bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure of rat ultimobranchial bodies after birth
Authors: Calvert R. 
Published: February 2005

AbstractThe evolution of ultimobranchial bodies in Holtzman rats during the first 64 weeks after birth was studied by reconstructing three‐dimensional models from serial sections stained by the periodic acid‐Schiff technique. Radioautography with 125I was made to see if ultimobranchial cells and/or follicular cells lining the lumen of mixed follicles were able to iodinate proteins. The term ultimobranchial body designates herein an embryonic vesicular structure (derived from the third pharyngeal pouch) whose wall is made of a stratified squamous epithelium. During the first week after birth, the vesicular ultimobranchial body elongates rapidly and becomes a canal or a duct. During the second week, cell desquamation brings about local dilatations in the lumen of these ducts; with further enlargement ultimobranchial follicles will appear. In one‐day‐old rats, mixed follicles are present. Only the follicular component of mixed follicles iodinates proteins as is shown by radioautography. The reconstructed models enlarge rapidly up to the 56th day after birth at which time their weight has increased nineteenfold. These same models show that the three morphological components of ultimobranchial parenchyma, namely ducts, follicles and mixed follicles, are in continuity within the thyroid parenchyma. The formation of new thyroid follicles after birth and the possibility that the ultimobranchial parenchyma may function as an endocrine gland of holocrine type are discussed.
16α‐hydroxy‐progesterone as a sex hormone antagonist: Effect on venous diameters in the female mouse
Authors: Forbes Thomas R. , Taku Elaine 
Published: February 2005

AbstractPellets of progesterone plus 1 % 16α‐hydroxy‐progesterone (16α‐OH), testosterone plus 1 % 16α‐OH, and estradiol‐17β plus 1 % 16α‐OH were implanted in the right uterine fat mass in ovariectomized (O) and ovariectomized‐hysterectomized (OH) mice. Three weeks later they were killed and the diameters of the ovarian, uterine, and femoral veins and the inferior vena cava were measured and averaged. The averages were compared with averages for O and OH mice bearing pellets of glass and of progesterone, testosterone, and estradiol‐17β without 16α‐OH. It is concluded that in castrate mice the size of ovarian and uterine veins is influenced not by the presence or absence of the uterus but by sex steroids, that progesterone usually causes decreases while testosterone and estradiol‐17β cause increases in vein diameter, and that both the presence of the uterus and the administration of 1 % 16α‐OH are associated with partial inhibition of increases in vein size induced by steroids. Uterine hypertrophy and urinary bladder distention resulting from the administration of testosterone and estradiol‐17β were not prevented by the addition of 1 % 16α‐OH.
Hematopoiesis in the embryonic mouse spleen. II. Alterations after phenylhydrazine administration to the mothers
Authors: Djaldetti M. , Bessler H. , Fishman P. 
Published: February 2005

AbstractThe effect of phenylhydrazine (PHZ) on the hematopoietic events in the embryonic spleeen of C57Bl/6J mice was examined by light and electron microscopy. Following PHZ injections to the mothers, the embryonic spleen revealed a marked increase in erythroid precursors, with a shift to mature cells. This phenomenon was part of a more generalized stimulation of erythropoiesis, expressed by a shift to mature red cell precursors in the embryonic livers and an increase in the percentage of non‐nucleated cells in the embryonic peripheral blood. Concomitantly stimulation of phagocytosis in the spleen of embryos in the early gestational days and increased vascularity were observed, and a later effect of granulocytopoietic stimulation. The effect on erythropoiesis in the embryonic spleen might be a sequence of erythropoietin stimulation, either in the mothers or the fetuses, due to anemia and hypoxia following PHZ injections.
Conal contribution to the electrocardiogram of chick embryo hearts
Authors: Paff George H. , Boucek Robert J. 
Published: February 2005

