bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrastructural features of the shark brain
Authors: Long Don M. , Bodenheimer Thomas S. , Hartmann J. Francis , Klatzo Igor 
Published: February 2005

AbstractThe ultrastructural characteristics of elasmobranch central nervous system have not been previously reported. This study presents a general assessment of aldehyde perfused brain and spinal cord in three species of shark: tiger, hammerhead and Atlantic nurse. The same distinct cell types are present in the shark that exist in mammals and similar criteria may be used for their differentiation. Neurons have frequently round nuclei with a prominent nucleoli; cytoplasm is abundant and filled with formed elements; somatic synapses and subsurface cisterns are rare. Astrocytes are smaller, and have less cytoplasm and slightly fewer organelles. Glial fibrils occur, but are not invariably present. Separating astrocytes from neurons is the most difficult identification problem. Oligodendrogliocytes are smaller, and have denser cytoplasm and a dark nucleus. The striking feature of capillary morphology is the presence of an appreciable perivascular space containing collagen; many tortuous evanginations of this space occur into surrounding glial processes which completely invest the capillaries. Astrocyte cell bodies frequently lie immediately next to vessels, and capillaries are occasionally totally surrounded by a single astrocyte process, thus being endocellular. Smaller pericapillary processes may be either astrocytic or ependymal. Dendrites, synapses, axons, and myelin have no obvious special characteristics. Sodium, visualized by precipitation techniques, is prominent in the astroglia and neurons.
Subcommissural organ and adjacent ependyma: Autoradiographic study of their origin in the mouse brain
Authors: Rakic Pasko , Sidman Richard L. 
Published: February 2005

AbstractMorphogenesis and time and place of cell origin of the subcommissural organ and adjacent ependyma in the mouse brain was investigated by light microscopy and autoradiography. Pregnant mice were injected systematically at different stages of gestation and their offspring killed after various periods. Cells of the subcommissural organ arise (undergo final replication of nuclear DNA) from embryonic days 11 to 15 at the diencephalomesencephalic junction in close association with the primordial fibers of the posterior commissure. The ependymal cells of the caudal part of the third ventricle first arise at approximately the same embryonic stage as the subcommissural cells and continue to proliferate through embryonic day 18.The subcommissural organ is suitable for semiquantitative analysis because its cells are of one type, their number is small, they arise over a short time span and once formed, they persist indefinitely. Some cells exposed to thymidine‐H3 in utero at the time of final DNA replication were strongly labeled at adulthood, as expected, but others were weakly labeled. Calculations suggested that significant numbers of these weakly labeled cells should be assigned to the nondividing class i.e., had their birthdays on the day of thymidine‐H3 injection. Errors are introduced if the usual practice is followed of assigning birthdays on the basis of the heavily labeled population exclusively.
The fine structure of the adrenal cortex of the 13‐lined ground squirrel
Authors: Seliger William G. , Smith Wayne F. 
Published: February 2005

AbstractThe adrenal cortex of the 13‐lined ground squirrel was examined by means of phase contrast and electron microscopy. At the most, two cell types were observed. One of these two types was observed in three morphologically different stages of activity. They had some common characteristics, although they were very different in general appearance. The findings substantiate Symington's (′60, ′61) statements that the zona reticularis contains the active cells and the zona fasciculata contains the inactive cells of the deep adrenal cortex. The cell types do not stay within the bounds of the three classical zones, and it is suggested these be used for general topography only. A number of modifications and derivations of mitochondria are described, one of which lends strength to Lever's ('55) suggestion that mitochondria might be converted into lipoidal masses.
The innervation of the bone marrow in laboratory animals
Authors: Calvo Wenceslao 
Published: February 2005

