Neutralizing effect of zinc oxide on dehydroabietic acid-induced toxicity on human polymorphonuclear leukocytes

The cytotoxic effect of dehydroabietic acid (DHAA), a resin acid found in rosin, was studied on human polymorphonuclear leukocytes using leakage of 51Cr from prelabeled cells, supravital staining, and transmission electron microscopy. DHAA caused a strong dose-related release of 51Cr, a high uptake of trypan blue, and total cell necrosis, as seen in transmission electron microscopy. Albumin slightly reduced the toxic effects, whereas the addition of zinc in various forms strongly inhibited these toxic effects of DHAA in the concentration range of 10-500 micrograms/mL. In the presence of albumin, zinc oxide as a suspension inhibited the damage of the cell membranes more than a filtrate of zinc oxide, indicating a subsequent slow release of zinc from the zinc oxide.     

Metabolism of a subtropical Brazilian lagoon

Total community, planktonic and benthic metabolisms were measured by using the carbon dioxide production and consumption, the diurnal curve' method and the in situ bottle incubation technique over an annual cycle in two sublagoons of the Saquarema Lagoon, Brazil. Metabolic rates of the phytoplankton-based lagoon were characterized by considerable daytime and daily variability in production and respiration, by a seasonal shift between net autotrophy and heterotrophy and by an annual balance of production (P = 105 ± 65 mmoles/m²/dayn = 25) and respiration (R = 102 ± 50 mmoles/m²/dayn = 25). Total community metabolism was similar throughout the lagoon, but phytoplankton assimilation rates and benthic respiration showed spatial differences. Bottle incubations compared to total community free water respiration suggested that the pelagic community was 2–5 times more active than the benthos     

Modelling of formation processes of inclusion complexes of coumarin laser dyes and β-cyclodextrin by the MM2 force field method. I. 7-Amino-4-methylcoumarins

In order to improve the generating and photochemical properties of coumarin laser dyes, the following active media were synthesized: inclusion complexes of -cyclodextrin (-CD) and 7-amino-4-methylcoumarins (COU1, COU102, COU120). Complex formation processes were studied, and the structure of the inclusion complexes was estimated using the method of MM2 molecular mechanics. The data obtained suggest the reasons underlying the complex structure effects on their spectral, luminescent and generating characteristics.     

An expression vector inhibits gene expression in Xenopus embryos by antisense RNA

Summary An expression vector was constructed containing the entire bovine papilloma virus (BPV-1) genome and part of the a-actin gene of Xenopus laevis cloned in the antisense orientation into the neomycin resistance gene under the control of the herpes simplex virus (HSV) thymidine kinase (TK) promoter. When this vector is microinjected into X. laevis embryos it replicates extrachromosomally, at least up to the tadpole stage, and a fusion RNA is synthesized after the mid blastula transition (MBT). The expression of the antisense gene results in a morphological abnormality of somites demonstrating that antisense RNA generated by an episomal replicating expression vector can inhibit the expression of a selected gene during early embryogenesis of X. laevis.     

用TOPSIS方法评价黄土丘陵区草场质量的研究

一、自然概况黄土高原位于我国西北部,西起青海日月山,东抵山西太行山,北至晋陕长城,南达甘陕秦岭,构成一个独具特色的、比较完整的自然区域,其地理范围大致是北纬34°—41°,东经103°—113°之间。高原到处有起伏的黄     

The acetycholinesterase gene ofAnopheles stephensi

1. The acetylcholinesterase (AChE) gene from the important malaria vector Anopheles stephensi has been isolated by homology to the Drosophila acetylcholinesterase gene. 2. The complete sequence and intron-exon organization has been determined. The encoded protein has 69% identity to Drosophila AChE and 38 and 36% identity to Torpedo AChE and human butyrylcholinesterase, respectively.     

Brain injury: New insights into neurotransmitter and receptor mechanisms

The studies reviewed here represent a continuing search for mechanisms which play a role in neurological disturbances resulting from brain injury. Focal cortical freezing lesions in rats were shown to cause a widespread decrease in local cerebral glucose utilization (LCGU) in cortical areas of the lesioned hemisphere and this was interpreted as reflecting a depression of cortical activity. Such an interpretation was supported by the finding that in lesioned brain reduction of cerebral metabolism by pentobarbital and isoflurane was limited by the metabolic depression that has already occurred as a result of injury and by the demonstration that the energy status and substrate (glucose) supply in the cortical areas in the injured brain have not been compromised at the time when LCGU was decreased. Both the serotonergic and the noradrenergic neurotransmitter systems were implicated in functional alterations associated with injury. Cortical serotonin (5-HT) metabolism was increased throughout the lesioned hemisphere and complete inhibition of 5-HT synthesis withp-chlorophenylalanine ameliorated the decrease in cortical LCGU, interpreted as reflecting cortical functional depression. Cortical norepinephrine metabolism was bilaterally increased in focally injured brain, while prazosin, a selective ₁-noradrenergic receptor blocker, normalized cortical LCGU in the lesioned hemisphere. Low-affinity in vivo binding of [¹²⁵I]HEAT, another selective ₁-receptor ligand, was specifically increased in cortical areas of the lesioned hemisphere at the time of the greatest depression in LCGU, suggesting that ₁-adrenoreceptors may be of functional importance in injured brain. The general conclusion from this series of studies on mechanisms underlying functional disturbances in injured brain is that both the serotonergic and the noradrenergic neurotransmitter systems are involved in the widespread cortical depression which develops with time as a consequence of a focal lesion. The data are compatible with the inhibitory effects of NE and 5-HT in the cortex and with the hypothesis that these two transmitter systems affect cortical information processing.     

A bioluminescent assay for the determination of phosphoenolpyruvate carboxykinase activity in nanogram-sized tissue samples

A highly specific and sensitive assay for the determination of phosphoenolpyruvate carboxykinase (PEPCK) in nanogram-sized tissue samples is described. This test system is based on the stoichiometric transformation of phosphoenolpyruvate into ATP. In a subsequent step ATP is quantified by bioluminescent techniques. The applicability of this assay system is shown by measurements in liver samples with normal and high PEPCK activity levels.     

The genetics and expression of an esterase locus inAnopheles gambiae

The main polymorphic system of esterase isoenzymes in adults of the G3 laboratory strain ofAnopheles gambiae consists of two to five major bands of activity per individual. The bands are designated 5S, 5F, 13, 14, and 15. In genetic crosses, the genes which coded for the bands assorted as three codominant alleles, Est A, Est B, and Est C, at a single autosomal locus. Homozygotes for the Est C allele were significantly underrepresented among backcross progeny. The developmental pattern of esterase expression was examined. Esterase gene expression in embryos was first detectable between 2 and 12 hr after oviposition. The initiation or termination of expression of some of the bands corresponded to boundaries between developmental stages. Most of the esterase fractions were not specifically localized within the tissues tested, with the exception of a series of bands which were restricted largely to adult male testes.