bluuebunny/crossref_metadata_2025 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

The 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

Changes 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

The 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

Sixty‐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

The 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

Trigeminal 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

A 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

By 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

Lipid 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

The 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

The 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

The 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

The 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

In 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

Blastogenesis 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.
Ultrastructural features of the shark brain
Authors: Long Don M. , Bodenheimer Thomas S. , Hartmann J. Francis , Klatzo Igor
Published: February 2005

The ultrastructural characteristics of elasmobranch central nervous system have not been previously reported. This study presents a general assessment of aldehyde perfused brain and spinal cord in three species of shark: tiger, hammerhead and Atlantic nurse. The same distinct cell types are present in the shark that exist in mammals and similar criteria may be used for their differentiation. Neurons have frequently round nuclei with a prominent nucleoli; cytoplasm is abundant and filled with formed elements; somatic synapses and subsurface cisterns are rare. Astrocytes are smaller, and have less cytoplasm and slightly fewer organelles. Glial fibrils occur, but are not invariably present. Separating astrocytes from neurons is the most difficult identification problem. Oligodendrogliocytes are smaller, and have denser cytoplasm and a dark nucleus. The striking feature of capillary morphology is the presence of an appreciable perivascular space containing collagen; many tortuous evanginations of this space occur into surrounding glial processes which completely invest the capillaries. Astrocyte cell bodies frequently lie immediately next to vessels, and capillaries are occasionally totally surrounded by a single astrocyte process, thus being endocellular. Smaller pericapillary processes may be either astrocytic or ependymal. Dendrites, synapses, axons, and myelin have no obvious special characteristics. Sodium, visualized by precipitation techniques, is prominent in the astroglia and neurons.
Subcommissural organ and adjacent ependyma: Autoradiographic study of their origin in the mouse brain
Authors: Rakic Pasko , Sidman Richard L.
Published: February 2005

Morphogenesis and time and place of cell origin of the subcommissural organ and adjacent ependyma in the mouse brain was investigated by light microscopy and autoradiography. Pregnant mice were injected systematically at different stages of gestation and their offspring killed after various periods. Cells of the subcommissural organ arise (undergo final replication of nuclear DNA) from embryonic days 11 to 15 at the diencephalomesencephalic junction in close association with the primordial fibers of the posterior commissure. The ependymal cells of the caudal part of the third ventricle first arise at approximately the same embryonic stage as the subcommissural cells and continue to proliferate through embryonic day 18.

The subcommissural organ is suitable for semiquantitative analysis because its cells are of one type, their number is small, they arise over a short time span and once formed, they persist indefinitely. Some cells exposed to thymidine‐H3 in utero at the time of final DNA replication were strongly labeled at adulthood, as expected, but others were weakly labeled. Calculations suggested that significant numbers of these weakly labeled cells should be assigned to the nondividing class i.e., had their birthdays on the day of thymidine‐H3 injection. Errors are introduced if the usual practice is followed of assigning birthdays on the basis of the heavily labeled population exclusively.
The fine structure of the adrenal cortex of the 13‐lined ground squirrel
Authors: Seliger William G. , Smith Wayne F.
Published: February 2005

The adrenal cortex of the 13‐lined ground squirrel was examined by means of phase contrast and electron microscopy. At the most, two cell types were observed. One of these two types was observed in three morphologically different stages of activity. They had some common characteristics, although they were very different in general appearance. The findings substantiate Symington's (′60, ′61) statements that the zona reticularis contains the active cells and the zona fasciculata contains the inactive cells of the deep adrenal cortex. The cell types do not stay within the bounds of the three classical zones, and it is suggested these be used for general topography only. A number of modifications and derivations of mitochondria are described, one of which lends strength to Lever's ('55) suggestion that mitochondria might be converted into lipoidal masses.
The innervation of the bone marrow in laboratory animals
Authors: Calvo Wenceslao
Published: February 2005

The nerve pattern of the bone marrow of the monkey, rabbit, rat and mouse was studied in serial sections specially stained to demonstrate myelinated and nonmyelinated nerve fibers. Features that are common to the different species studied were found in the bone marrow of the femur of the rat in a simple arrangement.

