bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence for a relationship between lymphoid cells and osteoclasts: Bone resorption restored in ia (osteopetrotic) rats by lymphocytes, monocytes and macrophages from a normal littermate
Authors: Marks Sandy C. , Schneider Gary B.
Published: February 2005

Osteopetrosis in the ia rat is known to be due to reduced bone resorption and the absence of ruffled borders in osteoclasts. The disease can be cured by the temporary parabiotic union with, or by transfusion of spleen, thymus, or liver cells from, normal littermates. This investigation was pursued in an attempt to determine the cellular basis of this cure by testing the relative effectiveness of populations of mononuclear cells — lymphocytes, monocytes, and tissue macrophages, from spleen and thymus of normal rats — in curing the disease, compared with cell suspensions of the entire organs. The mononuclear fractions were separated from cell suspensions of spleen or thymus by an adaptation of the Ficoll‐Hypaque density‐gradient‐centrifugation procedure. The mononuclear isolates were evaluated by conventional histological procedures and non‐specific esterase histochemistry and found to contain approximately 97% lymphocytes and 3% monocytes from the spleen and 99% lymphocytes and less than 1% monocytes from the thymus.

The results of these transplantations were evaluated radiographically and histologically three weeks after treatment. No difference in the rate of skeletal cure was observed in the ia rats that received cells from either whole spleen or thymus, or the mononuclear isolate from these organs. Osteoclasts from the ia animals cured by the transplantation of the mononuclear isolate were examined by electron microscopy and found to have ruffled borders.

We conclude that the mononuclear cells isolated from either the spleen or thymus of normal littermates have positive effects on osteoclasts and bone resorption in the ia rat, either indirectly, by elaboration of some local factor that affects the mutant osteoclasts, or directly by transformation into osteoclasts.
The neurohypophyseal capillary bed II. Specializations within median eminence
Authors: Page Robert B. , Leure‐Dupree Alphonse E. , Bergland Richard M.
Published: February 2005

Vascular casts of the pituitary gland, median eminence and hypothalamus from several mammalian species were examined by scanning electron microscopy. These observations were correlated with light microscopic studies of injected, cleared median eminence‐pituitary specimens and with light microscopic examination of serial sections of injected hypothalamic, median eminence, and pituitary specimens employing reflected lighting or epiillumination. Transmission electron microscopy was employed to study long portal vessels on the ventral surface of the rat median eminence.

In each of the species examined, the median eminence (infundibular) capillary bed is subdivided into an external and an internal plexus. The external plexus (the neurohemal contact zone) receives an arterial supply from the superior hypophyseal arteries and is continuous with the capillary bed of the infundibular stem and process.

Egress from the external plexus is possible via three vascular routes: (a) by fenestrated portal vessels and capillaries to the adenohypophysis, (b) by capillary connections to the medial basilar hypothalamus and, (c) by internal plexus capillaries to the ependyma of the median eminence.

Median eminence vasculature is structurally organized to deliver (1) hypothalamic and neurohypophyseal peptides to the glandular pituitary via portal vessels, (2) hypothalamic and pituitary secretions to the medial basilar hypothalamus via capillaries, and (3) hypothalamic and pituitary secretions to distant brain sites through cerebrospinal fluid via ventricular and subarachnoid routes.
Investigations on the turnover of adrenocortical mitochondria. X. A correlated biochemical and stereological study of the effects of Chronic treatment with chloramphenicol on the mitochondria of the rat zona fasciculata
Authors: Mazzocchi Giuseppina , Neri Giuliano , Robba Claudia , Belloni Anna S. , Nussdorfer Gastone G.
Published: February 2005

The effects of chloramphenicol (CAP) on rat adrenocortical cells were investigated by biochemical and stereological methods. It was found that administering 50 mg/kg of CAP every 12 hours provoked a persistent inhibition of the incorporation of 3H‐leucine into mitochondrial proteins. Chronic treatment (up to 15 consecutive days) with this dose of CAP induced a significant decrease in the volume of the mitochondrial compartment, in the surface area of the outer and inner mitochondrial membranes and in the number of mitochondria per cell. These results confirm the hypothesis that the ACTH‐induced maintenance of adrenocortical mitochondrial growth requires continuous mitochondrial DNA‐dependent protein synthesis.
The basilar membrane of the bat, Pteronotus p. parnellii
Authors: Henson Miriam M.
Published: February 2005

The basilar membrane of Pteronotus p. parnellii was studied by light and scanning electron microscopy in order to examine the relationship of membrane structure to the sharply tuned sense of hearing in this bat. The basilar membrane was found to differ from those of other mammals and other bats by showing virtually no change in width except at the extreme ends. Thickenings of the pars pectinata and pars tecta are well developed in Pteronotus; they show no sudden changes in their dimensions and in this way differ from the thickenings found in the European horseshoe bat whose sharply tuned sense of hearing seems at least partially dependent on sudden, marked changes in the structure of the basilar membrane. In Pteronotus the greater part of the basilar membrane, 7.5 mm or approximately 58%, lies within the enormous basal turn and within this turn there are steeply banked curves and one small 0.5‐mm region where the membrane is straight. The straight portion is associated with a region of the cochlea where there is a marked change in the density of nerve fibers and where the stria vascularis, spiral ligament and fluid‐filled spaces of the ear are enlarged.
Descending monoaminergic pathways in the primate spinal cord
Authors: Crutcher Keith A. , Bingham W. G.
Published: February 2005

The distribution of monoamine axons and terminals within the spinal cord of a primate (Macaca mulatta) was studied with the Falck‐Hillarp histofluorescence technique for the demonstration of biogenic amines. Catecholamine and indoleamine varicosities appeared qualitatively similar to those previously reported for the rat although the indoleamine terminals were difficult to visualize and were not studied in great detail. Catecholamine fibers innervate the substantia gelatinosa, marginal layer, intermediolateral cell column, ventral horn and the region surrounding the central canal. The location of monoamine axons, as revealed by spinal cord ligation, corresponds to that in the rat and cat with the exception of the dorsolateral region of white matter where fluorescent axons are not visible in the primate.
C‐type virus‐lymphocyte interactions in developing mouse thymus
Authors: Koppenheffer Thomas L. , Phillips Joseph H. , Vankin G. Lawrence
Published: February 2005

The appearance of C‐type virus particles in thymus cells of Swiss mouse embryos, 11.5 to 15.5 days post‐conception age (PCA), was studied with the electron microscope. In thymic rudiments of all specimens examined, virus particles were seen in epithelial cytoplasm, budding from epithelial cell surfaces and in extracellular spaces. Lymphoid cells were first seen in thymic rudiments of 13.5 days PCA, and did not display virus particles at this stage. At 14.5 days PCA, thymic lymphocytes had localized plasmalemmal thickenings of high electron‐density which were adjacent to extracellular virus particles. Viruses appeared to be penetrating thymic lymphocytes by viropexis in embryos of 15.5 days PCA. At this stage, many lymphocytes also had cytoplasmic virus‐containing vesicles and viral buds at their surfaces. These observations suggest the possibility that, in embryos, C‐type I viruses are transmitted horizontally from thymic epithelium to early populations of thymic lymphocytes.
Cytology and distribution of secretory cell types in the mouse hypophysis as demonstrated with immunocytochemistry
Authors: Baker Burton L. , Gross Douglas S.
Published: February 2005

Since differential chemical staining has been unsatisfactory for demonstration of specific secretory cell types in the hypophyseal pars distalis of the mouse, the objective of this study was to determine whether the peroxidase‐antiperoxidase immunocytochemical procedure might be more effective. Accordingly, representative sections from the hypophyses of 17 female and 15 male adult mice of the Swiss‐Webster strain were immunostained, 16 antisera to 5 pituitary hormones or their subunits being utilized. Five secretory cell types were demonstrated. Somatotropes were ovoid to spheroidal and distributed quite generally in the gland except for the “sex zone” where they were scarce. Somatotropes were larger and more numerous in the male than in the female. Mammotropes were polyhedral and also generally distributed in the gland except for the “sex zone” where few were observed. Mammotropes were larger and more numerous in the female than in the male. Corticotropes were small, stellate and few. They were most common near the ventral surface of the gland and formed bilateral centromedial groups in the lateral wings. Thyrotropes were usually large and polyhedral. They were restricted almost solely to the ventral region of the pars distalis. Gonadotropes were polyhedral, and generally distributed, except for aggregation in the cephalomedian “sex zone.” Most gonadotropes appeared to contain both luteinizing hormone and follicle‐stimulating hormone. Thus, all secretory cell types recognized in other species can be demonstrated readily in the mouse hypophysis with immunocytochemistry.
Ultrastructural identification of afferent fibers of cardiac origin in thoracic sympathetic nerves in the dog
Authors: Seagard Jeanne L. , Pederson Harlan J. , Kostreva David R. , Van Horn Diane L. , Cusick Joseph F. , Kampine John P.
Published: February 2005

While cardiac afferent nerve activity has been recorded from the ventrolateral (VLCN) and ventromedial (VMCN) cardiac nerves, left dorsal and ventral ansae subclaviae, and left upper thoracic white rami communicantes, little anatomical evidence for the existence of afferent fibers in these nerves has been reported. This study was designed to characterize the normal ultrastructure of the above nerves and to identify afferent fibers in them through Wallerian degeneration produced by dorsal root ganglionectomy. Laminectomies followed by dorsal root ganglionectomies were performed on left thoracic roots T1‐T4 in six mongrel dogs. The nerves to be examined were removed from two animals at 1, 2, and 3 weeks following ganglionectomy and prepared for electron microscopy. Control nerves were obtained from two normal dogs. Degenerating nonmyelinated fibers were characterized by watery axoplasm containing clumps of electron‐dense material. Degenerating myelinated fibers were distinguished by the separation of their myelin lamellae, producing characteristic whorls. After three weeks, afferent nonmyelinated axons had degenerated in all nerves, leaving only layered processes of Schwann cells in these areas. Approximately 5–15% of the fibers in each nerve degenerated, indicating their afferent nature. Of these fibers, 85–90% were nonmyelinated C fibers and the remainder myelinated Aδ fibers. These results indicate participation of both Aδ fibers and a large population of C fibers in transmission of cardiac afferent activity.
Structure of the chicken's inner ear: SEM and TEM study
Authors: Tanaka Katsuhiko , Smith Catherine A.
Published: February 2005

The inner ears of 35 adult chickens were studied by TEM, SEM and light microscopy. Two well differentiated hair cell/nerve ending units were present: tall hair cells with small vesiculated nerve endings were located on the attached part of the basilar membrane; short hair cells with large vesiculated nerve endings were located on the free basilar membrane except for the distal tip. In this respect the chicken ear is similar to that of the pigeon. The chickens examined did have some unique features. Sensory cells of lenticular and hemispheric shape were also present at the proximal end. Bundles of long dense tubules were seen frequently within the sensory cell cytoplasm. Kinocilia were absent from the hair bundles of many of the sensory cells. The internal structure of the kinocilia which were present was atypical and consisted of a variable number of doublets. Eight peripheral plus one central doublet were found most frequently.
The fine structure of the ventricular surface of the area postrema of the cat, with particular reference to supraependymal structures
Authors: Leslie R. A. , Gwyn D. G. , Morrison C. M.
Published: February 2005

The ependymal surface of the feline area postrema (AP) has been examined with the scanning and transmission electron microscopes. Particular attention was paid to the distribution and structure of supraependymal (SE) cells which have not been described before on this organ. A population of SE cells was found consistently on the cat AP; they were grouped most frequently toward the caudal aspect of the organ. Their structure bears a great resemblance to that of macrophages, containing: (1) many small apical vacuoles, (2) numerous lysosomes, and (3) phagosome‐like bodies. Arrays of microvillous tufts and also singly‐occurring microvilli are features of the unciliated ependymal surface of the organ. Tufts are often found in very close proximity to superficial blood vessels which are characteristically surrounded by large perivascular spaces.
The cochlear nuclei in man
Authors: Moore Jean Kavanagh , Osen Kirsten Kjelsberg
Published: February 2005

The human cochlear nuclei are composed of a ventral and a dorsal nucleus which are similar, though not identical, in their cytoarchitecture to those of other mammals. The ventral cochlear nucleus (VCN) consists of a rostral area of spherical cells, a central area of multipolar and globular cells, a posterior area of octopus cells, and a laterodorsal cap of small neurons. The interareal boundaries are less distinct in man than in the cat. The central region of multipolar cells and the cap area of small cells constitute the bulk of the human VCN. The spherical, globular, and octopus cells appear relatively less numerous in man than in other mammals. The dorsal cochlear nucleus (DCN) in man is relatively large, but lacks the typical stratification seen in other mammals, with only vestiges of the granular and molecular layers remaining. Virtually the entire DCN consists of an area of cochlear fiber neuropil containing pyramidal cells, small neurons, and occasional giant cells. The pyramidal cells have lost their typical radial orientation and lie scattered within the cochlear neuropil. Thus the entire human DCN may be equivalent to layers 2 and 3 of this nucleus in other mammals. In spite of the relatively large DCN, the acoustic striae appear small. This is in contrast to the large trapezoid body leaving the VCN. Intrinsic and descending fiber pathways to the cochlear nuclei are not clearly defined and may be less prominent in man than in the cat.
Morphogenesis of the truncus arteriosus of the chick embryo heart: The formation and migration of mesenchymal tissue
Authors: Thompson Robert P. , Fitzharris Timothy P.
Published: February 2005

The appearance and migration of mesenchymal cushion tissue within the truncus arteriosus of the normal 2.5‐to 6‐day chick embryo heart was surveyed systematically with the light microscope. Series of cross‐sections taken from replicate hearts at successive developmental stages allowed comparison of the following qualitative and quantitative aspects of early truncal morphogenesis. Mesenchyme within the truncus was derived from two distinct sources. The first mesenchyme appeared to migrate caudally into the cardiac jelly of the distal truncus from the nearby aortic arch region, coincident with slowing of the anterior elongation of the heart tube (Hamburger‐Hamilton Stage 17–18). A second, separate mesenchymal population, derived from endocardium, began to fill the conus and proximal truncus in a radial direction, coincident with expansion of the bulbus cordis (Stage 12–19). The measured kinetics of relative cell numbers, distributions, and mitotic indices suggest substantial contributions from both sources. By Stage 26, the conotruncal region was filled with mesenchyme, which then condensed to form the anlagen of three future structures: the semilunar valves, the aorticopulmonary septum, and the tunica media of the great arteries.
Morphogenesis of the fetal membranes of an American mole, Scalopus aquaticus
Authors: Prasad M. R. N. , Mossman H. W. , Scott G. L.
Published: February 2005

