bluuebunny/crossref_metadata_2025 huggingface dataset:
Innervation of the vibrissae of the California sea lion, Zalophus californianus
Authors: Stephens R. J. , Beebe I. J. , Poulter T. C.
Published: February 2005

The vibrissae of the California sea lion are richly innervated with myelinated fibers that terminate in three distinctly different endings. Large nerve bundles enter the base of the follicle and immediately branch into smaller bundles that traverse the connective tissue trabeculae below the large ring sinus. Some neurons terminate in a lamellated corpuscle in close relationship to the venous sinuses of the proximal cavernous tissues. The remainder of the nerves continue distally parallel to the glassy membrane terminating in two specific types of endings arranged in a ring about the shaft of the vibrissae at the level of the upper portion of the ring sinus. One type of ending is on the outer surface of the glassy membrane where the myelin sheath terminates abruptly and the sensory ending is flattened into a thick, lancet‐shaped structure. An extension of cytoplasm from a specialized supportive cell covers this terminal segment of the nerve on two sides, while numerous finger‐like extensions protrude into the connective tissue from the narrow, uncovered sides. The second type of ending penetrates the glassy membrane, branches, and terminates in close apposition to the Merkel cells in the outer root sheath. Amyelinated nerves of various sizes are frequently observed in the same bundles as the larger myelinated fibers, but to date, the position of their termination has not been established.
A comparative ultrastructural study of the choroid plexuses of the immature pig
Authors: Davis Donald A. , Lloyd Bolivar J. , Milhorat Thomas H.
Published: February 2005

The fine structure of the choroid plexus of the immature pig consists of an epithelial layer of cells contiguous with a subepithelial region containing fibrillar elements. The apical surface is extended as numerous digitiform microvilli. At irregular intervals, apical tufts of cilia occur that contain 10–14 cilia with a typical 9+2 subfibrillar arrangement. The cytoplasm is composed of randomly distributed smooth tubular endoplasmic reticulum, apically concentrated cisternae of rough endoplasmic reticulum, Golgi areas, glycogen and numerous mitochondria. Lateral cell membranes are typically tortuous, interdigitating and possess an apical tight junction. Various vesicles are found including pinocytotic vesicles, lipoid inclusions and lysosomes. A comparative ultrastructural study of the choroid plexuses from the lateral, third and fourth ventricles failed to demonstrate significant differences between these structures of different embryological origin.
Pathogenesis of abnormal remodeling of bones: Effects of yellow phosphorus in the growing rat
Authors: Whalen Joseph P. , O'Donohue Neil , Krook Lennart , Nunez Eladio A.
Published: February 2005

Histologic examination of metaphyseal bone of rats intoxicated with elemental phosphorus showed that inhibition of osteocytic osteolysis and chondrolysis account for widening of trabeculae and retention of the chondroid core. These changes are reflected in increased radiographic density and abnormal remodeling.
Correlation between structure and glycogen content of livers from rats on a controlled feeding schedule
Authors: Cardell Robert R. , Larner Joseph , Babcock Muriel B.
Published: February 2005

Male rats were maintained on a controlled feeding schedule and groups of animals sacrificed at 2, 15, 21, 36, 48 and 72 hours of fasting. Chemical determinations of glycogen showed that livers of rats fasted two hours contained 8.7% glycogen; 15 hours, 6.2%; 21 hours, 0.7%; 36 hours, 0.7%; 48 hours, 0.8%; and 72 hours, 0.4%. After PA/S procedures, glycogen appeared in hepatocytes of rats fasted 2 and 15 hours as large masses intensely stained. At these time‐periods, almost all cells contained significant quantities of glycogen but hepatocytes located toward portal tracts showed larger and more intensely stained masses of glycogen than found in cells near central veins. After longer periods of fasting, glycogen masses decreased in size, number, and staining intensity. The fine structure of hepatocytes from rats fasted 2 or 15 hours showed abundant α and β particles of glycogen in the form of large masses throughout the cytosome. These correlated in position and shape to the masses of glycogen seen in the light microscope. As glycogen depletion occurred (fasted 21 hours and longer) the number of glycogen particles decreased in hepatocytes. It is concluded from this study that a good correlation exists between chemical determinations of hepatic glycogen, cytochemistry of glycogen in hepatocytes, fine structure of liver cells, and the fasting state of the animal.
Adrenergic innervation of the rat submandibular and parotid glands. An electron microscopic autoradiographic study of the uptake of tritiated norepinephrine
Authors: Bogart Bruce Ian , De Lemos Carmen L.
Published: February 2005

The adrenergic innervation of the rat submandibular and parotid glands was investigated by monitoring the uptake of H3‐NE by nerve terminals with electron microscopic autoradiographic techniques. Both glands contained nerve bundles in the stroma encompassed by a Schwann cell sheath. Silver grains due to H3‐NE were observed overlying several nerve terminals found in these nerve bundles, while other nerve terminals in the same bundle were devoid of silver grains. In the submandibular gland, adrenergic nerve terminals characterized by silver grains due to H3‐NE were observed in the stroma in close relationship to, but not in direct apposition to parenchymal cells. In the parotid gland, silver grains due to H3‐NE were observed overlying nerve terminals contained within the basement lamina and in close contact with acinar cells.
Rat renal capsule: Presence of layers of unique squamous cells
Authors: Bulger Ruth Ellen
Published: February 2005