A scheme is proposed based on thirteen photomicrographs demonstrating the nerve pattern of the bone marrow and the relation of the nerve fibers with the arterial tree, the sinusoids and the blood forming cells. This scheme shows that the necessary anatomical conditions exist permitting a direct influence of the nervous system on the function of the bone marrow. These conditions are the presence of myelinated nerve fibers traversing the parenchyma of the marrow, and the existence of nonmyelinated fibers ending in sphincterlike structures at the origin of the arterioles.

Single myelinated nerve fibers and small bundles of both myelinated and nonmyelinated fibers lie in close contact with the endothelial wall of the sinuses during long trajects. Only the very thin endothelium of the sinuses separates the newly formed blood and the nerve fibers. An interaction between both elements is possible along these areas of contact.
The fine structure of uterine smooth muscle of the rat uterus at various time intervals following a single injection of estrogen
Authors: Bo Walter J. , Odor D. Louise , Rothrock Martha
Published: February 2005

The fine structure of smooth muscle cells of the rat uterus was studied at 6, 12, 24, 48, 72 and 96 hours after a single subcutaneous injection of estradiol dipropionate (10 μg). The control rats were ovariectomized, but did not receive hormone treatment. Changes in the ultrastructure of the muscle cells occurred soon after estrogen stimulation. An increase in the number of ribosomes on the outer nuclear membrane and evagination of the membrane into the surrounding cytoplasm was noted at six hours. The amount and dilatation of the granular endoplasmic reticulum (GER) increased gradually from 6 to 96 hours. At 24 and 48 hours the mitochondria appeared to increase in number and at later time intervals they increased in size. The Golgi complex was more prominent at 72 and 96 hours than at the earlier time intervals. An increase in free ribosomes was observed at 6 and 12 hours, but a marked accumulation of them occurred at 24 hours and continued to 96 hours. The glycogen granules were very pronounced at 24 and 48 hours with a reduction at 72 and 96 hours. Many pinocytotic vesicles and dense bodies were present in the controls and at 6 and 12 hours. A decrease in number occurred in both at the later time intervals. Organelles accumulated at the nuclear poles beginning at 24 hours and extending to 96 hours. The observations made provide additional information on the fine structure of uterine smooth muscle cells following estrogen stimulation and support previous biochemical studies on glycogen concentration and RNA synthesis in the rat uterus.
The fetal membranes of Pedetes capensis, and their taxonomic significance
Authors: Fischer Theodore V. , Mossman H. W.
Published: February 2005

Implantation in Pedetes capensis is superficial and antimesometrial with the embryonic disc mesometrially oriented. As the blastocyst expands, the embryonic pole trophoblast proliferates and penetrates the epithelium at the mesometrial side to establish a massive trophospongial preplacenta. Maternal blood lacunae form in this, and a preplacental maternal circulation is soon established. Amniogenesis is by folding. A choriovitelline placenta develops on the preplacental surface. Yolk sac inversion is late. The bilaminar omphalopleure is permanent. Syntrophoblastic tongues penetrate the preplacenta and surround maternal spaces lined with an attenuated trophospongial cell layer, thus providing a hemodichorial barrier when the vascular allantoic mesoderm invades these tongues to form the lobular labyrinth. A typical countercurrent bloodflow occurs. A small allantoic diverticulum persists to term. Several fetal membrane characters, known to be evolutionarily “conservative,” are alike in Pedetes and the more primitive sciuromorphs. These are the type of implantation, amniogenesis, yolk sac inversion, and allantois. The massive trophospongial preplacenta (Träger) suggests affinity with the Myomorpha and Hystricomorpha, but this is a highly variable character within the Rodentia. Therefore, it is concluded that on the basis of the fetal membranes the Pedetidae are somewhat specialized sciuromorphs.
Observations on calvarial growth in rachitic and healing rats
Authors: De Angelis Vincent
Published: February 2005

The histology of the rachitic and healing sutures, ectocranial and endocranial surfaces of the rat calvarium is described in this paper. Osteoid margins were evident on all surfaces observed at seven days in rachitic rats and were seen to increase in equal amounts on either side of the sutures as the disease process continues, while the osteoid accretion on the ectocranial and endocranial surface revealed differential growth rates throughout the experimental period. The pattern of osteoid deposition is suggestive of a process of calvarial reshaping from the younger animals to the older ones. The marrow spaces were gradually occluded by the osteoid deposition on their margins.

