摘要:

AbstractStructural features of the mouse and rat manchette and the role of the manchette in shaping the spermatid nucleus were investigated. Rod‐like elements about 10 nm in diameter and 40–70 nm in length were seen linking the innermost microtubules of the manchette and the outer leaflet of the nuclear envelope in step 8 through step 11 rat and mouse spermatids that either had been routinely fixed for electron microscopy or had been isolated and detergent extracted. Rod‐like linkers were also seen joining the nuclear ring to the plasma membrane and nuclear envelope. These linkers may ensure that under normal conditions the manchette remains in a defined position relative to these membranous components. A variety of compounds (taxol, cytoxan, and 5‐fluorouracil) were found to perturb the manchette and to affect nuclear shaping. In addition,sysandazhmutant mice were used to determine the consequences of defective manchette formation. These genetic conditions and chemical treatments either produced manchettes that were not in their normal position (azh, sys, and taxol) and/or caused the manchette to appear abnormal (azh, sys, cytoxan, 5‐fluorouracil, and taxol), and all resulted in a deformation of the step 9–11 spermatid nucleus. In all instances where the manchette was present, either in normal or ectopic locations, thesectioned nuclear envelope was parallel to the long axis of the microtubules of the manchette. In general, areas of the nuclear envelope where the manchette was not present, or where it was expected to be present but was not, were rounded (normal animals,sys, cytoxan). In addition, there are indications using certain compounds (cytoxan and 5‐fluorouracil) as well as in theazhandsysmouse that the manchette may exert pressure to deform the nucleus. It is suggested that the rod‐like linkages of the manchette ensure that the nuclear envelope remains at a constant distance from the manchette microtubules and that this is a major factor acting to impart nuclear shape changes on a region of the head caudal to the acrosome during the early elongation phase of spermiogenesis. The manchette microtubules, which are also known to be linked together, may act as a scaffold to deform this part of the nucleus from its spherical shape, perhaps in concert with forces initiated by other structural elements. Evidence fromsysanimals indicates that structural elements, such as the acrosomal complex over the anterior head (acrosome‐actin‐nuclear envelope), may affect nuclear shaping over the acrosome‐covered portion of the spermatid head. It is suggested that chromatin condensation primarily reinforces the shape changesalreadybrought about by the manchette and other structural elements acting on the nucleus. After chromatin condensation, spermatid nuclear sh

ISSN:0002-9106    

DOI:10.1002/aja.1001920202

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

年代:1991

数据来源: WILEY

摘要:

AbstractSegments and subsegments are the smallest unit of synchrony thus far described within longitudinal sections of seminiferous tubules. It is known that cells in a clone joined by intercellular bridges are at the same phase of development and are also thought to be units of synchrony. This study was designed to determine if it is possible that the synchrony seen in cells joined by intercellular bridges is the same as that cataloged along the long axis of the seminiferous tubule. In the present study, the maximum number of rat spermatids joined by intercellular bridges (a clone) was obtained. It was hypothesized that if the clone size were larger than the smallest known units of synchrony (segments or subsegments) in the long axis of the seminiferous tubule, then intercellular bridges would most likely govern the synchronous development of segments or subsegments (or finer subdivisions thereof). If the clone size is smaller than the number of cells present in a segment or subsegment, then other factors must govern synchrony in the longitudinal aspect of the tubule. In the determination of spermatid clone size, rat testes were injected with cytochalasin D which opens intercellular bridges of a spermatid clone to produce large symplasts. The number of nuclei in the symplasts was determined from serially sectioned tissue, by drawing nuclei with a camera‐lucida, and by counting nuclei. After extensive examination of tubules, the number of spermatids found in the suspected five largest clones observed was determined to be 650, 607, 338, 240, and 177. The segment and subsegment length and the density of spermatids per given tubule length were determined from previously published data. The numbers of spermatids accommodated in the smallest segment and subsegment were 128 and 30, respectively. Our observations indicate that synchronous development of germ cells along the length of the tubule is controlled by intercellular bridges since the number of conjoined cells required to fill a segment or subsegment is more than the number of cells in the smallest arbitrarily identified units of synchrony cataloged to dat

