The effects of guanine and cytosine variation on dinucleotide frequency and amino acid composition in the human genome

Summary One hundred twelve human DNA sequences were analyzed with respect to dinucleotide frequency and amino acid composition. The variation in guanine and cytosine (G+C) content revealed: (1) at 2–3 and 3-1 doublet positions CG discrimination is attenuated at high G+C, but TA disfavor is enhanced, and (2) several amino acids are subject to G+C change. These findings have been reported in part for collections of sequences from various species. The present study confirms that in a single organism-the human-the G+C effects do exist. Aspects of the argument that connects G+C with protein thermal stability are also discussed.     

[3H]Imipramine Binding of Protein Nature in Human Platelets: Inhibition by 5-Hydroxytryptamine and 5-Hydroxytryptamine Uptake Inhibitors

Abstract: The nature of [³H]imipramine binding to human platelets was investigated. Desipramine and 5-hydroxytryptamine (5-HT) displaced the same amount of binding and the binding was sensitive to protease treatment. The nature of pharmacological inhibition of [³H]imipramine binding was investigated in saturation experiments. Increases in K d without changes in B _max were noted with the addition of 5-HT, desipramine, norzimeldine, or 5-methoxytryptoline. Reductions in B _max without alterations in K _D were obtained when citalopram or clomipramine was added. It is concluded that the [³H]imipramine binding site in human platelets is of protein nature and that this binding site contains the substrate recognition site for 5-HT uptake. In addition, [³H]imipramine and other 5-HT uptake inhibitors have bonds to other parts of the 5-HT uptake carrier or to the surrounding lipid membrane. This additional binding outside the substrate recognition site is not one single site but most likely represents sites that are specific for the chemical structure of each uptake inhibitor, respectively.     

Autoradiographic Analysis of [3H]Imipramine Binding in the Human Brain Postmortem: Effects of Age and Alcohol

In vitro quantitative autoradiography of high-affinity [3H]imipramine binding sites was performed on 16 human brains postmortem. The densities of binding sites were highest in the hypothalamus. Next, in descending order, were the basal and lateral nuclei of the amygdala; substantia innominata; insular cortex; the central nucleus of the amygdala; the anterior nucleus of the thalamus; the head of the caudate nucleus; portions of the frontal, parietal, and temporal cortex; claustrum; the granular layer of the dentate gyrus; substantia nigra; the pyramidal layer of CA fields; globus pallidus; red nucleus; and white matter. Imipramine binding was found to increase with age in a region-specific manner. The presence of alcohol had a similar effect, which was most pronounced in the hippocampus. Sex and time from death to autopsy did not affect imipramine binding, in our sample.     

Extracellular Amino Acid Concentrations in the Dorsal Spinal Cord of Freely Moving Rats Following Veratridine and Nociceptive Stimulation

In vivo microdialysis was used to sample extracellular concentrations of amino acids in the dorsal lumbar spinal cord of freely moving rats. Changes in the extracellular concentrations of amino acids were measured in response to infusion of veratridine (180 microM), a sodium channel activator, as well as during acute noxious stimulation by an injection of 5% formalin into the metatarsal region of the hindleg. Veratridine produced a tetrodotoxin (TTX)-sensitive increase in the extracellular concentration of Glu. Concentrations of Asp, taurine, Ala, Asn, and Gly were not significantly elevated following veratridine stimulation. Intradermal injection of formalin produced a TTX-sensitive increase in Asp concentration and a non-TTX-sensitive increase in Glu concentration. These data support the hypothesis that Glu and Asp are dorsal horn neurotransmitters involved in nociception.     

Neuropathy Target Esterase: Rates of Turnover In Vivo Following Covalent Inhibition with Phenyl Di-n-Pentylphosphinate

Phenyl di-n-pentylphosphinate is a reasonably stable easily synthesized inhibitor of neuropathy target esterase (NTE) with low anticholinesterase activity. Like phenylmethylsulphonyl fluoride it protects hens against neuropathic effects of compounds such as diisopropylphosphorofluoridate. At intervals up to 15 days after dosing hens (10 mg/kg s.c. to inhibit 90% NTE) assays were made of catalytically active and of phosphinylated NTE in autopsy tissue. The sum of these components was always within the range of catalytic activity in undosed controls. However, the half-life of reappearance of active NTE was 2.07 days +/- 0.13 (SD, n = 6) for brain and 3.62 days +/- 0.23 (SD, n = 6) for spinal cord--shorter than after dosing with phenylmethylsulphonyl fluoride. It is proposed that: (1) The physiological turnover mechanism cannot distinguish between catalytically active and di-n-pentylphosphinylated NTE although initiation of organophosphate-induced delayed polyneuropathy might involve recognition of aged di-alkyl-phosphorylated NTE as "foreign". (2) The short half-lives indicate a slow spontaneous dephosphinylation of inhibited NTE occurs in vivo as well as de novo synthesis. The difference in half-lives for brain and spinal cord NTE may be due to different rates of synthesis de novo or (more likely) to different rates of spontaneous reactivation of the inhibited NTE in the two tissues.     

