bluuebunny/crossref_metadata_2025 huggingface dataset:
Endocytic activity in embryonic cardiac cushion mesenchyme in vivo and in collagen gel lattices
Authors: Hay Don A. , Markwald Roger R. , Sage Alexis P.
Published: February 2005

Mesenchymal cells, termed cushion tissue (CT) cells, are the principal cellular elements in atrioventricular (AV) endocardial cushions, the latter constituting AV septal and valvular primordia in the embryonic heart. Atrioventricular canals of 2½ day chick embryo hearts were explanted onto collagen gel lattices, wherein cushion endothelial cells acquired the characteristics of CT cells and invaded the gel. The endocytic activity of in situ CT cells was compared to that of gel‐cultured CT cells by exposing appropriate preparations to horseradish peroxidase (HRP), cationized ferritin (CF) or to lysozyme. Stimulation by these exogenous proteins resulted in phagocytosis. In addition, all three markers were associated with coated pits, smooth surfaced vesicles (45–60 nm), C‐ or cup‐shaped structures and other lysosomal elements, but were excluded from Golgi cisternae and their entire vesicle population. In CT cells, HRP does not act solely as a “content” marker that reflects fluid‐phase uptake. Instead it appears to follow adsorptive endocytic pathways. The endccytic behavior of in vivo and in vitro cushion tissue cells appears to be the same. Endogenous endocytic activity may reflect in part membrane retieval, which counterbalances the extensive exocytosis observed in these cells.
Organization and structure of branches in the rat pulmonary arterial bed
Authors: Lane Bernard P. , Zeidler Marie , Weinhold Chantal , Drummond Edward
Published: February 2005

Pulmonary arteries were fixed by perfusion under constant pressure and filled with rubber. The hardened rubber cast delineated the arterial bed, permitting dissection of axial vessels and all branches. Each segment was prepared for scanning electron microscopy and transmission electron microscopy. Branches arising at acute angles from the axial artery and the first two generations of its branches, regardless of diameter, had the same concentric muscle layer structure as parent vessels. Endothelial cells of the parent vessel were oriented into the ostia of these branches. Branches that came off the axial vessel or its branches at right angles had spiral muscle bundles and led to nonmuscular precapillary vessels. Right angle branches also had similar wall structure regardless of diameter. Near the ostia of right angle branches, endothelial cells of the parent vessels did not show orientation of their long axis into the branch lumens. It was concluded that branch arteries arising at acute angles are conduits which carry blood to distant parts of the lung while right angle branches are a histologically different group which distribute the blood to local capillary beds.
Dynamics of lysosomal elements in pulmonary alveolar macrophages: I. The postactivation lysosomal cycle
Authors: Sorokin Sergei P.
Published: February 2005

Lavaged alveolar macrophages of mice were examined by light and electron microscopy primarily using cytochemical reactions for lysosomal enzymes. Among several methods tried, the Reed and Bennett procedure for N‐acetyl‐β‐glucosaminidase (J. Histochem. Cytochem., 23:752–757 (1975)) was preferred for use in smears and the Gomori acid phosphatase method for ultrastructural study. Prior to examination, some mice were exposed to an aerosol of finely divided iron oxide for 1–3 hours at particle concentrations of 80–290 mg/m3, others breathing clean air provided macrophages for comparison. Both exposed and unexposed macrophage populations were composed of a similar range of subtypes differing in cytological appearance and enzymic activity. The exposed populations tended to contain a higher proportion of strongly reactive cells, notably of a kind possessing many elongate lysosomes; consequently, it appeared that many cells in these populations were substantially engaged in synthesizing lysosomes. Based on this material, the cycle of production was reconstructed. This is divisible into five natural stages, defined primarily by the intracellular distribution of lysosomal enzyme activity and to a lesser extent by other cytological criteria. Commencing in immature cells, where the predominant localization of acid phosphatase activity in the Golgi apparatus and a few rounded lysosomes (Stage 1), the cycle continues through a period dominated by extensive growth of the granular endoplasmic reticulum (Stage 2). With the appearance of a crop of elongate or lumbricoid lysosomes, the predominate locus of acid phosphatase activity shifts from the Golgi apparatus to these bodies (Stage 3). Thereafter, they often are seen together with an increased number of large rounded lysosomes (Stage 4), but in other cells only the latter are to be found (Stage 5). This lysosomal cycle operates in cells showing other signs of an aroused metabolism, and it appears not to be closely tied to the mitotic cycle. The nascent lumbricoid lysosomes seem to be formed at some distance from the Golgi apparatus, wheras the lysosomes produced by more quiescent cells often lie in close relationship to that organelle.
A computer graphic study of cardiac truncal septation
Authors: Thompson Robert P. , Wong Yu‐Man Matthew , Fitzharris Timothy P.
Published: February 2005

Septation of the cardiac truncus arteriosus in the normal rat embryo was described and illustrated by three‐dimensional reconstruction from serial sections through the developing outflow tract. Tracings of selected structures were digitized on an Apple II‐plus microcomputer, relayed through a central computer facility, and displayed on a Hewlett‐Packard 9845C graphics computer. Rotation and dissection of the color images allowed a kinetic description of the principal features of truncal septation and comparison with analogous events in the chick.