AbstractContraction of the conus arteriosus (conus) is visibly delayed in the tubular heart of the chick embryo, and since the electromechanical coupling interval of isolated conal segment is similar to other areas of the embryonic heart, the delayed contraction of the conus indicated an impedance in the spread of the depolarization wave across the ventriculo‐conal (VC) junction.A surface electrode placed on the conus of hearts obtained from the 72‐hour chick embryo records a deflection, termed the C wave, appearing between the QRS complex and the T wave. To establish that the C wave arose from below the atrioventricular sulcus, atria were removed from a series of hearts from 96‐hour embryos and the electrogram revealed a C wave without a P wave.The VC junction responds to digitoxin just as the atrioventricular tissue. Digitoxin prolongs the interval between the QRS and the C wave prior to a complete block in a manner analogous to the PR interval increase prior to the development of the Wenckebach phenomenon or complete atrioventricular block.As the embryonic heart developed after 96 hours, the C wave was no longer identifiable in the ECG.
The effects of ringer‐locke or blood infusions on the lateral intercellular spaces of the rat proximal tubule
Authors: Bengele Howard H. , Evan Andrew P. 
Published: February 2005

AbstractDiuresis and natriuresis follow volume expansion by intravenous infusion of either blood or saline. However, the mechanisms underlying the renal responses seem different for the two types of expansion. It has been suggested that the response to saline expansion is due to changes in physical factors with alterations in the morphology of the lateral intercellular space (LIS). The present study examines the width of the LIS of the proximal tubule after a Ringer‐Locke (1%, 2.3%, or 7% body weight) or whole blood (2.3% body weight) infusion and in nonexpanded control. After Ringer‐Locke infusion, a significant widening of the LIS of the proximal tubule is seen at all levels of expansion. There is a linera relationship between the level of the Ringer‐Locke infusion and the degree of expansion of the LIS. In contrast, after blood volume expansion, the width of the LIS is the same as nonexpanded controls. These studies are consistent with the view that the renal response to saline expansion is mediated at least in part by physical factors affecting the proximal tubule.
Prenatal development of the grey lethal mouse. I. Teeth and Jaws
Authors: Hollinshead May B. , Schneider Lawrence C. , Smith Michael E. 
Published: February 2005

AbstractOsteopetrosis is a disease in which diffuse sclerosis of the entire skeleton results from an imbalance between the processes of bone formation and bone resorption. The grey lethal is the most severely affected of the three mouse mutants which have been described and its osteopetrosis is transmitted as a simple autosomal recessive gene. Affected mice develop a grey coat at 8–10 days of age and die before one month of age.Recently we (Hollinshead and Schneider, 1973) reported that grey lethal mice could be identified at birth because the apex of their lower incisors lies anterior to the molar region in the mandible. In this study we show that it is possible to identify affected fetuses from day 18 of gestation using the same and other histologic criteria in examining their teeth.
The influence of function on chondrogenesis at the epiphyseal cartilage of a growing long bone
Authors: Meikle Murray C. 
Published: February 2005

AbstractIn order to study the behaviour of epiphyseal cartilage in a nonfunctional environment, the third metacarpal bone was transplanted intracerebrally as an isograft between 7‐day‐old litter‐mate rats. Host animals were killed 1, 2, 3, 4, 5, 6 weeks post‐operatively, and the cellular kinetics evaluated by means of tritiated thymidine autoradiography. The study was also used to compare the effects of function on chondrogenesis at the epiphyseal cartilage with that previously demonstrated for the condylar cartilage of the mandible (Meikle, '73a).Transplantation resulted in three major changes in the cartilage; there was a decreased rate of proliferative activity in the cell columns; the cartilage failed to maintain a satisfactory increase in transverse diameter; the cells of the perichondrium differentiated into osteoblasts instead of chondroblasts. Autoradiographic and histological findings suggested that the inability of the cartilage to increase in transverse diameter was related to the decreased rate of proliferative activity in the cell columns and not to the cessation of perichondrial chondrogenesis. On the basis of these findings two conclusions can be made.1. Extrinsic mechanical stresses associated with function appear to be necessary for the normal interstitial growth of epiphyseal cartilage during postnatal development, suggesting that functional activity can influence the rate of cell proliferation.2. Functional activity provides the stimulus for the differentiation of perichondrial cells into chondroblasts.
Electron microscopic localization of calcium in vascular smooth muscle
Authors: Debbas Gamil , Hoffman Loren , Landon Erwin J. , Hurwitz Leon 
Published: February 2005

