摘要:

AbstractCell pairs from late cleavage and early blastulaAmbystoma mexicanumembryos were found to be electrotonically coupled. Thin‐section electron microscopy revealed typical gap junctions between the cells. Freeze‐fracture electron microscopy showed the gap junctions to be comprised of aggregations of 8.5‐nm P‐face particles and corresponding E‐face pits. The conductance of the amphibian embryonic gap junction is known to be voltage‐dependent, but no obvious gating structure was resolved by these morphological

ISSN:0002-9106    

DOI:10.1002/aja.1001580202

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

年代:1980

数据来源: WILEY

摘要:

AbstractAutoradiographic evidence for incorporation of3H‐glucose and35S‐sulfate into the cupulae ofXenopus laevis(African clawed toad) lateral line organs was obtained after injection into the dorsal lymph sacs of adult animals. Time intervals of 15 minutes to 4 hours after administration of these labeled metabolic precursors were used to examine the time course of the apparent mechanism of growth of the cupulae. Our results suggest that the two layers of accessory cells (the sustentacular cells and inner layer of mantle cells), concentrically arranged around the organ's central sensory (hair) cells, elaborate distinct cupular components. Sustentacular cells, immediately adjacent to the sensory cells, appear to produce and extrude at their exposed apices a cupular “core” substance labeled by3H‐glucose, but not by35S‐sulfate. The layer of inner mantle cells, external to the sustentacular cells, was labeled by both precursors and is spatially situated to secrete a cupular sheath enclosing the cupular core. Ultrastructural differences between the secretory products within the two cell types were marked. Electron microscopic autoradiography of toads killed 4 hours after3H‐glucose injection showed that silver grains were associated with accumulations of the respective secretory products in sustentacular and inner mantle cells, and label was found over the cupular trough area, where the bases of the cupulae are attached. These results suggest that the cupular core and sheath may both contain mucopolysaccharide, and the sheath, a sulfated mucop

ISSN:0002-9106    

DOI:10.1002/aja.1001580203

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

年代:1980

数据来源: WILEY

摘要:

AbstractDifferential growth of neural transplants as related to the age of the donor embryos was investigated in this study. Neocortical tissue of constant volume, obtained from embryos of 15, 16, 17, 18, 19, 20, and 21 days' gestational age, was transplanted into the cerebellum of 10‐day‐old rats. The fully grown transplants were analyzed quantitatively and qualitatively 90 days after transplantation. The ultimate volume of the transplants and the estimated total number of neurons in them followed a gradient in relation to the age of the donor embryos. At one extreme, the neural transplants from 15‐day‐old embryos grew very large, showing a 21‐fold increase in size, and at the other extreme, those from 21‐day‐old embryos grew less than two‐fold in volume. These differences were determined by the developmental history of the transplants. Neural tissue obtained from 15‐day‐old embryos contained predominantly neuroepithelial cells which continued to proliferate even after transplantation. This resulted in the large size of these transplants. At the other extreme, neural tissue from 21‐day‐old embryos contained predominantly preformed neuroblasts, and they simply differentiated after transplantation. Due to this, the transplants were small in size. Neural tissues obtained from other embryos of different gestational ages between these two extremes contained neuroepithelial cells and preformed neuroblasts in differential ratios. The number of neuroepithelial cells in the transplants and their differential proliferative activity after transplantation, and the number of neuroblasts present, determined the differential sizes of these transplants. In histological preparations, all transplants were seen to contain normal‐looking and well‐differentiated neurons, and normal‐looking neuropil. The transplants were integrated with the host brain, in that there was neither any gap nor any scar tissue between the transplants and the host neural tissue surrounding them. Neither the transplants nor the host brains showed any pathological

ISSN:0002-9106    

DOI:10.1002/aja.1001580204

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

年代:1980

数据来源: WILEY

摘要:

AbstractIn this study the growth of neural transplants was analyzed in relation to the age of the host animals and the site of transplantation. The influence of these two host parameters on the growth of neural transplants with high growth potential (tissue from 15‐day‐old embryos) and low growth potential (tissue from 18‐day‐old embryos) was investigated. Neocortical neural tissues of constant volume, obtained from 15‐ and 18‐day‐old embryos, were tranplanted into the forebrain or cerebellum of 5‐, 10‐, 20‐, 25‐, 30‐, 35‐ and 180‐day‐old host animals and analyzed, quantitatively as well as qualitatively, 90 days after transplantation. The transplants grew larger in volume in the cerebellum than in the forebrain region of the hosts of all ages. In both sites, tissue from 15‐day‐old embryos yielded larger transplants than tissue from 18‐day‐old embryos. Transplants from 15‐day‐old embryos grew most extensively in 5‐day‐old host animals (33‐fold in the cerebellum, and 23‐fold in the forebrain region.) In older host animals it grew less extensively, and without much variation in size that could be attributed to the age of host animals. Tissue from 18‐day‐old embryos grew little, regardless of site of transplantation or age of host. Apparently the age of the host animals and the site of transplantation had greater influence on the growth of the neural transplants with high growth potential than on those with low growth potential. Histologically, the neural transplants in all cases contained normal‐looking and fully differentiated neuro

ISSN:0002-9106    

DOI:10.1002/aja.1001580205

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

年代:1980

数据来源: WILEY

摘要:

AbstractCells of mineral oil‐induced plasmacytomas (MOPC) and normal plasma cells from mouse lymph nodes were used to study the intracellular localization of IgG by means of immunoferritin cytochemistry on ultrathin frozen sections. IgG was demonstrated in the rough endoplasmic reticulum, in virus‐containing smooth ER of the tumor cells, in peripheral elements at the cis‐side of the Golgi complex, and in all Golgi cisternae. It is suggested that the peripheral elements transfer IgG molecules from the RER to the Golgi complex. Vacuoles showing a strong immunoreaction occurred at the trans‐side of the Golgi complex. These vacuoles were normal in lymph node plasma cells and were occasionally seen in the tumor plasma cells. It is proposed that these vacuoles carry IgG from the Golgi complex to the cell membrane and, hence, can be considered as secretory v

ISSN:0002-9106    

DOI:10.1002/aja.1001580206

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

年代:1980

数据来源: WILEY

摘要:

AbstractForelimbs of the newtNotophthalmus (Triturus) viridescenswere amputated at the wrist, and at 14 to 25 days, the new limb regenerates were removed by a razor‐blade cut. After incubation of the isolated regenerates in a medium containing only inorganic salts, the epithelium was removed easily from the underlying mesenchyme. The surfaces separated in the salt solution were examined using scanning and transmission electron microscopy to evaluate the completeness of the separation and the extent of tissue damage near the plane of separation. Rarely was an epithelial cell found clinging to the mesenchymal surface, supporting previous light microscopic observations. The most apparent morphological damage was sustained by the basal epithelial cell surfaces, which exhibited blebbing; the formation of vacant vesicles within the cytoplasm near the newly exposed plasma membranes; the structural disruption of some organelles; and the tearing away of fragments of the basal epithelial cell plasma membranes, which remained adherent to the mesenchymal surface during separation procedure. Examination of the structure of the epithelialmesenchymal interface of intact regenerates showed that the plane of epithelialmesenchymal separation was, for the most part, between the basal epithelial cell membrane and its substrate, an extracellular material which remained at the mesenchymal surface after separation. This substrate was in the form of an extracellular material closely adherent to the basal epithelial cell membrane at the distal tips of the regenerates; a developing basal lamina at the periphery of regenerates undergoing blastema accumulation; or a mature basal lamina at the base of digit stage regenerates. The usefulness of these separated tissues for future experimentation and the evaluation of the nature of the epithelial substratum throughout the course of limb regeneration are discusse

ISSN:0002-9106    

DOI:10.1002/aja.1001580207

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe present study defines the cellular composition of chemosensory corpuscles (taste buds) present in the mucosa overlying the arytenoid cartilages of the larynx in serial sections studied by electron microscopy. Three cell types can be defined in such chemosensory corpuscles. Basal cells are relatively undifferentiated in terms of cytologic characteristics and have been identified presumptively as the stem cells for differentiation of the other two cell types. Sustentacular or supporting cells are characterized by the presence of apical electron‐opaque granules that apparently are extruded into the lumen of the pore, and are, thus, the source of the electron‐opaque extracellular material present between the microvilli protruding from the apex of the cells into the chemosensory corpuscle pore. The chemosensory cells are characterized by the presence of synaptic specializations with appended nerve fibers at the base of the cell, the presence of specific cytoplasmic secretory granules, as well as numerous clusters of typical synaptic vesicles, and apical microvilli that extend into the pore of the corpuscle. Other cell profiles encountered in chemosensory corpuscles are cells in various stages of degeneration or transition, to one of the other cell types, from undifferentiated basal cells. Two types of synaptic specializations have been identified as being associated with chemosensory cells. The first is characterized by an increased electron‐opacity of the respective plasma membranes of nerve fiber and chemosensory cell. In this situation numerous synaptic vesicles usually are present in the cytoplasm of the chemosensory cell subjacent to the membrane densities. A second type of synaptic association is characterized by the presence of subsurface cisterns of agranular endoplasmic reticulum in the cytoplasm of the chemosensory cell, and numerous synaptic vesicles often are present in the axoplasm of the subjacent neurite, suggesting a reciprocal synapse. These findings are interpreted to indicate that only one cell type is specialized for transducing chemical signals into neural activity and that this cell is modulated by activity of the nervous s

