bluuebunny/crossref_metadata_2025 huggingface dataset:
Use of the L‐proline analog, L‐azetidine‐2‐carboxylic acid (LACA) to analyse embryonic growth and determination and expression of the chondrogenic phenotype in vivo and in vitro
Authors: Hall Brian K.
Published: February 2005

The L‐proline analog, L‐azetidine‐2‐carboxylic acid, (LACA) was injected into embryonated eggs of the common fowl, Gallus domesticus at daily doses of 350 μg/egg on one or several days between 8 and 12 days of incubation. Treatment at nine‐days of incubation preferentially retarded embryonic growth to the twelfth day but recovery of growth rate occurred by 15 days of incubation. Relationships between growth and LACA‐inhibited aspects of collagenogenesis are discussed.

The earliest aged embryos from which isolated stem cells from membrane bones will form secondary cartilage is ten days of incubation. Secondary chondro‐genesis on the quadratojugal, a membrane bone of the skull, was inhibited by treatment of whole embryos with LACA at nine days of incubation but not by treatment at eight days. We concluded that an event involving collagen began at nine days of incubation, was blocked by LACA, and was part of the process of chondrogenic determination of these stem cells. Addition of LACA to the medium in which already determined stem cells from the quadratojugal were cultured prevented expression of the chondrogenic phenotype. This proline analog is then a useful probe for events relating both to determination and to expression of the differentiated state, and allows conclusions to be drawn regarding the role of col‐lagenogenesis in these events.
The ultrastructure of normal myogenesis in the limb of the mouse
Authors: Platzer Ann C.
Published: February 2005

The ultrastructure of myogenesis in the mouse hind limb has been studied from day 12 to birth. Mononucleated cells with myofilaments are small and infrequent during myogenesis and never line myotubes. Only mononucleated cells without myofilaments cover the myotubes and are involved in mass fusion. These mononucleated cells are pleomorphic and undifferentiated during early myogenesis. They have a heterochromatic nucleus and many accumulate mitochondria and lengthen during days 16‐18. After day 18 they are normally elongate with a heterochromatic nucleus and packed with free ribosomes. The multinucleated cell development may be divided into four stages. 1. Immature myotube (days 14‐15). Their fibrils are small, out of register and some poorly defined. Many myofilaments are not in rigid hexagonal alignment. The sarcoplasmic reticlum is simple and randomly oriented and triads are absent. Large clumps of glycogen occur between euchromatic nuclei which are in chain formation. 2. Mature myotube (days 16‐18). Small groups of fibrils show alignment. Glycogen granules and sarcoplasmic reticulum become numerous between fibrils. Triads are sparse and mitochondria cluster in subsarcolemmal regions and between nuclei. 3. Young myofibers are present by day 19. More fibrils are aligned and compact. The filaments are in a rigid hexagonal array, the glycogen is dispersed and nuclei are peripherally located and moderately heterochromatic. Triads are frequent but often obliquely oriented and mitochondria are elongate and numerous between fibrils. 4. Mature myofibers occur postnatally (2 weeks).
Development of the fetal pituitary‐testicular system based on observation of leydig cells in encephalectomized, hypophysectomized and control fetal rats
Authors: Eguchi Yasunobu , Arishima Kazuyoshi , Nasu Tetsuo , Toda Mineyuki , Morikawa Yoshio , Hashimoto Yoshiyuki
Published: February 2005

The time of onset of brain regulation of the pituitary‐Leydig cell system in fetal rats was assessed by fetal encephalectomy, which allowed the pituitary to persist in situ. The effects of encephalectomy were compared with those of fetal hypophysectomy (surgical decapitation). The parameter for in terpretation of these effects was the collective volume of Leydig cells, measured by the method of Chalkley ('43). The normal increase in the collective volume of Leydig cells in fetuses encephalectomized on day 17 of gestation and autopsied on day 18 was not retarded, whereas that in decapitated fetuses of the same age was retarded. In all other one‐day experimental periods (day 18–19, 19–20, 20–21, and 21–22), the increase in volume was retarded to approximately the same extent in encephalectomized as in decapitated fetuses. The collective volume of Leydig cells continued to increase to some extent without the brain until day 20, after which it ceased to increase. The results suggest that in fetal rats, the brain control of the pituitary‐Leydig cell system begins to operate from day 18 of gestation, when the day following overnight mating was designated as day 1 of gestation.
Rapid isolation of chloride cells from pinfish gill
Authors: Hootman Seth R. , Philpott Charles W.
Published: February 2005

Enriched fractions of chloride cells with good ultrastructural integrity have been obtained from gill filaments of the euryhaline teleost, Lagodon rhomboides. The branchial epithelium from seawater‐adapted fish was dissociated by gentle mechanical means in a Ca++, Mg++ ‐free balanced salt solution. Density gradient centrifugation of the mixed cell suspensions through a Ficoll gradient yielded a fraction containing between 50 and 70% chloride cells. This fraction showed a 3‐ to 4‐fold enrichment over comparable gill homogenate values for sodium plus potassium‐activated adenosinetriphosphatase, (Na+, K+‐ATPase), an enzyme concentrated in chloride cells. Isolation of chloride cells from fish adapted to one‐third seawater was less successful, due to the smaller size and reduced number of these cells, although fractions with at least a 2‐fold enrichment of the enzyme were obtained. These results continue to support the belief that chloride cells are responsible for the osmoregulatory activity associated with the branchial epithelium of teleosts and that this vital function is mediated through the activity of the transport associated enzyme, Na+, K+ ‐ATPase, the specific activity of which increases with osmotic stress.
Heterogeneity of the MtTW15 mammosomatotropic tumor. I. Light microscopic evaluation of cell types by means of immunocytochemistry, morphometric quantitation, fluorescence cytophotometry and radioimmunoassay
Authors: Parsons Jonathan A. , Erlandsen Stanley L. , Carpenter Anna‐Mary , Debault L. E.
Published: February 2005