Unique squamous cells forming one or more layers are invariably present at the inner border of the rat kidney capsule. The cells frequently surround a space or lumen of irregular contour. The cells appear to be supported by collagenous bundles which run between adjacent cells within groove‐like indentations in a single cell, but the connective tissue components are separated from the squamous cells by a thick basal lamina. The fibrous capsule is bound to the renal parenchyma by loose connective tissue containing fibrocytes, small collagen bundles, and abundant mononuclear cells which are partially surrounded by processes of the fibrocytes.
Fine structure of the ultimobranchial body of the chick
Authors: Isler H.
Published: February 2005

The ultimobranchial bodies of the chick consisted of follicles and cell cords. The follicles were of various sizes and shapes. Their epithelium was simple or stratified, squamous to cuboidal, and contained two cell types. The lumen‐bordering cells had microvilli at their apex, a few long, flat ergastoplasmic sacs, a prominent Golgi, an extensive system of smooth membrane tubules and microvesicles, abundant free ribosomes, no granules and indented nuclei. Their lateral membranes followed a sinuous path and their membrane at the base showed occasional intense pinocytotic activity. Thus these cells appear well differentiated and functionally active, whatever their function may be. The second cell type, never in contact with the lumen, also differed by its abundant granules, the smooth path of its plasma membrane, the smooth outline of its nucleus and the occasional presence of intranuclear vesicles. The cell cords were made essentially of these same granular cells. It was shown histoimmunologically that numerous calcitonin‐containing cells were present in the cell cords; those few present within the wall of the vesicles never bordered on the lumen. It is concluded that the granular cells are producing calcitonin, while the lumen‐bordering cells contribute the holocrine secretion of the vesicle.
Peristaltic contractions of the murine urogenital sinus
Authors: Cunha Gerald R.
Published: February 2005

Urogenital sinuses from 14‐ to 17‐day old embryonic mice were grown in vitro for six days. Fourteen‐day old urogenital sinuses exhibited weak, irregular peristaltic contractions, while in explants from 15‐ to 17‐day old embryos peristaltic contractions were forceful and regular in rhythm. Neither testosterone dipropionate nor Cyproterone acetate substantially influenced contractile activity whereas estradiol was slightly inhibitory. Exposure to cytochalasin‐B resulted in a complete, but reversible inhibition of peristalsis. The initiation of peristaltic contractions correlated well in time with the presumed onset of urine production by the developing kidneys, and it is suggested that these peristaltic contractions may facilitate urine transport from the kndneys to the amnionic cavity.
Stimulation of acinar cell proliferation by isoproterenol in the postnatal rat submandibular gland
Authors: Chang W. W. L. , Barka T.
Published: February 2005

During the postnatal development of the submandibular gland, the stimulation of DNA synthesis and mitosis by a single injection of isoproterenol, measured as the percentage of labeled cells in radioautographs, was dependent on the age of the rat. The drug had no effect on the proliferative activity in two day old rats, but stimulated DNA synthesis in older (7–42 day old) animals. In general, the degree of stimulation was directly related to the proportion of acinar cells and inversely related to the proliferative activity in the gland of control rats. An analysis of various cell types revealed that the stimulation of DNA synthesis in the gland was essentially restricted to the acinar cells in rats older than 14 days of age. In seven day old rats, the acinar cells were not stimulated, but their precursors, the proacinar cells, the terminal tubule cells and the intercalated duct cells were stimulated to synthesize DNA by isoproterenol. This suggested that isoproterenol had an effect on the transformation of precursor cells to acinar cells.
Enhanced mineralization of the tibial epiphyseal plate in the rat following propylthiouracil treatment: A histochemical, light, and electron microscopic study
Authors: Dearden Lyle C.
Published: February 2005

Following treatment with propylthiouracil, most chondrocytes in the reserve and upper proliferation zones in the tibial epiphyseal plate exhibit degenerate ultrastructural morphology. In the extracellular matrix, sulfated mucopolysaccharide is reduced, matrix vesicles are increased both in number and in size, apatite crystals are present in all zones, and mineralization is enhanced.

In post‐treatment recovery, chondrocyte degeneration decreases; however, the extracellular matrix is considerably delayed in returning to conditions comparable to those in corresponding controls and this is indicated by the continued presence of apatite crystals in abnormal locations.

