树鼩(Tupaia belangeri chinensis)的脑底动脉环

用25只树鼩,从升主动脉灌注带色的橡胶乳液,在解剖显微镜下进行解剖观察,用目测微尺进行测量。大多数树鼩(22只)有完整的脑底动脉环。由左、右大脑前动脉向内侧各发一前交通动脉组成大脑前总动脉。前交通动脉口径为大脑前动脉的75～85％。后交通动脉口径与大脑后动脉相近,连于颈内动脉与大脑后动脉(基底动脉的分支)之间。测量了组成脑底动脉环有关动脉的口径。由于后交通动脉足够粗大,只有中断左、右颈总动脉和左、右椎动脉,才能造成全脑缺血。     

An Improved Method for In Situ Freezing of Cat Brain for Metabolic Studies

This study introduces a new method for rapid freezing of the cat brain. The method employed a Styrofoam box which was fitted around the head of the animal. Liquid nitrogen was poured into the box until the head was submerged. Temperature changes in three brain sites (ventral hypothalamus, the fourth ventricle, and the corpus callosum) and levels of labile carbohydrate metabolites (glycogen, glucose, ATP, P-creatine, and lactate) in five brain regions (cortex, thalamus, midbrain, cerebellum, and pons) frozen by the box method were compared with those frozen by a conventional cup method in which liquid nitrogen was poured into a hollow Styrofoam cup placed on top of the skull. The box method shortened the time of arrival of the freezing front and improved the freezing rate. The time required to bring the tissue to -20 degrees C was shortened, from 20 min at the ventral hypothalamus and 10-12 min at the fourth ventricle with the cup method, to less than 5 min at both sites with the box technique. Continued perfusion of brainstem prior to freezing was demonstrated. Levels of metabolites frozen by either method were similar. Lactate levels in any of the five brain regions studied by either method were not elevated, indicating no ischemic change.(ABSTRACT TRUNCATED AT 250 WORDS)     

Evidence for Differing Origins of the Serotonergic Innervation of Major Cerebral Arteries and Small Pial Vessels in the Rat

We have studied the nature and origin of the serotonergic innervation of two distinct anatomical cerebrovascular compartments, namely, small pial vessels and major cerebral arteries, in the rat. To this end, the levels of serotonin [5-hydroxytryptamine (5-HT)] and 5-hydroxyindoleacetic acid (5-HIAA) were measured by HPLC in both cerebrovascular compartments after either bilateral sympathectomy or destruction of the ascending serotonergic pathways, which originate from the raphe nuclei. We first showed that the small pial vessel samples were not contaminated by underlying cortical tissues through the use of an immunohistochemical approach that revealed the glia limitans, the most superficial cortical layer. Superior cervical ganglionectomy caused a marked decrease in noradrenaline concentrations in major cerebral arteries (-77%), although the reduction was less pronounced (-34%) in small pial vessels. Sympathectomy decreased by 33% 5-HT concentrations in the major cerebral arteries but was without effect on 5-HT levels in the small pial vessels. Destruction of the ascending serotonergic pathways (via local administration of 5,7-dihydroxytryptamine into the ventral tegmental area) produced a dramatic fall in 5-HT and 5-HIAA concentrations in both vascular compartments. To establish the authenticity of the serotonergic innervation, the synthesis of 5-HT [as assessed by measuring the accumulation of 5-hydroxytryptophan (5-HTP) after decarboxylase inhibition] was measured in the two vascular beds under control conditions and after destruction of the ascending serotonergic pathways. The rate of accumulation of 5-HTP was higher in the small pial vessels than in major cerebral arteries, an observation that indicates an important de novo synthesis of 5-HT in small pial vessels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of Selective Brain Hypothermia on Regional Cerebral Blood Flow and Tissue Metabolism Using Brain Thermo-Regulator in Spontaneously Hypertensive Rats

