Effect of nerve growth factor and GM1 ganglioside on the recovery of cholinergic neurons after a lesion of the nucleus basalis in aging rats

Summary A unilateral ibotenic acid lesion was placed in the nucleus basalis magnocellularis of 3- and 18-month-old rats. In the lesioned aging rats, the number of choline acetyltransferase-immunoreactive neurons of the nucleus basalis magnocellularis was markedly reduced in the ipsilateral side and to a lesser extent in the contralateral side. Twenty-one days after the lesion, the activity of choline acetyltransferase in the ipsilateral cortex was reduced by 40% in both groups of rats and by 24% in the contralateral frontal cortex of the aging rats. Intracerebroventricular administration of nerve growth factor (10 g, twice a week) to aging lesioned rats for 3 weeks after surgery resulted in a complete recovery in the number of choline acetyltransferase-immunoreactive neurons in the nucleus basalis of both sides, and choline acetyltransferase activity in the contralateral cortex, with little effect on the ipsilateral cortex. No potentiation was seen after the concurrent administration of GM1 ganglioside and nerve growth factor. Complete recovery in cortical choline acetyltransferase activity was only observed in the lesioned rats treated with nerve growth factor for 1 week before and 3 weeks after lesioning. Nerve growth factor treatment, both after the lesion, and before and after the lesion, improved the passive avoidance performance disrupted by the lesion. In young lesioned rats daily intraperitoneal administration of GM1 (30 mg/kg) for 21 days after surgery promoted both the recovery of choline acetyltransferase activity and passive avoidance performance. In aging rats GM1, even at a dose twice as large, failed to reverse the biochemical and morphological deficits and behavioral impairment induced by the lesion. Only when GM1 administration was started 3 days before the lesion, were a complete recovery in choline acetyltransferase activity in the contralateral cortex and a partial recovery in the ipsilateral cortex obtained.Our results indicate that nerve growth factor and, to some extent, GM1 facilitate the recovery of the cholinergic neurons after a lesion of the nucleus basalis in aging rats, but their efficacy is reduced. The lower efficacy of GM1 as compared to NGF might be due to the different routes of administration used.     

Behavioral significance of phasic changes in mesolimbic dopamine-dependent electrochemical signal associated with heroin self-injections

Summary High-speed chronoamperometry with monoamine-selective carbon fiber electrodes was used in rats to monitor, during 5–6 consecutive daily sessions, changes in DA-dependent electrochemical signal in the nucleus accumbens (NAcc) during intravenous heroin (0.1 mg/kg) self-administration (SA) behavior and passive repeated drug injections performed with a temporal scheme similar to that in the SA experiment. In trained animals, biphasic signal fluctuations time-locked to the individual lever-presses were found to accompany all but the first daily SAs. The signal gradually increased by 30–40 nM for the 10 minutes preceding the SA, reached a peak at the moment of lever-press and decreased abruptly by 40 nM for 3–4 min after heroin SA. The cycle then repeated, reaching a new peak at the moment of the next lever-press. Rapid bi-directional fluctuations in signal associated with individual heroin SAs were superimposed on substantial tonic increase in signal baseline (400–500 nM). This increase quickly developed after presentation of heroin-related light cue and the first SA, was relatively stable during all subsequent SAs and decreased towards the baseline after the last SA of a session. Changes in signal baseline induced by repeated heroin SAs depended strongly upon the signal's basal level (r=– 0.787); that signal preferentially increased when its basal values were low (0–300 nM), and decreased when signal was tonically elevated (> 600 nM). Repeated passive heroin injections also induced biphasic signal fluctuations and a similar tonic increase in signal baseline. Although a transient signal decrease (25 nM for 2–4 minutes) followed by a prolonged signal increase occurred after each but not the first passive injection, the gradual pre-injection signal acceleration was absent.Although DOPAC, a principal DA metabolite, may significantly contribute to the tonic increase in electrochemical signal seen during SA session, the changes in extracellular DA may be the main contributor to both the rapid signal increases preceding drug-taking and the transient signal decreases following heroin SA. If so, the present findings suggest that activation of mesolimbic DA cells and increase in DA transmission may be involved in the mediation of motivational and/or activational components of drug-seeking and drug-taking behavior. An acute termination of previous drug- and behavior-associated DA activation with a transient inhibition of DA release, immediately following heroin SA may correlate with the drug's rewarding action, representing a part of a mechanism regulating drug-taking behavior.     

Slicer and tissue retrieval system for excisional endoscopic surgery

Extraction of large specimens risks detachment of malignant cells within the peritoneal cavity and contamination of the parieties with resultant seedling implantation at the access wounds. Therefore, extraction is best conducted through a rip-proof sleeve-retrieval system which creates a third space in which the specimen can be sliced under visual control. Slicing of tissue is preferable to morcellation or disintegration since it preserves the structural integrity of the tissue and thereby does not jeopardize histopathological examination and staging of excised tumors. Of the two types of tissue-slicing mechanisms investigated, the compression-moving blade system (CMB) was found to be superior to wire-cutting devices. A prototype CMB slicer has been developed which has been tested experimentally and is currently undergoing clinical evaluation.     

