Quantitative changes in gene expression of glutamate receptor subunits/subtypes in the vestibular nucleus, inferior olive and flocculus before and following unilateral labyrinthectomy in the rat: real-time quantitative PCR method

Spontaneous recovery from the oculomotor and postural symptoms of unilateral labyrinthectomy (UL) is known as vestibular compensation, which is a useful model for investigation of the mechanisms of lesion-induced CNS plasticity. In the present study, to elucidate the molecular biological basis of vestibular compensation, we investigated changes in the mRNA expression of glutamate receptor subunit/subtypes in the rat central vestibular system, including the vestibular nucleus complex (VNC), inferior olive (IO), and cerebellar flocculus following UL, using a real-time quantitative polymerase chain reaction (PCR) method. In normal control animals, regional differences in the expression of several glutamate receptor subunit/subtypes, e.g., NR1 and NR2A subunits of the N-methyl-D-aspartic acid (NMDA) receptor, GluR2 and KA2 subtypes of non-NMDA receptors, and mGluR1 and mGluR7 metabotropic glutamate receptors, were consistent with previous results from studies using in situ hybridization histochemistry, suggesting that the real-time quantitative PCR method was a reliable procedure for evaluation of changes in mRNA expression. In the vestibular nucleus complex, NR2A, GluR2 and mGluR7 mRNA were ipsilaterally downregulated by 6 h following UL (P<0.05, P<0.05 and P<0.01, respectively). In the inferior olive, no changes in gene expression were observed. In the ipsilateral flocculus, KA2 mRNA expression was increased by 50 h post-UL (P<0.05). However, in the contralateral flocculus, mGluR1 mRNA was downregulated by 6 h post-UL (P<0.005). Both the increase in KA2 mRNA expression in the ipsilateral flocculus and the decrease in mGluR1 mRNA expression in the contralateral flocculus may have had the effect of reducing Purkinje cell inhibition of ipsilateral VNC neurons, thereby contributing to the rebalancing of spontaneous resting activity between the ipsilateral and contralateral VNCs. It is suggested that such changes in the activities of the floccular-VNC pathways may be important to the vestibular compensation process. Electronic Publication     

膀胱抗菌机制—粘膜抗菌蛋白初步研究

本文报道以１％乙酸冲洗雌性Ｗｉｓｔａｒ大鼠膀胱和雌性新西兰白兔膀胱，分别获得其膀胱酸溶性提取物。ＡＵ－ＰＡＧＥ分析表明，两种膀胱粘膜酸溶性提取物都有十余条主蛋白带，而不含常见的杀菌物质溶菌酶和防御素样分子。琼脂糖弥散法杀菌试验显示，两种膀胱粘膜酸溶性提取物对致病性大肠杆菌ＭＬ－３５ｐ耐药株都有杀菌活性。进一步采用电泳凝胶琼脂糖弥散法杀菌试验分析，结果表明大鼠膀胱粘膜酸溶性提取物中有两条蛋白带具明显的杀菌活性，我们称这两条蛋白带为ＲａｔＢＰ－１和ＲａｔＢＰ－２。而兔膀胱粘膜酸溶性提取物的杀菌活性亦与两条被称为ＲａｂＢＰ－１和ＲａｂＢＰ－２的蛋白带相关。本文首次提示，在膀胱粘膜内存在抗菌蛋白，可能是膀胱粘膜杀菌作用的分子基础。     

Analysis of feeding patterns in normal and vagotomized rabbits.

Spontaneous meal sizes, intermeal intervals, and 24 hr feeding rhythms were monitored in normal and 60 day recovered vagotomized rabbits fed solid laboratory chow. Mean sizes of meals and intermeal intervals, and the circadian distribution of food intake did not differ between the two groups, but vagotomy was associated with increased frequencies of both smaller and larger than average meals. Positive meal to postmeal interval correlations were evident in intact but not vagotomized animals, whereas vagotomized animals displayed a meal to premeal interval correlation in the light phase that was not present in normal rabbits.     

Expression of the monoclonal antibody HECA-452 defined E-selectin ligands in Langerhans cell histiocytosis

