Age-dependence of malonate-induced striatal toxicity

Malonate is an inhibitor of cellular metabolism, which, following intrastriatal injection, induces a striatal pathology similar to that seen in Huntington's disease. In two parallel studies, we have investigated the suggested relationship between the neuronal vulnerability to metabolic toxicity and the decline in metabolic function with increasing age. The first experiment investigated malonate-induced neuronal loss in animals aged from 6 weeks up to 27 months, and the second assessed the activities of two mitochondrial enzymes, succinate dehydrogenase and cytochrome oxidase (CYTOX) in animals aged 6 weeks, 3, 8 and 18 months. In the first study, male Lister-Hooded rats received intrastriatal stereotaxic injections of malonate (0.5 or 1.0 M). Animals were killed 10 days after surgery, and the brains were stained with cresyl violet and processed for NADPH-diaphorase activity and glial fibrillary-acidic-protein (GFAP) immunohistochemistry. Animals aged 6 months and older exhibited over 60% striatal neuronal loss. However, the degree of neuronal loss did not show any age-related increase in rats between 6 and 27 months of age, indicating that the extent of malonate-induced toxicity does not increase with age in animals older than 6 months. Infusion of 0.5 M malonate produced smaller lesions, which also demonstrated a consistent extent of neuronal loss from 6 months onwards. Metabolic enzyme activities were decreased in the striatum with increasing age, although this effect was only significant for CYTOX activity. Thus, the pattern of malonate-induced neuronal loss in aged animals partially reflects the changes in metabolic activity during ageing.     

Cell cycle arrest of human gingival fibroblasts and periodontal ligament cells by Actinobacillus actinomycetemcomitans: involvement of the cytolethal distending toxin

The cytolethal distending toxin (Cdt) is produced by several Gram-negative bacterial species and causes growth arrest and morphological alterations in mammalian cells. Actinobacillus actinomycetemcomitans, which is involved in the pathogenesis of localized aggressive periodontitis, also produces a Cdt that affects periodontal connective tissue cells. The aim of this study was to investigate in which phase of the cell cycle these cells are arrested and enlarged when challenged with A. actinomycetemcomitans, and to evaluate the involvement of its Cdt. Human gingival fibroblasts and periodontal ligament cells were challenged with A. actinomycetemcomitans extract, or with purified Cdt, and cell cycle analysis was performed by propidium iodide staining and flow cytometry. Cells exposed to an A. actinomycetemcomitans wild-type strain, or to purified Cdt, were arrested in both G1 and G2/M phases, and appeared enlarged compared to the corresponding controls. The cellular enlargement occurred in both G1 and G2/M arrested cells. In contrast, cells exposed to an A. actinomycetemcomitans cdt-knockout mutant strain showed cell cycle phase distribution and size similar to the controls. In conclusion, A. actinomycetemcomitans causes a combined G1 and G2/M growth arrest and enlargement in periodontal connective tissue cells, which is attributed to its Cdt.     

Rapid detection of Clostridium difficile toxin A in stool specimens

Objective: To evaluate a rapid (15-min) enzyme immunoassay in the format of an individual cassette (ImmunoCard toxin A, Meridian, BMD, Marne-la-Vallée, France) for the detection of Clostridium difficile toxin A in stool specimens.
Methods: We compared this new test with the cytotoxicity assay using MRC-5 cells, the ToxA test (TechLab, BioWhittaker, Fontenay-sous-bois, France) and toxigenic culture for the diagnosis of C. difficile -associated diseases (CDAD). A total of 236 stool specimens collected from 220 patients was simultaneously tested with the four methods. Discordant results were resolved by reviewing patients' clinical records.
Results: The prevalence of CDAD was 13.9%. Test sensitivities and specificities were 100% and 99% respectively for the cytotoxicity assay, 87.5% and 100% for ImmunoCard toxin A, 77.4% and 100% for the ToxA test and 100% and 98% for toxigenic culture.
Conclusions: The ImmunoCard Toxin A is a very rapid, individual and easy-to-perform test for the diagnosis of CDAD. It provides same-day results and may be useful for both guiding appropriate treatment and controlling nosocomial spread of C. difficile.     