Depletion of Brain Glutathione in Preweanling Mice by L-Buthionine Sulfoximine

Previous studies indicated that DL-buthionine sulfoximine (DL-BSO), an agent that inhibits the biosynthesis of GSH in liver and other peripheral organs, fails to suppress levels of GSH in the CNS. In the current study, preweanling mice responded to repeated injections of L-BSO with marked declines (79.6-86.5%) of GSH content in brain and spinal cord. In adult mice, the same treatment schedule produced only modest declines (17.8-29.2%) of GSH content in brain and a 55.9% decline in spinal cord. Pretreatment of preweanling mice with L-BSO represents a tool for studying the role of GSH in the CNS.     

Solubilization and Characterization of Calcitonin Gene-Related Peptide Binding Site from Porcine Spinal Cord

The binding site for calcitonin gene-related peptide (CGRP) was solubilized with 3-[(3-cholamidopropyl)dimethylammonio]-1-propane sulfonate (CHAPS) in an active form from porcine spinal cord. 125I-labeled human alpha-CGRP (125I-CGRP) binding to the solubilized protein was determined by filtration using a GF/B glass filter. The maximal binding activity (approximately 60% of the crude membrane fraction) was obtained with 5 mM CHAPS. 125I-CGRP binding to the solubilized protein was of high affinity, saturability, and high specificity, having KD and Bmax values of 3.69 pM and 338 fmol/mg of protein, respectively. The binding activity was eluted in a single peak with a molecular mass of 400,000 daltons by gel filtration on TSK gel G4000SW. These results suggest that the solubilized protein may be responsible for the specific binding site.     

Structural Features of Human Monoamine Oxidase A Elucidated from cDNA and Peptide Sequences

Monoamine oxidase (MAO), an important enzyme for the degradation of amine neurotransmitters, has been implicated in neuropsychiatric illness. The amino acid sequence for one form of the enzyme, MAO-A, has been deduced from human cDNA clones and verified against proteolytic peptides. The covalent binding site for the flavin adenine dinucleotide (FAD) cofactor is near the C-terminal region. The presence of features characteristic of the ADP-binding fold suggests that the N-terminal region is also involved in the binding of FAD. These cDNAs should facilitate the study of the structure, function, and intracellular targeting of MAO, as well as the analysis of its expression in normal and pathological states.     

The effects of traditional gathering on populations of the marine gastropod Strombus luhuanus linne 1758, in southern Papua New Guinea

Summary Little is known of the response of mollusc populations to predation by humans, particularly for tropical species. In this paper, we examine the effects of human predation on populations of the gastropod Strombus luhuanus in Bootless Inlet, Papua New Guinea, by documenting both the population biology of the shellfish and the shell-gathering practices of traditional and contemporary human groups. Strombus luhuanus occurs in local colonies and individuals of each sex from different colonies differed significantly in size. Sexual maturity is reached within two years after settlement, at which time the shell length stabilises at about 35–60 mm, and the shell lip thickens. There was also significant between-colony variation in density (8.35–23.39 individuals/m²), and colonies differed in the depth range of their distributions and the frequency of human collection visits. Traditional gatherers rarely collected individuals which were buried or subtidal. Contemporary collectors used different collecting methods, and gathered subtidal populations to a depth of 2.5 m. Both traditional and contemporary collectors gathered only individuals greater than 30 mm shell length, and in the contemporary sample the probability of being gathered increased significantly with shell length. This was due to size-dependent burying, which was greatest among young juveniles and least among adults. The traditional sample contained fewer shells in the largest size category (>45 mm) and more in the smallest (<40 mm), but this difference largely represents the pooling of shells from different collecting locations rather than widespread juvenisation of colonies due to exploitation. Stromb population densities at collected sites in PNG far exceeded those in comparable uncollected sites in northeastern Australia. We conclude that S. luhuanus displays high resilience to all gathering practices used to date, as a consequence of both its size-dependent burying and partly subtidal distribution, which provide refugia from human predation.     

人胸腺上皮细胞培养及其分泌产物

本文通过降低培养基中血清含量,向RPMI 1640培养基中补加三碘甲腺原氨酸而获得一种人胸腺网状上皮细胞占优势生长的培养物。在此培养基中细胞经传代培养长达90天,仍维持正常形态特征。胸腺组织在培养14天后,新生细胞的突起形成网状结构,细胞化学检查和电镜观察表明具有丰富的分泌颗粒,囊泡及张力原纤维束和桥粒等上皮细胞特征。收集合并细胞培养液,经部分纯化后检查其生物活性,表现出具有促进玫瑰花结形成和降低胸腺细胞TdT活性的作用,说明培养细胞的分泌产物具有胸腺激素活性。根据形态学,细胞化学和生物活性检测结果,我们倾向于认为该培养物主要为网状上皮细胞。