bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrastructure of developing alveoli. I. The role of the interstitial fibroblast
Authors: Vaccaro Charles , Brody Jerome S.
Published: February 2005

We examined the ultrastructural features of postnatal alveolar septal formation in rats from birth to 28 days of age. At birth, the rat lung consists of large saccules with thick walls and cellular interstitium. Interstitial cells have large oval nuclei with scant cytoplasm containing few organelles and scattered lipid droplets. These cells appear to be poorly differentiated mesenchymal cells not engaged in active protein synthesis or secretion. Between 5 and 15 days of age, saccule walls thin and many new alveolar septa form. Two types of interstitial fibroblasts are present: one which appears at the tips of newly formed septa has the characteristics of a myofibroblast and appears to be engaged in synthesis and secretion of elastin; the other fibroblast appears at the base of new septa, is filled with lipid and contains few other cytoplasmic organelles. After 15 days of age, alveolar walls become thinner, few new septa form and interstitial fibroblasts begin to resemble the dormant type of fibroblasts seen at birth. Thus, the process of postnatal alveolarization of lung parenchyma involves differentiation of the interstitial fibroblast and elastogenesis. The factors which control this process, the precise role of elastogenesis in alveolar septal formation, the origin and fate of the lipid filled fibroblast and the ultimate fate of the myofibroblast remain to be determined.
Morphological and quantitative analysis of spermatogonia in mouse testes using whole mounted seminiferous tubules. II. The irradiated testes
Authors: Huckins C. , Oakberg E. F.
Published: February 2005

In adult male mice exposed to 300 R X‐irradiation, the sper‐matogonial population was selectively killed except for the radioresistant type As stem cells. Type A spermatogonia were minimal two days after irradiation, when only 20% of the control population was present in stages 5‐6; these were predominately single and paired undifferentiated cells. When multiple injections of 3HTdR were given between 2 and 3.5 days post‐irradiation, 90–95% of these survivors in stages 4‐6 became labeled. Enhanced proliferation of these stem cells, and at times when they were normally quiescent, led to restoration of all classes of spermatogonia by 11 days after irradiation.

Several autoradiographic studies were undertaken to better characterize the radioresistant cells. In mice given single or multiple injections of 3HTdR prior to irradiation, there was appreciable retention of label by those type As sper‐matogonia that had originally incorporated 3HTdR in stages 2‐4. This labeling pattern was identical to that of the long‐cycling As stem cells in nonirradiated testes. Since the long‐cycling As stem cells are thought to be characterized by a prolonged G1 or “A‐phase” which is known to be a highly radioresistant portion of the cell cycle, it was clear why these cells could preferentially survive irradiation doses that killed other spermatogonial types. It was proposed that following germ cell depletion, as after irradiation injury, the long‐cycling As survivors could be prematurely triggered from A‐phase into DNA synthesis, thereby, initiating restoration of the germ cell population.
Ultrastructural cytochemistry of atrial muscle cells. VI. Comparative study of specific granules in right and left atrium of various animal species
Authors: Cantin Marc , Timm‐Kennedy Martina , El‐Khatib Ellen , Huet Madeleine , Yunge Lawrence
Published: February 2005

Specific (A‐, B‐ and D‐) granules as well as multivesicular bodies (MVB) with a dense core from the right and left atrium of a variety of mammals (mouse, rat, hamster, guinea pig, rabbit, young and old cat) were compared by quantitative ultrastructural and cytochemical methods as regards number, size, localization and reactivity. The number of specific granules was greater in the right atrium of the rat and lesser in the same atrium of the guinea pig. In the rat this difference was due to a greater number of all three types of specific granules in the right atrium. In the guinea pig, both A and B granules were more numerous in the left atrium. A greater number of granules was also found in the left atrium of hamster, rabbit and young and old cat but the difference with the right atrium was not significant. All atria contained the same type of specific granules but A‐ and B‐granules were present in the left atrium not only in the paranuclear area, as in the right atrium, but also throughout the sarcoplasm. In both atria, all specific granules were argen‐taphobic when stained according to the periodic acid‐thiocarbohydrazide‐silver proteinate technique of Thiery. They reacted positively to phosphotungstic acid‐hydrochloric acid (PTA) (pH 0.3) as did the cell coat, residual bodies (Cgranules), lysosomes, Z‐disks and a small portion of the Golgi complex. The PTA and PAS stains were abolished by acetylation, restored by saponification, unchanged by methylation and greatly diminished by sulfation. The MVB with a dense core, identical to those already noted in the cells of various endocrine glands, and thought to be crinophagic, were rare in the right atrium of all species and absent in that of the rat. They were much more numerous in the left atrium, particularly of hamsters, guinea pigs and cats and, to a lesser degree, of mice, rabbits and rats. They were silver negative. Their dense core reacted to PTA but their matrix, contrary to classical MVB without a dense core, did not.
Histological and ultrastructural observations of tail bud formation in the chick embryo
Authors: Schoenwolf Gary C.
Published: February 2005