Scalopus membranes are characterized by: Superficial nidation; antimesometrial orientation of the embryonic disc; amniogenesis by folding; an extensive but transitory choriovitelline placenta; a large yolk sac with late and incomplete inversion; large persistent allantoic vesicle; a very broad, thin, villous, epitheliochorial chorioallantoic placenta of annular shape interrupted mesometrially, dotted with numerous areolae, and bordered by a non‐villous sparsely vascular chorioallantoic membrane connected with the persistent bilaminar omphalopleure by a very narrow rim of chorion. There is no decidua. Electron microscopy shows that at 8 mm, CR, (limb bud embryo) the uterine epithelium of the interhemal membrane may be 0.5 μm or less in thickness, but that it shows no signs of degeneration. Trophoblastic microvilli often penetrate the epithelium to within 0.2 μm of its base. At this time there is active secretion by the uterine glands, and cellular hypertrophy and cytolysis of the epithelium at the gland mouths, with active phagocytosis by the areolar cytotrophoblast. The occurrence of absorptive areolae in an insectivore emphasizes the probable primitiveness of this widely distributed placental mechanism. In spite of similarities of the yolk sac to that of rabbits and rodents, the bilaminar omphalopleure produces no invasive trophoblastic giant cells. The definitive membranes of Parascalops breweri and Scapanus latimanus are like those of Scalopus. The placentae of Talpa europaea, Condylura cristata, and Neurotrichus gibbsii are discoid and relatively much smaller, thicker and more complex in internal structure. There is some reason to believe that the fetal membrane systems of moles and shrews (Soricoidea) are more like those of the ancestral mammalian stock than are those of any other recent eutherians.
Loss of thick filaments from fast‐twitch glycolytic muscle fibers of the pigeon pectoralis after chronic administration of dantrolene sodium
Authors: Silverman Harold , Hikida Robert S. , Staron Robert S.
Published: February 2005

Adult pigeons received dantrolene sodium, a skeletal muscle relaxant which blocks the release of calcium during excitation‐contraction coupling, for 12 to 16 weeks. The pectoralis muscles of these birds were analyzed for changes occurring in the various fiber types of the muscle. Both histochemistry (ATPase and SDH activity) and electron microscopy (mitochondrial and lipid volume percentages) differentiated two fiber types. The two fiber types consisted of fast‐twitch glycolytic fibers (FG) and fast‐twitch oxidative‐glycolytic (FOG) fibers. After dantrolene treatment some FG fibers showed little or no ATPase activity. Dantrolene treatment also produced a disappearance of thick filaments in some FG fibers. We infer that the fibers without thick filaments are the ones lacking ATPase activity. The FOG fibers were nearly normal. Since drug‐fed birds lose weight, a few birds were starved to determine whether the filament loss was related solely to the bird's loss in weight. No fibers in starved birds showed reduced ATPase activity or loss of thick filaments. In fibers that showed thick filament disappearance, the I‐bands remained organized and intact, suggesting that the I‐band maintains its integrity without interaction with the thick filaments. Changes in activity patterns may cause loss of thick filaments by inhibiting either their synthesis or assembly.
The habenular nuclei of the elasmobranch “Scyllium stellare”: Myelinated perikarya
Authors: Kemali Milena , Miralto Antonio
Published: February 2005

Some habenular cells of the elasmobranch, Scyllium stellare, have a perikaryon completely enveloped by myelin of the compact type. They are found only in the left habenula and not in the right. The myelin sheath accompanies the proximal segment of the process arising from the perikaryon, in a node of Ranvier‐like pattern. The identity of these myelinated cells and the functional significance of their myelination are unknown.
The prism pattern of rat molar enamel: A scanning electron microscope study
Authors: Risnes Steinar
Published: February 2005

Rat molar enamel has been studied by sectioning the enamel along various planes, and observing the etched surfaces in the SEM. It was found that the prism pattern was much more variable than in rat incisor enamel. Regions without prism decussation seemed to dominate in the occlusal half of the molars. Where present, prism decussation was of the uniserial lamellar type, but it varied considerably in distribution, extent, and distinctness. Prism decussation seemed to have a predilection for the cervical enamel, and was almost absent in the enamel on the occlusal surface.

The interprismatic substance showed a characteristic configuration: In the inner enamel it appeared in the form of radially oriented sheets, which tended to delimit radially directed, single lines of prisms. In regions with prism decussation these single lines of prisms encompassed prisms belonging to different prism lamellae. In the outer part of the enamel the interprismatic substance exhibited a honeycomb appearance.

The similarities and differences between the prism patterns of rat incisor and molar enamel may be of importance for understanding the mechanisms of amelogenesis, especially for the recognition of factors controlling the movement of ameloblasts.
Observations on the inter‐relationships of Sertoli cells at the level of the blood‐testis barrier: Evidence for formation and resorption of Sertoli‐Sertoli tubulobulbar complexes during the spermatogenic cycle of the rat
Authors: Russell Lonnie D.
Published: February 2005

