神经肽Y微量注入外侧隔核的心血管效应

本文观察了麻醉大鼠外侧隔核(LS)内微量注射神经肽Y(NPY)引起的心血管效应。LS内微量注射NPY可使血压和心率明显增加,其加压反应呈量效关系,但心率加快反应则否。LS内微量注射生理盐水对血压和心率无明显影响。     

损毁中缝大核对大鼠胃酸排出量及血清胃泌素水平的影响

本实验观察了损毁中缝大核对大鼠胃酸排出量和血清胃泌素水平的影响。实验表明:损毁中缝大核可增加胃酸排出量和血清胃泌素水平。切断双侧膈下迷走神经干可以消除这种作用,去除腹腔交感神经节及肠系膜上交感神经节只能部分减弱这种作用。     

Orofacial pain increases mRNA level for galanin in the trigeminal nucleus caudalis of the rat

The changes of preprogalanin mRNA levels in the superficial dorsal horn neurons (laminae I and II) of the trigeminal nucleus caudalis in response to orofacial pain induced by the injection of 5% formalin into the lips of rats was investigated and compared to those of preproenkephalin A mRNA and preprodynorphin mRNA in the same region by means of in situ hybridization histochemistry. Rapid and marked increases of preprogalanin and preprodynorphin mRNA were observed on the side of the injection, but the increase of preproenkephalin A mRNA level was less pronounced than that of the other two mRNAs, indicating that these peptides have different roles in the dorsal horn analgesic mechanism and that galanin, in addition to opioid peptides, may have a highly specific role in this mechanism.     

Morphology and function of capillary networks in subregions of the rat tuber cinereum

Summary The differentiated cytology, cytochemistry, and functions within subdivisions of the tuber cinereum prompted this morphometric and physiological investigation of capillaries in the median eminence and arcuate nucleus of albino rats. Morphometric studies established that the external zone of the median eminence had 3–5 times the number and surface area of true and sinusoidal capillaries than the internal or subependymal median eminence zones, or either of two subdivisions examined in the arcuate nucleus. Type-I true capillaries, around which Virchow-Robin spaces comprise 1% of arcuate tissue area, were situated proximally to the median eminence border. This finding is consistent with a premise that confluent pericapillary spaces enable infiltration of arcuate neurons by factors from capillary blood from the median eminence or Virchow-Robin spaces. Physiologically, the rate of penetration across the median eminence capillaries by blood-borne [¹⁴C]-aminoisobutyric acid (a neutral amino acid used as a capillary permeability tracer) was 142 times greater than for capillaries in the distal arcuate nucleus within 12 s of tracer administration. A new finding was that the proximal arcuate nucleus had a permeability x surface area product of 69 l g^–1 min^–1, 34 times greater than that in more distal aspects of the tuber where blood-brain barrier properties exist. We also found that the microcirculatory transit time of a plasma space marker, [¹⁴C]sucrose, was considerably longer (1.2 s) in the median eminence and proximal arcuate nucleus than in the distal arcuate or ventromedial nucleus (0.4 s). By virtue of its high capillary permeability and extensive blood-tissue surface area, including the wide Virchow-Robin spaces, the median eminence external zone could be a gateway for flooding other tuberal compartments with blood-borne factors. This effect may be compounded by capillary bed specializations in the proximal arcuate nucleus where Type-I true capillaries, Type-III sinusoids, and pericapillary spaces are confluent with those in the median eminence. The results indicate that the proximal arcuate parenchyma could be exposed to circulating neuroactive substances on a moment-to-moment basis.Dedicated to Dr. Milton W. Brightman of Bethesda, Maryland, USA on the occasion of his 67th birthday and tribute as Craigie scholar at the First Craigie Conference on Brain Capillaries, Toronto, Ontario, June 24, 1990     

The life cycle of mitochondria in the true slime mould,Physarum polycephalum

The cytoplasmic aspects of mitochondrial biogenesis have been the focus of much recent attention and a review is presented here of studies on the life cycle of mitochom dria inPhysarum polycephalum. Such studies have focused predominantly on behavior of the mitochondrial genome throughout the mitochondrial life cycle and have been designed to reveal details about (1) the role of the DNA-membrane complex in the segregation of the mitoehondrial genome; (2) the regulation of mitochondrial activity associated with changes in ptoidy of the mitoehondrial nucleus; (3) the hierarchical pattern of transmission of the mitochondrial genome as it relates to the mating-type locus (matA) during the sexual development; and (4) the fusion of mitoehondria that is promoted by a mitochondrial plasmid. The results of such studies contribute significantly to efforts towards a better understanding not only of the mitochondrial life cycle inP. potycephalum but also of the biogenesis of mitoehondria and plastids in many other organisms. Recipient of the Botanical Society Award for Young Scientists, 1988.     

