bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electron microscopic observations on the postnatal differentiation of the seminal vesicle epithelium of the laboratory mouse
Authors: Deane Helen Wendler , Wurzelmann Sarah 
Published: February 2005

AbstractThe cytological changes occurring in the epithelium of the mouse seminal vesicle between 5 and 49 days of postnatal life have been traced by electron microscopy.Initially the epithelium was composed of typical immature columnar cells. During the second week of life, the principal changes were: rapid cell proliferation, followed by increases in the amounts of organized ergastoplasm and Golgi material. During the third week, dense secretory material appeared in Golgi cisternae and then in the lumen of the gland.The parallelism between these changes and those found in maturing pancreatic acinar tissue has been assessed. Comment is made on the attachment of ribosomes to endoplasmic reticulum in the initiation of protein‐secretory activity, and the importance of the subsequent proliferation of ergastoplasmic and Golgi membranes. The evidence for relating these cytological and secretory alterations in the seminal vesicle to a rising titer of androgen during the prepuberal period has been cited.Other observations included: (a) Evidence for a considerable amount of cellular sloughing and resorption during the first two postnatal weeks; (b) an association of mitochondria with developing desmosomes, and (c) the appearance of basal cells first during the second week of postnatal life, thus suggesting that they arise by dedifferentiation of columnar cells.
Effects of gonadectomy, androgen administration and thyroidectomy on the cytology of the pituitary gland of the five‐striped palm squirrel, Funambulus pennanti (Wroughton)
Authors: Dhaliwal Gurmeet K. , Prasad M. R. N. 
Published: February 2005

AbstractChanges in the cytology of the pituitary gland of the palm squirrel, Funambulus pennanti (Wroughton), following gonadectomy, androgen administration and propylthiouracil treatment are described.Increase in gonadotroph cell number and granulation reaches its maximum by one week after gonad ablation and is maintained at this level during the next three weeks, following which there is a gradual decline. Female squirrels show hypertrophied cells with prominent Golgi apparatus at 16 weeks after gonadectomy whereas males show similar changes four weeks after castration, changes which are still clearly noticeable at the end of 48 weeks. Castration cells or “signet‐ring cells,” so characteristically seen in rats, do not occur in gonadectomized squirrels. Thyrotrophs are not affected by gonadectomy. Acidophils quickly decrease in number following gonadectomy, and are maintained at this level throughout the post‐castration period.Administration of testosterone propionate to one week castrates causes degranulation in some gonadotrophs while others are coarsely granulated and deeply stained. The degranulated cells are interspersed with the other deeply stained gonadotrophs in the lateral halves of the pars anterior. Testosterone propionate administration to 12‐week castrates produces no marked changes in the granule content of the gonadotrophs.Propylthiouracil treatment causes degranulation of cells located in the anteromedian zone of the pars anterior. Degranulation is partial in animals treated for 15 days but is compete after 30 days of treatment. Acidophils are partially degranulated after 30 days of propylthiouracil treatment.
The ultrastructure of the gastric mucosa in normal and hypophysectomized rats
Authors: Corpron Richard E. 
Published: February 2005

AbstractThe objectives of this study were to observe with the electron micro scope (a) the epithelial cell types found in the neck and isthmus of the gastric fundic gland of the rat, and (b) the effects of hypophysectomy on the gland. The following cell types were distinguished in the neck of the fundic gland of the rat: nondifferentiated cell, immature surface cell, mucous neck cell, and neck parietal cell. In the normal gland, these cell types resembled each other in the possession of a ground cytoplasm and nucleoplasm of low density, a poorly developed endoplasmic reticulum, few mitochondria and numerous free ribosomes. The most important structural difference between mucous neck and immature surface cells was the contrasting density of the secretory granules; both cell types differed from the nondifferentiated cell primarily in the presence of their characteristic secretory granules. The neck parietal cell appeared to be a developmental form between the immature surface cell and the mature parietal cell. No changes were observed in these cells to result from hypophysectomy.Hypophysectomy caused marked involutional changes in the chief cell which involved mainly the organelles most directly concerned with protein synthesis, i.e., the ergastoplasm and Golgi apparatus. These effects were correlated with the loss of basophilia and secretory granules and with the reduction in cell size and capacity to secrete pepsinogen which were described previously. In contrast, the parietal cell, which is concerned with electrolyte transport, was affected much less.
Changes in endometrial vascularity during implantation and pregnancy in the rabbit
Authors: Hafez E. S. E. , Tsutsumi Y. 
Published: February 2005