Structures termed tubulobulbar complexes are known to be formed by adjoining Sertoli cells at the level of the blood‐testis barrier (Russell and Clermont, 1976). Here, long (2–4 μm) tubular evaginations of one Sertoli cell, which end in bulbous dilations, are seen in corresponding invaginations of a neighboring Sertoli cell. In most regions of the tubular and bulbous portions of the complex, the Sertoli plasma membranes were found to be separated by a 4–5‐nm intercellular space, but in some areas the membranes converged to form tight and gap junctions. The numbers, distribution and properties of tubulobulbar complexes were studied in relation to the cycle of the seminiferous epithelium. From the data obtained it was concluded that tubulobulbar complexes develop and undergo regressive changes during the spermatogenic cycle. Most complexes arise during the early stages of the cycle (Stages II‐V) and develop large bulbous endings. Developing tubulobulbar complexes consist of short evaginations of one Sertoli cell which face a bristle‐coated pit of the opposing Sertoli cell. At midcycle (Stages VI‐VII) most show regressive changes and are eventually resorbed as a consequence of the action of nearby Sertoli lysosomes. Once resorbed, the probability of seeing a tubulobulbar complex in thin sections decreases from 4‐ to 8‐fold. The few tubulobulbar complexes which remain past this period (Stages VII‐XIV‐I) usually lack bulbous endings and are frequently seen above type A spermatogonia. The data suggest that small fragments of cytoplasm and plasma membrane (including junctional surfaces) are lost from one Sertoli cell as a result of the degradative processes occurring in a neighboring Sertoli cell. Tubulobulbar resorption is discussed in relation to the impending breakdown of the blood‐testis barrier above spermatocytes as these cells move upward. The possible significance of the cyclic resorption of tight and gap junctional sites between Sertoli cells is also discussed.
Density variation in the humeral cortex of Macaca
Authors: Burr David B.
Published: February 2005

The purpose of this research was to describe patterns of density variation throughout the cortex of the humeral shaft in Macaca and to attempt to explain these variations in terms of the gross anatomy and mechanical function of the bone. One hundred ninety transverse sections were taken from five sites along the humeral diaphyses of 38 Macaca. The density at eight positions around each section was measured using radiographic and densitometric techniques. Analysis of variance indicated significant (p < 0.02) differences among cross‐sectional levels and positions within each level. No sexual dimorphism in density could be demonstrated, although sexual dimorphism in density has been reported for the femora of this same sample. This relationship between humerus and femur parallels that found in humans. Density increased distally in the humerus, probably due to major areas of muscle attachment. Comparison with similar data from the femur of Macaca indicated unexpected differences in density pattern which may underlie differences in the strength and mechanics of the upper and lower extremities.
A route for direct retinal input to the preoptic hypothalamus: Dendritic projections into the optic chiasm
Authors: Silver Jerry , Brand Scott
Published: February 2005

With the use of Golgi, horseradish peroxidase, and electron microscopic techniques, neurons within a broad region of the preoptic hypothalamus of the mouse were shown to have dendrites that projected well into the depths of the optic chiasm. Further experimental and ultrastructural investigation demonstrated synapses between these dendrites and retinal axonal boutons within the chiasm. All synapses located in the chiasm were classified as Gray's type I. The possible function of these dendritic projections is discussed.
Cephalic neurulation and optic vesicle formation in the early mouse embryo
Authors: Kaufman Matthew
Published: February 2005

The overall pattern of cephalic neurulation and the concomitant early development of the optic vesicles in mouse embryos were examined by scanning electron microscopy. Paraffin‐sectioned specimens were also examined.

The overall pattern of closure of the cephalic neural folds accords well with earlier observations of this process. The earliest indication of optic placode formation was seen in histological sections of embryos at the 4‐ysomite stage, while optic pit formation was first observed at the 5‐ to 6‐somite stage. The upper halves of the optic vesicles were formed in 10‐ to 15‐hsomite embryos by the fusion of the neural folds at the junction between the mesencephalon and prosencephalon, while closure of the lower halves was associated with the closure of the rostral neuropore, and was usually completed by about the 20‐somite stage.

By the 25‐ to 30‐somite stage, a rapid increase in the volume of the forebrain was observed, so that the optic vesicles were displaced laterally. An overall increase in the volume of the optic vesicles and decrease in the diameter of the optic stalks were also observed at this time. This account of cephalic neurulation and optic organogenesis provides useful baseline data relevant to the study of the normal early development of the mouse. A comparison is made between similar events in the rat, the hamster, and the human embryo.
Mode of action of cortisol on bone resorption in fetal rat fibulae cultured in vitro
Authors: Liskova‐Kiar Marie
Published: February 2005

Several concentrations of cortisol (10‐8 to 10‐6 M) were tested for their ability to inhibit the spontaneous or parathyroid extract‐induced (PTE) bone resorption in organ cultures of 19‐day‐old fetal rat fibulae. The criteria used for the assessment of bone resorption were: the release of 45Ca from pre‐labeled bone rudiments into the culture medium, the dry weight and the number of osteoclasts per bone. At a dose of 10‐6 M, cortisol diminished significantly the release of 45Ca from fetal fibulae. This inhibition was accompanied by an increase in bone dry weight and by reduced numbers of osteoclasts. PTE, alone, caused extensive bone resorption with numerous osteoclasts and enhanced 45Ca release, without weight gain. This resorptive action of PTE was partially suppressed by cortisol at a dose of 10‐6 M. Lower concentrations were ineffective. Radioautographic studies with 3H‐thymidine revealed that cortisol restricts the recruitment of osteoclasts from osteoprogenitor cells, without decreasing the potential of precursor cells to form osteoblasts. PTE, however, stimulates the proliferation of progenitor cells and favors their differentiation towards osteoclasts. This effect can be suppressed by cortisol. It is concluded that cortisol inhibits bone resorption in vitro by limiting the ability of precursor cells to form osteoclasts. Moreover, our study shows that, in fetal rat bones cultured in vitro, osteoclasts arise from locally proliferating mononucleated precursor cells.
Establishment of an epithelial cell line from rat thymus
Authors: Itoh Tsunetoshi
Published: February 2005

