bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphometric studies on rat seminiferous tubules
Authors: Wing Tung‐Yang , Christensen A. Kent 
Published: February 2005

AbstractThe goal of this morphometric study was to obtain quantitative information on the seminiferous tubules of Sprague‐Dawley rats, including changes seen at various stages of the cycle of the seminiferous epithelium. Tissue from perfusion‐fixed testes was embedded in Epon‐Araldite; and sections were subjected to morphometric measurements at the light microscopic level, using point counting for volume densities and the Floderus equation for numerical densities.Changes occur in the diameter of the seminiferous tubule, as well as in the volume of the seminiferous epithelium and tubule lumen, from stage to stage during the cycle. A significant constriction of the seminiferous tubule accompanies spermiation. The volume of the seminiferous epithelium per unit length of the tubule begins to increase after stage XIV, and peaks at stage V of the next cycle. The tubule lumen increases dramatically from stages V to VII, at the expense of the epithelium.The number of Sertoli cells is constant per unit length of the seminiferous tubule at all stages of the cycle. This is also true for primary spermatocytes of various developmental phases and for round spermatids from step 1 through step 10 of spermiogenesis. The average number of younger (preleptotene, leptotene, zytgotene) primary spermatocytes per Sertoli cell is 2.34 ± 0.082 (SEM), the number of older (pachytene, diplotene) primary spermatocytes per Sertoli cell is 2.37 ± 0.064, and the ratio of step 1–10 spermatids to Sertoli cells is 7.89 ± 0.27. By studying tangential views of serially sectioned seminiferous tubules at stage V, it is shown that the number of step‐17 spermatids associated with each Sertoli cell averages 8.35 ± 0.128, although the counts ranged from 6 to 11. The only appreciable occurrence of cell death after the last spermatogonial mitosis appears to be a 15% loss during the first meiotic division. From our morphometric results, corrected for volume changes during preparation for microscopy, there are 15.7 million (± 0.99 million) Sertoli cells per gram of fresh rat testis. The length of seminiferous tubule per gram of testis is estimated to be 12.4 ± 0.56 meters, and the tubule surface area per gram testis is 119.7 ± 2.57 cm2. The daily production of mature spermatids is 9.61 million (± 0.615 million) per gram of testis.
Appearance and disappearance of tubular paracrystalline structures in somatotrophs and lactotrophs during the annual life cycle of the bat (Myotis lucifugus)
Authors: Nunez Eladio A. , Gershon Michael D. 
Published: February 2005

AbstractThe fine structure of the endocrine (granulated) cells of the adenohypophysis of the bat was examined at different periods of the annual life cycle. During the active homeothermic period (early spring until late summer) the endocrine cells were heavily granulated, and evidence of granule release was commonly seen. At this time, but not at other times (hibernation and arousal), prominent paracrystalline structures were numerous and transiently appeared in the cytoplasm of acidophils (apparently both lactotrophs and somatotrophs) but not in the cytoplasm of basophils. These paracrystalline bodies were composed of densely packed, parallel arrays of tubules. The paracrystalline structures in lactotrophs differed in size, shape, and the pattern of arrangement of component tubules from those of somatotrophs. During hibernation no evidence of exocytosis was seen, and secretory granules accumulated in the cytoplasm. Prior to arousal, secretory granules were removed by autophagy.
Kinetics of fibrous sheath formation in the rat spermatid
Authors: Irons Margaret J. , Clermont Yves 
Published: February 2005

AbstractThe morphogenesis of the fibrous sheath in the rat spermatid has been studied by electron microscopy and by EM radioautogaphy following injection of 3H‐proline. The appearance of the developing fibrous sheath from the distal to proximal end of the principal piece has been examined in spermatids in each of the 19 steps of spermiogenesis. The precise timing of the various steps of its formation has been established and related to radioautographic observations on the synthesis and incorporation of proteins into the developing fibrous sheath. The longitudinal columns form slowly over a period of 15 days, appearing first at the distal end of the principal piece in step 2 and gradually extending in a proximal direction, ending at the level of the annulus in step 17. Throughout this 15‐day period, proline‐containing proteins are synthesized and incorporated into the growing columns.All of the ribs, on the other hand, arise from anlagen which are assembled along the length of the principal piece during a much shorter (4.5‐day) period between steps 11 and 15 of spermiogenesis. New rib anlagen seemingly originate from bundles of proteinaceous filamentous material which are synthesized in the cytoplasm of step 11–15 spermatids and become aligned along the plasma membrane of the principal piece, starting at the distal end. These observations suggest that the two components of the fibrous sheath are assembled by means of two independent mechanisms that proceed asynchronously except during an overlap period of 2.5 days between steps 12 and 14.
Culture of A‐431 human epidermoid carcinoma cells in serum‐free medium: Effect of culture conditions on the binding of [125I]‐epidermal growth factor
Authors: Barka Tibor , Van Der Noen Hendrika 
Published: February 2005

