bluuebunny/crossref_metadata_2025_split huggingface dataset:
An electron microscopic study of the entodermal cells of the yolk sac of the chick during incubation and after hatching
Authors: Lambson Roger O. 
Published: February 2005

AbstractNormal and Thorotrast‐injected chick yolk‐sac specimens were prepared for electron microscopy and examined at intervals from early in the incubation period through the twelfth day after hatching. At all stages of development studied, it appeared that electron‐dense yolk granules, lipid droplets, and Thorotrast particles were phagocytosed by the entodermal lining cells through a complicated system of coated vesicles and apical canaliculi which were associated with larger vesicles situated more deeply in the cells. The numerous vesicles in these cells frequently appeared to have merged with one another, and absorbed yolk materials within many of them appeared to have become structurally altered.In the late‐incubation and post‐hatching periods, numerous lightly osmicated lipid spherules (50–150 mμ diameter) were seen within cisternae of rough‐surfaced endoplasmic reticulum, in vesicles of the Golgi apparatus, and in membranous enclosures near the basal plasmalemma of the entodermal cells. These lipid spherules were also present within intercellular spaces and within endothelial cells of vitelline capillaries, suggesting a sequence of events in which spherules were released from entodermal cells into the extracellular space and then taken up by the vascular system for further transport.
The developing bronchial arteries in a fetus of the twelfth week
Authors: Boyden Edward A. 
Published: February 2005

AbstractIn the human fetus bronchial arteries appear, as such, between the ninth and twelfth week as highly variable arteriolar outgrowths from the aorta itself or from proximal portions of right (or left) posterior intercostal rami of the aorta. Thus, they constitute a secondary system implanted relatively late upon the peripheral coats of the bronchial tree and large pulmonary vessels. The process is thought to be an inductive one depending partly upon the approximation of parts during the descent of heart and lungs into the thorax and partly upon the advancing degree of maturity of the bronchial tree.In the fetus of the twelfth week, to be described below, there are three bronchial arteries to the left lung and at least one to the right. The lowest of these (the left aorticobronchial artery) can be traced along the superficial coasts of the left lower lobe bronchus to the level just preceding that in which cartilages are differentiating: for example, to the third of what will comprise, eventually, some 25 generations of branches of the posterior basal segmental bronchus. Beyond this shifting level of differentiation the segmental pulmonary arteries constitute the sole arterial supply to the bronchi and parenchyma of the lung. It is assumed from recent reports in the literature that the bronchial arterioles will have established continuity with pulmonary arteries and with the pulmouary parenchyma not later than the twenty‐sixth week of gestation.
Adrenergic nerve elements in the hypogatric ganglion of the guinea pig
Authors: Watanabe Hiroshi 
Published: February 2005

AbstractAdrenergic nerve elements in the hypogastric ganglion of the guinea pig were studied by fluorescence and electron microscopy. The ganglion contains two main elements exhibiting green to green‐yellow fluorescence for catecholamines. One consists of basket‐like, simple nerve endings around some of the ganglion cell bodies, and the other of small polyhedral cells with short axonic processes. Electron microscopy revealed the ultrastructure of these elements. The adrenergic nerve endings contain small granular vesicles, about 500 Å in diameter, as well as a few large granular and small agranular vesicles. They were more rare than the cholinergic endings, which contain numerous small agranular vesicles mixed with a few large granular vesicles. Both adrenergic and cholinergic endings submerge to a considerable depth into the cytoplasm of ganglion cells. The ganglion cells send spinous processes into these endings. The fluorescent polyhedral cells are probably in an intermediate position between adrenal medullary cells and ganglion cells. They contain numerous large granular vesicles. Their axonic processes extend for a short distance to end in close topographical relation to capillaries. According to the structure of the granulated vesicles, these cells were classified into four types. The function of the adrenergic elements in ganglionic transmission was discussed.
The effect of hydrocortisone on extracellular connective tissue fibrils in the early chick embryo
Authors: Carlson Edward C. , Low Frank N. 
Published: February 2005