AbstractThe nerve pattern of the bone marrow of the monkey, rabbit, rat and mouse was studied in serial sections specially stained to demonstrate myelinated and nonmyelinated nerve fibers. Features that are common to the different species studied were found in the bone marrow of the femur of the rat in a simple arrangement.A scheme is proposed based on thirteen photomicrographs demonstrating the nerve pattern of the bone marrow and the relation of the nerve fibers with the arterial tree, the sinusoids and the blood forming cells. This scheme shows that the necessary anatomical conditions exist permitting a direct influence of the nervous system on the function of the bone marrow. These conditions are the presence of myelinated nerve fibers traversing the parenchyma of the marrow, and the existence of nonmyelinated fibers ending in sphincterlike structures at the origin of the arterioles.Single myelinated nerve fibers and small bundles of both myelinated and nonmyelinated fibers lie in close contact with the endothelial wall of the sinuses during long trajects. Only the very thin endothelium of the sinuses separates the newly formed blood and the nerve fibers. An interaction between both elements is possible along these areas of contact.
The fine structure of uterine smooth muscle of the rat uterus at various time intervals following a single injection of estrogen
Authors: Bo Walter J. , Odor D. Louise , Rothrock Martha 
Published: February 2005

AbstractThe fine structure of smooth muscle cells of the rat uterus was studied at 6, 12, 24, 48, 72 and 96 hours after a single subcutaneous injection of estradiol dipropionate (10 μg). The control rats were ovariectomized, but did not receive hormone treatment. Changes in the ultrastructure of the muscle cells occurred soon after estrogen stimulation. An increase in the number of ribosomes on the outer nuclear membrane and evagination of the membrane into the surrounding cytoplasm was noted at six hours. The amount and dilatation of the granular endoplasmic reticulum (GER) increased gradually from 6 to 96 hours. At 24 and 48 hours the mitochondria appeared to increase in number and at later time intervals they increased in size. The Golgi complex was more prominent at 72 and 96 hours than at the earlier time intervals. An increase in free ribosomes was observed at 6 and 12 hours, but a marked accumulation of them occurred at 24 hours and continued to 96 hours. The glycogen granules were very pronounced at 24 and 48 hours with a reduction at 72 and 96 hours. Many pinocytotic vesicles and dense bodies were present in the controls and at 6 and 12 hours. A decrease in number occurred in both at the later time intervals. Organelles accumulated at the nuclear poles beginning at 24 hours and extending to 96 hours. The observations made provide additional information on the fine structure of uterine smooth muscle cells following estrogen stimulation and support previous biochemical studies on glycogen concentration and RNA synthesis in the rat uterus.
The fetal membranes of Pedetes capensis, and their taxonomic significance
Authors: Fischer Theodore V. , Mossman H. W. 
Published: February 2005

AbstractImplantation in Pedetes capensis is superficial and antimesometrial with the embryonic disc mesometrially oriented. As the blastocyst expands, the embryonic pole trophoblast proliferates and penetrates the epithelium at the mesometrial side to establish a massive trophospongial preplacenta. Maternal blood lacunae form in this, and a preplacental maternal circulation is soon established. Amniogenesis is by folding. A choriovitelline placenta develops on the preplacental surface. Yolk sac inversion is late. The bilaminar omphalopleure is permanent. Syntrophoblastic tongues penetrate the preplacenta and surround maternal spaces lined with an attenuated trophospongial cell layer, thus providing a hemodichorial barrier when the vascular allantoic mesoderm invades these tongues to form the lobular labyrinth. A typical countercurrent bloodflow occurs. A small allantoic diverticulum persists to term. Several fetal membrane characters, known to be evolutionarily “conservative,” are alike in Pedetes and the more primitive sciuromorphs. These are the type of implantation, amniogenesis, yolk sac inversion, and allantois. The massive trophospongial preplacenta (Träger) suggests affinity with the Myomorpha and Hystricomorpha, but this is a highly variable character within the Rodentia. Therefore, it is concluded that on the basis of the fetal membranes the Pedetidae are somewhat specialized sciuromorphs.
Observations on calvarial growth in rachitic and healing rats
Authors: De Angelis Vincent 
Published: February 2005