To investigate the effect of selective hypothermia of the brain (brain cooling) on regional cerebral blood flow and tissue metabolism, we have developed a brain thermo-regulator. Brain temperature was modulated by a water-cooled metallic plate placed on the surface of the rats' scalp to get the appropriate brain temperature precisely with ease. Regional cerebral blood flow and brain temperature were measured simultaneously using a Teflon-coated platinum electrode and thermocouple probe inserted stereotaxically into the parietal cortex and thalamus in spontaneously hypertensive rats. Experimental forebrain ischemia was induced by the occlusion of bilateral common carotid artery under normo- and hypothermic brain condition, and the supratentorial brain tissue metabolites were measured enzymatically after 60 min of forebrain ischemia. When cortical temperature was set to hypothermia, cortical blood flow was significantly lowered by 40% at 30°C and 20% at 33°C as compared with that at 36°C (p < 0.0001 and p < 0.05, respectively). Thalamic blood flow was also significantly reduced by 20% when cortical temperature was set to 30°C as compared with 36°C (p < 0.05). There were no significant differences in arterial blood pressure and gas parameters throughout these experiments. In the rats with selective brain hypothermia (30°C) immediately after the induction of cerebral ischemia, the level of brain ATP concentration after 60 min of ischemia was significantly higher than that in normothermia rats (36°C) (p < 0.05). Our findings indicate that: 1) the metallic plate brain thermo-regulator is useful in small animal experiments; 2) regional brain temperature regulates regional cerebral blood flow; and 3) selective brain hypothermia, even started after the forebrain ischemia, ameliorates the derangement of brain metabolism, suggesting its effectiveness as a cytoprotective strategy.     

On the presence of neurotrophin p75 receptor on rat sympathetic cerebrovascular nerves

Although the presence of neurotrophin p75 receptor on sympathetic nerves is a well-recognised feature, there is still a scarcity of details of the distribution of the receptor on cerebrovascular nerves. This study examined the distribution of p75 receptor on perivascular sympathetic nerves of the middle cerebral artery and the basilar artery of healthy young rats using immunohistochemical methods at the laser confocal microscope and transmission electron microscope levels. Immunofluorescence methods of detection of tyrosine hydroxylase (TH) in sympathetic nerves, p75 receptor associated with the nerves, and also S-100 protein in Schwann cells were applied in conjunction with confocal microscopy, while the pre-embedding single and double immunolabelling methods (ExtrAvidin and immuno-gold-silver) were applied for the electron microscopic examination. Immunofluorescence studies revealed “punctuate” distribution of the p75 receptor on sympathetic nerves including accompanying Schwann cells. Image analysis of the nerves showed that the level of co-localization of p75 receptor and TH was low. Immunolabelling applied at the electron microscope level also showed scarce co-localization of TH (which was intra-axonal) and p75. Immunoreactivity for p75 receptor was present on the cell membrane of perivascular axons and to a greater extent on the processes of accompanying Schwann cells. Some Schwann cell processes were adjacent to each other displaying strong immunoreactivity for p75 receptor; immunoreactivity was located on the extracellular sites of the adjacent cell membranes suggesting that the receptor was involved in cross talk between these. It is likely that variability of locations of p75 receptor detected in the study reflects diverse interactions of p75 receptor with axons and Schwann cells. It might also imply a diverse role for the receptor and/or the plasticity of sympathetic cerebrovascular nerves to neurotrophin signalling.     

1D simulation of blood flow characteristics in the circle of Willis using THINkS

One-dimensional (1D) simulation of the complete vascular network, so called THINkS (Total Human Intravascular Network Simulation) is developed to investigate changes of blood flow characteristics caused by the variation of CoW. THINkS contains 158 major veins, 85 major arteries, and 77 venous and 43 arterial junctions. THINkS is validated with available in vivo blood flow waveform data. The overall trends of flow rates in variations of the CoW, such as the missing anterior cerebral artery (missing-A1) or missing posterior cerebral artery (missing-P1), are confirmed by in vivo experimental data. It is demonstrated that the CoW has the ability to shunt blood flow to different areas in the brain. Flow rates in efferent arteries remain unaffected under the variation of CoW, while the flow rates in afferent vessels can be subject to substantial changes. The redistribution of blood flow can cause particular vessels to undergo extra flow rate and hemodynamic stresses.     