Tail bud formation was studied in chick embryos by light and electron microscopy. The caudal part of the neural groove at stage 11 is flanked by widely separated neural folds and merges posteriorly with the shallow primitive groove. The neural groove and primitive streak partially overlap. The depth of the neural groove gradually decreases antero‐posteriorly within this overlap zone while the dorso‐ventral thickness of the streak progressively increases. The anterior end of the streak begins to form a spherical accumulation of mesenchymal cells, the incipient tail bud, concomitant with closure of the posterior neuropore. Formation of the posterior body fold results in consolidation of the remainder of the streak into the definitive tail bud. The overlap zone between neural groove and primitive streak is retained as the tail bud forms. Thus the posterior end of the neural tube and anterior end of the tail bud overlap. The latter undergoes cavitation to form the ventral part of the spinal cord within this overlap region.

The tail bud is initially continuous with an overlying, flattened layer of ectoderm and an underlying, columnar layer of endoderm. A bilaminar ectodermal epithelium forms directly above the developing neural tube as the dorsal portion of the tail bud undergoes cavitation. Most of the endodermal cells are displaced from the ventral surface of the tail bud by the posterior body fold and condensed into a disk‐shaped region which ultimately gives rise to tail gut.
Renal regeneration following D‐serine induced acute tubular necrosis
Authors: Peterson Darryl R. , Carone Frank A.
Published: February 2005

Regeneration of the rat kidney was observed for six days after inducing acute tubular necrosis of the proximal pars recta with d‐serine (80 mg/100g body weight). Regenerating cells appear by two days post‐treatment, and re‐epithelialization of the nephron is completed within six days, with the most mature cells approaching normal morphology. Regeneration originates from viable cells adjacent to the necrotic zone which divide and follow a template provided by the intact basement membrane. Transient, cytoplasmic regenerative activity among developing tubular cells is characterized by the presence of large, irregularly shaped nuclei, prominent nucleoli, abundant ribosomes and lysosomes, and abnormal mitochondrial configurations. Microfilaments appear to be involved in the formation of apical microvilli and the basal labyrinth of plasmalemmal convolutions. These data suggest that d‐serine. inducedacute tubular necrosis of the proximal pars recta may be followed by rapid, patterned regeneration along an intact basement membrane, and that microfilaments are involved in differentiation of cellular morphology.
The effect of dichloromethylene diphosphonate, a pyrophosphate analog, on bone and bone cell structure in the growing rat
Authors: Miller Scott C. , Jee Webster S. S.
Published: February 2005

Dichloromethylene diphosphonate (Cl2MDP) is a synthetic compound related in structure to inorganic pyrophosphate but is resistant to enzymatic and chemical degradation and is known to be a potent inhibitor of bone resorption. The administration of 20 mg/kg/day of Cl2MDP for ten days to growing rats results in marked increases in metaphyseal mineralized tissue mass due to slowed bone resorption. There was an increase in resorption areas covering anorganic bone viewed by scanning electron microscopy (SEM), however, the resorption pits, or Howship's lacunae, in these resorption areas were smaller and less defined than those encountered in controls. The appearance of these large areas of poorly delineated resorption pits is likely due to an inhibition of bone resorption coupled with slowed bone formation. Administration of Cl2MDP to growing rats also results in an increase in the numbers and size of osteoclasts. Because this would appear to be a histological paradox, in view of the ability of Cl2MDP to slow bone resorption, the osteoclasts were examined by transmission electron microscopy (TEM). The ruffled borders and associated cytoplasmic vacuoles were generally less extensive in the Cl2MDP‐treated osteoclasts than in controls, even though clear zones were frequently seen. Examination of undecalcified light microscope sections reveal that the area of bone being degraded by adjacent osteoclasts was generally much smaller in the Cl2MDP‐treated animals than in controls. Thus the collaborating TEM observations of smaller ruffled borders, with the SEM observations of smaller, less‐de‐fined resorption pits, with the light microscope observations of smaller bone areas being degraded by individual osteoclasts provide a morphological basis for the observed decreases in bone resorption following Cl2MDP administration.
Development of the intrarenal vascular system of the puppy kidney
Authors: Evan Andrew P. , Stoeckel James A. , Loemker Vickie , Baker Jeffrey T.
Published: February 2005

This study investigates the development of the vascular system of the puppy kidney (1‐21 days after birth) after preparing casts of the renal vessels. At two days, the intrarenal vascular system distal to the afferent arteriole is strikingly different than that of the adult. The glomeruli of the outer cortex consist of a single dilated vessel while those of the mid and inner cortex possess an increasingly larger number of capillary loops. The efferent arterioles vary greatly in appearance from outer to inner cortex. Those in the nephrogenic zone are characteristically short and narrow and join a larger venous vessel termined a sinusoidal capillary. An efferent system somewhat similar to that of the adult is seen in the mid and inner cortex. One of the most obvious differences noted between the puppy and adult kidney is the relative lack of peritubular capillary networks throughout the cortex of the puppy kidney. The puppy possesses large, irregular vessels termed sinusoidal capillaries. The most rudimentary sinusoids are found in the outer cortex with more mature vessels in the inner cortex. The vascular arrangement of the efferent arteriole and sinusoidal capillary appears as a post‐glomerular shunt. Functionally, the shunt would direct blood flow away from the proximal tubule and thus could result in a low extraction ratio and Tm for secreted solutes.
Mitoses in peripheral pulmonary epithelium: The effect of colchicine
Authors: Baron David A. , Esterly John R.
Published: February 2005

