Mossy and climbing fibre organization on the anterior lobe of the cerebellum activated by forelimb and hindlimb areas of the sensorimotor cortex

Summary Stimulation of forelimb and hindlimb areas of the sensorimotor cortex in the cat evokes in the lobus anterior of the cerebellum an early response at latency of 3–3.5 msec due to the mossy fibre input (MF) and a later response at latency of 13–16 msec due to the climbing fibre (CF) input.In the pars intermedia these two types of responses are organized in a somatotopic manner: the hindlimb area projects in lobuli HIV and HIII whereas the forelimb area projects to lobulus HV. In the vermis a somatotopic arrangement is less clear. Both forelimb and hindlimb areas of the sensorimotor cortex project to lobuli III, IV and V: on a maintained somatotopy in a caudo-rostral direction there is a tendency for the hindlimb area of the sensorimotor cortex to be well represented in a longitudinal strip close to the paravermal sulcus. This arrangement in the vermis is evident for the CF pathways, but more difficult to demonstrate for the MF pathways.The forelimb area of the sensorimotor cortex projects to those areas of the lobus anterior impinged upon by the forelimb nerves through both the MF and CF systems and the same holds true for the hindlimb area and the hindlimb nerves.     

额叶脑回的横断层定位

目的:在横切面上利用髓突对成人端脑额叶脑回进行影像学定位.方法:取20例正常成人尸头标本,作层厚6mm之横切脑片,选取其中典型层面,观察分析额上、中、下回所对应髓突的方向、数目等特征形态.结果:各切面.各脑回所对应髓突为1～2支;时针12-12点半方向髓突所对应脑回是额上回;时针12点半-1点(左)及10点半-11点半(右)方向髓突所对应脑回是额中回;时针2-3点(左)及9-11点(右)方向髓突所对应脑回是额下回.结论:额上、中、下回与髓突之间有对应规律可寻,影像学上可以通过髓突定位额上、中、下回.     

cAMP-induced stellation in primary astrocyte cultures with regional heterogeneity

It is well known that increased cAMP levels in cultured astrocytes can convert flat polygonal shaped astrocytes into process-bearing, stellate astrocytes. In this study, we have examined the possible existence of astrocyte regional heterogeneity in morphological changes in response to cAMP stimulation. Primary astrocyte cultures were prepared from six different regions of neonatal rat brains, including cerebral cortex, hippocampus, brain stem, mid brain, cerebellum, and hypothalamus. After about 2 weeks in culture, the astrocyte culture medium was changed to DMEM containing various concentrations of 8-CPT-cAMP, a membrane permeable cAMP analog, for 2 h. We found that 250 microM 8-CPT-cAMP produced a maximum effect causing >95% stellation in all regional astrocytes except hypothalamic astrocytes (56% stellation). At lower cAMP concentrations, cell stellation most effectively occurred in cerebellar astrocytes. To examine further the regional heterogeneity of astrocyte morphological changes, glutamate was added together with 8-CPT-cAMP to block cAMP-induced astrocyte stellation. Interestingly, glutamate blockage on cAMP-induced astrocyte stellation was brain region-specific in that cerebral and hippocampal astrocytes were effectively blocked by glutamate when compared to other regional astrocytes. Furthermore, glutamate inhibited isoproterenol-induced astrocyte stellation in a region-specific manner similarly as in cAMP-induced stellation. The present study demonstrates that astrocytes derived from different regions of the neonatal rat brain maintain different levels of morphological plasticity in culture.     

