bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arteriovenous anastomoses in the skin of seals. II. The california sea lion Zalophus californianus and the northern fur seal Callorhinus ursinus (Pinnipedia: Otariidae)
Authors: Bryden M. M. , Molyneux G. S. 
Published: February 2005

AbstractThe structure, distribution and density of arteriovenous anas‐tomoses (AVAs) were studied in body and flipper skin of a California sea lion and a northern fur seal. In both animals AVAs consisted of arterial, intermediate and venous segments, and were generally larger and more tortuous in the sea lion than in the fur seal. In the sea lion the majority of AVAs (72%) occurred in the deeper region of the dermis, and the density was significantly greater in the flippers than in the body. In the northern fur seal most AVAs (76%) occurred in the superficial region of the dermis; the density of AVAs in flipper skin was significantly higher than in body skin, and the density in the hind flipper was significantly greater than in the foreflipper.Arteriovenous anastomoses are important in the regulation of body temperature in seals; when these animals are on land, AVAs function to dissipate body heat, and vascular thermoregulation occurs in the flippers but not over the general body surface. Due to differences in distribution and density, AVAs play a more significant role in thermoregulation in the northern fur seal than in the California sea lion.
Morphological and functional differentiation of the surface epithelium of the bursa Fabricii in chicken
Authors: Naukkarinen Anita , Arstila Antti U. , Sorvari Tapani E. 
Published: February 2005

AbstractMorphological and functional differentiation of the mucosal surface epithelium of the bursa Fabricii was studied in White Leghorn chicken fetuses and newly hatched chickens. First signs of differentiation towards two types of epithelial cells appeared on the thirteenth day of incubation: The apical cells of the epithelial buds projected towards the lumen, and an increase in the number of Golgi regions was observed in the epithelial cells between the buds. On day 15 the follicle‐associated epithelium contained small apically situated vacuoles, and large mucin granules appeared in the interfollicular surface epithelium. Towards the day of hatching both epithelial cell types were arranged to a monolayered or pseudostratified cylindrical epithelium. The follicle‐associated epithelium had invaginations and small vacuoles in the apical cytoplasm, whereas the interfollicular surface epithelium had numerous microvilli on its apical surface and large mucin granules in the apical cytoplasm. In functional studies, endocytosis of colloidal carbon was demonstrated in four out of ten 19‐day‐old fetuses and in all chickens studied immediately after hatching.
The mammalian tubuli recti: Ultrastructural study
Authors: Osman D. I. , Plöen L. 
Published: February 2005

AbstractThe ultrastructure of the tubuli recti was studied in the testes of sexually mature bulls, boars, rams, goats, rabbits and rats fixed by vascular perfusion. The tubuli recti are lined with a simple epithelium that varies in height, from squamous to tall columnar according to the species and the region. The cells are characterized by extensive lateral and tortuous basal plasma membranes and a luminal border with microvilli. Tight junctions and desmosomes are found in the upper half of the lateral borders. The Golgi apparatus is sizable and associated with it are coated vesicles and may smooth vesicles concentrated towards the luminal border. A distal segment of the tubuli recti is found in bulls only and is characterized by a high epithelium which is thrown into folds giving the lumen a festooned appearance. It is suggested that the epithelial cells of the tubuli recti are involved in fluid exchange and in the removal of unwanted spermatozoa.
Vasectomy in rhesus monkeys. IV. Electron microscopic studies of the seminiferous epithelium
Authors: Chapman E. S. , Heidger P. M. , Harrison R. M. , Roberts J. A. , Domingue G. J. , Schlegel J. U. 
Published: February 2005