Large MtTW15 pituitary tumors produced 200‐ to 800‐fold elevations in serum growth hormone (GH) and prolactin (PRL) levels. Female tumor hosts showed doubling in body weight, milk secretion, and a 2‐fold hepatosplenomegaly. Pituitaries of host animals were reduced by about 50% in both weight and concentrations of GH and PRL. Large tumors were well‐encapsulated, multinodular and showed variable amounts of necrosis and hemorrhage. Cytofluorometric analysis revealed a range of 100‐fold in nuclear DNA content of tumor parenchymal cells which were chromophobic, pleomorphic and frequently mitotic. Concentrations of hormones in tumors were less than in normal pituitaries and highly variable with the ratio of GH/PRL ranging up to 30‐fold within the same tumor. Immunostaining and linear scanning quantitation showed that about 50% of the tumor cells contained immunodetectable hormones. Comparison of immunostained adjacent sections showed that hormone‐containing tumor cells were pleomorphic, unequally distributed within nodules, lacking in distinctive identifying morphological characteristics and that they contained GH or PRL but not both hormones simultaneously. Collectively our results show that large MtTW15 tumors are comprised of a markedly heterogeneous population of tumor cells and they suggest that the hormone‐containing cells are monohormonal secreting tumor cells which can produce GH or PRL but not both hormones.
Gross and histological variations along the length of the rat vas deferens
Authors: Hamilton D. W. , Cooper T. G.
Published: February 2005

The gross morphology of the vas deferens of the rat and the changes that occur along its length are reported. It is shown that the organ can be divided into proximal, distal and terminal portions. Each portion is histologically unique and is situated in a different part of the body. The differences are discussed in relation to the function of the organ and their possible role in the consequences of vasectomy.
Actin‐ and myosin‐like filaments in rat brain pericytes
Authors: Lebeux Yvi J. , Willemot Joan
Published: February 2005

Heavy meromyosin (HMM) labeling was used to identify the nature of the filaments which form bundles in the cytoplasm of the pericytes in brain tissue. Rat brain tissue pieces were incubated in glycerol solutions at 4°, and then transferred into buffer (pH 7.0), (1) without HMM, (2) with HMM, (3) with HMM + 5 mM ATP, and (4) with HMM + 2.5 mM Na+ pyrophosphate. In pericytes from untreated tissue, smooth‐surfaced microfilaments, averaging 6 nm in diameter, appear to branch and anastomose and to anchor on the plasma membrane. After exposure to HMM, the number and the density of the microfilaments are strikingly increased. These tightly‐packed microfilaments are now heavily coated with exogenous HMM thus increasing in width to 18–20 mm. They intertwine in closely‐woven networks. After incubation in HMM solutions containing ATP or Na+ prophosphate, they are no longer coated with thick sidearms. It can thus be concluded that these microfilaments are of actin‐like nature. In addition, after incubation in ATP, they are intermingled with, and converge onto the surfaces of, thick, tapered filaments, which we have tentatively identified as of myosin‐like nature. Thus, it appears that certain of the major elements necessary for contraction are present in brain pericytes.
Ultrastructural identification of collagen and glycosaminoglycans in notochordal extracellular matrix in vivo and in vitro
Authors: Kenney M. Cristina , Carlson Edward
Published: February 2005

Notochordal extracellular matrix consists of a continuous basal lamina, amorphous materials and microfibrils embedded in a ground substance of low electron density. Together they comprise the notochord sheath and are of considerable interest because of their suspected role in early embryonic tissue interactions. The notochord is particularly well‐suited to morphological investigation of extracellular matrix because it is one of the few embryonic epithelia which produces ultrastructurally recognizable stroma in vitro without the advantage of a collagenous substratum. Furthermore, these matrix components produced in vitro are morphologically identical to those observed in vivo. The present study uses ruthenium red staining to demonstrate that notochordal microfibrils exhibit collagen‐like cross‐banding patterns both in vivo and in vitro. Collagenase and testicular hyaluronidase digestion studies designed to localize collagen and glycosaminoglycans show a reduction of microfibrillar diameters by 30‐35%. Furthermore, these enzyme treatments frequently result in enhanced striations of microfibrils. When cis‐hydroxyproline (a proline analog) or beta‐aminoproprionitrile (BAPN, a lathyrogenic compound) is added to the culture medium, a similar reduction in microfibrillar diameters is seen. Moreover, increased ruthenium red‐positive surface coats and large collagen fibrils are frequently present in BAPN‐treated cultures, implying a stimulatory metabolic effect.