A complex of tissue structures appeared in the downstream, distal truncus at 13 days of gestation and moved toward the ventricle(s) through the following day. As in the chick, the forming semilunar valves remained within 200 μm of the cephalic margin of the myocardial sleeve as they rotated and descended toward their definitive position against the heart. Mesenchymal condensations formed within the intervening aorticopulmonary (AP) septum and remained in close association with the principal bifurcation of the spiralling blood lumens, passing between the valves and descending along the conus septum. As the conus septum fused at 15 days of gestation, three outlets for cardiac outflow were seen: the major left and right streams to the aortic and pulmonary valves, respectively, and an apparently dwindling stream which crossed from the right ventricle behind the conus septum to exit through the aorta. In the chick, but not in the rat, nerve bundles invaded the distal truncus during septation to form the cardiac plexus.
A novel sectioning technique for use in descriptive embryology: Bridging the gap between paraffin and plastic serial sections
Authors: Schoenwolf Gary C. , Chandler Nancy B.
Published: February 2005

A novel sectioning technique for making serial sections for use in descriptive embryology is presented. This technique allows one to obtain good‐quality sections (5‐ to 10‐μm thick) of embryos embedded in plastic, several times faster than with conventional plastic sectioning techniques. Furthermore, this technique can be used to serially section embryos until desired levels are reached. One‐micrometer or thin (50–100 nm) sections can then be cut for study, respectively, by light and transmission electron microscopy. The resolution of cellular morphology in 5‐ to 10‐μm sections is intermediate to that of paraffin and 1‐μm plastic sections, and gross tissue distortions typically present in paraffin sections are absent in plastic sections. Thus, in terms of convenience and section quality, this technique bridges the gap between those routine techniques used for preparation of conventional paraffin and plastic serial sections.
Secretory process in Brunner's glands during recovery from stimulation with a single dose of pilocarpine
Authors: Scott Carol A. , Flickinger Charles J.
Published: February 2005

The secretory pathway and kinetics of the secretory process were studied in Brunner's glands of mice after stimulation of secretion with a parasympatho‐mimetic drug. Adult male mice were injected with pilocarpine, while unstimulated controls received saline. The animals were subsequently administered an intravenous injection of 3H‐threonine, and tissue was prepared for electron microscope autoradiography at intervals ranging from 5 minutes to 2 hours after injection of the radioactive precursor. Stimulation with pilocarpine resulted in discharge of secretory granules, which was reflected in a significantly lower percentage of the cell volume occupied by granules. In both control and stimulated mice, at 5 minutes after injection of 3H‐threonine, the highest percentage of silver grains over the rough endoplasmic reticulum declined at later intervals, and a peak of labeling was observed over the Golgi apparatus at 1 hour. Labeling of the secretory granules increased in the 1‐ and 2‐hour samples from both control and stimulated mice, although the relative concentration of radioactivity in both Golgi‐associated and apical secretory granules was greater in stimulated than control glands at 1 hour. The results suggest that the secretory protein produced by Brunner's glands was synthesized by the rough endoplasmic reticulum and transported to the Golgi apparatus where secretory granules were formed in both stimulated and control glands. Depletion of secretory granules by prior stimulation resulted in no change in the kinetics of arrival of radioactivity in the cell organelles involved in the secretory process. However, the drainage of the radioactive label from the rough endoplasmic reticulum was significantly slower in the stimulated glands than in the controls. The existence of two subcompartments within the rough endoplasmic reticulum is among the possible explanations for the latter observation.
Problems associated with the morphometric measurement of transverse skeletal muscle fibers: I. Analysis of frozen sections
Authors: Shorey C. D. , Cleland K. W.
Published: February 2005

The aim of this study was to evaluate the effects of a number of reported procedures which precede freezing on the cross sectional area of skeletal muscle fibers. Probable sources of variation were recognised as:

Within blocks, same animal, same procedure. Variability in the size of muscle fibers from area‐based measurements was determined for the anterior head of the biceps femoris muscle of the rat. Fibers were measured within areas selected at random from sections taken from the same block of tissue. Variance within and between sections was subsequently established.

Between blocks from rats having undergone the same procedure. Variability in the size of muscle fibers measured within areas selected at random from sections taken from different blocks of tissue within the same animal.

Between rats, same or equivalent procedure. Fibers were measured from randomly selected areas within sections taken from blocks of tissue derived from different animals. The muscles were subjected to the same or equivalent treatment prior to freezing.

