A QUANTITATIVE STUDY OF VASCULAR PERMEABILITY TO HORSERADISH PEROXIDASE, AND THE SUBSEQUENT FATE OF THE TRACER, IN RAT BRAINS AFTER PORTOCAVAL ANASTOMOSIS

Sumner B. E. H. (1982) Neuropathology and Applied Neurobiology 8, 117–133
A quantitative study of vascular permeability to horseradish peroxidase, and the subsequent fate of the tracer, in rat brains after portocaval anastomosis
Labelled blood vessel segments, exudation patches, and pericytic granular cells were counted in sections of rat brain which had been fixed and tested with DAB from 3 min to 24 h after intravenous injection of horseradish peroxidase (HRP).
In normal rats, 3 min after injection, only 1% of the total blood vessel segments had walls penetrated by HRP, but in rats 14 days after portocaval anastomosis (PCA) 44% of the total segments had labelled walls, a frequency of 3033 permeable segments/mm³ of brain. In normal rats no exudation patches were found, but after PCA there were seven patches/mm³ of brain. Maximum vascular wall labelling and maximum exudation occurred in the cerebellum and medulla of the operated rats. Hardly any pericytic cells were labelled 3 min after injection.
In operated rats 2 h after injection of HRP, labelled vascular walls were fewer and exudation had disappeared, but 204 pericytic cells/mm³ of brain contained HRP-labelled granules, i.e. 60% of the total pericytes. Highest numbers were found in the most anterior section of the brain sample. Later after injection these numbers declined.
It is suggested that most of the protein which leaked into the brain after PCA returned to the blood whence it came, but that some was captured and hydrolysed by the granular pericytes.     

CEREBRAL ISCHAEMIA IN THE RAT: INCREASED PERMEABILITY OF POST-SYNAPTIC MEMBRANES TO HORSERADISH PEROXIDASE IN THE EARLY POST-ISCHAEMIC PERIOD

An earlier study of the rat hippocampal stratum radiatum after transient cerebral ischaemia has shown cell membrane breaks, mainly post-synaptically, occurring as early as 20 min after an ischaemic episode. In the present study HRP was injected into the lateral ventricle 10-15 min after ischaemia and allowed to diffuse until 60 min post-ischaemia. Ultrastructural examination in the control animals, showed that HRP was localized exclusively in the extracellular space. After 10 min of transient ischaemia, HRP was not confined to the extracellular space, but was also seen in about 10% of apical dendrites. Only a very few pre-synaptic terminals showed the presence of HRP. Thus, there is evidence of early post-ischaemic membrane damage occurring in vivo in the apical dendrites of the CA-1 pyramidal cells.     

THE MITOCHONDRIAL CONTENT OF ENDOTHELIAL CELLS AND THE BASEMENT MEMBRANE THICKNESS OF RAT BRAIN CAPILLARIES AFTER PORTOCAVAL ANASTOMOSIS

Laursen H. (1980) Neuropathology and Applied Neurobiology 6,375–386
The mitochondrial content of endothelial cells and the basement membrane thickness of rat brain capillaries after portocaval anastomosis
The volume of mitochondria in brain capillary endothelium and the harmonic mean basement membrane thickness were estimated in rats after portocaval anastomosis for 10 days, 30 days and 10 weeks. The mitochondrial volume was from 5–73% to 7–64% of the endothelial volume. There was no difference between the control and experimental animals. The harmonic mean thickness of the basement membrane was calculated from orthogonal intercepts measured on a reciprocal logarithmic scale. This method leads to an approximately normal distribution of the measurements. The harmonic mean thickness was 57–8 nm in controls, 54–6 nm after 10 days, 63–2 nm after 30 days and 600 nm after 10 weeks portocaval anastomosis. The increase after 30 days was significantly different from the first two measurements. It is concluded that only a small increase in harmonic mean thickness of the basement membrane, and thereby an increase in diffusion resistance, have occurred after 30 days portocaval anastomosis.     

REGIONAL NEURONE DAMAGE AFTER CEREBRAL ISCHAEMIA IN THE NORMO- AND HYPOGLYCAEMIC RAT

Ten minutes of total cerebral ischaemia was produced in normo- and hypoglycaemic rats. The most conspicuous findings were loss of hippocampal (CA-1) pyramidal cells and Purkinje cells, which were most pronounced in the normoglycaemic rats. While pre-ischaemic hypoglycaemia to some extent protected these cells, it led to infarction or severe ischaemic nerve cell changes in the brain stem nuclei and lowered the neurological restitution of the hypoglycaemic animals. The regional damage in these rats, which were kept normotensive after ischaemia, was not due to circulatory insufficiency. However, rats with untreated spontaneous low blood pressure in the early postischaemic period showed multiple small infarcts.     

