bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunocytochemical evidence for anti‐LHRH and anti‐ACTH activity in the “F” antiserum
Authors: Clayton Claudia J. , Hoffman Gloria E.
Published: February 2005

An antiserum which has previously been thought to be specific for LHRH‐ like immunoreactive material was shown to contain two populations of antibodies, one demonstrating anti‐LHRH activity and the other anti ‐ACTH (1‐24) activity. In rat and mouse, ACTH(1‐4)‐like immunoreactive substance is present in perikarya within the basal hypothalamus and in fibers in arcuate, periventricular and dorsomedial nuclei. LHRH‐like immunoreactivity is present in fibers within the median eminence and arcuate nucleus, in a few fibers running along the ventral border of the hypothalamus, and in a small number of cell bodies within the medial basal hypothalamus.
Development of the renal corpuscle during metamorphosis in the lamprey
Authors: Youson John H. , Ooi Eng C.
Published: February 2005

The renal corpuscle of the adult lamprey, Petromyzon marnus L., is formed during the programmed period of metamorphosis. Development is initiated early in this metamorphic period and is marked by the synchronous formation and growth of rudimentary nephron units (RNU) from a longitudinal cord of nephrogenic tissue extending from the posterior tip of the degenerating larval kidney to the cloaca and connected to the peritoneal epithelium. Detachment of the RNU from the peritoneum involves autolysis and cell death and is accompanied by their branching into five or six hexagonally‐arranged nephrons which radiate from the original point of attachment.

Differentiation of the epithelial cells at the proximal ends of the nephrons is preceded by the widening of lateral intercellular spaces, the formation of tubular lumina (primitive urinary spaces), the loss of apical cell junctions, and the development of a capillary network with its associated mesangium. With the extension of the capillaries and mesangium between the proximal ends of adjacent undifferentiated nephrons, visceral epithelial cells (podocytes), with long cell processes (trabeculae) and slit membranes, make their appearance.

The urinary spaces resulting from this form of development are lined by the epithelium of the dilated ends of the nephrons (nephric capsules). The cells of these capsules differentiate mainly into podocytes, but a few parietal cells connect to the draining tubule. This method of development explains the unique form of the renal corpuscle in the adult lamprey. Despite the type of morphogenesis, this renal corpuscle possesses the fine‐structural features seen in the renal corpuscles of other vertebrates.
Successful maintenance of suckling rat ileum in organ culture
Authors: Shields Helen M. , Yedlin Steven T. , Bair Frank A. , Goodwin Carol L. , Alpers David H.
Published: February 2005

Ileum from rats 4, 9, 11, 12, and 15 days old can best be maintained for 24 hours in a system using Hanks' Balanced Salt Solution without fetal calf serum, at 25°C and 21% O2. Suckling rat duodenum and jejunum were difficult to maintain well for 24 hours in this system or a variety of other systems that were tried. A temperature of 37°C hastened deterioration of duodenum, jejunum or ileum. With ileum, 3H‐thymidine and 14C‐leucine were increasingly incorporated into DNA and protein over the 24‐hour period. Light microscopy, as well as scanning and transmission electron microscopy, showed very good preservation of the ileum after 24 hours. The addition to the medium of hydrocortisone, 1 μm, and thyroxine, 0.01 μm, alone or in combination, did not change DNA or protein synthesis, or morphology, possibly because of the relatively short (24 hour) time period. Our organ culture system emphasizes the differences between suckling rat ileum and the rest of the intestine, and provides a new tool for evaluating, over a 24‐hour period, the developing rat small intestine.
Observations on closure of the neuropores in the chick embryo
Authors: Schoenwolf Gary C.
Published: February 2005

Neuropore closure was studied in chick embryos by light and electron microscopy. Surface ectoderm reflects over the crests of the neural folds at all craniocaudal levels, merging with the neural ectoderm lining the neural groove. Apices of surface ectodermal cells have an essentially identical morphology prior to approximation of folds, both within the presumptive fusion sites and more laterally. Cells of these areas have slightly convex profiles exhibiting few cellular protrusions. Each neural fold contains a superficial half, composed of neural ectoderm covered by surface ectoderm, and a deep half consisting entirely of neural ectoderm. Initial contact between folds usually occurs near the junction between these halves in cranial regions, but is restricted primarily to surface ectoderm at caudal levels. Subsequent fusion of folds at all levels involves both ectodermal layers. Cellular protrusions and small, morphologically unspecialized intercellular junctions often interconnect cells of apposed folds in areas undergoing fusion. The anterior neuropore closes at stages 10–11, but fusion of folds in this region is not completed until stages 13–14. Fusion occurs dorsoventrally in this area and is more advanced internally than externally. Numerous pleomorphic inclusions and a few apparently necrotic cells are present in areas bordering the anterior neuropore. The posterior neuropore closes at stages 12–13 and fusion is completed in this region during stages 13–14. The caudal end of the posterior neuropore closes dorsal to the developing tail bud. Several morphological features of this closure may at least partially account for the high susceptibility to myeloschisis localized specifically at caudal spinal cord levels.
The effect of estrogen on epithelial cell proliferation and differentiation in the crypts of the descending colon of the mouse: A radioautographic study
Authors: Hoff Martin B. , Chang William W. L.
Published: February 2005

The regulatory role of estrogen on cell population kinetics in the descending colon was studied in intact female and ovariectomized mice. In the colonic crypts from intact mice, the crypt size (the number of epithelial cells per crypt column) and the proliferative activity of epithelial cells fluctuated slightly during the estrous cycle. Peak cellularity per crypt column was exhibited during estrus and early diestrus, whereas peaks in labeling index were seen during estrus and late metestrus. While the population size of mucous cells showed a minimal variation, the number of proliferative vacuolated cells per crypt column varied inversely with that of differentiated columnar cells during estrous cycle. The vacuolated cells were increased in number in the preovulatory phase and the columnar cells in the postovulatory phase.

