bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regeneration in free grafts of normal and denervated muscles in the rat: Morphology and histochemistry
Authors: Carlson Bruce M. , Gutmann Ernest 
Published: February 2005

AbstractIntact soleus and extensor digitorum longus muscles in the rat were freely grafted to the contralateral leg after either no preliminary tretment or 14 days prior denervation. Normal muscle grafts during the first week were characterized by a central zone of degenerating original muscle fibers (disappearing by 7–9 days) and a peripheral zone, containing regenerating muscle as well as small numbers of surviving original muscle fibers. A radial gradient of regeneration was established, with more mature muscle at the periphery and less mature muscle toward the center. Denervated grafts were characterized by rapid degeneration (within 2–3 days ) of original muscle fibers in the central area, rapid appearance of regenerating muscle fibers (e.g., cross striations by 5 days) with uniform levels of differentiation throughout the graft and larger numbers of surviving original muscle fibers at the periphery. During the first week, stages of muscle differentiation in denervated grafts were attained 1–2 days earlier than comparable stages in normal grafts. Later stages of muscle differentiation were similar in both types of grafts. Histochemical studies revealed a loss of enzyme activity (phosphorylase, ATPase and SDH) in the center of early (2–4‐day) normal and denervated grafts. Denervated grafts, however, possessed a thicker peripheral rim of enzymatically active surviving muscle fibers than normal grafts. In both types of grafts the old muscle fibers in the center were replaced by enzymatically active regenerating muscle fibers which stained uniformly (ATPase) until 30 days. By 60 days a mixed fiber pattern had developed. Muscle spindles were found within the grafts.
Life span of small lymphocytes in the thymolymphatic tissues of normal and thymus‐deprived BALB/C mice
Authors: Röpke C. , Everett N. B. 
Published: February 2005

AbstractAutoradiography and scintillation counting have been used after various schedules of 3H‐thymidine injections to evaluate lymphocyte kinetics in normal and thymus‐deprived BALB/C mice. The thymus was found to be an active production site of small lymphocytes, the majority of these cells having thymic residence times of three to five days. Peripheral lymphoid tissues – including spleen, lymph nodes and Peyer's patches – were dominated by long‐lived lymphocytes and produced very few small lymphocytes. Nearly identical percentages of long‐lived lymphocytes with comparable grain counts were found in the peripheral tissues. In adult thymectomized animals, and in mice thymectomized and reconstituted with bone marrow cells following total body irradiation, percentages and lifespan of long‐lived lymphocytes were found to be of the same order as in normal or sham‐operated controls. It is concluded that T cells in the peripheral long‐lived pool can be formed outside the thymus and that the bone marrow probably produces long‐lived B lymphocytes.
Electron microscopy of endothelial microvilli of large arteries
Authors: Fujimoto Sunao , Yamamoto Koji , Takeshige Yoshio 
Published: February 2005

AbstractScanning electron microscopic investigations by others have revealed “hair‐like” projections from the endothelial surface of the rabbit aorta. We have confirmed by transmission electron microscopy that endothelial microvilli are found, in a limited number of areas in the aortic arch, particularly at the presumed site of fetal origin of the ductus arteriosus and near the origin of the subclavian artery.The microvilli are almost uniform in diameter (about 0.1 μm) and are as long as 3 μm in length. The outer leaflet of the limiting membrane shows a fuzzy appearance, and thin filaments are recognized in their interiors.A profuse array of endothelial microvilli was also found over the entire surface of the large arteries of human fetuses. The possible hemodynamic significance of these processes is discussed.
The sertoli cell junctional specializations and their relationship to the germinal epithelium as observed after efferent ductule ligation
Authors: Ross Michael H. , Dobler Johanna 
Published: February 2005