Injury in the periphery of the lung was studied in rats given intratracheal trypsin. Mitotic figures were noted in the alveolar epithelium, and colchicine enhanced the yield. Of 65 mitotic figures examined in detail, 46 were present in the alveolar epithelium. Epithelial mitoses were confined to type II cells, many of which contained lamellar inclusions, abundant rough endoplasmic reticulum, and luminal microvilli. Mitoses were not seen in type I cells or in less well differentiated epithelial cells, but they were noted in occasional endothelial and interstitial cells. Colchicine‐arrested type II cells were distinguished by radially disposed chromosomes surrounding pairs of centrioles and randomly oriented microtubules. In addition, many of these cells showed a pronounced cortical zone, devoid of microvilli, and others showed cytotoxic degenerative changes. These observations indicate that the alveolar epithelium is renewed exclusively by division of differentiated type II cells.
“Silver dust”—a tool to study growth interrelationships between bone, periosteum and muscle
Authors: Grimm Arthur F. , Katele Kazimieras V.
Published: February 2005

A cylinder of gelatin containing silver spongy granules was placed in and lay within the masseter muscle, the periosteum, and the mandible, and terminated in the medial pterygoid muscle of young (3 month‐old) growing miniature pigs.

On the basis of an animal sacrificed one week after placement of the cylinder, it was found that the suspending gelatin was removed by cellular activity. Nine months later the remaining animals were sacrificed. Periodic X‐rays were taken during the course of the experiment. After sacrifice, the mandible and associated tissues were histologically examined. The results of this study suggest that the silver granules in the muscles maintained their location during growth; the silver granules in the mandible moved forward with mandibular growth. “Slippage” appeared to occur external to the fibrous layer of the periosteum; the site of movement was revealed by the trail of the silver granules. The described method should prove of value in studying the growth interrelationships between bone, periosteum, and muscle.
Specific granules of the rat atrial muscle cell
Authors: Seiden David
Published: February 2005

The specific granules found in the atrial cardiac muscle cells of the normal rat were studied. The ultrastructural appearance of these granules demonstrates a fixative‐dependent lability. Fixation with cacodylate buffered aldehydes yields three types of granules. However, fixation with phosphate buffered aldehvdes or primary fixation with OsO4 yields granules of uniform appearance. The granules are found predominantly in the perinuclear zone; 78% of the granules are within ten linear micrometers of the center of the nucleus. Two independent methods of measurement demonstrate spherical diameters of these granules of 0.30 μm and 0.37 μ respectively. The granules are found in greater concentration at one pole of the nucleus than at the other. On the high density side there are 4.07 granules/μm3 which occupy 5.8% of the cytoplasmic volume. On the low density side there are 2.15 granules/μm3 which occupy 3.0% of the cytoplasmic volume. The granules at both poles are the same size. Atrial walls were incubated in a modified Tyrode's solution. One hour of incubation caused no change in the atrial granules. Addition of norepinephrine or L‐Dopa resulted in the appearance of more granules but the size of the granules remained the same. Incubation with reserpine had no effect upon the atrial granules. Apparently the atrial myocardial cell is stimulated by exogenous catechol‐amine to synthesize more atrial granules which themselves do not appear to contain catecholamines.
Crystalloids of actin‐like filaments in the sertoli cell of the swine testis
Authors: Toyama Yoshiro , Obinata Takashi , Holtzer Howard
Published: February 2005

Normal swine testes, congenital cryptorchid swine testes, and normal human testes were exposed to HMM (heavy meromyosin) after either glycerination or saponin treatment in order to determine whether the fine filaments composing the crystalloids in the Sertoli cells are actin‐like. The microfilaments of the crystalloids in the Sertoli cells of the cryptorchid swine testes bind HMM to form arrowhead complexes. Short bundles of microfilaments observed in the basal part of the Sertoli cells in both normal and cryptorchid testes also bind HMM. Similar bundles of HMM‐bound filaments are observed in the vicinity of spermatocytes. The periodicity of the arrowhead complexes is about 35 nm, and all arrowheads on a given filament point in the same direction. In addition, the polarity of the HMM‐bound filaments in a given crystalloid or bundle is uni‐directional. A mechanism for the formation of the swine crystalloids has been suggested by Toyama (′75), and the results of this study strongly support this hypothesis.

