylthioethers to alkylsulfoxides, followed by metabolism of the alkylsulfoxides to aldehydes.     

The early life history of two sympatric New Zealand octopuses: eggs and paralarvae of Octopus huttoni and Pinnoctopus cordiformis

This study combined morphological and morphometric information on egg clutches, egg capsules and paralarvae of two sympatric coastal octopuses from New Zealand waters, Octopus huttoni and Pinnoctopus cordiformis, to provide species-specific traits to identify their early life stages obtained from field surveys. Eggs of O. huttoni (2.5 mm length; 1 mm width) were entwined with one another forming strings that ranged from 11 to 25.8 mm in length. Eggs of P. cordiformis (6.4 mm length; 1.5 mm width) were significantly bigger than those of O. huttoni and were grouped in small clusters of about seven eggs. Paralarvae O. huttoni and P. cordiformis differed in hatching size (1.4 mm versus 3.1 mm mantle length), number of suckers per arm (four versus eight), number of lamellae per outer demibranch (five versus ten) and arrangements of chromatophores in the body surface (29 to 59 versus 91 to 179), respectively. The morphological traits described in hatchlings from the laboratory allowed comparisons with field-collected paralarvae, suggesting that such characters were reliable species-specific patterns to enable a consistent differentiation between the early life stages of these two sympatric species, even in the absence of the brooding female.     

Americans all: Black and single‐parent families in the inner city

Bette J. Dickerson (ed.), AFRICAN AMERICAN SINGLE MOTHERS: UNDERSTANDING THEIR LIVES AND FAMILIES, Thousand Oaks, CA: Sage Publications, 1995, xxxii + 200 pp., $24.00 (paper).

Linda Gordon, PITIED BUT NOT ENTITLED: SINGLE MOTHERS AND THE HISTORY OF WELFARE 1890–1935, Cambridge, MA: Harvard University Press, 1994, 433 pp., $15.95 (paper).

Joyce A. Ladner, TOMORROW'S TOMORROW: THE BLACK WOMAN, Lincoln, NE: The University of Nebraska Press, 1995, xxiii + 304 pp., $12.00 (paper).

Carl Husemoller Nightingale, ON THE EDGE: A HISTORY OF POOR BLACK CHILDREN AND THEIR AMERICAN DREAMS, New York: Basic Books, 1993, xv + 254 pp., $14.00 (paper).

M. Belinda Tucker and Claudia Mitchell‐Kernan, (eds), THE DECLINE IN MARRIAGE AMONG AFRICAN AMERICANS: CAUSES, CONSEQUENCES AND POLICY IMPLICATIONS, New York: Russell Sage Foundation, 1995, xxiv + 397 pp., $49.95 and $19.95 (paper).     

Distribution of Clostridium botulinum Type E Strains in Nunavik,Northern Quebec,Canada

The distribution and levels of Clostridium botulinum type E were determined from field sites used by Inuit hunters for butchering seals along the coast of Nunavik. The incidence rates of C. botulinum type E in shoreline soil along the coast were 0, 50, and 87.5% among samples tested for the Hudson Strait, Hudson Bay, and Ungava Bay regions, respectively. Spores were detected in seawater or coastal rock surfaces from 17.6% of butchering sites, almost all of which were located in southern Ungava Bay. Concentrations of C. botulinum type E along the Ungava Bay coast were significantly higher than on the coasts of Hudson Strait and Hudson Bay, with the highest concentrations (270 to 1,800/kg of sample) found near butchering sites located along the mouths of large rivers. The Koksoak River contained high levels of C. botulinum type E, with the highest median concentration (270/kg) found in sediments of the marine portion of the river. C. botulinum type E was found in the intestinal contents (4.4%) and skins (1.4%) of seals. A high genetic biodiversity of C. botulinum type E isolates was observed among the 21 butchering sites and their surroundings along the Nunavik coastline, with 83% of isolates (44/53) yielding distinct pulsed-field gel electrophoresis genotypes. Multiple sources of C. botulinum type E may be involved in the contamination of seal meat during butchering in this region, but the risk of contamination appears to be much higher from environmental sources along the shoreline of southern Ungava Bay and the sediments of the Koksoak River.     