A cell line (IT‐26R21), composed only of epithelial cells, was established from normal rat thymus. Thymuses were treated with both collagenase and trypsin. Four months after the initiation of cultures, epithelial cells in packed colonies formed a monolayer and no other cells were found in cultures. Thereafter, epithelial cells have been subcultured with trypsin and EDTA, and are currently at the 30th subculture.

Based upon the fine structure of the thymus in vivo, IT‐26R21 cells were identified as epithelial cells from the thymus, because of their mosaic‐like arrangement, desmosomes and tonofilaments. Other features also supported their origin and identity.
Binding of concanavalin‐A to critical‐point‐dried and freeze‐dried human lymphocytes
Authors: Schneider Gary B. , Pockwinse Shirwin M. , Billings‐Gagliardi Susan
Published: February 2005

When human lymphocytes are treated with concanavalin‐A (con A) and hemocyanin, the hemocyanin marker, which demonstrates con A binding sites, can be visualized by scanning (SEM) and transmission electron microscopy (TEM) on both critical‐point‐dried and freeze‐dried cells. The ability to visualize the hemocyanin marker by SEM, its quantity and distribution, were all similar in lymphocytes prepared by both drying procedures. By TEM, hemocyanin was seen adjacent to the plasma membrane on critical‐point‐dried lymphocytes. In contrast, freeze‐dried cells showed hemocyanin labeling at some distance from the plasma membrane (40–70 nm) as well as adjacent to it. The distribution of hemocyanin corresponded to the thickness of the amorphous coat seen on fixed, freeze‐dried cells. Therefore, the extracellular coat on freeze‐dried lymphocytes is a carbohydrate‐containing glycocalyx.
The regenerating liver: A site of erythropoiesis in the adult long‐evans rat
Authors: Naughton Brian A. , Kolks Gail A. , Arce Janet M. , Liu Philip , Gamba‐Vitalo Christina , Piliero Sam. J. , Gordon Albert S.
Published: February 2005

Erythropoiesis, which is primarily hepatic in the rat during fetal and early neonatal life, shifts almost entirely to the bone marrow in the neonatal‐adolescent stage of development. In the adult, extramedullary erythropoiesis has been demonstrated in the liver and spleen under certain pathological conditions when bone marrow red cell production is insufficient. In the present study, erythropoietic foci have been found in young‐adult rat liver regenerating 24–72 hr after subtotal hepatectomy. This erythropoiesis is both extravascular and sinusoidal, with some erythroblastic islands noted. The centrolobular hepatic area contains the highest concentration of erythroblasts. Peripheral blood reticulocytosis coincides with the appearance of these cells and this is considered as an indicator of effective erythropoiesis. Liver regenerating after partial hepatectomy produces significant quantities of erythropoietin (Ep) in response to hypoxia. Subtotal hepatectomy may confer upon the adult liver the ability to revert to a fetal‐like condition both in its ability to produce Ep and to function as a hematopoietic inductive microenvironment for erythropoiesis.
Increase in free cholesterol content of the adrenal cortex after stress: Radioautographic and biochemical study
Authors: Sharawy Mohamed , Dirksen Thomas , Chaffin Joe
Published: February 2005

The purpose of this investigation was to quantify free cholesterol biochemically and in radioautographs of 3H‐digitonin cholesterol complex in fasciculata cells of control and stressed rat adrenal cortex. Stress was induced by ether, laparotomy, and adrenal and intestinal handling. Control rats were anesthetized with nembutal. All animals were killed ten minutes from the beginning of anesthesia. The adrenals were excised and either fixed in glutaraldehyde containing 3H‐digitonin or homogenized for biochemical determination of free cholesterol. The plasma corticosterone level of each animal was measured. The fixed adrenals were processed, using different methods of dehydration and embedment, for light and electron microscopic radioautography. The mean number of silver grains (X̄) per unit area of zona fasciculata was counted from light microscopic radioautographs. Crystals of cholesterol‐digitonide complex were more numerous in stressed fasciculata cells, particularly over SER. Silver grains were localized over or close to the crystals. The X̄ for stressed rats was significantly higher than control values, indicating more free cholesterol in fasciculata cells of stressed rats. The results were not affected by either the method of dehydration or the type of embedding medium used. The morphologic results were substantiated by biochemical findings of increase in free cholesterol in adrenals of stressed rats. Plasma corticosterone was significantly high in stressed rats. The increase in free cholesterol in stimulated fasciculata cells is consistent with a previously reported increase in cholesterol esterase activity after ACTH stimulation.
Intracellular dynamics in pituitary mammotropes throughout the rat estrous cycle. II. Changes in synthetic and secretory organelles
Authors: Poole Max C. , Mahesh Virendra B. , Costoff Allen
Published: February 2005

