The effect of lake restoration measures on the physical,chemical and phytoplankton variables of Lake Bled

Monthly changes of physical, chemical and biological variables due a combination of artificial inflow of clean water, removal of hypolimnetic water, and diversion of sewage were studied in Lake Bled from December 1980 to December 1982.During the winter period 1981/82 the species composition of the phytoplankton changed. New species replaced those observed in previous years. We conclude that the combined effect of these three lake restoration measures was responsible for the sudden disappearance ofOscillatoria rubescens D.C. A marked decrease in some nutrients and an increase in temperature and oxygen concentration also occurred.     

The influence of dolichol, dolichol esters, and dolichyl phosphate on phospholipid polymorphism and fluidity in model membranes

The effect of dolichols, polyprenols, dolichol esterified with fatty acids, and dolichyl phosphate on the structure and fluidity of model membranes was studied using 31P NMR, small-angle x-ray scattering, differential scanning calorimetry, and freeze-fracture electron microscopy. These studies suggest that dolichol and dolichol derivatives destabilize unsaturated phosphatidylethanolamine containing bilayer structures and promote hexagonal II phase formation; high concentrations of dolichol induce lipid structures characterized by "isotropic" 31P NMR and particulate fracture faces; dolichol, contrary to cholesterol, has no effect on the thermotropic behavior of membranes consisting of phosphatidylcholine, while dolichyl-P incorporation abolishes the transition from the gel to liquid crystalline phase in 1,2-dimyristoyl-sn-glycero-3-phosphocholine; both dolichol and dolichyl-P increase the fatty acid fluidity in phosphatidylethanolamine mixtures; the effect of dolichol on bilayer structure and fluidity is more pronounced with increasing number of isoprene residues; dolichol esters are only soluble to a limited extent in the bilayer and segregates into domains at low concentrations; the results are consistent with a localization of dolichyl-P in which the phosphate group is oriented to the water interphase. The induction of hexagonal II phase by dolichyl-P may elicit the transmembrane movement of glycosylated lipid intermediate.     

The carbohydrates of secretory granules and the glycocalyx in developing mucoid cells

Summary Complex carbohydrates in secretory granules and at the apical cell surface of mouse gastric mucoid cells were studied during embryogenesis and in the early postnatal period by various cytochemical methods; the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) and tannic acid-uranyl acetate (TA-UA) procedures made neutral mucosubstances (NMS) visible, whereas the hexose residues of glycoconjugates were identified using WGA-, RCA II- and ConA-ferritin. The glycocalyx was stained with ruthenium red (RR). During differentiation of the embryonic mucoid cells the number of secretory granules increased in parallel to the increase in their carbohydrate component. NMS-stainable parts in secretory granules also had binding sites for the conjugates RCA II- and WGA-ferritin, but the binding of ConA could not be identified. The increasing quantity of NMS in secretory granules was correlated with the increased amount of PA-TCH-SP and TA-UA positive substances in the apical glycocalyx only in 14- and 18-day-old embryos. The observed uniform affinity for RR and lectin conjugates in all analysed developmental stages remains to be explained.     

Effects of short-term and prolonged aerogenic hypoxia on gamma-glutamyl transpeptidase activity in the brain,liver, and biological fluids of young rats

Posthypoxic fluctuations in the levels of two excitatory amino acids, glutamate and aspartate, may be related to changes in mechanisms(s) which are responsible for their reuptake. As gamma-glutamyl transpeptidase (GGT) plays a role in mediating the uptake of glutamate and aspartate into various compartments of the brain, we studied changes in the activity of this enzyme in main regions of the brain in young and adult rats. We found a posthypoxic increase in bound GGT activity in some brain regions of 18-day-old animals after acute exposure, but no changes were observed after prolonged altitude hypoxia, with the exception of a decrease in cortical GGT activity. In contrast, acute hypoxia decreased GGT activity in the cortical capillaries to 59%, but prolonged hypoxic exposure was ineffective. However, the activity of soluble GGT in the cerebrospinal fluid of both groups of rats was several-times elevated in comparison with controls. At the same time, bound GGT activity was increased in the liver after acute or prolonged altitude hypoxia. The soluble GGT activity in plasma was only increased after prolonged exposure. Ninety days after prolonged hypoxic exposure the bound GGT activity was reduced in all brain regions to about 60–70% of controls (significantly higher in females than in males) as long-term developmental sequel from early postnatal hypoxia.     