Does pertussis infection induce manifestation of allergy?

Summary To evaluate whether pertussis induces the development of allergy, a prospective study was performed in 25 children aged 0.8–12.2 years. The patients underwent allergy diagnostics during pertussis infection and at a follow-up visit 8–14 months later. Diagnostic criteria included the medical history of the patients and their families, a modified skin prick test, measurement of serum IgE and radio-allergosorbent test screening for specific sensitizations. At the time of pertussis, serum IgE concentration in the study group was 62+ 30 kU/ml. At the follow-up visit, there was a significant increase in serum IgE to 137 ± 51 kU/ml, which was also significantly higher than IgE in an age-matched control group. Children at a significantly higher risk for developing IgE increase or new allergic sensitizations were those with a family history of allergy or potentially allergic disease in their personal history. Our results indicate that pertussis may induce IgE production in affected children.Abbreviation SPT skin prick test Dedicated to Prof. Dr. N. Zöllner on the occasion of his 70th birthday     

Effects of luminal stimuli on polyamine metabolism in the small intestine of the rat: the role of enteric nerves

The aim of this study was to investigate to what extent polyamine metabolism in the small intestine of the rat is controlled by the enteric nervous system. Polyamine metabolism was followed by measuring the activity of ornithine decarboxylase (ODC) and in some instances also the content of polyamines (putrescine, spermidine and spermine). ODC activity in the intestine was increased when intraluminal pressure was increased and 3 h after placing cholera toxin in the intestinal lumen. Cholera toxin also increased the tissue putrescine content. Atropine or hexamethonium given i.v. did not influence the evoked changes of ODC activity. The pressure induced changes were not decreased by placing lidocaine on the serosal surface. On the other hand, the ODC activity of control segments were decreased by hexamethonium or atropine. The presence of glucose in the intestinal perfusate did not augment tissue ODC activity, neither did the heat stable enterotoxin from Escherichia coli (STa). It is concluded that the effect on polyamine metabolism evoked by luminal pressure or cholera toxin seems not to be mediated via nerves, while nerves seem to influence ODC activity during control conditions. The experiments with enterotoxins suggest that cAMP is the intracellular second messenger controlling intestinal ODC activity.     

Identification of neurons with acetylcholinesterase and NADPH-diaphorase activities in the centrifugal visual system of the chick

The isthmo-optic nuclei (ION) and ectopic neurons, which constitute the centrifugal visual system (CVS), are thought to be cholinoceptive and nitrergic. However, it is not clear which neurons express these markers, namely the ones that project to the retina rather than in neurons that only participate in a local circuit. Therefore, to characterize the neurochemical patterns of the centrifugal visual system in the post-hatched chick, retinopetal cells of the isthmo-optic nuclei and the ectopic region were identified via immunolabeling for cholera toxin, a neuronal tracer, which has been injected in the ocular globe. Then, double labeled with acetylcholinesterase histochemistry to reveal cholinergic synapses, or NADPH-diaphorase histochemistry as a nitrergic marker. Briefly, acetylcholinesterase activity was present mainly in cholera toxin labeled cell bodies of the isthmo-optic nucleus and the ectopic region indicating that retinal projecting neurons of centrifugal visual system comprise a cholinoceptive pathway. On the other hand, NADPH-diaphorase histochemistry was present in the neuropile and sparse cell bodies inside of the isthmo-optic nucleus and in ectopic neurons which were not cholera toxin positive suggesting their role in an intrinsic circuit of the centrifugal visual system. These data support the idea that these two neurochemical systems are present in distinct neuronal populations in the centrifugal visual system.     