Between procedures. Restraining muscles prior to and during freezing did not significantly affect the results except the procedure involving holding the muscle between two pairs of forceps. However, the variability was high within and between sections and blocks from the same muscle. It is postulated that the variability is of technical rather than biological origin and may be the result of small focal contractions which occur along the fibers during freezing.
Knife chatter during thin sectioning of rat incisor enamel can cause periodicities resembling cross‐striations
Authors: Warshawsky H. , Bai P.
Published: February 2005

Cross‐striations are traditionally associated with the enamel rods in many species including man. Although these striations are obvious with light microscopy, their exact nature has been difficult to determine with the transmission electron microscope on thin sections of enamel. Thin section microscopy either reveals no structures that can be called cross‐striations, or shows periodic light and dark bands across the rods. Superficially, these bands resemble chatter artifact. To test this possibility, rat incisor enamel was used because cross‐striations have not been demonstrated on these enamel rods. Thin sections were prepared of enamel blocks oriented in various ways with respect to the cutting edge of the diamond knife. The sections showed either uniform enamel or light and dark bands over rod profiles or interrod enamel. Since these bands could be produced artifactually it is concluded that similar bands seen on enamel rods of other species may also be artifacts.
The tridimensional structure of Nissl bodies: A stereoscopic study in ventral horn cells of rat spinal cord
Authors: Beaudet Alain , Rambourg Alain
Published: February 2005

The tridimensional structure of rough endoplasmic reticulum was examined with both high and low voltage electron microscopes in large ventral horn cells of rat spinal cord, by combining stereoscopic techniques with the use of thick sections selectively impregnated with heavy metal salts. In all neurons examined Nissl bodies appeared as well defined clusters of densely stained and profusely anastomosed plate‐, ribbon‐, and thread‐like cisternae. Plate‐like cisternae were variable in size, often showed a shallow curvature, and usually ran in short parallel arrays, separated from one another by fairly constant intervals. All gave rise at their edges to several ribbon‐like extensions which occasionally decreased in width distally, turning into thin, thread‐like cisternae. Characteristically, these ribbon‐like structures would emerge at an angle from their plate of origin and smoothly curve away from the plane of the plate to merge with ribbons or threads arising from adjacent or more distant plates. Most plate‐like cisternae were found at the periphery of Nissl bodies and tended to be oriented parallel to their surface. In contrast, the center of Nissl bodies was almost exclusively occupied by a complex network of ribbon‐and thread‐like cisternae. It is suggested that the basic plate/ribbon association here described in spinal motoneurons might be a constant feature of Nissl body architecture in various neuronal types, while the size, orientation, and relative proportion of plate‐like cisternae may vary according to the metabolic state and/or functional specialization of the cells.
Immunolocalization of carbonic anhydrase isozymes in rat and mouse salivary and exorbital lacrimal glands
Authors: Hennigar Randolph A. , Schulte Bradley A. , Spicer Samuel S.
Published: February 2005

Carbonic anhydrase (CA) isozyme I and isozyme II have been localized with the immunoperoxidase bridge method in cells of mouse and rat salivary glands and exorbital lacrimal glands. Immunostaining proved optimal in Carnoy fixed specimens for some sites and in Bouin fixed glands for other sites. Staining in mouse largely resembled that in rat glands, but minor species differences were observed. Serous acinar cells in the submandibular gland stained uniformly and exclusively for CA I. From 50 to 100% of the serous acinar cells in the parotid glands evidenced content of both CA I and CA II. A minor population of serous acinar cells in the mouse exorbital lacrimal gland stained for CA I and CA II, but these glands in the rat failed to stain.

Immunostaining was observed in ducts in Bouin fixed glands. Some cells in striated ducts of submandibular and sublingual glands stained for CA I and CA II and other cells in these ducts were negative. Such cellular heterogeneity was also observed in excretory ducts of submandibular and sublingual glands. These findings thus demonstrate the presence of CA in two morphologically and functionally diverse cell populations in rodent salivary glands.

Immunolocalization of the CA isozymes in serous acinar cells and intercalated duct cells, presumably packaged in secretory granules, implies a role for this enzyme in salivary secretions whereas localization of CA in striated and excretory ducts suggests their traditional function in fluid and electrolyte transport.
Freeze‐fracture and lead ion tracer evidence for a paracellular fluid secretory pathway in rat parotid glands
Authors: Simson J. A. V. , Bank H. L.
Published: February 2005

The morphology and permeability of tight junctions of the three major epithelial constituents of rat parotid gland–acinus, intercalated duct, and striated duct–have been examined ultrastructurally. Acinar and intercalated duct junctions (including those surrounding intercellular canaliculi) averaged two to three sealing strands, whereas striated duct junctions had five to eight sealing strands. When the permeability of the junctional complex was probed by means of a recently devised lead ion tracer technique, acinar junctions were found to be very permeable, intercalated duct junctions were somewhat permeable, and striated duct junctions were essentially impermeable to the tracer. Thus, by both morphological and tracer‐permeability criteria, acinar tight junctions appear to be “leaky.” These data provide strong evidence that, in rat parotid glands, a potential paracellular secretory pathway exists in the acinar region for the transepithelial passage of fluid.
A cytochemical study on surface charges and lectin‐binding sites in epididymal and ejaculated spermatozoa of Macaca fascicularis
Authors: Fain‐Maurel M. A. , Dadoune J. P. , Reger J. F.
Published: February 2005