消炎痛缓释系统的基础研究及新型T型铜药宫内节育器临床应用的初步研究

将消炎痛掺入SYZ-1医用加成型硅橡胶制成长21mm,直径为2.4mm含消炎痛40mg的均质型缓释药棒,通过体外消炎痛释放量测定,得出消炎痛缓释系统为非零级释放,释放时间至少持续360天,其生物安全性能评价结果全部合格,其经γ射线,环氧乙烷消毒后,无新物质产生,消炎痛释放规律不变。将该缓释系统应用于新型T型铜药宫内节育器,通过半年的临床观察有效地防止了放器后引起的月经过多,并随机选择10例放器后的妇女于分泌期吸取宫颈粘液测消炎痛含量,结果为7.44μg/ml粘液,5例妇女于分泌期吸取宫颈粘液测铜含量,结果为0.46μg/ml粘液湿重。选择15例妇女于放器前月经干净3～7天及放器1月月经干净3～7天对子宫内膜细胞后150个进行定量测定,结果示放器后1月子宫内膜细胞较放器前明显增大。     

Synergistic role of muscarinic acetylcholine and tachykinin NK-2 receptors in intestinal peristalsis

It is known that tachykinins (substance P, neurokinin A) participate in the excitatory neural pathways subserving peristaltic motor activity in the intestine. The aim of the present study was to elucidate the types of tachykinin receptor (NK-1 or NK-2) involved in peristalsis by the use of receptor subtype-selective antagonists. Peristaltic motility in isolated segments of the guinea-pig ileum was induced by pumping fluid into the oral end of the intestinal segment. By way of the intraluminal pressure the compliance of the intestinal wall during the preparatory phase and the pressure threshold to trigger the emptying phase of peristalsis were recorded. The tachykinin antagonists were used at concentrations that were at least 30 times in excess of the equilibrium dissociation constants which had previously been evaluated with receptor subtype-selective agonists on the guineapig ileum circular muscle. The NK-1 selective antagonist CP-96,345 (0.3 M) had a slight stimulant influence on peristalsis, whereas the NK-2 selective antagonists MEN-10,376 (10 M), GR-94,800 (0.3 M) and SR-48,968 (0.1 M) led to a small inhibition of motor activity. However, when given after exposure of the ileum to a threshold concentration of atropine (5–20 nM) causing little depression of peristalsis, the tachykinin NK-2 receptor antagonists invariably abolished peristalsis. This synergistic interaction was not seen when SR-48,968 was administered after the ileal segments had been exposed to concentrations of hexamethonium, isoproterenol or calcitonin gene-related peptide that by themselves caused a slight inhibition of peristalsis only. CP-96,345 was without effect on peristalsis when it was applied in the presence of a threshold concentration of atropine. These findings indicate that transmission via tachykinin NK-2, but not NK-1, receptors synergizes with cholinergic transmission via muscarinic receptors in the relay of excitatory enteric pathways subserving intestinal peristalsis. Correspondence to: P. Holzer at the above address     

Release and actions of adenosine in the central nervous system

Adenosine is released from active neurons into the extracellular fluid at a concentration of about 1mol/l. Neither the precise cellular origin nor the biochemical form of release has been firmly established, though the nucleotide is probably released partly directly, as a result of raised intracellular levels, and partly as nucleotides, which are subsequently hydrolysed. Once in the extracellular medium, adenosine markedly inhibits the release of excitatory neurotransmitters and modulatory peptides and has direct inhibitory effects on postsynaptic excitability via A₁ receptors. A population of A₂ receptors may mediate depolarization and enhanced transmitter release. Adenosine also modulates neuronal sensitivity to acetylcholine and catecholarnines, all these effects probably contributing to the behavioural changes observed in conscious animals. As a result of their many actions, adenosine analogues are being intensively investigated for use as anticonvulsant, anxiolytic, and neuroprotective agents.     

DNA repair synthesis following irradiation with 254-nm and 312-nm ultraviolet light is not diminished in fibroblasts from patients with dysplastic nevus syndrome