AbstractTwo series of chick embryos were treated with hydrocortisone in an attempt to demonstrate the influence of this hormone upon microfibrils found free in the tissue space surrounding the notochord. Embryos in series I were explanted on agar‐albumen medium and permitted to survive 1–24 hours after Ringer's solution or hydrocortisone had been pipetted onto the area vasculosa. Doses of hydrocortisone ranged from 5 μg to 1 mg. Series II embryos were similarly treatedin ovothrough a small shell “window” and then incubated 12 or 24 hours. All embryos were sacrificed at 72 hours incubation age. Ringer‐treated embryos in both series exhibited a rich tangle of early extracellular connective tissue fibrils (microfibrils) surrounding the notochord. One hour after treatment with hydrocortisone, embryos in series I showed a reduction in perinotochordal microfibrils. At four hours the effect was maximal and by 12 hours, recovery had been initiated, the morphology of which suggested a re‐organization of amorphous material and extracellular debris to form fibrillar structures. Twenty‐four hours after treatment, recovery was complete and hydrocortisone‐treated embryos exhibited perinotochordal fibril populations that were indistinguishable from Ringer‐treated specimens. The results of the series II experiments roughly parallelled those seen in series I but were somewhat less predictable.Possible modes of action of hydrocortisone on connective tissues and their relationship to the present study are discussed. It is suggested that the steroid may induce the release of a substance with an enzymatic activity capable of digesting microfibrils. This catabolic activity may be reflected as an inhibition of connective tissue production if it is assumed that microfibrils are precursors of larger, more mature fibrils. It is further suggested that since microfibrils are thought to contain connective tissue proteins, the initiation of microfibrillar reduction by hydrocortisone could indicate that this hormone may act in a similar manner on more mature connective tissue fibrils.
Renewal of the epithelium in the descending colon of the mouse. II. Renewal of argentaffin cells
Authors: Chang W. W. L. , Leblond C. P. 
Published: February 2005

AbstractArgentaffin cells (defined as containing groups of fine, iron hematoxylin stained granules) were examined in the epithelium of the descending colon of the mouse at various times after the initiation of a continuous infusion of 3H‐thymidine, using radioautography of semithin Epon embedded sections.These argentaffin cells do not show mitosis nor do they take up label one hour after injection of 3H‐thymidine. Therefore, they do not have the capacity to divide. Nevertheless. by two days and later after the beginning of continuous infusion of 3H‐thymidine, labeled argentaffin cells are present. It is, therefore, concluded that argentaffin cells arise from unidentified precursor cells containing no iron hematoxylin stained granules (or too few for identification with the light microscope).The number of labeled argentaffin cells increases during the first few days after continuous infusion of 3H‐thymidine, while they migrate upward along the crypt wall, somewhat more slowly than vacuolated‐columnar and mucous cells do. The results demonstrate that at least some of the argentaffin cells undergo migration and renewal in the colonic epithelium.
Fine structure of the taste bud in the mud puppy, Necturus maculosus
Authors: Farbman Albert I. , Yonkers Jenny D. 
Published: February 2005

AbstractThe taste receptor of Necturus was studied because of its potential usefulness in electrophysiological intracellular recording. The taste bud has about twice the length and twice the diameter of buds in most other vertebrates. The large size can be attributed to both a greater number of cells and a greater size of the individual cells. The cells of Necturus taste buds appear to be homologous to those in other vertebrates. Three distinct cell types were found: dark cells (60%), light cells (30%), and basal cells (10%). Dark cells contained granular endoplasmic reticulum, Golgi bodies, and many clusters of characteristic granules that reacted positively when treated with the periodic acid‐silver methenamine technique. They are probably secretory cells. Light cells, found in the center of the taste bud, were virtually filled with agranular endoplasmic reticulum, mitochondria and Golgi bodies. Their morphology is similar to that of chloride cells in fish gills, and they may have an ion transport function important in the gustatory response. Basal cells, located at the periphery in the basal half of the bud, contained characteristic dense‐core vesicles about 70–90 mμ in diameter. The lower half of the taste bud contained many intraepithelial nerve processes adjacent to the cells.
Effects of red blood cell injections on diet‐induced atrial thrombosis in Swiss mice
Authors: Ashburn Allen D. , Weaver Macon M. , Summers Patricia A. 
Published: February 2005

