IN VITRO ANALYSIS OF τ PHOSPHORYLATION SITES AND ITS BIOLOGICAL ACTIVITY

INTRODUCTIONThemicrotubule－associatedprotein蚲ishyperphos－phorylatedandglycosylatedinAlzheimerdisease（AD），andtheseabnormalmodificationsformedthebasisofprogressivelyretrogradeneurofibrillarydegenerationseeninADbrainandtherebythedementia（１，２）．ADab－normallyphosphorylated蚲notonlyismicrotubuleas－semblyincompetent，butalsoinhibitsassemblyanddis－assemblesthepreassembledmicrotubulesinvitro（３）．Inthetangle－bearingneuronsinADbrain，thenormalcytoskeletonisdisruptedandreplacedwi…     

Apolipoprotein B polymorphism and altered apolipoprotein B concentrations in Congolese blacks

The immunoreactivity of apolipoprotein B (apo B) in plasma obtained from 238 unrelated black African male subjects from the People's Republic of Congo was analysed by non-competitive Enzyme Linked-Immunosorbent Assay (ELISA) with monoclonal BIP 45 anti-LDL antibody. The polymorphism detected by BIP 45 monoclonal antibody is identical to the Ag(c,g) polymorphism. Antibody BIP 45 distinguishes three apo B allotypes (immunophenotypes) encoded by the two allelic genes apo B Ag(c) and apo B Ag(g). Because of co-dominant transmission, genotypes may be inferred from allotypes, and it has been shown that BIP 45 binds strongly to the Ag(c) factor and only weakly to the allelic Ag(g) factor. Analysis of the Congolese plasma samples indicated that 67.65% of them bound BIP 45 with low affinity (Ag(c-,g+) genotype), 28.15% with intermediate affinity (Ag(c+,g+) genotype) and 4.20% with high affinity (Ag(c+,g-) genotype). According to the Hardy-Weinberg equilibrium, this corresponds to gene frequencies of 0.817 and 0.183 for the type Ag(g)/Ag(c) alleles, respectively. After adjustment for age and body-mass index, it was found that the Ag(c) allele decreases the apo B level by 9.62 mg/dl and that the Ag(g) allele increases apo B by 0.43 mg/dl. Therefore, as much as 4.30% of the genetic variance for apo B level could be accounted for by the Ag(c,g) gene locus.     

Perinatal lung development following maternal exposure to methylmercuric chloride

Mercury ingested from dietary sources has potent neurotoxic and teratogenic effects. Initial studies have shown that mercury may also affect fetal lung development. Since these pulmonary effects may play a role in subsequent neonatal morbidity and mortality due to compromising of the development of the lung, mercury effects in fetal and neonatal lung were investigated. Methylmercuric chloride (MMC), 1,000 ppm (15 mg/kg of body weight), was administered via an intragastric tube to timed-pregnant Swiss/Webster mice on day 9 of gestation. Lungs from fetuses on gestational day 18 and from neonates on days 1, 5, or 10 after birth were studied. Significant changes in MMC-exposed lungs compared to controls occurred at postnatal day 1. At this time, lung weight per gram body weight increased, phospholipid content per gram of lung or per microgram of DNA decreased, while DNA per gram of lung increased. Methylmercury appears to have delayed lung maturation. Cuboidal epithelial cells in alveolar tubules contained conspicuous glycogen deposits, and differentiation of alveolar type II cells was adversely affected. These results suggest that prenatal exposure to methylmercury may be detrimental to lung development, specifically to the initiation of surfactant synthesis, by delaying the normal pattern of maturation of the alveolar type II cells within the lungs. Pediatr Pulmonol. 1994; 17:11–21 . © 1994 Wiley-Liss. Inc.     

男性不育患者精浆抗弓形虫IgG抗体与精子抗体关系的研究

目的:观察男性不育患者精浆中抗弓形虫 IgG 抗体。及其与抗精子抗体(AsAb)的关系。方法:采用 ELISA 方法测定169例男性不育患者及35例正常生育男性精浆抗弓形虫 IgG 抗体和 AsAb。结果:男性不育患者精浆抗弓形虫 IgG 抗体阳性率18.35%,显著高于正常生育组的2.86%(x~2=5.26,P<0.05)OR 为7.64;男性不育组精浆 AsAb 抗体阳性率为26.63%,也显著高于正常生育组(x~2=11.96,P<0.01)。精浆抗弓形虫抗体阳性的男性不育患者精浆AsAb 的阳性率为41.94%,与精浆抗弓形虫抗体阴性组的男性不育病人精浆 AsAb 的阳性率23.19%相比较,差异具有显著性(x~2=4.55,P<0.05).OR 为2.39。结论:男性不育患者精浆抗弓形虫抗体与精浆 AsAb 的产生可能有着一定的关系。     

