bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of starvation and refeeding on mucosal size and epithelial renewal in the rat small intestine
Authors: Altmann Gabriel G.
Published: February 2005

Adult male rats were fasted for 0 (controls), three, five and seven days; a group was refed for one day after six days of starvation. Histological samples were taken from five regions along the length of the small intestine. The sizes of the villi, crypts and mitotic pool were estimated by measuring the number of epithelial cells per villus and crypt section and the number of mitotic figures per crypt section. Additional studies were carried out using colchicine for estimating mitotic time and methotrexate for inhibiting mitosis.

All three parameters decreased progressively during starvation; the decrease in villus size was most pronounced in the duodenum and gradually less distalward. Refeeding increased the mitotic pool in every region; crypt size did not increase and villus size increased slightly in duodenum and jejunum only. When refeeding was combined with mitotic inhibition, the cell population of the crypts became depleted by 30–40% without change in villus size; thus, renewal appeared to continue by crypt cells migrating to the villi.

Mitosis in the crypts is used for epithelial renewal in the adult intestine. The calculated turnover time of the epithelium was longer than normal and similar in every stage of starvation. Refeeding appeared to stimulate renewal. Since villus size changed somewhat independently from mitotic activity, the involvement of a separate mechanism controlling villus size was indicated.
Retinal damage after prolonged exposure to visible light. A light and electron microscopic study
Authors: O'Steen W. Keith , Shear Charles R. , Anderson Kenneth V.
Published: February 2005

Albino rats were exposed to fluorescent illumination for four to six months at an intensity which would not cause photocoagulation of the retina. Electron and light microscopic studies indicated that the retinas of these animals were irreversibly damaged and that the degeneration was specifically localized to the photoreceptor cells. Photoreceptors were not found in any of these retinas. Prolonged exposure to low intensity, visible light had no apparent effect on the bipolar neurons and ganglion cells or on their interconnections in the inner plexiform layer. Pigment epithelial cells survived the exposure and were unchanged except for extreme compaction of the apical villous processes in the retinal zone where the photoreceptors were located prior to their destruction. In some degenerated retinas the bipolar neurons were displaced along blood vessels extending from the inner ganglion cell layer to the outer retinal layers. Some of these blood vessels apparently formed anastomoses between the central retinal circulation and the choriocapillaries. The outer Müller cell processes, which contained numerous lamellated and tubular structures, expanded to cover the area adjacent to the pigment epithelium and to form an outer limiting membrane, which was displaced in position in comparison with a normal retina.
Electron microscopy of the red pulp of human spleen
Authors: Chen Li‐Tsun , Weiss Leon
Published: February 2005

Terminating arterial vessels, the structure of sinuses and cords, and the passage of cells through the sinus wall in the red pulp of human spleen were studied. All terminating arterial capillaries arterial capillaries observed opened into cords. The distance between terminating arterial capillaries and sinuses varied. Macrophages were commonly present at arterial terminations. Arterial capillary endothelium contained filaments about 80 Å in diameter. Blood cells were frequently present in the capillary lumen or in passage through the capillary wall into cords. Endothelial cells of sinuses contained three distinctive structures: loosely organized cytoplasmic filaments, tightly organized finer filaments, and micropinocytotic vesicles. Many micropinocytotic vesicles about 0.1 μ in diameter were present just beneath the plasma membrane of the lateral and luminal sides of sinus endothelial cells and a few at the basal aspect. Loosely organized filaments about 80 Å in diameter ran parallel to the longitudinal axis of the sinus endothelium. The finer filaments about 30–50 Å in diameter were tightly organized as filamentous bands and present basally. The filaments of the bands appeared inserted upon the plasma membrane. They were also present in the cordal reticular cells and terminating arterial capillaries. Free cells were frequently present in passage through the slits of the sinus wall. There were no preformed or fixed apertures in the sinus wall. The basement membrane and reticular fibers were completely covered by the endothelial cells and/or cordal reticular cells.

It is likely that those slits between endothelial cells in the sinus wall not covered by the basement membrane are potential passageways for cells moving from the cords into the sinus. The larger cytoplasmic filaments are likely contractile. The filamentous bands appear to maintain cell shape, stabilize the wall in relation to the basement membrane, and are probably operative in the control of cellular passage through the slits of sinus wall.
Longevity of male and female, intact and gonadectomized, untrected and hormone‐treated, neoplastic and non‐neoplastic syrian hamsters
Authors: Kirkman Hadley , Yau P. K. S.
Published: February 2005

Two thousand four hundred and fifty‐six male and 1432 female Syrian hamsters, dying spontaneously at different ages, are arranged in age at death increments of 100 days. These are arranged further into groups of intact male, female, orchiectomized and ovariectomized animals; animals with and without benign or malignant tumors; animals treated with androgen, estrogen or both; animals with or without various hormonal imbalances; solitary and grouped animals; and virgins and breeders. The age at death incidences of each sex are plotted in graphs. Although longevity is decreased by gonadectomy and by neoplasia, the same sex differential is evident in each group, with males showing a distinct and consistent tendency to outlive females. Results are expressed in absolute numbers and in percentages. The data provide strong evidence supporting the frequently published suggestion that the Syrian hamster may be remarkable among mammals in that males tend to outlive females.
Ultrastructural studies of transmural migration of blood cells in the bone marrow of rats, mice and guinea pigs
Authors: Campbell Ferrell R.
Published: February 2005

