摘要:

AbstractIntracranial arterial patterns were studied in injectedAlligatoradults and in serially sectionedAlligatorembryos ranging in body length from 4.0 mm to 180 mm. The embryos show extensive developmental modifications involving in particular the posterior cerebral artery anterior cerebral artery, ophthalmic artery, and mesencephalic artery. The posterior cerebral arteries of both sides fuse to form the common ethmoidal artery, which forms a connection with the anterior cerebral artery. A portion of the latter then degenerates posterior to the common ethmoidal artery; the posterior cerebral arteries thus become the sole intracranial source of supply for the naso‐olfactory regions. The ophthalmic artery functions only during early embryonic stages and is later replaced by the orbital artery. The formation of flexures in the brain influences the development of the embryonic mesencephalic artery and causes the posterior ramus of this vessel to become the stem of the definitive mesencephalic arter

ISSN:0092-7317    

DOI:10.1002/cne.901350402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1969

数据来源: WILEY

摘要:

AbstractThe spinal ganglia of the fowl have been studied from the third incubation day to the adult.The neuroblasts are the first cells that differentiate in the ganglionic anlage. Satellite cells, probably arising from the undifferentiated elements scattered among the neuroblasts, become detectable during the fifth incubation day. They appear starshaped with attenuated cytoplasmic expansions intervening between adjacent neuroblasts. At this time the neuroblasts largely outnumber the satellite cells.From the sixth incubation day connective tissue spaces, appearing as large intercellular gaps containing an amorphous material, become evident between satellite cells. During the second half of the incubation period each nerve cell is completely enveloped by a satellite cell sheath, which is in turn entirely surrounded by a connective tissue space. The satellite cells change in shape from star‐shaped to flat elements. By this time and even more so in adult life, satellite cells outnumber nerve cells.The satellite cells increase progressively in number, up to the ninth incubation day mainly through differentiation of undifferentiated cells; but later on by mitotic reproduction of fully differentiated satellite cells.The neuron‐satellite cell boundary becomes more and more complicated with time, thus enlarging in parallel with the increase in volume of the nerve cell. Adhering junctions may be observed along this boundary.The significance of the ergastoplasm, centrioles and cilia of the satellite cells is briefly discussed. Numerous adhering and scarce occluding junctions, some of which are temporary, link satellite ce

ISSN:0092-7317    

DOI:10.1002/cne.901350403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1969

数据来源: WILEY

摘要:

AbstractA method is presented for individually mounting serial sections on one‐hole specimen holders. Also a technique for constructing stereograms based upon serial sections is described including a method for obtaining perspective foreshortening. Ultrastructural findings revealed the surface of the motoneuron to be covered with synaptic boutons which frequently pressed against each other. Surface area not contacted by boutons was covered with astroglial processes. The latter processes wedged around and sometimes between the boutons. On occasion finger‐like astrocytic processes (spines) were found to invaginate the terminal boutons. No synaptic thickenings were found between adjacent boutons (axo‐axonal contacts) on the perikaryal surface. However, in view of the enormous size of the motoneuron contrasted to the small volume of tissue thus far investigated, this observation is regarded as inconclusive. Three‐dimensional studies revealed an astrocytic process with disproportionately large amounts of surface membrane in the form of many interconnected pockets. The initial unmyelinated segment of a large anterior horn cell was encountered and found to have synaptic boutons on its proximal half. Its distal half was surrounded by an extracellular space containing electron dense material similar to that found in the goldfish by Robertson, Bodenheimer, and Stag

ISSN:0092-7317    

DOI:10.1002/cne.901350404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1969

数据来源: WILEY

摘要:

AbstractStudy of the brain stem, stato‐acoustic nerve, and inner ear of the mouse by a cholinesterase technique has disclosed that the acetylcholinesterase‐positive centrifugal fibers to the inner ear are part of a general visceral efferent system which supplies fibers to the facial, vestibular and cochlear nerves. This system largely corresponds in its central course to that of the bundle of fibers which has been called “olivocochlear”, but its cells of origin do not appear to lie in the superior olivary complex. Instead, the preganglionic cells of origin are chiefly organized into four nuclei: one medial to the genu of the facial nerve; one lateral to the genu; the superior salivatory nucleus; and a small nucleus lying within the borders of the lateral vestibular nucleus. The fibers to the inner ear synapse, perhaps completely, on postganglionic cells located along their peripheral courses. Additionally, orthosympathetic acetylcholinesterasepositive fibers are present in the cochlear nerve; they arriveviathe anterior inferior cerebellar artery. Postganglionic fibers supply not only vascular walls and secretory epithelium in the inner ear but also (1) contact the somata of some acetylcholinesterase‐positive, bipolar cochlear neurons and (2) ramify among, or terminate upon distal, acetylcholinesterase‐positive processes of some sensory neurons at the foramina nervosa. These finding indicate that, on morphological grounds, autonomic nerve activity may influence auditory input at th

ISSN:0092-7317    

DOI:10.1002/cne.901350405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1969

数据来源: WILEY

ISSN:0092-7317    

DOI:10.1002/cne.901350406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1969

数据来源: WILEY