AbstractSixty‐five pregnant rabbits were autopsied at different stages of pregnancy 2 to 28 days post coitum (p.c.). The vascularity of the endometrium and placenta was studied using intervascular injections of neoprene latex cast, by clearing injected specimens and by the study of frozen and paraffin embedded sections. At 6 days p.c. the implantation sites were identified; the endometrium at the inter‐conceptus was similar to that during pseudopregnancy. The subepithelial capillary plexus increased in thickness, reaching a maximum at 6–11 days p.c. Marked endometrial branching occurred 10 days p.c. After 15 days p.c. the endometrium formed a thin irregular layer. Most of the endometrial epithelial cells showed cytoplasmic projections at 6 days p.c. and were transformed into syncytial epithelial cells 8 days p.c. At 24–28 days p.c. the conceptus and interconceptus areas were unidentifiable.The size of the obplacental folds diminished at 6 days p.c., and the placental folds increased in size after 7 days p.c. At 9 days p.c. blastocyst attachment was observed histologically. The surface capillaries were dilated and changed into surface sinuses. Networks of blood pathways were established; the pathways connected with large veins in the core of the fold. The veins extended to the hemorrhage areas representing the origin of fetal placenta. The fetal vessels were recognizable near the base of the fetal placenta at 11 days p.c. The maternal circulation in the fetal placenta started before the fetal vessels reached the fetal placenta. At 10 days p.c. the perivascular sheath of the maternal vessels, in the placental folds, developed markedly as to replace most of the connective tissue. With advancing pregnancy the number of vessels within the maternal placenta decreased and some vessels increased in size. At 13 days p.c. the zone of separation was formed. At 15 days p.c. the lobes were formed in the fetal placenta; all placental elements were established anatomically. Subsequent stages were characterized by developmental changes in the fetal placenta and degenerative changes in the maternal placenta.
Renewal of spermatogonia in man
Authors: Clermont Yves 
Published: February 2005

AbstractThe spermatogonia of normal adult human testis were investigated in view of clarifying their mode of proliferation and renewal. Three main types of spermatogonia were identified: the dark type A spermatogonia (Ad) tentatively considered as the stem cells, the pale type A spermatogonia (Ap) and the type B spermatogonia (B), these being the more and more differentiated elements giving rise to preleptotene spermatocytes. The dark and pale type A spermatogonia were present in all stages of the cycle of the seminiferous epithelium, the type B spermatogonia were found in stages VI, I and II of the cycle and the preleptotene spermatocytes in stages III and IV of the cycle. The type A spermatogonia divided preferentially in stage V of the cycle and the type B spermatogonia in stage II of the cycle.Quantitative data on spermatogonia and preleptotene spermatocytes revealed that the cell ratio Ad: Ap: B: Pl was equal to 1:1:2:4. This indicated that the spermatogonial stem cells divided to produce equal numbers of new stem cells (Ad) and of the more differentiated pale type A spermatogonia (Ap). Each one of the latter gave rise to two type B spermatogonia which in turn produced four spermatocytes.The arrangement in pairs of the dark and pale type A spermatogonia throughout the duration of the cycle indicated that the mitoses of spermatogonial stem cells are “equivalent” in nature; therefore, the possibility of having “differential” mitoses to explain the renewal of spermatogonial stem cells should be abandoned. Lastly, the frequent arrangement of the two classes of type A spermatogonia in homogeneous clusters indicated that the impetus which facilitates the differentiation of stem cells into the more differentiated elements (Ap) may affect homogeneous and compact groups of stem cells.
The development and maintenance of myelinated tissue cultures of rat trigeminal ganglion
Authors: Winkler Gerald F. , Wolf Merrill K. 
Published: February 2005