Changes in electronegative and electropositive surface charges and in lectin receptors (concanavalin A and wheat germ agglutinin) were investigated on sperm plasma membranes of the monkey (Macaca fascicularis) during epididymal transit and after ejaculation. Electronegative charges at pH 1.8, which were uniformly distributed on the whole plasma membrane of caput epididymal spermatozoa, increased mainly on the postacrosomal cap and the tail during epididymal passage. Electropositive charges at pH 9 were simultaneously found on the whole cell surface of caput epididymal spermatozoa with a stronger labeling on the acrosomal apex, the postacrosomal cap, and the tail. These charges disappeared during passage through the epididymis corpus. The surface distribution of lectin receptors varied inversely during epididymal transit with an increase in concanavalin A receptors and a decrease in wheat germ agglutinin receptors. These data show that changes in the monkey sperm plasma membrane during epididymal maturation occur in the distal corpus of the epididymis.
Seasonal changes in fine structure of the ductuli efferentes of the ground squirrel, Citellus lateralis (say)
Authors: Pundey Jeffrey , Fawcett Don W.
Published: February 2005

The morphoogical changes that the ductuli efferentes undergo during the seasonal breeding cycle of the ground squirrel Citellus lateralis were examined by means of electron microscopy. At the time of spermatogeneetic activity the epithelium of the ductuli was composed of highly differntiated principal and ciliated cells. Distinctive cytological features of these cells during this period were the presence of a heterogeneous collection of numerous membrane‐bound granules in principal cells and large accumulation of glygen in ciliated cells. Structurally these cells were specialized for movement of luminal contents and its modification by absorption and possible secretion. With the onset of testicular regression, profound changes occurred in both cell types. Initially the lumen of the ductuli became occluded by masses of apical cytoplasm protruded from principal and ciliated cells as well as by degenerating cells which had been sloughed from the epithelium. This leads eventually, by the time of complete testicular regression, to reduced ductuli containing cells smaller in size with fewer organelles than those present during the period of spermatogenesis. The membrane‐bound granules in principal cells and the accretions of glycogen in ciliated cells had now virtually disappeared. There was, however, a dramatic increase in dense inclusions representing deposits of lipofuchsin. As yet the cellular mechanisms controlling and effecting these dramatic changes in morphological appearance are unknwon.
Pleuroperitoneal canal closure in the rat
Authors: Gattone Vincent H. , Morse Dennis E.
Published: February 2005

Pleuroperitoneal canal development and closure were studied with light microscopy and transmission and scanning electron microscopy in 12.75‐ to 16‐day fetuses. The major chronological events described in this paper are (1) the caudal tips of the lung buds projecting to the pleuroperitoneal canal (12.75 through 13.50 days); (2) the caudal tips of the lungs becoming situated medial to the canal areas at 14 days; and (3) both canals becoming crescent shaped with a uniform diameter until closure. Concurrently, the developing diaphragm and associated pleuroperitoneal folds assume more caudal positions. Both canal regions are bordered by the liver, lung, gonadal ridge, and suprarenal glands. In addition, on the left side, the stomach and mesogastrium also border the early canal. The right canal closes before the left (right, 14.75–15 days; left, 15–15.25 days).

The results suggest that the pleuroperitoneal folds are pushed together, thereby closing the canals. This may be accomplished by one or a combination of the following: (1) enlargement of the liver pushing the ventral fold dorsad and a molding of the liver to the dorsal body wall caudal to the canal; (2) liver and thorax enlargement which appears to pull the dorsal fold taut against the central fold; and (3) a change in the orientation of the canal near the time of closure. Each canal is fully closed by the mergence of the dorsal and ventral fold mesothelia and mesenchyme. This study provides a basis for relating pleuroperitoneal canal development and closure to the surrounding organs and tissues.
Macroanatomy of the renicule of the bowhead whale (Balaena mysticetus)
Authors: Abdelbaki Yahya Z. , Henk William G. , Haldiman Jerrold T. , Albert Thomas F. , Henry Robert W. , Duffield Dennis W.
Published: February 2005

The macroanatomy of renicules and surrounding tissues from the kidneys of five Eskimo‐harvested bowhead whales, Balaena mysticetus, was examined. These renicules are similar in overall structure to those of other cetaceans and intermediate in size. There are several important differences including the presence of arcuate vessels within the sporta perimedularis, the extension of connective tissue from the sporta deep into the peripheral cortex, and the presence of very large, thin‐walled veins that occupy the interrenicular spaces. Arterial and venous plexuses outside the substance of the sporta reported in other cetaceans were not observed in the bowhead.
Immunocytochemical identification of cells containing insulin, glucagon, somatostatin, and pancreatic polypetide in the islets of langerhans of the guinea pig pancreas with light and electron microscopy
Authors: Baskin Denis G. , Gorray Kenneth C. , Fujimoto Wilfred Y.
Published: February 2005

Cell types contianing insulin, glucagon, somatostatin, and pancreatic polypetide were identified in guinea pig islets with light and electron microscopic immunoperoxidase staining. Cells containing immunostainable insulin (B cells) are located throughout the islets, including the islet periphery, and contain irregularly shaped granules (350–550 nm). Granule contents are of variable opacity and are often fragmented but not crystalloid. Cells containing immunoreactive glucagon (A cells) are found in the interior of islets and contain numerous shperoid electron‐opaque granules (250–350 nm). Cells containing immunoreactive somatostatin(D cells) have elongate, axonlike processes that end adjacent to islet capillaries. D cells, which are very numeous and distributed uniformly throughout the islet parenchyma, contain small spheroid granules (150–250 nm) of pale electron opacity. Cells with immunoreactive pancreatic polypeptide (F cells) are rare in islets but numerous among the exocrine parenchyma. F cells contain pale spheroid granules (100–200 nm). Morphological criteria are reliable indicators for A cells and B cells, but D cells and F cells require immunostaining for positive identification.
An improved perfusion technique for fixation of sheep myocardium
Authors: Smolich J. J. , Canale E. , Campbell G. R. , Walker A. M. , Adamson T. M. , Maloney J. E.
Published: February 2005