长爪沙鼠肝细胞体外分离培养体系的建立

目的建立长爪沙鼠原代肝细胞分离培养体系。方法以雄性长爪沙鼠为供体,采用组织消化法和Seglen两步灌流法分离肝细胞,以台盼蓝染色检测细胞得率和活率,过碘酸-希夫氏反应(PAS)鉴定肝细胞,倒置显微镜观察肝细胞形态变化,并使用含有多种细胞因子的培养基维持培养。结果组织消化法和Seglen两步灌流法平均每只长爪沙鼠可分别获得肝细胞(1.33±0.34)×107个、(3.97±1.15)×107个,细胞活率分别为(29.4±6.05)%、(80.3±4.56)%,这两种方法在细胞得率及活率方面存在显著差异。肝细胞内因有大量的糖原颗粒,经PAS染色后被染成红色。结果表明肝细胞在贴壁后72 h内,肝细胞形态发生显著变化。结论采用胶原酶经肝门静脉灌流分离肝细胞是一种高效获得肝细胞的方法。各种细胞因子有利于维持肝细胞在体外的生长分化,长爪沙鼠原代肝细胞分离培养体系的建立将为肝脏相关疾病研究和防治药物的开发提供技术支持。     

杨树溃疡病生防菌株N6-34抗菌活性物质的分离纯化与结构鉴定

【背景】杨树溃疡病是一种主要由葡萄座腔菌引起的杨树枝干病害,危害严重。前期从杨树中分离到一株内生拮抗细菌N6-34,研究表明该菌株拮抗效果好,对多种植物病原菌均有较强的拮抗作用。【目的】对拮抗细菌N6-34产生的抗菌活性物质进行分离纯化,并鉴定了活性物质组分的结构。【方法】通过硫酸铵盐析、甲醇抽提、分子筛、高效液相色谱等方法分离纯化N6-34菌株的抗菌活性物质,并对其进行结构鉴定。【结果】N6-34菌株发酵液经多步分离纯化,共获得14个组分,其中有13个组分具有抗菌活性,经一级质谱分析,获得了13种抗菌活性组分的分子量;经二级质谱分析,将13种抗菌活性物质鉴定为Fengycin A或Fengycin B的同系物或同分异构体。【结论】从N6-34菌株发酵液中分离获得了13种抗菌成分,为杨树溃疡病的生物防治提供了理论依据。     

Enhancing the Detection of Giardia duodenalis Cysts in Foods by Inertial Microfluidic Separation

The sensitivity and specificity of current Giardia cyst detection methods for foods are largely determined by the effectiveness of the elution, separation, and concentration methods used. The aim of these methods is to produce a final suspension with an adequate concentration of Giardia cysts for detection and a low concentration of interfering food debris. In the present study, a microfluidic device, which makes use of inertial separation, was designed and fabricated for the separation of Giardia cysts. A cyclical pumping platform and protocol was developed to concentrate 10-ml suspensions down to less than 1 ml. Tests involving Giardia duodenalis cysts and 1.90-μm microbeads in pure suspensions demonstrated the specificity of the microfluidic chip for cysts over smaller nonspecific particles. As the suspension cycled through the chip, a large number of beads were removed (70%) and the majority of the cysts were concentrated (82%). Subsequently, the microfluidic inertial separation chip was integrated into a method for the detection of G. duodenalis cysts from lettuce samples. The method greatly reduced the concentration of background debris in the final suspensions (10-fold reduction) in comparison to that obtained by a conventional method. The method also recovered an average of 68.4% of cysts from 25-g lettuce samples and had a limit of detection (LOD) of 38 cysts. While the recovery of cysts by inertial separation was slightly lower, and the LOD slightly higher, than with the conventional method, the sample analysis time was greatly reduced, as there were far fewer background food particles interfering with the detection of cysts by immunofluorescence microscopy.