AbstractTrigeminal ganglia of fetal or neonatal rats and mice have been cultured on collagen‐coated coverslips in Maximow assemblies. The methods which proved optimal and the natural history of the resulting cultures are presented in detail. Cultures formed abundant myelin, remained healthy for at least three months, and resembled previously described cultures of other primary sensory ganglia in most but not all respects. New features included an exceptionally high requirement for glucose and apparently for other nutrients, migration of some neuron somas, and the occasional occurrence of stable but abnormally formed myelin segments. The advantages and limitations of such cultures for experimental study of isolated nervous tissues are discussed.
Tolerance of the facial bones to impact
Authors: Hodgson Voigt R. 
Published: February 2005

AbstractA study of the tolerance of the facial bones to blunt impact has been conducted for the purpose of determining the mechanics and important parameters affecting fracture. Such information is urgently needed for the safe design of vehicles and protective equipment, and would serve a useful purpose as an aid in the diagnosis and treatment of facial injuries. Work to date has been concentrated around the zygomatic bone because of its amenability to mathematical analysis and susceptibility to damage due to its relative fragility and prominence. The force to fracture the bone has been found to be time dependent. For example, high forces up to 1,000 pounds can be tolerated for extremely short time durations of 3 milliseconds or less. Impacts lasting beyond 4 milliseconds produce fracture near 200 pounds. These figures are for a 1 inch square area, and it has been found that for impulses lasting longer than 4 milliseconds the tolerance of the zygomatic bone can be raised by a factor of 150 to 250% if the load is distributed over the entire bone. A linear fracture around one zygomatic bone has been found not to affect the structural integrity of the opposite side of the face, which fact has been very useful in comparing parameters on the same cadaver. In comparing the impact strength of three facial bones on each of four cadavers, the frontal bone has been found to tolerate a force three or four times higher than the mandible and zygomatic bone which are about equal.
A morphological analysis of the early implantation stages in the rat
Authors: Enders Allen C. , Schlafke Sandra 
Published: February 2005

AbstractBy making use of the known sequence of ovulation and fertilization in Holtzman rats, the Pontamine Blue reaction, and electron microscopy, the first stages in implantation were studied. Implantation is initiated when the blastocyst becomes clasped by the endometrium and hence assumes a fixed position (evening of day 5). At this stage, the trophoblast cells are in close association with the uterine epithelial cells, with interdigitating microvilli in places, but decidualization of the fibroblasts is just beginning. In the second stage of implantation the decidualized fibroblasts form a cup around the luminal epithelium. Evidence of adhesion of the cell membranes of trophoblast cells with the cell membranes of luminal epithelial cells can be seen at this time. The layer of fibroblasts immediately surrounding the luminal epithelium becomes epithelioid, resulting in a relative isolation of the luminal epithelium from its vascularization. This stage is well‐developed by the afternoon of day 6. By the morning of day 7, the luminal epithelium has disappeared from the region of the forming ectoplacental cone down to the level of the abembryonic trophoblast. The trophoblast cells on the lateral aspect of the blastocyst are directly in contact with the residual basement membrane of the luminal epithelial cells, and are separated by this structure and a small connective tissue cleft from the stromal cells. The importance of the relative isolation of the epithelium by the stromal reaction and the adhesion of the cell membrane of the trophoblast cells to the cell membranes of epithelial cells with regard to removal and phagocytosis of epithelial elements are discussed, and many of the cytological features observed during the process are described.
An experimental study of microscopic and submicroscopic lipid inclusions in hepatic cells of the mouse
Authors: Parks Harold F. 
Published: February 2005