Chondrocyte degeneration, sulfated mucopolysaccharide, and matrix vesicles, are discussed as they relate to the mineralization process.
Lactic dehydrogenase activity in the hair follicles of the stump‐tailed macaque (Macaca speciosa)
Authors: Sasai Yoichiro
Published: February 2005

Lactic dehydrogenase activity was studied in hair follicles from both the bald and hairy regions of the scalp of the stump‐tailed macaque by the application of the method of Lineweaver‐Burk to the histochemistry. There was no difference between terminal and vellus follicles in total lactic dehydrogenase activity. During anagen, the activity was higher in the lower part of the external sheath and was similar to that in the bulbar sac. The activity of the heart‐type lactic dehydrogenase (H‐LDH) was high in the matrix, whereas that of the muscle‐type lactic dehydrogenase (M‐LDH) was high in the external sheath of the lower and upper bulb portions. The activity of M‐LDH in the matrix of terminal hair follicles was extremely low compared with that in vellus follicles. In telogen, however, there was no difference between the two types of follicles.
Cytochemical studies of the maternal surface of the syncytiotrophoblast of human early and term placenta
Authors: Martin B. J. , Spicer S. S. , Smythe N. M.
Published: February 2005

Light microscopic studies using a battery of basic dye stains combined with sialidase and hyaluronidase digestions indicated that the extensive basophilia of the maternal surface of the placental syncytium largely results from the presence of a non‐sulfated mucosubstance specifically identified as hyaluronic acid. Ultrastructural examination of dialyzed iron (DI) stained specimens revealed that DI‐positive filaments observed along the syncytial surface were removed by hyaluronidase digestion. Staining with the lectins, Concanavalin A or lentil bean hemagglutinin produced an intense and periodic pattern of staining that was not enzyme labile. Incubation of tissue sections in the enzyme solutions or control buffers allowed the lectins to penetrate the syncytial plasma membrane and stain material within the endoplasmic reticulum presumed to be human chorionic gonadotropin. The maternal surface exhibited essentially no reactivity for acid phosphatase but showed strong alkaline phosphatase activity with a periodic staining pattern. With each of the techniques used there was variability in the intensity of staining in different regions along the maternal surface, suggesting that functionally different zones may be identified cytochemically. Only minor differences were observed in the cytochemical reactivity of early compared with term placenta.
Fine structure of myogenesis and elastogenesis in the developing rat lung
Authors: Collet A. J. , Biens G. Des
Published: February 2005

The processes of myogenesis and elastogenesis are studied under the electron microscope in developing rat lungs, throughout the 15th to the 21st days of the gestation period. Myogenesis follows bronchial development and stops at the beginning of the alveolar zone, at the primitive respiratory bronchiole level. Elastogenesis appears at the periphery of the myoblasts during their differentiation. Thin myofilaments only are observed within myoblasts and their formation precedes that of dense bodies.

Primitive respiratory bronchioles are visible on the 19th day and are characterized by an early elastogenesis carried out by fibroblasts. At this stage there are no elastic fibers around the alveolar tubules. Then (20th and 21st days) elastogenesis spreads throughout the alveolar zone, accompanying the alveolization process. Peculiar morphological characteristics of the pulmonary fibroblast are underlined. In relation to both muscular cells and fibroblasts the fine structural features of the rat pulmonary elastogenesis are identical to those previously described in other organs. Myoblasts and fibroblasts probably originate from the same primitive mesenchymal cell. Their differentiation depends on the zone where they are located. The relations between connective tissue and epithelial cell differentiation suggest a control of lung development by means of reciprocal induction processes.
An electron microscopic investigation of the surface coat of visceral yolk sac endoderm cells in the guinea pig
Authors: King Barry F.
Published: February 2005

Guinea pig visceral yolk sac endoderm cells are known to absorb proteins from the uterine lumen by the process of pinocytosis. Since previous studies have shown that the first step in protein absorption is the binding of the protein to an extracellular material on the surface of pinocytotic invaginations, it was thought that the surface coat might possess receptor sites for molecules which are subsequently absorbed. This study investigates the nature of the surface coat of the endoderm cells using ruthenium red, alcian blue/cetylpyridynium chloride‐lanthanum and concanavalin A‐peroxidase procedures. Results using these methods showed the presence of a surface coat on both the microvilli and pinocytotic invaginations. The coat on the pinocytotic invaginations was thicker than that on the microvilli. Concanavalin A receptor sites were separated from one another on the cell surface. Since only those pinocytotic invaginations which were open to the surface at the time of fixation would be “stained” by these methods, the procedures also show that the numerous tubules and vesicles in the apical cytoplasm do not all form an intercommunicating labyrinth open to the surface, even though most of them are part of a related functional system. The results indicate that the surface coat contains mucopolysaccharide components. In addition, concanavalin A receptor sites are present which are probably oligosaccharides associated with a glycoprotein component of the apical cell membrane.
A new fixation technique for the electron microscopic study of pulmonary surfactant
Authors: Callas Gerald
Published: February 2005

Previously reported methods for the electron microscopic visualization of the surface layer (surfactant) of the alveolar lining cells have proved less than ideal and further development in this area is needed. Two percent agar in glutaraldehyde injected into the respiratory tree concurrently with vascular perfusion seems to offer some real advantage over techniques described by others. The combination of glutaraldehyde and agar acts both as an obstruction that holds surfactant against the alveolar surface and as a fixative due to the buffered glutaraldehyde component. This technique offers more consistent results and more extensive demonstration of the surfactant layer over the alveolar surface.
The fine structure and innervation of the cushion veins of the human nasal respiratory mucosa
Authors: Cauna Nikolajs , Cauna Dzidra
Published: February 2005

