摘要:

AbstractThe sperm acrosome reaction is an example of exocytosis, accomplished through the fusion of the acrosomal and plasma membranes. As in other examples of exocytosis, the acrosome reaction is initiated by an influx of Ca++, which may promote fusion by binding to anionic sites on adjacent bilayers. In this study we used ruthenium red (RR) and cationic ferritin (CF) to detect anionic sites on the surfaces of acrosomal and plasma membranes of guinea pig spermatozoa. These probes indicate a dense concentration of anionic sites on the cytoplasmic surface of the acrosomal membrane. Higher concentrations of salt (NaCl) were required to inhibit cationic probe labeling of the cytoplasmic surface of the acrosomal membrane compared to the concentration needed to inhibit the plasma membrane binding. The added NaCl also increased the separation of the plasma from the acrosomal membrane. Low‐pH buffers stop cationic probe labeling of both membranes. Sections tangential to the acrosomal membrane revealed that the cation probes bound in a linear pattern, similar to the periodicity and distribution of intramembraneous particles observed in freeze‐fracture replicas. Following fusion of the plasma and acrosomal membrane during the acrosome reaction, we could no longer detect a dense concentration of anionic sites on the cytoplasmic surface of the fused vesicles. The results indicate that the dense concentrations of anionic sites are either masked or lost following fusion with the overlying plasma membr

ISSN:0002-9106    

DOI:10.1002/aja.1001730402

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

年代:1985

数据来源: WILEY

摘要:

AbstractCell membranes of normal human nasal and tracheal epithelium were characterized by means of freeze‐fracture preparations. These investigations illustrated a predictable variability in the distribution of membrane‐associated particles on PF‐faces of different cell types and in different regions of the same cell. Details of the fine structure and variability of tight junctional complexes in different cell types are presented as are ultrastructural perspectives of cell membrane involvement in ciliogenesis and in mucus secretion. Because ciliogenic profiles and nascent tight junctional complexes were observed more frequently in nasal epithelial cells, these features provided markers of cellular differentiation. Based on the frequent appearance of such indicators, these observations suggested that cell turnover may be more rapid in the region of the nasal turbinates than in the trachea. There was no appreciable evidence of ultrastructural variability between the epithelial cell membranes of similar cell types in the upper and lower respiratory

ISSN:0002-9106    

DOI:10.1002/aja.1001730403

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe epiphyseal cartilage in mouse tibia and fibula was investigated with the freeze‐fracture method. Cytodifferentiation of growth plate chondrocytes was found to be marked by changes in both cell membrane and extracellular matrix vesicle membranes. Exocytosis and endocytosis were observed in all zones of differentiation, with endocytosis being predominant in the reserve and proliferative zones and exocytosis occurring with greatest frequency during hypertrophy. Intramembraneous particles (IMPs) on the plasma membrane were distributed evenly on the reserve and proliferative cell membranes, whereas in the hypertrophic zone IMPs tended to be distributed asymmetrically. Several types of matrix vesicles were identifiable on the basis of IMP distribution: IMP‐free, IMP‐aggregated, and IMP‐random. The distribution pattern of IMPs on vesicles varied with differentiation of the chondrocytes. For proliferative and prehypertrophic cells, most matrix vesicles belonged to the IMP‐random category. IMP‐aggregated and IMP‐free matrix vesicles became increasingly frequent in the later stages of differentiation, particularly in the late hypertrophic stage. IMPs were observed more frequently on the convex protoplasmic fracture face of matrix vesicles than on the concave exoplasmic fracture face, as was also observed for the plasma membrane. Matrix vesicles formation appears to occur by budding from chondrocyte projections and bulges at the smooth surfaces of the cells and from cell disintegration. Crystals of mineral were apparent in cross‐fractured matrix vesicles of the calcifying zone, but not in

ISSN:0002-9106    

DOI:10.1002/aja.1001730404

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

年代:1985

数据来源: WILEY

摘要:

AbstractSubcutaneous implantation of bone chips into normal and osteopetrotic (ia) rats results in the formation of multinucleate giant cells (MNGCs) adjacent to the bone surface. In this study the resorptive and morphological characteristics of the cells surrounding these implants were assessed to determine if the bone‐resorbing defects seen iniaanimals would be mimicked, thus giving validity to the use of this system as a model for the study of osteoclastic lineage and function. Direct measurement ofin vivobone resorption was achieved through the use of45Ca‐labelled bone‐chip pairs that were primarily osteoid‐exposed and freeze‐thawed (FT), primarily mineral‐exposed and bleached (B), or primarily mineral‐exposed and collagenase‐treated (CT). Comparison of the45Ca content of implanted chips to that of controls indicated the total45Ca release during a two‐week implantation period. There was no significant difference in the amount of label released between normal andiaanimals. Both normal andiarats showed 23% greater total45Ca release from mineral‐ versus osteoid‐exposed matrix. Cellular events occurring on the bony substrate were evaluated by light and electron microscopy. At 3 days, bone chips were surrounded primarily by mononuclear cells. By 14 days, MNGCs were present at the bone surface in bothiaand normal animals. In mineral‐exposed implants, 40–50% of the bone surface was covered by MNGCs as compared to 20% of the osteoid‐exposed surface. These MNGCs possessed occasional clear zones, but did not exhibit ruffled borders; therefore, they could not be classified as osteoclasts. Thus, the defects seen iniamutants were not reproduced in this implant system. The45Ca release that occurred was probably due to the action of mononuclear phagocytes and macrophage polykaryons rather than to true o