AbstractStudies were undertaken to assess the fine structural effects of vasectomy upon the rhesus monkey testis, using 27 monkeys subjected to one of three surgical techniques: control sham operation (COS), unilateral silk vasoligation (USV), or unilateral clasp vaso‐occlusion (UCV). The monkeys were sacrificed from 1 to 66 weeks after surgery; tissues were fixed in glutaral‐dehyde in collidine buffer and processed for electron microscopy (EM) using routine techniques. No alterations were noted in the seminiferous epithelium of any COS animal; only focal lesions were found in vasectomized animals. These changes correlated with length of time post‐vasectomy, a finding consistent with earlier light microscopic studies (Heidger et al., '78). Even at the longest post‐operative periods studied, spermatogenesis appeared in most animals to be normal. One animal exhibited areas in which the seminiferous epithelium consisted of Sertoli cells and spermatogonia, only. The seminiferous epithelium of approximately one‐third of other animals, both on the vasectomized and contra‐lateral sides, exhibited such alterations as development of extensive infoldings and duplication within the basal lamina, and presence within the basal Sertoli cell cytoplasm of late spermatids and sperm tails. These alterations were observed in both UCV and USV animals. The presence of such late germ cells in the basal Sertoli cell cytoplasm was noted by light microscopy; however, lu‐minal spermiophages encountered in one animal at the light microscopic level were not detected in our EM study, which underscores the limitations of EM as a survey technique. All UCV animals developed spermatic granulomas of the vas, whereas only 3 of 13 USV animals developed such granulomas. It does not appear that the alterations exhibited by the animals in this study would necessarily dispose toward impaired spermatogenesis following vasovasostomy.
Formation of apical pseudopods by canine thyroid follicular cells: Induction by thyrotropin and 5‐hydroxytryptamine; antagonism by reserpine
Authors: Nunez Eladio A. , Gershon Michael D. 
Published: February 2005

AbstractThe role of biogenic amines in the activation of thyroid follicu‐lar cells by thyrotropin (TSH) was studied. 5‐hydroxytryptamine (5‐HT) was chosen as the amine to study and apical pseudopod formation, assessed by scanning electron microscopy, was used as the index of follicular cell activation. All experiments were done on dogs. TSH and 5‐HT were both potent inducers of pseudopod formation. The action of TSH but not that of 5‐HT was antagonized by the amine depleting drug reserpine. Reserpine depleted the thyroid of 5‐HT in newborn, adolescent, and adult dogs. It is concluded that one or more biogenic amines, such as 5‐HT, are probably involved in follicular cell activation by TSH.
Epithelial influences on membrane bone formation in the maxilla of the embryonic chick
Authors: Tyler Mary S. 
Published: February 2005

AbstractIn light of previous evidence that epithelial influences are required for membrane bone formation in certain instances (mandible, Tyler and Hall, '77 a,b; cranium, Benoit and Schowing, '70), the possibility that maxillary epithelium influences membrane bone formation within the maxillary mesenchyme was investigated. Intact maxillary processes, and enzymatically separated epithelial and mesenchymal components of the maxilla were obtained from embryonic chicks of three to five days of incubation (Hamburger and Hamilton ['51] stages (HH) 18‐25) were grown individually as grafts on the chorioallantoic membranes of host chick embryos. The histodifferentiation of grafted intact maxillary processes was similar to that in vivo. The histodifferentiation of grafted maxillary mesenchyme depended upon the embryonic age at which the mesenchyme was isolated from its epithelium. In grafts of maxillary mesenchyme isolated from its epithelium at HH 22 or earlier stages, cartilage differentiated, but membrane bone did not form. In grafts of maxillary mesenchyme isolated from its epithelium at HH 23 or later stages, membrane bone formed in addition to cartilage. The results indicate that maxillary mesenchyme requires the presence of epithelium through HH 22 in order for membrane bone to form within the mesenchyme. Cartilage formation within the mesenchyme does not require epithelial influences during the embryonic period tested (HH 18‐25). Maxillary epithelium isolated from its mesenchyme and grown as a graft became underlaid by host fibroblasts and achieved a limited degree of differentiation; the epithelium did not induce ectopic membrane bone formation within the host tissue, indicating that the presence of maxillary epithelium is not a sufficient condition for promoting membrane bone formation in normally non‐osteogenic tissue.
Filtration of circulating particles by splenic autotransplants
Authors: Dumont Allan E. , Martelli Amalia B. 
Published: February 2005