Opioid dependence prevents the action of pertussis toxin in the guinea-pig myenteric plexus

Summary The longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum has been employed for the study of the effect of pertussis toxin (IAP) on opioid dependence. Guinea-pigs were treated with IAP (120 g/kg, i.p.) either prior to chronic administration of an opioid or after opioid dependence had been established. The isolated preparations were tested in vitro for dependence; that is, the naloxone-precipitated withdrawal contracture. Naloxone almost failed to evoke a sign of dependence in preparations treated with IAP prior to chronic exposure to an opioid. In contrast, IAP failed to affect the withdrawal contracture when applied to an animal after dependence has been established. It is concluded that theN _i-unit, the substrate for IAP, plays a critical function in the development of dependence. The continuous activation of the opioid receptor associated with the development of dependence may induce changes inN _i which in turn prevent the interaction of IAP with its substrate.     

Effects of sodium and GTP on the binding kinetics of [3H]diprenorphine in NG 108-15 cell membranes

Summary Equilibrium binding isotherms of [³H]diprenorphine in membranes from NG 108-15 cells are consistent with a homogenous population of binding sites. Upon addition of Na⁺, Mg²⁺ and GTP, only a 2-fold reduction in affinity with a minor decrease in the number of sites is observed. Dissociation curves of [³H]diprenorphine, however, are clearly biphasic: in the absence of Na⁺, Mg²⁺ and GTP, 80% of the bound ligand dissociates slowly with at _1/2 of 100 min, and only 20% rapidly (t _1/2 4.5 min). In the presence of Mg²⁺, nearly all the binding is found in the slowly dissociating form. Upon the addition of either Na⁺ or GTP, 20–30% of the binding dissociates more rapidly. The rate constant of the rapidly dissociating form generated by Na⁺, however, is 2.5 times greater than that induced by the presence of GTP. Thus, the addition of both, Na⁺ and GTP, converts about 80% of the receptor into a very fast dissociating form (t _1/2 1.7 min).Exposure of intact cells to pertussis toxin (10 ng/ml) or treatment of membranes with N-ethyl maleimide (500 M), strongly reduces the proportion of the slowly dissociating component. Following these treatments, the effect of GTP is reduced or abolished, but that of Na⁺ remains unaffected.We conclude from these data that the effects of Na⁺ and GTP are not only distinct in site but also in mechanism of action and that there are three forms of opioid receptors that can be differentiated by their kinetic properties. The slowly dissociating receptor form requires a functional N unit.     

一起赤潮后海产品麻痹性贝类毒素衰减结果分析

目的 以2017年漳州沿海一起赤潮引起的麻痹性贝类毒素(paralytic shellfish poisoning,PSP)中毒事件为研究起点,研究贝类海产品中的PSP在自然条件下的衰减情况。方法 在漳浦佛昙和龙海港尾海域采集牡蛎和贻贝进行PSP检测。结果 2017年6月8日相关海域海产品最大毒素总毒力为21 056.7 μg/kg,2017年6月26日海产品PSP总毒力值衰减86%以上,2017年7月20日海产品PSP总毒力值衰减97%以上,2018年12月所有海产品中PSP均未检出。结论 本次赤潮发生后,漳浦佛昙和龙海港尾两个海域贝类海产品约需45天净化周期方可食用,相关海域约需18个月净化至贝类毒素完全消失。     

A型肉毒毒素治疗面肌痉挛的疗效

目的 :观察A型肉毒毒素 (BTXA)治疗面肌痉挛的疗效。方法 :面肌痉挛患者 85例 ,既往均经药物、针灸、理疗、神经干阻滞等治疗无效。使用A型肉毒毒素 ,根据痉挛肌肉 ,于眼轮匝肌及面肌多点注射 ,每一注射点注射 2 .5U ,每次注射总剂量不应超过 5 5U。结果 :完全缓解者 92 .9% (79/ 85 ) ;明显缓解者 7.1% (6 / 85 ) ;总有效率 10 0 %。平均起效时间 (3.1±1.6 )d。平均疗效维持时间 (2 3.4± 2 .6 )周。未见全身副作用 ,局部副作用主要表现为闭目力弱 9例 ,眼睑下垂 5例 ,面肌无力 6例 ,均于 1月内自行缓解。结论 :A型肉毒毒素治疗面肌痉挛疗效显著 ,为一种简便、安全的方法。