CHANGES IN RAT CEREBRAL MITOCHONDRIAL SUCCINATE DEHYDROGENASE ACTIVITY AFTER BRAIN TRAUMA

The objective of this study was to evaluate 2,3,5-triphenyltetrazolium chloride (TTC) staining in the brain tissue of rats submitted to a closed head traumatic injury, in comparison to control rats not submitted to trauma. The closed head, weight drop trauma model described by Marmarou et al. (1994) was used. Animals were all sacrificed 24 h after trauma. Staining of cerebral coronal slices using TTC, coupled to image analysis software, was used to measure the level of staining. An ultrastructural study of the brain region underneath the impact zone, as well as from the correspondent region of control rats, was also done. The TTC image analysis revealed a significant decrease in the percentage of white area, in traumatized rats (mean ± SEM 23.93% ± 2.26, n = 4 for control, 12.13% ± 1.72, n = 9 for traumatized rats, p < .05). The ultrastructural analysis revealed that the number of axons showing at least one mitochondrion was significantly higher in the trauma group (mean ± SEM 49.3%, n = 4 rats, 75 photographs, 2443 axons) than in control groups (23%, n = 3 rats, 30 photographs, 6220 axons (p < .001). Another difference observed was the larger mitochondrial size in the axons of traumatized rats (mean diameter ± SEM 0.520 ± 0.003 μm) compared to the controlled rats (0.368 ± 0.006 μm; p < .001). The ultrastructural observation of the traumatized brain revealed a significantly higher number of peroxisomes per photograph (mean number ± SEM 10.58 ± 1.18, n = 75) compared to the control group (0.19 ± 0.08, n = 30, p < .001). The results indicate an increase of mitochondrial and peroxysomal relative mass, with a higher succinate dehydrogenase activity, 24 h after the induction of traumatic brain injury     

THE CEREBROVASCULAR PERMEABILITY TO PROTEIN AFTER BICUCULLINE AND AMPHETAMINE ADMINISTRATION IN SPONTANEOUSLY HYPERTENSIVE RATS

Hemodynamic and morphometric studies on spontaneously hypertensive rats (SHR) have suggested that the lumen to wall ratio of the resistance vessels is decreased due to hypertrophy of the media. As the tension in the vessel wall increases with the pressure and the radius and decreases with the vessel wall thickness, such vessels would be expected to withstand higher pressure than vessels of normotensive rats (NR) unless local wall defects were present. Bicuculline-induced epileptic activity and amphetamine intoxication, two conditions with cerebral vasodilatation and high blood pressure, give rise to extensive protein leakage in the brain of NR. Consistent with the hypothesis presented above, less protein leakage occurred in brains of SHR than in brains of NR after amphetamine and bicuculline administration.     

THE EARLY ULTRASTRUCTURAL ALTERATIONS IN THE RABBIT CEREBRAL AND CEREBELLAR CORTEX AFTER COMPRESSION ISCHAEMIA

The early ultrastructural alterations in the rabbit cerebral and cerebellar cortex after compression ischaemia
The ultrastructural alterations in the rabbit cerebral and cerebellar cortex resulting from 30 minutes complete, permanent cerebral ischaemia were studied. The ischaemia was induced by raising the intracranial pressure (ICP) above the systolic arterial pressure (compression ischaemia). Immediately after releasing the ICP the brain was fixed by intravascular glutaraldehyde perfusion. Samples from the cerebral and cerebellar cortex were processed for electron microscopy. The ultrastructural changes were relatively minor; there was a generalised, slight intracellular oedema, most prominent in the subpial area; the nuclear chromatin was clumped, the endo. plasmic reticulum and cisternae of the golgi apparatus became somewhat dilated, the inner matrix of the slightly swollen mitochondria showed increased electron lucency, and microtubules and ribosomes began to loose their compact structure. These changes, unaccompanied by any extensive volumetric change of any cellular compartment, agree well with the recently presented hypothesis of two different types of anoxic-ischaemic nerve cell injury. This cellular reaction to complete, permanent compression ischaemia represents the type of injury that is seen resulting from ischaemic insults during which no flow of fluid irrigates the ischsemically injured cells.     