We conclude that most, if not all, notochordal extracellular matrix components are composed of both collagen and glycosaminoglycans and suggest that the entire extracellular matrix should be considered a macromolecular composite which acts in concert to induce or stabilize developmental interactions.
Cilia of neonatal articular chondrocytes incidence and morphology
Authors: Wilsman Norman J. , Fletcher Thomas F.
Published: February 2005

Cilia in neonatal canine articular chondrocytes were studied using morphometric techniques and transmission electron microscopy. The cilia in chondrocytes were morphologically similar to cilia in a variety of other cell types. A chondrocytic cilium consisted of a basal body and a ciliary shaft. The cylindrical basal body was 0.21 μm (S.D. = 0.01 μm) in diameter, 0.50 μm (S.D. = 0.03 μm) in length and contained nine microtubular triplets. The ciliary shaft was 0.196 μm (S.D. = 0.02 μm) in diameter and 1.76 μm (S.D. = 0.80 μm) in length. The number of microtubular doublets in the ciliary shaft varied depending on where along the length of the shaft the section was taken.

This study demonstrates that on the average the frequency of cilia in neonatal articular chondrocytes, as estimated stereologically, was about one cilium per cell.
Perisynaptic satellite cells in the developing and mature rat soleus muscle
Authors: Kelly Alan M.
Published: February 2005

In mature rat soleus muscle it is shown that satellite cells are not evenly distributed over the surface of myofibers but are more numerous in the vicinity of the motor endplate. In this location they commonly lie close to the post synaptic membrane where they are termed perisynaptic satellite cells. In developing muscle several satellite cells may be seen close to the endplate and give the impression of limiting the spread of the axon over the myofiber. In addition these satellite cells make close plasmalemmal contact with Schwann cells and appear as a continuation of the Schwann sheath onto the surface of the myofiber.
Secretagogue‐mediated discharge of nerve growth factor from granular tubules of male mouse submandibular glands: An immunocytochemical study
Authors: Simson J. A. V. , Hazen D. , Spicer S. S. , Murphy R. A. , Young M.
Published: February 2005

Submandibular glands of male mice were stained for nerve growth factor by light microscopic immunocytochemistry. Nerve growth factor (NGF) was present in the granules of granular tubule cells, with the immunoreactive material often concentrated at the periphery of granules. Administration of the α‐adrenergic agent, phenylephrine, to animals resulted in a marked depletion of NGF‐containing granules from granular tubules. Some release also occurred following administration of the β‐adrenergic agent, isoproterenol. Cholinergic stimulation (pilocarpine) did not result in appreciable loss of immunoreactive granules from these cells. In vitro results were not as clear cut, immunocytochemically, as those obtained with intact animals. It is concluded that discharge of NGF from male mouse submandibular glands is mediated predominantly by α‐adrenergic activation, and that this phenomenon is readily demonstrated in the intact animal.
Surface morphology of bone marrow lymphocytes. I. Scanning electron microscopy of small lymphocytes bone marrow and spleen
Authors: Kammerer W. A. , Osmond D. G.
Published: February 2005

Cell separation techniques and scanning electron microscopy (SEM) were used to characterize the surface morphology of small lymphocytes in mouse bone marrow. Lymphocyte‐rich fractions and unfractionated suspensions of bone marrow and spleen cells from 9‐10‐week‐old C3H male mice were glutaraldehyde‐fixed, syringed onto gelatin‐coated silver membranes, dehydrated in ethanol, infiltrated with amyl acetate, critical point dried, coated with gold‐palladium and examined by SEM. High proportions of cells were retained on the membranes. Purified spleen small lymphocytes showed unimodal distribution curves for cell diameter (mode, 3.4 μm) and for number of surface microvilli (mode, 55‐60). Bone marrow small lymphocytes were identified initially in lymphocyte‐rich marrow fractions and in erythroblast‐depleted marrow from polycythemic mice as well as in normal whole marrow. The cells resembled spleen small lymphocytes in size distribution and they showed microvilli. However, the number of visible microvilli was lower on small lymphocytes in the bone marrow (mode, 35‐40) than in the spleen. While in each small lymphocyte population the total number of microvilli was greater on larger cells than on smaller ones, the density of microvilli per unit area of cell surface tended to decrease with increasing cell size. The results establish that the small lymphocytes in mouse bone marrow, mainly locally‐produced immature cells, have villous surfaces, but the number of microvilli per unit cell surface area is less than that on peripheral small lymphocytes, as seen in the spleen. Neither in the bone marrow nor in the spleen are subpopulations of small lymphocytes distinguishable solely by numbers of microvilli. The findings suggest that microvilli on bone marrow small lymphocytes may undergo further development during post‐mitotic maturation, surface receptor expression and migration of the cells to peripheral lymphoid tissues.
Distribution of surface coat material on nasal folds of mouse embryos as demonstrated by concanavalin A binding
Authors: Burk Dorothy , Sadler T. W. , Langman Jan
Published: February 2005

