摘要:

AbstractThe non‐primary input to the soma of the principal cells of the rostral anteroventral cochlear nucleus (AVCN) of the guinea pig was defined by correlating data from freeze‐fractured and thin‐sectioned specimens. The principal cells receive three types of non‐primary terminals in addition to a single end bulb from the ascending branch of the auditory nerve. The first, the O‐boutons are irregularly shaped, medium‐sized boutons, containing oval synaptic vesicles. These cover about 13% of the soma and each makes from one to three crescent‐shaped axosomatic junctions. Paramembranous dense material is distributed symmetrically between the pre‐ and postsynaptic junctional membranes. The second, the F‐bouton, is a small, ovate bouton which occurs either singly or in small clusters and covers about 5% of the soma. This bouton, containing flattened synaptic vesicles, has a single, oval synaptic junction lined by thin, paramembranous densities distributed symmetrically between the pre‐and postsynaptic membranes. The third, the SR‐bouton, is a medium‐sized bouton containing small, round synaptic vesicles. These boutons cover about 4% of the soma, but more frequently contact dendrites in the neuropil. The junctional region of the bouton is poorly defined. Small tufts of dense material symmetrically line the cytoplasmic surfaces of the pre‐ and postsynaptic membranes along scattered, narrow undulations of the apposition. In freeze‐fracture replicas, several narrow troughs on the cytoplasmic leaflet frequently have a higher density of large intramembranous particles than adjacent membrane and may represent a diffusely organized active zone. No specializations are found on either leaflet of the postsynaptic plasmalemma opposite the non‐primary boutons. Correlation of the measurements from thin‐sectioned and freeze‐fractured material suggests that the oval, flattened, and small round vesiclecontaining boutons occur on the somata of the pr

ISSN:0002-9106    

DOI:10.1002/aja.1001530402

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe numbers of nerve fibers in 44 intact chorda tympani nerves (CT) from 34 rats were counted on electron micrographic montages of cross‐sections of the nerves. The mean number of fibers was 1,096, consisting of 641 myelinated and 455 unmyelinated fibers. There was no significant difference in the mean number of fibers between CT's from right and left sides, nor was there any significant difference in counts between CT segments taken from the middle ear and those taken from just proximal to the region where the CT joins the lingual nerve. The relative contribution of efferent and afferent fibers in the CT was assessed in 13 animals as follows. Intracranial surgery was performed to cut the root of the facial nerve just proximal to its entrance into the internal auditory meatus on the right side. After 19 to 21 days, to allow Wallerian degeneration of the efferent fibers, counts were made as above. The mean number of afferent fibers in the rat CT was 484 myelinated and 122 unmyelinated (606 total); the intact left CT's from the same animals contained a mean of 616 myelinated and 402 unmyelinated (1,018 total) fibers. The afferent limb of the CT, therefore, contains 79% of the total number of myelinated fibers and only 30% of the total number of unmyelinated fibers. Removal of the superior cervical sympathetic ganglion did not significantly affect the numbers of fibers. In order to determine whether the efferent limb of the CT contributes fibers to the fungiform papillae on the tongue, we compared the number of (CT) fibers in fungiform papillae from “de‐efferented” rat tongues with that from papillae of controls. In order to make this comparison, it was necessary to section the lingual nerve, which contributes about 75% of the total number of fibers to the fungiform papillae. This was done in both the control and de‐efferented animals. There was no significant difference in mean number of fibers in fungiform papillae innervated by a de‐efferented CT when compared with those innervated by an intact CT. There is, then, no evidence from these studies to suggest the presence of an efferent CT component within the fungif

ISSN:0002-9106    

DOI:10.1002/aja.1001530403

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe use of methyl methacrylate corrosion casts prepared from portions of the vascular system has made it possible to examine numerous and extensive areas of microscopic structures on a 3‐dimensional scale with the scanning electron microscope. By this means we have examined the arterial microvasculature of intracranial vessels among three domestic animal species. In addition, these vessels have been compared with the terminal branches of abdominal arteries in the dog. The results of this study suggest that the sphincteric control mechanisms of the vessels in the two regions may be structurally different from one another.In the case of the intracranial vessels, the terminal portion of the arteriole is continued by a precapillary arteriole composed of a chain‐like series of muscular constrictions. This is most suitably described as a precapillary sphincter area, which terminates at the capillary. In the abdominal vessels, the precapillary arteriole is generally followed by a single precapillary sphincter at the origin of the capillary. These morphological characteristics may account, in part, for the difference in response of vessels in these two regions in hypovolemic sh

ISSN:0002-9106    

DOI:10.1002/aja.1001530404

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

年代:1978

数据来源: WILEY

摘要:

AbstractQuantitative electron microscopic analysis of the supragranular zone of the dentate gyrus molecular layer has shown that the number and volume fraction of profiles of astroglial processes are significantly increased in senescent rats relative to young adults. These ultrastructural modifications, which are not associated with significant age‐related changes in the number of astrocytes or in the width of the molecular layer, may result from a formation of new astroglial processes and/or elongation of existing ones. In either case, the increase in the number and volume fraction of astroglial process profiles is an indicator of age‐related astroglial hypertrophy. Hypertrophy of astroglial processes, which seems to develop with advanced age as a response to partial deafferentation of neurons, may compensate for a decrease in the dendritic volume fraction, thereby preventing changes in the dimensions of the dentate gyrus molecular layer in senesce