翅果油树根瘤超微结构及其内生菌的观察

作者用光学显微镜,透射电镜和扫描电镜对翅果油树(Eldaeagnus mollis D.)根瘤侵染细胞的超微结构及其内生菌的形态进行了观察研究。翅果油树根瘤中的内生菌具有五种不同的发育形态:菌丝、固氮泡囊、孢囊、孢囊孢子和拟类菌体。内生菌的这些不同形态以及它们在共生固氮中的作用,本文也作了讨论。     

Observations sur la végétation nitrophile de lisière dans les Marches (Italie Centrale)

A survey of the nitrophilous fringe communities of the region Marche (Central Italy) allows the individualization of five associations well characterized floristically and ecologically. These are:Urtico-Aegopodietum, Anthriscetum sylvestris, Chaerophylletum aurei, Alliario-Chaerophylletum temuli, andAnthriscetum nemorosae. The first three associations are ranged, from the phytosociological point of view, in the allianceAegopodion podagrariae, while the last two belong to the allianceGalio-Alliarion.     

柱孢鱼腥藻的铁蛋白与棕色固氮菌的钼铁蛋白的交叉互补作用

纯化的柱孢鱼腥藻铁蛋白能够与棕色固氮菌的钼铁蛋白有效地交叉反应,展现较高的活性。此异源交叉反应的乙炔还原比活及放氢比活,分别是蓝藻同源互补比活的83.8及66.7％。比较藻铁蛋白与菌钼铁蛋白异源交叉反应及藻固氮酶组分之间的同源反应的动力学特点时发现,铁蛋白对钼铁蛋白的最佳克分子比数前者(异源交叉反应)较后者(藻同源反应)为高,前者为5,后者为1;但反应的时间进程两者差别不大。     

The effect of glucose on cellobiose uptake and β-D-glucosidase activity inStreptomyces granaticolor

Glucose inhibits the inducible synthesis of β-D-glucosidase inStreptomyces granaticolor. Neither cAMP nor cGMP influence the inhibitory effect of glucose. Glucose also inhibits the inducible synthesis of the cellobiose uptake system but has no effect on its activity. This may be the mechanism underlying glucose inhibition of induction of β-D-glucosidase inS.granaticolor.     

Sugar cane bagasse as a possible source of fermentable carbohydrates. I. Characterization of bagasse with regard to monosaccharide, hemicellulose, and amino acid composition

Individual monosaccharides present in bagasse hemicellulose were determined using HPLC and other chromatographic procedures. The presence of higher oligomers of the monosaccharides could also be determined. No single procedure can separate and identify all the naturally occurring monosaccharides. The pentosan fraction of bagasse wa successfully hydrolyzed and extracted with 5% (m/v)HCl, and the rate of release of individual monosaccharides was determined. Xylose was the main component in the hydrolyzates, while glucose, arabinose, and galactose present in the side chains of the pentosans were initially released at a fast rate. This treatment resulted in obtaining 229 mg/g xylose (85% of theoretical maximum) and 44 mg/g glucose from bagasse. Only arabinose (2.8 mg/g) and galactose (0.75 mg/g) was also present in detectable quantities. A total of 309 mg monosaccharides were obtained from 1 g of bagasse by this treatment. The results indicated that hydrolysis conditions for specific plant materials depend on the composition of the specific material being utilized. A part of the pentosan fraction (77.1%) was hydrolyzed at a high rate, while 22.9% was more stable and hydrolyzed more slowly. Although 39.8% dry bagasse could be obtained in solution by treatment with dilute alkali, only about 72% of the available hemicelluloses could be extracted in this way if the bagasse was not delignified beforehand. Amino acids and peptides or proteins were also extracted to very much the same with the alkali.