AbstractSeminiferous tubules from testes of normal and efferent ductule ligated mice were examined with the electron microscope. The tubules in the ligated animals were markedly distended and at most stages of the seminiferous cycle the epithelium exhibited a series of circumferentially‐oriented ridges. Cross‐sectional profiles of these ridges were studied with particular emphasis on the Sertoli cell junctional specializations and their relationship to the germinal cells.In the ligated specimen the basal cytoplasm of the Sertoli cells is highly attenuated, often appearing as a thin process resting on the basement lamina. Where the cytoplasm of one Sertoli cell ends, it meets in apposition with the cytoplasm of an adjoining Sertoli cell, and at these sites, junctional specializations are present. The ridges are comprised of a stalk of apical Sertoli cell cytoplasm, often appearing like an inverted cone, with young spermatids aligned along the lateral surfaces and the more mature spermatid population embedded within the apical cytoplasm. Junctional specializations were observed along these lateral Sertoli cell surfaces. In some instances, they formed a free surface, but usually early spermatids were in contact with the junctional specializations. With respect to the more mature spermatids, the acrosomal component was typically found in relation to a junctional specialization. Germ cells at the spermatocyte stage were also noted in relation to the Sertoli cell junctional specializations.The findings suggest that spermatocytes cross the Sertoli cell barrier and gain access to the adluminal compartment of the seminiferous tubule through the disengagement of the inter‐Sertoli cell junctional complex. It is proposed that when the inter‐Sertoli cell junctional specializations separate, the spermatocytes come in apposition with the newly freed junctional surfaces and remain in relation with them through the ensuing divisions. It appears that at some point, firm adhesion between germ cells and the junctional specializations occurs; the spermatid progeny may thus maintain contact with the original inter‐Sertoli cell junctional specializations until their release into the tubule lumen.
Observations on the fine structure of propylthiouracil‐induced “brown degeneration” in the zona reticularis of mouse adrenal cortex
Authors: Moore N. A. , Callas Gerald 
Published: February 2005

AbstractPropylthiouracil (6‐propyl‐2‐thiouracil), an anti‐thyroid agent, was fed to mice in a concentration equal to 0.1% of their diet for periods of 10 and 15 weeks. The cells of the inner zone of the adrenal cortex were examined with the electron microscope. In animals receiving propylthiouracil for ten weeks mitochondria were altered and the smooth endoplasmic reticulum (SER) showed a marked focal proliferation. In contrast to control animals rough endoplasmic reticulum was abundant and was frequently associated with the hyperplastic SER. After 15 weeks these alterations were no longer present but had been replaced by a spectrum of “brown degeneration.” The less affected cells were characterized by increased numbers of liposomes and lysosomes and the more affected cells by liposomal and mitochondrial degeneration. These observations emphasize that “brown degeneration” is a true degenerative process and not a spontaneous proliferation of ceroid pigment. It is suggested that the changes described may be directly related to an alteration in cholesterol metabolism.
Chondroitin sulfate and electron lucent bodies in the pericellular rim about unshrunken hypertrophied chondrocytes of chick long bone
Authors: Kashiwa Herbert K. , Luchtel Daniel L. , Park Han Z. 
Published: February 2005

AbstractDirect observation of unstained, 1 mm thick blocks of fresh epiphyseal cartilage from tibia of 15‐ and 18‐day‐old chick embryos revealed shrunken chondrocytes on its cut surfaces but unshrunken chondrocytes deep within the tissue blocks. The unshrunken hypertrophied chondrocytes are rimmed with refractile substance identified as chondroitin sulfate removable with hyaluronidase. This substance is stained metachromatically red with toluidine blue, and is stained with ruthenium red and with ruthenium red‐OsO4. The latter, observed with the electron microscope, is present as an electron dense rim, specifically about the unshrunken, hypertrophied chondrocytes between the plasma membrane and lacunar wall. By rendering the chondroitin sulfate electron dense with RR‐OsO4, electron lucent bodies (ELB) were revealed specifically about the hypertrophied chondrocytes. The ELB contain an electron dense core with radiating fibrils. The content and source of ELB, also found in the intercellular matrix, are not known. The 0.1% toluidine blue solution containing 0.2 m MgCl2 or 0.4% NaCl or KCl stained juxtanuclear clusters of granules metachromatically red. The location of intracellular granules was believed to represent a cluster of Golgi‐derived vesicles. The pericellular metachromatic, RR‐OsO4‐positive rim is believed to be an accumulation of externalized juxtanuclear metachromatic granules. The possibility that the ELB may also be externalized content of Golgi vesicles was entertained.
Transmission and scanning electron microscope studies of calcified cartilage resorption
Authors: Savostin‐Asling Irene , Asling C. Willet 
Published: February 2005