On induction of healing by vitamin D, the osteoid was calcified and then differentially resorbed by osteoclasis. The first osteoclasts were seen at the anterior lambdoidal suture two days after vitamin D administration. At the end of four days of healing, osteoclasts were evident at the coronal, the anterior lambdoidal and the posterior lambdoidal sutures as well as the endosteal sides of the ectocranial and endocranial surfaces. There were no osteoclasts in contact with uncalcified osteoid throughout the entire experimental period. Only the osteoid assumed to be overgrowth was resorbed, while osteoid in some areas was calcified and then retained. At the end of a ten day healing period, the calvarium of the experimental animal was virtually identical to that of the control animal, with the exception of some localized osteoclasis continuing.

A rachitogenic diet supporting excellent health and growth in the albino rat is described in this paper.
A histochemical study of muscle spindles and their relationship to extrafusal fiber types in the rat
Authors: Yellin Herbert
Published: February 2005

Hindlimb muscles of the rat were studied in serial section with enzyme histochemical methods. Muscle fibers, both extrafusal and intrafusal, were compared as to their relative succinic dehydrogenase and phosphorylase activity, indicative of oxidative and glycolytic metabolism respectively. The superficial fascicles of a number of white (fast‐twitch) muscles are composed almost exclusively of glycolytic (type A) muscle fibers, whereas the deep fascicles contain a mixture of oxidative (type B) and oxidative‐glycolytic (type C) fibers. Muscle spindles are found only among the deep fascicles of these fast muscles. Neither the soleus, a red (slow‐twitch) muscle comprised mainly of type B fibers, nor the middle lumbrical muscles, with a fairly uniform distribution of several fiber types, exhibit so specific a spindle disposition. Thus a close spatial relationship exists between spindles and certain types of muscle fibers, presumbly representing specific types of motor units. Within the spindles, the nuclear‐bag intrafusal fibers are generally of types A and B, and of a third variety characterized by both low oxidative and low glycolytic activity. The latter fiber‐type is not commonly observed in the extrafusal musculature. Nuclear‐chain intrafusal fibers resemble type C fibers. Speed of contraction and enzymes of energy metabolism of extrafusal fibers are known to be neurally regulated. The several types of histochemically distinguishable intrafusal fibers probably reflect differences in motor innervation and possibly differing contraction‐kinetics.
Skeletal development of mice x‐irradiated in utero
Authors: Rugh R. , Duhamel L. , Osborne A. W. , Sweeney W. A.
Published: February 2005

CF1 mice were exposed to x‐rays during development at various intervals from 0.5 day after conception to 18 days. The levels of x‐irradiation were previously established for each gestation day so that half of the exposed fetuses would survive for at least 30 days after birth. Those that survived to two months were radiographed (1,174 mice including 150 controls of the two sexes) and seven bone measurements were taken from each mouse. From conception through gestation day 10 there appeared to be no significant reduction in bone measurements as a result of embryonic or fetal x‐irradiation even though the exposures ranged from 100 R to 400 R. The greatest decrements followed exposure of the fetuses at days 15 and 16, although there was some reduction on days 13 and 14 also. The spine measurements were first reduced when x‐irradiation was done on day 11. In both the controls and those x‐rayed the average bone measurements were slightly greater for the males than for the females. Embryologically those days most radiosensitive with respect to skeletal growth were those when osteogenesis was the most active. There is no evidence that ionizing radiations prior to chondrogenesis has any effect on later skeletal development.
A cytological study of intestinal absorption in the suckling rat
Authors: Cornell Richard , Padykula Helen A.
Published: February 2005

The distal small intestine of the albino rat has the capacity to absorb protein and particulate matter during the suckling period. Ultrastructural and cytochemical aspects of this absorptive phenomenon were examined in the ileum. Soon after the initial ingestion of milk, a large, yellow, smooth membrane‐limited, protein body appears in the immediate supranuclear region of ileal absorptive cells and, also, many small vacuoles and membrane‐limited droplets arise between this body and the microvilli. Exogenous protein enters an elaborate superficial tubular system and is segregated in membrane‐limited vacuoles and droplets and, then, appears in the supranuclear body. The body and adjacent membrane‐limited droplets are basophilic, periodic acid‐Schiff positive, and rich in hydrolytic enzymes (acid phosphatase, ATPase, thiamine pyrophosphatase, alkaline phosphatase, esterase). The results suggest the presence of a highly developed lysosomal system during the period of protein absorption. Additional cytological features of the absorptive cells are presented.