Fine filaments of Charcot‐Boettcher's crystalloid in human Sertoli cells did not bind HMM. Therefore the fine filaments of the human crystalloid are not actin‐like in nature.
Cell junctions in the endothelia and connective tissue of the rat choroid plexus
Authors: van Deurs B.
Published: February 2005

Cell junctions between endothelial cells and between connective tissue cells (leptomeninges) of the rat choroid plexus were studied by freeze‐fracture. Special attention was paid to the problems of identifying fractured cell membranes and fracture faces. Tight junctions in arterioles are comprised of continuous small‐meshed networks of strands appearing as shallow grooves with aligned particles on E‐faces, and low ridges with some particles on P‐faces. In the fenestrated capillaries the tight junctions are represented by discontinuous, isolated slightly elevated ridges with some particles on P‐faces, and corresponding shallow grooves devoid of particles on E‐faces. Junctions in venules appeared as a less developed version of the junctions in the fenestrated capillaries. Extended areas of the meningeal cell membranes exhibit cell junctions. Tight junctions in this tissue are comprised of a loose discontinuous arrangement of isolated, often branched junctional elements. On P‐faces the elements appear as elongated crests with a distinct furrow running along the edge of the crest, occupied by a few particles. On E‐faces corresponding elongated impressions are present and occupied by aligned particles and a few short bars. The arrangement of these tight junction elements are not supportive of any significant barrier function. Small gap junctions occur “freely” in the membrane, or they are sometimes surrounded by tight junction elements. Very large gap junctions (up to about 10,000 particles) are mostly surrounded and interconnected by tight junctional elements. The possible significance of the variability of gap junction size, and the relation to tight junction elements is discussed.
Focal laminate segments in cytoplasmic processes of mouse myocardial fibroblasts
Authors: Forbes M. S. , Sperelakis N.
Published: February 2005

In mouse ventricular myocardium, we have found unusual fibroblasts whose cellular processes in some regions are particularly flattened and which contain linearly‐arranged, electron‐opaque structures (“central laminae”). The morphology of these focal laminate segments of fibroblast processes suggests that the intracellular laminae are adhesive entitieswhich hold the plasmalemmata above and below them in close parallel apposition for short distances.
Morphology of the atrioventricular node, bundle and proximal bundle branches: A study employing computerized reconstruction
Authors: Roberts Nigel K. , Castleman Kenneth R.
Published: February 2005

The morphology of the human atrioventricular node, atrioventricular bundle and bundle branches is described. A block of tissue bounded by the ostium of the coronary sinus, the pars membranacea, the septal leaflet of the tricuspid valve and the atrial and ventricular septa is removed. This block is then sectioned serially from the right endocardial surface in the frontal plane of the heart. Sectioning in this way produces fewer sections than from techniques previously described. Outlines of the atrioventricular node, atrioventricular bundle and proximal bundle branches are digitally registered and stored in a computer. Three dimensional reconstructions of the structures are then generated by computer and displayed on an oscilloscope so that the entire three dimensional image can be rotated in any plane. Stereoscopic image pairs are produced to assist perception of the shape of the atrioventricular node, bundle and branching patterns of the bundles. This technique is unique in that it describes a method from which a relatively small number of histologic sectionsare generated permitting not only a complete histologic examination, but also a study of the morphology of the area.
Morphogenesis of rod cells in the retina of the albino rat: A scanning electronmicroscopic study
Authors: Galbavy Edward S. J. , Olson Mark D.
Published: February 2005

This study presents scanning electron microscopic (SEM) observations of topographicalchanges that occur during morphogenesis of rod cells in the albino rat. Correlative transmission electron microscopy (TEM) was also utilized. Albino rats ranging in age from birth to three weeks were used for the study. Tissues were prepared by conventional methods for SEM and TEM.

At birth, numerous irregularly arranged inner segments extend from the external surface of the sensory retina. They are spherical, smooth surfaced and possess a randomly oriented cilium. The internal morphology of these immature inner segments is comparable to that observed in other vertebrate species. Statistical analysis reveals a rapid increase in the number of rod cells during the first week. This period is characterized by the elongation of inner segments and their associated cilia. Microvilli project from the apices of Müller cells, but not from adjacent inner segments.

By day 5, cilia occasionally display small bulbous outer segments. They are more numerous by day 8 and are usually eccentrically positioned at the tips of cilia. By day 11, outer segments are abundant and frequently obscure from view the underlying inner segments and associated cilia. Elongated cylindrical outer segments are present within the posterior retina at the end of the second week. However, rod cell morphogenesis lags in the peripheral retina. Topographical variations between developing photoreceptor cells in mammalian and non‐mammalian retinas are discussed.
The origin of the extrinsic adrenergic innervation to the rat ovary
Authors: Lawrence Irvin E. , Burden Hubert W.
Published: February 2005

