摘要:

AbstractIn the continuously erupting rat incisor the ameloblasts progress through distinct stages associated with the secretion and maturation of enamel. We have examined the possibility that the so‐called “postsecretory” ameloblasts of the maturation stage of amelogenesis remain biosynthetically active and are engaged in the synthesis, secretion, and degradation of enamel gene products. The ultrastructural distribution of antigenic sites for enamel proteins was studied within enamel organ cells during the early maturation stage of amelogenesis in rat incisors by using the protein A‐gold immunocytochemical technique and rabbit polyclonal antibodies developed against mouse amelogenins. All regions of amelogenesis from late secretion through the first complete modulation from ruffle‐ended to smooth‐ended ameloblasts were examined. Specific immunolabelling was found within the rough endoplasmic reticulum, Golgi saccules, secretory granules, and lysosomes of ameloblasts throughout these regions. The heaviest intracellular immunolabelling was found within secretory granules and lysosomes (multivesicular type). Quantitative analyses showed that the Golgi saccules and the multivesicular lysosomes of modulating ameloblasts were generally less immunoreactive compared to similar organelles in ameloblasts secreting the inner enamel layer. Radioautographic studies confirmed that ameloblasts of the maturation stage incorporated3H‐leucine and3H‐methionine and secreted labelled proteins into the enamel layer. Grain counts indicated that ameloblasts from the first ruffle‐ended band incorporated about twofold less3H‐methionine and secreted about tenfold less labelled proteins into the enamel compared to ameloblasts secreting the inner enamel layer. The results of this study confirm that ameloblasts do not terminate biosynthesis and secretion of enamel proteins once the final layer has been deposited on the surface of the developing enamel. They continue to form and release new proteins during the maturation stage which intermix with older proteins laid down initially during the secretory stage of amelogenesis. Secretory activity for enamel proteins has been detected in ameloblasts up to at least the second ruffle‐ended phase of maturation, at which point the enamel matrix is part

ISSN:0003-276X    

DOI:10.1002/ar.1092170202

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe topographical arrangement of the clones of Asingle, Apaired, and Aaligned(As, Apr, and Aal) spermatogonia on the basement membrane of seminiferous tubules of the Chinese hamster was studied. It was found that at least some of these clones are not distributed at random as clones of similar cell number were often seen in clusters. Areas were found with few or many Asspermatogonia. Also, clusters of Aprspermatogonia were found, indicating that in such an area many Asspermatogonia more or less synchronously formed Aprspermatogonia. Since clusters of clones of 16 Aalspermatogonia were observed, it can be concluded that these clusters of Aprspermatogonia may proliferate in at least a roughly synchronous way.It was found that over large areas the densities of undifferentiated spermatogonia may be very low or high in comparison to the mean density in the animal. Whether the ratio of self‐renewal and differentiation of the stem cells changed locally in response to the high or low density of undifferentiated spermatogonia in particular areas was investigated. No indications for a regulatory mechanism to keep the density of stem cells and/or the density of undifferentiated spermatogonial clones at a certain level could be detected in the normal Chinese hamster. This lack of regulation was at least partly responsible for the widely different numbers of A1spermatogonia that were formed in the various areas studied in stage I

ISSN:0003-276X    

DOI:10.1002/ar.1092170203

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

年代:1987

数据来源: WILEY

摘要:

AbstractIn this study the yield of the proliferation of the differentiating spermatogonia into spermatocytes was determined in five Chinese hamsters. Large differences of up to a factor 2 were found between the numbers of A1spermatogonia in the various animals. However, the numbers of leptotene spermatocytes varied only by up to a factor 1.2 between animals. It is concluded that more spermatogonial degeneration takes place in animals with a relatively large number of A1spermatogonia than in those with a small number of these cells. In such a way in all animals ultimately about the same number of spermatocytes is formed.An experiment was done in which the number of A1spermatogonia was lowered with the S‐phase killer cytosine arabinoside (Ara‐C). It was found that this greatly increased the yield of the spermatogonial proliferation, showing a direct relationship between the number of A1spermatogonia in an animal and the extent of the spermatogonial degeneration.In addition to the variation in the number of A1spermatogonia found between various animals, an even larger variation of up to a factor 3.7 was found between the numbers of A1spermatogonia in different areas of seminiferous tubules within each animal. Nevertheless the variation in the number of leptotene spermatocytes in different areas within each animal was not larger than a factor 1.3. It is concluded that in the normal animal the phenomenon of spermatogonial degeneration depends on the local density of these spermatogonia. Apparently, when too many spermatogonia are present the surplus of cells degenera