Ileal absorptive cells are normally free of lipid droplets. When emulsified lipid is introduced into the neonatal ileum, it enters into the cytoplasmic smooth membrane system, including the supranuclear body, and later appeas in the lacteals. This suggests both that the uptake of material may be non‐selective and that similar intracellular pathways may be used in transporting protein and lipid through the epithelium.
Position and orientation of the heart valves
Authors: Merklin Robert J.
Published: February 2005

The position and orientation of the heart valves and cusps were investigated in 125 adult and 25 stillborn cadaver hearts in an attempt to establish a reasonably uniform picture of this aspect of cardiac anatomy. The study was prompted by the fact that current textbook figures show wide variation in depicting these structures and also by the fact that the standard nomenclature of the cusps has not been fully accepted by anatomists and cardiologists. There is the additional problem of naming the cusps in congenitally defective hearts. The literature related to cases of great vessel transposition is particularly confusing and the lack of a uniform figure of the heart valves and disagreement about the cusps adds to the confusion.

The arrangement of the valves and cusps was found to be very uniform in the specimens studied and a standard figure is suggested to replace the variations seen in current texts. It is further suggested that the approved nomenclature of the cusps be followed and several supplemental terms be recognized as accurate. non‐ambiguous and useful, particularly in descriptions of the congenitally defective heart.
On the development of bone marrow innervation in new‐born rats as studied with silver impregnation and electron microscopy,
Authors: Calvo Wenceslao , Forteza‐Vila Jerónimo
Published: February 2005

This study of innervation of the bone marrow in new‐born rats demonstrates that major signs of differentiation occur in the nerves at the end of the second week after birth. Myelinated nerve fibers begin to acquire their myelin sheath at this time. The Schwann cells show abundant ergastoplasmic reticulum. Some of these cells separate individual axons and wrap them up with the double membranes that form the myelin sheath. From then on, the nerves of the marrow contain both myelinated and nonmyelinated fibers. Fibroblasts also differentiate during this time, producing collagen fibers around the nerves. Some fibroblasts are interconnected by desmosome‐like structures. Fibroblasts and collagen fibers form the connective tissue sheaths of the nerve (perineurium and endoneurium). Upon completion of the myelin sheath by the Schwann cells and the connective tissue sheath by the fibroblasts, nerves of the marrow acquire the morphological characteristics of the peripheral nerves of the adult animal. The fine structure of the axons in contact with the muscle fibers of the arterial wall correspond to Type 2‐a of Watari. These nerve fibers are considered to be of sympathetic type. The time of maturation of nerves in the bone marrow coincides with the beginning of responsiveness to stimulatory and inhibitory conditions demonstrated in this organ by other authors.
The ultrastructure of the stellate cell in the rabbit pars distalis,
Authors: Schechter Joel
Published: February 2005

Stellate cells in the rabbit pars distalis have been studied electron microscopically from birth to adulthood. During this period the stellate cells are found in abundance throughout the pars distalis and are the only consistently agranular cells observed in the pars distalis parenchyma. Identifying features of stellate cells are fine cytoplasmic filaments and farreaching cytoplasmic processes. The cytoplasmic processes ramify between adjacent parenchymal cells and are connected to other stellate cells by desmosomes. The stellate cells, linked to one another by desmosomes, thus constitute a meshwork within which the granulated parenchymal cells reside. Processes of stellate cells are also found interposed between the parenchymal basal lamina and the granulated parenchymal cells. The cytoplasmic filaments are distributed throughout the cytoplasm and extend into the fine processes. The filaments do not appear to have any particular orientation to the plasma membrane. Compared to granulated cell types, the cytoplasmic organization of stellate cells is not complex. Mitochondria, smooth and granular endoplasmic reticulum, Golgi membranes, ribosomes, dense bodies and lipid droplets are distributed throughout the cytoplasm, but not in great numbers. Nuclear chromatin is uniformly distributed. A nucleolus may or may not be evident.