3H‐concanavalin A and the concanavalin A‐horseradish peroxidase staining technique were used to study the distribution of surface coat material on the epithelium of the nasal folds and nasal groove of mouse embryos. In stages shortly before and during epithelial fusion concanavalan A stained or labeled material was present at apical surfaces of epithelial cells of the nasal groove and nasal folds. Silver grains, representing bound 3H‐concanavalin A, were counted in defined areas of the nasal groove and presumptive fusion area in both anterior and posterior regions of the nasal folds. For both stages examined there was a significant increase in the amount of 3H‐concanavalin A bound by presumptive fusion areas in posterior regions of the nasal folds as compared with anterior regions; i.e., the amount of surface coat was greater in the region just prior to the point of contact between the nasal folds. This finding is consistent with results from investigations of palatal shelf and neural fold fusion which suggest that increased synthesis of surface coat material is associated with adhesion and fusion of epithelial folds and shelves.
A qualitative and quantitative study of rete ovarii development in the fetal rat: Correlation with the onset of meiosis and follicle cell appearance
Authors: Stein Larry E. , Anderson Conwell H.
Published: February 2005

Development of the rete ovarii and its contribution to the cells of the ovary were examined in fetal rats. Histochemical and autoradiographic techniques were used for the observations between days 15 and 21 of gestation. The data presented indicate that the rete system contributes somatic cells to the ovary before birth.

The basement membrane which surrounds the cuboidal epithelium of the mesonephric tubules immediately adjacent to the ovary becomes discontinuous on day 15 of gestation. The mesonephric epithelial cells in this region form a knot or clump of pleiomorphic cells, with no apparent tubular organization, and this clump later becomes surrounded by a basement membrane. On day 17 of gestation the newly established fetal rete ovarii is comprised of three regions; (1) the extraovarian mesonephric tubules (ER), (2) intraovarian cords of flattened epithelioid cells which surround the oogonia (IR), and (3) a knot or clump of cells connecting the ER and IR regions (CR). The entire rete system is enclosed by a continuous basement membrane as defined by Periodic Acid‐Schiff Reagent techniques.

Autoradiographic and quantitative analyses demonstrate that the ER tubule cells proliferate and are incorporated into the other regions of the rete system. These processes begin on day 17 and continue until at least day 21 of gestation. The role these mesonephric tubule cells may play in the regulation of meiosis and their early contribution to the presumptive granulosa cell population is discussed.
Fine structure of the adrenocortical homologue in the north American eel and modifications following seawater adaptation
Authors: Bhattacharyya Tapan Kumar , Butler David Gordon
Published: February 2005

The ultrastructure of the adrenocortical homologue (AH) of the north American eel (Anguilla rostrata) was studied from freshwater and long‐term (1.5 years) seawater (SW) adpated animals. The AH tissue situated in the wall of cardinal veins is surrounded by a thin layer of collagenous capsule; in the region away from the vein wall, parenchymal cells are separated by interstitial lacunae containing collagen bundles, capillaries, chromaffin cells and nerve fibers often applied closely to the surface of AH cells. The free surface of the cell near the vein wall, capillaries or interstitial space extends numerous slender microplicae. The cytoplasm is characterized by the presence of mitochondria with tubular cristae, a network of smooth endoplasmic reticulum, a few cisternae of rough surfaced endoplasmic reticulum, well developed Golgi apparatus, coated vesicles, centrioles, cilium, filaments, microtubules, dense bodies of variable nature and a scarcity of liposomes. The cell nuclei possess invaginated cytoplasmic pseudo‐inclusions. Electron histochemical reaction for free cholesterol revealed the occurrence of needle‐shaped crystals mainly associated with surface microplicae and smooth endoplasmic reticulum, which seems to be the major organelle for storage or synthesis of this steroid precursor. SW animals indicated ultrastructural signs of stimulated steroid synthesis and secretion, i.e., high degree of pseudo‐follicle formation, increased electron density of mitochondria, greater abundance of lysosomal dense bodies, hyperactivity of Golgi apparatus and dilation of smooth endoplasmic reticulum tubules. Some SW fishes showed extensive deposition of osmiophilic inclusions in the mitochondria and stacks of elongated cup‐shaped mitochondria. Chronic seawater acclimation enhances AH activity as judged by ultrastructural criteria with ultimate mitochondrial degeneration resulting possibly from prolonged cortisol hypersecretion; the latter may be linked with physiologic re‐adjustment of ionic transfer mechanism in hyperosmotic medium.
Ultrastructure of the apocrine‐sebaceous anal scent gland of the woodchuck, Marmota monax: Evidence for apocrine and merocrine secretion by a single cell type
Authors: Smith Janet D. , Hearn Gail W.
Published: February 2005

Light and electron microscope studies of the woodchuck anal scent gland revealed that it is composed of apocrine and sebaceous components emptying into a common duct. In the apocrine acini, the single secretory cell type showed evidence of both merocrine and apocrine secretion. Merocrine secretion resulted in the release of the contents of apical secretory granules while apocrine secretion released apical caps of cytoplasm by a process involving the following: (1) formation of an apical cap, usually containing no organelles or secretory granules; (2) appearance of a single row of flattened vesicles forming an incomplete barrier between the apical cap and the remaining cell cytoplasm; and (3) fusion between vesicles and plasmalemma, causing progressive constriction of the neck of the apical cap and eventual cap release. Since both merocrine and apocrine secretory processes have been reported in three other types of apocrine glands, it is likely that the occurrence of both processes in a single cell is a general characteristic of apocrine cells.

Several features apparently unique to these particular apocrine cells were observed, including secretory granules of a single morphological type and a population of small dense‐cored basal vesicles of unknown function. Therefore, it would appear that, just as with merocrine cells, apocrine cells from different types of glands also have distinctive morphologies which probably reflect real differences in their functions and products.
Short‐term effects of androgen withdrawal on the structure of different epithelial cells in the rat epididymis
Authors: Moore H. D. M. , Bedford J. M.
Published: February 2005

Rat spermatozoa are highly dependent on the milieu of the normal epididymis for their maturation and survival, and die within a few days after androgenic support of the epididymal epithelium is withdrawn. The immediate changes in the ultrastructural organization of the epithelial cells of the rat epididymis, 2, 4, 6 and 14 days following castration have been monitored by morphometric analysis of localized regions of the caput and cauda epididymidis. While castration results in greater endocytosis by principal cells (Moore and Bedford, '79), many of their early structural changes following androgen withdrawal (disappearance of vesicles from the cell apex, reduction in rough endoplasmic reticulum, a drop in the volume of the Golgi cisternae and increase in lysosome content) seem indicative of inhibition of a secretory function. By contrast with the regressive response of the principal cell, the ultrastructure of clear cells in the cauda and of apical cells in the caput region appeared unchanged up to 14 days after castration. The implications of this evidence for specialized functions, and the suggestion of a differential androgen dependence among major cell types of the epididymal epithelium, are discussed briefly.
Fine structure of the oxynticopeptic cell in the gastric glands of an elasmobranch species (Halaelurus chilensis)
Authors: Rebolledo Ivan M. , Vial Juan D.
Published: February 2005

Gastric mucosa of an elasmobranch species was examined by electron microscope. The gastric glands contain one form of cell whose fine structure is similar to the cell that secretes both hydrochloric acid and pepsinogen of the amphibian gastric glands proper. These oxynticopeptic cells are characterized by: (a) a luminal surface with long projections of cytoplasm having dilatations in their thickness; (b) a tubulo‐vesicular system in the apical cytoplasm; (c) a great number of mitochondria, some of which are of great length; (d) a well developed granular endoplasmic reticulum and a conspicuous Golgi apparatus; and (e) a large nucleus with a conspicuous nucleolus. A fourth part of the cells are binucleated. Physiological implications of some of these ultrastructural features are discussed.
Morphologic variations and aging in the atrioventricular conduction system of large breed dogs
Authors: Sandusky George E. , Kerr Kirklyn M. , Capen Charles C.
Published: February 2005

The microscopic anatomy of the atrioventricular node, bundle of His, both bundle branches and surrounding fibrous cardiac skeleton was studied in 40 large breed dogs of various ages. In the AV conduction system of all dogs over five years of age there was an increase of fibrous connective tissue, an infiltration of adipose tissue, loss of conduction fibers and focal fibrosis extending from the central fibrous body.

Fibrosis was seen in the summit of the interventricular septum posterior to the AV node in dogs of all ages. Chondroid metaplasia was consistently observed in the central fibrous body and the root of the aorta in large breed dogs, including ten Doberman Pinschers of all ages. This metaplasia varied from a few chondroblasts and chondrocytes to mature chondrocytes with mineralization. Bone formation was seen in eight dogs. These changes appeared in close approximation to the cardiac conduction system above the bundle of His. No degenerative changes were seen in the AV bundle. Approximately one‐half of the large breed dogs five years of age and older had thickened medial and intima proliferation in the small coronary arterioles supplying the AV node. The results of this study suggest that the presence of cartilage and bone in the central fibrous body is a normal occurrence in large breed dogs at all ages.
Failure of induced functional activity and cell deficit to restore preoperative cell number in paired accessory sex glands following unilateral ablation in castrated male mice
Authors: Alison Malcolm R. , McHanwell Stephen , Wright Nicholas A.
Published: February 2005

The proliferative response to testosterone propionate in the accessory sex glands of castrated male Balb/c mice has been studied when the glands were intact, and when the glands were unilaterally ablated. The response was analysed by serial measurements of DNA and weight, and by 3H‐thymidine labelling techniques. When stimulation is started at three days after castration, most seminal vesicle cells of intact glands carry out DNA synthesis to restore preoperative cell number, whilst the smaller reduction in coagulating gland DNA prior to stimulation results in only about 30% of cells carrying out DNA synthesis to restore former levels. In the unilaterally ablated glands of the 3‐day castrates, the cell kinetics of stimulated DNA synthesis and the net accumulation of DNA were similar to the intact glands. A much larger deficit in DNA was apparent in all glands of unstimulated 14‐day castrates, resulting in a much larger net accumulation of DNA following testosterone stimulation. No difference between intact and unilaterally ablated glands was detected, and despite prolonged stimulation DNA levels did not exceed preoperative values. Unlike gland DNA levels, gland weights exceeded those of non‐castrated mice following prolonged stimulation. However, unilateral ablation did not result in further weight increases in the remaining contralateral glands. It is concluded that the absence of the contralateral sex gland is not detected by the remaining partner during the response to the combined stimuli of a reduction in cell number (resulting from androgen deprivation), and testosterone propionate administration.
Morphologic effects of pressure changes on canine carotid artery endothelium as observed by scanning electron microscopy
Authors: Lee Mary M. L. , Chien Shu
Published: February 2005

