bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of drugs on pituitary fine structure in laboratory animals
Authors: Stefaneanu Lucia , Kovacs Kalman 
Published: February 2005

AbstractAlthough an increasing number of chemicals are reported to affect endocrine glands, only a few studies are dealing with their toxic effect on pituitary. The drugs can induce lesions acting directly on endocrine cells or indirectly by interfering with the regulation of their endocrine activities. Some drugs stimulate pituitary cell proliferation leading to hyperplasia and tumor formation; other chemicals have an inhibitory effect on adenohypophysial cells; and only one drug, hexadimethrine bromide, has been found to induce pituitary necrosis.Although complex toxicologic studies have been carried out on many chemicals, the mechanism of action of most drugs is not completely elucidated and further studies are necessary to establish structure function correlations.
Preparation of (InGa)As/GaAs materials for TEM by one side non‐rotation ion beam thinning
Authors: Yao J. Y. , Dunlop G. L. 
Published: February 2005

AbstractA technique is described for the preparation of thin specimens for transmission electron microscopy (TEM) of (InGa)As/GaAs multilayered materials. In this technique, a shielding method is used for selective‐area perforation by ion beam thinning. Thin cross‐sectional specimen slices are mechanically pre‐thinned to about 30 μm and then thinned by ion sputtering from one side of the specimen at a time without rotation of the specimen stage. No direct ion sputtering occurs at the growth surface of the specimen so that a specimen with thin areas containing the desired near‐surface structures can be obtained. The recipe for this technique is given in detail. A patterning method for increasing the size of the thin area for TEM investigation is also described. It is shown that a smooth surface can be obtained by sputtering without rotating the stage if obstacles that produce redeposits onto the sputtered surface are removed.
Testicular differentiation in mammals under normal and experimental conditions
Authors: Merchant‐Larios Horacio , Taketo Teruko 
Published: February 2005

AbstractGonadal differentiation begins with the establishment of a sexually undifferentiated gonad, in which gonadal cords are formed by condensation of somatic cells and deposition of basal laminar components around the cluster of epithelial‐like cells. The first event of sexual differentiation is the invasion of mesenchymal and endothelial cells into the genital ridge in the XY gonad. As a consequence of this event, the gonadal cords become conspicuous, recognized as seminiferous cords (or testis cords). Cytological differentiation of Sertoli cells follows these stromal changes. In the XX gonad, by contrast, the invasion of the mesenchyme is absent and gonadal cords remain associated with the surface epithelium. In the B6.YDOM XY ovotestis, seminiferous cords and ovarian gonadal cords are often enveloped by common basal laminae, confirming that both structures share the embryonic origin. It has been recently reported that seminiferous‐like cords are formed after loss of oocytes in the rat XX ovary cultured in the presence of Müllerian inhibiting substance or after long‐term culture in the basic medium alone. These results are comparable with our observation on the persistent gonadal cords in the ovary of busulphan‐treated rats or W/WV mutant mice, in which oogonia are absent or scarce. Ultrastructural evidence for Sertoli cell differentiation from XX cells has been presented, so far, only in the fetal mouse ovary that has been grafted beneath the kidney capsule of adult male mice. Possible mechanism of gonadal sex determination is discussed based on these morphological studies.
Sertoli cells and testicular differentiation in the rat fetus
Authors: Magre Solange , Jost Alfred 
Published: February 2005

AbstractThe fetal testis is not merely a precursor of the adult organ: it is indeed an endocrine gland whose function is the masculinization of the fetus. It differs physiologically and morphologically from the adult testis. In this paper, the first stages of testicular differentiation in the rat are described, with special emphasis on the ultrastructural aspects. At the stage of 13.5 days after fertilization, the first Sertoli cells differentiate; they are characterized by a voluminous and little electron dense cytoplasm, a well‐developed RER formed by vesicles and short cisternae filled with a flocculent material. Progressively, they polarize and adhere to one another by adherens‐like junctions and cytoplasmic interdigitations to form the differentiating seminiferous cords. In the basal part of the Sertoli cells, a mat of microfilaments differentiates under the plasmalemma, while cytoplasmic blebs protruding in the extracellular space tend to disappear. A continuous basal lamina delineating the seminiferous cords begins to appear on day 14.5 and becomes widespread on day 15.5. These observations, when compared with other data from the literature, emphasize the fact that the differentiation of the Sertoli cells is the first morphological event during testicular differentiation. A possible role of the Sertoli cells in the subsequent organogenesis of the testis is suggested.
High‐Resolution scanning electron micrographs of freeze‐cracked cells in testes from normal and irradiated rats at different stages of gonadal development
Authors: Burdzy Krystyna , Tung Pierre S. , Fritz Irving B. 
Published: February 2005