The organellar dynamics within mammotropes (prolactin secreting cells) of the anterior pituitary were examined using morphometry throughout the four‐day rat estrous cycle. Two predominant periods of maximal organellar activity were found. The first period, which occurred during proestrus, resulted in two peaks of serum PRL at 6 pm and 12 m proestrus, while the second occurred during middiestrus‐2 and resulted in an increase of pituitary PRL, but not a major serum PRL peak. The mitochondrial volume rose prior to that of other organelles during early proestrus, rising 110% from 4 am late diestrus‐2 to 6 pm proestrus. However, the number of mitochondria per cell remained constant throughout the cycle. The volumes of rough endoplasmic reticulum (RER) and Golgi complex reached maximal proportions at 8 pm and 12 m proestrus, respectively. The RER volume was 153% greater than at 4 am late diestrus‐2, while the Golgi complex had increased by 200%. We suggest that changes in the RER and Golgi complex volumes were the result of two processes: the synthesis of new membrane and the swelling of existing complexes. This study further substantiated that the serum peak of PRL at 6 pm proestrus is the result of stored mature granules being released, whereas the PRL peak at 12 m proestrus is due to the immediate release of hormone without any storage.
Somitogenesis in cultured embryos of the Japanese quail, Coturnix coturnix japonica
Authors: Packard David S.
Published: February 2005

The ability of unsegmented paraxial mesoderm from Japanese quail embryos to form somites was studied by culturing pieces of embryos, containing the segmental plates, on an agar medium. In the first experiments, two explants were prepared from each donor embryo. Both explants contained a segmental plate and neural tube, but only one contained notochord. The explants containing notochord formed 11.4 ± 2.1 somites, while the explants without notochord formed 11.1 ± 1.3 somites. It was concluded that explants containing Japanese quail segmental plates readily form somites in culture and that the continued presence of the notochord is not required for these somites to form. In a second series of experiments, one explant from each donor embryo contained neural tube and notochord along with the segmental plate, while the corresponding explant did not contain axial structures. The results, which were similar to those obtained in the first experiments, indicated that neither neural tube nor notochord is required for somitogenesis in vitro. Additional experiments demonstrated that bilateral symmetry extends to the unsegmented somite mesoderm, where there was a strong tendency for each segmental plate of a given embryo to form the same number of somites. It was also shown that over a three‐fold range of segmental plate length, there was only a slight tendency for shorter segmental plates to make fewer somites. It was estimated that Japanese quail embryos having five to 21 pairs of somites have segmental plates that represent 11.3 ± 2.9 prospective somites each.
The development of the sinusoids of fetal rat liver: Morphology of endothelial cells, Kupffer cells, and the transmural migration of blood cells into the sinusoids
Authors: Bankston Patrick W. , Pino Richard M.
Published: February 2005

The fine structural development of rat fetal liver sinusoids from 10 to 22 days gestation was studied. Colloidal carbon (Pelikan ink) was injected into 14‐22 day gestation fetuses via the umbilical vein to assess the continuity of the sinusoidal lining and the phagocytic ability of the developing lining cells. Endothelial cells, devoid of an underlying basal lamina, form the bulk of the vascular lining at all gestational ages. These cells possess typical intercellular junctions and fenestrae with diaphragms before 17 days gestation. Transendothelial open fenestrations, typical of the adult liver, appear around 17 days gestation, increasing in number for the remainder of gestation. Although fenestrae possessing diaphragms are permeable to carbon before 16 days gestation, open fenestrations, first seen at 17 days gestation, allowed large amounts of carbon to reach the extravascular space. Endocytosis of carbon by endothelial cells was accomplished exclusively by large bristle‐coated vesicles. Endothelial cells were also seen to be involved in transmural diapedesis of newly formed erythrocytes and megakaryocyte processes from the extravascular space by forming a temporary migration pore allowing these cells and processes to enter the circulation. At the end of gestation, blood‐forming activity had nearly ceased, and only the space of Dissé separated the lining cells from the parenchymal cells. Kupffer cells were easily identified as early as 13 days gestation by their content of phagosomes and engulfed erythrocytes. The Kupffer cells are much more avid in the phagocytosis of carbon than are endothelial cells. Toward the end of gestation, some Kupffer cells develop a homogeneous “sticky coat” to carbon.
The stem‐cell zone of the small intestinal epithelium. IV. Effects of resecting 30% of the small intestine
Authors: Bjerknes Matthew , Cheng Hazel
Published: February 2005