The DNA excision repair capacity of 23 primary fibroblast lines from patients with dysplastic nevus syndrome was investigated and DNA repair synthesis (unscheduled DNA synthesis) was determined after UV exposure. Seventeen fibroblast lines from normal donors served as controls. The dose/response experiments included up to ten dose levels and two wavelength ranges: UV-C (using a low-pressure mercury lamp emitting predominantly 254-nm light) and UV-B (artificial sunlamp radiation centering around 312-nm light). For each dose level, silver grains over fibroblast nuclei were counted by visual inspection. Twelve cell lines were also evaluated for both UV wavelength ranges using a new semi-automatic image analyzing system. This system included components for rapid sequential identification of both fibroblast nuclei and silver grains sited above them. Silver grains over 100 nuclei were determined for each UV dose level. Dose/response curves were established and analyzed by linear regression. As a quantitative term for assessing DNA excision repair capacity of a cell line we calculated the linear increase (G ₀) in the number of grains per nucleus, when the UV dose was multiplied by the factor e (i.e. 2.72). The sensitivity of grain detection and resolution ofoverlapping grains was approximately threefold better in visual than in automatic counting, especially when there were more than 70 grains over nuclei. The time recired for visual conting, however, was tenfold that of automatic counting. The varianceweighted meanG ₀ ^v,w of all fibroblast lines from patients with dysplastic nevus syndrome was found to be 79.1 (±1.8-grains/nucleus, that of fibroblast lines from normal donors was 74.2 (±1.7) grains/nucleus. This difference revealed a slightly better repair capability for cell lines from patients but was at the borderline of detection and, therefore, should not be overinterpreted. From the experimental accuracy achieved by determination of the varianceweighted means of the two groups, we would have been able to detect a difference of 7 and more grains [> 2 x (_normal + _patients)]. The variance-weighted meanG _o ^v,w of all fibroblast lines from patients with dysplastic nevus syndrome was found to be 76.4 (±1.4) grains/nucleus, whereas that of fibroblast lines from normal donors was only 66.6 (±1.8) grains/nucleus. This difference was statistically significant and, contrary to expectation, revealed better, not worse post-UV DNA repair capability in cell lines from patients that in those from normal donors. From the experimental accuracy achieved by determination of the variance-weighted means of the two groups, we would have been able to detect a difference of 6.4 or more grains [> 2 x (_normal + _patients)]. Variation between cell lines belonging to the same group was expressed by the standard deviation. On average, the standard deviation was in the range 18.2–21.1 grains/nucleus. This variation did not reflect experimental inaccuracy but different responses of individual cell lines to UV irradiation. On the basis of our data, we consider the hypothesis that patients with dysplastic nevus syndrome are prone to melanoma development because of a general defect in post-UV DNA repair to be improbable.This work was supported by the Deutsche Forschungsgemeinschaft, SFB 136     

Haptic localization and the internal representation of the hand in space

As the hand actively explores the environment, contact with an object leads to neuronal activity in the topographic maps of somatosensory cortex. However, the brain must combine this somatotopically encoded tactile information with an internal representation of the hand's location in space if it is to determine the position of the object in three-dimensional space (3-D haptic localization). To investigate the fidelity of this internal representation in human subjects, a small tactual stimulator, light enough to be worn on the subject's hand, was used to present a brief mechanical pulse (6-ms duration) to the right index finger before, during, or after a fast, visually evoked movement of the right hand. In experiment 1, subjects responded by pointing to the perceived location of the mechanical stimulus in 3-D space. Stimuli presented shortly before or during the visually evoked movement were systematically mislocalized, with the reported location of the stimulus approximately equal to the location occupied by the hand 90 ms after stimulus onset. This pattern of errors indicates a representation of the movement that fails to account for the change in the hand's location during somatosensory delays and, in some subjects, inaccurately depicts the velocity of the actual movement. In experiment 2, subjects were instructed to verbally indicate the perceived temporal relationship of the stimulus and the visually evoked movement (i.e., by reporting whether the stimulus was presented before, during, or after the movement). On average, stimuli presented in the 38-ms period before movement onset were more likely to be perceived as having occurred during rather than before the movement. Similarly, stimuli in the 145-ms period before movement termination were more likely to be perceived as having occurred after rather than during the movement. The analogous findings of experiments 1 and 2 indicate that the same inaccurate representation of dynamic hand position is used to both localize tactual stimuli in 3-D space and construct the perception of arm movement.     

Effects of prostaglandin F2α(PGF2α) and prostaglandin I2 (PGI2) on nerve-mediated secretion in guinea-pig colon

We have applied conventional flux-chamber and intracellular recording methods to investigate the effects of the prostaglandins PGF₂ and PGI₂ upon epithelial ion transport and on the electrical behaviour of submucosal neurones in guinea-pig colon. In flux-chamber experiments on segments of colon, both prostaglandins evoked a dose-dependent increase in short-circuit current that was reduced in chloridedepleted Krebs solution and by serosal addition of tetrodotoxin or atropine, but was unaffected by hexamethonium. These results indicate activation of chloride secretion via submucosal neurones. The response to PGF₂ was decreased by piroxicam. Application of PGF₂ or PGI₂ to submucosal neurones evoked depolarization of the membrane potential associated with an enhanced spike discharge. The depolarizing response was tetrodotoxin insensitive, indicating a direct effect of the prostaglandins on the impaled neurones. Membrane depolarization was frequently associated with the occurrence of fast excitatory postsynaptic potentials, suggesting in addition that part of the excitatory effect is mediated by the activation of neural circuits that drive the impaled neurone synaptically. The results of this study indicate that the secretory effects of prostaglandins are mediated in part by submucosal neurones and further suggest that the colonic submucosal plexus may function as an amplifier to enhance the epithelial response to inflammatory mediators.