Three weeks after bilateral ovariectomy, the colonic crypt appeared to reach a new steady state, which was characterized by a small crypt size, a decrease in the number of differentiated cells, an increase in the relative number of proliferative cells and a relative increase in the proliferative activity of the crypt as compared to intact mice.

When ovariectomized mice were treated with estrogen, the number of 3H‐thymidine‐labeled cells in the crypt was decreased as compared to untreated ovariectomized mice, the decrease being greater after a single injection than after multiple injections of estrogen, and the vacuolated‐columnar cell line being affected more than mucous cell line. Meanwhile, the crypt size as well as the population size of differentiated cells in the crypt failed to return to normal after estrogen treatments. Thus, estrogen did not promote differentiation of epithelial cells in the crypt.
The longitudinal orientation of structures in the subendothelial space of rat aorta
Authors: Buck Robert C.
Published: February 2005

The aortas of rats were sectioned parallel to the endothelial surface for the purpose of studying the orientation of structures in the endothelium and subendothelial space relative to the long axis of the aorta. Microfilament bundles within endothelial cells, and the associated anchoring filaments of the subendothelial space, lay parallel to the long axis. Other filamentous structures of the subendothelium, namely, the bundles of very fine microfibrils and the somewhat larger elastic fibers, also showed a generally longitudinal orientation, although they frequently deviated from this arrangement, and were not perfectly straight. Another group of filaments in the deepest part of the subendothelial space lay in the transverse axis of the aorta. These filaments appeared to represent the most superficial component of the internal elastic lamina.

In addition to the longitudinally orientated fibrillar structures, the subendothelium also contained longitudinal cytoplasmic folds, or rugae, projecting from the deep surface of the endothelial cells.

It is concluded that contact‐guidance by structures having a pronounced longitudinal orientation within the subendothelial space may be responsible for creating the longitudinal arrangement of smooth muscle cells seen in this layer of the arterial wall with aging, and with certain types of pathological change.
Differential response of myofibrils and 10‐nm filaments to a cocarcinogen
Authors: Toyama Y. , West C. M. , Holtzer H.
Published: February 2005

Multinucleated myotubes containing large numbers of striated myofibrils and large numbers of longitudinally‐oriented 10‐nm filaments were treated with the cocarcinogen phorbol‐12‐myristate‐13‐acetate (PMA) for 24, 48 or 72 hours. The inhibitory effects of PMA on the accumulation of myofibrils was evident within 24 hours, and by 72 hours virtually all striated myofibrils had disappeared. In contrast, the density of the 10‐nm filaments was greatly enhanced in these myofibrildepleted myotubes. These effects were not due to a generalized cytotoxicity, for PMA stimulated the replication of the presumptive myoblasts and fibroblasts present in these cultures. 24 hours after removing the PMA, these myotubes assembled a new set of striated myofibrils and the density of 10‐nm filaments diminished proportionately.
The secretion of mullerian inhibiting substance by cultured isolated sertoli cells of the neonatal calf
Authors: Price J. Michael
Published: February 2005

Sertoli cells have been isolated from the newborn calf testis using a combination of mechanical and enzymatic disruption. Testicular fragments, previously chopped into 1‐mm pieces, are digested in an enzyme mixture consisting of hyaluronidase, collagenase, trypsin and DNAse, followed by a second digestion in trypsin and DNAse. Isolation of the resulting cellular fractions by sedimentation with unit gravity produces an aliquot of Sertoli cells which is over 95% pure when examined by light and electron microscopy. Cultures of these cells grow rapidly and produce Mullerian Inhibiting Substance as evidenced by their ability to cause the involution of the Mullerian duct of the female fetal rat when co‐cultured in an organ‐culture assay system.
Scanning electron microscopy of the subarachnoid space in the dog: Evidence for a non‐hematogenous origin of subarachnoid macrophages
Authors: Merchant Randall E. , Low Frank N.
Published: February 2005

Injection of viable BCG into the subarachnoid space of immunized and non‐immunized dogs produced a 10‐fold increase in the populations of pial free cells. In immunized animals injected three days previously with BCG, stereoscopic SEM revealed that many pial cells had rounded up and were protruding into the subarachnoid space. With continued rounding these cells took on amoeboid characteristics, with shapes that suggested a capacity for cell movement. Internally, these pial cells possessed an increased volume of perinuclear cytoplasm and organelles. Reactive pial cells could be distinguished from macrophages of presumed hematogenous origin on the basis of their surface morphology. These findings suggested that pial cells had the ability to alter their normal structural and behavioral characteristics and to become macrophage‐like under these conditions of secondary challenge by BCG.
Fine structure of the liver in the larval lamprey, Petromyzon marinus L.; Hepatocytes and sinusoids
Authors: Peek W. D. , Sidon E. W. , Youson J. H. , Fisher M. M.
Published: February 2005