AbstractNewly developed techniques in high‐resolution scanning electron microscopy (SEM) and for tissue‐processing procedures have been applied to an investigation of structures of various cells in rat testes at different stages of gonadal maturation. A series of high‐resolution SEM micrographs are presented which survey the surfaces of different types of testis cells during normal development, and which also illustrate ultrastructural features of some of their intracellular organelles. In addition, a series of high‐resolution SEM micrographs are presented which compare the structural features of Sertoli cells in normal testes with those in germ‐cell‐depleted testes obtained from rats killed at varying times after having been irradiated in utero. We describe our observations on the structural properties of surfaces and intracellular organelles in Sertoli cells, Leydig cells, peritubular myoid cells, and some classes of germinal cells. We also consider the possible role of Sertoli cell apical cytoplasmic processes in lumen formation. Similarities are pointed out between the structure of germ‐cell‐depleted testes, resulting from irradiation in utero, and the structure of germ‐cell‐depleted testes in seasonal breeders during periods of involution. Finally, we discuss advantages and disadvantages of methods employed to reveal the fine structure of intracellular organelles in cells of the testis.
Formation of a functional endothelium on vascular grafts
Authors: Williams Stuart K. , Schneider Timothy , Kapelan Barbara , Jarrell Bruce E. 
Published: February 2005

AbstractThe lack of a functional endothelial cell lining on artificial polymeric vascular grafts severely reduces their effectiveness in replacing small caliber (< 6 mm) blood vessels. Techniques have now been developed to transplant autologous endothelial cells from one site in the body onto the surface of grafts prior to implantation. Pre‐clinical animal trials provide evidence that grafts sodded with autologous, fat‐derived, microvessel endothelial cells exhibit a stable, antithrombogenic lining of endothelium. The new endothelial cell lining exhibits morphologies identical with endothelium on native blood vessels. The effectiveness of endothelial cell sodding techniques in pre‐clinical animal trials provides support for expanded clinical trials.
Cross‐sectional transmission electron microscopy of x‐ray multilayer thin film structures
Authors: Nguyen Tai D. , Gronsky Ronald , Kortright Jeffrey B. 
Published: February 2005

AbstractA simple method for preparing cross‐sectional transmission electron microscopy specimens and discussions of possible artifacts from specimen preparation and observation of x‐ray multilayer thin film structures are presented. The specimen preparation method employs mechanical grinding and polishing to approximately 20 μm, followed by ion milling, without dimpling. Artifacts such as preferential ion milling and crystallization under the electron beam, as well as effects of Fresnel fringes at interfaces, are important factors in interpretation of the images. Care in identifying them is required to avoid erroneous results in studies of morphology and microstructures within the layers and at their interfaces. Example high‐resolution TEM results of cross‐sectional W/C, Ru/C, and Mo/Si multilayers are presented.
An alkali digestion method to expose connective tissue fibers: A scanning electron microscopy study of rat lung
Authors: O'Donnell M. D. , McGeeney K. F. 
Published: February 2005