AbstractThe histology of the rachitic and healing sutures, ectocranial and endocranial surfaces of the rat calvarium is described in this paper. Osteoid margins were evident on all surfaces observed at seven days in rachitic rats and were seen to increase in equal amounts on either side of the sutures as the disease process continues, while the osteoid accretion on the ectocranial and endocranial surface revealed differential growth rates throughout the experimental period. The pattern of osteoid deposition is suggestive of a process of calvarial reshaping from the younger animals to the older ones. The marrow spaces were gradually occluded by the osteoid deposition on their margins.On induction of healing by vitamin D, the osteoid was calcified and then differentially resorbed by osteoclasis. The first osteoclasts were seen at the anterior lambdoidal suture two days after vitamin D administration. At the end of four days of healing, osteoclasts were evident at the coronal, the anterior lambdoidal and the posterior lambdoidal sutures as well as the endosteal sides of the ectocranial and endocranial surfaces. There were no osteoclasts in contact with uncalcified osteoid throughout the entire experimental period. Only the osteoid assumed to be overgrowth was resorbed, while osteoid in some areas was calcified and then retained. At the end of a ten day healing period, the calvarium of the experimental animal was virtually identical to that of the control animal, with the exception of some localized osteoclasis continuing.A rachitogenic diet supporting excellent health and growth in the albino rat is described in this paper.
A histochemical study of muscle spindles and their relationship to extrafusal fiber types in the rat
Authors: Yellin Herbert 
Published: February 2005

AbstractHindlimb muscles of the rat were studied in serial section with enzyme histochemical methods. Muscle fibers, both extrafusal and intrafusal, were compared as to their relative succinic dehydrogenase and phosphorylase activity, indicative of oxidative and glycolytic metabolism respectively. The superficial fascicles of a number of white (fast‐twitch) muscles are composed almost exclusively of glycolytic (type A) muscle fibers, whereas the deep fascicles contain a mixture of oxidative (type B) and oxidative‐glycolytic (type C) fibers. Muscle spindles are found only among the deep fascicles of these fast muscles. Neither the soleus, a red (slow‐twitch) muscle comprised mainly of type B fibers, nor the middle lumbrical muscles, with a fairly uniform distribution of several fiber types, exhibit so specific a spindle disposition. Thus a close spatial relationship exists between spindles and certain types of muscle fibers, presumbly representing specific types of motor units. Within the spindles, the nuclear‐bag intrafusal fibers are generally of types A and B, and of a third variety characterized by both low oxidative and low glycolytic activity. The latter fiber‐type is not commonly observed in the extrafusal musculature. Nuclear‐chain intrafusal fibers resemble type C fibers. Speed of contraction and enzymes of energy metabolism of extrafusal fibers are known to be neurally regulated. The several types of histochemically distinguishable intrafusal fibers probably reflect differences in motor innervation and possibly differing contraction‐kinetics.
Skeletal development of mice x‐irradiated in utero
Authors: Rugh R. , Duhamel L. , Osborne A. W. , Sweeney W. A. 
Published: February 2005

AbstractCF1 mice were exposed to x‐rays during development at various intervals from 0.5 day after conception to 18 days. The levels of x‐irradiation were previously established for each gestation day so that half of the exposed fetuses would survive for at least 30 days after birth. Those that survived to two months were radiographed (1,174 mice including 150 controls of the two sexes) and seven bone measurements were taken from each mouse. From conception through gestation day 10 there appeared to be no significant reduction in bone measurements as a result of embryonic or fetal x‐irradiation even though the exposures ranged from 100 R to 400 R. The greatest decrements followed exposure of the fetuses at days 15 and 16, although there was some reduction on days 13 and 14 also. The spine measurements were first reduced when x‐irradiation was done on day 11. In both the controls and those x‐rayed the average bone measurements were slightly greater for the males than for the females. Embryologically those days most radiosensitive with respect to skeletal growth were those when osteogenesis was the most active. There is no evidence that ionizing radiations prior to chondrogenesis has any effect on later skeletal development.
A cytological study of intestinal absorption in the suckling rat
Authors: Cornell Richard , Padykula Helen A. 
Published: February 2005