The ultrastructure of hepatocytes, bile canaliculi, and hepatic sinusoids of the larval lamprey, Petromyzon marinus, was examined using thinsectioned and freeze‐fractured tissues. The liver is a “tubular gland” with hepatocytes arranged in a tubular fashion around large bile canaliculi. Hepatocytes are roughly conical in shape, with their tapered apices facing a bile canalicular lumen. They possess extensive rough and smooth endoplasmic reticulum, a well‐developed Golgi complex, abundant mitochondria, and varying numbers of large secondary lysosomes. Both secondary lysosomes and the Golgi complex are concentrated in the apical or peribiliary cytoplasm, indicating a possible role in bile secretion. The apical surfaces of the hepatocytes bear numerous elongate microvilli and occasional cilia, which project into the bile canaliculi. The hepatocytes are joined, apically, by junctional complexes composed of zonulae occludentes and adhaerentes. In freeze‐fracture, the zonulae occludentes are of variable apicobasal depth and consist of honeycomb‐like meshworks of fibrils. Spaces of variable width frequently appear in the P‐face grooves, indicating that the zonulae occludentes are “leaky.” Numerous communicating (gap) junctions join the hepatocytes laterally. Varying numbers of lateral microvilli project into the intercellular spaces and, basally, the plasma membrane is deeply infolded, resulting in the formation of apparently interdigitating basal processes resting upon a thin basal lamina. Sinusoids are composed of both a heavily‐fenestrated, continuous endothelium, and phagocytic reticulo‐endothelial (Kupffer) cells. Despite the difference in arrangement of their hepatocytes, the mammalian and lamprey livers show similar ultrastructural features.
Aglomerular pathways in intrarenal microvasculature of aged rats
Authors: Casellas Daniel , Mimran Albert
Published: February 2005

By means of silicone rubber injections, we confirmed the existence of several types of aglomerular arterial pathways within kidneys of aged rats. In superficial cortex some interlobular arteries divide to form aglomerular branches (Ludwig's arterioles) towards cortex corticis. In juxtamedullary cortex these pathways are relatively more numerous, they comprise: (a) Vasa Recta Vera, (b) glomeruli in which afferent and efferent arterioles form a continuous vessel and (c) glomeruli with two efferent vessels, one by‐passing glomerular tuft. In addition, results obtained in the rat by the microsphere technique are in agreement with our morphological observations.
Morphology of the epithelium of the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the adult male rabbit
Authors: Jones R. , Hamilton D. W. , Fawcett D. W.
Published: February 2005

The fine structure of the epithelium lining the extratesticular rete testis, ductuli efferentes and ductus epididymidis of the rabbit has been investigated. In the ductuli efferentes the epithelium is composed of two cell types, principal cells and ciliated cells. The latter cell type is distinguished from principal cells by the presence of cilia projecting into the lumen and the position of the nucleus in the apical half of the cell. Principal cells in this segment are characterized by micropinocytotic vesicles on the surface plasma membrane and a variety of small dense bodies scattered throughout the cytoplasm. In the ductus epididymidis basal cells replace ciliated cells as the second cell type, but differences between various segments of the epididymis are related to the fine structure of the principal cells. In the proximal caput epididymidis (Nicander's region 1) the principal cells are tall with long microvilli. They typically contain a small Golgi apparatus and a cluster of dense bodies adjacent to the nucleus. In the distal caput epididymidis (Nicander's regions 2–5) the apical cytoplasm of principal cells is filled with numerous micropinocytotic vesicles and large multivesicular bodies; these features are interpreted as signs of absorptive activity. The multivesicular bodies are absent from the cytoplasm of principal cells in the corpus epididymidis (Nicander's region 6) and, instead, numerous elements of smooth endoplasmic reticulum, a large Golgi apparatus, lipid droplets and dense bodies characterize principal cells in this segment. Towards the proximal cauda epididymidis (Nicander's region 7), the number of dense bodies (lysosomes) in the cytoplasm increases considerably. In the globose cauda (Nicander's region 8), the principal cells are reduced in height, and in addition to the features described in region 7, are characterized by a concentric array of rough endoplasmic reticulum in the basal cytoplasm. These observations are discussed in relation to the role of the epididymis in promoting the maturation and survival of spermatozoa.
Migration and turnover of entero‐endocrine and caveolated cells in the epithelium of the descending colon, as shown by radioautography after continuous infusion of 3H‐thymidine into mice
Authors: Tsubouchi S. , Leblond C. P.
Published: February 2005

Adult male mice were given a continuous infusion of about 0.5 μCi of 3H‐thymidine per gram body weight per day for periods varying from 1 to 60 days. Semithin sections of descending colon were cut from plastic‐embedded blocks and stained by a method combining silver impregnation and iron hematoxylin, by which argentaffin entero‐endocrine cells and caveolated cells could be identified. From radioautographs, the labeling index of these cells was determined.