AbstractAlkali digestion has been used to remove cellular elements of tissues thus exposing the underlying connective tissue framework. We studied the action of this severe alkali treatment on the delicate tissues of rat lung. The lungs of male Sprague‐Dawley rats were perfused with saline to remove blood and then inflated by fixation through the airways at 20 cm pressure. Sections of lung 2 × 5 × 5 mm were immersed in 2.5 M NaOH at 25°C for 6 h, 16 h, 24 h, 48 h, and 72 h. The alkali was changed daily. Tissues were washed to neutral with water (24 h), treated with tannic acid (1%, 3h), post‐fixed with osmic acid (1%, 3 h) and processed for SEM. At 6 h, epithelial cells started to peel off the alveolar surface. At 16 h the digestion process was well advanced. At 48 h the cells were completely removed revealing the lattice network of connective tissue fibers within the alveolar surface. The method allows the complete removal of cellular elements of the lung while retaining the very fine 3D structure of the connective tissue matrix.
Clasmatosis of skin mast cells as affected by moccasin venom
Authors: Zahl Paul A. , Nowak Andrew 
Published: February 2005

AbstractMoccasin venom injected intradermally into mouse skin induces an almost immediate clasmatosis of mast cells, followed by dissolution or loss of staining reaction of the released granules, a condition from which there is no observable recovery for at least 25 days. The possible significance of this reaction is discussed.
An autoradiographic study of RNA synthesis in isolated salivary glands of Drosophila hydei. I. Autoradiographic studies
Authors: Arnold Gail 
Published: February 2005

AbstractRNA synthesis in isolated Drosophila salivary glands was studied by autoradiography. The dry mass of cellular structures was determined by interference microscopy; a correction which compensates for self‐absorption of β‐particles, and consequent lowered grain counts, is discussed. The correction factors are 12.0 for nucleolus, 5.0 for nucleoplasm and 8.8 for cytoplasm.After 15 seconds in uridine‐H3, label was localized over the nucleolus; after one minute, nucleoplasm RNA became labeled also. In situ synthesis of some nucleolar RNA is indicated.Comparisons of uridine‐H3 and cytidine‐H3 incorporation were made in glands exposed briefly to isotope, followed by transfer to unlabeled nucleoside solutions. The data suggest two RNA fractions in nucleoli. Rapid turnover and higher uridine incorporation characterized one fraction, which resembled RNA of nucleoplasm metabolically. The second nucleolar RNA incorporated less uridine, remained longer in the nucleolus, and resembled cytoplasmic RNA in precursor incorporation pattern.Preincubation in Actinomycin D before uridine‐H3 labeling resulted in 80% inhibition of RNA synthesis in both nucleolus and nucleoplasm. Longer isotope exposures produced some increase in labeling. Actinomycin treatment delayed appearance of label in cytoplasmic RNA.After HCl extraction of uridine‐H3‐labeled RNA, some activity, presumed to be incorporated in DNA, remained. This non‐extractable label appeared earliest over nucleoli, and subsequently over chromatin. Actinomycin treatment abolished incorporation of non‐extractable label into nucleoli.
Histochemistry of the developing chick esophagus and trachea. I. Alkaline phosphatase
Authors: Hinsch Gertrude W. , Buxbaum Susan K. 
Published: February 2005

AbstractTissues of White Leghorn embryos of stages 17–45, and chicks of one day, two days, and three weeks of age were frozen or fixed in 85% ethanol. Alkaline phosphatase was identified using the azo‐dye or Gomori techniques.Alkaline phosphatase activity is found in the ventral mesenchyme of the esophagus surrounding the epithelium to stage 34. At stage 38 activity appears in the basal layers of the epithelium and is subsequently lost in the mesenchymal tissues. This activity persists in the epithelium throughout development and following hatching. At 16 days the mucous glands arise as solid buds of epithelium projecting into the tunica propria. These buds are highly positive for alkaline phosphatase. As differentiation of the glands becomes complete they and their ducts lose their positive phosphatase reaction.On the fourth day of development the trachea is found lying ventral to the esophagus. Mesenchyme has condensed around the tracheal epithelium by the fifth day, at stage 37 (11 days) the first cartilaginous rings appear, and by stage 38 (12 days) all are completely formed. During the third week of development the trachea increases in size. Pseudo‐stratified columnar ciliated epithelium begins to appear at 15 days. Alkaline phosphatase is highly reactive in the mesenchyme surrounding the epithelium prior to cartilage formation. After the cartilages have formed the reaction diminishes and in late stages of development phosphatase is found only in the epithelium.
Development of intracranial arterial patterns in turtles
Authors: Burda Doris J. 
Published: February 2005