Cushion veins of the human nasal lining were studied in eight patients of both sexes ranging in age from 11 to 59 years. It was found that the subendothelial cushions were part of the tunica media and consisted of smooth muscle cells, collagen and elastic fibers and occasional fibrocytes. The muscle fibers of the cushion nearest to the endothelium were circular. They extended processes towards the endothelium through gaps in the endothelial basement membrane and formed appositional junctions with the endothelial cells. The rest of the cushion consisted of longitudinal muscle fibers. The sarcoplasm of the muscle cells was characterized by large areas filled with vesicles of various sizes. In addition, these cells possessed cytoplasmic processes which were devoid of a basement membrane and which did not show the regular structure of sarcoplasm. The subendothelial cushion possessed a rich, intrinsic nerve supply of adrenergic and cholinergic axons. It is suggested that the cushion veins regulate the drainage of the cavernous tissue and are under nervous and humoral control. The increase in girth of the subendothelial cushion is effected by contraction of the longitudinal muscle cells and probably by uptake of extracellular fluid by means of the specialized cytoplasmic processes. The single layer of circular muscle cells situated between the endothelial lining and the longitudinal musculature, may provide protection to the endothelium against distension when the cushion expands.
Junctional complexes in the preimplantation rabbit embryo
Authors: Hastings Richard A. , Enders Allen C.
Published: February 2005

The morphology and development of junctional complexes between blastomeres of the preimplantation rabbit embryo were investigated using several approaches. Electron microscopic examination of embryos stained en bloc with uranyl acetate, and the study of junction permeability using horseradish peroxidase and lanthanum nitrate provided information on structure, intermembrane spacing and permeability of the junctional complexes. In addition, the freeze fracture technique was used with day 5 and day 6 blastocysts, since the large size of these embryos facilitated use of this method. These experiments showed that although rudimentary junctions were present between blastomeres of the early cleavage stages, effective tight junctions were not present until the blastocyst stage. Electron microscopic examination of thin sections revealed apical foci of membrane approximation or “fusion” between trophoblast cells by day 4. Freeze fracturing revealed a lattice of interconnecting ridges (on the A face) and grooves (on the B face) in the apical region between trophoblast cells of the day 5 blastocyst. This lattice formed a continuous band along the apical margin of each cell, and therefore constituted a zonula occludens. The zonula occludens of the day 5 blastocyst averaged 2–3 ridges per lattice, while day 6 blastocysts had lattices that averaged 5–6 ridges. Also seen in the freeze fracture replicas from the day 5 and day 6 blastocysts were local accumulations of intramembranous particles on the A face. These particles were often observed in aggregates similar to those of previously described gap junctions. It could not be determined whether these small regions of particles were true gap junctions or a possible primitive form of gap junction because the complementary pitted surfaces (B face pits) were not demonstrated.
Alterations in the fine structure of hepatocytes in hyperthyroid rats
Authors: Callas Gerald , Cannon M. Samuel
Published: February 2005

Ultrastructural investigation of liver from ten radiothyridectomized adult male albino rats, made hyperthyroid by administration of desiccated thyroid for eight to ten weeks, revealed changes in hepatic organelles, but no differences between centrilobular, midzonal and periportal hepatocytes of a single lobule. The mitochondria were enlarged with an increase in matrix density, but no increase in number of mitochondria or alterations in membranes or criste was observed. The smooth endoplasmic reticulum appeared slightly increased and dilated in treated rats, while stacked cisternae of the rough endoplasmic reticulum were seldom seen. Large vacuoles, which often contained follicular material and frequently opened into the spaces of Disse, were observed at the periphery of hepatocytes. The vacuoles may arise from invaginations of the cell membrane along these spaces to increase the surface area and to act as channels for liver metabolites. Moreover, in hyperthyroid rats hepatic glycogen was uniformly depleted. Whether these changes were a primary effect of thyroid hormone or secondary to metabolic alterations is unclear.
The variable fine structure of elastin visualized with verhoeff's iron hematoxylin
Authors: Brissie R. M. , Spicer S. S. , Thompson N. T.
Published: February 2005

Verhoeff's iron hematoxylin (VIH) followed by lead citrate (LC) applied to epoxy thin sections stained the dense component of elastic fibers heavily and the peripheral microfibrillar component lightly in guinea pig trachea and mouse testis fixed with a glutaraldehyde‐osmium tetroxide sequence. This method stained large fimbriated fibers beneath tracheal epithelium, small fibers and stacked aggregates thereof in the deep lamina propria, cartilage and adventitia of the trachea and large stacked fibers in the fibroelastic band of the trachea. Fibers of the fetus differed from those of the adult, especially in the subepithelial elastic lamina of the trachea. Elastic fibers were intimately associated with fibroblasts and particularly slender fibroblast processes in tracheal stroma and with chondrocytes in tracheal cartilage. Fibroblasts associated with elastic fibers in the tracheal subepithelial lamina propria were often closely bordered by eosinophils, mast cells, or monocytes. Occasional mast cells extended slender processes around elastic fibers in the subepithelial lamina propria. In mouse testis and in many regions of the trachea, small elastic fibers were identified which were below the limits of resolution for the light microscope and were not apparent at the ultrastructural level in routinely stained thin sections.
Ultrastructural and histochemical study of the adrenal medulla in normal and cold‐stressed syrian hamsters
Authors: Al‐Lami Fadhil , Farman Naziha
Published: February 2005