ISSN:0002-9106    

DOI:10.1002/aja.1001730405

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

年代:1985

数据来源: WILEY

摘要:

AbstractA stereological approach to studying the architecture of the ventral and dorsal prostates of the Syrian hamster is described. In this approach, the prostate is considered to consist of acinar and interacinar compartments. The acinar compartment is divided into luminal, epithelial, lamina proprial, and muscular stromal compartments. Volume fractions of acini and interacinar tissue are calculated with reference to the volume of the gland; those of the acinar components are calculated with reference to the acinar volume. Volume fractions are determined from point counts. The surface fraction of the secretory epithelium is determined from intercept counts, with reference to the volume of the epithelium. By assuming that the acini are cylindrical, the acinar length fraction is calculated with reference to the volume of the gland. Absolute values for the volumes of different components, epithelial surface area, and acinar length can be determined from the weight of the gland, its specific gravity, and the volume fraction of that component, or epithelial surface fraction, or acinar length fraction, respectively. Finally, from these values and assuming a cylindrical shape for acini, characteristics of the typical acinus, including its radius, the thicknesses of its epithelium, lamina propria, and muscular stroma, and the amount of mucosal folding can be calculated from simple geometrical formulae. This approach is illustrated from a consideration of the ventral and dorsal prostates of 20‐week‐old Syrian hamst

ISSN:0002-9106    

DOI:10.1002/aja.1001730406

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

年代:1985

数据来源: WILEY

摘要:

AbstractShort‐day photoperiods and castration both cause reductions in the weights of male accessory sex glands. In the Syrian hamster, we have found that the ventral prostate loses less weight following these treatments than does the dorsal prostate. In this paper, we report on the effects of the pineal and of castration on the structural integrity of these glands, as assessed by stereological techniques. Short days result in little alteration to the ventral prostate or its acinar composition. The typical acinus is narrower following 10 weeks in short days. The ventral prostate also responds to castration with a narrower acinus, and, in addition, it shows a decrease in the epithelial volume fraction and increases in those of the lumen and muscular stroma. In neither case is there a change in the proportion of the gland consisting of acinar or interacinar components. Short‐day photoperiods and castration generally show similar effects in the dorsal prostate. In both cases, there are increases in the proportion of the gland made up of interacinar tissue. Within the acini, there are decreases in the volume fractions of lumen and large increases in those of lamina propria and muscular stroma. Following both treatments, typical acini are narrower and show reduction in the thickness of the epithelium and increases in the thickness of the lamina propria and muscular stroma.Thus, in the ventral prostate, both short days and castration lead to subtle changes which are different with each treatment and which differ from those that occur in the dorsal prostate. In the dorsal prostate, there are relative increases in the proportions of nonepithelial elements following both of these treatments. These results are discussed in relation to the mode of action of the pineal in causing accessory sex gland regress

ISSN:0002-9106    

DOI:10.1002/aja.1001730407

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

年代:1985

数据来源: WILEY

摘要:

AbstractThe development, differentiation, and pattern formation of isolated distal parts of avian leg buds that had grown ectopically on the chorioallantoic membrane (CAM) or in the coelomic cavity were studied. The grafts grown on the CAM invariably gave rise to cartilage and soft connective tissue. In some cases muscle tissue was also found. The CAM grafts did not undergo overt morphogenesis and pattern formation. A high percentage of grafts grown in the coelomic cavity showed a close approximation to normal limbs. The presence of proximal structures depended on the stage of development of the donor at the time of the operation, on the size of the grafts, and on the site to which the graft was attached within the coelom. The presence of anteroposterior structures depended on the shape of the graft. The pattern formation of this axis was found to be independent of the presence of the zone of polarizing activity at the proximal posterior border of the bud. The distance from the tip of the bud to the line of most distal colonization by myogenic cells was determined. The speed of migration of the myogenic cells can be considered to be constant. In muscleless legs, tendons developed at the levels of the phalanges and the tarsometatarse. They degenerated, however, in the absence of muscle from day 9 on, from proximal to distal areas. CAM grafts as well as coelomic grafts were well vascularized. The endothelial cells of the blood vessels were of host origin. In coelomic grafts, nerves were present with Schwann cells of host origin. The nerves and blood vessels showed a distribution that resembled that in normal legs.

ISSN:0002-9106    

DOI:10.1002/aja.1001730408

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

年代:1985

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001730401

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

年代:1985

数据来源: WILEY