AbstractSerum‐free culture conditions that permit the continuous growth of A‐431 human epidermoid carcinoma cells were developed. In Dulbecco's modified Eagle's synthetic nutritional medium (DME) supplemented with fetuin, insulin, transferrin, biotin, and oleic acid‐fatty acid‐free bovine serum albumin complex A‐431 cells grew at a rate comparable to that observed in the presence of calf or fetal calf serum. Of the factors tested, oleic acid had the most pronounced stimulatory effect on the growth and [3H]‐thymidine incorporation of A‐431 cells in serum‐free medium. A‐431 cells have a high number of receptors for epidermal growth factor (EGF); they bind and rapidly internalize EGF. Nevertheless, EGF did not stimulate either the growth or the [3H]‐thymidine incorporation of these cells. Analyses of [125I]‐EGF binding data indicated that A‐431 cells grown in the presence of calf serum had about 3.2–3.9 × 106 specific, saturable EGF receptor sites on their surface. Linear Scatchard plots indicated a single class of noninteracting receptors with an apparent equilibrium dissociation constant of about 2.8 × 10−9 M. The average number of receptors of A‐431 cells maintained in DME supplemented with only fetuin, insulin, and transferrin for several months was significantly less, 1.54 × 106, than that of A‐431 stock cells cultured in the same medium for 2 days only (2.68 × 106). The apparent dissociation constants for the same cell populations were, however, similar, 4.5 × 10−9 M and 4.1 × 10−9 M, respectively. Stimulation of growth by oleic acid resulted in about 20% decrease in the average number of receptor sites, with an increase in the apparent equilibrium dissociation constant.
The contribution of the mesonephros to the development of the sheep fetal testis
Authors: Zamboni Luciano , Upadhyay Shakti 
Published: February 2005

AbstractIn this study, which was performed on 52 sheep fetuses aged 24 to 85 days, we examined the relationship between testicular development and the “giant” mesonephric nephron, a peculiar structure consisting of a large glomerulus and multiple tubules. The development of the testis occurred in two phases. The preparatory phase began at day 24 of gestation, evolved simultaneously with the involution of the glomerulus of the giant nephron, and was characterized by mobilization of the glomerular cells and by their colonization of the genital ridge. By day 31, a prominent mass of migrating mesonephric cells had developed; it extended uninterrupted from the giant glomerulus into the gonad where the mesonephric cells associated with the germinal cells forming the cellular template from which the testicular cords later became assembled. At complete involution of the glomerulus (day 52), the migratory mass implanted on the tubules of the giant nephron, which thus became continuous with the gonad. During the organizational phase, which began at day 29 with the formation of the tunica albuginea, the various components of this continuum became progressively organized along a testis‐to‐mesonephros direction into seminiferous cords, tubuli recti, the cords of the rete testis, and the ductules efferentes. These observations show that, in the sheep, the precursors of the Sertoli cells are mesonephric in origin, and that the genital tract proximal to the epididymis differentiates from a single mesonephric nephron.
Vasculature of the mouse, rat, and rabbit testis‐epididymis
Authors: Chubb Curtis , Desjardins Claude 
Published: February 2005

