Alzheimer Aβ Amyloid Forms an Inhibitory Neuronal Substrate

Abstract: Alzheimer's disease (AD) is identified by the accumulation of amyloid plaques, neurofibrillary degeneration, and the accompanying neuronal loss. AD amyloid assembles into compact fibrous deposits from the amyloid β(Aβ) protein, which is a proteo-lytic fragment of the membrane-associated amyloid precursor protein. To examine the effects of amyloid on neuron growth, a hybrid mouse motoneuron cell line (NSC34) exhibiting spontaneous process formation was exposed to artificial "plaques" created from aggregated synthetic Aβ peptides. These correspond to full-length Aβ residues 1–40 (Aβ1–40), an internal β-sheet region comprising residues 11–28 (Aβ11–28), and a proposed toxic fragment comprising residues 25–35 (Aβ25–35). Fibers were immobilized onto culture dishes, and addition of cells to these in vitro plaques revealed that Aβ was not a permissive substrate for cell adhesion. Neurites in close contact with these deposits displayed abnormal swelling and a tendency to avoid contact with the Aβ fibers. In contrast, Aβ did not affect the adhesion or growth of rat astrocytes, implicating a specific Aβ-neuron relationship. The inhibitory effects were also unique to Aβ as no response was observed to deposits of pancreatic islet amyloid poly-peptide fibers. Considering the importance of cell adhesion in neurite elongation and axonal guidance, the antiadhesive properties of Aβ amyloid plaques found in vivo may contribute to the neuronal loss responsible for the clinical manifestations of AD.     

底物膜技术检测精子顶体酶活性的研究

应用底物膜技术检测１３０例正常精液,精子顶体酶活性百分率的正常值下限为５７％。４５９例不孕症病人精液分析,无精症２５例,其余４３４例中７５％精子顶体酶活性正常。实验表明精子密度对数值与顶体酶活性百分率之间有正相关,ｒ＝０．８４（Ｐ＜０．０１）,回归方程为顶体酶活性百分率ｙ＝４８．４３％＋（８．９％）（ｌｏｇ精子计数）。活动精子百分率与顶体酶活性之间有密切正相关,ｒ＝０．９６７,（Ｐ＜０．０１）,顶体酶活性ｙ＝３８．６％＋０、３６ｘ％。前向活跃直线运动精子百分率与顶体酶活性之间也有密切相关．ｒ＝０．９６,（Ｐ＜０．０１）,顶体酶活性ｙ＝３４．２１％＋０．６１ｘ％。     

Plant communities on anthropogenically disturbed sites on the Chukotka Peninsula,Russia

Abstract. The vegetation of anthropogenically disturbed sites on the Chukotka Peninsula was investigated in 1986 and 1990. 102 sites had been bulldozed free of vegetation and soil between 2 and 20 yr ago and revegetated. Anthropogenic vegetation differs considerably from natural tundra. The total plant cover decreases, lichens are absent, moss composition changes, and graminoids predominate. A floristic classification was developed in order to describe the diversity of anthropogenic communities formed on these sites. Four associations were distinguished, all belonging to the alliance Poion glaucomalacanthae. An additional alliance characterized by Alopecurus alpinus is suggested for colder sites, but it has not yet been described. There is a correspondence of associations to substrate types. The association Phippsietum algidae was found only on loam substrate. The Artemisietum glomeratae and Saxifragetum punctatae are connected with rubble or gravel. The graminoid association Arctagrostietum arundinaceae is generally widespread in disturbed habitats and occurs on a variety of substrate types.     

废用条件下大鼠和达乌尔黄鼠骨骼肌氧化应激和抗氧化防御能力与肌萎缩的比较研究

有鳞类(蛇和蜥蜴)具有较发达的嗅器和犁鼻器,对其不同种类嗅觉结构的认识有助于阐明爬行动物化学感觉的进化。本文采用组织学方法比较了草原沙蜥(Phrynocephalus frontalis)、荒漠沙蜥(P. przewalskii)、密点麻蜥(Eremias multiocellata)和秦岭滑蜥(Scincella tsinlingensis)的嗅器及犁鼻器。结果发现,草原沙蜥的鼻腔较为狭长,秦岭滑蜥呈梨形,其他两种蜥蜴的鼻腔略成圆形。秦岭滑蜥的嗅上皮最厚,其次是密点麻蜥和草原沙蜥,荒漠沙蜥最薄。犁鼻器主要由犁鼻腔、犁鼻感觉上皮、犁鼻神经及蘑菇体等组成,没有腺体。草原沙蜥和荒漠沙蜥的犁鼻腔较为宽阔,密点麻蜥和秦岭滑蜥的较窄。4种蜥蜴的犁鼻感觉上皮均较嗅上皮厚,蘑菇体向后逐渐缩小至消失,犁鼻感觉上皮成闭环状,包围犁鼻腔。密点麻蜥和秦岭滑蜥的犁鼻感觉上皮位于犁鼻器的背侧,蘑菇体位于腹侧;与此不同,两种沙蜥的犁鼻感觉上皮偏向于犁鼻器的腹内侧,蘑菇体位于背外侧。密点麻蜥的犁鼻感觉上皮最厚,其次为秦岭滑蜥,两种沙蜥最薄;秦岭滑蜥犁鼻感觉上皮的感觉细胞密度最高,其次是密点麻蜥,两种沙蜥最低。这些结果提示,密点麻蜥和秦岭滑蜥对嗅觉信号的依赖和投入较两种沙蜥多;4种蜥蜴犁鼻器的结构差异间接地佐证了有鳞类犁鼻器系统发生的特异性。     