The effect of 24 and 48 hours' cold stress on the hamsters' adrenomedullary follicles and on the medullary ATPase activity was studied by light and electron microscopy. Only norepinephrine cells were depleted after this stress, and exocytosis seemed to be the mechanism involved in the release of catecholamine. Follicles containing these cells expanded and their lumina became narrow. A few other cellular and follicular changes also occurred and are described.

ATPase activity was apparent in control organs along the endothelial linings, in neural elements and macrophages, and in approximately 40% of the linings of follicular lumina. Cold stress did not alter this pattern.

These results have been compared with previous findings and the possible functions of the follicular lumina are discussed. It is concluded that they are unlikely sites for catecholamine storage or release.
Localization of cells retaining 3H‐estradiol in the forebrain of rabbits
Authors: Anderson Conwell H.
Published: February 2005

Ovariectomized rabbits received 3H‐estradiol via an ear vein and were killed one hour later. Autoradiograms were prepared and exposed up to six months. Labeled cells, as indicated by many silver grains over the nucleus of a neuron, were found in many nuclei of the brain. Thus, the bed nucleus of the stria terminalis had labeled cell bodies. The stria terminalis leads into the medial preoptic area where great numbers of cells concentrated the estrogen. Farther into the hypothalamus the labeled cells were numerous in the ventromedial and arcuate nuclei. Other locations with labeled cells were the lateral septal nucleus and nucleus accumbens septi, the periventricular preoptic nucleus, anterior hypothalamic nucleus, nucleus supraopticus diffusus, posterior hypothalamic nucleus, and premammillary nucleus. The labeled cells could be followed into the central gray surrounding the aqueduct of Sylvius. The amygdaloid nuclei, and in particular the medial amygdaloid nucleus, had labeled cells as did the most ventral posterior part of the hippocampal cortex. The results are discussed in comparison with those in the rat, and with reference to physiologic data.
The effects of various fixative‐buffer combinations on lung fine structure
Authors: O'Hare Karen Hitchcock , Braunschweig Ralph Jon
Published: February 2005

A variety of fixatives, buffers and fixation procedures were compared in rat and squirrel monkey lung in an attempt to preserve optimally both the cytologic details of pulmonary parenchyma as well as the acellular alveolar lining layer. In initial experiments utilizing the fixative of Ito and Karnovsky ('68), an electron‐dense deposit was observed on the alveolar surface. Experiments were carried out in an attempt to determine what component of this fixative was responsible for the reaction product observed. In addition, immersion fixation of tissue blocks was compared to the whole lung fixation method of Kikkawa ('70). Kikkawa ('70) achieved excellent preservation of the acellular alveolar lining layer by such a fixation technique.

In all lungs examined, whenever a phosphate buffer was utilized with primary aldehyde fixation, an electron‐dense precipitate was observed on the luminal surfaces of the type I and II pulmonary epithelial cells. Additional sites of reaction product were pinocytotic vesicles of the type I cells and membranous arrays within the alveolar lumen. Such deposits were never observed when a sodium cacodylate buffer was used. No such granules were observed in areas of lung where the acellular alveolar lining layer had been preserved.

The implications of these findings with regard to lung histochemical procedures and the possible relationship of these phosphate buffer‐dependent granules to the surfactant system are discussed.
Granular cells in the juxtaglomerular apparatus in perinatal rats
Authors: Eguchi Y. , Yamakawa Michiko , Morikawa Y. , Hashimoto Y.
Published: February 2005

Granular cell indices (GCI; Dunihue and Robertson, '57) in kidneys of fetal and newborn rats were determined by examining sections stained with Bowie's technique. Some fetuses were delivered prematurely by Caesarean section a day earlier than the expected delivery, and were then nursed by a foster mother. Similarly, postmature Caesarean newborn rats were obtained; retention one day beyond the normal gestation was induced by maternal progesterone injections.

The GCI was strikingly increased within a day after birth, followed by an immediate decrease thereafter. This was also observed in both premature and postmature newborn rats. It seems that this temporary increase of the GCI is not attributable solely to the age of rat, but follows only the separation from the maternal environment.
The postnatal development of high‐endothelial venules in lymph nodes of mice
Authors: Van Deurs B. , Röpke C.
Published: February 2005

The postnatal development of high‐endothelial venules (HEvenules) in popliteal lymph nodes of normal and athymic mice was studied by light and electron microscopy.