Cutting the suspensory ligament reduced the ovarian content of norepinephrine (NE) to less than half that of controls and only a few blood vessels had perivascular fibers and an occasional nerve remained in the interstitial gland. Cutting the ovarian plexus had a less drastic, but similar effect on the ovarian content of NE and on the pattern of ovarian adrenergic nerves. Cutting both the suspensory ligament and ovarian plexus eliminated visualization of ovarian adrenergic nerves, but some ovarian NE was still measurable. Fluorescence and electron microscopic studies of the suspensory liagament revealed a large adrenergic nerve embedded in smooth muscle of the ligament. The nerve was also acetylcholinesterase‐positive. Cutting the celiac plexus or incising a small nerve lateral to the plexus and medial to the origin of the suspensory ligament, had the same effect on the ovarian adrenergic nerves as cutting the suspensory ligament. It is concluded that the extrinsic adrenergic nerves to the rat ovary reach the organ by two routes: one via the nerve in the suspensory ligament (superior ovarian nerve), and one via the traditionally described ovarian plexus along the ovarian artery.
Morphologic abnormalities in the postnatal differentiation of CA1 pyramidal cells and granule cells in the hippocampal formation of the Ataxic mouse
Authors: Burt Alvin M.
Published: February 2005

The postnatal differentiation of the hippocampal formation of the ataxic mouse was studied. Brains from ataxic mice (axJ/axJ) and littermate controls (+/?), from 19 to 51 days of age, were either impregnated according to a Golgi‐Cox procedure or sectioned and stained with Weil‐hematoxylin and Darrow Red. The hippocampus and dentate gyrus, although somewhat reduced in cross‐sectional area in the ataxic brain, appeared to have a normal complement of both pyramidal cells and granule cells, respectively. Examination of Golgi‐Cox material showed significant differences in the differentiation of the dendritic tree of both pyramidal and granule cells. At 41 days the height of the apical dendrite of CA1 pyramidal cells in the ataxic brain was 76% of the control value, and the width was only 35%. Similarly, the basal dendritic tree was narrower in the ataxic mouse. In the dentate gyrus of the 41‐day ataxic brain, the height of the granule cell dendritic tree was only 74% of the control value. These and other alterations in the dendritic morphology of both CA1 pyramidal cells and granule cells can be explained by a lack of growth of the dendritic tree during the developmental period studied. These findings are discussed in relation to other studies on intrinsic and extrinsic factors and their effect on normal hippocampal differentiation.
Heterogeneity of the MtTW15 mammosomatotropic tumor. II. Characterization of parenchymal cells by superimposition immunocytochemistry and electron microscopy
Authors: Parsons J. A. , Baskin D. G. , Erlandsen S. L.
Published: February 2005

Large MtTW15 tumors, which secrete growth hormone (GH) and prolactin (PRL), are composed of ovoid, elongated, and angular cells which demonstrated interdigitating processes and junctional complexes. The majority of the cells were essentially agranular, but two types of granulated cells were identifiable. One class of granulated cells contained moderate to sparse populations of round dense‐cored granules measuring up to 250 nm in diameter. Rod‐shaped to filamentous mitochondria with an electron‐dense matrix were characteristic of a second class of granulated cells with pleomorphic granules of various sizes and electron densities. Images of exocytotic release of the round dense‐cored granules were frequently seen, but were not observed with the pleomorphic granules, many of which were judged to be lysosomes. Superimposition immunocytochemistry revealed hormones only in the granulated cells with round to ovoid granules. Morphometry indicated that hormone specific subpopulations of tumor cells can be identified since PRL secretory granules were significantly smaller than GH secretory granules (149 ± 6 nm for PRL versus 221 ± 9 nm for GH, P < 0.001). The vast majority of immunopositive cells contained only GH or PRL, but a few were observed containing both hormones. Ovoid to irregular‐shaped nuclei, large lipid inclusions, numerous free ribosomes and polyribosomes, moderate development of the rough endoplasmic reticulum, and prominent Golgi profiles were characteristics of all cell types. Irrespective of the presence or absence of cytoplasmic granular elements, particles resembling viruses were encountered in many tumor cells, and these frequently appeared to be budding into the cisternae of the endoplasmic reticulum.
Ultrastructural and biochemical effects of D‐penicillamine on mouse hepatocytes
Authors: Walter Robert J. , Tandler Bernard , Hoppel Charles L.
Published: February 2005

The ultrastructural and oxidative metabolic effects of D‐penicillamine were examined in hepatocytes of mice fed various concentrations of the drug for periods up to 11 days. In virtually all animals studied, membranous material in the form of whorls, sheaves, and irregular networks was observed in some bile canaliculi. In several mice a few mitochondria were substantially enlarged, with diameters of 4‐6 μm. In other animals some mitochondria became quite elongated, measuring 10 μm in length but only 0.5 μm in width. Certain mitochondria had small deposits of dense material in their outer compartment. Lysosomes contained numerous small dense particles; aggregates of these particles were also observed free in the cytosol. Despite these alterations, the vast majority of hepatocytes showed no changes whatsoever. Study of isolated hepatic mitochondria derived from the experimental animals showed no alterations in oxidative metabolism. It may be concluded that, unlike other copper‐chelating agents, D‐penicillamine has little significant morphological and biochemical effect on mouse hepatocytes, even when its concentration exceeds standard clinical dosages.
Responses of mouse spleen morphology to the growth of subcutaneously injected virally transformed cells
Authors: Nutter Robert L. , Gridley Daila S. , Slater James M. , McMillan Paul J.
Published: February 2005