AbstractFemale Taconic Swiss mice were fed a high‐fat (28%), low‐protein (8%), hypolipotropic diet. Some of the animals received intraperitoneal injections of washed, packed red blood cells or physiological saline while receiveing the diet. Mice that received only the experimental diet for ten weeks developed a high incidence of atrial thrombosis (84%) concurrently with severe anemia (hematocrit 6.7). Saline injections did not alter these changes significantly. Atrial thrombosis was prevented in mice maintained at a normal or slightly subnormal hematocrit level with injections of washed, packed erythrocytes.
The fine structure of the pia mater of the rat
Authors: Morse Dennis E. , Low Frank N. 
Published: February 2005

AbstractTissue from the central nervous system of 11 adult Sprague‐Dawley rats fixed by vascular perfusion with buffered aldehydes was used in a study of the fine structure of the pia mater. Surface tissue from the cerebral and cerebellar cortices, ventral pons, olfactory bulb, tuber cinereum, spinal cord, superior colliculus, optic chiasm, and median longitudinal fissure was examined. Variations in pial composition occurred within each of these selected areas although a basic pattern prevailed throughout.The components of the pia mater are described under three categories: pial cells, extracellular elements, and macrophages. The pial cells are the more numerous cell type, possessing long, flattened cytoplasmic processes which contain few inclusions. These cells vary in thickness in any one area and there may be from one to six distinct cytoplasmic layers. Fenestrations between pial cell processes or total absence of pial cells are occasionally encountered. Unit collagen fibrils make up most of the extracellular material of the pia. These have a major period of about 550 Å and are about 400 Å wide. Macrophages are rounded up and contain various cytoplasmic inclusions. In normal animals evidence of active phagocytosis is rare.
Influence of starvation and refeeding on mucosal size and epithelial renewal in the rat small intestine
Authors: Altmann Gabriel G. 
Published: February 2005

AbstractAdult male rats were fasted for 0 (controls), three, five and seven days; a group was refed for one day after six days of starvation. Histological samples were taken from five regions along the length of the small intestine. The sizes of the villi, crypts and mitotic pool were estimated by measuring the number of epithelial cells per villus and crypt section and the number of mitotic figures per crypt section. Additional studies were carried out using colchicine for estimating mitotic time and methotrexate for inhibiting mitosis.All three parameters decreased progressively during starvation; the decrease in villus size was most pronounced in the duodenum and gradually less distalward. Refeeding increased the mitotic pool in every region; crypt size did not increase and villus size increased slightly in duodenum and jejunum only. When refeeding was combined with mitotic inhibition, the cell population of the crypts became depleted by 30–40% without change in villus size; thus, renewal appeared to continue by crypt cells migrating to the villi.Mitosis in the crypts is used for epithelial renewal in the adult intestine. The calculated turnover time of the epithelium was longer than normal and similar in every stage of starvation. Refeeding appeared to stimulate renewal. Since villus size changed somewhat independently from mitotic activity, the involvement of a separate mechanism controlling villus size was indicated.
Retinal damage after prolonged exposure to visible light. A light and electron microscopic study
Authors: O'Steen W. Keith , Shear Charles R. , Anderson Kenneth V. 
Published: February 2005