AbstractTo determine whether filtration in reconstituted perifollicular marginal zones underlies particle sequestration in regenerating spleen transplants, the distribution of IV injected particles of tantalum was examined in autografts freely transplanted into subcutaneous pouches in rats. In two to six weeks old autografts removed one to three hours after particle injection, the reconstituted marginal zones contained practically all of the sequestered tantalum. At 48 hours to‐20 weeks following injection, marginal zones were largely free of particles which were distributed extracellularly throughout the red pulp. This sequential pattern of distribution conformed closely to that observed in the intact spleen.The findings indicate that a reconstituted marginal zone allows splenic autotransplants to function as simple mechanical filters. Increased demand for this activity rather than for phagocytosis may be the predominant factor regulating spleen growth.
Identity of a population of progenitor cells in gingival connective tissue of the mouse incisor
Authors: Everts Vincent , Beertsen Wouter 
Published: February 2005

AbstractIn the gingiva of the mouse incisor, connective tissue cells were observed which were undergoing mitosis and contained collagen fibrils enclosed in vacuoles in their cytoplasm. The presence of intracellular collagen was noted in the majority of the dividing cells. On the basis of this observation it is suggested that renewal of the fibroblast population in the gingiva occurs preferentially by division of differentiated fibroblasts rather than by division of cells with a lower degree of differentiation.
The effects of 5α‐reduced androgens on maintenance and regeneration of prostate glands and seminal vesicles in castrated and hypophysectomized rats
Authors: Ahmad Nazir , Warren Dwight W. , Haltmeyer Gary C. 
Published: February 2005

AbstractThe effects of 5α‐androstane‐3α,17β‐diol (3α‐diol) and 5α‐androstane‐3β, 17β‐diol (3β‐diol) were studied in rats hypophysectomized and treated daily for 30 days with the steroids, starting on the day of surgery (hypophysectomized, H) or 30 days following the removal of pituitary (hypophy‐sectomized regressed, HR). The ability of 3β‐diol to maintain and restimulate the prostate glands and seminal vesicles of castrated (C) and castrated regressed (CR) rats, respectively, was also studied. This androgen (3βdiol) was able to maintain as well as rejuvenate to some degree the sexual accessory glands of all treatment groups. The prostate glands and seminal vesicles in both castrated experimental groups showed increased stimulation with progressively higher dosages of 3β‐diol. At all dose levels, stimulation of seminal vesicles of CR rats was comparable to that of non‐regressed castrates. The prostate glands, on the other hand, showed better maintenance in the higher dosage group. In H rats, the stimulation of sexual accessory glands by both androgens was not significantly different than normal controls. The seminal vesicles and prostate glands of HR rats treated with 3α‐diol were well stimulated and comparable to those of H rats treated with 3α‐diol. The seminal vesicles of HR rats treated with 3β‐diol were also well stimulated, though not to the extent as those with 3α‐diol treatment. The prostate glands of the 3β‐diol treated HR rats were significantly smaller than those of the 3α‐diol treatment group. However, these miniature glands were morphologically stimulated as evidenced by mitosis of parenchymal cells and accumulation of secretory products in the alveoli. This study clearly indicates that 3β‐diol is biologically active and the degree of stimulation varies with the animal preparation in which the andro‐gens were tested.
Effects of testosterone enanthate on the structure of the male reproductive tract of the rat
Authors: Flickinger Charles J. 
Published: February 2005