AbstractThe distal small intestine of the albino rat has the capacity to absorb protein and particulate matter during the suckling period. Ultrastructural and cytochemical aspects of this absorptive phenomenon were examined in the ileum. Soon after the initial ingestion of milk, a large, yellow, smooth membrane‐limited, protein body appears in the immediate supranuclear region of ileal absorptive cells and, also, many small vacuoles and membrane‐limited droplets arise between this body and the microvilli. Exogenous protein enters an elaborate superficial tubular system and is segregated in membrane‐limited vacuoles and droplets and, then, appears in the supranuclear body. The body and adjacent membrane‐limited droplets are basophilic, periodic acid‐Schiff positive, and rich in hydrolytic enzymes (acid phosphatase, ATPase, thiamine pyrophosphatase, alkaline phosphatase, esterase). The results suggest the presence of a highly developed lysosomal system during the period of protein absorption. Additional cytological features of the absorptive cells are presented.Ileal absorptive cells are normally free of lipid droplets. When emulsified lipid is introduced into the neonatal ileum, it enters into the cytoplasmic smooth membrane system, including the supranuclear body, and later appeas in the lacteals. This suggests both that the uptake of material may be non‐selective and that similar intracellular pathways may be used in transporting protein and lipid through the epithelium.
Position and orientation of the heart valves
Authors: Merklin Robert J. 
Published: February 2005

AbstractThe position and orientation of the heart valves and cusps were investigated in 125 adult and 25 stillborn cadaver hearts in an attempt to establish a reasonably uniform picture of this aspect of cardiac anatomy. The study was prompted by the fact that current textbook figures show wide variation in depicting these structures and also by the fact that the standard nomenclature of the cusps has not been fully accepted by anatomists and cardiologists. There is the additional problem of naming the cusps in congenitally defective hearts. The literature related to cases of great vessel transposition is particularly confusing and the lack of a uniform figure of the heart valves and disagreement about the cusps adds to the confusion.The arrangement of the valves and cusps was found to be very uniform in the specimens studied and a standard figure is suggested to replace the variations seen in current texts. It is further suggested that the approved nomenclature of the cusps be followed and several supplemental terms be recognized as accurate. non‐ambiguous and useful, particularly in descriptions of the congenitally defective heart.
On the development of bone marrow innervation in new‐born rats as studied with silver impregnation and electron microscopy,
Authors: Calvo Wenceslao , Forteza‐Vila Jerónimo 
Published: February 2005

AbstractThis study of innervation of the bone marrow in new‐born rats demonstrates that major signs of differentiation occur in the nerves at the end of the second week after birth. Myelinated nerve fibers begin to acquire their myelin sheath at this time. The Schwann cells show abundant ergastoplasmic reticulum. Some of these cells separate individual axons and wrap them up with the double membranes that form the myelin sheath. From then on, the nerves of the marrow contain both myelinated and nonmyelinated fibers. Fibroblasts also differentiate during this time, producing collagen fibers around the nerves. Some fibroblasts are interconnected by desmosome‐like structures. Fibroblasts and collagen fibers form the connective tissue sheaths of the nerve (perineurium and endoneurium). Upon completion of the myelin sheath by the Schwann cells and the connective tissue sheath by the fibroblasts, nerves of the marrow acquire the morphological characteristics of the peripheral nerves of the adult animal. The fine structure of the axons in contact with the muscle fibers of the arterial wall correspond to Type 2‐a of Watari. These nerve fibers are considered to be of sympathetic type. The time of maturation of nerves in the bone marrow coincides with the beginning of responsiveness to stimulatory and inhibitory conditions demonstrated in this organ by other authors.
The ultrastructure of the stellate cell in the rabbit pars distalis,
Authors: Schechter Joel 
Published: February 2005