Although sheep have been widely used as models in the study of cardiac physiology, corresponding morphologic and morphometric data are scanty. For meaningful correlation of morphometric data with physiological information, it is desirable that fixation of the heart occur under controlled conditions. This paper describes a technique for in situ, retrograde aortic perfusion fixation of sheep myocardium under conditions of controlled pressure and minimal wastage of fixative. This is achieved by the application of snares around the brachiocephalic trunk and aortic arch, which are tightened at the start of the perfusion. These isolate the ascending aorta and the coronary vasculature from the remainder of the circulation and allow fixation of the whole heart at a controlled pressure. The method produces good fixation and contrast for transmission electron microscopy and is applicable to late‐gestation fetuses, lambs, and adult sheep.
The facial nucleus of the rat: Representation of facial muscles revealed by retrograde transport of horseradish peroxidase
Authors: Hinrichsen Colin F. L. , Watson Carol D.
Published: February 2005

The representation of facial muscle groups in the facial nucleus of rat was examined by retrograde transport of HRP. Motoneurons supplying muscle groups are arranged in longitudinal columns. Those supplying nasolabial muscles are located in the lateral and ventral intermediate segments, posterior auricular muscles in a medial column, platysma in an intermediate column; the lower lip and ocular muscles are in the ventral and dorsal segments respectively of the intermediate column. The posterior belly of the digastric muscle is supplied by motoneurons extending from the dorsal aspect of the facial nucleus to the caudal pole of the trigeminal motor nucleus.
Developmental age estimated by bone‐length measurement in human fetuses
Authors: Kelemen Endre , Jánossa Margit , Calvo Wenceslao , Fliedner Theodor M.
Published: February 2005

The lengths of 491 long bones of the extremities derived from 193 freshly delivered human fetuses of 7 to 22 weeks fertilization age were measured. Fetuses delivered after spontaneous abortion, twin pregnancy, or known maternal disease were excluded. The correlation between fetal age (measured by crown‐rump length) and bone length was linear. The term “developmental age” was used for bone length‐derived age values. Developmental age can be determined from the length of even a single bone, i.e., when mechanical injury of the delivered fetus inhibits crown‐rump length measurement. The results could aid researchers dealing with human embryology, clinicians performing fetal tissue transplantation, and could be applied in forensic medicine as well.
Postpartum regeneration of the guinea pig endometrium: Relationship to serum estradiol and progesterone concentrations
Authors: Garris David R.
Published: February 2005

The pattern of cell mitotic activity in the uterus of postpartum, pregnant guinea pigs was correlated with the associated changes in serum progesterone and estradiol levels between days 1–8 of pregnancy. Stromal and glandular epithelial mitotic patterns mimicked the associated fluctuations in serum progesterone and estradiol levels, respectively. No changes in myometrial mitotic activity were observed. The luminal epithelial mitotic index was apparently sensitive to the relative change in the ratio of progesterone‐to‐estradiol in circulation. These studies indicate that postpartum, endometrial preparation for blastocyst implantation depends on the proper priming of the uterus by both progesterone and estradiol in the guinea pig.
Pigmented cells in the leptomeninges of the cat
Authors: Morse Dennis E. , Cova John L.
Published: February 2005

Cells laden with pigment granules are described in the leptomeningeal tissues of the cat and kitten. These cells can be identified consistently by gross observation following vascular perfusion. The fusiform or stellate pigmented cells are most often found in association with the outermost layers of the arteries of the subarachnoid space. They are typically separated from the cerebrospinal fluid by an attenuated layer of pial cells. Vessels that are described as having pigmented cells along their course are the anterior and posterior cerebellar; the anterior, middle, and posterior cerebral; and the basilar. Electron microscopic studies confirm the presence of abundant pigment granules. The pigment granules are the predominant component of the cytoplasm. Few organelles are demonstrable except for a large central nucleus. The data provide suppport for the concept of neural crest contribution to leptomeningeal structures. Identification of this isolated, easily defined population of melanocytes may provide a model for further studies of neural crest distribution as well as experimental approaches to melanogenesis and melanoma production and control.
The secretory pathway in the mouse epididymis as shown by electron microscope radioautography of principal cells exposed to monensin
Authors: Flickinger Charles J. , Wilson Kathleen M. , Gray Helen D.
Published: February 2005