ISSN:0002-9106    

DOI:10.1002/aja.1001580208

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

年代:1980

数据来源: WILEY

摘要:

AbstractPrevious studies have shown that villus size in the small intestine decreases from the duodenum toward the ileum. Villus‐enlarging and villus‐reducing factors have been found in the gastric, pancreatic, and duodenal secretions, and in bile (Altmann and Leblond, ′70; Altmann, ′74). We here explore the role of intrinsic factors present in the individual sections of the small intestine by following the development of villus height in fetal (21‐day old) jejunal and ileal segments implanted under the kidney capsule of syngeneic adult rats. Twenty‐eight and 45 days after implantation, the jejunal villi contained significantly more columnar epithelial cells than did the ileal villi, but the jejunoileal gradient was even greater in small intestine of corresponding ages, developing in situ. Our experiments, thus, show that the jejunoileal gradient is already programmed in rats 1 day before birth, while other factors contribute postnatally to regulation of it

ISSN:0002-9106    

DOI:10.1002/aja.1001580209

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

年代:1980

数据来源: WILEY

摘要:

AbstractIn previous studies, a marked diminution in left coronary flow during systole has been demonstrated. This phenomenon has been said to result from capillary compression by the contraction of myocardium and perhaps also from active changes in the state of the smooth muscle in the wall of the coronary vessels. In order to determine the morphological factors involved in this occurrence, and to gain a three‐dimensional concept of the myocardial microvasculature, casts were prepared by perfusion of the coronary arteries with methyl methacrylate. Because of the conditions of the perfusion, these casts were considered to demonstrate a state of muscular contraction. Following maceration, portions of the casts were prepared for scanning electron microscopy (SEM).Arterioles of larger diameter were characterized by the helical configuration of the vascular replicas. Smaller vessels were categorized according to their directional pattern and their diameter. The arterioles gave rise to numerous large‐diameter capillaries and also to short vessels that were guarded by sphincters. True capillaries, in some cases guarded by precapillary sphincters, were packed in densely stacked parallel sheets with numerous short anastomotic connections between them. Postcapillary venules were found to enter at regular intervals into larger venules arranged perpendicular to the capillary sheets.Most of these characteristics were found to be consistent throughout the microvasculature. These structural features were considered to be factors in the active regulation of blood flow through the myocardial microvasculat

ISSN:0002-9106    

DOI:10.1002/aja.1001580210

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

年代:1980

数据来源: WILEY

摘要:

AbstractThe male urethral sphincter is a striated muscle in contact with the urethra from the base of the bladder to the perineal membrane. The individual muscle fibers are 25 to 30% smaller than fibers of associated muscles and are embedded in connective tissue which obscures the visibility of the whole muscle.The muscle primordium is laid down around the urethra prior to the development of the prostate. Subsequently, the prostate develops as a diverticulum of the urethra and grows into the developing sphincter, thinning the overlying musculature. With the onset of puberty, accelerated growth of the prostate displaces the sphincter, with atrophy of the overlying muscle, resulting in what may appear to be isolated segments of the sphincter muscle distributed around the prostate. The prostate overgrows the anterior portion of the urethra and the associated sphincter muscle.There is no distinct superior fascia of the so‐called urogenital diaphragm separating the sphincter muscle from the prostate. The fascia of the sphincter muscle is inseparable from the prostatic sheath, is oriented vertically, and passes through the urogenital hiatus to unite with the fascia of the pudendal canals at the isochiopubic rami. Thus, the sphincter muscle is a component of a bladder‐urethra‐prostate‐sphincter unit which lies within the pelvis, in the urogenital hiatus, and rests upon the perineal membrane. The concept of a urogenital diaphragm is not borne out by thi

ISSN:0002-9106    

DOI:10.1002/aja.1001580211

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

年代:1980

数据来源: WILEY