唐鱼脑的组织形态学观察

应用光镜技术观察了唐鱼(Tanichthys albonubes)脑的形态学和组织学结构。结果表明,唐鱼脑基本结构与多数硬骨鱼类相一致,包括端脑、间脑、中脑、小脑及延脑五部分,端脑由嗅囊、嗅叶和大脑构成。脑的组织形态学特点为:嗅叶及嗅囊分化较明显,大脑呈长椭圆状,仍保留鲤科(Cyprinidae)鱼类脑的原始特征;间脑背面具一松果体,腹面中央有一心形漏斗,前端连接呈鸡心形的脑垂体;中脑视叶膨大,与视觉发达相关;小脑发达,与其活跃的生活习性相适应;延脑前部稍稍隆起。此外,对唐鱼脑保持硬骨鱼类较原始的结构特点及其生态学意义进行了探讨。     

版纳鱼螈和双带鱼螈核型的比较研究

本文对版纳鱼螈的核型作了观察,并与双带鱼螈进行了比较。两者的核型基本一致,均为2n=42,但版纳鱼螈的NF=62,而双带鱼螈的NF=60;版纳鱼螈的染色体有中部着丝粒、亚中部着丝粒和端部着丝粒三种类型,而双带鱼螈则无亚中部着丝粒的染色体。     

基于线粒体细胞色素b基因序列的版纳鱼螈四个种群遗传多样性与遗传结构研究

版纳鱼螈Ichthyophis bannanicus 是蚓螈类在我国分布的唯一物种,目前已知分布在云南、广西和广东的部分地区.本研究获得4个版纳鱼螈种群的87个个体的线粒体DNA细胞色素6基因1 000 bp序列,对序列变异、遗传多样性、种群结构和种群动态进行了分析.经比对后87个序列发现39个(3.9%)多态性位点,共定义了22个单倍型.序列分析结果显示版纳鱼螈种群单倍型多样性和核苷酸多样性与其它两栖动物接近,说明版纳鱼螈各种群仍保持一定的遗传多样性水平.单倍型网络关系图和系统发生分析均显示来自云南和两广地区的版纳鱼螈分歧明显,已形成了不同的进化谱系.种群遗传结构分析也显示来自云南的勐腊种群与两广各种群之间显著的遗传差异,这提示分布在云南与两广地区的版纳鱼螈应作为不同的管理单元(MU)进行保护.综合两种中性检验(Fu's Fs=9.44,P=0;Tajima's D=1.88,P=0.013)和种群增长指数(g=5415.03±297.55)分析的结果表明,两广地区的版纳鱼螈可能经历近期的种群扩张事件.     

版纳鱼螈外周血细胞观察

以濒危两栖动物版纳鱼螈(Ichthyophis bannanica)为材料,应用瑞氏-姬姆萨混合染色法与血细胞计数法观察并统计了版纳鱼螈各种外周血细胞的形态特征和数量比例.结果表明,版纳鱼螈的外周血液中红细胞数量较多,呈卵圆形、椭圆形、梭形和梨形,平均含量为2.57 ×105个/mm3.白细胞数量较少,多呈近圆形,平均含量为0.72×103个/mm3.白细胞中,淋巴细胞最多,其次为单核细胞、嗜中性粒细胞、嗜碱性粒细胞和嗜酸性粒细胞.血栓细胞数量较少,常数个集合在一起.同时,将此研究结果与鱼类、爬行类和其他两栖类的血细胞比较,进而探讨了版纳鱼螈的进化地位.     

宽体沙鳅脑组织学研究

为探究鱼类脑结构及其与生态习性的相关性, 采用HE及Nissl染色法对健康性成熟宽体沙鳅脑组织结构进行观察。结果显示: 宽体沙鳅脑由端脑、间脑、中脑、小脑、延脑五部分组成。嗅叶为典型的“鲤型”嗅叶; 大脑视前核呈索状排列, 未见视前核大、小细胞群; 间脑乳头体及副错位核清晰可见, 血管囊及下叶发达; 中脑视盖由5层构成; 小脑发达, 由3层构成; 延脑分化出面叶和发达的迷叶。这表明, 宽体沙鳅视觉稍有退化, 嗅觉、听觉、触觉、味觉及运动中枢发达, 生活中主要依靠嗅觉、听觉、触觉、味觉觅食及逃避敌害。     