The ultrastructure of bone marrow of rats, mice and guinea pigs was studied after fixation by vascular perfusion. Serial sections were examined to determine the structure and site of pores in lining cells. It was concluded that pores are transient structures occurring only in conjunction with migrating blood cells. These pores occur within lining cells and most frequently near junctions of contiguous lining cells. Microfilaments in lining and adventitial cells are described and their possible roles discussed.
In vitro studies on ciliary activity within the oviducts of the rabbit and pig
Authors: Gaddum‐Rosse P. , Blandau R. J.
Published: February 2005

Direct observations of ciliary activity on the mucosal surface of mammalian oviducts have rarely been reported. Yet such studies might help to determine the relative value of ciliary action in gamete transport through the ducts. The purpose of this study was to examine the direction and rapidity of ciliary currents in the oviducts of two mammalian species, the rabbit and the pig. Fresh oviducts were slit open longitudinally and submerged in Hanks' balanced salt solution at 37°C. The movements of particulate matter, such as stained lycopodium spores and 15 μ microspherents, placed on the mucosal surface, were observed and recorded on film. In both species ciliary currents in the ampulla swept the particles toward the ampullar‐isthmic junction. In the isthmus of the pig oviduct the particulate matter was transported in the reverse direction, toward the ovary. The pro‐ovarian current could be demonstrated throughout the isthmus, beginning a few millimeters above the uterotubal junction. In the rabbit a similar current was detected, but it was not as extensive as in the pig. In the upper isthmus of the rabbit oviduct, particulate matter and rabbit eggs in the “mucin coat” merely rotated or “tumbled” on the surface with little movement in either direction. This is the first report of pro‐ovarian ciliary currents for any mammal, and we believe these to be important for sperm transport through the isthmus. The action of cilia during egg transport is discussed.
Duration of the cycle of the seminiferous epithelium and the spermatogonial renewal in the monkey Macaca arctoides
Authors: Clermont Yves , Antar Michael
Published: February 2005

Monkeys were sacrificed at three hours and at 12 days‐3 hours after an intraperitoneal injection with 3H‐thymidine. Radioautographs were prepared of periodic acid‐Schiff‐hematoxylin‐stained sections of the testes. At three hours, the most evolved labeled germ cells were leptotene spermatocytes in stage VIII of the cycle; at 12 days‐three hours the most evolved labeled cells were pachytene spermatocytes in stage IX of the succeeding cycle. Thus, over a 12‐day interval, the most evolved labeled spermatocytes had advanced through slightly more than one complete cycle. A quantitative analysis of tubular cross sections containing labeled spermatocytes permitted the calculation of the duration of one cycle of the seminiferous epithelium which turned out to be 11.6 days. The whole process of spermatogenesis which begins with the first spermatogonial mitoses taking place in stage VIII and terminates with the release of spermatozoa taking place in stage VI of the cycle, extends over the duration of 3.8 consecutive cycles and therefore requires approximately 44 days.

On the same histological material counts of resting and dividing spermatogonia were performed at various stages of the cycle to determine their mode of proliferation and renewal. Six mitotic peaks were disclosed and were located in stages VIII, X, XII, II, IV and VI of the cycle. Cell counts and labeling indices indicated that the pale type A spermatogonia were the cells dividing during the first two of these six peaks of mitoses while the type B spermatogonia divided during the remaining four peaks of mitoses. The dark type A spermatogonia were not seen to divide during the cycle and may be considered as “reserve stem cells.” Cell counts and cell ratios indicated further that the pale type A spermatogonia divided in stage VIII of the cycle (and some in stage IX) to yield about twice their number of pale type A spermatogonia: of several possible schemes the authors believe that half of these entered a long interphase and became stem cells for the spermatogonia to be formed during the next cycle; these may be referred to as “renewing stem cells”; we consider that the other half of the pale type A spermatogonia arising from stage VIII peak of mitoses divided in stage X to produce type B spermatogonia. The latter cells then could enter the series of four consecutive mitoses during which they doubled their number each time to yield a generation of primary spermatocytes.
Ultrastructure of germ cells and sertoli cells in the postnatal rabbit testis
Authors: Gondos Bernard , Renston Richard H. , Conner Lucy A.
Published: February 2005