Day-night cycle of lipidic composition in rat cerebral cortex

A study of the lipidic pattern of the cerebral cortex of the normal adult rat during the daynight cycle was carried out. The changes observed were the following: phosphatidylcholine, phosphatidylethanolamine, phosphatidylinositol and phosphatidylserine plus phosphatidic acid showed a peak at 16:00 hr possibly due to a general increase in phospholipid biosynthesis. During the nocturanl period the variations of phosphatidylcholine and phosphatidylethanolamine were not clearly observe, they might be due to an increase in the interconversion or exchange reaction, since the ratio phosphatidylcholine/phosphatidylethanolamine showed a significative change at 04:00 hr. This occurred because small but opposite changes in both phospholipids were observed, suggesting an increase in the methylation reactions of phospholipids. Cardiolipin showed a significant peak at 04:00 hr. Plasmalogens exhibited significative changes, an important diminution at 16:00 hr and a prominent peak at 24:00 hr. Cholesterol levels were high during the light period and low in the dark one. Cerebrosides and gangliosides showed no day-night variations. The changes observed indicate a phenomenon of biological rhythmicity synchronized by the photoperiod, suggesting that these fluctuations could act as physiological modulators of the properties and functions of the nerve cell membrane.     

Distribution and dilatory effect of vasoactive intestinal polypeptide (VIP) in human cerebral arteries

Vasoactive intestinal polypeptide (VIP)-containing nerve fibers were demonstrated in human pial arteries by immunocytochemistry. Fine varicose fibers were located in the adventitia close to the media layer. Measurements by radioimmunoassay revealed concentrations of VIP between 0.7 and 2.7 pmol/g in the major arteries at the base of the brain, obtained at autopsy. Isolated human pial arteries, obtained in conjunction with neurosurgery, relaxed in a concentration-dependent manner upon administration of VIP. The relaxation of the vessels amounted to 57 +/- 9% of the contraction elicited by prostaglandin F2 alpha (2.5 microM) with an EC50 value of (8.5 +/- 1.2) X 10(-9) M.     

Contribution of the vertebral artery to cerebral circulation in the rat snake Elaphe obsoleta

Blood supplying the brain in vertebrates is carried primarily by the carotid vasculature. In most mammals, cerebral blood flow is supplemented by the vertebral arteries, which anastomose with the carotids at the base of the brain. In other tetrapods, cerebral blood is generally believed to be supplied exclusively by the carotid vasculature, and the vertebral arteries are usually described as disappearing into the dorsal musculature between the heart and head. There have been several reports of a vertebral artery connection with the cephalic vasculature in snakes. We measured regional blood flows using fluorescently labeled microspheres and demonstrated that the vertebral artery contributes a small but significant fraction of cerebral blood flow (∼13% of total) in the rat snake Elaphe obsoleta. Vascular casts of the anterior vessels revealed that the vertebral artery connection is indirect, through multiple anastomoses with the inferior spinal artery, which connects with the carotid vasculature near the base of the skull. Using digital subtraction angiography, fluoroscopy, and direct observations of flow in isolated vessels, we confirmed that blood in the inferior spinal artery flows craniad from a point anterior to the vertebral artery connections. Such collateral blood supply could potentially contribute to the maintenance of cerebral circulation during circumstances when craniad blood flow is compromised, e.g., during the gravitational stress of climbing. J. Morphol. 238:39–51, 1998. © 1998 Wiley-Liss, Inc.     

孕酮对缺血／再灌注大鼠脑皮层水肿的影响

目的探讨孕酮(progesterone,PROG)对脑水肿的影响.方法48只大鼠随机分为6组即缺血/再灌(I/R)组,二甲基亚砜(DMSO)组,预防(pretreatment)组,防治(pre+posttreatment)组,治疗(posttreatment)组,地塞米松(DEXA)组.采用大鼠局灶性脑缺血/再灌注(I/R)模型,测定大脑中动脉阻塞(MCAO)24h后脑皮层水、钠、钾、钙含量.结果与DMSO组相比,应用PROG预防及防治组均能明显降低缺血皮层的H2O(P＜0.01)、Na+(P＜0.01)、Ca2+(P＜0.01)含量,升高K+(P＜0.01)含量,而治疗组虽能明显降低H2O(P＜0.05)、Na+(P＜0.01),但降低Ca2+(P>0.05)和升高K+(P＞0.05)的效果不显著.DEXA组的结果与PROG预防或防治组类似.结论用PROG预防或防治能显著减轻I/R引起的脑水肿.     