A QUANTITATIVE STUDY OF AGE-RELATED CHANGES IN THE VASCULAR ARCHITECTURE OF THE RAT CEREBRAL CORTEX

Wilkinson J.H., Hopewell J.W. & Reinhold H.S. (1981) Neuropathology and Applied Neurobiology 7, 451–462
A quantitative study of age-related changes in the vascular architecture of the rat cerebral cortex
A quantitative study of age related changes in the vascular architecture of the rat cerebral cortex is described. A special vessel-filling technique, which allowed the simultaneous fixation of the vasculature, aided the identification of the vessels in histological sections. Vascular parameters, which included the total number of vessel fragments, a blood volume and a vessel wall-surface area index were obtained using a Quantimet 720 shape-analysing computer. In animals aged 13–83 weeks, there was an increase in the above vascular parameters which could mainly be attributed to an increase in the number of vessels with a diameter > 8 μm. In very old rats, aged 124 weeks, the vascularity of the cerebral cortex was severely reduced. These changes, which are very similar to those reported in the ageing human cerebral cortex, may be explained by either direct or indirect effects on the cerebral vasculature. Possible mechanisms are discussed in relation to similar changes observed in the cerebral vasculature after several different insults.     

THE TOXICITY TO RAT CEREBRAL CORTEX OF TOPICAL APPLICATIONS OF ACETALDEHYDE, AMMONIA OR BILIRUBIN

The relative toxicity of acetaldehyde, ammonia and bilirubin to cerebral cortex of rats has been tested by supervision of the intact dura for 1 h with each toxin separately. The cortex was examined histologically after 6 days survival using a silver stain which selectively impregnates degenerating axons and their synaptic terminals. A tissue concentration of 30 mM acetaldehyde was found to cause axonal and terminal degeneration, whereas 11 mM acetaldehyde was not toxic, and did not produce any structural changes detectable by electron microscopy. In terms of tissue concentrations, acetaldehyde was at least 27 times more toxic than ethanol on a molar basis. However, the acetaldehyde concentration necessary to produce neuronal degeneration in a 1 h exposure is many times greater than ever reported in CSF in human alcoholism. Both ammonia and bilirubin are capable of causing neuronal degeneration, but we have not measured the tissue concentrations that are toxic. Comparison of molar concentrations in the supervising fluids showed that ammonia is at least 39 times more toxic than acetaldehyde, and at least 1000 times more toxic than ethanol. Superfusion with an ethanolic solution of bilirubin (2–5 mM) was strongly toxic, but this solution diluted to 50% with saline was not toxic. The possibility exists that ammonia or bilirubin may reach concentrations toxic to neurons in alcoholism, especially in the presence of liver damage.     

THE PROTEOGLYCAN DSD-1-PG OCCURS IN PERINEURONAL NETS AROUND PARVALBUMIN-IMMUNOREACTIVE INTERNEURONS OF THE RAT CEREBRAL CORTEX

Proteoglycans involved in the shaping of the developing brain are often preserved in the adult brain in more restricted locations. We have studied the fate of DSD-1-PG, a chondroitin sulfate proteoglycan containing the hybrid epitope DSD-1. DSD-1-PG exerts neurite outgrowth promoting activity and has been shown to occur in the developing brain during late brain development and into adulthood. In the adult rat brain, monoclonal and polyclonal antibodies against DSD-1-PG labelled only the circumference of a selected subpopulation of neurons. These nerve cells invariably expressed the calcium-binding protein parvalbumin. The label occupied the extracellular space in close vicinity to the cell body, surrounding axon terminals and glial end feet, but was absent from synaptic clefts. DSD-1-PG is thus shown to be an additional representative of the growing list of substances found in perineuronal locations in the adult mammalian brain. Copyright © 1996 ISDN. Published by Elsevier Science Ltd.     

COMPLETE CEREBRAL ISCHAEMIA IN THE RAT: AN ULTRASTRUCTURAL AND STEREOLOGICAL ANALYSIS OF THE DISTAL STRATUM RADIATUM IN THE HIPPOCAMPAL CA-1 REGION

Ekström von Lubitz D.K.J. & Diemer N.H. (1982) Neuropathology and Applied Neurobiology 8, 197–215
Complete cerebral ischaemia in the rat: an ultrastructural and stereological analysis of the distal stratum radiatum in the hippocampal CA-1 region
An ultrastructural study and a stereological analysis of the distal stratum radiatum in the hippocampal CA-1 region of the rat were performed after 10 min of complete cerebral ischaemia followed by 10, 20 and 60 min of blood reflow periods. Post-ischaemic changes were mainly limited to the region of synaptic terminals which showed either clumping or dispersion of the synaptic vesicle pools and damage to synaptic membranes. Presynaptic terminals and astrocytes were swollen after 10 and 20 min of reflow, but this abated after 60 min. Mitochondria in neurons showed varying degrees of swelling, but in astrocytes their structure was normal. There were no changes in capillaries. After 20 and 60 min of blood reflow, disruption of cell membranes was observed, mainly in the vicinity of the synaptic terminals. The size of the extracellular space diminished by approximately 30% in all three ischaemic groups. The data show that synaptic terminals are a primary and early target in the development of postischaemic nerve cell damage.     

THE EFFECT OF ISCHEMIA ON THE PERMEABILITY OF THE PERINEURIUM TO PROTEIN TRACERS IN RABBIT TIBIAL NERVE

The influence of ischemia on the permeability of the perineurium to protein tracers was studied in rabbit tibial nerve. Intravital ischemia was produced by a pneumatic cuff around the thigh and the effects of long-lasting permanent ischemia were investigated in postmortem experiments. The permeability was tested fluorescence microscopically by injections of albumin labelled with Evan's blue (EBA) around the nerve. The diffusion of EBA into the endoneurium of control tibial nerves was prevented by the perineurium. This “barrier” function of the perineurium resisted ischemia of even 24 hours’duration but after 48 hours of ischemia the tracer penetrated the perineurium and spread widely in endoneurial spaces. This diffusion barrier is therefore markedly resistant to ischemia and postmortem changes.     

大鼠中脑导水管周围灰质向孤束核的直接投射

用ＰＨＡ－Ｌ和ＷＧＡ－ＨＲＰ顺行追踪方法,对大鼠中脑导水管周围灰质（ＰＡＧ）向孤束核的投射进行了研究。结果如下：（１）ＰＨＡ－Ｌ和ＷＧＡ－ＨＲＰ顺标纤维和终末在孤束核内的分布状态基本一致,内侧亚核最多,连合亚核、腹外侧亚核和腹侧亚核次之,中间亚核内最少。无论注射区在ＰＡＧ的尾段还是吻段,孤束核的尾中段内的标记纤维和终末均多于吻段。（２）ＰＡＧ尾段向孤束核的投射多于ＰＡＧ吻段。（３）ＰＡＧ腹外侧区向孤束核的投射较多,而背外侧区较少（尾段）或缺如（吻段）。根据作者过去的结果和本实验证据,可见ＰＡＧ向孤束核的投射通路存在定位投射关系。     

THE CONTUSION INDEX: A QUANTITATIVE APPROACH TO CEREBRAL CONTUSIONS IN HEAD INJURY

Adams J.H., Scott G., Parker L.S., Graham D.I. & Doyle D. (1980)
Neuropathology and Applied Neurobiology 6, 319–324
The contusion index: a quantitative approach to cerebral contusions in head injury
A quantitative means of assessing contusions of the brain (the 'contusion index') following head injury has been devised. Its derivation and application to a consecutive series of 151 cases are described.     

THE EVOLUTION OF INTRACELLULAR RESPONSES TO ACRYLAMIDE IN RAT SPINAL GANGLION NEURONS

Acrylamide (30 mg or 50 mg/kg/day, 5 days each week) was injected intraperitoneally into rats for up to 4 weeks. Lumbar spinal ganglia, spinal cord and lumbrical muscle spindles were examined by light and electron microscopy at various times during this period. The first abnormalities in spinal ganglion neurons were seen at 7 days when an apparent increase in numbers of mitochondria, some being hypertrophic, were found in a few large light cells. This was 10 days before any significant Wallerian degeneration was found in muscle spindle sensory fibres. Mitochondrial changes became more marked with time and were later associated with RER disruption, loss of neurofilaments and peripheral displacement of the nucleus thus mimicking chromatolysis of the axon reaction. All these changes began, however, before axon degeneration. Evidence of increased satellite cell activity was maximal at 21 days. These changes are discussed in the light of the possibility that calcium entry into the cell may be seriously increased early in the intoxication as a direct result of the presence of acrylamide and that many of these cellular features are secondary responses to such an event. Distal degeneration of axons seems likely to be secondary to the perikaryal changes.     

投射到垂体后叶的室管膜下神经元丛电镜研究

在电子显微镜下观察了大鼠前部第三脑室和室门孔室管膜下方的投射到垂体后叶的神经元和树突，以及这些神经元胞体和树突与室管膜之间的关系。部分ＨＲＰ—ＴＭＢ标记的室管膜下神经元胞体和树突距室管膜细胞基底面仅相隔数层细胞膜，有少数树突或胞体与室管膜细胞直接接触；有的走行在室管膜细胞之间，距室腔仅隔１００ｎｍ的距离。室管膜下标记神经元胞休或树突大数有突触与之接触。部分突触前膨大内也见有标记产物，可与标记树突或家标记树突形成突触。一些标记树突可伸至室周毛细血管壁基膜下方．