One to three days after the beginning of 3H‐thymidine infusion, label is observed in some of the stained entero‐endocrine cells in the bottom of the crypts; the apices of these cells reach the crypt lumen and are joined to neighboring cells by terminal bars (junctional complexes). After five to seven days, labeled entero‐endocrine cells are seen on the sides of the crypts, where their base stretches along the basement membrane and their apex has lost its terminal bar connections to neighboring cells. Finally, by 13 and 24 days, labeled cells are observed within the epithelium at the mucosal surface. The turnover time, which is taken to be equal to the mean time required for migration from site of origin to site of loss on the mucosal surface, has been estimated at 23.3 days. This is much longer than the 4.6 days required by the two main cell types of the epithelium — vacuolated‐columnar and mucous cells — to travel the same route. It is likely that, after entero‐endocrine cells lose their terminal bar attachment to other epithelial cells, they migrate independently and very slowly.

Labeled caveolated cells are first seen in the crypt bottom one day after the beginning of 3H‐thymidine infusion. By three to five days, they are on the sides of the crypts; their base is stretched along the basement membrane, but their apex retains its attachment to neighboring cells by terminal bars. By seven days, labeled caveolated cells are on the mucosal surface. Their turnover time has been assessed at 8.2 days. This is, again, longer than for the two main types to which they are bound by terminal bars throughout migration. The discrepancy is explained by the caveolated cells arising deeper in the crypts than most vacuolated‐columnar and mucous cells.
Differences in regional capillary distribution and myocyte sizes in normal and hypertrophic rat hearts
Authors: Gerdes A. Martin , Callas Gerald , Kasten Frederick H.
Published: February 2005

Data are reported which show significant regional capillary differences in left ventricular endocardium and epicardium of normal rats and of rats with hyperthyroid‐induced cardiac hypertrophy. The epicardial region of control rats has 38% more capillaries than the endocardial region. Control endocardial myocytes are 62% larger in cross‐sectional area than epicardial myocytes. Hypertrophic hearts exhibit regional differences in capillary density similar to those in the normal hearts, but there is an overall reduction of 12 and 17.5% in capillary density in both regions. The average cross‐sectional area of myocytes increases 34.5% in the epicardium and 22.5% in the endocardium.
Developmental changes in the fine structure of rhesus monkey amnion
Authors: King Barry F.
Published: February 2005

The purpose of this study was to examine developmental changes in the amnion with regard to: (1) the fine structure of the epithelial cells, (2) the nature and permeability of the intercellular junctions, and (3) the structure of extracellular matrix components in the subepithelial compartment. Comparisons were made between amnion from 26‐72 and 146‐170 days of gestation. Early in gestation, epithelial cells were squamous and had few apical microvilli; late in gestation, cells were cuboidal with numerous microvilli and a well‐developed glycocalyx. Epithelial cells from early gestation had large glycogen stores, well‐developed Golgi apparatus, granular ER, and relatively few 10 nm cytoplasmic filaments. Later, cells were similar except for less glycogen, somewhat more lipid droplets, and numerous 10 nm cytoplasmic filaments. Lateral cell borders were complexly interdigitated at both ages and desmosomes were the predominant type of cell junction. Occasional tight junctions were observed early in gestation; no tight junctions were observed near term. After exposure to peroxidase in vitro, reaction product was present in the intercellular spaces, and the epithelial cells demonstrated very limited pinocytosis. Early in gestation, the basal cell surface was smooth, had no specialized junctions, and was underlain by a complete basal lamina (BL). Late in gestation, the basal surface was thrown into numerous folds, had hemidesmosome‐like junctions, and an incomplete BL. Early in gestation, the BL contained ruthenium red‐positive particles; later, these particles were absent. Early in gestation, the BL had a layer of interstitial collagen fibrils beneath it; late in gestation, a thick layer of 12 nm microfibrils was interposed between the BL and the interstitial collagen. The microfibrillar layer appeared at about 72 days of gestation, when it was apparently formed between the basal cell surface and the partially detached basal lamina.

The results support the view that amniotic epithelial cells remain metabolically active throughout gestation and that the intercellular pathway is important in the movement of certain large molecules across the epithelium. The microfibrillar layer may provide structural strength for the amnion late in gestation.
Utilization of the chick chorioallantoic membrane for in vitro growth of the embryonic murine kidney
Authors: Preminger Glenn M. , Koch William E. , Fried Floyd A. , Mandell James
Published: February 2005

Previous experimental investigations of embryonic kidney development with in vitro organ‐culture techniques have been limited by the short duration of graft viability and lack of detailed anatomic development. In a modified application of the chick chorioallantoic‐membrane (CAM) grafting technique, we have transplanted 11‐day‐old undifferentiated embryonic murine kidney rudiments and studied their differentiation and early morphogenesis.