Electron microscopy of endocytic elements in the cat cerebrum

Summary Small quantities of ferritin or Thorotrast were injected into the visual cortex of the cat in order to determine which cells in the cerebrum exhibited endocytic activity when exposed to foreign material. Blocks of tissue from the cortex and adjacent white matter were examined by electron microscopy 5 h and 20 h after injection.Some neurons and oligodendrocytes and all the astrocytes examined showed pinocytotic activity. Increasing the time of exposure of the tissue to the tracer did not appear to result in greatly increased uptake by individual cells, except in the case of astrocytes.Neutrophils, which invaded the tissue after 5 h, and in increased numbers after 20 h, exhibited minimal endocytic activity when they invaded the grey matter. They were more active in the white matter.Up to 20 h after injection, the three most important endocytic elements in the cerebrum were astrocytes (collectively), pale perivascular cells within the basement membrane of the blood vessels and phagocytes, which appeared to be reactive endogenous cells.Many thanks are due to Professor M. J. Blunt, School of Anatomy, University of N.S.W., for his helpful criticisms throughout the course of this study, which was supported by a research grant from the National Health and Medical Research Council of Australia to Professor Blunt. The assistance of Mrs. Ruth Mather is gratefully acknowledged.     

Functional significance of arrangement of neurones in cell assemblies

Summary An account is given of the columnar arrangement in the cerebral cortex that has been discovered for neurones having a similar receptivity. This has been observed in the somaesthetic cortex for neurones with similar modality sensitivities and in the visual cortex for neurones with similar directional sensitivities. The anatomical basis is discussed. In the motor cortex also there is an arrangement in clusters of pyramidal cells that are responsible for particular movements.The functional significance of this organization in clusters in the cerebral cortex is discussed in relationship to the problem of securing a reliable performance despite the irregular background discharge of the individual neurones. It is proposed that reliability is secured by the in-parallel arrangement of neurones with similar receptivities in the clusters. The neurones of a cluster tend to converge onto common target neurones, which, as it were, read out the summed performance of the cluster from moment to moment. Recent work on the cerebellum also discloses that there is an arrangement of Purkyn cells in clusters with somewhat similar receptive fields and that their axons tend to converge onto neurones of the cerebellar nuclei (fastigial nucleus), which likewise are arranged in functional clusters.The general concept emerges that the arrangement of neurones in clusters both in the cerebrum and in the cerebellum, achieves functional significance not only in giving opportunity for amplification and integration of incoming signals and for their sharpening by surround inhibition, but it is also important in the output performance. Signals are lifted out of noise by the spatial summation deriving from the many similarly performing neurones that project by their axons to the same cluster of target neurones; and this orderly projection can go on sequentially through all the complexities of on-going actions initiated by some input.Prof. R. Jung to his 60th birthday.     

碘过量对仔鼠大脑锥体细胞的形态学影响

目的 探讨碘过量对Wistar大鼠仔鼠大脑锥体细胞的形态学影响。方法将断乳后1个月Wistar大鼠随机分为5组（NI、5HI、10HI、50HI、100HI）,饮用不同浓度的碘水,饲养3个月后雌雄合笼,取第二代1、20、60日龄仔鼠,观察仔鼠的脑发育。结果在1日龄仔鼠中,与NI组相比,各碘过量组仔鼠锥体细胞顶树突棘突密度、棘突的分布类型、锥体细胞基树突数、初级树突分枝指数、锥体细胞的最大横截面积、体密度和面数密度均无明显变化（P〉0．05）;在20日龄仔鼠中,100HI组顶树突棘突密度、锥体细胞的最大横截面积较NI组减小（P〈0．05）;而在60日龄仔鼠中,50HI组和100HI组与NI组相比都表现出一定程度的脑发育落后,其中以100HI组最为明显（P〈0．05）。结论大鼠对碘过量有极强的耐受力,严重碘过量（正常摄人量50倍以上）会影响仔鼠大脑锥体细胞的发育,进而阻碍脑的发育。     

Laminar cortical necrosis in mitochondrial disorders

Objectives

Laminar cortical necrosis, defined as focal or diffuse necrosis of one or more cortical lamina, represents an increasingly recognized neuropathological endpoint of vascular, endocrine, immunologic, metabolic, or toxic conditions, of which mitochondrial disorders (MIDs) are the third most frequent after cerebral ischemia and hypoxia.

