bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure of the complex basement membrane underlying the epithelium of the vas deferens in the rat
Authors: Clermont Y. , Hermo L.
Published: February 2005

Underlying the epithelium of the vas deferens there is a complex basement membrane showing a thick lamina densa separated from the plasma membrane of epithelial cells by a lamina lucida. On the connective tissue side of the lamina densa, there are plaques composed of a material that is similar to that of the lamina densa but is more compact and has a greater electron density. This material also forms plaques at a short distance from the lamina densa, where it appears as irregular nodular masses. The plaques are bridged by striated anchoring fibrils (SAF) that are variable in structure. