bluuebunny/crossref_metadata_2025_split huggingface dataset:
Radioautographic tracing of 3H‐proline in the endodermal cells of the parietal yolk sac as an indicator of the biogenesis of basement membrane components
Authors: Mazariegos Mario R. , Leblond C. P. , van der Rest Michel 
Published: February 2005

AbstractThe biogenesis of basement‐membrane components was investigated in the endodermal cells of the rat parietal yolk sac in 12.5‐day pregnant rats; 3H‐proline was injected into conceptuses. After various time intervals, the parietal yolk sac, including endodermal cells and the associated Reichert's membrane, was removed and processed for electron‐microscopic radioautography. Silver grains were counted over endodermal cell organelles and Reichert's membrane.At 2 and 5 min after 3H‐proline injection, endodermal cells showed heavy labeling in rough endoplasmic reticulum (rER). Silver grain density over the rER decreased from 2 to 20 min and then remained at a plateau. Grain density was moderate over the Golgi apparatus initially but rose to a peak at 2 hr and decreased by 4 hr and later. Grain density was negligible over secretory granules at 2 and 5 min and increased moderately with time to reach a maximum at 8 hr. Thus, radioautographic peaks occurred sequentially in rER, Golgi apparatus, and secretory granules. By 4 hr and later, silver grains accumulated over Reichert's membrane. These results indicated that endodermal cells incorporated labeled proline into substances which were processed from the rER through the Golgi apparatus, transported from there to the cell surface by secretory granules, and released for export to Reichert's membrane.To clarify the nature of the exported substances, the amount of label present in proline and hydroxyproline residues after 3H‐proline injection was measured in Reichert's membrane with or without the associated endodermal cells. Within the cells, 61.8% of the labeled proteins were classified as “sedentary” and 38.2% as “exportable.” Of the label exported to Reichert's membrane, 66.3% consisted of type IV collagen and the rest of other basement‐membrane components.The results obtained with this model suggest that basement‐membrane proteins, including type IV collagen, are elaborated by the associated cells through the classical pathway: rER‐Golgi apparatus‐secretory granules.
Tridimensional architecture of the Golgi apparatus and its components in mucous cells of Brunner's glands of the mouse
Authors: Rambourg A. , Clermont Y. , Hermo L. , Segretain D. 
Published: February 2005

AbstractThe three‐dimensional structure of the Golgi apparatus and its components has been analyzed in thin and thick sections of mucous cells of mouse Brunner's glands by using low‐ and high‐voltage electron microscopes and a stereoscopic approach. In thick sections of glands impregnated with osmium or treated to detect nicotinamide adenine dinucleotide phosphatase (NADPase) or thiamine pyrophosphatase (TPPase) activity, the Golgi apparatus appeared, at low magnification, as a continuous network located in the supranuclear region. At higher magnifications and in thin sections of tissue postfixed with reduced osmium and stained with lead citrate or treated to demonstrate phosphatase activity, the following components were observed: (1) on the cis‐face of the Golgi stacks, an osmiophilic tubular network referred to as the cis‐element; (2) a cis‐saccular‐compartment composed of a distended porous saccule slightly reactive for NADPase and three or four underlying NADPase‐positive, flattened, poorly fenestrated saccules; (3) a trans‐saccular‐compartment consisting of four to six TPPase‐positive saccules or sacculo‐tubular elements, prosecretory granules, and “peeling off” trans‐tubular networks.The saccules of the cis‐compartment were often perforated by large pores in register. The cavities thus formed in the stacks were called wells and were pan‐shaped with a mouth directed toward the cis‐face of the stacks and a bottom closed by TPPase‐positive saccules. The wells always contained 80‐nm vesicles. The saccules of the trans‐compartment were involved in the formation of secretory granules according to the following proposed sequence of transformation. The secretion product appeared initially as a granular material evenly distributed throughout a slightly distended, poorly fenestrated saccule. These saccules appeared to transform into fenestrated elements with irregular pores and with parts of them taking on the appearance of a tubular network; they were thus referred to as sacculotubular elements. The secretory material initially distributed throughout these elements accumulated in nodular dilatations randomly distributed along the tubular portions of the elements. The dilatations, considered as prosecretory granules, increased in size as they drained the secretory material from the rest of the sacculotubular elements. Such prosecretory granules, large and irregular in shape, “peeled off” from the stacks of saccules with residual saccular or tubular structures still attached to them, some of the latter forming trans‐tubular networks. The prosecretory granules detached from such membranous residues, condensed, and finally transformed into spherical secretion granules.
Myocardial capillaries in the fetal and the neonatal rat: A morphometric analysis of the maturing myocardial capillary bed
Authors: Porter Glyn A. , Bankston Patrick W. 
Published: February 2005

AbstractDeveloping myocardial capillaries from 16‐day‐gestation fetus to adult undergo several morphological changes including a thinning of the lateral extensions of the capillary endothelial cells, the formation of a basal lamina, and an increase in the number of plasmalemmal vesicles. A decrease in the extracellular space, an increase in the number of capillaries, and a decrease in the capillary diameter were also observed during the developmental period. In view of these ultrastructural changes, a morphometric analysis was made on the developing myocardial wall to demonstrate specific quantitative changes. The volumes which were occupied by capillary endothelial cells, capillary lumina, extracellular space, and myocardial myocytes within a reference volume of myocardium were measured; and we found that 8% of the reference myocardial volume was occupied by capillary endothelial cells, 85% was occupied by myocardial myocytes, 4% was occupied by capillary lumina, and, except for a significant change in extracellular space at 16 days gestation, 3% was occupied by extracellular space. Each volume ratio was found to be nearly constant throughout the studied period. In contrast to this constancy in the volume ratios, other parameters which were measured demonstrated significant changes during the developmental period studied. These overall changes include a 135% increase in capillary density, a 63% increase in luminal surface area of capillary endothelial cells, a 24% decrease in capillary diameter, a 12% decrease in diffusion distance, and a 35% decrease in the diameter of the erythrocyte population. The decrease in capillary diameter occurs concomitantly with and may be correlated to the decrease in erythrocyte diameter. Also, the increasing number of capillaries offset the effect of the decrease in capillary diameter, resulting in constant volume ratios. This constancy in the volumes of the measured myocardial compartments during development, despite the considerable changes in morphology and in the other measured parameters which are occurring in the myocardial wall, can be interpreted to mean that some functional constraints are operating to maintain capillary‐to‐myocardium volume ratios within very narrow limits.
Splenic hypertrophy and extramedullary hematopoiesis induced in male Syrian hamsters by short photoperiod or melatonin injections and reversed by melatonin pellets or pinealectomy
Authors: Vaughan M. K. , Hubbard G. B. , Champney T. H. , Vaughan G. M. , Little J. C. , Reiter R. J. 
Published: February 2005

AbstractAdult male Syrian hamsters either placed in a short photoperiod alone or kept in a long photoperiod and given daily afternoon injections of the pineal indole melatonin (25 μg) exhibited splenic hypertrophy and extramedullary hematopoiesis in addition to a marked regression in testicular weight. The testicular regression as well as the changes in spleen weight and histology could be prevented if the animals in short photoperiod were either pinealectomized or implanted subcutaneously with a pellet containing 1 mg melatonin. Female Syrian hamsters given afternoon injections of melatonin for 7 or 12 weeks had ovaries devoid of corpora lutea; additionally, these animals had reduced relative spleen weights compared to the control animals. In conclusion, it is apparent that spleen weight varies with the functional status of the gonads. Splenic hypertrophy accompanied by pineal‐induced testicular regression in males may be related to splenic extramedullary hematopoiesis.
Ultrastructure of neural crest formation in the midbrain/rostral hindbrain and preotic hindbrain regions of the mouse embryo
Authors: Nichols David H. 
Published: February 2005

AbstractIn the mouse embryo, neural crest mesenchyme associated with the first and second pharyngeal arches escapes from the epithelium that forms the tips of the midbrain/rostral hindbrain and preotic hindbrain neural folds. To investigate the ultrastructure of crest formation, embryos with four to eight pairs of somites were processed for transmission electron microscopy. In the earliest event related to crest formation, crest precursors in the midbrain/rostral hindbrain elongated and moved all or most of their contents to the basal region of the epithelium. Elongation was probably mediated by apical bands of micro‐filaments and longitudinally oriented microtubules. Elongated cells then relinquished apical associations while nonelongated cells maintained those associations and withdrew from the basal lamina. This resulted in an epithelium stratified into apical and basal (crest precursor) layers. The coalescence of enlarging extra‐cellular spaces opened a delaminate gap between the two layers. Additional crest precursors entered this gap from the apical layer. From the time crest precursors began moving basally, some formed microfilament‐ and/or microtubule‐containing processes, which penetrated the basal lamina. Some of these cells moved their contents into the larger, microtubule‐containing processes, perhaps thereby escaping from the epithelium. Soon after elongating cells appeared, the basal lamina beneath the epithelium began to degrade in a pattern unrelated to process formation. This ultimately resulted in disruption of the lamina, dispersal of the basal layer of the epithelium, and release of the crest precursors in the delaminate gap. Once crest formation was complete, the apical layer reformed a basal lamina on a patch‐by‐patch, cell‐by‐cell basis. In the preotic hind‐brain, elongating crest precursors apparently forced their basal faces through the basal lamina and then relinquished apical association to escape. As a result, the lamina was disrupted before the epithelium could stratify, and enlarged extracellular spaces appeared among mesenchymal cells rather than creating a delaminate gap. The failure of elongation to disrupt the basal lamina in the midbrain/rostral hindbrain and its success in the preotic hindbrain might be due to less‐vigorous, less‐concerted elongation in the midbrain/rostral hindbrain or to earlier, more rapid degradation of the lamina in the preotic hindbrain.
Ultrastructural localization of heparan sulfate and chondroitin sulfates associated with granulopoiesis in embryonic chick bone marrow
Authors: Sorrell J. Michael , Voci Matthew , Weiss Leon 
Published: February 2005

AbstractSulfated glycoconjugates were ultra‐structurally localized within embryonic chick marrow by using the high iron diamine–silver proteinate stain. Stain was concentrated in the extravascular, granulopoietic compartment, indicating that granulopoiesis, but not erythropoiesis, proceeded in a highly sulfated environment. It was likely that most of the stainable material represented sulfated proteoglycans since staining was abrogated by predigesting tissue with enzymes and other treatments known to degrade specific glycosaminoglycan chains. Chondroitinase/hyaluronidase digestion resulted in the removal of most of the stainable material associated with the extracellular matrix and a portion of the stainable material associated with fibroblastic cell surfaces. Unaffected material lay in close proximity to fibroblastic cell membranes. Heparitinase/heparinase digestion had essentially the opposite effect. Sulfated material associated with matrix components was largely unaffected, but the fibroblastic plasmalemmal material was now absent. These results suggest that there are at least two categories of sulfated proteoglycans in the granulopoietic compartment, each differentially distributed. The plasmalemmal material likely represented heparan sulfate which in this tissue appeared to be associated in a uniform layer with fibroblastic stromal cell membranes and not with blood or endothelial cell membranes. Material identified as chondroitin sulfates was found within patches of amorphous matrix that was located on fibroblastic stromal cell surfaces and that was interspersed with fibrils in the extracellular matrix. Chondroitin sulfates were sparsely distributed on granulocytic cell surfaces.
Opossum adrenal medulla: II. Differentiation of the chromaffin cell
Authors: Spagnoli Daniel B. , Frederickson Richard G. , Robinson Robert L. , Carmichael Stephen W. 
Published: February 2005

AbstractThe ultrastructure of the opossum adrenal medulla was examined in its postnatal development. Maturation of chromaffin cells and genesis of chromaffin vesicles were of particular interest. The primitive sympathetic cell was seen to contain few organelles with no apparent polarity. Initial pheochro‐moblasts contained more organelles with some polarity. Endoplasmic reticulum and the Golgi complex increased as the pheochromoblasts matured, which suggested increased synthetic activity. Structures resembling Golgi/endoplasmic reticulum/lysosome (GERL) systems were seen in the pheochromoblasts. It is suggested that some of the components of the chromaffin vesicle may be processed by the GERL while others come directly through the Golgi complex. It is stressed that the developing pheochromoblast in the opossum presents an interesting model in which to study the genesis of the chromaffin vesicle.
Projection of cervical dorsal root fibers to the medulla oblongata in the brush‐tailed possum, Trichosurus vulpecula
Authors: Culberson James L. 
Published: February 2005