By using scanning electron microscopy (SEM) we were able to follow the sequence of ultrastructural alterations of the luminal surface which occurred when specimens of canine carotid artery were subjected to controlled transmural pressures. Specimens of carotid artery were removed from dogs following fixation at experimental pressures ranging from 0 mm Hg to 100 mm Hg. The endothelium of specimens fixed at 0 mm Hg has parallel longitudinal ridges formed by the contraction of the underlying internal elastic lamina. With increasing transmural pressure, the luminal surface undergoes a gradual flattening of the endothelial ridges so that at 100 mm Hg, these ridges have completely disappeared. The observed morphologic changes of the arterial endo‐thelium indicate that SEM can provide good ultrastructural information on blood vessels subjected to controlled transmural pressure and that the pressure‐dependent alterations must be considered in studies on vascular structure and function.
The morphology of extrachoroidal ependyma overlying gray and white matter in the rabbit lateral ventricle
Authors: Page Robert B. , Rosenstein Jeffrey M. , Leure‐Dupree Alphonse E.
Published: February 2005

A morphologic investigation of ependyma over gray matter (caudate nucleus) and over periventricular white matter (tapetum) of the rabbit lateral ventricle was undertaken prior to evaluation of morphological changes which occur with experimental hydrocephalus. Ependymal cells over the caudate nucleus are cuboidal and heavily ciliated. Numerous microvilli cover the cell surface. The lateral margins are straight and interdigitations between adjacent ependymal cells are absent. Ependymal cells over white matter are squamous. Nonciliated as well as ciliated cells contribute to the epithelial lining. Microvilli are present at the cell surface but tend to aggregate near the cellular borders. The lateral margins are convoluted and complex interdigitations are present between adjacent cells. Morphologic differences between ependymal cells over the caudate nucleus and those over periventricular white matter may help to explain the differential response to hydrocephalus observed in these two regions of the lateral ventricle.
Alterations in hepatocytes of mice fed a gallstone‐inducing diet: Occurrence of nuclear and cytoplasmic lipids
Authors: Saland L. C. , Napolitano L. M.
Published: February 2005

Mice fed a high cholesterol‐cholic acid (lithogenic) diet for one year develop fatty livers in addition to gallstones. Light and electron micrographs demonstrate large amounts of lipids in liver parenchymal cells, often to the exclusion of most other cytoplasmic organelles. In addition, some hepatocytes exhibit nuclear lipid pseudo‐ and true inclusions. Other prominent features of hepatocytes after lithogenic diet include segregation of nucleolar granular and fibrillar material. Accumulation of considerable collagen in extracellular spaces is also noted. Observations suggest changes induced by the cholesterol diet are comparable to cytologic alterations seen in spontaneous and drug induced hepatic tumors, as well as to more general “fatty metamorphosis” of the liver.
Mandibular growth retardation in corticosteroid‐treated juvenile mice
Authors: Silbermann Michael , Maor Gila
Published: February 2005

Juvenile mice were treated for up to eight weeks with weekly doses of a synthetic analogue of cortisol:triamcinolone hexacetonide. The mandibular condylar cartilage was studied histologically and histochemically at regular intervals. Morphometric measurements were performed along the mandibular posterior vertical dimension (condylar process and ramus). By the second injection significant morphological changes were noted in the condylar cartilage, followed by retardation of bone growth. The most distinctive feature in the cartilage of triamcinolone‐treated mice was a marked increase in the dimension of its mineralized zone concomitant with a significant increase in the number of hypertrophic chondrocytes. The role of condylar cartilage in mandibular growth is discussed.
Intraspinal non‐neuronal cellular responses to peripheral nerve injury
Authors: Gilmore Shirley Ann , Skinner Robert D.
Published: February 2005

The accumulation of non‐vascular, non‐neuronal cells (designated herein as reactive cells) in association with perikarya of axotomized motor neurons has been described by many investigators. Recently Gilmore ('75) found that sciatic axotomy in immature rats resulted in the occurrence of reactive cells not only in the spinal ventral gray matter but also in the dorsal gray matter. To determine if the presence of these cells in the dorsal gray matter, a finding not reported by others, was related to the immaturity of the animal, sciatic axotomy was performed in rats ranging in age from 17 days to 16 months in the present study. Light microscopic evaluation of the spinal cords three or seven days post‐operatively showed that the reactive cells occurred consistently in both dorsal and ventral gray matter irrespective of age. Transection of tibial nerve or the nerve to the medial head of the gastrocnemius muscle elicited a cellular response in both dorsal and ventral gray matter, although transection of the latter nerve resulted in a much less obvious response. Crushing of the sciatic nerve was followed by a response of reactive cells not qualitatively different from that noted following transection. Transection of the sural nerve, primarily a sensory nerve, resulted in the presence of reactive cells in dorsal gray matter but not in the environs of motor neurons in the ventral gray matter. These findings suggest that the reactive cells in the dorsal gray matter of the spinal cord are associated with altered central processes of dorsal root ganglion cells.
Early cytodifferentiation of human prostatic urethra and Leydig cells
Authors: Kellokumpu‐Lehtinen P. , Santti R. , Pelliniemi L. J.
Published: February 2005