The cutaneous lymphocyte associated antigen (CLA) recognized by the monoclonal antibody (moAb) HECA-452 plays a major role in the homing of lymphocyte subpopulations to the skin by binding to E-selectin on dermal microvessels. The factors responsible for the immigration of Langerhans cells (LC) and their precursors into the skin are still unknown, but because normal resting LC are also capable of expressing CLA, the antigen was proposed as a candidate LC-homing structure. To gain insight into these mechanisms, the expression of HECA-452 on neoplastic LC within and outside the skin was investigated in paraffin-embedded sections from 44 patients with localized and disseminated forms of Langerhans cell histiocytosis (LCH) presenting with proliferating cells positive for CD45, CD1a, S100 and HLADR. Irrespective of the clinical presentation or the type of organ involved, HECA-452-positive LC were detected in all biopsies tested (range 5->90%). The most prominent HECA-452 reactivity was observed in skin lesions and in areas with accumulations of eosinophilic granulocytes. Our data provide evidence for a heterogeneous expression of sLe^x/sLe^a structures in various stages of activated and/or differentiated LCH cells. Remarkably, CLA-antigen expression on LCH-cells was not restricted to cutaneous sites. In view of recent findings on the expression of HECA-452 on resting epidermal LC, our data are compatible with the view that local cytokine production by keratinocytes or cells from the surrounding infiltrate induce and/or modulate CLA expression on LC in both cutaneous and extra-cutaneous sites.This work is dedicated to Professor Dr. Thaddäus Radaszkiewicz, who died in September 1995     

大肠埃希菌中氟喹诺酮耐药机制功能分析

目的 分析拓扑异构酶的突变和外排泵系统在大肠埃希菌(Escherichia coli)氟喹诺酮类药物耐药机制中的作用.方法 本研究通过基因重组技术对大肠埃希菌中拓扑异构酶不同点突变的功能进行了准确测定,同时也对大肠埃希菌中不同外排泵及膜蛋白的功能进行了分析.结果 在不同的菌株中,acrAB或tolC的切除所引起细菌耐药性的变化不同.对拓扑异构酶点突变的功能分析显示,gyrA中的点突变(S83和D87)在喹诺酮耐药机制中起主要作用,没有gyrA上的点突变,parC上的点突变(S80和A108)对细菌的耐药性不产生影响,但单独gyrA上的点突变(S83和D87)也仅导致敏感菌株对萘啶酸耐药,而对其他氟喹诺酮类药物仍表现为敏感.当对喹诺酮敏感的大肠埃希菌K-12同时具备gyrA(S83L和D87N)和parC(S801和A108V)上的点突变后,重组菌株对氟喹诺酮会自然产生耐药性,而并不需要过度表达的外排泵.结论 拓扑异构酶的突变在大肠埃希菌氟喹诺酮药物的耐药机制中起主要作用,对氟喹诺酮药物耐药的菌株通常应同时具备gyrA和parC上的点突变.     

Somatic spectrum of cancer-associated single basepair substitutions in the TP53 gene is determined mainly by endogenous mechanisms of mutation and by selection

The spectrum of somatic TP53 single basepair substitutions detected in 955 cancers was compared with that of 2,224 different germline mutations in 279 different human genes (other than TP53), reported as the cause of inherited disease. This comparison reveals that, disregarding a relatively small subset (12%) of TP53 mutations that probably result from the action of exogenous mutagens, both the relative rates and the nearest-neighbor spectra of single basepair substitutions are similar in the two datasets. This spectral resemblance suggests that a substantial proportion of cancer-associated somatic TP53 mutations result from endogenous cellular mechanisms. The likelihood of clinical observation of a particular mutation type differs, however, between tumors and genetic diseases, when the chemical properties of the resulting amino acid substitutions are considered. Together with a sixfold higher observation likelihood for mutations at evolutionary conserved residues, this finding argues that selection is a critical factor in determining which TP53 mutations are found to be associated with human cancer. © 1995 Wiley-Liss, Inc.     

The control of retinogeniculate transmission in the mammalian lateral geniculate nucleus

Summary In the mammalian visual system, the lateral geniculate nucleus is commonly thought to act merely as a relay for the transmission of visual information from the retina to the visual cortex, a relay without significant elaboration in receptive field properties or signal strength. However, many morphological and electrophysiological observations are at odds with this view. Only 10–20% of the synapses found on geniculate relay neurons are retinal in origin. Roughly half of all synapses derive from cells in layer VI of visual cortex; roughly one third are inhibitory and GABAergic, derived either from interneurons or from cells of the nearby perigeniculate nucleus. Most of the remaining synapses probably derive from cholinergic, noradrenergic, and serotonergic sites within the brainstem reticular formation. Moreover, recent biophysical studies have revealed several ionic currents present in virtually all thalamic neurons. One is a Ca²⁺-dependent K⁺ current underlying the afterhyperpolarization (or the I_AHP), which may last up to 100–200 ms following an action potential. Activation of the I_AHP leads to spike frequency adaptation in response to a sustained, suprathreshold input. Intracellular recordings from other neuronal preparations have shown that the I_AHP can be blocked by noradrenalin or acetylcholine, leading to an increased cellular excitability. Another ionic current results from a voltage- and time-dependent Ca²⁺ conductance that produces a low threshold spike. Activation of this conductance transforms a geniculate neuron from a state of faithful relay of information to one of bursting behavior that bears little relationship to the activity of its retinal afférents. We propose that state-dependent gating of geniculate relay cells, which may represent part of the neuronal substrate involved in certain forms of selective visual attention, can be effected through at least three different mechanisms: (1) conventional GABAergic inhibition, which is largely controlled via brainstem and cortical afferents through interneurons and perigeniculate cells; (2) the I_AHP, which is controlled via noradrenergic and cholinergic afferents from the brainstem reticular formation; and (3) the low threshold spike, which may be controlled by GABAergic inputs, cholinergic inputs, and/or the corticogeniculate input, although other possibilities also exist. Furthermore, it seems likely that gating functions involving the corticogeniculate pathway are suited to attentional processes within the visual domain (e.g., saccadic suppression), whereas brain-stem inputs seem more likely to have more global effects that switch attention between sensory systems. In any case, it is now abundantly clear that geniculate circuitry and the intrinsic electrophysiological properties of geniculate neurons are no longer compatible with the notion that the lateral geniculate nucleus serves as a simple relay.     