Surviving grafts, maintained for 5–10 days on the CAM, demonstrated well‐developed convoluted secretory tubules and highly branched collecting ducts. Definitive glomeruli were also identified in these grafts by the presence of efferent tubules, visceral and parietal epithelium, capillary tuft, and Bowman's space. In vitro branching of the ureteric bud preceded formation of definitive tubules. Sections of the CAM grafts appeared histologically comparable to the 14–15‐day in vivo embryonic metanephros. Grafts of 10‐day‐old rudiments showed minimal kidney development; fewer grafts survived, fewer tubules were formed, and fewer glomeruli developed. Our results indicate that the CAM is an efficient site for in vitro murine kidney development with both vascularization of the explant and extensive maturation, including the appearance of primitive nephron units.
Trophoblastic and uterine luminal epithelial surfaces at the time of blastocyst adhesion in the rat
Authors: Enders Allen C. , Schlafke Sandra , Welsh Alerick O.
Published: February 2005

Fixed uteri from rats on the afternoon of day 6 of pregnancy were split to expose the implantation chambers, their enclosed blastocysts, and the imprints of the blastocysts on the adjacent epithelium of the chamber. Some ofthe implantation chambers were prepared for scanning electron microscopy; other chambers were treated with colloidal iron hydroxide, with cationized ferritin, or with the tannic acid method, and subsequently were prepared for transmission electron microscopy. In this manner, the disposition of the surfacecoat markers on the surface of the blastocyst, surface of the uterus within the chamber, and the surface of the uterus that had been apposed to a blastocyst were compared. Despite the pronounced morphological differences between the microvilli of the uterine luminal epithelium in the imprint and those in the rest of the chamber, the binding of the markers was remarkably similar. No evidence of removal of surface coat could be found in that area of the uterus in contact with the blastocyst. In addition, in two instances in the cationized ferritintreated material, and in another instance in tannic acid‐stained material, regions of the apparently adhering trophoblastic cell membranes and uterine cell membranes had abundant coat materials and, possibly, even secretory materials interposed. When blastocyst‐sized glass beads were introduced into uteri from animals made pseudopregnant or unilaterally pregnant, the beads failed to elicit a decidual response and made an imprint that did not resemble the imprint of a blastocyst in an implantation chamber. It was concluded that, at least in the initial stages of adhesion, the blastocyst does not bring about a physical removal of the demonstrable aspects of the surface coat of the uterus. It was concluded further, that glass beads are not a suitable object for mimicking a blastocyst in the rat uterus.
Stereological analysis of the guinea pig adrenal: Effects of dexamethasone and ACTH treatment with emphasis on the inner cortex
Authors: Black Virginia H. , Russo James J.
Published: February 2005

This paper describes the morphological responses of adult male guinea pig adrenals to dexamethasone (DEX) and adrenocorticotrophic hormone (ACTH), in both qualitative and quantitative terms. Most organelles and inclusions are affected, but their responses often vary in the different cell types examined: zona fasciculata externa and interna, and zona reticularis.

Following DEX the volume of lipid droplets increases in cells of zona fasciculata externa but decreases in zona reticularis; smooth endoplasmic reticulum decreases in fasciculata externa but increases in reticularis. Following ACTH, exactly the opposite occurs. This strongly suggests differing functions for these subcellular entities in each cell type, particularly for the smooth reticulum, as well as for the cells themselves.

The volume of the Golgi complex markedly decreases following DEX in all cells but increases only in zona fasciculata interna and zona reticularis following ACTH. These deeper cortical cells are known to secrete at least one sulfated steroid, dehydroepiandrosterone sulfate, and these changes in the Golgi complex strengthen the suggestion that the Golgi plays a role in sulfation of steroids.

Mitochondrial volume and number decrease in all cells following DEX, supporting their role in steroidogenesis. Further decreases in their volume, accompanied by increases in their number following ACTH, may be related to a proliferation of mitochondria in response to ACTH.

Changes in peroxisome volume and number, following DEX and ACTH, suggest a possible role for these organelles in steroid cell metabolism.

Lysosomes decrease in volume in all cells following ACTH. This does not support the recently suggested concept that they play a role in steroid secretion.
Motor‐end‐plate and nerve distribution in a histochemically compartmentalized pennate muscle in the cat
Authors: Galvas Patrick E. , Gonyea William J.
Published: February 2005

Previous investigations in this laboratory have shown the flexor carpi radialis muscle (FCR) of the cat to be compartmentalized with regard to the distribution of muscle fiber types. This study was undertaken to determine whether each compartment of the FCR had a distinct motor innervation band, or whether there was only one innervation band, as has been reported previously for other muscles. In order to assess variation in motor innervation banding patterns, the innervation bands were correlated with the muscle‐tendon architecture. Each compartment of the FCR possessed a distinct innervation band. In addition, it was observed that the nerve to the FCR divided into a number of separate intramuscular branches which were distributed to the different histochemical compartments. It is possible that muscle fibers innervated by a single intramuscular nerve branch, and possessing a discrete innervation band, are locally organized within subdivisions of the FCR. It is hypothesized that the compartmental organization of the FCR would allow discrete regions of the muscle to function independently when performing different motor tasks.
“M” cell distribution in follicle‐associated epithelium of mouse peyer's patch
Authors: Smith M. W. , Peacock M. A.
Published: February 2005

The distribution of “M” cells within the follicle‐associated epithelium (FAE) of mouse Peyer's patches has been estimated from a series of SEM micrographs. “M” cells are found generally to be distributed evenly throughout the higher regions of the FAE. The frequency with which “M” cells occur decreases in the lower regions of the FAE. No “M” cells are found in the follicle‐associated crypts. “M” cell microvilli are longer than those of enterocytes found at the base of the follicle‐associated crypts and shorter than those found on enterocytes in other parts of the FAE.

