Biomedical subjects

L R de França

Publications and source records attributed to L R de França.

7 recordsLinked to original sources

PubMed1995

Morphometry of rat germ cells during spermatogenesis.

BACKGROUND: There has never been a study of the components of germ cells as they progress through spermatogenesis. METHODS: The structural changes taking place in rat germ cells, from spermatogonia to late spermatids, were studied utilizing morphometric techniques conducted largely at the ultrastructural level. RESULTS: Volume and surface area parameters for virtually all cellular and subcellular features were obtained for nine periods during the spermatogenic cycle. Virtually all germ cell components show dynamic properties associated with specific phases of their development. CONCLUSIONS: The data provided can be used in an objective way to characterize structural changes taking place during spermatogenesis and to relate those structural changes to functional properties of germ cells.

Acrosome↗

PubMed1995

Characteristics of mitotic cells in developing and adult testes with observations on cell lineages.

This report describes characteristics of dividing cells, primarily in developing (10-40 day) rat testis and relates the structure of the dividing cells to the structure of interphase cells. Mitotic cells were characterized in seven zones. Dividing Sertoli cells were seen prior to day 15 and possessed distinct characteristics as compared with dividing germ cells. Myoid cells showed morphological characteristics of precursor myoid cells; 'clear cells' self-replicated in the myoid cell layer; adult-type Leydig cells, some containing lipid, differentiated early (10th-15th postnatal days) from fibroblast-like cells of the multilayered tubule wall and later (15th-25th postnatal days) from dividing differentiated and semi-differentiated Leydig cells within the lymphatic space; fibroblastic cells arose from cells with similar morphological characteristics; semi-differentiated Leydig cells divided, and differentiated Leydig cells in the lymphatic space self-renewed; undifferentiated perivascular cells most likely gave rise to Leydig cells, pericytes; arteriolar smooth muscle cells and vascular endothelial cells arose from division of the pre-existing respective cell types. Fetal Leydig cells appeared to remain but, with time, they appeared to lose their lipid. The data suggest that (1) early recruitment of Leydig cells from undifferentiated peritubular fibroblast-like cells, (2) later mitosis of differentiated and semi-differentiated Leydig cells primarily in the interstitium but also in the perivascular region, and (3) the continued presence of pre-existing Leydig cells from the fetus constitute the adult population. Leydig cell division in the adult mouse was documented. This study provides the necessary information for the recognition of cell divisions to study of cell lineages among testis cells.

Animals↗

PubMed1995

Building a testis.

Specific cellular, subcellular and acellular components of the rat testis including the capsule, the peritubular tissue (tunica propria) and the lymphatic endothelium were analyzed using morphometric techniques at cellular and subcellular levels to yield volume and surface area data. These data were integrated with previously published data for other cellular components of the rat testis to provide information about the volumetric composition for virtually every component of this organ. For major cell types (Leydig, Sertoli, myoid cells and germ cells) the data are expressed to the subcellular level in terms of volume and, in some instances, surface area. Graphic portrayals of testis constituents are used for rapid visual understanding of testis structure. The data presented herein are useful in conjunction with biochemical data to describe physiological properties of cells and cell components and also for understanding how structure differs under experimental and in pathological situations.

Animals↗

PubMed1994

Hormone sensitivity of germ cells in stage XIV and in stage I of the rat spermatogenic cycle.

Previous data have been inconclusive with respect to whether the meiotic degenerations that occur in stage XIV of the spermatogenic cycle are increased after hypophysectomy. Meiotic cell degenerations in Stage XIV and early Stage I of the spermatogenic cycle were enumerated to determine if the advanced generation of meiotic cells were influenced by hormonal deprivation subsequent to hypophysectomy and, if so, could cellular degenerations be prevented by supplementation with either testosterone or recombinant FSH during the period of hypophysectomy. The animals utilized were either pituitary-intact rats or rats hypophysectomized for 3 or 10 days. Hormone supplementation began at day 3 post-hypophysectomy and continued until day 10 at which time all animals were sacrificed. The numbers of degenerating meiotic figures (metaphase to telophase of the first and second meiotic division) as expressed per Sertoli cell nucleus or nucleolus were not increased significantly 10 days after hypophysectomy as compared with animals hypophysectomized for 3 days or with pituitary-intact controls. Exogenously administered testosterone and FSH had no effect on the numbers of degenerating meiotic germ cells in hypophysectomized animals. These data indicate that stage XIV metaphase to telophase spermatocytes are not hormone sensitive. However, it was determined that there were new cell types degenerating at Stage XIV and I of the spermatogenic cycle. These were interphase secondary spermatocytes and step 1 spermatids and were seen in stages XIV and I, respectively. These cell degenerations were found in low numbers in Stage XIV and I in either FSH-treated or testosterone-treated rats, suggesting their hormone sensitivity. Thus it is possible that Stages XIV and I are hormone sensitive stages.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