AbstractLipid spherules of microscopic (1‐μ) and submicroscopic (300–1000 A) dimensions were studied by electron microscopy in livers of mice that were normally fed, fasted, fasted and refed, or fed fat‐free or high‐fat diets. Tissues were fixed by perfusion with osmium and post‐osmicated at 37°C.Submicroscopic inclusions were present in Golgi complex, endoplasmic reticulum, cytoplasmic vesicles near space of Disse, and in the space itself. The lipid of these inclusions was sufficiently unsaturated to be fixed and rendered insoluble by postosmication in all animals save those that were fed a diet rich in saturated fat or a fat‐free high‐carbohydrate diet (which induces synthesis of saturated fatty acids); in animals fed the two latter diets, the central mass of the inclusions escaped fixation and was dissolved during dehydration and imbedding. The inclusions were thus shown to reflect the character of the fatty acids most freely available in the cytoplasm of the hepatic cell in a given physiological state. On the basis of morphological and biochemical considerations, the submicroscopic inclusions were identified as secretion antecedents, elaborated by the liver for export to the blood.The larger lipid inclusions, which did not dramatically reflect changes in the degree of saturation of fatty acids available in the liver cell, were concluded to represent a more stable storage pool of hepatic‐cell neutral lipid.
Observations on the development of mouse blastocysts transferred to the testis and kidney
Authors: Porter David G. 
Published: February 2005

AbstractThe development of mouse blastocysts transferred to the kidney and testis was studied by light and electron microscopy. Approximately 50% of the blastocysts transferred to both sites survived for more than five days. Although trophoblast proliferation was characteristic of all 31 successful transplants which were serially sectioned, inner cell masses differentiated in only nine. Transplants were invasive in kidney but were encapsulated in testis. In both organs, however, transplants produced considerable hemorrhage. That trophoblast invades by phagocytosis was not substantiated in this study nor was there evidence that trophoblast elaborates a cytolytic factor. Although transplants caused gross lesions in the host organs, the cytology of cells in close proximity to invading trophoblast was almost normal. The only abnormal features observed were the presence of fine fibrillar material in the basal cytoplasm of renal tubule cells and a thickening of their basement membranes. No correlation could be demonstrated between the antigenic dissimilarity of host and transplant and extent of host tissue response.
The development of vagal innervation of the bovine stomach
Authors: McGeady T. A. , Sack W. O. 
Published: February 2005

AbstractThe development of the vagal innervation of the bovine stomach was examined in serial section from 15 embryos ranging from 10 to 20 mm crown‐rump length. Models of the gastric epithelium and nerves were made of an 11, 14, and 20 mm embryo. The vagal innervation of the stomach was also examined in six bovine fetuses ranging from 15 to 52 cm in length. The bovine stomach developed from a spindle‐shaped primordium at 10 mm to a four‐chambered organ at 20 mm. At 11 mm, the right and left vagus extended to a point dorsal to the heart where they divided into dorsal and ventral branches. The ventral branches fused to form the ventral vagal trunk and the dorsal branches fused to form the dorsal vagal trunk. At the 12 to 14 mm stage, both vagal trunks ran along the lesser curvature of the gastric pri‐mordium to the level of the developing abomasum. By 20 mm, the principal branches of the vagal trunks found in the adult were established and it became clear that the dorsal and ventral vagal trunks innervated areas of the ruminant stomach roughly comparable to the visceral and parietal (posterior and anterior (NA)) surfaces, respectively, of the simple stomach. The distribution of the vagal trunks in the fetuses was similar to that in the adult. Similarities in the development of the gastric nerves in man and ox were discussed.
An electron microscopic study of esophageal epithelium in the newborn and adult mouse
Authors: Parakkal Paul F. 
Published: February 2005