No lymphoid cells occur within the epithelium of the follicle‐associated crypt. Lymphoid cells in the higher regions of the FAE are associated closely with “M” cells. There is, in the lower regions of the FAE, a transitional zone where lymphoid cells occur both free within the epithelium and closely associated with “M” cells. It is suggested that an initial close association of lymphoid cells with young, fully differentiated enterocytes is responsible for the latter's subsequent transformation to “M” cells.
Comparative histochemical study of prosimian primate hindlimb muscles. II. Populations of fiber types
Authors: Sickles Dale W. , Pinkstaff Carlin A.
Published: February 2005

The populations of fiber types in hindlimb muscles of the tree shrew (Tupaia glis), lesser bushbaby (Galago senegalensis), and the slow loris (Nycticebus coucang) were described and an attempt was made to correlate populations of fiber types and locomotor patterns. Muscle fibers were assigned to one of the following groups: fast‐twitch glycolytic (FG), fast‐twitch oxidative‐glycolytic (FOG), and slow‐twitch oxidative (SO). Histochemical techniques for the demonstration of alkaline‐ and acid‐stable ATPases, succinic dehydrogenase, and mitochondrial á‐glycerophosphate dehydrogenase were used in the classification of muscle fibers. Results indicated that the FG fiber type is the predominant fiber type in muscles used for jumping, the FOG fiber type is predominant in muscles used for running, and the SO fiber type occurs in high percentages in postural muscles. The SO fiber was also the most common fiber in muscles of the slow loris‐‐a species that exhibits a slow, deliberate, sustained locomotor pattern. Intramuscular regional variations in populations were seen in some larger muscles of the tree shrew, but not in the lesser bushbaby and slow loris. Our results did not support the contentions of others that analogous muscles in different species have similar populations of fiber types.
An ultrastructural investigation of developing vasomotor innervation in rat peripheral vessels
Authors: Todd Mary E. , Tokito Mariko K.
Published: February 2005

The developing innervation was investigated in three muscular peripheral arteries from male Wistar rats. These were the superficial epigastric and saphenous arteries, branching from the femoral artery in the thigh, and the tail artery. At maturity the tail and saphenous are similar in size and the superficial epigastric is about half the size of the other two. They are approximately the same size at birth and were chosen because of the resemblance of the tunica media among them. The general pattern of the developing innervation was similar in all three, starting with nerve processes containing mainly empty vesicles. As development proceeded, the processes usually were enclosed within Schwann cells, and both the number of clear vesicles and the number of vesicles with dense cores increased. Tubular membranes probably budded off vesicles. The development of the innervation was mainly postnatal, although some processes seen in the fetus may have been growth cones. The tail artery was the latest to develop recognizable nerves, although the number increased dramatically and had surpassed those in the other two vessels by 12 days of age. It had the densest nerve plexus at maturity. Only adrenergic vasomotor innervation was present in these vessels. The nerves retained a precise relationship, adjacent to the outermost layer of smooth muscle cells and external elastic lamina, throughout development. The Schwann cell population increased very slowly and was similar in each vessel at each age. This meant that the tail artery had many more nerve processes per Schwann cell than the other two vessels. These three muscular arteries, then, varied in the rate of development of their adrenergic innervation and in the final density.
Some observations on sperm transport through the uterotubal junction of the rat
Authors: Gaddum‐Rosse Penelope
Published: February 2005

Entry of spermatozoa into the oviducts of mammals is restricted by the uterotubal junctions. The extent to which these junctions act as selective valves, or filters, for sperm transport has not been determined. A new technique has been developed that permits the direct visualization of sperm transport through the uterotubal junction of the rat in vitro. After mating or artificial insemination, the female tract is removed to a special “observation dish” containing oxygenated Earle's solution maintained at 37°C. The oviducts are severed 1.0–1.5 mm above the uterotubal junctions. Under appropriate magnification and with oblique transillumination, spermatozoa may be observed emerging from the cut ends. It was noted that only motile spermatozoa emerged and that they usually appeared individually, with an interval of several minutes between each. Their egress was not directly related to contractions of the uterine cornu. Neither immotile spermatozoa nor a dye solution were observed to pass through the uterotubal junction. It is concluded that sperm motility is important, and probably essential, for sperm entry into the oviducts in the rat. Scanning electron microscopy revealed that the rat uterotubal junction forms a small mound or papilla projecting into the uterine cavity. No ciliated cells were observd in this region.
Effects of glucagon on hepatic glycogen and smooth endoplasmic reticulum
Authors: Striffler John S. , Cardell Emma Lou , Cardell Robert R.
Published: February 2005