AbstractThe histology and fine structure of the testis, epididymis and sex accessory glands were studied in young adult male rats administered testosterone enanthate, 120 μg/100 g body weight, three times weekly for 4, 8, or 12 weeks. The weights of the testis and epididymis decreased, and animals treated for 11 weeks were infertile. Alterations were found in the seminiferous tubules of all rats treated for 8 or 12 weeks, including the presence of many degenerating germ cells and a‐large decrease or absence of late spermatids. Study of different stages of the cycle of the seminiferous epithelium showed that the greatest number of degenerating germ cells, step 7 spermatids and pachytene primary spermatocytes, occurred at stages VII‐VIII of the cycle. Some normal appearing spermatogonia, primary spermatocytes and early spermatids remained in most seminiferous tubules. Sertoli cells contained many lipid droplets and lysosome‐like bodies, and degenerating cells were surrounded by Ser‐toli cell cytoplasm. The Leydig cells of treated animals were greatly reduced in size. Sperm progressively disappeared from the lumen of the middle segment and proximal part of the terminal segment of the epididymis after treatment for 8 or 12 weeks. Changes in the middle segment also included the appearance of intraepithelial cavities containing debris, and the presence within the epithelium of phagocytic cells that resembled leukocytes. The lumen of the proximal part of the terminal segment was often collapsed, while in the distal part of the terminal segment, the lumen was filled with cellular debris and degenerating sperm. Organelles of the principal cells of the epididymal epithelium appeared to be qualitatively unaltered. The weight of the sex accessory glands remained close to normal, and the presence of normal ultrastructural features suggested that production of secretions continued.
Linear arrays of intramembrane particles on microvilli in primate large intestine
Authors: Neutra Marian R. 
Published: February 2005

AbstractDistinctive linear arrays of intramembrane particles were present in microvillar membranes of approximately 5% of surface columnar cells observed in freeze‐fracture replicas of monkey colon and human rectum. On these cells, longitudinally‐oriented rows of P face particles and corresponding E face grooves appeared on all exposed microvilli. The constituent particles varied from round (8‐9 nm in diameter) to rod‐shaped (18 nm long). Microvilli of the great majority of columnar cells displayed randomly distributed P face particles similar to those previously observed in small and large intestine of birds and small mammals. The significance of the linear arrays is not known. It is postulated that they may represent protein assemblies which are specific to a functionally‐distinct subpopulation of primate intestinal columnar cells.
Histochemical characteristics of the masseter and temporalis muscles of the rhesus monkey (Macaca mulatta)
Authors: Maxwell Leo C. , Carlson David S. , McNamara James A. , Faulkner John A. 
Published: February 2005

AbstractThe histochemical characteristics, cross‐sectional area and capillary of the skeletal muscle fibers of the anterior and posterior regions of the superficial masseter and the temporalis muscles are described for juvnile and adult rhesus monkeys of both sexes. Slow twitch fatigue resistant (S), fast twitch fatigue resistant (FR) and fast twitch fatigable (FF) fibers were found in varying proportions throughout the muscles; however some fibers with an intermediate myofibrillar ATPase activity were observed in the anterior masseter. No significant differences for any of the variables were found between male and female juveniles for a specific muscle sample site. However, consideable variation was found between juvenile and adult and between adult male and female monkeys in the percentages of different fiber types and the cross‐sectional area of fibers in specific regions of the superficial masseter and temporalis muscles. We conclude from these observations that significant differences in funtion exist both within and between the different masticatory muscles of rhesus monkeys. Functional differences may result from the pronounced sexual dimorphism evident in the dentofacial complex of rhesusmonkey.
The distribution of alkaline phosphatase activity in normal and cross‐species regenerated rat and mouse taste buds
Authors: Zalewski Andrew A. 
Published: February 2005

AbstractAlkaline phosphatase (ALK Pase) activity can be detected histochemically in the taste buds of rats but not mice. Since taste buds develop, regenerate and are maintained under the influence(s) of the sensory nerve it was decided to study cross‐species regenerated buds of these two animals to determine whether the nerve also regulated ALK Pase development in taste cells. Grafts of rat sensory ganglion and mouse tongue or mouse ganglion and rat tongue were combined in the anterior chamber of the eyes of immunologically‐deficient nude mice and the cross‐species buds that developed at 35 days were examined histochemically for ALK Pase. The results revealed that the rat nerve did not cause ALK Pase to appear in any buds found in mouse tongue grafts and that mouse nerve could support buds containing ALK Pase in rat tongue tissue. Because the cross‐species regenerated buds were histochemically characteristic of those normally found in rat or mouse tongue, there is no evidence that the foreign nerve altered gene expression for ALK Pase in the target organ, and the action of the nerve on gustatory epithelium appears to be that of activation and maintenance.
Chromatin substructure: An electron microscopic study of thin‐sectioned chromatin subjected to sequential protein extraction and water swelling procedures
Authors: Cameron Ivan L. , Pavlat William A. , Jeter James R. 
Published: February 2005