Occurrence of Verticillium fungicola var. fungicola on Agaricus bitorquis Mushroom Crops in Spain

Diseased fruit bodies of Agaricus bitorquis, with similar symptoms to those caused by dry bubble on Agaricus bisporus, were observed in some Spanish crops during summer 1999. Isolates of Verticillium fungicola from A. bitorquis and A. bisporus were submitted to different temperatures and to prochloraz–Mn sensitivity tests. All the isolates collected from A. bitorquis and A. bisporus were identified as V. fungicola var. fungicola. Artificial infections of A. bisporus and A. bitorquis with V. fungicola var. fungicola are also described in the present study. The appearance of natural infections of V. fungicola var. fungicola in A. bitorquis crops could well be due to the growing temperatures used in Spain, which are considerably below those used in other countries.     

Use of Local Raw Materials for the Production of Bacillus sphaericus Insecticide in Ghana

Locally available raw materials were used as fermentation media for the preparation of an effective bacterial insecticide of Bacillus sphaericus in Ghana. The choice of materials for media production was based on their availability, their cost and how well they supported growth and sporulation of the bacterium. The materials used were anchovy (Engraulis encrasicolus), spent grain from breweries, bambara beans (Vigna subterranea), sprout maize (Zea mays) and B. sphaericus strain IAB 881. The larvicidal activities of each final whole culture of the insecticides prepared were evaluated against third and fourth instar larvae of the mosquito species Culex quinquefasciatus. The levels of larvicidal activity exhibited by preparations using the raw materials were similar to those where the bacterium was cultured in a synthetic medium, with median lethal concentrations ranging from 0.30 10- 5 to 0.68 10-6. Cell counts were in the range 11 108 - 36 108 colony-forming units ml-1, and spore counts were between 29 107 and 61 107 ml-1.     

Microbial cultures in the utilization of cellulosic materials

This review elaborates on the most recent microbial development in saccharification of cellulose and cellulase formation. A particular highlight is a new genetic-immunochemical approach investigating the mechanism of adhesion of bacterial cellulase to cellulose during cellulose conversion. New developments and recent reviews in hemicellulose and lignin degradation are also covered.     

Citric acid production from beet molasses by cell recycle ofAspergillus niger

Summary Production of citric acid from beet molasses at a varying pH profile using cell recycle ofAspergillus niger was investigated. Best results in terms of citric acid concentration, yield, productivity and specific citric acid productivity were obtained with a substrate pH of 3.0.     

Effect of Different Isomers of Dihydroxybenzoic Acids (DBA) on the Rate of DL-DOPA Oxidation by Mushroom Tyrosinase

Dihydroxybenzoic acids (DBA), such as 3,4-DRA, 3,5-DBA, and 2,4-DBA—at all concentrations tested—inhibited the rate of DL-DOPA oxidation to dopachrome (λmax = 475 nm) by mushroom tyrosinase. 2,3-DBA and 2,5-DBA at relatively low concentration had a synergistic effect on the reaction, whereas at relatively high concentrations they inhibited the rate of DL-DOPA oxidation. The synergistic effect of 0.6-13.3 mM 2,3-DRA on the rate of DL-DOPA oxidation to dopachrome (λmax = 475 nm) was found to be due to the ability of 2,3-DBA-o-quinone (formed by the oxidation of 2,3-DBA by mushroom tyrosinase or by sodium periodate) to oxidize DL-DOPA to dopachrome (via dopaquinone) non-enzymatically. A similar explanation is likely to be valid for the synergism exerted by 2,5-DBA on the rate of DL-DOPA oxidation by mushroom tyrosinase.     

Glucose uptake of Cytophaga johnsonae studied in batch and chemostat culture

The influence of different physiological states on the glucose uptake and mineralization by Cytophaga johnsonae, a freshwater isolate, was examined in batch and chemostat cultures. At different growth rates under glucose limitation in chemostat cultures, different uptake patterns for ¹⁴C labeled glucose were observed. In batch culture and at high growth rates the glucose uptake potential showed a higher maximum velocity and a much lower substrate affinity than at lower growth rates. These findings and the results of short-term labeling patterns could be explained by two different glucose uptake mechanisms which enable the strain to grow efficiently both at high and low substrate concentrations. Substrate specificity studies showed that a structural change of the C-2 atom of the glucose molecule was tolerated by both systems. The consequences of these results for the ecophysiological classification of the Cytophaga group and for the operation of continuous cultures are discussed.