The action of glucagon on hepatic glycogen and smooth endoplasmic reticulum (SER) was studied in samples of liver taken sequentially from anesthetized rats. The physiological state of each animal was assessed by continuously monitoring aortic blood pressure and blood lactate/pyruvate ratios. High hepatic glycogen levels were established by using 10–12 hr fasted control‐fed rats infused continuously with glucose. In rats receiving glucose only, hepatic glycogen levels remained above 5.0% during the 4‐hr period of glucose administration. Centrilobular hepatocytes displayed an abundance of glycogen which often appeared dispersed with elements of SER between the glycogen particles. Periportal cells had dense clumps of glycogen with few vesicles of SER restricted to the periphery of the glycogen masses. The addition of glucagon to the glucose infusate caused a marked stimulation of glycogenolysis. In these rats, the hepatic glycogen level (x̄±SE) was 6.71±.15% 1 hr after glucose and declined after initiation of glucagon infusion as follows: 5.86±.29% (15 min), 4.89±.26% (1 hr), 2.16±.40% (2 hr), and 1.66±.29% (3 hr). The fine structure of hepatocytes showed a dramatic response to the administration of glucagon. The glycogen regions of the cells were noticeably decreased in size and number of glycogen granules 3 hr after initiation of glucagon infusion, and SER was abundant in both periportal and centrilobular hepatocytes. The interpretation offered is that glucagon induces the formation of new SER membranes which participate in glycogen breakdown and/or glucose release from hepatocytes.
The epithelium of the excretory duct of the human submandibular gland: A transmission and scanning electron microscopic study
Authors: Testa‐Riva Francesca , Puxeddu Paolo , Riva Alessandro , Diaz Giacomo
Published: February 2005

The duct of the human submandibular gland (Wharton) is lined by a pseudostratified epithelium consisting of principal and basal cells. Scattered among them are a few goblet and ciliated cells.

The principal cells are columnar in shape with many mitochondria, numerous dense bodies and a central nucleus with some indentations. Their apical cytoplasm shows a number of clear vesicles, some of which are reactive to silver and are extruded by exocytosis into the lumen. Other vesicles, which are unreactive, may represent the products of the absorption process. A mechanism of apocrine secretion is also observed in the principal cells.

Thus, with regard to its functions, the duct of the human submandibular gland modifies the composition of saliva by adding a secretory component to it. This latter material is derived from the goblet cells but chiefly from merocrine (exocytosis) and apocrine secretion of principal cells.
Rapid alterations induced by insulin in hepatocyte ultrastructure and glycogen levels
Authors: Thompson Ed W. , Parks William C. , Drake Richard L.
Published: February 2005

The speed with which insulin alters hepatocyte ultrastructure and glycogen levels in insulin‐deficient rats has been studied. Insulin deficiency was induced with alloxan, followed by insulin treatment with regular and NPH insulin. Rats were killed at various times after the insulin injection, blood samples were obtained, plasma glucose levels were determined, and liver samples were prepared for electron microscopy and glycogen determinations. Plasma glucose levels in insulin‐deficient rats declined to normal values by 4 hours post insulin, returning to insulin‐deficient levels by 8 hours post insulin. Hepatic glycogen was considerably reduced in the insulin‐deficient rats. By 1 hour post insulin hepatic glycogen increased, reached maximal levels by 8 hours, then declined to insulin‐deficient levels by 36 hours. The ultrastructural appearance of both centrilobular and periportal hepatocytes from insulin‐deficient rats showed abundant vesicular smooth endoplasmic reticulum (SER), decreased rough endoplasmic reticulum (RER), and enlarged RER intracisternal spaces. One‐half hour post insulin, centrilobular hepatocytes were unchanged. In periportal hepatocytes, however, vesicular SER was no longer visible, the RER intracisternal spaces appeared normal, and the amount of RER had increased. By 1 hour post insulin the centrilobular hepatocytes showed similar ultrastructural changes. These changes became more pronounced in the next few hours and remained through 24 hours. By 36 hours both centrilobular and periportal hepatocytes appeared similar to those in the insulin‐deficient rat. These results demonstrate the rapid and lobular‐specific effects insulin has on the hepatocyte.
The surface topography of the colonic crypt in rabbit and monkey
Authors: Specian Robert D. , Neutra Marian R.
Published: February 2005

Scanning electron microscopy (SEM) was used to investigate the epithelial topography of the surface and crypt in rabbit and monkey colon. Crypt openings in monkey colon are arranged in a hexagonal pattern, in sharp contrast to rabbit colon where they are randomly arrayed and frequently hidden by epithelial folds. Crypt lumens were exposed by freezing ethanol‐dehydrated tissue in liquid nitrogen and fracturing the tissue with a razor blade. The resulting overview of crypt‐cell luminal surfaces showed that as columnar cells mature and migrate up the crypt and onto the colonic surface, their microvilli become progressively more abundant. Goblet cells were readily identified in the cross‐fractured crypt epithelium; their luminal surfaces are characterized by short, sparse microvilli. The changing appearance of the luminal surface of goblet cells was visualized by SEM during the exocytosis of single mucous granules from unstimulated crypt goblet cells, and during the compound exocytosis of multiple granules in response to acetylcholine.
Bone marrow cells associated with heightened eosinophilopoiesis: An electron microscope study of murine bone marrow stimulated by Ascaris suum
Authors: Sakai Nobuhiko , Johnstone Colin , Weiss Leon
Published: February 2005