AbstractThe authors' previous report (Savostin‐Asling and Asling, 1973) demonstrated that Meckel's cartilage is a favorable site for study of calcified cartilage resorption. In the present study the ultrastructural features at this resorption front have been examined by transmission and scanning electron microscopes (19‐day rat fetus). Multinucleated giant cells (chondroclasts) dominated the erosion front. The many features which they showed in common with osteoclasts included abundant mitochondria, vacuolation, lysosomes, sparsity of roughsurfaced endoplasmic reticulum, and deep infoldings at loci of contact with calcified matrix. Crumbling of matrix (with mineral crystals penetrating between these foldings) and fragmentation of collagen fibrils were also seen. The propensity of chondroclasts for spanning several opened lacunae provided special opportunity to demonstrate cell surface modifications in presence or absence of matrix contact. Ameboid processes extending into lacunae were seen by both transmission and scanning procedures; they were sometimes tipped with a veil of filamentous processes as small as 0.3 μm in diameter. Most hypertrophic chondrocytes, when released from lacunae, appeared to be disintegrating. However, in accord with previous evidence of their possible merger with chondroclasts (in light microscopic studies) there was also evidence for breakdown of cell walls between a chondroclast and a chondrocyte in intimate contact, with possibility of cytoplasmic continuity.
An angiographic study of the fox testis in various stages of sexual activity
Authors: Joffre M. , Kormano M. 
Published: February 2005

AbstractThe arteries and veins of the fox testis were studied using an angiographic technique. The postnatal development of the testis involved only minor modification of the vasculature. In the non‐breeding season both the arteries and veins of the adult fox testis undergo extensive spiralization which completaly disappears during the breeding season. When the sequence of morphological changes in blood vessels are related to available data on changes in testicular size, blood flow and connective tissue content, it is obvious that the vascular spiralization is passive and related to shrinkage of the organ and does not primarily influence the testicular blood flow.
Appearance and disappearance of multiply ciliated follicular cells during development of the dog's thyroid gland
Authors: Nunez Eladio A. , Gershon Michael D. 
Published: February 2005

AbstractMultiply ciliated follicular cells have been observed in developing thyroid glands in dogs. These cells are prominent three weeks prior to the expected date of birth but become progressively less common as development proceeds. After birth only rare isolated cilia remain. No evidence of removal of cilia by autophagy or loss into colloid was found. It is concluded that cilia are probably no longer formed by mature cells and that those already present are diluted out by progressive division of mature follicular cells.
The use of ultraviolet light to induce melanogenesis in the epidermis of the rhesus monkey: An ultrastructural and biochemical study
Authors: Erickson Kent L. 
Published: February 2005

AbstractThe general body epidermis of the rhesus monkey (Macaca mulatta) contains no discernible melanocytes, but after repeated ultraviolet irradiation DOPA‐positive melanocytes appear and increase numerically up to 30 exposures. With continued irradiation, however, the number again declines.Experiments to determine how melanogenic activity, assayed by the incorporation of labeled DOPA or tyrosine, is related to DOPA positivity indicated that biochemical activity corresponded to the histochemical pattern. Ultrastructural studies demonstrated that after the exposure to ultraviolet light, a pool of indeterminate cells in the skin of rhesus monkeys developed into melanocytes. The melanosomes formed by these cells, however, differed from the eumelanin melanosomes described in other species; they had no internal filamentous matrix with periodicity but appeared similar to phaeomelanin melanosomes. Long term ultraviolet light irradiation may damage keratinocytes and render them incapable of phagocytizing melanosomes.
Kinetics of intraepithelial lymphocytes in the small intestine of thymus‐deprived mice and antigen‐deprived mice
Authors: Röpke C. , Everett N. B. 
Published: February 2005

