Lead as an inductor of some morphological and functional changes in synaptosomes from rat brain

Summary 1. The effect of lead (in vivo) on the uptake of GABA, dopamine, and histidine as a precursor of histamine in synaptosomes obtained from chronically lead-treated rats was studied.2. Lead decreased the uptake of GABA, increased the uptake of dopamine, and did not change the uptake of histidine. These effects were independent of calcium concentration.3. Lead administration to the rat changed the morphology of the synaptosomes, as manifested in the decreased number of synaptic vesicles and disturbed mitochondrial structure.4. The results suggest the existence of several mechanisms of lead toxicity on uptake, related to individual neurotransmitters, which are not necessarily connected with a Pb²⁺/Ca²⁺ interaction.     

Stimulatory Effect of Histamine on Cyclic AMP Formation in Chick Pineal Gland

Abstract: Histamine (HA) potently stimulated cyclic AMP accumulation in intact pineal glands taken from light-exposed chicks. The action of HA was stronger in the presence of forskolin and the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). The effect of HA was mimicked by HA H₁- and H₂-receptor-selective agonists in the following order of potency: HA > 4-methylhistamine (H₂) > 2-methylhistamine (H₁) > 2-thiazolylethylamine (H₁) ≫ dimaprit (H₂). The HA H₃-receptor-selective agonist (R)α-methylhistamine was poorly active. The effect of HA was antagonized by selective H₂-receptor blockers (tiotidine > oxmetidine > cimetidine = ranitidine) and was not significantly affected by the selective H₁- and H₃-receptor blockers mepyramine and thioperamide. A detailed analysis of an antagonistic action of ranitidine (versus HA) revealed a noncompetitive mode of action of the H₂ blocker. The stimulatory action of the H₁ agonist 2-thiazolylethylamine (both under basal conditions and in the presence of forskolin or IBMX) was not significantly influenced by three H₁-receptor-selective blockers (mepyramine, triprolidine, and diphenhydramine), but it was totally counteracted by ranitidine. Using accepted selective agonists and antagonists of the HA H₁, H₂, and H₃ receptor we were unable to identify clearly the receptor subtype mediating the HA action on the cyclic AMP-generating system of the chick pineal. It is suggested that the receptor under consideration may represent either an H₂-like (in terms of mammalian criteria) or avian-specific HA receptor. The data suggest that HA may be considered a modulator of the pineal activity in chicks.     

Accumulation of cesium and radiocesium in forest litter in selected regions of poland and its influence on litter-to-mushroom transfer factor

The aim of this work was to check whether the stable cesium content in forest litter affects the value of radiocesium from litter-to-mushroom transfer factorTf or not. Total cesium in litter, measured by AAS, varied from 0.1–2.7 μg/g. These data, combined with earlier results for mushrooms, showed no simple correlation forTf. More complex relationships provided very high correlation coefficients, but their validity needs further investigation.     

Polish Glomales

Spores of Acaulospora dilatata and Scutellospora dipurpurascens found in Poland are described and illustrated and their occurrence and distribution are characterized and mapped. Spores of Acaulospora dilatata from Poland do not differ from those originally described in the United States of America. The germination shield found in a number of spores is described and illustrated, and compared with that occurring in members of the genus Scutellospora. Acaulospora dilatata was found in five of the 303 soil samples taken from around the roots of Ammophila arenaria colonizing maritime sand dunes of the Sowinski National Park. Polish specimens of S. dipurpurascens are similar in size, wall structure, and reaction in Melzer's reagent to those described from the type localized in the United States of America. However, some spores from Poland have a thicker wall, greater sporogenous cells, and are somewhat darker coloured. They were recovered from 34 soils sampled from forests, gardens, sand dunes, and both cultivated and uncultivated soils. S. dipurpurascens was commonly associated with different plants of the Hel Peninsula and occurred regularly among the roots of Ammophila arenaria growing in the Slowinski National Park. Both species were found for the first time in Poland and are probably new to Europe.     

Arbuscular fungi and mycorrhizae (Glomales) of the Hel Peninsula,Poland

In the years 1985–1989, the occurrence of arbuscular fungi and mycorrhizae on the Hel Peninsula (Poland) was investigated with the help of 45 soil and root samples collected under 20 plant species of eight families. Except for Zea mays, the other plant species were from uncultivated sites. All soil samples contained spores of arbuscular fungi, of which about 45% were of the genus Glomus. Acaulospora spp. preferred members of the Cupressaceae. Spores of Gigaspora occurred rarely and only in two plant families. Glomus spp. were most frequently associated with plants of the Rosaceae, and species of Scutellospora were found at markedly higher frequencies among roots of plants of the Gramineae and Cupressaceae. A total of 29 spore-forming species and Glomus tenue (a fungus recognizable by its distinctive infections) were found. The most frequently recovered fungus, Glomus tenue, was present in roots of 56.8% of examined plants. Of the spore-forming fungi, the most frequently isolated spores were those of Scutellospora dipurpurascens, then Glomus constrictum, Acaulospora 61, and Glomus microcarpum. The overall spore density in examined samples averaged 99.8 in 100 g dry soil in the range 1 to 547, and was highest in a sample taken from around roots of Festuca arundinacea. The dominant fungi forming spores in sampled soils were Glomus constrictum, Glomus microcarpum, and Scutellospora dipurpurascens. The average species density was 3.9 in 100 g dry soil in the range 1 to 10, and was highest in Corynephorus canescens, Rosa canina, and Thuja occidentalis. Levels of colonization by arbuscular fungi ranged from 0.0 to94.0% (mean 23.3%) of the root length and were highest in Festuca arundinaceae and Zea mays.     