The changes in the fractional volume of six structural components in the spleens of Balb/C mice injected with Herpes simplex virus Type 2‐transformed cells (H238 tumor cells) were quantitated during progressive tumor growth. Spleen sterology was performed at three time intervals during the early stages of tumor development. The results revealed that the volume of the compact myeloid tissue and reaction centers of lymphoid nodules increased about four‐ to five‐fold from 10 to 33 days after H238 tumor cell injection. A progressive increase was also seen in the red pulp volume. Although an increase in volume of the marginal zones around the lymphoid nodules was evident early during the test period, by day 33 the mean value was similar to the control value. These results indicate that the spleen undergoes significant morphological changes in three splenic components during progressive growth of a tumor produced by subcutaneous injection of a virally‐transformed cell line.
Necrotic extrafusal muscle fibers of the dystrophic mutant mouse: The ultrastructure of the myoneural junction
Authors: Ontell Marcia , Haller Edward
Published: February 2005

At 28 days postpartum, the extensor digitorum longus muscle of the dy2J mutant mouse contains a population of myofibers which exhibit coagulation necrosis for ˜90% of their length. Using the electron microscope, motor endplates were found on more than half of the necrotic fibers studied, occurring in mildly, moderately, and severely necrotic regions of these fibers. The ultrastructural features of the axonal terminals did not vary with the condition of the fiber segment at which the endplate occurred. No morphological criteria could be established for distinguishing between the axonal terminals of necrotic fibers and those of “healthy” fibers in the dystrophic animal. The principle morphological changes at motor endplates of necrotic fibers involved not the axonal terminal, but the muscle fiber itself.

This study demonstrates that the necrotic myofibers, which are present at the onset of the first clinical symptoms of murine dystrophy, are innervated. Therefore, necrosis is not precipitated by structural denervation. Furthermore, observations of motor endplates on mildly, moderately, and severely necroctic regions of the myofibers indicate that regional changes along the necrotic fiber 's length are not a function of distance from the motor endplate.
Muscle spindle supply to the bovine jaw muscles
Authors: Kubota Kinziro , Komatsu Shigeru , Nakamura Mitsutaka , Masegi Toshiaki
Published: February 2005

The jaw‐closing muscles of two bovine fetuses average 1,177 muscle spindles on one side of the face: 549 in the masseter, 433 in the temporalis, 192 in the medial pterygoid, and three in the lateral pterygoid. The jaw‐opening muscles have no spindles.
Accumulation of CPC‐precipitable material at apical cell surfaces during formation of the optic cup
Authors: Robert. Hilfer S. , Yang Jyh‐Jla W.
Published: February 2005

Accumulation of extracellular material at the apical surfaces of cells in the optic vesicle was studied by precipitation with cetylpyridinium chloride (CPC) and scanning electron microscopy. Treatment at low salt concentration to preserve all precipitable material indicated an initial appearance of surface material at the time that the retinal primordium first formed. The amount of precipitate increased as the optic cup formed, particularly at the margins of the cup. Stability of the precipitate during subsequent washing at higher salt concentrations suggested that the apical cell surface material contained highly acidic glycosaminoglycans. The greatest resistance to extraction occurred during the period in which invagination was most pronounced.
Muscle sarcomere length following passive jaw opening in the rabbit
Authors: Hertzberg S. R. , Muhl Z. F. , Begole E. A.
Published: February 2005

Sarcomere lengths were measured microscopically in formalin‐fixed jaw muscles of 14 rabbits divided into two groups; jaw open, and jaw closed. The measurements were compared by means of a nested analysis of variance. The sarcomeres of the jaw open group were longer in the masseter and temporalis muscles (jaw elevators) and shorter in the digastric muscle (jaw depressor) than were those of the jaw closed group. In the jaw closed position, sarcomeres in the deep portion of the masseter muscle become markedly shorter than those in the superficial part of the muscle. The values for sarcomere length in the masseter muscle of the jaw open group and the digastric of the jaw closed group are near the top of the ascending limb of isometric length‐tension relation for the rabbit digastric muscle.
Ependymal astrocytes in the frog cerebellum
Authors: Korte Gary E. , Rosenbluth Jack
Published: February 2005

We have examined the ependymal astrocytes of the frog cerebellar cortex in thin sections and freeze‐fracture replicas. The somata border the fourth ventricle and give rise to basal processes whose daughter branches cross the molecular layer and terminate as subpial endfeet. Irregular lamellar appendages arise from the basal processes and their branches. In the molecular layer the appendages selectively ensheath apposed parallel fiber boutons and Purkinje cell dendritic spines. Other appendages ramify throughout the neuropil, some contributing to extensive pericapillary sheaths.

Freeze‐fractured ependymal astrocyte plasma membrane consistently has a greater concentration of intramembranous particles (IMPs) and IMPs of larger mean size than neuronal plasma membrane in the same replicas. Like the astrocytes of the mammalian central nervous system, frog ependymal astrocytes form numerous gap junctions with each other. However, orthogonal arrays of IMPs (“assemblies”) were not observed.