致《四川动物》编辑部的一封信

《四川动物》编辑部:感谢您在过去一年里的对我的关心和支持!2006年5月我在贵刊2006年25卷2期发表《版纳鱼螈研究进展》,同年在《动物学杂志》41卷4期发表《版纳鱼螈的骨骼系统》。自这两文发表以来,我收到了数位关心该研究方向的读者来信,共同反映一个问题:《版纳鱼螈研究进展》一文“2.7骨骼研究”一段中提到“国内尚无学者关注版纳鱼螈的骨骼研究,国外仅有MtthewW.Colbert和David Canatella 2004年采用CT扫描的方法展示了版纳鱼螈头骨的三维结构,并制作成了动画电影“,而在《版纳鱼螈的骨骼系统》之前言部分又说:”到目前为止国内外尚…     

泥鳅脑的形态构造观察

观察了泥鳅（Misgurnus Anguillicaudatus）脑的显微结构。结果表明,泥鳅的脑组织基本结构与多数鱼类相一致,其脑轮廓狭长,包括端脑、间脑、中脑、小脑及延脑五部分,视叶隆起,小脑瓣突入中脑室内,延脑有核团的分化。同时与其生存环境和捕食习性相适应,泥鳅脑具有一些原始的特征,包括：嗅叶及嗅束分化较明显,大脑呈长椭圆状,仍保留鲤科（Cyprinidae）鱼类脑的原始特征;中脑视叶壁偏薄,与视觉不甚发达相关;小脑不发达,与其喜静的生活习性相适应;延脑前部稍稍隆起,面叶发达与其须感知食物的习性相符。     

版纳鱼螈的骨骼系统

以我国特有的珍稀濒危两栖动物版纳鱼螈(Ichthyophis bannanica)为材料,采用传统的脊椎动物骨骼标本制作技术与透明骨骼标本制作技术相结合的方法,对其骨骼系统进行了形态学研究,并与其他无足目和两栖动物相比较,探讨版纳鱼螈的亲缘关系和进化地位。结果表明,版纳鱼螈成体具头骨41枚,椎骨108~115枚,肋骨101~108枚,无四肢骨。头骨、椎骨和肋骨均具有适应于穴居、掘穴和夜行性习性的特征。版纳鱼螈与双带鱼螈(I.glutinosus)的头骨极为相似,却具有比Dermophis mexicanus的头骨更原始的特征。     

版纳鱼螈侧线系统的结构

版纳鱼螈(Ichthyophis bannanica)是我国无足目的仅有代表,应用光镜和扫描电镜对版纳鱼螈的侧线系统进行形态学和组织学观察的研究表明:版纳鱼螈幼体表皮中的侧线器官有接受机械刺激的神经丘和电接受壶腹器官两种,神经丘包括表面神经丘和陷神经丘。侧线分布主要包括:头部的鼻侧线、眶上线、眶下线、眶后线、口侧线、下颌线、咽侧线、鳃孔上线和身体上的背侧线。侧线器官的分布密度、大小和凹陷深度明显与周围表皮的厚度和不同部位有关。幼体的侧线器官退化与鳃孔的退化同步,亚成体以后不保留侧线系统。版纳鱼螈的侧线分布和器官结构与其它无足类的大致相似,仅在眶上线和眶下线的器官分布上存在微小的差别     

鲫鱼的脑

初中动物学下册(人民教育出版社1952年9月出版)第11画第93图"鱼的脑"为苏联十年制中学动物学中的插图直接引用过来的.苏联课本中所讲述的恐为鲈鱼(学名为Perca fluviatilis)的脑,而不是我们书中所讲述的鲫鱼(学名为Carassius auratus)的脑.因此在教授时,时常发生困难.鲫鱼的脑(见图1图2)可分为嗅叶,嗅柄,大脑,间脑,中脑     

Functional regeneration of the olfactory bulb requires reconnection to the olfactory nerve in Xenopus larvae

Larvae of the South African clawed frog (Xenopus laevis) can regenerate the telencephalon, which consists of the olfactory bulb and the cerebrum, after it has been partially removed. Some authors have argued that the telencephalon, once removed, must be reconnected to the olfactory nerve in order to regenerate. However, considerable regeneration has been observed before reconnection. Therefore, we have conducted several experiments to learn whether or not reconnection is a prerequisite for regeneration. We found that the olfactory bulb did not regenerate without reconnection, while the cerebrum regenerated by itself. On the other hand, when the brain was reconnected by the olfactory nerve, both the cerebrum and the olfactory bulb regenerated. Morphological and histological investigation showed that the regenerated telencephalon was identical to the intact one in morphology, types and distributions of cells, and connections between neurons. Froglets with a regenerated telencephalon also recovered olfaction, the primary function of the frog telencephalon. These results suggest that the Xenopus larva requires reconnection of the regenerating brain to the olfactory nerve in order to regenerate the olfactory bulb, and thus the regenerated brain functions, in order to process olfactory information.     

