Isolation of viral coat protein mutants with altered assembly and aggregation properties

A method was developed to screen bacteria for synthesis of mutant proteins with altered assembly and solubility properties using bacteriophage MS2 coat protein as a model self-associating protein. Colonies expressing coat protein from a plasmid were covered with an agarose overlay under conditions that caused the lysis of some of the cells in each colony. The proteins thus liberated diffused through the overlay at rates depending on their molecular sizes. After transfer of the proteins to a nitrocellulose membrane, probing with coat protein-specific antiserum revealed spots whose sizes and intensities were related to the aggregation state of coat protein. The method was employed in the isolation of assembly defective mutants and to find soluble variants of an aggregation-prone coat protein mutant.     

Determination of 8-oxoguanine in human plasma and urine by high-performance liquid chromatography with electrochemical detection

A highly sensitive and selective method for determining 8-oxoguanine in plasma and urine was developed by high-performance liquid chromatography with electrochemical detection. The compound was separated by gradient elution on a C₁₈ reversed-phase column with a mobile phase of acetonitrile and 0.1 M sodium acetate, pH 5.2. 8-Hydroxy-2′-deoxyguanosine was used as internal standard. 8-Oxoguanine was detected electrochemically by setting the potential to +300 mV vs. Pd reference. The sensitivity of the assay was 22 ng/ml with a signal-to-noise ratio of 7:1. The within-day relative standard deviations for 8-oxoguanine quality control samples with concentrations of 3340, 1340 and 84 ng/ml were 3.6, 4.3 and 5.7% for plasma, and 4.1, 4.6 and 6.2% for urine, respectively. The day-to-day relative standard deviations for the same samples were 3.8, 6.8 and 7.1% for plasma, and 3.9, 7.0 and 7.9% for urine, respectively. The method is designed to study the pharmacokinetics and metabolic fate of O⁶-benzylguanine in a phase I clinical trial. Previously, O⁶-benzyl-8-oxoguanine was identified as the primary metabolite of O⁶-benzylguanine in humans. We now demonstrate that 8-oxoguanine is a further metabolite of O⁶-benzylguanine.     

A neural-network system for control of eye movements: basic mechanisms

This paper presents a neural-network-based system that can generate and control movements of the eyes. It was inspired by a number of experimental observations on the saccadic and gaze systems of monkeys and cats. Because of the generality of the approach undertaken, the system can be regarded as a demonstration of how parallel distributed processing principles, namely learning and attractor dynamics, can be integrated with experimental findings, as well as a biologically inspired controller for a dexterous robotic orientation device. The system is composed of three parts: a dynamic motor map, a push-pull circuitry, and a plant. The dynamics of the motor map is generated by a multi-layer network that was trained to compute a bidimensional temporal-spatial transformation. Simulation results indicate (1) that the system is able to reproduce some of the properties observed in the biological system at the neural and movement levels and (2) that the dynamics of the motor map remains stereotyped even when the motor map is subject to abnormal stimulation patterns. The latter result emphasizes the role of the topographic projection that connects the motor map to the push-pull circuitry in determining the features of the resulting movements.     

Mitogenomes provide new insights into the evolutionary history of Prodiamesinae (Diptera: Chironomidae)

Evolutionary analysis of Prodiamesinae has long been impeded by lack of information, and its phylogenetic relationship with Orthocladiinae remains questionable. Here, ten complete mitochondrial genomes (mitogenomes) of Orthocladiinae sensu lato were newly sequenced, including three Prodiamesinae species and seven Orthocladiinae species. Coupled with published mitogenomes, a total of 12 mitogenomes of Orthocladiinae sensu lato were selected for a comparative mitogenomic analysis and phylogenetic reconstruction. Mitogenomes of Orthocladiinae sensu lato are conserved in structure, and all genes arrange the same gene order as the ancestral insect mitogenome. Nucleotide composition is highly biased, and the control region displayed the highest A + T content. All protein-coding genes are under purifying selection, and the ATP8 evolves at the fastest rate. In addition, the mitogenomes of Orthocladiinae sensu lato are highly conserved, and they are practically useful for phylogenetic inference, suggesting a re-classification of Orthocladiinae by sinking Prodiamesinae as a subgroup of Orthocladiinae.     

Central muscarinic control of the pattern of small intestinal motility in rats

The effects of central and peripheral administration of muscarinic agonists and antagonists on small intestinal motility were examined in conscious rats chronically fitted with electrodes implanted in the duodeno-jejunal wall and a cannula in a cerebral lateral ventricle. Intracerebroventricular (i.c.v.) administration of either atropine or pirenzepine at doses from 1 to 10 micrograms, 15 min before a 3 and 6 g lab chow meal significantly reduced the duration of the postprandial disruption of the migrating myoelectric complexes (MMC). The reduction was significantly greater for atropine, a mixed M1 and M2 muscarinic receptor antagonist, than for pirenzepine, an antagonist with a high affinity for M1 receptors. At a higher dose (10 micrograms) intra peritoneal (i.p.) administration of atropine or pirenzepine did not modify the postprandial disruption of MMC. Oxotremorine (10 ng) a M2 agonist, but not McNeil A343 (5 micrograms), a selective M1 agonist, given i.c.v. in fasted rats disrupted for 1.5 h the MMC pattern. At the same doses given i.p. oxotremorine and McNeil A343 disrupted the MMC for 15 and 45 min respectively. We conclude that the postprandial changes in the small intestinal motility involve muscarinic receptors, mainly of M2 subtype, at the level of the central nervous system.     