AbstractPotassium pyroantimonate has been employed in this study to localize calcium in the vascular smooth muscle of the thoracic aorta of the rabbit. The pyroantimonate ion precipitates sodium, magnesium and calcium. Incubation of the isolated thoracic aorta in a high potassium bathing medium which does not contain sodium, magnesium or calcium depletes the tissue of sodium. Addition of 10.8 mM CaCl2 to the incubation medium results in welllocalized depositions of reaction product, presumably that of calcium pyroantimonate, in mitochondria, sarcoplasmic reticulum, and at the plasma membrane. Some or all of these organelles may, therefore, play a vital role in the contractionrelaxation cycle of vascular smooth muscle.
The origin and fate of osteoclasts
Authors: Hall Brian K. 
Published: February 2005

AbstractDespite intensive and ingenious investigation, the origins and ultimate fate of the osteoclast remain shrouded in mystery. This brief review evaluates some of the recent experimental approaches used in the study of the osteoclast, especially whether they form from intra‐ or extra‐skeletal progenitor cells, whether from the same osteoprogenitor cell as the osteoblast, and whether, once formed, they may modulate to osteoblasts.That osteoprogenitor cells can, and do, become osteoclasts is well founded, as is the conclusion that such progenitor cells originate as blood‐borne, extraskeletal cells. Evidence that sessile, intra‐skeletal, progenitor cells can form osteoclasts is less direct. There is good evidence that osteoclasts both shed and take‐up nuclei, but no direct evidence that nuclear shedding is accompanied by death of the osteoclast, and no direct evidence for the fate of the shed nuclei. Whether the same osteoprogenitor cell can produce either an osteoblast or an osteoclast also remains an open question.
The effects of prostaglandin F2α on the fine structure of the corpus luteum of the hysterectomized guinea pig
Authors: Bagwell J. N. , Davies D. L. , Ruby J. R. 
Published: February 2005

AbstractLuteal cell fine structure was studied in hysterectomized control and hysterectomized, prostaglandin‐treated (1–5 days) guinea pigs. In hysterectomized control animals, luteal cells were hypertrophied and were characterized by an abundance of agranular endoplasmic reticulum (AER) suggesting steroidogenic activity. With one day of prostaglandin treatment, little change in the cytological appearance had occurred. After two, or three days of treatment, cells showed a decrease in size and an apparent increase in the number of lipid droplets. Following four days of prostaglandin treatment, luteal tissue was characterized by the presence of large amounts of collagen in the intercellular spaces and by the invasion of fibroblasts. Areas of degenerating luteal cells with numerous myelin figures and lipid droplets were observed. After five days of prostaglandin treatment, most of the luteal cells had undergone extensive luteolytic changes. Typically they contained coalescing lipid droplets, myelin figures and crystalloids, and were surrounded by collagen fibers. These observations suggest that prostaglandin F2α does effect structural luteolysis in this species in the absence of uterine tissue.
Changes in numbers of acidophilic and basophilic connective tissue granulated cells in the intestine of the rat during the estrous cycle
Authors: Johnson Shirley M. , Nellor John E. 
Published: February 2005

AbstractChanges in physiological reproductive states of female Long‐Evans hooded rats were directly correlated with changes in the concentration of acidophilic and basophilic connective tissue granulated cells in the lamina propria of the duodenum. Acidophilic granulated cell numbers were significantly higher at estrus and metestrus than at other stages of the estrous cycle or in the immature state. Acidophilic granulated cell numbers during pregnancy were not significantly different from cell numbers quantified during metestrus, diestrus, or proestrus, but were significantly lower than cell numbers during estrus. Late lactation (21‐25 days) was associated with significant decreases in the numbers of acidophilic granulated cells from numbers observed during the estrous cycle and during pregnancy. Basophilic granulated cell numbers did not differ significantly during the estrous cycle, although the highest numbers were observed during proestrus. Basophilic granulated cell numbers were significantly higher during pregnancy than during the estrous cycle. Basophilic granulated cell counts in late lactation were comparable to numbers quantified in estrus, metestrus, and diestrus, but were significantly lower than during proestrus and pregnancy.
Intercellular junctions of rat endocardium
Authors: Anversa Piero , Giacomelli Filiberto , Wiener Joseph 
Published: February 2005