AbstractObservations on chelonian intracranial arteries are based primarily on the adult condition in Pseudemys scripta and on a series of Chrysemys marginata embryos. Those vessels which show major modifications are the anterior cerebral, posterior cerebral, cerebellar, and internal auditory arteries. The distal portion of the embryonic anterior cerebral is acquired by more medial vessels; from the proximal portion develops the middle cerebral which becomes the major source of supply for the lateral surface of the adult cerebral hemisphere. The posterior cerebral appears early in development and eventually supplies branches to the epiphysis, posterior portions of the hemisphere, olfactory regions, anterior face of the optic lobe, and choroid plexus of the third and lateral ventricles. The cerebellar and internal auditory arteries show similarities in development, each initially supplying the area immediately surrounding a nerve root and then acquiring larger areas of distribution by means of anastomoses with nearby medullary vessels.
Chick cephalogenesis. The normal development of the cephalic region of stages 3 through 11 chick embryos
Authors: Hillman Nina W. , Hillman Ralph 
Published: February 2005

AbstractThe cephalogenesis of chick embryos was studied at stages 3 through 11 inclusive. Ten embryos were examined at each stage. Particular attention was paid to the time of appearance of the prechordal plate mesoderm and cephalic notochord. It was found that the presumptive neural ectoderm begins to differentiate to form medullary plate as soon as it becomes associated with the chordamesoderm. Histological studies revealed the similarity of the notochord underlying the presumptive forebrain and midbrain regions, and the differences between this notochord and that associated with the hindbrain. These differences included the notochord histology and time of separation of the notochord from entoderm and neural ectoderm.
The phenomena of amphibian metamorphosis. IV. The development of the median eminence
Authors: Etkin William 
Published: February 2005

AbstractThe development of the median eminence of several species of American anurans was studied in correlation with the progress of metamorphosis. Before metamorphosis the hypothalamic arteries break up into a plexus of capillaries lying in the extensive area of contact between the anterior lobe and the floor of the hypothalamus. During prometamorphosis the neural tissue of this area is converted into the median eminence. The neural tissue becomes thicker and shorter as the capillaries on its surface sink inward. The anterior lobe separates from the neural tissue except at its anterior tip where the residual capillaries have enlarged to form the pituitary portal veins. These changes are largely but not completely accomplished by the be‐ beginning of metamorphic climax. No significant alterations were found in the neurosecretory cells or their fibers during metamorphosis. The morphological data are interpreted in terms of the changing level of activity of the pituitary‐ thyroid axis during metamorphosis and its dependence upon a thyrotropin‐ releasing factor from the brain.
A reinvestigation of the segmentation of the crayfish abdomen and thorax, based on a study of the deep flexor muscles and their relation to the skeleton and innervation. I. The skeleton and intersegmental membranes
Authors: Rayner M. D. 
Published: February 2005

AbstractRecent physiological studies on the crayfish Procambarus clarki (Girard), Astacura, Decapoda, have suggested the existence of certain anomalies between the classical interpretation of the segmentation of the crayfish and the more recently established segmental innervation patterns. An extensive reinvestigation of the skeletal segmentation has been undertaken, based on the dissection of both fresh and fixed specimens of this and two other crayfish species, to decide to what extent misinterpretation of the skeletal structure might provide an explanation of these apparent anomalies.As a result of this attempt to provide a self‐ consistent analysis of the crayfish skeleton, it has been necessary to conclude that the epimeral plate is tergal rather than pleural in origin, that the basal segment of the thoracic legs contains a subcoxal element, that this subcoxa exists as a free leg segment in the last thoracic legs and that the abdominal pleural folds are in part homologous with the subcoxae of the thorax. On the other hand it has not been necessary to diverge from the classical account of the segmentation, except to recognize the existence of a seventh abdominal segment (segment XXI) posterior to the uropod segment.
The lymphatic system of Dasypus novemcinctus and Dasypus sexcinctus
Authors: Azzali Giacomo , Didio Liberato J. A. 
Published: February 2005