Spermatogenesis begins in the rabbit at seven to eight weeks of age. During the preceding postnatal period, seminiferous tubules contain round to oval prespermatogonia arranged in pairs at the tubular periphery and elongated Sertoli cells lying perpendicular to the basal lamina. Prespermatogonia are distinguished from fetal gonocytes by their abundant cytoplasm and the presence of intercellular bridges. Preceding the onset of spermatogenesis, prespermatogonia undergo diminution in cell size and cytoplasmic condensation. At the same time there is marked nucleolar enlargement, with elaborate proliferation of the nucleolonema. By the end of the seventh week, characteristic type A and B spermatogonia are present. Spermatocytes are seen at the end of the eighth week. Spermatids appear in the twelfth week, coincident with tubular lumen formation. The duration of the initial spermatogenic cycle is similar to that in the adult. Sertoli cells are closely associated with adjacent germinal elements throughout the postnatal period. The Sertoli cell cytoplasm includes elongated mitochondria, abundant smooth endoplasmic reticulum and prominent Golgi complexes. Many of the cells contain phagocytized material, presumably derived from degenerating germ cells. The observations suggest possible mechanisms by which Sertoli cells support early germ cell maturation.
Pinocytosis by epithelium associated with lymphoid follicles in the bursa of fabricius, appendix, and Peyer's patches. An electron microscopic study
Authors: Bockman Dale E. , Cooper Max D.
Published: February 2005

The fine structure and micropinocytotic capabilities of epithelial cells closely associated with lymphoid follicles in the chicken bursa of Fabricius, rabbit appendix, and mouse Peyer's patch were compared. Epithelial cells capable of transporting ferritin and India ink tracers from the lumen were demonstrated in all three locations. Epithelial cells not associated with lymphoid follicles in the bursa and appendix did not express pinocytotic activity. Lymphoid cells were identified in bursal epithelium of chick embryos as early as the twelfth day of incubation. These lymphoid cells were smaller than typical bursal lymphocytes, had dense cytoplasm, numerous cytoplasmic projections, and prominent nucleoli. The small lymphoid cells were first demonstrable at a time in incubation during which lymphoid stem cells have been shown to migrate into the bursal epithelium. Lymphoid cells were seen earlier than the specialized follicle‐associated epithelium. It is concluded that specialized pinocytotic follicle‐associated epithelium does not induce initial migration of stem cells into areas along the intestinal tract, but that this transepithelial pinocytotic flow of intestinal contents after birth may provide a significant stimulus for attraction, proliferation and egression of lymphocytes.
Experimental manipulation of desmosome structure
Authors: Borysenko Joan Z. , Revel Jean Paul
Published: February 2005

A systematic investigation of the effects of proteolytic enzymes, chelators and detergents on desmosomes originating in a variety of tissues was undertaken. Although junctions from different tissues are morphologically similar, we found great differences in their sensitivity to various reagents, indicating dissimilarities in biochemical composition.

In general, desmosomes from stratified squamous and glandular epithelia were insensitive to ethylenediaminetetraacetic acid (EDTA), but readily dissociable with trypsin. Enzymatic digestion caused disruption of material within the junctional extracellular space, and dislocation of paired desmosomal plaques. In contrast, the extracellular components of desmosomes from simple columnar epithelia were usually EDTA‐sensitive but trypsin‐resistant. There were, however, exceptions to the general pattern. Desmosomes from rat pancreas were affected only by the detergent sodium desoxycholate (DOC). DOC also solubilized the intermediate dense line of desmosomes from the frog skin.

We have divided desmosomes into two broad categories based upon the differential effects of these reagents. One group, sensitive to trypsin or DOC, may be functionally “stable” in maintaining cell‐to‐cell associations for long periods. Such junctions occur in stratified squamous and many glandular epithelia. Another group of desmosomes, affected by chelating agents, may be physiologically “labile” or plastic. These junctions, occurring in simple columnar epithelia such as the gut, may respond to physiological stimuli by opening or closing, thus allowing intercellular migration of cells and substances passing through the epithelial sheet.
Dynamic function of the human fibula
Authors: Weinert Carl R. , McMaster James H. , Ferguson Roger J.
Published: February 2005

There is general agreement that motion between the tibia and fibula is an important and necessary part of normal ankle function in man.

We studied the function of the tibiofibular unit in healthy college athletes running barefooted. Movies and cine‐roentgenograms showed the fibula moving downward and laterally during the strike phase of gait. Fibular motion in this direction rather than upward, as suggested by cadaver studies, deepens the ankle mortice and stabilizes the joint when the ankle is dorsiflexed and load is the greatest. This motion also stretches the interosseous membrane and tibiofibular ligaments, converting compressive force in the ankle to tension in these structures.
The morphology of M. tensor veli palatini in the five‐month human fetus
Authors: Rood Stewart R.
Published: February 2005

The morphology of M. tensor veli palatini in the five‐month human fetus was studied using a light microscopic procedure. The muscle was found to be divided into two fairly distinct bundles. In cross‐section, the fibers of the more lateral bundle coursed in an inferior‐superior direction from the hard palate to the level of the cranial base. The fibers of the bundle lying just lateral to the Eustachian tube and medial to the previously identified bundle ran in a medial‐lateral direction between their attachment to the lateral membranous tubal wall and the fibroelastic tissue layer separating the two bundles. It is suggested that these observations may account in part for lateral movement of the lateral membranous wall without necessitating a hamular or velar insertion of the tensor palati.
The early differentiation of the testis and interstitial cells in the fetal pig, and its duplication in organ culture
Authors: Moon Young S. , Hardy Margaret H.
Published: February 2005

The unusual histogenesis of the fetal pig testis was examined as part of a study of its role in reproductive biology. Three types of interstitial cells were defined and their numbers estimated per unit area of testicular tissue in 6 μ‐serial sections. Statistical analysis of the percentage frequency of each cell type showed that the mature Leydig cells (C‐type) reached a peak at about 4.5 cm crown‐rump length (CRL) fetus and then fell to a low level, rising again sharply from 20 cm CRL until near birth. It was postulated that the first mature Leydig (C‐type) cells arose from mesenchymal (A‐type) cells which differentiated first into immature Leydig (B‐type) cells, and the process was repeated in the last part of fetal life.