The secretory pathway in principal cells of the mouse epididymis was studied using in vitro labeling and electron microscope radioautography of tissue exposed to the ionophore monensin. After a 5‐minute pulse of 3H‐leucine, control samples of caput epididymidis were incubated in a modified Krebs‐Ringer solution (MKRH medium), while experimental specimens were placed in the same medium, to which 1 μM monensin had been added. At intervals between 5 minutes and 4 hours, samples were fixed and prepared for electron microscope radioautography. Analysis of control specimens revealed heaviest labeling of the rough and the sparsely granulated endoplasmic reticulum early in the experiment followed by a fall in radioactivity, maximal labeling of the Golgi apparatus at 30 minutes, and a pronounced rise in the percentage of grains associated with the apical cell surface and the epididymal lumen beginning 1 hour after administration of precursor. In monensin‐treated epididymides, radioactive material accumulated in the Golgi region while the normal increase in labeling of the apical surface and the lumen was completely inhibited for at least 2 hours. The percentage of grains attributed to coated vesicles was also reduced in samples exposed to monensin. In contrast, labeling patterns of the abundant, sparsely granulated, endoplasmic reticulum and the rough endoplasmic reticulum were very similar in monensin‐treated and control specimens. The concomitant alterations in labeling of the Golgi apparatus and the lumen demonstrate that the Golgi apparatus participates in intracellular transport of secretory proteins in epididymal principal cells, and is not bypassed as previously suggested. The percentage of grains associated with the sparsely granulated endoplasmic reticulum suggests that much of the synthesis of secretory protein in the principal cells occurs in this organelle, and the lack of alteration of its labeling in the presence of a monensin‐induced block at the level of the Golgi apparatus indicates that the sparsely granulated endoplasmic reticulum lies before the Golgi apparatus in the secretory pathway. It is speculated that vesicles play a role in transport of secretory pathway. It is speculated that vesicles play a role in transport of secretory protein from the Golgi apparatus to the lumen.
Immunohistochemical analysis of the distribution of vimentin in human peripheral lymphoid tissues
Authors: Giorno Ralph
Published: February 2005

The distribution of the intermediate filament protein vimentin in peripheral lymphoid tissues was determined using a monoclonal antibody. Frozen sections of tissue were stained using an avidin‐biotin immunoperoxidase method. The antibody stained endothelial cells in spleen, lymph node, and tonsil. Unusual rod‐like structures were revealed in the sinusoid‐lining cells of the spleen. A variety of reticulum cells was detected, including fibroblastic reticulum cells, histiocytic reticulum cells (tingible body macrophages), and splenic marginal zone macrophages. Very few lymphocytes were immunoreactive. Only weak cytoplasmic immunoreactivity was observed in lymphocytes of the periarteriolar lymphocyte sheath of the spleen. The monoclonal antibody employed appears to be of limited usefulness in detecting normal lymphocytes, but is strongly reactive with endothelial structures and some types of reticulum cells.
Ultrasonic microdissection of the mouse mandible: Exposure of the vasculature of alveolar bone and myelinated axons of the pulp
Authors: Johnson Roger B. , Highison Gregory J.
Published: February 2005

The present scanning electron microscopic study describes a new method for the exposure of blood vessels of mouse alveolar bone and myelinated nerves of the dental pulp. This technique differs from others because it does not remove the periodontal ligament, allowing study of the vascular continuity between alveolar bone and periodontal ligament. Fixed and demineralized mandibles are digested with bacterial collagenase (1 mg/ml) at 37°C for 12 hours, exposed to buffered osmium tetroxide for 24 hours, and ultrasonicated at 80 kHz for 5 minutes. The technique demonstrates that the vascular distribution of the interdental and interradicular septa is different. Vessels pass horizontally through the interdental septum and are continuous with vessels of the adjacent periodontal ligament. Vessels of the interradicular septum branch from a central vessel, pass toward the adjacent periodontal ligament, and become continuous with its vessels. Thus, the pattern of vessel distribution of the interdental septum of the mouse has little similarity to that of man or of research animals. The present study provides an improved method for demonstration of bone vasculature and pulpal axons while retaining valuable anatomical landmarks.
Muscle fiber necrosis and regeneration induced by prolonged weight‐lifting exercise in the cat
Authors: Giddings C. J. , Neaves W. B. , Gonyea W. J.
Published: February 2005

For periods ranging from 26 to 87 weeks, the morphological characteristics of the flexor carpi radialis (FCR) muscle were examined in four cats trained to perform weight‐lifting exercise. Four untrained, sex and weight‐matched cats served as controls. The right FCR from each cat was surgically isolated, attached to a tension transducer, and set at its optimal length. The forelimb was perfused with 2% glutaraldehyde in 0.1 M cacodylate buffer. Small bundles of fibers were teased from their origin and insertion tendons and embedded in Epon. Spaced serial sections were used to examine the morphological features of the fibers for trained and control animals. Ultrastructural examination revealed muscle fiber degenerative changes, such as pyknotic nuclei, disruption of the sarcolemma, vacuolation, and disorganization of myofilaments. Such changes were observed at a higher frequency in trained muscle than in control muscle. Spaced serial sections of fiber bundles showed that the degree of degeneration varied along the length of the fiber. Fiber area measurements showed that trained muscle had both larger and smaller fibers than control samples. The very small fibers observed in the trained muscle were considered to be regenerating or “new” fibers since they had not undergone degenerative changes. “Satellite‐like” cells were observed in trained muscle. Such cells resembled satellite cells but also contained developing myofilaments. Since evidence of degeneration‐regeneration was observed in control samples, but at a lower frequency, it was postulated that weight‐lifting exercise accelerates muscle fiber turnover in the cat FCR.
Bone healing after amputation of mouse digits and newt limbs: Implications for induced regeneration in mammals
Authors: Neufeld Daniel A.
Published: February 2005