AbstractThe kinetics of lymphoid cells within the epithelium of the small gut has been studied in various thymus‐deprived mice and in antigen‐deprived mice by the use of 3H‐thymidine injections and radioautography. In thymusdeprived mice —including adult thymectomized, thymectomized and irradiated, neonatally thymectomized, and nude mice —and in germ‐free mice decreased numbers of intraepithelial lymphocytes (IL) were found. On the other hand, the radioautographic results indicated that the remaining IL populations included both newly formed and long‐lived lymphoid cells in the same percentages as found in sham‐operated controls and normal mice. It is concluded that although the presence of the thymus and the antigen content of the gut is of importance to the maintenance of the numbers of cells in the lymphoid populations of the intestinal wall, the basic kinetics of these cell populations are preserved in deprived mice.
A study of germ cell morphology and duration of spermatogenic cycle in the baboon, Papio anubis
Authors: Chowdhury A. K. , Steinberger E. 
Published: February 2005

AbstractBiopsy and orchiectomy specimens were collected from two adult baboons (Papio anubis) at different intervals after intratesticular injection of H3‐thymidine. Zenker‐formol or Bouin's fixed materials were stained with PASWeigert‐Hematoxylin and radioautographed using the H.S.R. (Harleco Synthetic Resin) coating technique. Morphological features of most germ cells appeared similar to those of other monkeys, except that the spermatids in steps 9 to 11 showed a spike‐like projection of the acrosome. Also, the type A spermatogonia showed some resemblance to the human type A spermatogonia. The cell associations consisted of 12 stages and a large number of tubular cross sections showed the presence of two or more stages. In Papio anubis, the zygotene spermatocytes are formed in stage VIII, and spermatozoa are released during stages V and VI.H3‐thymidine labeling of germ cells indicated that one cycle of spermatogenesis in this species takes approximately 11 days, and complete spermatogenesis occupies 3.8 cycles, or approximately 42 days. The presence of labeled B type spermatogonia 35 days after H3‐thymidine injection indicated the existence of some stem cells. The presence of some labeled Ad spermatogonia in these specimens could not be explained. The data indicated that spermatogenesis in this monkey is somewhat different from that in other monkey species described.
Light microscopic and ultrastructural observations of the calcifying zone of the mandibular condyle in the rat
Authors: Larsson Åke 
Published: February 2005

AbstractThe hypertrophic stage of development of the rat mandibular condyle was investigated in 16 and 26‐day‐old rats by electron microscopy. Interest was focused on the zone of mineralization and erosion. It was observed that capillaries invaded the lower level of the hypertrophic zone, without any previous chondroclastic resorption of calcified partitions. The partitions surrounding the hypertrophic chondrocytes were not mineralized around their entire circumference at the level of capillary penetration. The capillaries were accompanied by perivascular cells but these showed no similarities to chondroclasts. Multinucleated chondro‐ or osteoclasts were however present at a lower level of the subchondral area. It is suggested that there are no inherent differences with respect to the pattern of mineralization and erosion between the epiphyseal growth plate and the developing mandibular condyle.
Numerical density of nuclei in the sheep placenta
Authors: Teasdale François 
Published: February 2005

AbstractA method is described for estimating the number of nuclei of different cell types in the sheep placenta. The method was applied to the study of six placentas of different ages and the results have been correlated with data on the chemical composition and the physiology of the ovine placenta. In agreement with studies of placental DNA content, there is no demonstrable increase in the total number of placental nuclei in the last two months of gestation. However, the number of fetal mesenchymal nuclei decreases and there is a concomitant increase of fetal endothelial nuclei from 80 days to term. These changes correlate with a decrease in volume of the core of the placental villi and increase in umbilical blood flow.
Astrocytic gap junctions in the rat lateral hypothalamic area
Authors: Sipe Jack C. , Moore Robert Y. 
Published: February 2005

AbstractAn extensive system of gap or nexus junctions has been found between astrocytic processes in the neuropil of the lateral hypothalamic area in the albino rat. These specialized interastrocytic junctions occur in regions of high synaptic density where neural processes are separated by the interconnected glial system. In this study, 90% of the gap junctions observed in the lateral hypothalamic neuropil are in the immediate proximity of synaptic terminals. The close morphological relationship of these glial gap junctions with synaptic contacts suggests that they may play a significant role in the process of synaptic transmission.
Lanthanum hydroxide labelling of gap junctions in the odontoblast layer
Authors: Holland G. R. 
Published: February 2005