墨红鲜花香气(头香)成分分析

利用 XAD-4憎水性吸附树脂采集墨红头香,以毛细管气相色谱双柱保留指数和 GC/MS/DS 联用方法鉴定头香的化学成份。共分离鉴定或初步鉴定了45种组份,其中含量较大的有乙酸芳樟酯(14.98%),柠檬烯(12.07%),甲基苯甲醚(9.88%),香茅醇(4.82%),乙酸巳酯(3.98%),β-石竹烯(4.55%),芳樟醇(3.18%),正巳醇(3.17%)等.     

Histochemical characterization of glycoproteins present in jejunal and colonic goblet cells of pigs on different diets

Summary We examined the glycoprotein composition of intestinal goblet cells in jejunal and colonic biopsies obtained from pigs on different diets. Paraffin sections were stained both chemically and with the following horseradishperoxidase conjugated lectins: Canavalia ensiformis (Con-A), Limulus polyphemus (LPA), Lotus tetragonolobus (LTA), Arachis hypogaea (PNA), Ricinus communis (RCA1), Glycine max (SBA) and Triticum vulgaris (WGA). Using chemical staining procedures, only small quantitative differences were noted between the two organs. With respect to lectin staining, the mucus of the jejunum was characterized by the absence of Con-A binding sites, and colonic mucus consistently exhibited an absence of SBA affinity. After dietary modifications, O-acetyl sialic acid reactivity was lowered in the jejunum but was enhanced in the colon. In the jejunum, the glycoproteins became neuraminidase susceptible, whereas the colon became characterized by the absence of neutral mucins. The affinity for the tested lectins after the different diets was variable, but the most striking effects were observed after the fibreless diet (milk alone). Our data suggest the existence of marked regional variations in goblet-cell mucus and indicate significant differences between the glycoprotein components of the jejunal and colonic mucosa. Furthermore, the biosynthesis of mucins in both regions was altered by even only short-term feeding modifications.     

Expression of vimentin and glial fibrillary acidic protein in human developing spinal cord

Summary Expression of intermediate filament proteins was studied in human developing spinal cord using immunoperoxidase and double-label immunofluorescence methods with monoclonal antibodies to vimentin and glial fibrillary acidic protein (GFAP). Vimentin was found in the processes of radial glial cells in 6-week embryos, while GFAP appeared in vimentin-positive astroglial cells at 8–10 weeks. GFAP and vimentin were present in approximately equal amounts in differentiating astrocytes in 23-week spinal cord. In 30-week fetuses, astrocytes reacted strongly for GFAP, while both the reaction intensity and the number of vimentin-positive cells fluctuated predominantly in the grey matter. No clear-cut transition from vimentin to GFAP was noticed during the development of astrocytes. The majority of ependymal cells in 23-week fetuses contained vimentin but only a few of them reacted for GFAP. The expression of vimentin continued during the whole development of the ependymal layer, in contrast to the reactivity for GFAP which disappeared between the 30th week and term.     

Influence of enkephalinase inhibitors on gastric emptying in mice depends on the nature of the meal

The effects of two enkephalinase inhibitors (thiorphan and acétorphan) and DALAMIDE on gastric emptying of fat or non-fat meals were evaluated in mice. When administered intraperitonally at low doses (0.1 and 0.2 mg/kg) 30 min prior to a fatty (milk) meal, both thiorphan and acetorphan increased significantly (P less than 0.01) gastric emptying; these effects were maximal for 0.2 and 0.1 mg/kg respectively and decreased progressively to be not significant for doses higher than 5 mg/kg for thiorphan and 0.5 mg/kg for acetorphan. Similarly DALAMIDE given IP increased significantly (P less than 0.05) gastric emptying at doses of 0.5 and 1 mg/kg while a slowing of gastric emptying was obtained for 10 times higher doses. The effects of thiorphan (0.2 mg/kg) and DALAMIDE (0.5 mg/kg) were blocked by previous administration of naloxone (0.3 mg/kg) and methyl-naloxone (0.5 mg/kg) while only naloxone (0.3 mg/kg) blocked the slowing effect of high dose of DALAMIDE. Administered prior to a non-fat meal, thiorphan (1 mg/kg) stimulated gastric emptying and inhibited it at higher dosage (10 mg/kg). Neither acetorphan nor DALAMIDE at similar dosages affected the gastric emptying of a non-fat meal and the effects of thiorphan (1 and 0.1 mg/kg) were not blocked by naloxone (0.3 mg/kg). It is concluded that enkephalinase inhibitors (thiorphan and acetorphan) administered systemically stimulate the gastric emptying of a fat meal by increasing enkephalin levels in peripheral tissues, while thiorphan exhibits non-opiate effects on gastric emptying of a non-fat meal.     

A tetrapeptide isolated from hamster embryo with central opiate properties on gastrointestinal motility but not on pain perception

The effects of centrally administered kentsin (H-Thr-Pro-Arg-Lys-OH) on intestinal motility and on pain perception were investigated in rats chronically equipped with lateral ventricle catheters. Intestinal motility was recorded electromyographically from electrodes placed on the duodeno-jejunum; analgesia was evaluated by the hot-plate and tail-flick tests. Kentsin (4.0 ug/kg), injected intracerebroventricularly (ICV) 2 hours after the beginning of a meal, restores the "fasted" i.e. the migrating myoelectric complex of intestinal motility, while a 5 times higher dose administered subcutaneously was inactive. The ICV effect of kentsin was blocked by previous ICV administration of naloxone (400 ug/kg). In contrast, kentsin administered ICV (40 ug/kg) or SC (200 ug/kg) did not affect significantly (P greater than 0.05) the time latency in the two analgesic tests during 90 minutes after its administration and did not significantly modify the analgesic effects of (D5-Ala2, Met5) enkephalinamide. We conclude that kentsin when centrally administered acts on opiate receptors to alter gastrointestinal motility but without effects on pain perception.