AbstractThe lymphatic system of 40 specimens of Dasypus novemcinctus and 5 of Dasypus sexcinctus, both found in Brazil, were injected with Prussian blue suspension, neoprene latex (followed by partial corrosion). Lymphangioradiographic study was also made. The data concern the lymph nodes, the lymphatic networks, vessels and main trunks. The main features are the following: a few lymph nodes were missing (popliteal, subpubic and ischial); the superficial jugular ll.nn. predominate on the deep ones; the dorsal mediastinal ll.nn. are well developed; a mesentericocolic plexus is formed by the many anastomoses among the mesenteric and cecocolic ll.nn.; at regular intervals there is a concentration of vessels in the submucous network of the small intestine; the submucous network of the colon shows parallel lamellar lymphatic vessels; the mucous‐submucous networks are usually independent from the subserous‐muscular ones; there are two types of lymphatic networks alternating along the duodenum; folliculi lymphatici aggregati are absent; the lymphatic vessels run in the mesentery independently from the blood vessels; the mesenteric lymphatic vessels present many valves; the vessels from the diaphragm terminate directly in the cisterna chyli; there is a multipolarity of the abdominal lymphatic circulation, i.e., each organ has its own lymphatic tr.
The poison gland of the cottonmouth moccasin, Ancistrodon P. piscivorus, as observed with the electron microscope
Authors: Odor D. Louise 
Published: February 2005

AbstractThe structure of the poison gland of the cottonmouth moccasin has been studied with the electron microscope. This gland is divided functionally and structurally into a posterior and an anterior portion. In the posterior gland the columnar principal cells are considered to be responsible for the production of the secretory material, including the toxic substances in the venom. This cell is characterized by numerous dilated membrane pairs of the granular endoplasmic reticulum and by a large Golgi complex. Four other types of cells are observed within the epithelial layer of the posterior part of the gland, but their function is unknown.The majority of the cells of the anterior part of the gland are mucous‐secreting goblet cells. Some possible stages in their secretory cycle are described. Granular endoplasmic reticulum is present in the basal areas of the cell. The accumulation of recognizable secretory material appears first in structures considered to be a part of the Golgi complex.
Nerves and muscles of the pregenital abdominal segments of the American cockroach, Periplaneta americana (L.)
Authors: Shankland D. L. 
Published: February 2005

AbstractThe muscles and motor and sensory nerves of the pregenital abdominal segments were described and discussed in relation to the nerves and muscles of the thorax, as described by other workers. Each of the integumental muscles was named and described with regard to its location, function and innervation. Differences among segments of the same sex and between sexes were noted.A description of a longitudinal muscle, named here the hyperneural muscle, was included. The muscle overlies the abdominal portion of the nerve cord and may be derived from the ventral diaphragm. The most notable features of its structure are chiasmata of fibers which occur at points along its length and which show consistent relationships to the nerve cord and median nerve.A previously undescribed organ, located ventrally at the intersegmental fold, having dual innervation and showing stretch receptor function was described.
The development of the ovary of the sea lamprey (Petromyzon marinus L.)
Authors: Lewis J. C. , McMillan D. B. 
Published: February 2005

AbstractThis investigation is a histological study of the development of the ovary of the sea lamprey from south‐western Ontario, Canada. Development is described from the first appearance of primordial oögonia at the site of the ovary up to ovulation. After mitotic proliferation, oögonia enter meiotic prophase and become oöcytes which enlarge and acquire basophilic cytoplasm.During metamorphosis all oöcytes are at a uniform stage of development and no oögonia remain in the ovary.The follicular layer in the early adult produces nurse cells which are incorporated into the oöcyte and increase its mass of RNA‐rich cytoplasm. As the oöcyte enlarges, proteid yolk platelets are laid down in the cytoplasm. Vacuolation of the nucleolus, indicative of protein synthesis, is extensive during period of rapid growth and yolk formation.Immediately prior to spawning there is an accumulation of fluid under the follicular layer and the oöcyte emerges through a mound of follicular cells.Atresia of oöcytes occurs throughout the adult stages and following spawning. It is characterized by an enzymic dissolution of the yolk followed by phagocytic invasion. The phagocytes arise from the follicle in the early adult stages and from an unidentified source in the spawning‐phase adult.