AbstractThe arrangement of blood vessels serving the testis‐epididymis was investigated microscopically in the mouse, rat, and rabbit. Blood vessels were visualized by infusing liquid silicone rubber into the vessels and subsequently clearing the surrounding tissue. Comprehensive illustrations of the vasculature were prepared from three‐dimensional examinations.Arterial and venous vessels serving the testis‐epididymis follow similar routes in all three species. However, the arrangements and characteristics of the blood vessels demonstrate dramatic species differences. For example, arteries within the testes have tight coils in the mouse and artery‐artery anastomoses in the rat. Veins form vascular pathways that connect the testis and efferent ductules in all three species but also form a connection between the testis and cauda epididymidis in the rabbit only.Testosterone concentrations were determined in blood obtained by micropuncture of selected testis‐epididymal veins. The measurements establish that the highest levels of testosterone are found in testicular surface veins. Also, vas deferential veins of the rabbit had significant amounts of testosterone. Studies of the blood‐vessel volumes suggested that the volumes of arteries and veins in the testis are similar, whereas venous volumes exceed arterial volumes in all of the other organs examined.The studies provide comprehensive information about the architecture and physiology of blood vessels serving the testis‐epididymis in the mouse, rat, and rabbit. Each species exhibits diversity in the vasculature and testosterone content of the veins. Veins connecting the testis to the efferent ductules and cauda epididymidis may provide for the preferential delivery of testicular secretions to androgen‐dependent organs before the secretions are metabolized or diluted in the systemic blood.
Secretory cells of the oviduct of the pig‐tailed monkey, Macaca nemestrina, during the menstrual cycle and after estrogen treatment
Authors: Odor D. Louise , Gaddum‐Rosse Penelope , Rumery Ruth E. 
Published: February 2005

AbstractThe secretory cells of the oviductal epithelium in the pig‐tailed monkey, Macaca nemestrina, have been studied by light and electron microscopy. Changes during the menstrual cycle and after ovariectomy, with and without subsequent estrogen treatment, have been documented. During the early follicular phase the epithelium is recovering from deciliation and secretory cell atrophy that occur in the late luteal phase. A few fimbrial and a moderate number of ampullar and isthmic cells contain a few electron‐dense, homogeneous secretory granules in their apical cytoplasm. During the late preovulatory and early postovulatory periods, secretory cell structure varies considerably. Fimbrial cells typically display apical protrusions that contain no or a few small, mainly homogeneous, secretory granules. The cytoplasm is crowded with elements of the Golgi complex, with granular endoplasmic reticulum profiles often intimately associated with mitochondria, and with variable numbers of polysomes and glycogen granules. In ampullar and isthmic cells secretory granules are more abundant than in fimbrial cells, and electron‐lucent vacuoles appear. The granules are of two types: (1) those having an electron‐dense, homogeneous matrix, and (2) those possessing lamellar structures within moderately dense matrices. The lamellae of the second type course in parallel arrays separated by a distance of approximately 15.5 nm and exhibit a periodicity of approximately 11.3 nm. Possible transitional stages between the lamellar granules and the vacuoles containing lamellar fragments are observed. Secretion occurs by exocytosis. During the late luteal phase no fimbrial cells have secretory granules. In the ampulla many of the cells have poor development of the organelles involved in secretory activity and have few or no secretory granules. In others, a moderate number of secretory granules are present; in one animal, exocytosis is observed. In the untreated ovariectomized animal no secretory granules occur, and the organelle content is much less than in the cycling and the estrogen‐treated monkeys. In ovariectomized, estradiol‐treated monkeys, some areas of all three oviductal segments are well stimulated whereas others display little or no secretory activity.
Effect of ovariectomy on the hypothalamic content of immunoreactive gonadotropin‐releasing hormone in the female mouse as revealed by quantitative immunocytochemistry and radioimmunoassay
Authors: Briski Karen P. , Baker Burton L. , Christensen A. Kent 
Published: February 2005