ISSN:0003-276X    

DOI:10.1002/ar.1092170204

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe occurrence of alterations in testicular weight and morphology after vasectomy and vasectomy reversal by vasovasostomy was studied in Lewis rats. Animals were studied 3, 4, and 7 months after bilateral vasectomy or a vasectomy followed 3 months later by vasovasostomy. Other rats served as shamoperated controls. The weights of the testes in vasectomy and vasovasostomy animals fell into two groups—small testes weighing less than 0.88 g and normal‐sized testes of 1.2 g or more. When the extent of testicular alterations was estimated in sections for light microscopy by use of a semiquantitative testicular biopsy score count (TBSC), the morphology of the testes corresponded closely to the testis weight (r = .94), small testes having correspondingly low TBSC scores. In severely altered small testes, the seminiferous tubules were narrower than in sham‐operated rats, and numbers of germ cells were greatly depleted. Many tubules contained only Sertoli cells and spermatogonia, although spermatocytes were present in a minority of tubules. A few seminiferous tubules contained multinucleate spermatids. Electron microscopy of severely altered tubules revealed closely apposed processes of Sertoli cells, which contained filaments, microtubules, and endoplasmic reticulum. In contrast, testes with normal weight in vasectomy and vasovasostomy groups resembled those of the sham‐operated animals. Comparison of distributions of testicular biopsy score counts demonstrated differences between vasectomy and vasovasostomy groups as time after operation increased. At the 3–4‐month intervals, approximately one‐third of the testes were severely altered in both vasectomy and vasovasostomy groups. However, by 7 months the proportion of altered testes progressed to 60% in animals with a vasectomy, while it remained similar to the earlier intervals in rats that had received a vasovasostomy. These results suggest that vasovasostomy may prevent the progression of testicular alterations that occur after vasectomy, but vasovasostomy does not appear effective in reversing testi

ISSN:0003-276X    

DOI:10.1002/ar.1092170205

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

年代:1987

数据来源: WILEY

摘要:

AbstractDuring epididymal transit, the mouse sperm flagellum acquires a surface glycoprotein (SMA4) from epididymal fluid that functions as a sperm antiagglutinin. To determine the origin of this molecule, testes and epididymides of male mice were sectioned for light microscopy and stained with wheat germ agglutinin (WGA)‐peroxidase, a probe that has been used previously to examine the biology of SMA4. WGA reactivity was localized to the cytoplasm in a small population of cells in the distal caput epididymis. Testis cells and principle cells of the caput were nonreactive with WGA, while stereocilia were stained on principle cells in the corpus and cauda. The WGA‐positive cells in the distal caput were identified as holocrine cells on the basis of morphology, distribution, and PAS+ reaction. At high magnification, intense WGA reactivity was due to the presence of numerous apical granules in the cytoplasm. The location of the cells in distal caput coincided exactly with the region of tubule in which sperm first acquired SMA4 on their flagellae. These data suggest that holocrine cells near the junction of caput and corpus epididymis are the source of the sperm antiagglutinin S

ISSN:0003-276X    

DOI:10.1002/ar.1092170206

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe apex of the principal epithelial cells lining the vas deferens of the rat contains coated pits in continuity with the apical plasma membrane and large subsurface‐coated vesicles (100–125 um). In the apical cytoplasm, large, pale, uncoated vesicles (150–300 nm), small coated and uncoated vesicles (50–60 nm), uncoated vesicles about 75–90 nm, and membranous apical tubules are present, in addition to large, vacuolar, pale, multivesicular bodies, dense multivesicular bodies, and secondary lysosomes seen deeper in the cytoplasm amongst numerous ER cisternae, saccules of the Golgi apparatus, and mitochondria.The endocytic activity of these cells was investigated by using cationic ferritin (CF) as a marker of adsorptive endocytosis and native ferritin (NF) for demonstrating fluid‐phase endocytosis. These tracers were injected separately into the lumen of the vas deferens, and the animals were killed at various time intervals thereafter from 2 to 90 minutes. At 2 minutes CF was seen bound predominantly to microvilli and to areas of the apical plasma membrane delimiting coated pits as well as in large, coated vesicles. At 5 and 15 minutes the tracers were seen in apical tubules and pale multivesicular bodies; at 30 minutes moderately dense multivesicular bodies were labeled. At 1 hour and longer time intervals dense multivesicular bodies and secondary lysosomes were labeled. NF followed the same pathway as CF; however, no binding to microvilli or areas delimiting coated pits was observed. The numerous other vesicular structures, i.e., the large uncoated vesicles (150–300 nm) and the small coated and uncoated vesicles (50–60 nm), never became labeled with the tracers and therefore were not involved in the endocytic process. There was, however, and exception in the case of several small (75–90 nm) uncoated vesicles seen deeper in the apical cytoplasm of these cells which were labeled exclusively with CF. With time such vesicles appeared along the lateral and basal surfaces of these cells and discharged their content of CF into the lateral intercellular space or the connective tissue space at the base of these cells. Thus the principal epithelial cells in addition to sequestering the endocytosed tracers within secondary lysosomes where they are presumably degraded also appear to be involved in the transcytosis of material from the lumen of the vas deferens to the underlyi

ISSN:0003-276X    

DOI:10.1002/ar.1092170207

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

年代:1987

数据来源: WILEY

摘要:

AbstractWe used proteins in rat lung lavage fluid to successfully produce an antiserum against Clara cell secretory products. When used with the immunoperoxidase method, the antiserum specifically stained cells of the bronchiolar lining, which are morphologically consistent with Clara cells, as well as a few columnar cells in the bronchial and tracheal mucosa. B‐5‐fixed lung tissue furthermore demonstrated the immunoreactive layer over the bronchiolar epithelium. The alveolar and bronchial lining layers, on the other hand, were not immunoreactive, although a trace of granular immunoreactivity was seen in the latter. It was suggested that Clara cells produce and secrete some proteinaceous materials, which are mainly localized in the bronchiolar area after secretion and are seldom transferred into the alveolar lining layer. Our antibody cross‐reacted with the Clara cells of mice, but not with those of hamsters, guinea pigs, rabbits, dogs, cats, monkeys, and man. The high degree of specificity of this antisera to Clara cells in formalin‐fixed materials should make it a valuable tool for identifying Clara cell change in non‐neoplastic lung pathology and in obtaining some insights into cell origin in neoplastic

ISSN:0003-276X    

DOI:10.1002/ar.1092170208

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

年代:1987

数据来源: WILEY

摘要:

AbstractBiopsies of the pancreas head, tail, and uncinate regions of four baboons were processed for immunocytochemical (ICC) studies by using avidinbiotin‐peroxidase label for light microscopy (LM). Toluidine‐blue‐ or methylene‐blue‐stained 0.5‐μm sections of nonosmicated resin‐embedded tissue were viewed to locate areas of suitable islets. For ICC investigations, batches 10 μm apart of ten consecutive 1‐μm sections throughout ten islets from each of the three regions were immunolabelled for LM. Four slides in each batch were immunolabelled consecutively for insulin, glucagon, somatostatin, and pancreatic polypeptide, the fifth acting as one of the range of controls in each batch.The number of each of the four cell types was counted in at least ten immunolabelled islets from each of the pancreas heads, uncinate portions, and tails. The uncinate region and not the head, as in most mammals, was found to contain significantly higher numbers of pancreatic polypeptide (PP) cells and lower numbers of A (glucagon) and D (somatostatin) cells (P<.001). The PP cells occurred in clumps and not as described in other mammals as part of the mantle of A, D, and PP cells. PP and A cell numbers were significantly different for each region (P<.001), being lowest in the head for PP and in the uncinate process for A cells. D cell distribution was similar to that of the A cells whilst a significantly smaller number of B (insulin) cells was found in the tail compared with othe

ISSN:0003-276X    

DOI:10.1002/ar.1092170209

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe postnatal structural development of the thyroid gland of the Australian native bandicoot,Isoodon macrourus, was monitored and the onset of thyroid function (i.e., the secretion of thyroid hormones) was determined. Thyroid glands were obtained from bandicoots at days 1, 3, 11, 12, 13, 21, 25, 30, 34, 35, 39, 46, 48, 50, 59, 61, 75, 79, 83, and 163 of age and from adult animals, and the tissues were examined with the transmission electron microscope. The thyroid gland of the newborn bandicoot consisted of undifferentiated cells with no lumen. Follicles were first observed at day 12 postpartum, after which time rapid follicular growth occurred. The first signs of thyroid hormone secretion were seen at day 30 postpartum. A peak in thyroid activity seemed to occur around day 50 postpartum, and it correlated with the rapid rate of development of thermoregulatory capacity and hair development which occurred over the last 2 weeks of pouch life.

ISSN:0003-276X    

DOI:10.1002/ar.1092170210

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

年代:1987

数据来源: WILEY

摘要:

AbstractThe pig lymph node has an unusual structure in that tissue containing lymph nodules generally occupies a central position. Our aim was to describe the lymphatic pathways through this node. We studied the structure of these pathways with light and electron microscopy, made casts of lymphatic vessels and sinuses with Microfil, and studied the distribution within the node of subcutaneously injected carbon particles.Most afferent lymphatics penetrate deeply within the node, where they give off several branches to peritrabecular sinuses that ramify through centrally located nodular tissue. However, where an afferent lymphatic enters the node there is a subcapsular sinus over an area of nodular tissue that occupies a conventional superficial position. Some lymph reaches this sinus from the central peritrabecular sinuses, but there can also be direct communications between this sinus and the afferent lymphatic.After flowing through sinuses in nodular tissue, lymph enters tissue that is analogous to medullary tissue in other species. This tissue is of two types, one consisting mainly of a diffuse network of reticular cells around spaces up to 10–12 μm across, and one that more closely resembles conventional medullary tissue. Lymph then flows to collecting ducts, which lack valves, and then to efferent lymphatics.Our findings do not support suggestions that a purelyphysicalobstruction of lymphocytes in the lymph node accounts for the dearth of lymphocytes in efferent lymph of pi

ISSN:0003-276X    

DOI:10.1002/ar.1092170211

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

年代:1987

数据来源: WILEY