Aims

To investigate the prevalence of laminar cortical necrosis in MIDs, types of MIDs associated with laminar cortical necrosis, and the morphological characteristics on imaging and autopsy.

Methods

Medline literature review for the terms “laminar cortical necrosis”, “cortical signal change”, “mitochondrial” and all acronyms of syndromatic MIDs.

Results

Among 139 hits for “laminar cortical necrosis”, 10 articles fulfilled the inclusion criteria (7%). Among the ten hits five were case series and the other five single case reports. The syndromic MID most frequently associated with laminar cortical necrosis is the MELAS syndrome, but was also described in a single patient each with Leigh syndrome, mitochondrial depletion syndrome, and mitochondrial spinocerebellar ataxia. The morphological and pathohistological features of laminar cortical necrosis in MIDs were not at variance from those in non-mitochondrial disorders.

Conclusions

In MIDs laminar cortical necrosis represents the histopathological and imaging endpoint of a stroke-like lesion. Though laminar cortical necrosis may have a wide pathophysiological background the histological and imaging characteristics do not vary between the different underlying conditions.     

尼莫地平和灯盏花改善饮酒致脑功能损伤的实验研究

目的：探讨尼莫地平、灯盏花对饮酒致脑功能损伤的保护作用。方法：Wistar大鼠按饮酒剂量及保护药物随机分为9组,包括对照组、饮酒组、饮酒＋药物保护组;于饮酒后第14 d取脑组织,检测组织匀浆中丙二醛（MDA）、谷胱甘肽过氧化物酶（GSH-Px）含量的变化以及小脑、海马组织多巴胺受体3（D3R）和谷氨酸受体1（GluR1）表达的变化。结果：保护组脑组织匀浆中MDA明显低于饮酒组（P〈0.01）,各保护组D3R和GluR1的表达比饮酒组弱。结论：尼莫地平和灯盏花对饮酒所致脑功能损伤可能具有一定的改善作用。     

Distribution of freed-serine in vertebrate brains

Freed-serine distribution in vertebrate brains was investigated. In various brain regions of the lower vertebrate species, carp, frog and chick, freed-serine levels were low. On the contrary, in the mammals, mouse, rat and bull, the contents of freed-serine were high in the forebrain (around 400 nmol/g wet weight, and the ratio ofd-serine tol-serine, was d/l = 0.4), and low in the hindbrain. In developing mice,d-serine levels in the cerebrum increased with age and attained the adult level (d/l = 0.40) 8 weeks after birth. In the cerebellum and brain stem, the freed-serine levels increased with age until 2 weeks, followed by a decrease to the adult levels: thed/l ratios remained constant until 2 weeks of age, then decreased to 0.03 in the cerebellum and 0.12 in the brain stem. Freed-serine was shown not to be of microbial origin using germ-free mice. In the rat forebrain,d-serine was evenly distributed in two cerebral regions, namely frontal and occipital lobes. Thed/l ratios in other regions of forebrain, hippocampus and hypothalamus, were comparable to the cerebrum (d/l = 4), while that in the olfactory bulb was lower (d/l = 0.12). In the rat cerebrum, thed-serine content in the grey matter was significantly higher than that in the white matter. The contents of freed-serine in bovine cerebrum and cerebellum were similar to those in other mammalian brains, but thed/l ratio for bovine cerebral grey matter was lower than that for the cerebral white matter. Thed-serine level was discussed in terms ofd-amino-acid oxidase activity.     

A case of ectopic parasitism: Fasciola hepatica larvae burrow through a human brain and mimic cerebral aneurysm

An 8-year-old boy from Xuan-Han County, Sichuan Province, China presented with 6 months headache, nausea and vomiting. A computed tomography scan revealed multiple cerebral hemorrhages. Etiology of the cerebral hemorrhages was investigated by digital subtraction angiography, and cerebral aneurysm was entertained. Twenty-six days after his admission to the hospital, a flatworm emerged from the right eye of the patient. The worm was identified as Fasciola hepatica, based on the morphological characteristics of the worm.