AbstractOur radioimmunoassay data reveal that ovariectomy for either one or two months resulted in a significant decrease in the GnRH content of the mouse basal hypothalamus, while in mice ovariectomized for two weeks the GnRH levels did not differ significantly from controls. Parallel immunocytochemical analyses gave similar results. Tissue sections from specific regions of the median eminence in intact and ovariectomized mice were immunolabeled for GnRH with the peroxidase‐antiperoxidase procedure of Sternberger. Differences in area and average unit density of the reaction product were measured with a Quantiment 720 image analyzer. At two weeks after ovariectomy, a majority of matched sections from intact and ovariectomized animals, taken in each sampled region of the median eminence, showed no visually apparent difference in GnRH immunoreactivity. Quantitative image analysis of these preparations revealed no statistically significant difference in either the area of neural tissue covered by deposit or the average unit density of this material in any given region. In contrast, in mice ovariectomized for either one or two months, immunolabeled GnRH was decreased throughout the cephalo‐caudal extent of the median eminence. In each region, a reduction in reaction deposit was observed over most of the area in which GnRH is localized, especially in the medial aspects of this distribution. Image analysis of these preparations revealed a significant reduction of both specimen area immunolabeled for GnRH and the average unit density of reaction product in each region of the median eminence. While the decrease in density was uniform throughout the median eminence, the greatest reduction in area covered by deposit occurred in the infundibular region.The demonstration of a decrease in basal hypothalamic GnRH in the chronically ovariectomized mouse suggests that GnRH neurosecretion is increased in response to the absence of the ovaries and supports the premise that tonic secretion of this neurohormone, in the mouse, may be subject to regulation by the gonads. At two weeks after ovariectomy, it is possible that changes in GnRH secretion occur without a concomitant alteration in hypothalamic hormone content. In addition, the quantitative immunocytochemical data suggest that GnRH neurons responsive to ovariectomy terminate throughout the rostro‐caudal extent of the mouse median eminence, especially in the medial sites of localization. A proportionally greater number of these endings appear to be present within the infundibular region of the median eminence, relative to the other regions sampled.
Role of the vagus nerve and its recurrent laryngeal branch in the development of the human ductus arteriosus
Authors: Leonard Michael E. , Hutchins Grover M. , Moore G. William 
Published: February 2005

AbstractThe reason that the normal ductus arteriosus has a muscular media, contrasting with the elastic lamellar structure of the adjacent great arteries, is unknown. We examined the hypothesis that the anatomic relationship of the ductus arteriosus to the vagus and recurrent laryngeal nerves during early development might be of importance in influencing ductal morphology. Normal human embryos from the Carnegie Embryological Collection and embryos and fetuses from the Hopkins Pathology Collection were studied microscopically, by reconstructions made from serial histologic sections, or by gross dissection. At Carnegie stage 16 the recurrent laryngeal nerves pass medially from the vagus nerve to the laryngeal area and are caudal to the bilaterally symmetric sixth aortic arches. By stage 18 the right sixth aortic arch has disappeared and the left sixth aortic arch is in a more caudal position relative to the larynx. The left vagus nerve and its recurrent laryngeal branch form a sling supporting the distal (or ductus arteriosus component) of the left sixth aortic arch. In subsequent development there is greater relative separation of the larynx and ductus arteriosus. The media of the ductus arteriosus beneath the supporting nerves is thinner and has less elastic fiber formation than the elastic lamellar media of the adjacent aortic arches. The study shows that the vagus and recurrent laryngeal nerves are in a position to provide mechanical support to the ductus arteriosus during its development and that the morphology of the media of the supported ductus arteriosus differs from that of the adjacent unsupported aortic arches. It is suggested that this local mechanical support may be the reason that the normal ductus arteriosus differentiates as a muscular artery and is therefore able to obliterate its lumen in postnatal life. Without such support the ductal media could develop the abundant elastic fibers characteristic of the normal unsupported aorta and pulmonary trunk and become an abnormal, persistently patent ductus arteriosus.
The cytology of the dental follicle and adjacent alveolar bone during tooth eruption in the dog
Authors: Marks Sandy C. , Cahill Donald R. , Wise Gary E. 
Published: February 2005