Mixtures of cock plasma, chicken embryo extract and balanced salt solution allowed maintenance and differentiation of whole fetal testes or testicular slices as organ cultures in Maximow slide assemblies for 6 to 14 days. Medium 199 with 10% bovine serum allowed maintenance and differentiation in some explants for at least six days. Indifferent gonads developed into recognizable testes or ovaries. Testes from 2.5, 3.0, and 3.5 cm CRL fetuses differentiated at a fairly normal rate, and some of their interstitial cells underwent the transformation postulated from the in vivo study. It was concluded that organ cultures from indifferent gonads and early testes provided living, functioning systems which could be used to test for androgenic activity with biological indicators.
Morphogenesis of the fetal membranes and placenta of the black bear, Ursus americanus (pallas)
Authors: Wimsatt William A.
Published: February 2005

Knowledge of placentation in bears has been limited to analysis of a single shed placenta of the European brown bear. It was shown that the mature allantoic placenta is discoidal, endotheliochorial, provided with a circular marginal hematoma, and that the allantoic sac is large and permanent. The present study, based on a small series of conceptuses younger than any previously examined, provides new details concerning implantation and the morphogenesis of the fetal membranes, placenta and paraplacental organs. Implantation in the black bear is central and superficial; the orientation of the embryonic disc is antimesometrial. Amniogenesis and chorion formation are almost certainly accomplished by folding. The decidual reaction is minimal. As in other carnivores the yolk sac is prominent early, but progressively declines. A well‐developed choriovitelline placenta is formed early, but is eliminated before the limb bud stage. The bilaminar omphalopleure persists only slightly beyond the limb bud stage. The allantois, however, is extensive and permanent. Initially, the allantoic placenta is cup‐shaped but eventually flattens out to form the discoidal placenta. It is lobuliform and endotheliochorial, and probably a marked attenuation of the interhemal membrane occurs in later stages. The marginal hematoma, which is completed before the limb bud stage, is formed by enlargement and coalescence of separate extravasations, and apparently remains fully functional to term. Overall, morphogenetic sequences and relationships in bears more nearly resemble those of the dog than of other carnivores.
The origin, distribution and disappearance of surface cilia during embryonic development of Rana pipiens as revealed by scanning electron microscopy
Authors: Kessel R. G. , Beams H. W. , Shih C. Y.
Published: February 2005

Cilia begin to grow from the free surface of some ectodermal cells during the neural plate stage (stage 13). Ciliary growth is not closely synchronized between cells in the same embryo, but the number of ciliated cells increases greatly during neural fold development and further growth in length of pre‐existing cilia occurs. Ciliated cells are numerous and widely distributed over the surface of early tailbud stages. However, cilia do not develop on cells in the neural plate and inner sides of the neural fold, and only an occasional ciliated cell is observed on the surface of the paired suckers. The number of ciliated epidermal cells per embryo increases during tail growth (stages 18–22). Ciliated epidermal cells persist after hatching (stage 20), but regression of cilia can be detected in stage 24 larvae. By late stage 25, most of the cilia have disappeared and the morphological variations observed indicate that the process involves resorption of cilia. Non‐ciliated (secretory) ectodermal cells from the neurula onward to stage 25 synthesize granules which are released to provide a mucous‐like coat for the embryo and larva. The surface structure of both ciliated and non‐ciliated ectodermal cells is described in sections studied with the transmission electron microscope and compared to the surface architecture of both cell types observed with the scanning electron microscope.
Spermatogonial stem cells in the albino rat
Authors: Clermont Yves , Hermo Louis
Published: February 2005

The existence of two classes of spermatogonial stem cells in the rat testis, i.e., reserve type A0 spermatogonia and renewing, types A1‐A4 spermatogonia, postulated by Clermont and Bustos‐Obregon (′68), was reexamined in a quantitative analysis of type A spermatogonia in both whole mounts of tubules and in radioautographed sections of testes from animals killed at various times, up to 26 days, after one or multiple injections of 3H‐thymidine.

The cell counts obtained from whole mounts of tubules revealed that the number of isolated type A0 cells per unit area of limiting membrane remained constant throughout the cycle of the seminiferous epithelium. Paired type A0 spermatogonia also remained unchanged in number per unit area of basement membrane from stage I to stage VIII of the cycle. The low mitotic index of type A0 spermatogonia (0.1%) indicated that these cells were not actively involved in the production of spermatogonia or spermatocytes during each cycle of the seminiferous epithelium and thus were considered as reserve stem cells.