In the mouse jejunum, as in the rat, a new steady state was established 3 weeks after resection of 30% of the small intestine. The mean height of a villus, crypt, and proliferative zone increased. We studied the effects of this new steady state on the distribution of the four main epithelial cell types and on the stem‐cell zone. Beginning 2 cm distal to the ligament of Treitz, 10 cm of jejunum were resected. In control animals the jejunum was transected 12 cm distal to the ligament of Treitz and then rejoined. The mice were killed 1 and 3 weeks after surgery and a piece of jejunum 4 cm distal to the anastomosis collected. One hour before death the animals were given an injection of 1 μCi/gm 3H‐thymidine. The tissue was embedded in Epon and then serial 1 μm sections were prepared and radioautographed. One week after resection there was a transient increase in the proportion of enteroendocrine cells in the crypts. This returned to control levels 3 weeks after resection. Thus, there appeared to be a feedback from the enteroendocrine population onto enteroendocrine cell production. After resection, amplification of mucous cell numbers by mucous cell division was reduced and yet normal proportions of mucous cells were observed in the epithelium. Therefore, an increased proportion of stem‐cell output must have been committed to the mucous and enteroendocrine cell lines. The increased height of the proliferative zone that followed 30% resection was not due to an increase in the number of transit divisions through the proliferative zone. Instead it was due to an increased output from the stem‐cell zone into the proliferative zone. Evidence was presented which indicates that the increased output from the stem‐cell zone was due to an increased number of stem cells in the zone, at the expense of non‐stem cells. The height of the stem‐cell zone, as indicated by the Paneth cell distribution, the mucous cell distribution, and the distribution of labeled mucous cells, did not change after 30% resection.
Distribution and structure of the adrenocortical homologue in the garpike
Authors: Bhattacharyya Tapan K. , Butler David G. , Youson John H.
Published: February 2005

The microanatomy of the yellow corpuscles (adrenocortical homologue, AH) in the holostean fish, Lepisosteus spp., was studied by serial sectioning, steroid histochemistry, and electron microscopy. The modification of this tissue to short‐term ACTH treatment was also observed. The distribution of the AH within the renal tissue of the garpike phylogenetically represents a more advanced condition than that seen in its closest holostean relative, the bowfin, and appears to approximate that in teleosts. The homology of this tissue to vertebrate adrenocortical tissue was established by the positive identification of the enzyme, Δ5‐3β‐hydroxysteroid dehydrogenase, and by the ultrastructural features of the cells before and after ACTH administration.

The AH cells possess fine structural features characteristic of steroidogenic cells, namely, polymorphic mitochondria with tubular cristae, abundant tubules of smooth endoplasmic reticulum, a prominent Golgi complex, and lipid droplets. Other interesting features include the presence of annulate lamellae and a variety of dense bodies. Digitonin perfusion results in the deposition of presumed, cholesterol‐digitonide crystalline spicules on the surface microplicae of the cells and as dense accumulations in association with smooth endoplasmic reticulum. ACTH administration results in swelling of mitochondria, a loss of their cristae, and a decrease in electron density of their matrices. Alterations also occur in the smooth and rough endoplasmic reticulum, and large osmiophilic inclusions of irregular profile appear. Some of the ACTH‐induced modifications are similar to those observed in the adrenocortical cells of other vertebrate groups following comparable stimulation.
Tenotomy of the avian anterior latissimus dorsi muscle. I. Effect of age on fiber‐type transformation and regeneration from the stump in chicks
Authors: Hikida Robert S. , Wang Roomfang June
Published: February 2005

The chick's anterior latissimus dorsi muscle (ALD) was tenotomized at its origin at either 1 day or 4 weeks of age, and investigated histochemically and ultrastructurally at intervals thereafter to determine whether muscle fiber‐type transformation from a slow to a twitch type is greater in young birds than older birds. No transformation of fiber type occurred in either procedure, but a new muscular connection regenerated between the scar tissue at the end of the original tenotomized stump and the former origin. This regenerated muscle had a mosaic pattern of fiber types, as demonstrated by myofibrillar ATPase activity, and contained predominantly fast fibers, as contrasted with controls or the tenotomized portion, which contained predominantly slow tonic muscle fibers. The regenerated portion contained muscle spindles. The original portion of the tenotomized muscle was indistinguishable from the control muscle. These responses of the chick ALD to tenotomy are quite different from those in the pigeon, which are reported in the following study.
Freeze‐fracture study of rat ventral prostate: The columnar epithelial cell
Authors: Kachar Bechara , da Silva Pedro Pinto
Published: February 2005

The organization of the secretory epithelium of the rat ventral prostate as seen by freeze‐fracture is analyzed. Ultrastructural interpretation of the tall columnar epithelial cell is facilitated by the axial regionalization of the cytoplasm. The endoplasmic reticulum, which exists in all the regions of the cell, appears to have a role in the maintenance of cellular organization. Its cisternae delimit the spaces for the nucleus, the Golgi, and the apical secretory apparatus. Elements involved in the formation of secretory products for export are located within the apical region of the cell and are regionally separated from the Golgi complex. Structural and functional specializations of the plasma membrane in the apical, lateral, and basal areas are illustrated. Artifacts related to specimen preparation procedures are reported. Displacement of membrane particles, which we observed in the fracture faces of plasma and intracellular membranes, appears related to fixation at low temperature. Fixation at 37°C, which does not induce membrane‐particle displacement, results in proliferation of tight‐junctional elements.