ISSN:0002-9106    

DOI:10.1002/aja.1001920203

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe localization of proacrosin was determined by using colloidal gold labeling and electron microscopy of boar germ cells during spermiogenesis to post‐ejaculation. Proacrosin was first localized in round spermatids during the Golgi phase of spermiogenesis; it was associated with the electron‐dense granule, or acrosomal granule that was conspicuous within the acrosome. It remained within the acrosomal granule during the cap and acrosome phases of spermiogenesis. At these stages, there was no apparent association of the proacrosin molecule with the acrosomal membranes. During the maturation phase of spermiogenesis, proacrosin was seen to become dispersed into all regions of the acrosome except the equatorial segment. When sperm from different segments of the epididymis and ejaculated sperm were examined, localization was observed throughout the acrosome except for the equatorial segment. Here proacrosin appeared to be localized on both the inner and outer acrosomal membranes as well as with the acrosomal matrix, although further studies are required to verify the membrane localization. No labeling was seen on the plasma membrane. These data suggest that the synthesis and movement of proacrosin to sites in the acrosome are controlled by an as yet unknown process. The absence of proacrosin on the plasma membrane of mature ejaculated sperm makes it unlikely that this enzyme plays a role in sperm‐zona adhesion prior to capacit

ISSN:0002-9106    

DOI:10.1002/aja.1001920204

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

年代:1991

数据来源: WILEY

摘要:

AbstractAs cancer survival rates improve, there is increasing concern about the adverse effects of chemotherapeutic agents on male fertility. Five chemotherapeutic agents (amethop‐terin, AP or methotrexate; doxorubicin, DX; cytoxan or cyclophosphamide, CP; cisplatinum, CDDP; and 5‐fluorouracil, 5‐FU) which belong to three different categories of chemotherapeutic agents (antimetabolite, antibiotic, alkylating agent, alkylating agent, antimetabolite, respectively) were given systemically to adult rats to determine the short‐term morphological patterns of response in the testis, and the testes were examined by light microscopy. Morphological patterns of response were found to be highly characteristic for each agent, and some shared morphological responses were evident. All except one chemotherapeutic agent (5‐FU) caused spermatogonial damage. Among the defects seen were probable degenerating meiotic spermatocytes (CDDP), presence of micronuclei (DX), “arrested” spermatid development (5‐FU), and abnormally shaped step 15 spermatids (5‐FU). Damage that could be due to the effect of an agent on the Sertoli cell was failure of sperm release (5‐FU, CDDP, DX, and AP), increase in the Sertoli cell lipid (5‐FU), and malorientation of step 8 spermatids (5‐FU, DX). The varied patterns of damage observed are a possible explanation of why the reproductive recovery potential in cancer patients undergoing chemotherapy is var

ISSN:0002-9106    

DOI:10.1002/aja.1001920205

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

年代:1991

数据来源: WILEY

摘要:

AbstractTestes of mice with the recessive insertional mutation termedsymplastic spermatids (sys)were assessed for structural and developmental abnormalities. Homozygous (sys/sys) males are infertile due to an abnormality in spermatogenesis leading to azoospermia. The major interruption to spermatogenesis occurs when the intercellular bridges that connect round spermatids open prematurely resulting in the formation of symplasts. Symplasts contain as many as 285 nuclei. Development of spermatids within symplasts is arrested just before, or just after, elongation of the spermatid nuclei begins. Symplasts degenerate and appear to be phagocytized by Sertoli cells and by intratubular macrophages. In addition, degeneration of young round spermatids and also spermatocytes occasionally is observed. Spermatocyte degeneration is substantial in some tubules and leaves them depleted of cells other than basal compartment cells. Sertoli cell abnormalities are prominent and include intracellular vacuolation, absence of apical processes surrounding round spermatids, degeneration, and occasional sloughing. Although reduplication and infolding of the basal lamina is also seen, this does not appear as a common phenomenon. Thesysphenotype is first manifest in animals between 19 days and 22 days of age. Considerable variability is seen in testis histology of prepubertal animals; some display degenerating pachytene spermatocytes and virtually no Sertoli cell vacuoles, while others display vacuoles without apparent elevated numbers of degenerating spermatocytes. Although this study has not revealed the primary cell type(s) affected by the insertional inactivation event, it is possible that the abnormalities in the Sertoli cells are responsible for germ cell degeneration as it is generally recognized that deficits in the Sertoli cell can result in major germ cell abnormalities but not vice versa.