AbstractPrevious studies from our laboratories have shown that premolar eruption in dogs depends upon the presence of the dental follicle and is independent of root or crown growth or attachment to the oral epithelium. The present study is an analysis of the cellular composition of the dental follicle and the cellular investment of the adjacent walls of the bony crypt before and during eruption of the third and fourth mandibular permanent premolars in young beagle dogs. Four premolar follicles and their adjacent bony crypts were examined at 2‐week intervals over 12 weeks before and during eruption of these teeth. Tissues were removed, fixed, processed, and oriented so that each follicle and the adjacent crypt wall could be reproducibly examined in vertical and horizontal planes. Mononuclear cells with abundant cytoplasm, euchromatic nuclei, and prominent nucleoli were present in juxtavascular location in the coronal part of the dental follicle; and these cells increased in number immediately preceding and during tooth eruption in parallel with an increase in osteoclasts on the adjacent crypt wall. These data are interpreted to mean that the coronal part of the dental follicle may coordinate the alveolar bone resorption required for tooth eruption by attracting and directing to the crypt wall a population of mononuclear cells, which either become osteoclasts and/or direct osteoclastic activity during tooth eruption.
Organogenesis of the pituitary, adrenal, and lung at birth in the wallaby, Macropus rufogriseus
Authors: Walker M. T. , Gemmell R. T. 
Published: February 2005

AbstractThe ultrastructure of the pituitary, the adrenal, and the lung was examined in the newborn wallaby, Macropus rufogriseus. Tissue from six wallaby neonates (less than 8 hr of age), two near‐term fetuses (26 days after removal of suckling pouch young [RPY]), and a two‐day‐old pouch young was examined; and tissue levels of cortisol in the adrenal glands of five neonates and a near‐term fetus (26 days) were measured by radioimmunoassay.At birth the adenohypophysis comprised the bulk of the pituitary gland. The pars distalis was well vascularized and many cells contained electron‐dense, membrane‐bound granules. The adrenal glands lacked specific zones but comprised two distinct populations of cells. The cytoplasm of one cell type contained electron‐dense, membrane‐bound granules, similar to those observed inside catecholamine‐secreting cells of the adrenal medulla; the other cell type possessed large amounts of smooth endoplasmic reticulum and mitochondria with tubulo‐vesicular cristae. These features are characteristic of cells which are actively synthesizing steroid hormones. The concentration of cortisol was 0.58 ng/adrenal in the wallaby at birth. The fetal lungs near term were at the glandular stage of development, and epithelial differentiation of type I and type II pneumocytes was imminent although attenuation was not evident. The canalicular neonatal lung did not contain true alveoli, but type II pneumocytes contained osmiophilic lamellar inclusions of surfactant.The fetal pituitary and adrenal are functional at birth and are thus capable of initiating parturition and of influencing lung maturation in the fetus.
Histochemical evaluation of mouse and rat kidneys with lectin‐horseradish peroxidase conjugates
Authors: Schulte B. A. , Spicer S. S. 
Published: February 2005

AbstractParaffin sections of mouse and rat kidney were stained with a battery of ten lectin‐horseradish peroxidase conjugates and lectin binding was correlated with the ultrastructural distribution of periodate‐reactive sugar residues as determined by the periodic acid‐thiocarbohydrazide‐silver proteinate technique. Various segments of the uriniferous tubule in both species showed differential affinity for labelled lectins. Significant differences were also evident between comparable tubular segments in mouse and rat kidneys. Neutral glycoconjugates containing terminal β‐galactose and terminal α‐N‐acetylgalactosamine were prevalent on the luminal surface of the proximal convoluted tubule in the rat, but α‐N‐acetylgalactosamine was absent in this site in the mouse. In both species, terminal N‐acetylglucosamine was abundant in the brush border of proximal straight tubules but absent in proximal convolutions. Fucose was demonstrated in both proximal and distal segments of mouse kidney tubules but only in the distal nephron and collecting ducts in the rat. Lectin staining revealed striking heterogeneity in the structure and distribution of cellular glycoconjugates. Such cellular heterogeneity was previously unrecognizable with earlier histochemical methods. The marked cellular heterogeneity observed with several lectin‐conjugates in distal convoluted tubules and collecting ducts of both species raises a prospect that lectins can provide specific markers for intercalated and principal cells in the mammalian kidney. Glycoconjugates containing terminal sialic acid and penultimate β‐galactose were present on vascular endothelium in both rodent kidneys, as were terminal α‐galactose residues; but both species lacked reactivity for Ulex europeus I lectin in contrast to human vascular endothelial cells. The constant binding pattern of lectin conjugates allows convenient and precise differentiation of renal tubular segments and should prove valuable in the study of changes in kidney morphology promoted by experimental manipulation or pathologic changes.