Electrical activity of red nucleus neurones investigated with intracellular microelectrodes

Summary Microelectrodes were inserted into the magnocellular portion of cat's red nucleus (RN), and some basic physiological properties of RN cells were examined by both extra- and intracellular recording. During stimulation of the rubrospinal fibres at the spinal segmental level, the RN cells were invaded antidromically, producing conspicuous field potentials within RN. The somatotopical distribution of RN cells was confirmed by comparing the field potentials induced from C₂ and L₁ levels. When recorded intracellularly, antidromic action potentials showed three-step configuration as those in motoneurones and were followed by a remarkable after-hyperpolarization. The conduction velocity along the rubrospinal fibres ranged from 41–123 m/sec, with the peak frequency at 91–100 m/sec. The membrane properties were examined in some RN cells by intracellular application of current steps. The total membrane resistance was 4 M on the average, and the membrane time constant 6 msec, respectively.Excitatory postsynaptic potentials (EPSPs) were induced monosynaptically in RN cells by stimulation of the nucleus interpositus of the contralateral cerebellum. Their time course was analyzed in comparison with that of the potentials produced by current steps. Stimulation in the ventrolateral nucleus of the thalamus evoked monosynaptic EPSPs via the collaterals of the interpositus axons which innervate RN and thalamus commonly. It was further shown that impulses in cortico-rubral fibres produced EPSPs in RN cells. These cerebral-evoked EPSPs were characterized by much slower time courses than those from the nucleus interpositus.     

Typical and partial cat eye syndrome: identification of the marker chromosome by FISH

Three children are reported with typical cat eye syndrome (CES) and three more children with partial CES because of absence of coloboma, in which the supernumerary marker chromosome was studied by FISH. Using a genomic library, and also a centromeric and particularly a cosmid probe of 22q11, partial tetrasomy was shown in all cases.     

How do patch clamp seals form? A lipid bleb model

Individual ion channels are electrically isolated and studied in living cells with the tight patch voltage clamp method. Channels are identified, categorized, and sometimes named on the basis of the biophysical properties obtained with this method. Although it is usually presumed that these recordings are from native, undisturbed membrane, the physical basis of this technique is not well established. Observations that lipid blebs readily form when suction is applied to patch clamp electrodes suggest that many single channel recordings are from ion channels in these blebs.     

A convenient method for repeated intracellular recording of action potentials from the same muscle fibre without membrane damage

Summary Repeated intracellular recording of end-plate and action potentials from the same muscle fibre is often impossible because the membrane is damaged by the microelectrode when the muscle twitches. Membrane damage can be avoided by rolling and simultaneously stretching the muscle around a polyethylene rod; the amount of stretch necessary is about 50% of the “in-situ” length. Supported by the Deutsche Forschungsgemeinschaft, Sonderforschungsbereich 38 “Membranforschung”, Bad Godesberg. Established Investigator of the Consejo Nacional de Investigaciones Científicas y Tecnicas, Argentina     

补肾中药对老年大鼠脑组织中胆碱能M受体分布的影响

采用受体放射配基结合分析、原位杂交和放射自显影术等方法,研究胆碱能M受体、M1受体mRNA在脑组织中的分布,观察补肾中药对胆碱能M受体的含量、功能及分布的影响,探讨补肾中药延缓脑组织衰老的机理.结果显示:老年大鼠大脑皮层、海马、纹状体中M受体明显减少,放射自显影的灰度值降低,胆碱能M1受体mRNA在老年大鼠纹状体部位的表达减少,在其他部位的不明显.补肾中药明显增加老年大鼠胆碱能M受体的数量,对脑内胆碱能M1受体mRNA转录水平降低的部位有改善作用.补肾中药可通过改善胆碱能M1受体的mRNA表达、增加脑内胆碱能M1受体数量来延缓脑组织衰老.     

应用核酸分子杂交技术检测心肌炎组织中的肠道病毒RNA

用生物素标记ｐＣＢＩＩＩ／３５和ｐＣＢＩＩＩ／５１肠道病毒属特异性探针，对４５心肌炎和心肮病尸检或心肌活检心脏组织进行原位杂交，结果显示：１２例（２６．６％）存在肠道病毒ＲＮＡ。柯萨基Ｂ３病毒型特异性探针ｐＣＢＩＩＩ／２９进一步杂交表明，１２例经证实存在肠道病毒ＲＮＡ的心肌组织中５例（４１．７％）出现阳性杂交信号。阳性杂信号主要位于单个或多个心肌细胞的胞浆和心肌的间质组织，偶见竽心肌小血管内皮细胞     

Expression of the axon growth-related neural adhesion molecule TAG-1/axonin-1 in the adult mouse brain

