Untersuchungen Über faktoren,die sich bei folgekultivierung der pflanzen geltend machen

V práci byla sledována mo?nost allelopatického ovlivňování následných rostlin p?edplodinami p?i kultivaoi v odstupňovaných ?asových intervalech po sobě v té?e zemině u tě chto kombinací: mák — cukrovka, ho??ice — je?men, konopí — ?ito, cibule — ?epka. Pokusy byly prováděny v kvítiná?ích s kompostovou zeminou, umístěných během pokusu na zahradě a zapu? těných do p?dy. Byl sledován r?st p?edplodin a následných rostlin v po?áte?ních fá zích r?stu. P?ed vysetím následných rostlin byla stanovena u odebraných vzork? zemin intensita respirace, okam?itá vlhkost a obsah fyziologicky p?ístupného dusíku, fosforu a draslíku. Ve v?ech zkou?ených kombinacích byly následné rostliny ovlivněny kultivací p?edplodiny a následným ulo?ením zeminy. Změny r?stu následných rostlin ?áste? ně korelovaly s obsahem fyziologicky p?ístupného dusíku v zemině. Podle jejich charakteru v?ak bylo té? patrno, ?e se na nich podílely i allelopatické faktory. Zna?ně inhibi?ně p?sobil mák na cukrovku, mé ně inhibi?ně p?sobila ho??ice na je?men a cibule na ?epku. ??inek konopí na ?ito byl promě nný s dobou ulo?ení zeminy. Změny v obsahu fyziologicky p?ístupného dusíku, fosforu a draslíku v pokusné zemině neodpovídaly . mno?ství narostlé p?edplodiny, co? bylo podmíněno pou?itou kultiva?ní metodikou. Poměrně rychlé doplňování p?edplodinou vy?erpaných dusi?nan? v pokusné zemině s dobou jejího ulo?ení bylo pravděpodobně podmíněno nitrifikacními procesy. Podle stanovených změn intensity respirace pokusné zeminy se na allelopatickém ovlivnění mohla podílet i pudní mikroflora.     

Zooplankton decline in the Černé Lake (Šumava Mountains,Bohemia) as reflected in the stratification of cladoceran remains in the sediment

Stratigraphy of cladoceran remains in the upper 18 cm of a sediment core from the Lake Černé was studied. The successive disappearance of Bosmina longispina, Daphnia longispina and Ceriodaphnia quadrangula from the upper layers of the sediment corresponds with our knowledge concerning the disappearance of these species from the open water.     

Partial restoration of impaired alpha1-adrenergic responsiveness in parotid cells of aged rats by S-adenosylmethionine treatment

The age related decrease in alpha₁-adrenergic stimulated inositol 1,4,5 trisphosphate (IP₃) production in parotid cells of aged rats can be partially restored by treatment with S-adenosylmethionine (SAM). This effect is completely blocked by S-adenosyl homocysteine (SAH) and occurs in association with an increase in the conversion of phosphatidylethanolamine to phosphatidylcholine and a decrease in membrane viscosity. In contrast, SAM treatment actually inhibits stimulated IP₃ production in cells of young rats. The membrane viscosity of these cells is lower than that of those from aged rats. Although conversion of phosphatidylethanolamine to phosphatidylcholine is enhanced, no further decrease in membrane viscosity is elicited in young cell preparations. These findings suggest that age changes in the membrane environment may result in impaired alpha₁-adrenergic signal transduction and that such alterations may be at least partially reversible by SAM treatment.     

Enhancement of human immunodeficiency virus type 1 envelope-mediated fusion by a CD4-gp120 complex-specific monoclonal antibody.

The entry of human immunodeficiency virus type 1 (HIV-1) into cells is initiated by binding of the viral glycoprotein gp120-gp41 to its cellular receptor CD4. The gp120-CD4 complex formed at the cell surface undergoes conformational changes that may allow its association with an additional membrane component(s) and the eventual formation of the fusion complex. These conformational rearrangements are accompanied by immunological changes manifested by altered reactivity with monoclonal antibodies specific for the individual components and presentation of new epitopes unique to the postbinding complex. In order to analyze the structure and function of the gp120-CD4 complex, monoclonal antibodies were generated from splenocytes of BALB/c mice immunized with soluble CD4-gp120 (IIIB) molecules (J. M. Gershoni, G. Denisova, D. Raviv, N. I. Smorodinsky, and D. Buyaner, FASEB J. 7:1185-1187 1993). One of those monoclonal antibodies, CG10, was found to be strictly complex specific. Here we demonstrate that this monoclonal antibody can significantly enhance the fusion of CD4+ cells with effector cells expressing multiple HIV-1 envelopes. Both T-cell-line-tropic and macrophage-tropic envelope-mediated cell fusion were enhanced, albeit at different optimal doses. Furthermore, infection of HeLa CD4+ (MAGI) cells by HIV-1 LAI, ELI1, and ELI2 strains was increased two- to fourfold in the presence of CG10 monoclonal antibodies, suggesting an effect on viral entry. These findings indicate the existence of a novel, conserved CD4-gp120 intermediate structure that plays an important role in HIV-1 cell fusion.     

Chromosomal and histological changes in the reproductive organs of infertile men

Summary The chromosomal changes in the process of spermatogenesis in 27 infertile men have been examined. Normal chromosomal meiotic activity was found in 44% of cases, various chromosomal anomalies were seen in 18%, and no cells in meiosis were detected in 37% of cases.     

Impact of fishery management on Cladoceran populations

Zooplankton of the fish pond reveals a two-year periodicity, which is induced by the two-year cycle of fishery management. In the first year of each cycle, the biomass of large cladocerans prevailed — mainly adult specimens of the species Daphnia pulicaria Forbes, which were absent in the second year. The species Daphnia galeata Sars was present in both years, however, it is more numerous in the second year. The fraction of small zooplankton (rotifers, nauplii, Bosmina, newborn Daphnia) was abundant in the second years, but scarce in the first years, respectively.     

Fatty acid composition of phospholipids of myelin and synaptosomal proteolipid complexes from vertebrate brain.

1. Fatty acid composition of five main phospholipids of vertebrate brain myelin and synaptosomal proteolipids and membranes was studied. 2. Higher content of monoenoic and lower content of saturated and polyenoic fatty acids was found to be characteristic of phospholipids from myelin and myelin proteolipids as compared to phospholipids from synaptosomal proteolipids and membranes of vertebrates (from fishes to mammalians). Fatty acid composition of phospholipids of proteolipid complexes and of the membranes, from which they were isolated, were found to be similar in various species studied. 3. Microviscosity was found to be higher in myelin as compared to synaptosomal membranes of frog Rana temporaria and in rabbit Lepus cuniculus. It appears to be due to the difference in proteolipid content and in lipid composition of myelin and synaptosomal membranes.     

13/14 translocation in a man with reproductive failure

Summary An inherited (maternal origin) 13/14 translocation with the nucleolus organizer regions eliminated and one centromere was found in an oligospermic man whose wife had had two spontaneous abortions. Meiotic studies revealed all stages of spermatogenesis with a trivalent configuration in diakinesis. Possible reasons for his subfertility and his mother's normal fertility are discussed.