In the normal mice, undifferentiated postcapillary HEvenules are already present at birth. During the first four days after birth, ribosomes and mitochondria in the endothelial cells of the venules become more numerous, and the endoplasmic reticulum and in particular the Golgi complexes enlarge. At day four lymphocyte diapedesis through the venules becomes apparent. From the tenth day the HEvenules are structurally mature. However, diapedesis activity still increases till about a month postnatally. In mice with congenital aplasia of the thymus (nude mice) and in neonatally thymectomized mice the development of the HEvenules is similar to that in normal mice. In the athymic mice both lymphocytes and granulocytes migrate through the walls of the HEvenules. However, the blood level of lymphocytes in these mice is far below the value in normal mice.

It is concluded that the development of the HEvenules during the first month of life is independent of the blood level of lymphocytes.
The immune system of the nine‐banded armadillo (dasypus novemcinctus, linn)
Authors: Purtilo David T. , Walsh Gerald P. , Storrs Eleanor E. , Gannon Carman
Published: February 2005

The armadillo is rapidly emerging as an animal for biomedical research. A morphological study of the immune system of the armadillo was undertaken to try to demonstrate a possible defect in the morphogenesis of the lymphoid organs that could account for their susceptibility to leprosy. Blood from 20 domesticated adult armadillos revealed lymphocytes predominated among circulating leukocytes in the majority of animals, whereas in wild animals neutrophils predominated. Necropsies revealed well‐developed thymus glands and the thymus‐dependent areas in lymph nodes and spleens contained abundant lymphoid cells. Hence, we conclude that the susceptibility of the armadillo to leprosy cannot be explained on a morphological basis.
Malorientation of mitotic figures in the early lens rudiment of aphakia mouse embryos
Authors: Zwaan Johan , Kirkland Barbara M.
Published: February 2005

In early embryonic epithelia most cell divisions are oriented with their cleavage furrows perpendicular to the free surface of the tissue. This results in the generation of two daughter cells, which are equivalent with regard to their apical surface. Mitotic figures, in which the long axis through the centers of the chromosome plates (chromatin masses) is perpendicular to the surface, are seen only occasionally.

The lens placode and early lens cup of mouse embryos homozygous for the gene aphakia show significantly greater numbers of maloriented mitoses than normal control lenses. The axis connecting the centers of the chromosomal plates is frequently perpendicular or oblique to the surface. This may result in the production of daughter cells, which are unequal as far as their position at the tissue surface is concerned.

Later, the lumen of the mutant lens vesicle fills up with cells, which are apparently released from the lens epithelium. Further development of the lens and the eye is grossly disturbed.

The release of these cells may be a consequence of the malorientation of their divisions, or both may be the result of a defect in the spatial orgnization of the lens tissue, possibly due to abnormal cellular adhesion.
Kinetics of pulmonary epithelial proliferation during prenatal growth of the mouse lung
Authors: Kauffman Shirley L.
Published: February 2005

Autoradiographic methods were used to analyze cell kinetics in peripheral epithelium of the fetal mouse lung, days 15‐18. The 3H labeling index decreased in proportion to increases in fetal lung and body weight from day 15 to day 18. Cell‐cycle determination estimated from the percent of labeled metaphases at intervals after 3H thymidine injection showed the shortest cell‐cycle time (12.25 hours) on day 15 during the precenal stage of growth. Total cycle time (Tc) increased by approximately one hour on each subsequent day. Between days 15 and 16 Tc increased due to a 1‐hour increase in the post mitotic interphase (G1); thereafter increases in Tc could be ascribed almost entirely to lengthening of the DNA synthetic period. A comparison of cell‐cycle time in central and peripheral tubules of the same lungs on day 15 showed a slower cell cycle in the central tubules than in the peripheral branches. An estimate of the growth fraction (GF) on each day based on calculated and observed cell‐cycle times showed that GF was 1 on days 15 and 16, decreasing to 0.69 on day 17 and 0.27 on day 18. Thus cell‐cycle time increases with lung maturation and it increases from peripheral to central zones of the bronchial tree. The greater part of the observed decline in growth rate as the prenatal phase of growth is completed was due largely to a decrease in the fraction of cells in the cell cycle.
Morphological studies on the synthesis of secretory granules in convoluted tubules of mouse submandibular gland
Authors: Kaiho Masayoshi , Nakamura Toshikazu , Kumegawa Masayoshi
Published: February 2005

The synthesis of zymogen‐like secretory granules in convoluted tubules of mouse submandibular gland (SMG) was investigated by histometry, light microscopy and electron microscopy. In normal males secretory granules in the SMG increased greatly from 25 days after birth and reached a maximum level 50 days after birth. Castration of adult male mice markedly decreased the level, but it was completely restored by testosterone administration. A parallel was found between change in the granule level and the amount of rough endoplasmic reticulum (RER) in the convoluted tubular cells during development or after various treatments. Development of the Golgi apparatus was also observed in the cells when the granules increased. Both the increase in the granules and in the RER induced by testosterone were prevented by actinomycin D or puromycin. These results indicate that the granule contents are synthesized on the RER under the control of testosterone, and then condensed in the Golgi apparatus.
Morphogenesis of the carpal elements in the regenerating forelimb of adult Notophthalmus viridescens viridescens
Authors: Benzo Mary M. , Benzo Camillo A. , Manner Harold W.
Published: February 2005