The ultrastructure of the urethral epithelium and mesenchyme of the 6‐ to 9‐week‐old human embryos was studied in order to reveal early morphological signs of prostatic development. The morphological changes of the urethral wall were correlated with the cytodifferentiation of the Leydig cells of the same embryos. Throughout the study the urethral epithelium had two or more layers of cuboidal cells. The ultrastructure of the cells was primitive and they did not achieve characteristics of the secretory prostatic cell. The surface cells had well developed apical junctions and slender cytoplasmic processes projecting into widened intercellular spaces appeared during the developmental period. The urethral mesenchyme showed the most salient changes. The mesenchymal cells adjacent to the urethral epithelium differentiated in the ninth week into fibroblast‐like cells with an elongated shape and cytoplasmic processes. Granular endoplasmic reticulum appeared in the cytoplasm and collagen fibers were seen in the intercellular space. Mesenchymal cell processes contacting the continuous basal lamina under the epithelium were present. No direct epithelio‐mesenchymal cellular contacts could be seen. The differentiation of the mesenchyme before the epithelial outgrowths suggests that the mesenchyme has an essential role in the glandular development.

Electron microscopic study of the Leydig cells showed that the amount of agranular endoplasmic reticulum increased considerably in the ninth week. This agrees with earlier biochemical findings on the capability of Leydig cells to produce androgens by this time. The temporal relationship between the cytodifferentiation of Leydig cells and the urethral wall is consistent with the idea that in the human, fetal androgens induce prostatic development.
The topography of rat submandibular gland parenchyma as observed with S.E.M.
Authors: Brocco Steven L. , Tamarin Arnold
Published: February 2005

The parenchymal components of rat submandibular gland were examined by scanning electron microscopy after removal of the stromal connective tissue by acid hydrolysis and/or enzymatic digestion. Secretory acini have polymorphous topographies but usually consist of three to five truncated lobes emanating from a common hilus. They have a mean volume of about 33,000 μm3. Myoepithelial cells are associated with the deeper acini of the gland where they cover ⋍ 54% of the surface area of their allied acini. Each flattened myoepithelial cell has a central perikaryon that gives rise to four or five broad primary processes that bifurcate two or three times to produce a total complement of 20 to 40 terminal processes per cell, each 0.5 μm to 1.7 μm wide. The terminal processes of adjacent myoepithelial cells tend to slightly overlap and to attach to each other by desmosomes forming a network over adjacent acini. The components of the duct system are examined and each characterized by salient features as observed with the SEM.
The occurrence of ciliated and mucous cells in the peripapillary trench of the rat tongue
Authors: Toyoshima Kuniaki , Shimamura Akitatsu
Published: February 2005

Ciliated cells surrounded by mucous cells were found near the base of the peripapillary trench of the rat circumvallate papilla. The ciliated cells occurred singly or in small groups. Each cilium showed the nine plus two filament pattern characteristic of motile cilia.

We consider that these cells function in wetting the taste pores, circulating saliva containingtastants and removal of debris from the papillary trench.
Synthesis of secretory and plasma membrane glycoproteins by striated duct cellsof rat salivary glands as visualized by radioautography after 3H‐fucose injection
Authors: Hand Arthur R.
Published: February 2005

The ability of the striated ducts of rat salivary glands to incorporate 3H‐fucose into glycoprotein was studied by light and electron microscope radioautography. At 3.5 to 20 minutes after intravenous injection, the majority of the radioautographic grains in the ducts of the parotid gland were localized to the Golgi apparatus. By 40 minutes, the percentage of grains over the Golgi apparatus had decreased; a corresponding increase in grains occurred over small (0.1‐0.4 μm) apical granules and the highly infolded basal and lateral plasma membranes. By two hours, less than 10% of the label was associated with the Golgi apparatus, while 26% and 28% were attributed to the apical granules and plasma membrane, respectively. By 8 to 12 hours after injection, the number of grains over the apical cytoplasm had decreased, suggesting luminal discharge of the apical granules. In contrast, the basal and lateral plasma membranes remained labeled up to 30 hours after injection as judged by the distribution of grains in light microscope radioautographs. Mitochondria appeared capable of independent incorporation of fucose, accounting for about 20% of the grains from ten minutes to two hours after injection. Comparable results were obtained in the striated ducts of the submandibular and sublingual glands.

These results indicate that the striated duct cells readily incorporate 3H‐fucose into newly‐synthesized glycoproteins. A portion of these are secretory glycoproteins which are packaged and stored in the apical granules, and a portion are membrane glycoproteins which are incorporated into the extensive plasma membrane of these cells.
Selective labeling of mesenteric lymph nodes: Cell production and emigration ofnewly formed lymphocytes to other organs
Authors: Pabst R. , Trepel F.
Published: February 2005