Only activated but not non-activated presynaptic α2-autoreceptors interfere with neighbouring presynaptic receptor mechanisms

Summary Experiments were carried out in rabbit cerebrocortical slices in order to find out whether the attenuation by presynaptic ₂-autoreceptors of effects mediated by presynaptic opioid - and adenosine A₁-receptors requires activation of the ₂-receptors. The slices were preincubated with ³H-noradrenaline and then superfused with medium containing desipramine 1 mol/l. They were stimulated electrically either with single pulses or with trains of 32 pulses at 1 Hz.The overflow of tritium elicited by a single pulse amounted to 0.21% of the tritium content of the tissue. It was Ca²⁺-dependent and tetrodotoxin-sensitive and not changed by rauwolscine 1 mol/l or yohimbine 0.3 mol/l. Ethylketocyclazocine (EK; 0.1–10 nmol/l) and R-(–)-N⁶-phenylisopropyladenosine (PIA; 1–1,000 nmol/1) potently inhibited the overflow evoked by a single pulse, and their effects were not changed by yohimbine. — The overflow of tritium elicited by trains of 32 pulses at 1 Hz amounted to 0.92% of the tritium content of the tissue and was increased approximately fourfold by yohimbine 0.3 mol/l. EK and PIA were less potent inhibitors than in the one pulse experiments. Yohimbine greatly enhanced the effects of EK and PIA. The enhancement was even more pronounced when the Ca²⁺ concentration in the medium was reduced in order to obtain a control tritium overflow similar to that evoked by 32 pulses in the absence of yohimbine.The results demonstrate that there is no ₂-adrenergic autoinhibition when noradrenaline release is elicited by a single pulse. Under these conditions, the non-activated presynaptic ₂-adrenoceptor does not interfere with presynaptic opioid - and adenosine A₁-receptor mechanisms. It is only when the autoreceptor is activated by released noradrenaline that it attenuates neighbouring presynaptic receptor mechanisms, and this attenuation is removed by ₂-adrenoceptor antagonists.Send offprint requests to N. Limberger at the above address     

Presynaptic β2-adrenoceptors on the sympathetic nerve fibres of the human saphenous vein: no evidence for involvement in adrenaline-mediated positive feedback loop regulating noradrenergic transmission

Summary Spirally cut strips of human saphenous veins preincubated with ³H-noradrenaline were superfused in the presence of corticosterone and, unless stated otherwise, of cocaine or desipramine. Tritium overflow was stimulated electrically (2 Hz). Adrenaline (in the presence of rauwolscine), isoprenaline and the preferential ₂-adrenoceptor agonist procaterol concentration-dependently increased the electrically evoked tritium overflow. Prenalterol, a -adrenoceptor agonist with moderate preference for ₁-adrenoceptors, was ineffective. The concentration-response curve of isoprenaline was shifted to the right by the nonselective -adrenoceptor antagonist propranolol and by the preferential ₂-adrenoceptor antagonist ICI 118,551, but was not affected by the ₁-selective antagonist atenolol. In experiments on strips preexposed to adrenaline 10 nmol/l (i. e. a concentration higher than that which normally occurs in vivo) for 32 min in the absence of cocaine or desipramine, the electrically evoked ³H overflow was not affected 12 and 44 min after withdrawal of adrenaline, irrespective of whether propranolol was absent or present in the superfusion fluid. — In veins incubated with ³H-adrenaline, a considerable amount of the radioactivity was accumulated. During subsequent superfusion with ³H-adrenaline-free solution, electrical stimulation induced tritium overflow in a tetrodotoxin-sensitive manner. Propranolol failed to modify the evoked tritium overflow. — It is concluded that the sympathetic nerve fibres of the human saphenous vein are endowed with facilitatory presynaptic ₂-adrenoceptors. These receptors do not seem to play a substantial role in a local adrenaline (previously taken up)-mediated positive feedback loop regulating noradrenergic transmission, at least under the present in vitro conditions.This study was supported by a grant of the Deutsche Forschungsgemeinschaft Send offprint requests to M. Göthert     