This study is concerned with the morphogenesis of the carpal elements in the regenerating forelimb of the adult newt. Blastema cells surrounding the remnant bony stumps begin to differentiate into cartilage on the twentieth post‐amputation day. Subsequently, masses of cartilage build up from the radial and ulnar stumps. The radial mass is larger and differentiates more rapidly than the ulnar mass. By the fifty‐fifth post‐amputation day, the eight basic carpal elements are formed, with fusion of two of the units, intermedium with ulnare, occurring by the seventieth day. The complexed regenerate possesses the seven carpal elements characteristic of the normal adult limb. The present results show that during limb regeneration in the adult newt the carpal elements are restored to their original number and position and that the pattern of such carpal differentiation proceeds in a proximodistal direction influenced by the stump remnants of the radius and ulna.
Cellular mechanisms involved in cyclic stromal renewal of the uterus. III. Cells of the immune response
Authors: Padykula Helen A.
Published: February 2005

The principal cell types associated with the humoral immune response (monocyte‐macrophages, lymphocytes, and plasma cells) are numerous in the endometrial stroma of the uterus during the first four postpartum days in two types of mammals, the marsupial North American opossum and the eutherian albino rat. This transient cellular differentiation coincides with the physiologic period of rapid uterine regression which includes massive reduction in the amount of extracellular stromal material. In addition, heterophils and eosinophils, cell types also known to be associated with phagocytic and immunologic activity, appear in the stroma during the first two postpartum days; their presence may, however, be associated more directly with the postpartum estrus that occurs on day 1 postpartum than with endometrial regression. Thus, the five cell types, which are known in pathologic conditions to be components of an inflammatory response to a foreign antigen, are conspicuously present in the normal regressing endometrium. Furthermore, there is ample ultrastructural evidence of frequent macrophagic‐lymphocytic interaction, transformation of lymphocytes, and active secretion by plasma cells during this early postpartum period.

An hypothesis has been derived by uniting this new description of endometrial stromal cell differentiation with the existing literature on uterine collagenase activity, an important feature of postpartum regression (reviews by Gross, 1974; Harris and Krane, 1974). It is based on the assumption that during regression the extracellular action of neutral collagenase (and possibly other extracellular proteases) release new antigenic sites in proteins located in the ground substance. In the case of collagenase, these transient antigenic sites would arise at the locus of enzymic cleavage as well as from the subsequent denaturation of the fragments of the collagen molecule. This endogenous antigenic stimulus would be strong and temporary, and would lead to the cellular manifestations of the transient humoral immunologic response which are evident in the regressing stroma of these two mammals. This humoral immune reaction may be one of the regulatory mechanisms involved in the cyclic renewal of the extracellular compartment of the uterine stroma.
Mechanical properties and histology of cortical bone from younger and older men
Authors: Evans F. Gaynor
Published: February 2005

Tensile breaking load, strength, strain, modulus of elasticity and density plus the histological structure at the fracture site, were determined for 207 standardized specimens of cortical bone from the embalmed femur, tibia, and fibula of 17 men from 36 to 75 years of age. The men were divided into a younger group (41.5 years old‐avg) and an older group (71 years old‐avg). Specimens from younger men had a greater average breaking load, strength, strain, modulus and density than those from older men. The percentage of spaces in the break area was greater in specimens from older men, but specimens from younger men had a slightly greater percentage of osteons, osteon fragments, and interstitial lamellae. The number of osteons/mm2 and of osteon fragments/mm2 was greater in specimens from older men but the average area/osteon and area/osteon fragment was greater in specimens from younger men. Thus, there are quantitative and qualitative differences in the histological structure of bone from younger and older men. Differences in the tensile properties of bone from younger and older men can be explained by histological differences in the bone.
Recovery of rat prolactin cells following cessation of estrogen treatment
Authors: Shiino Masataka , Rennels Edward G.
Published: February 2005

Estrogen treatment for one month in female rats caused some regression of somatotrophs, but induced an increase in the number of prolactin cells and caused these cells to hypertrophy. These stimulated prolactin cells showed extensive development of the granular endoplasmic reticulum which was often arranged in concentric whorls (Nebenkern). Most of the prolactin cells contained a small number of mature granules which were smaller in size than those of prolactin cells in control animals. These prolactin granules were round in sectioned profile and closely resembled the secretory granules of normal somatotrophs.

At five and ten days after the suspension of estrogen treatment, many prolactin cells contained numerous secretory granules of various sizes ranging from 150–500 nm. Only occasional granules in these cells were as large as 750 nm, and only the largest of the granules exhibited the irregular shape which is characteristic of mature granules in normal prolactin cells. Fifteen days after the cessation of estrogen injection most prolactin cells exhibited numerous secondary lysosomes. At this time the mature secretory granules were similar in morphology to those of normal prolactin cells.