AbstractAlbino rats were exposed to fluorescent illumination for four to six months at an intensity which would not cause photocoagulation of the retina. Electron and light microscopic studies indicated that the retinas of these animals were irreversibly damaged and that the degeneration was specifically localized to the photoreceptor cells. Photoreceptors were not found in any of these retinas. Prolonged exposure to low intensity, visible light had no apparent effect on the bipolar neurons and ganglion cells or on their interconnections in the inner plexiform layer. Pigment epithelial cells survived the exposure and were unchanged except for extreme compaction of the apical villous processes in the retinal zone where the photoreceptors were located prior to their destruction. In some degenerated retinas the bipolar neurons were displaced along blood vessels extending from the inner ganglion cell layer to the outer retinal layers. Some of these blood vessels apparently formed anastomoses between the central retinal circulation and the choriocapillaries. The outer Müller cell processes, which contained numerous lamellated and tubular structures, expanded to cover the area adjacent to the pigment epithelium and to form an outer limiting membrane, which was displaced in position in comparison with a normal retina.
Electron microscopy of the red pulp of human spleen
Authors: Chen Li‐Tsun , Weiss Leon 
Published: February 2005

AbstractTerminating arterial vessels, the structure of sinuses and cords, and the passage of cells through the sinus wall in the red pulp of human spleen were studied. All terminating arterial capillaries arterial capillaries observed opened into cords. The distance between terminating arterial capillaries and sinuses varied. Macrophages were commonly present at arterial terminations. Arterial capillary endothelium contained filaments about 80 Å in diameter. Blood cells were frequently present in the capillary lumen or in passage through the capillary wall into cords. Endothelial cells of sinuses contained three distinctive structures: loosely organized cytoplasmic filaments, tightly organized finer filaments, and micropinocytotic vesicles. Many micropinocytotic vesicles about 0.1 μ in diameter were present just beneath the plasma membrane of the lateral and luminal sides of sinus endothelial cells and a few at the basal aspect. Loosely organized filaments about 80 Å in diameter ran parallel to the longitudinal axis of the sinus endothelium. The finer filaments about 30–50 Å in diameter were tightly organized as filamentous bands and present basally. The filaments of the bands appeared inserted upon the plasma membrane. They were also present in the cordal reticular cells and terminating arterial capillaries. Free cells were frequently present in passage through the slits of the sinus wall. There were no preformed or fixed apertures in the sinus wall. The basement membrane and reticular fibers were completely covered by the endothelial cells and/or cordal reticular cells.It is likely that those slits between endothelial cells in the sinus wall not covered by the basement membrane are potential passageways for cells moving from the cords into the sinus. The larger cytoplasmic filaments are likely contractile. The filamentous bands appear to maintain cell shape, stabilize the wall in relation to the basement membrane, and are probably operative in the control of cellular passage through the slits of sinus wall.
Longevity of male and female, intact and gonadectomized, untrected and hormone‐treated, neoplastic and non‐neoplastic syrian hamsters
Authors: Kirkman Hadley , Yau P. K. S. 
Published: February 2005

AbstractTwo thousand four hundred and fifty‐six male and 1432 female Syrian hamsters, dying spontaneously at different ages, are arranged in age at death increments of 100 days. These are arranged further into groups of intact male, female, orchiectomized and ovariectomized animals; animals with and without benign or malignant tumors; animals treated with androgen, estrogen or both; animals with or without various hormonal imbalances; solitary and grouped animals; and virgins and breeders. The age at death incidences of each sex are plotted in graphs. Although longevity is decreased by gonadectomy and by neoplasia, the same sex differential is evident in each group, with males showing a distinct and consistent tendency to outlive females. Results are expressed in absolute numbers and in percentages. The data provide strong evidence supporting the frequently published suggestion that the Syrian hamster may be remarkable among mammals in that males tend to outlive females.
Ultrastructural studies of transmural migration of blood cells in the bone marrow of rats, mice and guinea pigs
Authors: Campbell Ferrell R. 
Published: February 2005