AbstractThe ultrastructure of the intercellular junctions of rat endocardium has been characterized following lanthanum exposure in vitro and uranyl acetate staining en bloc. The interendothelial clefts of the endocardium run either a relatively straight or convoluted course and possess one or two loci where the plasma membranes are in close apposition or form punctate fusions. Elongate restrictions, that exhibit hexagonal arrays of subunits following lanthanum immersion (gap junctions), are also present in the intercellular endocardial clefts. The occurrence of interendothelial clefts of endocardium lacking occlusive foci can account for the permeability properties of ventricular endocardium, where the direction of diffusion of macromolecules has been attributed to pressure gradients between ventricular cavity and myocardium. The relationship of gap junctions to possible electrical phenomena within the endocardium is also discussed.
Cellular mechanisms involved in cyclic stromal renewal of the uterus. II. The albino rat
Authors: Padykula Helen A. , Campbell Ann G. 
Published: February 2005

AbstractDuring the first four days postpartum, heterophils (polymorphonuclear leucocytes) and macrophages occur in the intercellular compartment of the luminal epithelium of the uterine endometrium. Cytochemical and ultrastructural evidence indicates that transepithelial emigration of these stromal cells to the uterine cavity is occurring. This event takes place while the luminal epithelium is proliferating in response to the estrogenic stimulus of the postpartum estrus.Heterophil emigration precedes that of the macrophages and is most conspicuous during days 1 and 2. Although it has been established that collagen fibrils occur in uterine phagocytes (Schwarz and Güldner, 1967) assumed to be macrophages (Parakkal, 1969, 1972), their precise role in collagen degradation remains undefined. It seems likely that the emigrating macrophages, heavily laden with phagolysosomal derivatives and lipid droplets, are hauling the remnants of the intercellular substance out of the endometrium during days 2–4 postpartum. Ultrastructural evidence indicates that the emigrating macrophage punctures the basal lamina and passes through the intercellular compartment of the luminal epithelium by active penetration.Another mode of macrophagic egress operates in the deep stroma of the endometrium and myometrium where lymphatic drainage occurs. Macrophages accumulate in the perilymphatic stroma as well as within lymphatic vessels.Thus macrophagic emigration through the luminal epithelium and lymphatic vessels may provide a cellular mechanism for elimination of the intercellular stromal substance in the regressing uterus. Transepithelial emigration is a mechanism which operates also in the marsupial uterus (Padykula and Taylor, 1976), and thus may be a fundamental mechanism among subprimate mammals that fulfills in part the function that menstruation effects in primates.
The nonuniform distribution of acidic components on the human placental syncytial trophoblast surface membrane: A cytochemical and analytical study
Authors: Nelson D. Michael , Smith Carl H. , Enders Allen C. , Donohue Thomas M. 
Published: February 2005

AbstractThe surface coat of syncytial trophoblast from term human placentas was studied using cytochemical methods (colloidal iron, alcian bluelanthanum nitrate, dialyzed iron) in coordination with tissue enzyme digestions (trypsin, neuraminidase) and sialic acid analyses. The presence of at least two highly acidic anionic components that contribute significantly to the surface negativity of trophoblast has been demonstrated. The first of these, sialic acid, was removed with neuraminidase. Tissue digestion with this glycosidase was accompanied by a decrease in trophoblast surface staining with colloidal iron, a decrease in tissue sialic acid, and an increase in the concentration of sialic acid in the incubating medium. Results from methylation experiments were consistent with the presence of sialic acid. The second anionic component(s) was identified by removal with trypsin of a glycocalyx constituent that stained with both colloidal iron and lanthanum. After trypsinization, tissue sialic acid levels were not significantly different from control values, and no detectable sialic acid was present in the incubating medium. The identity of this anionic component has not been established. Both sialic acid and nonsialic acid acidic components are distributed in higher density on membrane of microvilli than on intermicrovillous surface membrane. In addition, the sialic acid moieties appear to be clustered in the glycocalyx.
Contributions to an analysis of the avian vitelline membrane's potential to promote outgrowth of the yolk sac‐serosal membrane
Authors: Haas Hermann J. , Spratt Nelson T. 
Published: February 2005