From the fact that the somatotrophs appeared not to be stimulated by the estrogen treatment we find it difficult to accept the concept that somatotrophs cna undergo transformation into prolactin cells.
The skin of the giraffe
Authors: Dimond Robert L. , Montagna William
Published: February 2005

The skin of the giraffe has the same general histological structure as that of other mammals, but there are notable features. The skin is heavily pigmented with the epidermis, pilary canals, and the outer cell layer of the apocrine duct richly melanized. Furthermore, melanotic dendritic cells are frequently found in the sebaceous glands, the entire length of the external root sheath, and the secretory tubules of the apocrine glands. The thick skin has a papillary dermis that extends to just beneath the secretory coils of the apocrine glands and bulbs of hair follicles and an equally thick reticular layer below these structures. The hair follicles do not grow in clusters, and with some regional variations, have associated sebaceous glands, apocrine glands, and arrectores pilorum muscles. Only the large hairs have a prominent medulla. In such specialized regions as the eyelids, nose, and lips, the apocrine glands are surrounded by cholinesterase‐reactive nerves but the glands on the general body surface are not. The only specialized nerve receptors are hair follicle end organs found on every hair of the eyelids, nose, and lips, but only rarely elsewhere.
A light and electron microscopic investigation of the hepatic parenchyma of the adult newt, Notophthalmus viridescens
Authors: Haar Jack L. , Hightower James A.
Published: February 2005

This light and electron microscopic study demonstrates that the liver of the adult newt, Notophthalmus viridescens, consists of a mass of hepatocytes interrupted by blood sinusoids which allow blood to percolate through the parenchyma. The plates separating adjacent sinusoids are usually two or more cells thick and the bile canaliculi lie between 2–6 neighboring cells. Fine structural characteristics of hepatocytes include abundant lipid and glycogen inclusions. Melanophores with developing melanosomes are situated throughout the hepatic parenchyma.
Localization of transferrin on the surface of the human placenta by electron microscopic immunocytochemistry
Authors: King Barry F.
Published: February 2005

During the course of gestation, a large amount of iron is transferred rapidly and unidirectionally from mother to fetus across the placenta. It has been postulated that one of the first steps involved in placental iron transfer involves binding of the maternal transferrin‐iron complex to the surface of the placenta and the subsequent removal of iron and release of transferrin back into the maternal circulation. To determine if transferrin is present on the surface of human placental villi, two different immunocytochemical methods have been used: (1) an unlabeled antibody, peroxidase‐antiperoxidase (PAP) method utilizing rabbit antiserum to human transferrin, goat anti‐rabbit IgG and rabbit peroxidase‐antiperoxidase complex or; (2) a peroxidase‐labeled antibody method utilizing goat antiserum to human transferrin and peroxidase‐conjugated rabbit anti‐goat IgG. The peroxidase was then localized by incubation in a diaminobenzidine‐hydrogen peroxide medium. Examination of the tissue in the electron microscope revealed the reaction product deposited as discrete patches or particles on the microvillous surface of human syncytial trophoblast. Controls using non‐immune serum or an antiserum adsorbed with purified human transferrin showed no reaction product on the surface. The results provide morphological confirmation for the presence of transferrin on the surface of human syncytial trophoblast lining the maternal blood spaces.
A correlative histofluorescence and light microscopic study of the formation of the sympathetic trunks in chick embryos
Authors: Kirby M. L. , Gilmore S. A.
Published: February 2005

The appearance and development of the primary and secondary sympathetic trunks in staged chick embryos was studied using the Falck‐Owman histochemical method for the demonstration of primary monoamines. The earliest appearance of catecholamine (stage 20) was in individual fluorescent cells located in the region of the dorsal root ganglia about two stages prior to the formation of primary trunk aggregates. These cells are believed to be sympathetic precursor cells and correspond to formaldehyde‐induced fluorescent cells observed in recent explantation experiments. Aggregates of fluorescent cells had formed bilaterally dorsolateral to the aorta at stage 22. These aggregates became continuous to form primary trunks by stage 24. The secondary sympathetic trunks were first seen in stage 25 and appeared to form at least partially by dorsal migration of cells from the primary trunks. Fluorescent cell processes were first observed at this stage. Secondary trunk formation was essentially complete by stage 28, and the primary trunks had become small and discontinuous. Definite rami communicantes could be observed by the early part of stage 28 in silver preparations. The significance of the development of two successive trunks in avians is discussed.
Ultrastructure of gallstones produced in mice fed a high cholesterol diet
Authors: Saland L. C. , Napolitano L. M.
Published: February 2005

Mice fed a high cholesterol‐cholic acid diet for two to six months develop gallstones; these were studied by transmission electron microscopy after glutaraldehyde‐digitonin fixation. Examination of the contents of mouse gallbladders presents views of layered structures and surrounding amorphous material. We interpret these images of gallstones to suggest that they may arise by cohesion of material rich in cholesterol to form more ordered structures. Gallbladder contents of mice fed the diet for five to six months were found to contain occasional crystals and rectangular areas similar to those observed in thin sections of human gallstones (unpublished observations). Recent findings that human gallstones can be dissolved with chenodeoxycholic acid are discussed, with reference to their applicability to studies of gallstones in mice.