Postamputational healing was compared in nonregenerating and regenerating animals to determine whether bone healing might interfere with a regenerative response in mice. More than 150 mouse toes and 100 newt limbs were examined at the light microscope level. Stages of normal bone healing with approximate times of occurrence were established. Major differences in healing of these two species were seen. The periosteum produced hyaline cartilage, woven bone, and chondroid bone in mice, but only hyaline cartilage in newts. The endosteum produced woven bone in mice but no new growth in newts. Dead bone persisted in mice but was removed in newts. The marrow cavity became sealed in mice but remained open in newts. Despite these differences both animals produced skeletal tissue distal to the amputation plane. Woven bone formed distal to the amputation plane of mice. Cartilage formed distal to the amputation plane of newts, but cartilage was never seen distal to the plane of mice. Results of previous studies reveal that cartilage can be formed distal to the amputation plane of experimentally treated mice. Thus, although it does not regenerate, mouse bone is capable of producing, distal to the amputation plane, the type of skeletal tissue which appears at that location during an epimorphic regenerative response. This observation, in combination with other experimental results, indicates that both skeletal and soft tissues at the amputation site of treated mammals can resemble comparable tissues of newt limbs at an early stage of regeneration.
The narrowing of high endothelial venules of the rat lymph node
Authors: Bélisle C. , Sainte‐Marie G.
Published: February 2005

The lymph node contains blood vessels of a special type, termed “high endothelial venules” (HEVs), which are involved in the process of lymphocyte recirculation. In standard tissue sections, many HEVs exhibit a nearly closed or closed lumen containing small lymphocytes but few, if any, erythrocytes. The question arose as to whether the appearance of HEVs in tissue sections is influenced by the routine method of animal sacrifice and/or of tissue processing. Therefore, the present work investigated the effects on HEVs of sacrificing rats as well as of excising and fixing their nodes with various procedures. It was observed that procedures involving animal bleeding or blood loss from nodes increase the percentage of HEVs exhibiting a nearly closed or closed lumen. The results further revealed that the endothelial thickness and other morphological features of HEVs are modified by this artifactual narrowing of HEVs. The possible significance of the phenomenon is discussed.
Occurrence of bone fractures and parathyroid hyperplasia in paraphysectomized frogs (Rana catesbeiana)
Authors: Nelson Stanley R. , Foltz Floyd M. , Camarata Paul , Sarras Michael P.
Published: February 2005

The physiological role of the amphibian paraphysis was studied by removing the paraphysis from bullfrog tadpoles (Rana catesbeiana) and observing change in frog weight, bone development, and parathyroid glands 22 months later. Development was similar in control and paraphysectomized frogs until 6 months when the experimental frogs began to show greater weight gain which persisted for the remaining 16 months. At the time of sacrifice (22 months after paraphysectomy), the parathyroid glands of the experimental frogs were enlarged with a tenfold increase in wet weight and a sevenfold increase in dry weight. The glands from experimental frogs had numerous cysts filled with eosinophilic staining material; histologically the cell nuclei were rounded and the cytoplasm was vesiculated. At the time of sacrifice the experimental frogs had knoblike deformities along the shafts of the long bones. These deformities were due to callus formation around spontaneous bone fractures as revealed by X‐rays of the tibia‐fibulas and femurs. The dry weight was greater but calcium content less in femurs from experimental frogs. These findings indicate the paraphysis plays a role in calcium metabolism, possibly by producing a factor necessary for calcium action on cells.
Heterogeneous distribution of glycoconjugates in human kidney tubules
Authors: Hennigar Randolph A. , Schulte Bradley A. , Spicer Samuel S.
Published: February 2005

Parafin sections of normal human kidney were stained with a battery of ten lectin‐horseradish peroxidase conjugates. Staining of proximal tubules revealed a relatively uniform distribution of glycoconjugates having bi‐ and/or triantennary N‐linked sugar chains as well as terminal β‐galactose and α‐fucose in all cells. In contrast, terminal α‐ and β‐galactose and α‐fucose were localized in only some cells of the thin limbs, whereas N‐linked sugar chains and terminal α‐N‐acetylgalactosamine occurred in all cells. In the ascending thick limbs, terminal α‐N‐acetylgalactosamine was found in some cells and N‐linked sugar chains and terminal β‐galactose were present in all cells. The distal convoluted tubules contained N‐linked oligosaccharides and terminal β‐galactose in all cells. Terminal α‐N‐acetylgalactosamine was found in some but not all profiles of distal convoluted tubules in a few kidneys. In the initial (connecting) segment of cortical collecting ducts, cells varied in their content of glycogen and glycoconjugates with terminal α‐and β‐galactose, α‐fucose and α‐N‐acetylgalactosamine, but cells in this segment evidenced uniform localization of N‐linked sugar chains. A similar distribution of sugars occurred in the medullary ray segment of cortical collecting ducts, except for terminal β‐galactose which was present in all cells. In the medullary collecting ducts, there was also considerable cell‐to‐cell variation in the content and distribution of glycogen and glycoconjugates having N‐linked sugar chains, terminal α‐galactose, α‐fucose, α‐N‐acetylgalactosamine, and the disaccharide galactose‐(β 1 → 3)‐N‐acetylgalactosamine. The content and distribution of glycoconjugates in the nephron varied only slightly between kidneys from different individuals, but individual variability was extensive in the collecting ducts. The reasons for these individual differences have not been determined, however. Cellular heterogeneity of glycosubstances within the different regions of the human kidney correlates with similar findings in other mammals and implies diverse functional roles for the various types of complex carbohydrates in the kidney.
An exceptionally high density of muscle spindles in a slow‐tonic pigeon muscle
Authors: Rosser Benjamin W. C. , George John C.
Published: February 2005