Neuropeptides: Animal behaviour and human psychopathology

Summary Animal studies have demonstrated that neuropeptides modulate nervous system functions. It has been postulated that disturbances in neuropeptide systems may be aetiological factors in psychiatric and neurological disorders. Neuropeptides related to ACTH/MSH, including ORG 2766, increase motivation and attention and facilitate recovery processes after nerve damage. These peptides may be effective during the early stage of dementia. Vasopressin and related peptides improve memory processes in animals and humans. In addition, these peptides influence social behaviour, mood and addictive behaviour. The non-opioid -type endorphins have neurolepticlike activities in animals and antipsychotic effects in a category of schizophrenic patients. Peptides related to CCK have also been found to be effective in these patients. Some neuropeptides, e.g. TRH and PLG, have been reported to exert antidepressant effects. Further research may eventually produce neuropeptides with therapeutic action in psychiatric and neurological diseases.Parts of this article were presented on the occasion of the inauguration ceremony of the Department of Psychiatry of the University of Mainz on April 2 and 3, 1987     

Uptake inhibitors do not change the effect of imidazoline α2-adrenoceptor agonists on transmitter release evoked by single pulse stimulation in mouse vas deferens

Summary The present study was undertaken to compare the presynaptic interaction of neuronal noradrenaline uptake inhibitors with imidazoline and phenylethylamine ₂adrenoceptor agonists under two different conditions: at low and high noradrenaline concentrations in the biophase.Isolated mouse vasa deferentia were stimulated with trains of 7 pulses given at 0.2 Hz and the inhibition by the ₂-adrenoceptor agonists clonidine, -methylnoradrenaline, and UK-14,304 of twitch responses was measured in the absence and in the presence of either cocaine (12 mol/l) or desipramine (40 nmol/l). The effects were determined for the first (equivalent to single pulse stimulation) and the last stimulus of each train. Both uptake inhibitors antagonized the presynaptic inhibitory effects of imidazolines (clonidine and UK-14,304) on the last twitch; the effects on the first twitch remained unchanged. In contrast, the uptake inhibitors potentiated the inhibitory effect of the phenylethylamine (-methylnoradrenaline) on both the first and the last twitches.These results support the view that the concentration of noradrenaline in the biophase plays a decisive role in the inhibition by a₂-adrenoceptor agonists of the electrically evoked release of noradrenaline. Agonists that are not substrates of neuronal uptake (i.e., clonidine, UK-14,304) become less effective when noradrenaline is present in the biophase while substrates of neuronal uptake (i. e., -methylnoradrenaline) do not. The results argue against the hypothesis that uptake inhibitors interact directly with presynaptic ₂-adrenoceptors or act at some link between uptake and receptor sites. Send offprint requests to S. Guimarães at the above address     

The effects of clonidine and yohimbine on human information processing

The effects of clonidine and yohimbine on human information processing were tested in six normal volunteers ages 18–30 years. Subjects were tested in a pre-post design with sessions conducted at weekly intervals. Three drug conditions were: Placebo (lactose), 0.2 mg clonidine, and 30 mg yohimbine. Two choice reaction time (RT) tasks were used. One was a stimulus evaluation-response selection task (SERS) that has been shown to be sensitive tod-amphetamine, methylphenidate and scopolamine. The other task was to assess stimulus pre-processing and used spatial frequency as a discriminative stimulus. The principle finding was that clonidine slowed RT; this effect was significant for both tasks. In contrast, yohimbine tended to speed RT, but the effects were significant only for the spatial frequency task on some analyses while not for others. RTs to high spatial frequency stimuli were speeded more than for low spatial frequency. The effects of these two NE drugs were compared with findings withd-amphetamine and scopolamine and interpreted within the framework of a serial information processing model proposed by Callaway (1983). Specifically, it is suggested that yohimbine and clonidine affect an early pre-processing stage.     

Drug Binding to α1-Acid Glycoprotein Studied by Circular Dichroism

The interactions of acidic and basic drugs with ₁-acid glycoprotein (₁-AGP) were investigated using circular dichroism (CD) measurements. Extrinsic Cotton effects were generated by the binding of drugs to ₁-AGP. The CD data suggested the presence of a single binding site on the ₁-AGP molecule. The induced ellipticities of the acidic drug–₁-AGP system decreased with increasing pH, while the ellipticities for the basic drugs increased with pH. The ellipticities for all drugs were reduced by the addition of fatty acids. Furthermore, the induced ellipticities decreased in the presence of cesium chloride for basic drugs bound to ₁-AGP. The extrinsic Cotton effects therefore appear to result from hydrophobic interaction with ₁-AGP for the acidic drugs and from hydrophobic and electrostatic interactions for the basic drugs.