Granulolysis in neurosecretory neurons of the rat supraoptico-posthypophyseal system

Ultrastructural and cytochemical observations on neurosecretory neurons of the rat supraoptico-posthypophyseal systems were made under experimental conditions which resulted in striking changes in the amount of neurosecretory granules and lysosomes. Attention was focused on granulolysis. At the onset of rehydration following a 4 days water deprivation, very active autophagy took place in neurosecretory axons of the neural lobe involving the marked increase in smooth endoplasmic reticulum, microvesicles and neurosecretory granules, although the latter were still very few due to previous depletion. When axonal transport was inhibited by colchicine at the onset of rehydration, granules accumulated in the perikarya while granule reloading of the neural lobe was delayed. However autophagy, although always active in axons, remained scarce in perikarya. Moreover, in the latter there was only slight evidence of crinophagy. Hypophysectomy also induced granule accumulation in the perikarya, although accompanied by little granulolysis. Images indicative of crinophagy as shown by acid phosphatase localization were few and exclusively restricted to perikarya, while autophagy occurred essentially in axons. Autophagy appeared to be the predominant process for granulolysis and might be considered here as an aspect of the general turnover of cell constituents, related to the sudden regression of hyperactivity-induced hyperthrophy, rather than as an expression of a specific regulation of an excess of secretory material.     

Demonstration of the tuberoinfundibular tract of the cat

Summary The distribution of dopaminergic nerve cells in the cat hypothalamus, particularly in the arcuate and periventricular nuclei, and the projections of their axons were studied by fluorescence and electron microscopy after electrothermic coagulation. The majority of these perikarya were located in the arcuate nucleus and the periventricular nucleus dorsocaudal to the optic chiasma. Large lesions caused a wide and diffuse depletion of dopamine fluorescence within the external layer; small lesions caused ipsilateral partial depletion of the dopamine fluorescence. Electron microscopic observations in animals with a lesioned arcuate nucleus revealed that in the external layer degenerating nerve terminals are engulfed by glial processes. In some cases nerve fibers had entirely disappeared and a heavy reactive proliferation of glial processes was observed. Persistence of the form of the median eminence in spite of the extensive degeneration of its nervous elements is considered to depend upon this glial proliferation.Dedicated to Professor W. Bargmann in honour of his 70th birthday     

Retinohypothalamic pathway in the duck (Anas platyrhynchos)

Summary Retinohypothalamic connections were studied in the duck after unilateral optic nerve transection using both light and electron microscopic techniques. Degenerated endings of optic fibers were found only in a circumscribed part of the anterior hypothalamic area, i.e. the ventral region of the contralateral suprachiasmatic nucleus. Images of degenerating boutons were observed in frozen sections (method according to Johnstone-Bowsher), and their presence confirmed by electron microscopic examination. These degenerating boutons make synaptic contacts with dendrites or dendritic spines of neurons of the suprachiasmatic nucleus.In the same material, the decussation of the optic chiasma was studied with the light microscope. Uncrossed retinal fibers were found in the marginal optic tract, the basal optic root and occasionally also in the isthmo-optic tract.Dedicated to Professor Dr. W. Bargmann on the occasion of his 70th birthdaySupported by the DGRST and European Training Program Brain and Behaviour ResearchI wish to express my gratitude to Professor Andreas Oksche, who repeatedly offered me the scientific facilities at the Department of Anatomy of the University of Giessen, and who provided me with valuable neuroanatomical suggestions throughout the progress of these studies.     

The synaptic organization in the medial geniculate body of afferent fibres ascending from the inferior colliculus

Summary The ventral nucleus of the medial geniculate body has been examined electron microscopically 2–5 days after destruction of the inferior colliculus. In both the ipsi- and contralateral ventral nuclei, degenerating collicular afferents are of medium diameter (1–5 ) and their degenerating terminals are distributed mainly to synaptic aggregations (glomeruli) in which they end axo-axonically and axo-dendritically. Their distribution and mode of termination indicates that these terminals belong to a class which in normal material is large, contains round synaptic vesicles and ends by means of asymmetrical synaptic complexes upon dendrites and upon the second (pale) type of glomerular terminal. It also ends by means of adhesion plaques on the same dendrites.As the terminals of corticothalamic afferents to the nucleus are already known, only the origin of two types remains to be determined: the pale terminals, which arise from structures resembling dendrites and which end only axo-dendritically, and a small, less common terminal which ends axo-axonically, axo-dendritically and axo-somatically. Both types contain flattened synaptic vesicles and end by means of symmetrical synaptic complexes.Correlative Nauta and Golgi studies suggest that the collicular afferents have a very specific spatial distribution within the cellular laminae composing the ventral nucleus.The terminal degeneration commences as a neurofilamentous hyperplasia and quickly passes to one of increased electron density. There is evidence for early removal of degenerating terminals from the postsynaptic membrane.This work was supported by a grant from the Bank of New Zealand Medical Research Fund.We are indebted to Professor J. A. R. Miles for use of the electron microscope.     

Ultrastructure of Sarcocystis booliati Dissanaike and Poopalachelvam, 1975 from the moonrat, Echinosorex gymnurus, in Malaysia

The ultrastructure of the cyst wall and zoites of Sarcocystis booliati from the moonrat Echinosorex gymnurus, was studied with the electron microscope. The primary cyst wall was thin, smooth and filled with a finely-granular, electron-dense material. The surface of the cyst wall had a row of vesicular invaginations. The ground substance beneath the primary cyst wall did not extend into the cyst to form septae. The zoites were covered with a double-layered membrane or pellicle and had an anterior conoid, 2 conoidal rings, 22 subpellicular microtubules, about 8 rhoptries, 50–60 micronemes, scattered lipid droplets, a micropore and a posteriorly situated nucleus, in front of which was a sac-like mitochondrion with vesicular internal cristae. The distinctive features in the ultrastructure of S. booliati were the thinness of the cyst wall, the absence of cytophaneres or trabeculae and the comparatively small number of micronemes in the zoites.