The type A1 spermatogonia, which are formed during stage I of the cycle, remained resting until stage IX, when they undertook a series of four successive divisions resulting in the production of new type A1 and Intermediate‐type spermatogonia. An analysis of the labeling indices of type A spermatogonia obtained from cell counts in radioautographed testicular sections after a single or multiple 3H‐thymidine injections indicated that the percentages of labeled type A cells corresponded to the percentages of type A1‐A4 at each stage, whereas the percentages of unlabeled type A cells corresponded to the percentages of type A0 spermatogonia obtained from counts of cells in whole mounts. This confirmed that type A0 cells were generally non‐proliferative throughout the cycle of the seminiferous epithelium while the type A1‐A4 spermatogonia underwent complete renewal during each cycle. The present results thus support the concept of the existence of two classes of spermatogonial stem cells in rats.
Direct quantitative estimation of Paneth and total cell populations in the jejunal glands of Lieberkühn
Authors: Malinin George I.
Published: February 2005

Direct morphometric estimation of the number of intestinal crypts per 10 mm length of jejunum, the total number of cells per crypt, and the number of Paneth cells per crypt was performed using Zenker‐fixed, serially sectioned small intestines from adult BALB/c mice. The mean volume of a crypt cell was estimated to be in the order of 6.6 ± 0.1 × 10−4 mm3, while the total volume of all cells in a single crypt was 1.833 ± 0.02 × 10−1 mm3. The cell population per crypt was 278 ± 7 cells, of which 44 ± 10 were Paneth cells. It was estimated further that 265 ± 30 crypts per 10 mm length of jejunum contained 7.4 ± 0.1 × 104 cells, including 1.2 ± 0.24 × 103 Paneth cells. The volume of all crypt and Paneth cells per 10 mm length of jejunum was in the order of 49 ± 1.2 and 8 ± 1.8 mm3, respectively. The volume of the tunica muscularis and the surface area of the crypt's lumina were estimated to be 33.5 ± 2.2 mm3 and 118 ± 19 mm2, respectively.
Motor‐sensory cortex‐corticospinal system and developing locomotion and placing in rats
Authors: Hicks Samuel P. , D'Amato Constance J.
Published: February 2005

Normal and abnormal development of movement in the rat were studied by investigating the growth and organization of the motor‐sensory cortexcorticospinal tract system (MSC‐CST) and the functional and morphologic effects of ablating the MSC or quadrants of it at different ages. Major growth of the MSC outflow, the CST, in the brain stem and rostral cord occurred in the second and third weeks postnatally, coinciding approximately with the normal mid‐third week transition from infantile to mature locomotion. Ablation of the MSC at birth revealed that while the MSC‐CST was not essential for ordinary locomotion on flat terrain, its presence hastened normal development of this kind of movement, and that it was absolutely essential for locomotion on difficult terrain. The MSC quadrants showed quite different, and in some domains mutually exclusive, CST projection patterns to forebrain, diencephalon, brain stem, and spinal destinations (determined by Fink‐Heimer‐Nauta fiber degeneration studies). Ablation of some quadrants produced distinctive syndromes of disordered movement: the posterolateral quadrant related to active grasping in positioning limbs, while the posteromedial quadrant related to tactile motorsensory positioning of limbs. Thus in addition to the classic somatotopic organization of the MSC, there was another kind of organization into regions concerned with components of integrated movement of a number of parts of the body. Several forms of aberrant circuitry developed after MSC ablations in infants, but their possible roles in functional adaptation remain to be determined.
Light and electron microscopic studies of postcapillary venules in developing human fetal lymph nodes
Authors: Bailey Raymond P. , Weiss Leon
Published: February 2005

Developing lymph nodes from 30 human fetuses with crownrump lengths (CRL) of 38 mm (8.7 wk) to 245 mm (26 wk) were studied by light and electron microscopy. Blood vessels that appear to be postcapillary venules (PCV) are present in nodes of 47 mm CRL and older fetuses. These venules first appear in nodes when the nodal population of lymphocytes is sparse. In these early nodes PCV are distributed randomly and consist of a low endothelium, underlying basal lamina and incomplete pericyte sheath. Early nodal PCV are distinguished from other nodal blood vessels by the presence of lymphocyte diapedesis and several luminal lymphocytes.

In the late stages of nodal development PCV are the more common noncapillary blood vessel and appear in the parenchyma near the periphery of the node. Late nodal PCV are generally characterized by a cuboidal endothelium that is rich in Golgi apparatus, lysosomes and Weibel‐Palade bodies. The lumen and wall of late nodal PCV contain lymphocytes.