Ependymal cells in the frog cerebellum combine the morphology, and probably the functions, of both ependymal cells and astrocytes.
Anatomy of the nasal‐pharyngeal airway of experimental animals
Authors: Schreider Jay P. , Raabe Otto G.
Published: February 2005

Silicone rubber casts were prepared of the nasal, pharyngeal and laryngeal regions of two rats, a rhesus monkey, and three beagle dogs and one for each species selected for detailed measurements. Cross‐sections of the casts were made and the area and perimeter of each section measured using an image analyzing computer. Considerable anatomical differences were found between the species. Some of the differences, such as the sharp bend in the nasopharynx of the monkey, could be related to normal posture. One of the main differences was the greater complexity of the turbinate region of the dog as compared to the corresponding area of the monkey.
Permeability to lanthanum of blood testis barrier in human germinal aplasia
Authors: Camatini Marina , Franchi Emilia , Decurtis Ivan
Published: February 2005

The permeability of Sertoli tight junctions to lanthanum administrated during fixation is demonstrated in biopsies of patients with partial germinal aplasia. In freeze‐fracture replicas the number of fibrils is not significantly different from the data obtained in normal testis. Thus, in these pathological conditions junctional permeability is not related solely to the complexity of the network revealed by freeze‐fracture.
Innervation of rat antral gastrin‐producing cells
Authors: Lechago Juan , Barajas Luciano
Published: February 2005

The innervation of rat antral gastrin‐producing cells (G‐cells) was studied by light and electron microscopy. Combination of histochemistry for acetylcholinesterase and immunofluorescence for gastrin in the same tissue section showed apparent contact between some of the G‐cells and acetylcholinesterase‐positive nerves. Electron microscopic observation, however, revealed gaps of 200–500 nm or more between the G‐cells and the closest nerve axons which often contained large dense‐cored vesicles. The latter may represent the storage sites for neuropeptides previously localized by immunohistochemistry in gastric nerves.
Hypertrophic and hyperplastic effects of thyroxine on the submandibular gland of the mouse
Authors: Gresik E. W. , van der Noen H. , Barka T.
Published: February 2005

The nature of the trophic response of the mouse submandibular gland to thyroxine (T4) was examined. Adult female Swiss‐ Webster mice were given daily subcutaneous injections of T4 (1 μg/gm body weight) for two or four days; two injections of tritiated thymidine (3H‐ TdR) were given 24 and 29 hours after the last injection of hormone, and the mice were killed one hour after the last injection of 3H‐ TdR. One gland was analyzed chemically for DNA content and for incorporation of 3H‐ TdR, while the other was used to prepare autoradiograms. The cellular composition of each gland was analyzed by counting 1000 nuclei, and the frequency and labelling index (LI) of six cell types were established. A rise in specific activity of DNA and a fall in its concentration were seen in response to T4. The LI for the entire gland more than doubled. The LIs and frequencies of granular convoluted tubule and granular intercalated duct cells were increased more than those of acinar and nongranular intercalated duct cells; striated and excretory duct cells were not affected. It is concluded that the enlargement of the submandibular gland of the mouse caused by T4 is due to both hyperplastic and hypertrophic effects.
Organization of collagen in the human pulmonary alveolar wall
Authors: Rosenquist Thomas H.
Published: February 2005

The purpose of this study was to determine the organization of collagen in the wall of the human pulmonary alveolus. Samples of human lung obtained at surgery were processed for light and electron microscopy. Light microscopy confirmed the general findings of Orsos ('36): there were 3 common fibers called primary, secondary, tertiary in this study in order of their increasing size. Primary fibers (called “pericapillary” by Orsos) formed a continuous mesh in the alveolar wall and were often confluent within the intercapillary regions of the wall (“knötenpunkten,” or nodes, Orsos). The tortuous secondary fibers (“circulatory fibers,” Orsos) passed frequently across the thickness of the alveolar wall and were closely applied to capillary walls. Tertiary fibers (“respiratory fibers,” Orsos) were continuous with the alveolar ostia and formed the supportive struts of the alveolar wall as they crossed the wall in a more direct course than the serpiginous secondary fibers.

Electron microscopy (serial sections and stereo pairs) showed that the primary fibers inserted near the edge of an intercapillary region, where they were attached to the endothelial or epithelial basal lamina directly or by a smaller fiber or microfibril resembling the fibrous component of elastin or oxytalan. Primary fibers passed through a typical intercapillary region while describing a helix or a portion thereof. Secondary fibers were more coarse than primary, and both secondary and tertiary fibers resembled woven ropes.
Uptake of radioiodine in follicles of dog C‐cell complexes studied by autoradiograph and immunoperoxidase staining
Authors: Kameda Yoko , Ikeda Kazuo , Ikeda Akira
Published: February 2005