Developmental changes and regional distribution of phospholipase D and base exchange enzyme activities in rat brain

Phospholipase D (PL-D) activity per mg protein of whole homogenate increased 5.1 fold between Embryonic (E) day 17 and Postpartum (P) day 14 and slightly decreased by P 30 days. This was due to the decrease of PL-D activity of the P₂ fraction. The PL-D activity of P₂ and P₃ fractions increased 11.2 and 6.1 fold respectively between E 17 and P 14. The 3 base exchange enzyme (BEE) activities per mg protein of whole homogenate increased up to P 14 or P 21 and then decreased. This decrease was greater in the P₂ fraction and the P₃ fraction increased after P14. Brains from 1 day to 25 month old rats were dissected into 7 separate regions and both PL-D and BEE activities were measured. In adult rats, the hippocampus and hypothalamus had the highest PL-D activities while medulla+pons and cerebellum had the lowest PL-D activities. The developmental patterns of 5 regions except for hippocampus and hypothalamus were similar. PL-D activity in the hippocampus was maximum at P 7 followed by a steep decrease till P30 suggesting that the PL-D activity of the hypothalamus develops later and that of the hippocampus develops earlier than any other region. The distributions of BEE activities were quite different from those of PL-D activities. In adult rats, the cerebellum had the highest activity while the striatum and medulla+pons had the lowest. The BEE activities of cerebellum were lowest at P 1 and showed steep increase during the next 2 weeks.To whom to address reprint request are to be sent.     

Dietary astaxanthin can accumulate in the brain of rats

We evaluated the distribution of astaxanthin in rat brains after a single dose administration and after feeding 0.1% astaxanthin diet for 5 days. Astaxanthin was detected in the hippocampus and cerebral cortex 4 and 8 h after a single dose. Astaxanthin concentration in rat brains was higher after consumption of astaxanthin diet for 5 days than after a single dose.     

Invited review: Genomic selection for small ruminants in developed countries: how applicable for the rest of the world?

Improved management and use of estimated breeding values in breeding programmes, have resulted in rapid genetic progress for small ruminants (SR) in Europe and other developed countries. The development of single nucleotide polymorphisms chips opened opportunities for genomic selection (GS) in SR in these countries. Initially focused on production traits (growth and milk), GS has been extended to functional traits (reproductive performance, disease resistance and meat quality). The GS systems have been characterized by smaller reference populations compared with those of dairy cattle and consisting mostly of cross- or multi-breed populations. Molecular information has resulted in gains in accuracy of between 0.05 and 0.27 and proved useful in parentage verification and the identification of QTLs for economically important traits. Except for a few established breeds with some degree of infrastructure, the basic building blocks to support conventional breeding programmes in small holder systems are lacking in most developing countries. In these systems, molecular data could offer quick wins in undertaking parentage verification and genetic evaluations using G matrix, and determination of breed composition. The development of next-generation molecular tools has prompted investigations on genome-wide signatures of selection for mainly adaptive and reproduction traits in SR in developing countries. Here, the relevance of the developments and application of GS and other molecular tools in developed countries to developing countries context is examined. Worth noting is that in the latter, the application of GS in SR will not be a ‘one-size fits all’ scenario. For breeds with some degree of conventional genetic improvement, classical GS may be feasible. In small holder systems, where production is key, community-based breeding programmes can provide the framework to implement GS. However, in fragile growth systems, for example those found in marginal environments, innovative GS to maximize adaptive diversity will be required. A cost-benefit analysis should accompany any strategy of implementing GS in these systems.