The ultrastructural features of the stellate cells are in many respects unchanged from birth to adulthood. An exception is in one‐to‐two‐day‐old neonates when in some stellate cells the quantity of cytoplasmic filaments appears increased and there is hyperplasia of the endoplasmic reticulum and Golgi membranes. A similar hyperplasia of these stellate cell organelles can be produced experimentally in adult rabbits by administration of Metopirone.

Though the morphological evidence supports a structural or metabolically supportive function for the stellate cell, an additional role as the possible source of adrenocorticotrophic hormone is also discussed.
Renewal of Paneth cells in the small intestine of the mouse
Authors: Cheng Hazel , Merzel J. , Leblond C. P.
Published: February 2005

The origin and fate of Paneth cells were examined in duodenum, jejunum and ileum of adult female mice, using radioautography after administration of 3H‐thymidine either in a single injection or in drinking water for four days or as a continuous infusion for up to ten days. The tissues were fixed by perfusion with 4% paraformaldehyde. One‐micron thick, Eponembedded single or serial sections were stained with Regaud's hematoxylin, radioautographed, and counterstained with safranin O.

Mitosis of Paneth cells is never observed, nor are these cells ever labeled one hour after 3H‐thymidine. Hence, Paneth cells do not divide.

However, a few days after single injection or prolonged administration of 3H‐thymidine, labeled Paneth cells appear. The first labeled cells have tiny granules but, as the cells age, larger and larger granules are observed.

Adjacent to Paneth cells are slender undifferentiated cells which show frequent mitoses and early labeling. The evidence points to some of these cells transforming into Paneth cells. Since occasionally Paneth cells degenerate, the newly‐formed ones would provide replacement for those which die, thus insuring the steady state of the Paneth cell population. The renewal of this population is characterized by a turnover time of about three weeks.
The opisthonephric kidney of the sea lamprey of the great lakes, Petromyzon marinus L. I. The renal corpuscle
Authors: Youson John H. , McMillan Donald B.
Published: February 2005

The renal corpuscle of the opisthonephric kidney of the Great Lakes lamprey, Petromyzon marinus L., is described. In the larvae (ammocoetes) several renal corpuscles, each consisting of lobed glomeruli and Bowman's capsules, are placed behind one another and there is a progressive lengthening of the posterior corpuscles as the animal ages, apparently by the addition of new glomeruli posteriorly. Bowman's capsule surrounds a single loop and consists of parietal and visceral layers which are similar to those seen in higher vertebrates.

The kidney of the adult has a single complex renal corpuscle which extends almost its entire length. Present evidence indicates that the adult kidney is formed during transformation and that the larval renal corpuscles do not contribute to the single elongate corpuscle of the adult. A large number of lobed glomeruli, lying one behind the other, form the elongate glomus. Interposed between each pair of lobes is the dilated end of a nephron. There are no typical Bowman's capsules in the adult although where these nephric capsules invest the blood vessels of a lobe they develop podocytes similar to those of the visceral layer of Bowman's capsule and elsewhere they consist of a simple squamous epithelium similar to that of the parietal layer.
Local action of intrahypophyseal implants of estrogen as revealed by staining with peroxidase‐labeled antibody
Authors: Gersten Brian E. , Baker Burton L.
Published: February 2005

The direct action of 17 β‐estradiol and cholesterol on cells of the pituitary pars distalis, as revealed by staining with peroxidase‐labeled antibody, was studied in female rats. Pellets of pure cholesterol and of estradiol mixed with cholesterol were implanted into the left lobe of the pars distalis 14–32 days after ovariectomy and left in place for 7–16 days. Rabbit antisera to rat prolactin, human growth hormone, human chorionic gonadotropin (for gonadotropes — presumably luteinizing hormone cells), and porcine corticotropin were used. In no case were cells altered in the contralateral lobe of the pars distalis; cholesterol likewise had no significant effect on the ipsilateral lobe. However, in the ipsilateral lobe containing an estrogen pellet, prolactin cells were hypertrophied and hyperplastic; cells assumed to be responsible for luteinizing hormone secretion were reduced in size and stained more intensely; and growth hormone cells were reduced in size. Corticotropin cells remained unaffected. For the most part estrogenic effects were distributed ventrally, caudally and laterally from the pellet and not far medially, never reaching the midline. It was concluded that estrogen acts directly on the hypophysis, the spread of the effects reflecting the direction of blood flow within the gland. These observations support the hypothesis that the pituitary gland serves as a site for feedback action by estrogen.