ISSN:0002-9106    

DOI:10.1002/aja.1001530405

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

年代:1978

数据来源: WILEY

摘要:

AbstractCollared lemmings from Churchill, Manitoba, and their descendants were studied in captivity to define neuroendocrine and related histophysiological characteristics and responses, particularly in relation to photic and temperature conditions. Relatively great pineal size (0.1755 ± 0.0167 mm3, or 3.08 ± 0.30 = pineal volume in mm3× 103/body weight in gm; N = 16) shown in this arctic rodent is consistent with the suggestion that pineal size and significance may tend to be greater in more northern (higher latitude) species. Total number of nucleated cells per pineal averaged 137,000 ± 10,500. Pinealocytes (105,000 ± 8,700/pineal) and other cell types were present in relative numbers typical of mammalian pineal glands, and were not numerically correlated with age, sex, or location or circumstances of birth and early postnatal life. Chronic exposure to warmer (21–27°C) in comparison with colder (−9 to −6°C) environments, whatever the illumination, led to greater pinealocyte activity, as shown especially by nucleolar diameter, throughout most of the nine regions of the organ analyzed cytologically (all regions combined: P<0.001). Increased pinealocyte activity in chronic darkness was suggested by similar evidence (P<0.01), but in comparison with the thermal effects, was less marked and more variable in different regions of the organ. These and other findings of this study indicate that theDicrostonyxpinea organ is morphologically unique, relatively large in size, and cytologically responsive to environmenta

ISSN:0002-9106    

DOI:10.1002/aja.1001530406

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe paraganglia of adult man were studied using the formaldehyde‐induced fluorescence (FIF) method for histochemical characterization of biogenic monoamines. Microspectrofluorimetry was used to record the emission spectra and fluorescence intensities of the paraganglionic cells. The study of samples from six patients showed that well vascularized paraganglia were widely distributed throughout the retroperitoneal spaces. The paraganglia exhibited strong FIF with the spectral characteristics of monoamines. Treatment with HCl caused an increase in the fluoresoence intensity of the paraganglia and a simultaneous shift of the emission maximum from 480–495 nm. This change suggests the presence of high concentrations of tryptophyl‐containing peptides and is not due to monoamines. The possibility of a dual endocrine function for the paraganglia is disc

ISSN:0002-9106    

DOI:10.1002/aja.1001530407

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

年代:1978

数据来源: WILEY

摘要:

AbstractA culture system with defined medium has been utilized to elucidate the role of thyroxine (T4) and hydrocortisone (HC) in growth and differentiation of the epithelium of embryonic chick duodenum during the third week of development. Duodenal explants maintained a basically normal morphology for 48 to 72 hours, but during subsequent culture, muscle and mesenchyme deteriorated, previllous ridges shrank, the epithelial surface became pitted, and the tissue lost weight. These degenerative processes were retarded by addition of HC to the culture medium.Previllous ridges of cultured duodenum failed to develop into true villi and ridge growth was subnormal. Epithelial mitotic counts were increased by T4 or HC, as compared to cultured control tissue, but dropped below values in vivo, by 72 hours in culture.Epithelial differentiation proceeded more rapidly in duodenum cultured without hormones than in vivo. Increase in cell height, flattening of the epithelial surface, attainment of uniform staining of the brush border with periodic acidSchiff, increase in microvillar density, and formation of a terminal web were accelerated by 24 to 48 hours in culture. In the presence of T4, cell height and microvillar growth were stimulated further, reaching the state found at 19 to 21 days in vivo.

ISSN:0002-9106    

DOI:10.1002/aja.1001530408

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

年代:1978

数据来源: WILEY

摘要:

AbstractHuman embryonic and fetal optic discs were studied in semithin sections stained with silver and toned with gold, in a series ranging from 7 to 21 weeks of gestation. The observations suggest that Bergmeister's papilla forms by proliferation of glial cells in the optic disc rather than by sequestration of retinal glia by axons growing through the region. A possible stimulus for such a glial proliferation is hypothesized to be traction on the anterior face of the disc exerted through the primary vitreous. The formation of the glial sheath of the hyaloid artery also appears to be a consequence of traction from the primary vitreous.

ISSN:0002-9106    

DOI:10.1002/aja.1001530409

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe use of methyl methacrylate corrosion‐casts has made it possible to examine the intracranial microvasculature on a three‐dimensional scale with the scanning electron microscope. By this means we have compared regions of four cerebral and cerebellar arteries among three domestic animal species. The results of this study suggest that there are from one to three different levels of interarteriolar anastomosis between branches of the same or adjacent vessels. In the horse and ox anastomoses were demonstrated (1) at the level of the precapillary arterioles, (2) along the arterioles, and (3) between small pial arteries. In the dog only the first‐named anastomoses were evident in this study. These morphological characteristics may explain, in part, the shunting mechanism by which hypoxia may be reduced among intracranial capillary net

ISSN:0002-9106    

DOI:10.1002/aja.1001530410

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

年代:1978

数据来源: WILEY

摘要:

AbstractThe long‐term application of low levels of cathodal direct current to the growing deer antler produced abnormal branching patterns and antlers which grew in atypical directions. The experimental antlers were significantly reduced in length when compared to control antler

ISSN:0002-9106    

DOI:10.1002/aja.1001530411

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

年代:1978

数据来源: WILEY