Lymphocyte production by mesenteric lymph nodes of normal young pigs was studied by intranodal injections of either tritiated thymidine or tritiated deoxycytidine as DNA precursors. One or two days after selective labeling of the mesenteric lymph nodes the relative and absolute number of lymphocytes derived from mesenteric lymph nodes were determined autoradiographically in the following organs: mesenteric, cervical and inguinal lymph nodes, spleen, thymus, bone marrow, peyer'spatches, tonsil, different regions of the gut, lung and liver. The overall cell production of mesenteric lymph nodes, as derived from the sum of all labeled cells one day after labeling, was estimated to be about 7 × 109 lymphocytes. Up to 40% of all newly formed lymphocytes had already left the lymph nodes within one day and were found in all organs studied. There was a preferential homing to the mucosa of the small intestine, but a considerable number migratedto the spleen and even to the thymus and bone marrow. In lymphoid organs all labeled cells were small and medium‐sized lymphocytes one and two days after labeling. In cervical lymph nodes, spleen, tonsil and peyer's patches the relative distribution to T and B cell areas was determined. There was an obvious preference of newly formed lymph node cells to home to T cell areas. The differences of labeling between thymidine or deoxycytidine were surprisingly low.
Development of villus absorptive cells in the human fetal small intestine: A morphological and morphometric study
Authors: Moxey Pamela Colony , Trier Jerry S.
Published: February 2005

We describe the sequential ultrastructural changes in villus absorptive cells of human fetal small intestine between 9 and 22 weeks of gestation. In concert with villus formation at 9 to 10 weeks, a complex membranous system designated the apical tubular system appeared in the apical cytoplasm of absorptive cells. The apical tubular system consisted of deep invaginations of plasma membrane and membrane‐bounded vesicles and tubules. Some elements of this system were characterized by linear arrays of particles on the inner (luminal) membrane leaflet. After villus formation, many lysosomal elements designated “meconium corpuscles” also appeared in the apical cytoplasm. Modified morphometric studies suggested that both the apical tubular system and the lysosomal elements were more extensively developed in the distal than in the proximal intestine, were most abundant at 15 to 17 weeks, and decreased by 18 to 22 weeks. Morphometry also showed an inverse relationship between the relative surface density of the apical tubular system and microvillus membrane, suggesting the possible derivation of elements of the former from the apical plasma membrane. Exposure of intestine to ferritin for 8 to 40 minutes in vitro revealed ferritin in elements of the apical tubular system of 12– to 20‐week fetuses. There was no evidence of transport of ferritin across absorptive cells. Distinctive membranous bodies composed of convoluted membrane‐bound cisternae separated by narrow channels of cytoplasmic matrix were seen in the Golgi region and apical cytoplasm of fetal absorptive cells between 14 and 22 weeks. In a single 22‐week fetus, there was marked proliferation of smooth endoplasmic reticulum, a decrease in cytoplasmic glycogen and loss of most lysosomal and apical tubular elements in the proximal but not the distal intestine. Thus, by the end of the second trimester, the structure of absorptive cells in proximal intestine was remarkably similar to absorptive cells in adult intestine.
Localization of tritiated norepinephrine in the renal arteriolar nerves
Authors: Barajas Luciano , Wang Patricia
Published: February 2005

The innervation of the glomerular arterioles was investigated by light and electron microscopy autoradiography for localization of exogenous tritiated norepinephrine. By light microscopy accumulations of grains were seen associated with afferent arterioles and in lesser numbers with efferent arterioles and neighboring tubules. Accumulations of grains were noted to be in contact with juxtaglomerular granular cells. Electron microscopy autoradiography revealed that nearly two‐thirds of the silver grains were on axons. Most of the label was on varicosities packed with small, clear and dense‐cored, vesicles. Most varicosities, including those in contact with smooth muscle, juxtaglomerular granular or tubular cells, were labeled. Some varicosities which appeared unlabeled in a given section were labeled in subsequent sections. These findings are consistent with the notion that the glomerular arterioles are innervated mainly by adrenergic nerves. This view is supported by the previously reported observations of the concomitant virtual disappearance of fluorescent and acetylcholinesterase‐positive nerves from the region of the glomerular arterioles after two injections of six‐hydroxydopamine (a drug which selectively destroys adrenergic nerves) and the presence of small dense‐cored vesicles in all axons of the juxtaglomerular region when examined by serial section electron microscopy.
Unipolarity of fibroblasts in rodent periodontal ligament
Authors: Beertsen Wouter , Everts Vincent , Brekelmans Margot
Published: February 2005

In order to investigate whether fibroblasts in rodent periodontal ligament have a structural polarity, the position of the Golgi apparatus or the centriolar region in the cells was studied using light and electron microscopy. It appeared that, in the periodontal ligament of continuously erupting mouse and rat incisors, centrioles in fibroblasts on the tooth side of the ligament are preferably located in the anterior (occlusally directed) part of the cytoplasm. Polarity of fibroblasts in a single direction was less pronounced or absent on the bone side of the tissue. In the mouse, fibroblasts in the connective tissue adjacent to the incisor also contained an extensive system of cytoplasmic microtubules, whereas in the fibroblasts on the bone side of the ligament microtubules were less frequent.

Unipolarity of fibroblasts was also observed in the periodontal ligament of the rat maxillary first molar, which is characterized by a limited eruption. Here, the Golgi region was usually situated in that pole of the cells that was directed towards the alveolar wall and the occlusal plane.

It is suggested that structural polarity of fibroblasts in the periodontal ligament of rodent teeth is associated with orientation of functional activities of the cells, such as unidirectional movement or unidirectional deposition or phagocytosis of collagen.