The relationship between the development of the parenchyma of fetal nodes and the appearance and activity of PCV, the passage of lymphocytes through the PCV wall and the fine structure of developing PCV are described. It is suggested that the lymphocytes that first appear in developing nodes, and the majority of the lymphocytes found in late nodes, migrate to the node via the blood vascular system and enter the nodal parenchyma by passing across PCV endothelium.
Morphogenesis of rat lingual filiform papillae
Authors: Baratz Robert S. , Farbman Albert I.
Published: February 2005

The morphogenesis of filiform papillae on rat tongue was investigated with the electron microscope. Tongue rudiments were first seen on the 12th day of gestation. At 15–17 days, dermal papillae had formed and were arranged in hexagonal array on the dorsal lingual surface. Capping each dermal papilla was a two‐layered epithelium that protruded slightly above the lingual surface, thus forming the early filiform papilla. In the next stage of development, at 18–19 days of gestation, the epithelium lining the papilla had differentiated into two cell populations, one producing hard keratin, the other producing soft keratin. Some of the keratinized epithelial cells assumed a position at an acute angle to the tongue surface and extended deep into the epithelium. In the next stage, 20–21 days, a cleft appeared within these angularly oriented cells. This resulted in the division of the epithelium into keratin‐lined individual filiform papillae. Finally, the individual papillae increased in size to the adult form.
Inverse prominence of ependyma and capillaries in the spinal cord of vertebrates: A comparative histochemical study
Authors: Sarnat Harvey B. , Campa Justiniano F. , Lloyd Judith M.
Published: February 2005

Spinal cords of 15 species representing six classes of vertebrates and the protochordate amphioxus were examined with histochemical methods for esterase, ATPase, LDH, PAS, and PAS‐phosphorylase. Ependymal and glial cell processes were demonstrated and resembled heavy metal impregnations. Capillaries also were shown. The prominence of glycogen‐rich ependymal structures in the spinal cord of nonmammalian vertebrates, and the increase in intramedullary blood vessels in placental mammals, suggest an inverse relationship between the relative development of the ependyma and of the blood supply. The marsupial opossum has sparseness of both ependyma and capillaries, but exhibits an extensive pattern of branched glial processes in both white and gray matter.
The development of primordial and definitive amniotic cavities in early rhesus monkey and human embryos
Authors: Luckett W. Patrick
Published: February 2005

Re‐examination of early rhesus monkey and human embryos in the collection of the Carnegie Institution of Washington suggests that the mechanism of amniogenesis in both is basically similar to that of the hedgehog and vespertilionid bats. A primordial amniotic cavity develops by cavitation within the embryonic mass of 10‐day rhesus monkey, and 7‐day human, blastocysts. This primordial cavity has no relationship initially with the overlying trophoblast, contrary to earlier reports. Subsequently, there is a thinning and peripheral spreading of the epiblastic roof of the primordial cavity, resulting in partial opening of the roof and formation of a slightly cupped embryonic disc. The resulting space is not homologous with the primordial amniotic cavity; instead, it is a transitory tropho‐epiblastic cavity. The definitive amniotic epithelium forms by the upfolding and mitotic proliferation of the margins of the epiblastic disc; this process is completed in 11‐day rhesus, and 9‐day human, blastocysts.

Amniogenesis by cavitation is associated with the persistence of polar trophoblast following implantation, and it is suggested that this cavitation process may be essential for providing a free epithelial surface for the morphogenetic movement of epiblastic cells during subsequent formation of the primitive streak.
Correlative microscopy of enamel prism orientation
Authors: Weber Dennis F. , Glick Paul L.
Published: February 2005

Both mature and developing human enamel were studied by correlative light and electron microscopic techniques. Ordinary light microscopic observations of routinely prepared ground sections produced a totally inaccurate impression of enamel prism direction. In contrast, ground sections which were acid‐etched and viewed with phase contrast optics, as well as thin (0.5 μm) sections, were in concert with further electron microscopic preparations. The appearance of longitudinally sectioned prisms as demonstrated on thick ground sections is often the result of structural interrelation between groups of obliquely sectioned prisms. The arrangement between enamel prism heads and tails is often such as to produce the light microscopic appearance of classical enamel cross striations. The production of such optical artifacts may be related to conflicting interpretations concerning enamel cross striations as well as light microscopic descriptions of the histopathology of enamel caries.
Distribution of 125I‐labeled rat growth hormone in regional brain areas and peripheral tissue of the rat
Authors: Stern Warren C. , Miller Maravene , Resnick Oscar , Morgane Peter J.
Published: February 2005

The uptake of intraperitoneally injected 125I‐labeled rat growth hormone into brain and peripheral tissues was measured in normal and hypophysectomized adult rats. A significant level of radioactivity was observed in the seven brain regions examined – the telencephalon, diencephalon, midbrain, pons‐medulla, cerebellum, pineal and pituitary glands. The pineal and pituitary glands, which are outside the blood‐brain barrier, contained three to four times the concentration of radioactivity of the other brain regions. Compared to brain, the level of radioactivity was much higher in peripheral tissues (the diaphragm, kidney, serum and liver). For example, the serum contained ten times the level of radioactivity of most brain regions. For a given tissue, however, the normal and hypophysectomized rats showed a comparable amount of 125I‐growth hormone. Trichloroacetic acid precipitates from each tissue sample showed that peripheral tissues had a higher proportion of radioactivity (35–48% of total tissue radioactivity) than the brain samples (13–26%). The data support the view that growth hormone, or a metabolite can enter the central nervous system and may directly affect on‐going metabolic processes.
Loss of synapses in the dentate gyrus of the senescent rat
Authors: Bondareff William , Geinisman Yuri
Published: February 2005