Direct determination of the enantiomeric purity of (R)- and (S)-2-hydroxy-4-phenylbutyric acid

The determination of enantiomeric purity of (R)- and (S)-2-hydroxy-4-phenylbutyric acid by chiral HPLC is described. Good resolution has been obtained on covalently bonded L-hydroxyproline saturated with Cu(II) ions. The method makes possible the determination of enantiomeric purity in media containing growing cells. © 1994 Wiley-Liss, Inc.     

Photoinhibition as a control on photosynthesis and production of Sphagnum mosses

The effect of high light intensity on photosynthesis and growth of Sphagnum moss species from Alaskan arctic tundra was studied under field and laboratory conditions. Field experiments consisted of experimental shading of mosses at sites normally exposed to full ambient irradiance, and removal of the vascular plant canopy from above mosses in tundra water track habitats. Moss growth was then monitored in the experimental plots and in adjacent control areas for 50 days from late June to early August 1988. In shaded plots total moss growth was 2–3 times higher than that measured in control plots, while significant reductions in moss growth were found in canopy removal plots. The possibility that photoinhibition of photosynthesis might occur under high-light conditions and affect growth was studied under controlled laboratory conditions with mosses collected from the arctic study site, as well as from a temperate location in the Sierra Nevada, California. After 2 days of high-light treatment (800 mol photons m^–2 s^–1) in a controlled environmental chamber, moss photosynthetic capacity was significantly lowered in both arctic and temperate samples, and did not recover during the 14-day experimental period. The observed decrease in photosynthetic capacity was correlated (r ²=0.735, P<0.001) with a decrease in the ratio of variable to maximum chlorophyll fluorescence (F _v/F _m) in arctic and temperate mosses. This relationship indicates photoinhibition of photosynthesis in both arctic and temperate mosses at even moderately high light intensities. It is suggested that susceptibility to photoinhibition and failure to photoacclimate to higher light intensities in Sphagnum spp. may be related to low tissue nitrogen levels in these exclusively ombrotrophic plants. Photoinhibition of photosynthesis leading to lowered annual carbon gain in Sphagnum mosses may be an important factor affecting CO₂ flux at the ecosystem level, given the abundance of these plants in Alaskan tussock tundra.     

Enhancement of symbiotic nitrogen fixation by vitamin-secreting fluorescent Pseudomonas

Fluorescent Pseudomonas sp. strain 267 promotes growth of nodulated clover plants under gnotobiotic conditions. In the growth conditions (60 M FeCl₃), the production of siderophores of the pseudobactin-pyoverdin group was repressed. Plant growth enhancement results from secretion of B vitamins by Pseudomonas sp. strain 267. This was proven by stimulation of clover growth by naturally auxotrophic strains of Rhizobium leguminosarum bv. trifolii and marker strains E. coli thi^- and R. meliloti pan^- in the presence of the supernatant of Pseudomonas sp. strain 267. The addition of vitamins to the plant medium increased symbiotic nitrogen fixation by the clover plants.     

Phytate dephosphorylation by free and immobilized cells ofSaccharomyces cerevisiae

Summary Saccharomyces cerevisiae in the form of baker's yeast, cells cultivated on a yeast extract-peptone-glucose medium, as well as cells immobilized in 18% (w/v) polyacrylamide gel showed the ability to hydrolyze 1.727 mM sodium phytate solution at 45°C, pH 4.6, in a stirred tank reactor. Seventy percent yield of dephosphorylation was observed after 2 h using a baker's yeast concentration of 5.8 g dry matter per 100 ml. Hydrolytic activity at 1.8–2.0 M Pi min^–1 was observed between 1st and 3rd h of the reaction in cells cultured 24 or 48 h. No inhibition by the substrate was found at sodium phytate concentrations of 0.587–1.727 mM. After 1.5 h of hydrolysis a single, well distinguished peak ofmyo-inositol-triphosphate was the main product found. By means of immobilization the stability of the biocatalyst was enhanced 3.3-fold and reached its half-life at 64 ninety-minute runs.     

The ant Lasius niger shows no relationship between task efficiency and body size variation among workers

In ants, workers of different sizes may perform various tasks, even in so-called monomorphic species with relatively low body size variation. However, it is unclear if the body size diversity of monomorphic workers correlates with task efficiency, especially in stressful contingencies. Here we tested if the body size variation of workers corresponds with its efficiency in transferring pupae. Transferring brood is a pre-set behavioral response to stress, e.g. suboptimal temperature. Here we applied a laboratory experiment simulating nest damage. The study was performed on the common garden ant (Lasius niger (Linnaeus, 1758)) – a species with no distinct worker subcastes. The efficiency of workers was measured as the latency of transferring pupae from a lit part of the experimental colony to a darkened part, while the body size diversity was expressed as the within-colony coefficient of variation in head width. We did not find any significant correlation between efficiency and body size variation. Summarizing the existing studies and the present results, we propose the hypothesis that the body size diversity of L. niger may have implications for workers’ division of labor but not for their task efficiency in a stressful contingency.