AbstractThis study describes the projection of cervical spinal afferent nerve fibers to the medulla in the brush‐tailed possum, a marsupial mammal. After single dorsal roots (between C2 and T1) were cut in a series of animals, the Fink‐Heimer method was used to demonstrate the projection fields of fibers entering the CNS via specific dorsal roots. In the high cervical spinal cord, afferent fibers from each dorsal root form a discrete layer in the dorsal funiculus. The flattened laminae from upper cervical levels are lateral and those from lower cervical levels are medial within the dorsal columns. All afferent fibers at this level are separated from gray matter by the corticospinal fibers in the dorsal funiculus. All cervical roots project throughout most of the length of the well‐developed main cuneate nucleus in a loosely segmentotopic fashion. Fibers from rostral roots enter more lateral parts of the nucleus, and fibers from lower levels pass to more medial areas; but terminal projection fields are typically large and overlap extensively. At more rostral medullary levels, fibers from all cervical dorsal roots also reach the external cuneate nucleus. The spatial arrangement here is more complex and more extensively overlapped than in the cuneate nucleus. Rostral cervical root fibers reach ventral and ventrolateral areas of the external cuneate nucleus and continue to its rostral pole; more caudal root fibers project to more dorsal and medial regions within the nucleus. These results demonstrate that projection patterns of spinal afferents in this marsupial are similar to those seen in the few placental species for which detailed data concerning this system are available.
Decidual cells in the human ovary at term: II. Morphometric analysis of cytoplasmic processes and organelles
Authors: Herr John C. , Fares Nagui H. , Banhawy Mohammed A. 
Published: February 2005

AbstractMorphometric analysis of human ovarian decidual cells was performed with a Videoplan computer, and mean values were established for the area and perimeter of cellular processes and organelles. Two‐hundred forty electron micrographs representing 160 cells were analyzed. The mean decidual cell area was 218.7 μm2 of which 34.5 μm2 was occupied by the nucleus (15.8% of the cytoplasmic area); the nucleus contained 1.74 μm2 of nucleolar material (0.8%). The endoplasmic reticulum occupied 13.63 μm2 (6.2%). Mitochondria occupied 7.3 μm2 (3.3%) and the Golgi network 5.49 μm2 (2.5%). Decidual secretory bodies occupied 0.91 μm2 (0.42%) and cytoplasmic processes 1.89 μm2 (0.94%). The remainder of the cytoplasm, containing inclusions and cytoskeleton, represented 71% of the cell area. Perimeter measurements indicated an average decidual cell was surrounded by 87.8 μm of plasma membrane. The mean nuclear membrane measured 28.3 μm (representing 32.3% of the plasma membrane, pm, or 4.1% of total cellular membranes, cm). Outer mitochondrial membranes measured 156.6 μm (178% pm, 23.5% cm); endoplasmic reticulum membranes measured 350.3 μm (400% pm, 52.6% cm); Golgi membrane measured 30.77 μm (35% pm; 4.5% cm) and membrane surrounding secretory bodies measured 9.8 μm (11.2% pm; 1.4% cm). A mean of 280 secretory bodies per ovarian decidual cell was calculated. The plasma membranes of evaginated cytoplasmic processes represented 22.3% of the total pm (19.6 μm or 2.9% cm). A mean of seven such processes was observed per 87.8 μm of plasma membrane (160/cell). These morphometric data provide a baseline for comparisons of human ovarian decidual cells with uterine decidua, in vivo and in vitro, as well as with decidual cells of other species.
Ultrastructure of cardiocyte degeneration and myocardial calcification in the dystrophic hamster
Authors: Burbach James A. 
Published: February 2005

AbstractThe myocardium of the Bio 14.6 cardiomyopathic hamster was examined with the electron microscope to identify cellular and organelle changes during the acute lesioning stage, a period typified by concomitant cardiocyte destruction and calcium elevation. Most cardiocytes retained their normal histologic and ultrastructural features, but scattered foci of altered and necrotic cells were observed in association with degenerative calcifying lesions. Prenecrotic alterations of myocytes included cellular edema; varying degrees of distension of sarcoplasmic reticulum and T‐tubules; contraction bands and other myofibrillar abnormalities; mitochondrial clustering and hyperplasia; a wide spectrum of mitochondrial changes such as altered sizes, shapes, and cristal patterns, and increases in the number and size of osmiophilic matrix inclusions. Morphologic features consistent with substantial calcium excess were not observed in most altered but prenecrotic cells. Instead, calcium deposition within extruded mitochondria and upon degenerating organelle debris was observed only after cardiocyte disruption. Some calcifying cell remnants were phagocytized by macrophages, whereas large calcified plaques and other deposits remained in the interstitium. Mitochondrial calcification in vascular smooth muscle cells and fibroblasts was evident in highly calcified lesions. These observations suggest that most of the morphologically identifiable calcium deposition present in this cardiomyopathy results from secondary calcification subsequent to sarcolemmal disruption.
Biological time and the effects of hydroxyurea on DNA synthetic activity of bone marrow and tumor cells in mice bearing the Ehrlich ascites carcinoma
Authors: Burns E. Robert 
Published: February 2005