Histochemical and histological observations on the tiny wing muscle, M. coracotriceps, of the pigeon revealed a remarkably high density of muscle spindles (14,582 ± 2,302/g of muscle) – approximately 15 times the highest densities hitherto reported for any muscle. Furthermore, all of the extrafusal fibers of this muscle were of the slow‐tonic variety. This unique muscle probably functions as a mechanoreceptor extremely sensitive to changes in its own length.
Blood supply of the caudal mediastinal lymph node in sheep
Authors: Albertine Kurt H. , Wiener‐Kronish Jeanine P. , Staub Norman C.
Published: February 2005

We investigated the arterial supply to, and the venous drainage from, the caudal mediastinal lymph node (CMN) in 18 anesthetized and exsanguinated sheep. The purpose of this gross anatomic investigation was to determine the CMN's blood supply so that a structural base can be used to interpret studies of the bronchial circulation's role in the pathogenesis of pulmonary edema. In ten sheep, we cannulated the bronchoesophageal artery at its origin from the aorta and injected Microfil. This artery, which branches into cranial and caudal divisions 2–4 mm distal to its origin, supplied the esophagus, trachea, bronchi, and visceral pleura. The CMN is supplied by the caudal division, as it courses between the CMN and aorta. Microfil injected through the thoracic aorta did not enter the CMN when the bronchoesophageal artery was ligated at its origin. These results indicate that only the bronchoesophageal artery supplies the CMN. In eight sheep we cannulated the vein at the head of the CMN (dorsal mediastinal vein) and injected Microfil, both peripherally and centrally. Peripherally, injected veins reached the CMN and esophagus. The dorsal mediastinal vein extended posteriorly to the CMN in three of the eight sheep, eventually emptying into the left azygos vein near the diaphragm. Centrally, the dorsal mediastinal vein joined the left azygos vein near the heart in six of the eight sheep, including the three in which the dorsal mediastinal vein extended posteriorly to the CMN. In the remaining two sheep the dorsal mediastinal vein drained centrally into the right azygos vein. We conclude that the bronchoesophageal artery supplies the CMN and that either the left or right azygos vein drains it.
Three‐dimensional reconstruction of a small‐granule paracrine cell cluster in an adult hamster bronchus
Authors: Pearsall Allan Dorland , Hoyt Richard Francis , Sorokin Sergei Pitirimovitch
Published: February 2005

Amine precursor uptake and decarboxylation (APUD) small‐granule cells were stained by periodic acid‐Schiff (PAS)‐lead hematoxylin in 0.5‐μm etched Epon sections of adult hamster lung fixed for transmission electron microscopy. The leading edge of a small‐granule cell cluster was identified in a segmental bronchus as a single PAS‐positive cell. From 256 serial thin sections through its entirety, a three‐dimensional wooden reconstruction of the cluster and morphometric estimates of the apical and basal surfaces, cell volume, and intracytoplasmic distribution of mitochondria and small granules was made. Of moderate size, the body consisted of 16 small‐granule cells, 11 forming its ovoid core with five outlying cells diverging at the margin; these were pyramidal, possessing wide bases and thin apical processes. At the bronchial surface, processes from the 11‐cell core emerged together, whereas the divergent cells emerged in groups of two and three. Ten Clara‐like cells and one ciliated cell encircled the core Altogether they formed a pseudostratified epithelium in contrast to the surrounding simple columnar epithelium. Deeper in the cluster, numerous cytoplasmic extensions interdigitated with those from adjacent cells, and toward the base the Clara‐like and APUD cells were increasingly interposed. In marked contrast to the apical cytoplasm, the infranuclear cytoplasm of the latter was densely packed with ca. 1,000 Å electron‐dense granules; and the basal, presumptively secretory face of each cell was five to six times greater than the area exposed to the bronchial lumen. Judged by granule size and ultrastructure, only one APUD cell type was recognized in the reconstructed cluster. Beneath it many fibrocytic processes were separated from the APUD cells by only the thickness of the basal lamina. Two fascicles of smooth muscle approached the cluster within 0.4–0.8 μm. Unmyelinated nerve fibers came as close but contacted only the muscle. Capillaries, in contrast, came no closer than 15 μm from the base of the body. Evidently, (1) fibrocytes and smooth muscle are more likely targets for secretions from such a paracrine body than cells reached through the bloodstream, and (2) not all small‐granule cell clusters are innervated.