The Vascularization of the Anuran Brain: Olfactory Bulb and Telencephalon: A scanning electron microscopical study of vascular corrosion casts

Lametschwandtner, A., Albrecht, U., Adam, H. 1980. The vascularization of the anuran brain. Olfactory bulb and telencephalon. A scanning electron microscopical study of vascular corrosion casts. (Department of Zoology, University of Salzburg, Austria.) — Acta zool. (Stockh.) 61(4): 225–238. The vascularization of the olfactory bulb and the telencephalon of the anuran brain is studied by means of scanning electron microscopy of vascular corrosion casts.—The olfactory bulb is supplied via a terminal branch of the ramus hemisphaerii medialis ventralis, while the drainage is via the lateral telencephalic vein. The vascular plexus which caps the olfactory bulb shows “basket-like” vascular formations facing the rostral olfactory bulb. This plexus is supplied via two sources which are a) terminal branches of the ramus hemisphaerii medialis ventralis and b) a branch of the inner carotid artery. — In the telencephalon the vascular pattern of medial and lateral cortex, the striatum, the septum, and the amygdala are described. It is demonstrated that in the cerebral cortex of the anuran brain the centrifugal blood flow is not present in that strictness found in the other parts of the brain. The arterial supply is via the ramus hemisphaerii medialis ventralis and the posterior telencephalic artery (ramus hemisphaerii medialis dorsalis) and their branches as well as by branches of the preoptic artery. The venous drainage of the telencephalon is by the lateral telencephalic vein.     

Organizing activity of Fgf8 on the anterior telencephalon

The anterior part of the embryonic telencephalon gives rise to several brain regions that are important for animal behavior, including the frontal cortex (FC) and the olfactory bulb. The FC plays an important role in decision‐making behaviors, such as social and cognitive behavior, and the olfactory bulb is involved in olfaction. Here, we show the organizing activity of fibroblast growth factor 8 (Fgf8) in the regionalization of the anterior telencephalon, specifically the FC and the olfactory bulb. Misexpression of Fgf8 in the most anterior part of the mouse telencephalon at embryonic day 11.5 (E11.5) by ex utero electroporation resulted in a lateral shift of dorsal FC subdivision markers and a lateral expansion of the dorsomedial part of the FC, the future anterior cingulate and prelimbic cortex. Fgf8‐transfected brains had lacked ventral FC, including the future orbital cortex, which was replaced by the expanded olfactory bulb. The olfactory region occupied a larger area of the FC when transfection efficiency of Fgf8 was higher. These results suggest that Fgf8 regulates the proportions of the FC and olfactory bulb in the anterior telencephalon and has a medializing effect on the formation of FC subdivisions.     

Misrouting of mitral cell progenitors in the Pax6/small eye rat telencephalon

The olfactory bulb is a protruding structure formed at the rostral end of the telencephalon. Pax6-mutant mice and rats lack the olfactory bulb and, instead, develop an olfactory bulb-like structure at the lateral part of the telencephalon. Here, we report that ectopic formation of the olfactory bulb-like structure in these mutants is caused by the abnormal migration of mitral cell progenitors, which first differentiate within the olfactory bulb. Cell-tracing experiments in whole embryos in culture indicate that, in the mutants, the mitral cell progenitors that originate from the rostral part of the telencephalon migrate caudally toward the lateral part of the telencephalon. Cell transplantation demonstrates that the abnormal cell migration is not autonomous to the mitral cell progenitors themselves. The mislocation of the olfactory bulb in the mutant is not caused by loss of olfactory nerve innervation. Furthermore, transfection of a Pax6-expression vector to the mutant telencephalon restores the normal migration of mitral cell progenitors. These results provide evidence that Pax6 is required to position the mitral cell progenitors at the rostral end of the telencephalon.     

Olfactory bulb axonal outgrowth is inhibited by draxin

Olfactory bulb (OB) projection neurons receive sensory input from olfactory receptor neurons and precisely relay it through their axons to the olfactory cortex. Thus, olfactory bulb axonal tracts play an important role in relaying information to the higher order of olfactory structures in the brain. Several classes of axon guidance molecules influence the pathfinding of the olfactory bulb axons. Draxin, a recently identified novel class of repulsive axon guidance protein, is essential for the formation of forebrain commissures and can mediate repulsion of diverse classes of neurons from chickens and mice. In this study, we have investigated the draxin expression pattern in the mouse telencephalon and its guidance functions for OB axonal projection to the telencephalon. We have found that draxin is expressed in the neocortex and septum at E13 and E17.5 when OB projection neurons form the lateral olfactory tract (LOT) rostrocaudally along the ventrolateral side of the telencephalon. Draxin inhibits axonal outgrowth from olfactory bulb explants in vitro and draxin-binding activity in the LOT axons in vivo is detected. The LOT develops normally in draxin−/− mice despite subtle defasciculation in the tract of these mutants. These results suggest that draxin functions as an inhibitory guidance cue for OB axons and indicate its contribution to the formation of the LOT.     