AbstractThe objective of this experiment was to attempt to induce, with hydroxyurea (HU), significant quantitative differences in the level of DNA‐synthetic activity (DNA‐SA) between a neoplastic cell population (the Ehrlich ascites carcinoma or EAC) and bone marrow in the same animal. Mice bearing a 5‐day‐old EAC were standardized to and kept on an LD 12:12 cycle (light 0600–1800 hr). They were treated with 500 mg/kg HU at 0500 hr (23 hr after lights on, or HALO) or at 1700 hr (11 HALO). DNA‐SA was determined by liquid scintillation counting of 3H‐thymidine incorporation into chemically isolated DNA. DNA‐SA in bone marrow and EAC cells was monitored over the next 60 hr with subgroups of ten mice each killed every 3 hr beginning 3 hr after treatment with HU. The circadian system of the host influenced the response of the bone marrow to HU; i.e., the response to HU administered at 0500 hr was different both qualitatively and quantitatively from that for HU given at 1700 hr. Comparisons of DNA‐SA in bone marrow and EAC from the same animal revealed time points after treatment with HU when DNA‐SA in the EAC was high, but DNA‐SA in bone marrow was low. These differences in the level of DNA‐SA between a tumor cell population and bone marrow should be of therapeutic value; i.e., executor doses of anti‐DNA‐SA drugs such as cytosine arabinoside could be given at that point in time after treatment with HU when DNA‐SA in the tumor was high, but DNA‐SA in the bone marrow was low.
Estrogen‐induced tumors: Changes in the vasculature in two strains of rat
Authors: Schechter Joel , Ahmad Nazir , Elias Kathleen , Weiner Richard 
Published: February 2005

AbstractThe influence of estrogen on the vasculature of the pars distalis has been studied in two strains of rat that differ in estrogen responsiveness. (Fischer 344 rats are highly estrogen‐responsive in comparison to Sprague‐Dawley rats.) Ovariectomized adults were implanted with silastic capsules containing 17 β‐estradiol benzoate. Control and experimental animals were sacrificed 10 and 20 days after implantation of the silastic capsules.Pituitary weights and plasma prolactin were elevated dramatically in estrogen‐treated Fischer rats in comparison to more moderate increases in Sprague‐Dawley rats. Although both strains exhibited the hypertrophy of mammotrophs expected after estrogen stimulation, the vasculature in Fischer rats was dramatically altered from normal. The pars distalis of the 20‐day, estrogen‐treated Fischer rats contained well‐formed arteries. In addition, capillaries frequently were disrupted, contributing to the formation of hemorrhagic lakes unlined by an endothelium. Even in intact capillaries, basal laminae delimiting the pericapillary spaces often were disrupted or absent. Perivascular connective tissue cells were prominent within the perivascular spaces and often contained rumerous, large lysosomal dense bodies as well as clusters of small dumbbell‐shaped bodies. These granule clusters also were apparent adjacent to the perivascular space within parenchymal cells, most frequently within follicular cells.The vasculature of Sprague‐Dawley rats maintained a more normal appearance after estrogen treatment, although perivascular connective tissue cells did appear activated and basal laminae delimiting the pericapillary spaces were disrupted occasionally. However, no capillaries were disrupted, nor were any hemorrhagic lakes evident, and no arteries were present.The results indicate that in some strains of rat, estrogen may influence the integrity of the pars distalis vasculature, including the possibility of stimulating vascular reorganization and arteriogenesis. If stimulation of arteriogenesis decreases normal hypothalamic inhibition of mammotrophs, this could be an important factor underlying the formation of prolactinomas.