AbstractEarlier work has suggested that terminal nerve fibers in the periphery of the dental pulp are linked to one another and to odontoblasts by gap junctions although positive identification of the junctions was lacking. In this study, the lanthanum hydroxide tracer technique has been used to demonstrate that the junctions in this area do have the characteristic features of gap junctions, a wide dark intermediate line in transverse section, stippling in oblique section and a globular arrangement of sub‐units in tangential section. Other studies have shown these junctions to be of low electrical resistance although the functional importance of this characteristic in this situation has not been determined.
The hematopoietic microenvironment of the bone marrow: An ultrastructural study of the stroma in rats
Authors: Weiss Leon 
Published: February 2005

AbstractThe bone marrow contains branching vascular sinuses lying in a fibroblastic stroma which supports hematopoiesis. This paper describes the stroma and vascular sinuses by scanning and transmission electron microscopy and in freeze‐fracture etch replicas in normal rat femoral marrow and in rats made eosinophilic by larvae of trichinella spiralis.The stroma consists primarily of reticular cells which ensheath sinuses as adventitial cells and branch into the surrounding hematopoietic space. They form a spongework on which hematopoietic cells are arranged. Erythroblasts, clustered into islets, and megakaryocytes lie just outside sinuses. Granulocytes, until the metamyelocyte stage, lie in the midst of the hematopoietic cords. Lymphocytes, monocytes and likely stem cells, are clustered about arterial vessels. Macrophages occur throughout the marrow. Fat cells occur adventitial to vascular sinuses and appear to be reticular cells which accumulate fat.Processes of reticular cells closely envelope hematopoietic cells or protrude into them. Reticular cells contain rough ER and are likely fibroblastic. The argyrophilic reticular fibers of the marrow are, however, slender and scanty. Reticular cells are rich in filaments and they may contain many microtubules. They are not phagocytic and possess few lysosomes. The reticular cell cover of a vascular sinus is lifted away as maturing hematopoietic cells approach the sinus, preparatory to crossing the endothelium and entering the circulation. Maturing granulocytes often show microvilli on reaching the basal endothelial surface.The level of eosinophils in the marrow may increase from approximately four to more than 20% after injection of trichinella larvae. Close distinctive association of reticular cells and eosinophils are marked.Reticular cells provide a physical spongework on which hematopoietic cells are supported. But I postulate that they also trap and induce differentiation of hematopoietic stem cells, and sort the differentiating hematopoietic cells into characteristic locations in their spongework.
Distribution of growth hormone‐release‐inhibiting hormone (somatostatin) in the rat brain as observed with immunocytochemistry
Authors: Baker Burton L. , Yu Ya‐Yen 
Published: February 2005

AbstractThe objective was to determine the distribution of growth hormone‐release‐inhibiting hormone (somatostatin) in the rat brain using the peroxidase‐antiperoxidase immunocytochemical method with antisera prepared against unconjugated, synthetic somatostatin. Somatostatin occurred in low quantity in the organum vasculosum of the lamina terminalis. It was present throughout the full length of the median eminence and occupied the entire width between the tuberoinfundibular sulci. Most somatostatin was located in the dorsal portion of the external lamina, and the amount varied according to the mediolateral position. The bodies labeled for somatostatin were most often granules; occasionally they appeared as clusters of granules that seemed to be membrane‐enclosed. Some of these bodies appeared to be portions of axons. Many of the larger bodies were arranged alongside tanycytes, but no label was distributed generally in tanycyte cytoplasm. Somatostatin was highly concentrated in the proximal one‐quarter of the infundibular stem and appeared in lower concentration throughout the distal portion of the stem. It was absent from the pars nervosa and pars intermedia of the pituitary gland. The distribution of somatostatin in the median eminence differed considerably from that of gonadotropinreleasing hormone.Somatostatin was identified in the ventromedial and/or dorsomedial hypothalamic nuclei of only two animals. Here it was probably located in axons that terminated on neuronal cell bodies but also may have been present in a restricted portion of the perikaryonal cytoplasm.