C‐cell complexes are special cell groups consisting of a mass of C‐cells associated with other epithelial elements and cysts. They are remnants of ultimobranchial bodies retaining fetal characteristics. In the C‐cell complexes there are follicular cells in various stages of differentiation, i.e., the cell clusters not yet organized into follicles, primordial follicles with small lumens and comparatively enlarged follicles storing plentiful amounts of colloid. They have a morphology similar to follicular cells of fetal thyroid glands and react to antiserum to 19S thyroglobulin. In order to determine whether or not the follicles in these complexes have the ability to incorporate radioiodine, autoradiography after a single injection of 125I was combined with immunoperoxidase staining using specific anti‐calcitonin, anti‐C‐thyroglobulin, and anti‐19S thyroglobulin antisera. The 19S‐positive cells not yet organized into follicles did not take up radioiodine. Primordial follicles showed a heavy accumulation of silver grains over their follicular lumens storing new 19S thyroglobulin as colloid. Comparatively enlarged follicles revealed a strong autoradiographic reaction and their labeling patterns were identical with those of typical thyroid follicles. These results confirm that the follicles in C‐cell complexes, as well as thyroid follicles, can incorporate radioiodine and are related to thyroid hormone synthesis. That is, functional thyroid follicles can arise from the ultimobranchial bodies.
A quantitative morphological analysis of interatrial muscle cells in the ferret heart
Authors: Marino Thomas A. , Biberstein Denise , Nong Cook P. , Cook Larry , Dwyer Samuel J.
Published: February 2005

Cells located in the interatrial septum of the ferret heart were examined and mean cell volume, surface area, length, width, as well as cell length/width and surface area/volume ratios were obtained. The muscle cells were from two different regions. One region was the area of the middle internodal tract while the other was from the area where the anterior and middle internodal tracts intermingled. Based on the data obtained, at least two different subpopulations of interatrial muscle cells could be defined. The larger cells had a mean cell length of 109.7 μm, a mean cell width of 13.1 μm, a length/width ratio of 8.61, a mean cell surface area of 5,057.6 μm2, a mean cell volume of 5960.8 μm3, and a surface area/volume ratio of 0.87. The smaller cells had a mean cell length of 58.0 μm, a mean cell width of 12.2 μm, a length/width ratio of 4.85, a mean cell surface area of 2494.1 μm2, a mean cell volume of 2553.6 μm3, and a surface area/volume ratio of 1.00. The large cell population had cells that were myofibril rich and also others that were myofibril poor. These quantitative data indicate that the regions of internodal pathways are not composed of a single specialized cell type, but rather are composed of at least two, if not more, cell types that intermingle with each other.
Some effects of protein‐calorie undernutrition on the developing central nervous system of the rat
Authors: Noback Charles R. , Eisenman Leonard M.
Published: February 2005

Some effects of undernutrition were noted in the brains of 21‐day‐old rat pups undernourished from birth by being reared by nursing dams fed on a low protein diet. As compared to the normally fed control pups, the body weight, brain weight, and thickness of the parietal neocortex and paravermal cerebellar cortex were significantly lower in the undernourished pups (p < 0.001), while the thickness of the cortices of the dentate gyrus and hippocampus CA3 only reached significance at the 5% level. Again, as compared to the control pups, the number of spines per unit length on the distal dendritic segments of the pyramidal cells of lamina III of the parietal neocortex and of the hippocampus CA3 reached significance at the 5% level whereas that of the granule cells of dentate gyrus and Purkinje cells of the paravermis did not reach significance at the 5% level. The myelination of the pyramidal tract and spinal trigeminal tract in the lower medulla was less advanced in the undernourished pups.

To date, the demonstration of precise functional correlates for the observed changes of morphological and physiological parameters in animals subjected to undernutrition has been elusive. An approach that may lead to unraveling this problem is suggested in a discussion of relating sources of input to the specific dendritic segments where the spine counts were made.
Central connections of the olfactory bulb in the american opossum (didelphys virginiana): A light microscopic degeneration study
Authors: Meyer R. Peter
Published: February 2005

Destructive lesions were made in the right olfactory bulb of 16 adult opossums. Following postoperative survival periods of 4 to 31 days, the animals were sacrificed and perfused with 10% Formalin. Frozen sections of the brain were cut in either the coronal, horizontal, or sagittal plane and processed by the Fink‐Heimer II method. Degenerating axons of olfactory bulb neurons were traced caudally in the ipsilateral lateral olfactory tract (LOT). Small lesions revealed a topographic representation of the olfactory bulb within the LOT. The dorsal, lateral, and ventral parts of the bulb were, respectively, represented in the dorsal, intermediate, and ventral parts of the LOT. Terminal degeneration was observed in the superficial half of the molecular layer ipsilaterally in the following structures: anterior olfactory nucleus, anterior hippocampal rudiment, olfactory tubercle, piriform cortex, ventrolateral frontal neocortex, lateral entorhinal cortex, nucleus of the LOT, and the lateral aspect of the cortical amygdaloid nucleus. No degeneration was observed in the anterior limb of the anterior commissure. Dorsal and lateral parts of the olfactory bulb projected to the anterolateral aspect of the olfactory tubercle, whereas the ventral part projected heavily to the entire tubercle. There was no evidence of topographic projections to other olfactory structures. The observations of the present investigation indicated that the olfactory bulb projections in the opossum, a primitive mammal, are essentially comparable with those of placental mammals.