AbstractStellate cells in the rabbit pars distalis have been studied electron microscopically from birth to adulthood. During this period the stellate cells are found in abundance throughout the pars distalis and are the only consistently agranular cells observed in the pars distalis parenchyma. Identifying features of stellate cells are fine cytoplasmic filaments and farreaching cytoplasmic processes. The cytoplasmic processes ramify between adjacent parenchymal cells and are connected to other stellate cells by desmosomes. The stellate cells, linked to one another by desmosomes, thus constitute a meshwork within which the granulated parenchymal cells reside. Processes of stellate cells are also found interposed between the parenchymal basal lamina and the granulated parenchymal cells. The cytoplasmic filaments are distributed throughout the cytoplasm and extend into the fine processes. The filaments do not appear to have any particular orientation to the plasma membrane. Compared to granulated cell types, the cytoplasmic organization of stellate cells is not complex. Mitochondria, smooth and granular endoplasmic reticulum, Golgi membranes, ribosomes, dense bodies and lipid droplets are distributed throughout the cytoplasm, but not in great numbers. Nuclear chromatin is uniformly distributed. A nucleolus may or may not be evident.The ultrastructural features of the stellate cells are in many respects unchanged from birth to adulthood. An exception is in one‐to‐two‐day‐old neonates when in some stellate cells the quantity of cytoplasmic filaments appears increased and there is hyperplasia of the endoplasmic reticulum and Golgi membranes. A similar hyperplasia of these stellate cell organelles can be produced experimentally in adult rabbits by administration of Metopirone.Though the morphological evidence supports a structural or metabolically supportive function for the stellate cell, an additional role as the possible source of adrenocorticotrophic hormone is also discussed.
Renewal of Paneth cells in the small intestine of the mouse
Authors: Cheng Hazel , Merzel J. , Leblond C. P. 
Published: February 2005

AbstractThe origin and fate of Paneth cells were examined in duodenum, jejunum and ileum of adult female mice, using radioautography after administration of 3H‐thymidine either in a single injection or in drinking water for four days or as a continuous infusion for up to ten days. The tissues were fixed by perfusion with 4% paraformaldehyde. One‐micron thick, Eponembedded single or serial sections were stained with Regaud's hematoxylin, radioautographed, and counterstained with safranin O.Mitosis of Paneth cells is never observed, nor are these cells ever labeled one hour after 3H‐thymidine. Hence, Paneth cells do not divide.However, a few days after single injection or prolonged administration of 3H‐thymidine, labeled Paneth cells appear. The first labeled cells have tiny granules but, as the cells age, larger and larger granules are observed.Adjacent to Paneth cells are slender undifferentiated cells which show frequent mitoses and early labeling. The evidence points to some of these cells transforming into Paneth cells. Since occasionally Paneth cells degenerate, the newly‐formed ones would provide replacement for those which die, thus insuring the steady state of the Paneth cell population. The renewal of this population is characterized by a turnover time of about three weeks.
The opisthonephric kidney of the sea lamprey of the great lakes, Petromyzon marinus L. I. The renal corpuscle
Authors: Youson John H. , McMillan Donald B. 
Published: February 2005

AbstractThe renal corpuscle of the opisthonephric kidney of the Great Lakes lamprey, Petromyzon marinus L., is described. In the larvae (ammocoetes) several renal corpuscles, each consisting of lobed glomeruli and Bowman's capsules, are placed behind one another and there is a progressive lengthening of the posterior corpuscles as the animal ages, apparently by the addition of new glomeruli posteriorly. Bowman's capsule surrounds a single loop and consists of parietal and visceral layers which are similar to those seen in higher vertebrates.The kidney of the adult has a single complex renal corpuscle which extends almost its entire length. Present evidence indicates that the adult kidney is formed during transformation and that the larval renal corpuscles do not contribute to the single elongate corpuscle of the adult. A large number of lobed glomeruli, lying one behind the other, form the elongate glomus. Interposed between each pair of lobes is the dilated end of a nephron. There are no typical Bowman's capsules in the adult although where these nephric capsules invest the blood vessels of a lobe they develop podocytes similar to those of the visceral layer of Bowman's capsule and elsewhere they consist of a simple squamous epithelium similar to that of the parietal layer.