AbstractThe stratified squamous epithelium of the esophagus in the newborn and adult mouse was studied by histological, histochemical and electron microscopic methods. In the newborn, the cells located above the basal layer elaborate mucus. The relative abundance of Golgi zones and rough‐surfaced endoplasmic reticulum suggests the involvement of these organelles in the production of mucous granules. The membrane of mature mucous granules ruptures and their contents become dispersed in the cytoplasm. Mature mucous granules are not seen in the outermost cells which are about to be exfoliated. The process of exfoliation begins in the upper layer of the epithelium when the contiguous cell membranes separate and wide intercellular spaces are formed. While the cells reach the surface, the intercellular spaces widen, the cells lose contact and are shed. The distal surfaces of the cells in the upper layer are lined by a surface coat which consists of finely branched filaments.The esophageal epithelium of the adult mouse is similar to the epidermis and undergoes complete keratinization. The sequential development of differentiation products, namely the cytoplasmic filaments, membrane‐coating granules (MCG) and keratohyalin granules is seen as the cells migrate toward the surface. After their formation, MCG migrate toward the cell surface where they become confluent with the plasma membrane and are secreted into the intercellular space. Keratohyalin granules are also elaborated in large numbers and become dispersed as the cells become cornified. As the horny cells are formed the cell constituents such as the rough‐surfaced endoplasmic reticulum, Golgi complex, ribosomes, mitochondria and the nucleus disintegrate. The fully keratinized cell has a thickened envelope and is filled with filaments embedded in an amorphous matrix.
Morphogenetic studies of the rabbit. XXXVII. Genome, gradient growth pattern and malformation
Authors: Sawin P. B. , Gow Maryann , Muehlke Marjorie 
Published: February 2005

AbstractThe metameric organization of the skeleton provides a cartograph of reference points and a unique opportunity for analysis of the polygenic background of the genome and its potentialities for maintaining normality or inducing spontaneous malformation. The position of the vertebral borders indicates the relative size of the thoracic and lumbar regions or gradients. Analysis of homeotic variations in progeny from matings of specific parental vertebral formulae has provided a critical evaluation of the relative effects of gene Da with that of the residual genomes of races DA and IIIDa. Significant differences in shift of the vertebral borders have revealed the segregation of several modifying influences interacting at each border in each strain and with Da when it is present. The segregation patterns demonstrate the polygenic background of these variations and the interaction effects of DA and IIIDa genomes which respectively enhance or suppress the retardation effects of Da upon thoracic and lumbar gradients. Discussion of these observations with reference to convergence of broadly related concepts in the literature leads to the conclusion that many species or strain differences in experimental response, spontaneous malformations and polymorphisms may arise by similar interactions from residual heterozygosity of minor modifying genes within the genome. The importance of a more intensive scrutiny of the genome with reference to spontaneous and experimentally induced malformations is indicated.
Local uterine regulation of the corpus luteum
Authors: Fischer Theodore V. 
Published: February 2005

AbstractIn order to determine if the well known uterine inhibition of the guinea pig corpus luteum is a local effect, a series of partial hysterectomies were performed. Some groups were subjected to one‐half or three‐fourths hysterectomies alone, while in others one ovary was also removed on either the side retaining some or the side losing all uterine tissue. In addition, two groups in which all ovarian and uterine tissue was preserved were subjected to unilateral or bilateral complete surgical separation of all communicating structures between uterus and ovary. Sham‐operated, totally hysterectomized, and unilaterally ovariectomized groups were used as controls.In all groups in which an ovary left in the animal was separated from direct contact with its uterine horn, the estrous cycles became long and erratic, or were arrested completely due to the persistance of active corpora lutea in those ovaries. However, corpora lutea regressed normally in all ovaries left in their normal relationship to a uterine horn. These results indicate that the uterine regulatory factor does reach the ovary by some local route.
Transformation of rat small lymphocytes with allogeneic lymphoid cells
Authors: Schwarz M. Roy 
Published: February 2005

AbstractBlastogenesis was observed in cultures containing lymphoid cells of the thymus glands, spleens, lymph nodes, thoracic duct lymph and blood of two genetically dissimilar rat strains. In thymus cultures, the large and medium cells in the culture inoculum gave rise by division to small lymphocytes. The majority of the blast cells originated from the small lymphocytes of both donors, although not all small cells underwent transformation. Subsequently, some blasts divided, giving rise to more blast cells, while others served as precursors of small lymphocytes, thereby completing the cycle of small lymphocyte → blast→ small lymphocyte. Similar blastogenesis was observed in mixed cultures containing newborn thymic cells but was not observed in mixed splenic cultures until the donors were three days of age.