An acute eosinophilopoiesis occurs in mice secondarily exposed to Ascaris suum, the marrow eosinophils increasing from approximately 5% to 45%, and blood levels from 50/ml3 to more than 1000/ml3, within 14 days. Eosinophilopoiesis occurs in hematopoietic compartments of the bone marrow and is associated with four other cell types: branched stromal cells, macrophages, lymphocytes, and reticular cells adventitial to venous sinuses. Branched stromal cells, a newly recognized cell type, are presented in intensified hematopoiesis of at least several blood‐cell types. They are characterized by extensive branches surrounding contiguous hematopoietic cells, dense cytoplasm, and multiple communications between nuclear cisternae and an extensive, dilated endoplasmic reticulum. These cells, moreover, have a capacity to coalesce to form an extensive, branching, multinucleate giant‐cell system. They are neither phagocytic nor fibroblastic, and attend every phase of eosinophilic hematopoiesis. Macrophages lie among eosinophils, and they possess many processes which extend among eosinophils. The may constitute, with the eosinophils, islets similar to erythroblastic islets; or they may lie among eosinophils in sheets. Macrophages also lie against the outside surfaces of vascular sinuses and extend transmural processes into the lumina. Lymphocytes of a type not yet known are regularly present among developing eosinophils. Adventitial cells of vascular sinuses, fibroblastic cells, extend processes deep into perivascular hematopoietic spaces, and thereby envelop eosinophils and other maturing blood cells. While adventitial cells can be dense, they were typically quite lucent and had microfilaments clustered beneath their plasmalemmae. With the large‐scale blood‐cell delivery characteristic of this model, marked changes occurred in the walls of the vascular sinuses. Adventitial cells moved away from the vascular wall, permitting blood cells direct access to the basal surface and reducing their cover from more than 65% to less than 20%. Both adventitial and endothelial cells may be compact and dark, or expanded and quite lucent. Heterolysomes occur in moderate‐to‐large numbers in both adventitial and endothelial cells, and large gaps filled with blood cells in transit occur in endothelium. The hematopoietic‐associated cells and the vasculature described here would appear to provide the cellular microenvironment which regulates hematopoiesis.
The ultrastructure of the thin limbs of henle in kidneys of the desert heteromyid (Perognathus penicillatus)
Authors: Nagle Ray B. , Altschuler E. M. , Dobyan Dennis C. , Dong S. , Bulger Ruth Ellen
Published: February 2005

The thin limbs of both long‐ and short‐looped nephrons in Perognathus kidneys were studied with transmission and scanning electron microscopy. The superficial nephrons have a short thin limb located in the vascular bundles of the outer medulla and are characterized by a simple, low‐lying epithelium (0.4 ± 0.1 μ thickness). In contrast, the first descending part of the thin limb of the majority of midcortical and juxtamedullary nephrons has a relatively thick epithelium (1.7 ± 0.6 μ in thickness) with marked lateral and basal interdigitation and a dense surface covering of microvilli. The remaining part of the long descending thin limb is relatively simple with a low‐lying epithelium (0.6 ± 0.1 μ in thickness), decorated on its surface by sparse microplicae. The bend of the loop and the ascending limb are covered by a very simple low‐lying epithelium (0.6 ± 0.2 μ in thickness) with relatively little surface modification. The extreme urine‐concentrating ability of Perognathus does not appear to be due to the development of a unique thin loop epithelium but rather to the extensive length of the inner and outer medulla.
Localization of tritiated vitamin A in lymph nodes of the mouse: An autoradiographic study of vitamin A‐storing cells
Authors: Hirosawa Kazushige , Yamada Eichi
Published: February 2005

Localization of tritiated vitamin A in lymph nodes of the mouse was investigated by the use of light‐ and electron‐microscopic autoradiography. Young male mice were fed a diet containing 3H‐vitamin A acetate for a week. Lymph nodes were removed and prepared for autoradiography. Lipid droplets in fibroblast‐like cells showed high concentrations of radioactivity. These cells were distributed around lymphatic sinuses and blood vessels. The cells can, therefore, be classified as “vitamin A‐storing cells” according to criteria proposed earlier by Yamada and Hirosawa (1976). Control animals from the same litter were maintained on ordinary laboratory food for the same period and examined by electron microscopy. Lipid‐droplet‐containing cells were found in the same areas as in the experimental animals but in fewer numbers. This suggests that the increased number of vitamin A‐containing lipid droplets is due to hypervitaminosis A in the experimental animals. The presence of some cells containing these droplets in the control animals would imply that even under normal feeding conditions the animals ingested excess amounts of vitamin A, which was retained in lipid droplets. The stored vitamin A probably participates in metabolic processes such as the formation of glycoproteins in ground substance.
The ultrastructure of the atrioventricular junctional tissues in the newborn ferret heart
Authors: Marino Thomas A. , Biberstein Denise , Severdia Joseph B.
Published: February 2005

In this study the structure of the atrioventricular (AV) node and bundle in the newborn ferret heart was examined by light and electron microscopy. At the light microscopic level the AV node could be subdivided into deep and superficial portions. Electron microscopy revealed that both superficial and deep AV nodal cells were characterized by a paucity of myofibrils, desmosomes, fasciae adherentes and gap junctions. Deep AV nodal cells, however, had more surface specializations than did superficial AV nodal cells. In both subdivisions the constituent cells were ellipsoid with tapering end‐processes. In contrast to the nodal cells, the newborn AV bundle cells were round to ovoid. The AV bundle cells were organized into large fascicles, and there was a high frequency of anastomosing intercommunication between fascicles. These bundle cells had few myofibrils and a high incidence of apposed plasma membrane. The present morphological findings support the concept that there are significant postnatal morphological changes that occur in the region of the AV junction. These results are also consistent with findings in other species that AV nodal conduction time is similar in newborns and adults, while conduction through the AV bundle increases with age.