Differences in the activation of m. biceps brachii in the control of slow isotonic movements and isometric contractions

Summary We have compared muscle activation in the control of slow isotonic movements and isometric contractions. Specific attention has been given to the contribution of the two force-grading mechanisms, the recruitment of motor units and the modulation of firing frequency in motor units that have already been recruited. The recruitment order of the m. biceps motor units under study was the same during isometric contractions and slow isotonic movements. However, the recruitment thresholds of the m. biceps units were considerably lower for both isotonic flexion and extension movements, even at velocities as low as 2 deg/s, than for isometric contractions. Furthermore, firing frequency at recruitment was found to depend on the motor task: at recruitment the motoneurone starts firing with a higher firing frequency during isotonic flexion movements and a lower firing frequency during isotonic extension movements than during isometric contractions. Two main conclusions can be drawn from these results. First of all, the concept of one single activation parameter (total synaptic drive?) cannot account for the motor-unit behaviour observed during our experiments: the relative contribution of the two forcegrading mechanisms is different for different tasks. Secondly, the distribution of activity among flexor motoneurone pools is different for isometric contractions and isotonic movements.     

Forelimb reflexes modulated by tonic neck positions in cats

The modulation of monosynaptic forelimb reflexes by tonic neck positions was investigated in cats with the head fixed.Lateral flexion of the body in a horizontal plane markedly facilitates reflexes of the deep radial nerve (DR) in the ipsilateral forelimb, while the antagonistic ulnar nerve (ULN) reflexes are strongly inhibited. Opposite effects are seen after contralateral body movement.Dorsiflexion of the body clearly increases DR-reflexes and exerts a reciprocal although more pronounced inhibition on ULN reflexes. Opposite effects appear after ventriflexion.The reflex modulation starts with head-body displacements of approximately 5° and increases with increasing angles. Furthermore reflex modulation does not depend on the intact cerebrum and cerebellum. The comparison of forelimb and hindlimb reflexes shows a decrease of the neck influences along the spinal cord.Supported by Sonderforschungsbereich Hirnforschung und Sinnes-physiology (SFB 70) der Deutschen Forschungsgemeinschaft (DFG).Essential parts of this paper will be submitted by A. F. as a thesis to the Faculty of Medicine, Freiburg/Breisgau, Germany.     

Plasticity of the central nervous system—a neurosurgeon's experience of cerebral compensation and decompensation

Summary Cerebral plasticity constitutes one of the most decisive factors in recovery and readaptation after cerebral lesions. In contrast to the considerable progress in current studies on normal neuronal plasticity including the idea of l'homme neuronal, the concept of plasticity postulated by Albrecht Bethe in 1929 received little attention. The author, as a neurosurgeon, has tried to describe cranial morphological plasticity, morphological and functional plasticity in infantile encephalopathies and especially in hemiatrophic lesions. It is supposed that a true morphological substrate exists due to compensatory hyperplasia of the uninvolved hemisphere.Modern neurosurgical techniques have demonstrated that the functional plastic capacity is much larger than has been supposed, even in the elderly. Some aspects of the mechanisms of compensation and decompensation of cortical and subcortical structures as well as of the central regulation systems are discussed. The full extent of the amazing recovery and functional reorganization is reached by plastic capacity, personal motivation, adequate training and sufficient time.The contribution ends with an exposition of a personal philosophy concerning psycho-somatic dualism, the body-mind problem, the future of the human brain and the ethical outlook, based on the progressive biological evolution of the basal neocortex and the immanent functional development (H. Spatz).In grateful memory of my paternal friends, the great German brain researchers Julius Hallervorden (1882–1965) and Hugo Spatz (1888–1969).