AbstractElectron microscopic observations and measurements were made on thin‐sectioned chromatin fibers and fibrils obtained from nuclei of mature chicken erythrocytes. The nuclei were isolated in low ionic strength gum arabic and octanol then extracted sequentially with (1) 0.14M NaCl, (2) 0.25 N HCl, (3) buffer saturated phenol, (4) hot 5% SDS and 0.14 M 2‐mercapto‐ethanol and, (5) 0.4 N NaOH. The amount of nuclear protein removed at each of the first four extraction steps was 1, 86, 3 and 11% of the total, respectively. Each extract was characterized by electrophoretic profiles. At each extraction the chromatin was fixed by adding large quantities of a mixture of equal volumes of sodium cacodylate buffered 8% (w/v) glutaraldehyde (pH 6.8) and 2% OsO4 (w/v), directly into (1) an aliquot of the chromatin in extraction fluid, and (2) an aliquot of the chromatin after water washing and swelling. Three size classes of chromatin structure were seen in thin sections prepared for high resolution transmission electron microscopy and stained with uranyl acetate and lead citrate. A thick fiber of about 25 + nm diameter was the predominant large fiber seen in freshly isolated nuclei or in nuclei after salt extraction. This 25 + nm fiber has a substructure consisting of 3.2‐5.2 nm diameter fibrils. After water swelling of such freshly isolated or salt extracted nuclei a fiber of about 10 nm diameter was the predominant large fiber instead of the 25 nm diameter fiber. The HCl extraction step which is known to remove histones, caused the disappearance of both the 25 nm and the 10 nm fibers. High magnification (600,000 × ) micrographs of the chromatin at all procedural steps, except the last NaOH step, reveal the fibril to be omnipresent. This fibril tends to decrease somewhat in diameter during the protein extraction steps to a 2.5 nm diameter fibril after the hot SDS extraction. A fibril of 2.5 nm diameter is expected of naked double helical DNA stained with a positive stain. The NaOH, which is known to denature DNA, completely destroyed the remaining fibril. We interpret our results to indicate that the larger chromatin fiber seen in micrographs of thin‐sectioned chromatin has a fibrillar substructure which probably represents a double coil of native DNA which may have a thin protein coating of its own. The latter fibril may in turn be wrapped around a hydrophobic histone domain, perhaps reflected in the 10 nm diameter fiber which is seen upon swelling of the chromatin. This 10 nm diameter fiber is thought to be further packaged by folding into the 25 + nm diameter chromatin fiber most frequently reported in thin sections of eukaryotic cell nuclei in situ.
Resorption of connective tissue in the gingiva of the mouse incisor
Authors: Schellens J. P. M. , Everts V. , Beertsen W. 
Published: February 2005

AbstractDuring eruption of the mouse incisor part of the periodontal ligament moves along with the tooth in occlusal direction and is degraded in the gingiva, just apically of the junctional epithelium. When studied with the electron microscope some connective tissue cells (fibroblasts) showed disorganization of both nucleus and cytoplasm. In other cells vacuoles were observed containing partly degraded cellular constituents. Sometimes within these vacuoles electron dense material with the appearance of clumped chromatin was observed. On the basis of this observation it is concluded that heterophagocytosis contributes to the process of fibroblast breakdown. The ultrastructure of these heterophagic cells resembled that of fibroblasts.Collagenous fibrils were observed within cytoplasmic vacuoles of fibroblasts indicating that collagen is phagocytosed and probably digested in the lysosomal apparatus. Part of the intercellularspace was filled with a homogeneous material of moderate electron density, intermingled with some collagenous fibrils.Within some cells of the junctional epithelium partly degraded material was observed which may indicate that the epithelium contributes to the removal of residual products of connective tissue degradation.