AbstractExplanted blastoderms of freshly laid chicken eggs expand their area during the first 44–45 hours of incubation by a factor of at least 11 if they are placed with the epiblast on the inner surface of explanted fresh chick vitelline membrane and provided with chick egg extract. This expansion is due essentially to the spreading of the yolk sac‐serosal membrane. On turkey and duck membrane the expansion factor is about 6 and 3.8 respectively under otherwise identical conditions, but 1.9 only on a semisolid nutrient agar plate. Only the inner surface of the vitelline membrane has this growth‐promoting potential, which markedly and progressively declines during incubation in ovo because of systemic factors rather than because of a direct influence by the outgrowing yolk sac‐serosal membrane. Trypsinization of fresh chick vitelline membrane (1% trypsin 3 hours) reduces the growth‐promoting potential to about 40% of its normal strength. The outgrowth of the extraembryonic tissues on vitelline membrane is better supported in the presence of a species' own egg extract than by extract from another species.
An autoradiographic study of tritiated uridine incorporation into the larval ovary of Xenopus laevis
Authors: Webb Andrew C. 
Published: February 2005

AbstractThe in vitro incorporation of 3H‐5‐uridine into the germinal and somatic cells of the larval ovary of Xenopus laevis has been studied using both light and electron microscope autoradiography. Incubation for only one hour in the presence of precursor revealed that the follicle cells are highly active in rRNA synthesis, whereas substantial oogonial nucleolar labeling was not detected for several hours. Semi‐quantitative analysis of high‐resolution autoradiograms indicated that the density of silver grains associated with “nuage” in oogonia was almost 4‐fold greater than the surrounding cytoplasm. This strongly suggests that a significant amount of RNA is associated with “nuage” at this stage of Xenopus oogenesis, in addition to its well documented protein composition. “Pulse‐chase” experiments further suggest that the nuage‐associated RNA is stable for at least 24 hours. These results are discussed (within the limitations imposed by the methodology) both in relation to other studies on the composition of nuage in a wide variety of germinal cell types and in the light of growing speculation that nuage and germinal granules are synonymous.
Cell differentiation in the terminal tubule of fetal rat submandibular gland in organ culture
Authors: Rufo Myra Bluestein , Barka Tibor 
Published: February 2005

AbstractSubmandibular glands from 17‐day‐old rat fetuses were maintained in organ culture for five days in a medium consisting of Eagle's MEM (87%), horse serum (10%), and chick embryo extract (3%). Each day of the culture period explants were incubated for the demonstration of peroxidase activity and processed for light and electron microscopic observations. In some experiments cultures were exposed to 3H‐thymidine one hour prior to fixation and incubation for the demonstration of peroxidase activity. Labelling index was determined using radioautographs of 1 μ Epon‐embedded sections. At the time of explantation the submandibular gland rudiment consisted of undifferentiated epithelial cells arranged in cords. On day 3 of culture two additional cell types could be distinguished: terminal tubule cells and proacinar cells. The proacinar cells were characterized by peroxidase activity in their granules and cytoplasm. By day 4 acinar cells begin to appear. On the fifth day of culture the four cell types of the terminal tubule were present in the following proportions: undifferentiated cells, 44%; terminal tubule cells, 19%; proacinar cells, 31%; acinar cells, 6%. These results indicate that the cytodifferentiation of the secretory unit of rat submandibular gland in vitro is comparable to the differentiation in vivo.