Synapses were counted in electron micrographs of the middle third of the molecular layer of the dentate gyrus of Fischer 344 rats, 3 months and 25 months of age. A 27% decrease in the number of synapses was found in senescent animals compared with young adults. This loss of synapses could not be correlated with changes in synaptic size, tissue volume or number of postsynaptic granule cells.
An angiographic study of the carotid arterial and jugular venous systems in the cat
Authors: Kumar A. J. , Hochwald G. M. , Kricheff I.
Published: February 2005

Standard techniques for performing carotid angiography in dogs and in man were adapted to the cat in order to study the vascularization of both intracranial and extracranial structures. Venous drainage was examined by venography of selected vessels. The carotid‐cerebral and the vertebral‐basilar arterial systems of the cat were studied, although no attempt was made to define the territory supplied by each system.

In serial angiograms, vascularization of the rete mirabile conjugatum was visualized, and distinct arterial and venous retia were delineated. Large facial veins were seen approximately one second after the intra‐arterial injection of radio‐contrast material. The early filling of the large facial veins appeared to be the result of an artery‐to‐venous shunt. Contrast material flowed posteriorly in these veins and drained into the venous rete. When contrast material was injected either into the sagittal sinus or retrograde in the external jugular vein, the internal jugular vein was visible in four of ten cats. This vessel drained blood directly from intracranial contents before anastomosis with the vertebral and external jugular veins.
Immunological competence in Snell‐Bagg pituitary dwarf mice: Response to the contact‐sensitizing agent oxazolone
Authors: Schneider Gary B.
Published: February 2005

Snell‐Bagg pituitary dwarf mice are an autosomal recessive mutant, their dwarfism being the result of an anterior pituitary defect. A number of investigators have reported that these mice, in addition to having hormonal deficiencies, have immunological defects. Dwarf mice reject allogenic skin grafts slowly, show a reduced response to contact agents and decreased graft‐vs.‐host reactivity. Other investigators have suggested that these results indicate a thymus‐cell‐deficiency. Contrary to this conclusion, we have found that the thymuses in our dwarf mice have a normal cellular composition and the T‐cell‐dependent zones in the peripheral lymphoid tissues are not deficient in lymphocytes. Therefore, this investigation was undertaken to study the response of dwarf mice to the hapten, oxazolone, which produces one type of T‐cell‐dependent response, delayed hypersensitivity, and to compare this response to that of normal littermates in animals 15 to 90 days of age.

The results of these studies indicate that the dwarf mice have the ability to develop delayed hypersensitivity, as shown by both a blastogenic response in the lymph node draining the site of sensitization (the induction phase of delayed hypersensitivity) and by a positive skin‐test. The magnitudes of the blastogenic response and the skin‐test reaction appear similar in dwarf and normal littermate animals, both histologically, and quantitatively. These results, which are in contrast to other studies, may be the result of the husbandry provided our colony of dwarf mice, and the immunological deficiencies that have been described previously may not be a necessary condition accompanying dwarfism in these mice.
Cytological development of yolk sac endoderm and protein‐absorptive mesothelium in the little brown bat, Myotis lucifugus
Authors: Enders Allen C. , Wimsatt William A. , King Barry F.
Published: February 2005

The yolk sac of the little brown bat is unusual in that during the course of gestation both the inner endodermal cells (bordering the yolk sac cavity) and outer mesothelium (facing the exocelom) form simple columnar epithelia which persist throughout gestation. These endodermal cells develop an extensive system of agranular endoplasmic reticulum, numerous lipid droplets and unusual “giant” mitochondria. During development the Golgi apparatus changes position from the apical to the basal side of the nucleus, reversing the polarity of the cells. In general, the endodermal cells have cytological features suggestive of synthetic or secretory activity. The mesothelial cells develop an extensive “absorptive apparatus” in their apices, while large crystalloid‐containing granules become numerous in their basal cytoplasm. The mesothelial cells have large deposits of glycogen, especially during mid‐gestation, but few mitochondria and little granular endoplasmic reticulum. Endodermal cells do not absorb exogenous protein (peroxidase) even if it is injected directly into the yolk sac cavity. However, placement of peroxidase either in the exocelom or in the maternal vascular system results in the appearance of this protein in the “absorptive apparatus” of mesothelial cells as well as in macrophages in the stroma of the yolk sac. While evidence of absorption was clear, no direct evidence of transport of tracer to fetal blood vascular system was obtained. It is postulated that a major function of the hypertrophied mesothelial cells during gestation is the absorption of proteins and possibly other substances from the exocelomic fluid. The major function of the hypertrophied endodermal cells may be synthesis and secretion of substances into the fetal circulation.
Comparative histochemistry of gastrointestinal mucosubstances
Authors: Sheahan Daniel G. , Jervis Helen R.
Published: February 2005

Two histochemical sequential staining techniques, Alcian blue‐PAS (AB‐PAS) and high‐iron‐diamine‐Alcian blue (HID‐AB), which differentiate neutral from sulfated and non‐sulfated acid mucosubstances, were applied to sections from the gastrointestinal tract of eleven mammalian species, including man, to study patterns of distribution of gastrointestinal epithelial mucosubstances. The application of these techniques under uniform laboratory conditions enabled a detailed description of epithelial mucosubstances throughout the gastrointestinal tract relative to location in each species as well as a comparison of their distribution among various species.