AbstractThe ultrastructure of bone marrow of rats, mice and guinea pigs was studied after fixation by vascular perfusion. Serial sections were examined to determine the structure and site of pores in lining cells. It was concluded that pores are transient structures occurring only in conjunction with migrating blood cells. These pores occur within lining cells and most frequently near junctions of contiguous lining cells. Microfilaments in lining and adventitial cells are described and their possible roles discussed.
In vitro studies on ciliary activity within the oviducts of the rabbit and pig
Authors: Gaddum‐Rosse P. , Blandau R. J. 
Published: February 2005

AbstractDirect observations of ciliary activity on the mucosal surface of mammalian oviducts have rarely been reported. Yet such studies might help to determine the relative value of ciliary action in gamete transport through the ducts. The purpose of this study was to examine the direction and rapidity of ciliary currents in the oviducts of two mammalian species, the rabbit and the pig. Fresh oviducts were slit open longitudinally and submerged in Hanks' balanced salt solution at 37°C. The movements of particulate matter, such as stained lycopodium spores and 15 μ microspherents, placed on the mucosal surface, were observed and recorded on film. In both species ciliary currents in the ampulla swept the particles toward the ampullar‐isthmic junction. In the isthmus of the pig oviduct the particulate matter was transported in the reverse direction, toward the ovary. The pro‐ovarian current could be demonstrated throughout the isthmus, beginning a few millimeters above the uterotubal junction. In the rabbit a similar current was detected, but it was not as extensive as in the pig. In the upper isthmus of the rabbit oviduct, particulate matter and rabbit eggs in the “mucin coat” merely rotated or “tumbled” on the surface with little movement in either direction. This is the first report of pro‐ovarian ciliary currents for any mammal, and we believe these to be important for sperm transport through the isthmus. The action of cilia during egg transport is discussed.
Duration of the cycle of the seminiferous epithelium and the spermatogonial renewal in the monkey Macaca arctoides
Authors: Clermont Yves , Antar Michael 
Published: February 2005

AbstractMonkeys were sacrificed at three hours and at 12 days‐3 hours after an intraperitoneal injection with 3H‐thymidine. Radioautographs were prepared of periodic acid‐Schiff‐hematoxylin‐stained sections of the testes. At three hours, the most evolved labeled germ cells were leptotene spermatocytes in stage VIII of the cycle; at 12 days‐three hours the most evolved labeled cells were pachytene spermatocytes in stage IX of the succeeding cycle. Thus, over a 12‐day interval, the most evolved labeled spermatocytes had advanced through slightly more than one complete cycle. A quantitative analysis of tubular cross sections containing labeled spermatocytes permitted the calculation of the duration of one cycle of the seminiferous epithelium which turned out to be 11.6 days. The whole process of spermatogenesis which begins with the first spermatogonial mitoses taking place in stage VIII and terminates with the release of spermatozoa taking place in stage VI of the cycle, extends over the duration of 3.8 consecutive cycles and therefore requires approximately 44 days.On the same histological material counts of resting and dividing spermatogonia were performed at various stages of the cycle to determine their mode of proliferation and renewal. Six mitotic peaks were disclosed and were located in stages VIII, X, XII, II, IV and VI of the cycle. Cell counts and labeling indices indicated that the pale type A spermatogonia were the cells dividing during the first two of these six peaks of mitoses while the type B spermatogonia divided during the remaining four peaks of mitoses. The dark type A spermatogonia were not seen to divide during the cycle and may be considered as “reserve stem cells.” Cell counts and cell ratios indicated further that the pale type A spermatogonia divided in stage VIII of the cycle (and some in stage IX) to yield about twice their number of pale type A spermatogonia: of several possible schemes the authors believe that half of these entered a long interphase and became stem cells for the spermatogonia to be formed during the next cycle; these may be referred to as “renewing stem cells”; we consider that the other half of the pale type A spermatogonia arising from stage VIII peak of mitoses divided in stage X to produce type B spermatogonia. The latter cells then could enter the series of four consecutive mitoses during which they doubled their number each time to yield a generation of primary spermatocytes.