 TAG-1/axonin-1 is a neuronal cell adhesion molecule of the immunoglobulin superfamily. It is predominantly expressed during neural development and has been reported to be involved in axonal growth and pathfinding. Here, the expression of TAG-1/axonin-1 was investigated anatomically in the adult mouse brain by in situ hybridization using digoxigenin-labeled cRNA probes. Low levels of TAG-1/axonin-1 could be detected in cerebellar granule cells, in tufted and mitral cells of the olfactory bulb, and in pyramidal cells of area CA1 and CA3 of the hippocampus. We suspect that the expression of TAG-1/axonin-1 in these structures of the adult brain may serve neural plasticity. Accepted: 8 September 1997     

Immunohistochemistry and in situ hybridization of the androgen receptor in the developing human prostate

 As it is suggested that the androgen receptor mechanism is required for prostatic development, we attempted to determine the appearance, expression and distribution of the androgen receptor in embryonic, infantile and pubertal human prostate. Using mono- and polyclonal antibodies and a digoxigenin-labeled 713 bp riboprobe, the androgen receptor expression in paraffin sections of fetal, infantile, and pubertal prostates was studied at the protein and RNA level. Under highly standardized conditions, application of the polyclonal antibodies resulted in a weak cytoplasmic and nuclear labeling of the epithelium of fetal glands. No immunoreaction was obtained with monoclonal antibodies. Applying the polyclonal antibody to pubertal and adult specimens, immunoreactivity of the androgen receptor was positive in nuclei of adluminal and basal epithelial cells, in interstitial and vascular smooth muscle cells and vascular endothelium, whereas ganglionic cells and enteroendocrine cells were negative. In situ hybridization with the digoxigenin-labeled riboprobe gave clear positive results already in epithelium of very young fetal specimens. A semiquantitative visual evaluation of in situ hybridizations showed that intermediate intensity of expression was increased in pubertal and adult specimens, whereas strong expression was reduced in prostatic epithelium. Conclusions: The essential findings are: (1) an early expression of androgen receptor mRNA in the fetal prostate; (2) no immunoreaction of monoclonal antibodies against the androgen receptor in the same specimens, (3) a decrease of androgen receptor mRNA expression, but increase in immunoreactivity of the androgen receptor protein with the onset of glandular maturation during puberty. Accepted: 29 September 1997     

Cholecystokinin and neurotensin mRNAs are differentially expressed in subnuclei of the ventral tegmental area

Immunohistochemical studies of ventral tegmental area (VTA) neurons indicate that individual cells can contain dopamine as well as the neuropeptide neurotransmitters cholecystokinin (CCK) and neurotensin (NT). We have defined the distribution of the cells expressing the mRNAs encoding these two dopamine cotransmitter peptides in each of the subnuclei of the ventral tegmental area, and quantitated the extent of expression of each gene by using in situ hybridization methods. These studies reveal significant differences in the patterns of expression of each of these two genes within various subdivisions of the VTA. The rostral linear nucleus contained numerous CCK positive cells, some of which appeared to express preproCCK-mRNA at a very high level, but this nucleus contained relatively few NT-expressing cells. The parabrachialis pigmentosus contained numerous NT and CCK positive cells. The paranigralis and interfascicularis nuclei displayed positive CCK cells but with expression at only modest levels. NT cells were very few in these nuclei. The caudal linear nuclei contained the highest number of NT-expressing neurons and these cells expressed very high levels of NT mRNA. The selective distribution of these peptide genes within the VTA subnuclei may have specific consequences. Studies of the connectivity of neurons in the VTA show that the different subnuclei of this region project to several functionally and architectonically different regions of the cerebral cortex and subcortically to nuclei related to the limbic system. Results from our study show very prominent expression of CCK mRNAs in those subnuclei that project heavily to the prefrontal, other cortical areas, and the amygdaloid complex. The NT gene is expressed prominently in those subnuclei of VTA that project heavily to the entorhinal cortex and amygdaloid complex. These results provide support for a differential role for the NT-expressing neurons than that of CCK-expressing neurons of VTA in "reward" mechanisms and in drug-seeking and motivational behavior. These observations could be applied to create working hypotheses and experimental paradigms to test the differential functional activity of the subdivisions of VTA and their potential roles in the pathogenesis and treatment of drug-seeking behavior and other neuropsychiatric disorders.     

A Collection of cDNA Clones with Specific Expression Patterns in Mouse Brain

A total of 950 cDNA clones were randomly selected from mouse cerebellar cDNA libraries, and of these, about 130 clones were found to correspond to mRNAs which were expressed unequally between the cerebellum and other parts of mouse brain. Their distribution patterns in adult mouse brain were analysed by in situ hybridization, and eight clones were found restricted to specific regions of the brain, including four clones specific to cerebellar granule cells and one clone specific to Purkinje cells. Another 27 clones were preferentially expressed in a diverse, but distinctive subpopulation of brain cells. Among them seven clones were especially abundant in specific nuclei, and three in specific fibre bundles. These clones will be useful in defining new subpopulations of brain cells characterized by different gene expression.