ISSN:0002-9106    

DOI:10.1002/aja.1001920206

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe structural properties of pelleted prepubertal Sertoli cells (pre‐culture pelleted cells) from 19‐day‐old rats and of similar cells cultured for 7 days were compared with Sertoli cells from the intact animal (testis tissue from 19‐and 26‐day‐old rats, thein vivogroups). Sertoli cells from freshly isolated pellets and those cultured for 7 days were similar in cell and nuclear volumes to theirin vivocounterparts. Cell volumes, organelle volumes, and organelle volume densities of newly isolated Sertoli cells were similar to those of sectioned cells taken from the 19‐day‐oldin vivogroup, indicating that the procedure for isolation does not grossly alter Sertoli cells. Mean height of cells cultured for 7 days was significantly lower than that of cells from intact animals at 19 and 26 days of age.In vivo, Sertoli cells of 26‐day‐old animals displayed increased organelle volumes and organelle surface areas compared with those from 19‐day‐old animals; volume densities and surface densities remained relatively constant, indicating thatin vivo, organelle growth is in proportion to growth of the cell. Most organelle volume and surface densities were not significantly different when 19‐day‐oldin vivocells and pre‐culture pelleted cells were compared. Many organelle volume and surface density values were significantly less in cells grown in culture for 7 days as compared to freshly isolated pelleted cells. After 7 days of culture, most Sertoli cell organelles were significantly less in both volume density and surface density, as compared to thein vivocell groups (19 or 26 day). This indicates thatin vitrothe organelles do not develop in proportion to the growth of the cell. After 7 days in culture, the absolute volumes and surface areas of the organelles remained generally unchanged as compared to cells from 19‐day‐old animals. The data show that Sertoli cells grow in volumein vitrolike theirin vivocounterparts; however, their subcellular features, although well maintained, do not develop in proportion to the cell. This suggests that short‐term cultures are a more ideal system in which to study biochemical responses. Also, cultured prepubertal Sertoli cells are most appropriately used to study prepubertal Sertoli cell function. This is the first study to quantify developmental changes in Sertoli cell structurein vivoas well as to compare them with

ISSN:0002-9106    

DOI:10.1002/aja.1001920207

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

年代:1991

数据来源: WILEY

摘要:

AbstractThe present study was undertaken (1) to document structural and functional changes in the testes of seasonally breeding woodchuck during active and inactive states of spermatogenesis and (2) to evaluate the ability of exogenous gonadotropins to reinitiate spermatogenesis outside the breeding season. During seasonal gonadal inactivity, there were significant (P<0.05) reductions in volumes of several testicular features (testis, seminiferous tubules, tubular lumen, interstitial tissue, individual Leydig cells, Leydig cell nuclei, and Leydig cell cytoplasm) as compared with gonadally active animals. The diameter of the seminiferous tubules was decreased by 26%, and Leydig cell numbers also declined in the regressed testes. These changes were accompanied by a decline in testosterone (T) levels in both plasma and testis, and reduction in epithelial height of accessory reproductive organs. A hormonal regimen was developed that would reinitiate spermatogenesis in captive, sexually quiescent woodchucks. A combination of PMSG and hCG markedly stimulated testicular growth and function and restored spermatogenesis qualitatively. Quantitatively normal spermatogenesis was restored in 2 of 6 treated males. Morphometric analyses revealed substantial increases in seminiferous tubular diameter and in the volume of seminiferous tubules, tubular lumen, total Levdig cells, and individual Leydig cells in the hormone‐treated animals. These increased values corresponded to 99, 75, 68, 51, and 200%, respectively, of the values measured in naturally active woodchucks. Leydig cell numbers, however, remained unchanged and approximated only 31% of the number found in naturally active testes. Hormonal stimulation also resulted in a significant rise in serum T as well as in the total content of testicular T, and a marked increase in epithelial height in various accessory reproductive glands. The most effective hormonal protocol for stimulating spermatogenesis was treatment with 12.5 IU of PMSG twice a week for 4 weeks followed by 12.5 IU of PMSG + 25 IU of hCG twice a week for 4 week

ISSN:0002-9106    

DOI:10.1002/aja.1001920208

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

年代:1991

数据来源: WILEY

ISSN:0002-9106    

DOI:10.1002/aja.1001920201

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

年代:1991

数据来源: WILEY