The urethral glands of male mice in relation to depletion of secretory granules upon mating.

The present study describes the effects of mating on urethral gland acinar cells in male mice. Histological and morphometric analysis demonstrated that there was a depletion of secretory granules in the urethral glands during mating. However, no change occurred in the rough endoplasmic reticulum containing tubular elements. The results indicate that the urethral glands are functional during mating. The timing of their granule depletion suggests that urethral gland secretions may contribute to the formation of semen or the copulation plug.

Animals↗

PubMed1993

Sertoli cell cycle: a re-examination of the structural changes during the cycle of the seminiferous epithelium of the rat.

Seminiferous tubules in mammals are composed of cell associations that show a cyclic pattern of renewal and development. The cyclic nature of germ cell development suggests that the cells supporting the spermatogenic process, the Sertoli cells, might also differ structurally during the spermatogenic cycle in terms of the quantity of their constituents. In the present study, cyclic differences in volumes, and surface areas were determined using a sampling technique at the electron microscope level that proportionally samples the Sertoli cell within the seminiferous tubule. Among the many parameters studied, only the surface area of the cell, the volume of lipid, and the volume and surface area of the rough endoplasm reticulum were shown by statistical analysis to vary cyclically. Regarding rough endoplasm reticulum, the volume and surface area of this organelle peaked at mid-cycle and its low was recorded near the end of the cycle, exhibiting an approximate 15-fold difference between extremes. The rough endoplasm reticulum parameters generally correlated with known patterns of protein secretion within the tubule and with the secretion of specific proteins as well as the factors important in controlling protein secretion. Many Sertoli cell structural parameters suggested to be influenced cyclically in the rat in other studies could not be confirmed by the present study. Methodological differences in the present study and past studies are discussed as potential sources of error for these discrepancies.

Animals↗

PubMed1993

Surface and surface-to-volume relationships of the Sertoli cell during the cycle of the seminiferous epithelium in the rat.

The surface relationships of the Sertoli cell and the surface relationships of the Sertoli cell in comparison to the changing volumes of developing germ cells were studied using morphometric techniques at periods representing nine groupings of the fourteen defined periods in the cycle of the seminiferous epithelium of the adult rat. No cyclic variation in the total Sertoli plasma membrane surface area was noted. Cyclic variations were noted in the area of the Sertoli cell surface that faces the basal compartment germ cells, but not the basal lamina. No cyclic variations were noted in the amount of contact of the Sertoli cells with each other at the level of the Sertoli cell barrier. However, when areas in the adluminal compartment were studied, significantly less Sertoli-Sertoli contact was seen in stages V through VII than in other stages with the exception of stages II-IV. Surface contact of germ cells with Sertoli cells increased progressively as germ cells entered the intermediate compartment and progressed to late spermatids. However, a calculation of the surface-to-volume ratio showed that surface increases of the Sertoli cell in relation to the volume of germ cells were greatest in elongating spermatids past step 12 of spermiogenesis. The area in which Sertoli ectoplasmic specializations faced germ cells was determined throughout spermatogenesis, and these data demonstrated that the first appearance of ectoplasmic specialization was at the mid-pachytene phase. They also showed that stage VIII was a period when ectoplasmic specialization loss from the cell surface was evident. Less Sertoli ectoplasmic specialization face step 8 and step 19 spermatids than comparable germ cell types at other stages. In addition to Sertoli cell surface area changes during the cycle, volumes of individual germ cell types were determined for the first time. The data presented allow an objective understanding of the complex structure and relationships of the Sertoli cell and provide a basis for understanding functional changes and interpreting biochemical data.

Animals↗