Central connections of the olfactory bulb in the goldfish,Carassius auratus

Summary The central connections of the goldfish olfactory bulb were studied with the use of horseradish peroxidase methods. The olfactory bulb projects bilaterally to ventral and dorsolateral areas of the telencephalon; further targets include the nucleus praeopticus periventricularis and a caudal olfactory nucleus near the nucleus posterior tuberis in the diencephalon, bilaterally. The contralateral bulb and the anterior commissure also receive an input from the olfactory bulb. Contralateral projections cross in rostral and caudal portions of the anterior commissure and in the habenular commissure. Retrogradely labeled neurons are found in the contralateral bulb and in three nuclei in the telencephalon bilaterally; the neurons projecting to the olfactory bulb are far more numerous on the ipsilateral side than in the contralateral hemisphere. Afferents to the olfactory bulb are found to run almost entirely through the lateral part of the medial olfactory tract, while the bulb efferents are mediated by the medial part of the medial olfactory tract and the lateral olfactory tract. Selective tracing of olfactory sub-tracts reveals different pathways and targets of the three major tract components. Reciprocal connections between olfactory bulb and posterior terminal field suggest a laminated structure in the dorsolateral telencephalon.     

FGF signaling through FGFR1 is required for olfactory bulb morphogenesis

During development, the embryonic telencephalon is patterned into different areas that give rise to distinct adult brain structures. Several secreted signaling molecules are expressed at putative signaling centers in the early telencephalon. In particular, Fgf8 is expressed at the anterior end of the telencephalon and is hypothesized to pattern it along the anteroposterior (AP) axis. Using a CRE/loxP genetic approach to disrupt genes in the telencephalon, we address the role of FGF signaling directly in vivo by abolishing expression of the FGF receptor Fgfr1. In the Fgfr1-deficient telencephalon, AP patterning is largely normal. However, morphological defects are observed at the anterior end of the telencephalon. Most notably, the olfactory bulbs do not form normally. Examination of the proliferation state of anterior telencephalic cells supports a model for olfactory bulb formation in which an FGF-dependent decrease in proliferation is required for initial bulb evagination. Together the results demonstrate an essential role for Fgfr1 in patterning and morphogenesis of the telencephalon.     

Central connections of the olfactory bulb in the bichir,Polypterus palmas,reexamined

Summary Central connections of the olfactory bulb of Polypterus palmas were studied with the use of horseradish peroxidase and cobalt-tracing techniques. The olfactory bulb projects to subpallial and palliai areas in the ipsilateral telencephalon; a projection to the contralateral subpallium is noted via the habenular commissure. A further target of secondary olfactory fibers is a caudal olfactory projection area in the ipsilateral hypothalamus. No labeling was seen in the anterior commissure and in the contralateral olfactory bulb. The medial and the lateral pallium receive secondary olfactory fibers in distinct areas. Neurons projecting to the bulb are found in the ipsilateral subpallium, mainly in one dorsal longitudinal nucleus. The main connection with the tel- and diencephalon is mediated via the medial olfactory tract. This tract also contains fibers to the contralateral telencephalon, and to the hypothalamus. The smaller lateral olfactory tract mediates fibers to the lateral pallium. The organization of pathways of secondary olfactory fibers in the telencephalon is described. The present findings are compared to those obtained in species possessing an inverted forebrain.This investigation was supported by grants from the Deutsche Forschungsgemeinschaft to DLM     

Cellular interactions in the development of the olfactory system: an ablation and homotypic transplantation analysis

In the current study, we addressed two questions: First, is the olfactory placode necessary for the development of the olfactory bulb and the entire telencephalon? Second, does the olfactory placode contribute cells to the olfactory bulb? We addressed these questions by unilaterally ablating the olfactory placode in chick embryos before an olfactory nerve was produced and, in a second series of experiments, by replacing the ablated chick olfactory placode with a quail olfactory placode. Our results indicate that the olfactory placode is critical for olfactory bulb development, but is not necessary for the development of the rest of the telencephalon. Further, our results support the hypothesis that LHRH neurons and olfactory nerve glia originate in the olfactory placode, but do not support an olfactory placodal origin for other cell types within the olfactory bulb.