The results showed that all of the 11 species studied had a distinctly different distribution of epithelial mucosubstances throughout the entire gastrointestinal tract. These differences were most obvious in the stomach and duodenum. In each species, neutral mucosubstances were most evident in the stomach and acid mucosubstances in the intestines, with sulfomucins most prominent in the large bowel. Acid mucosubstances were noted in Paneth cell granules of rodent species only. These histochemical observations make available a uniform comparative basis for the normal distribution of mammalian gastrointestinal mucosubstances which should facilitate their study in diverse pathological conditions.
Postnatal development of acinar cells in rat submandibular gland as revealed by electron microscopic staining for carbohydrates
Authors: Yamashina Shohei , Mizuhira Vinci
Published: February 2005

The postnatal differentiation of acinar cells in rat submandibular gland was studied by staining with periodic acid‐thiosemicarbazide‐silver proteinate to identify carbohydrate‐containing macromolecules in the electron microscope. This method revealed glycogen particles and internal substructure in the secretory granules of developing acinar cells. On the basis of morphologic and histochemical criteria three phases of acinar cell development were defined. In the pro‐acinar phase, during the first week after birth, pro‐acinar cells and terminal tubular cells were the main components of the terminal tubules in the rudimentary gland. The secretory granules of the pro‐acinar cells contained speckled or rod‐like substructures which stained intensively for carbohydrates and were digested by proteolytic enzymes. During the second to third week after birth, which is the immature‐acinar‐cell phase, thread‐like substructures were seen in the secretory granules. These structures, which were not digested by proteolytic enzymes, disappeared gradually. The acinar cells of 4‐week‐old or older rats displayed no particular substructure in the secretion granules and represented the final, mature phase of development.
Extra‐ and intra‐cranial blood supply to brains of dog and cat
Authors: Gillilan Lois A.
Published: February 2005

The dog and cat are useful experimental animals, and information regarding their cerebrovascular patterns and the source of blood supplying their brains is important. Blood vessels to brains and heads of cats and dogs were injected with various contrast media. Extracranial and intracranial arteries were studied grossly and in cleared sections.

The proximal part of the internal carotid artery is small in the dog and nonfunctional in the cat. The largest single source of arterial blood supplying the brains of these species comes from the maxillary artery over an anastomotic ramus leading to an internal rete mirabile enmeshed in the cavernous sinus. The distal segment of the internal carotid arises from this anastomosis. The brainstem of both animals is supplied by C1 branches of the vertebral arteries, and in the dog an occipital ramus makes a large contribution to it. In addition to an internal rete mirabile, the cat possesses a large external rete mirabile surrounding the maxillary artery and giving rise to all branches in the area. It is functionally equivalent to the ramus anastomoticus in the dog.

Arterial patterns over brains of Carnivora are similar. They resemble those of lower mammals more than those of primates. Extensive extracranial arterial anastomoses located in the orbit, retia mirabilia and neck musculature are significant and make it difficult to render the brains ischemic.
Intranuclear bodies in neurons of the periaqueductal gray matter in the cat
Authors: Liu Rita P. C. , Hamilton Betty L.
Published: February 2005

The nucleoplasm of neurons in the nucleus lateralis of the periaqueductal gray matter in the cat contains fibrillar structures which have no limiting membranes. These intranuclear bodies are associated with neither the nucleolus nor the nuclear membrane and have two characteristic forms. The first, the rodlet, is a compact bundle of fibrils 2 to 8 nm in diameter. It is usually elongated in shape although it appears spherical when sectioned transversely. This rodlike structure appears to correspond to Roncoroni's rodlet or the accessory body of Cajal in light microscopy. The second and more commonly observed form is a long slender bundle of five rows of parallel fibrils. Although similar intranuclear structures have frequently been observed in the highly differentiated neurons of the sympathetic ganglia and the retina, this is the first report of their presence in the undifferentiated neurons of the isodendritic core of the brainstem.
Cholinergic innervation of the simian oxyntic gastric mucosa
Authors: Lechago Juan , Barajas Luciano
Published: February 2005

The innervation of the oxyntic gastric mucosa was studied by light and electron microscopy in the rhesus monkey. An abundant net of acetylcholinesterase‐positive nerves was seen in the lamina propria, with many slender fibers noted close to the basal lamina of the glands. Electron microscopic observation disclosed the presence of nerve fibers containing axons and varicosities in the lamina propria, often in very close proximity to the epithelial glandular cells. Nerve endings partly enveloped by a Schwann cell were occasionally seen in direct contact with a parietal cell.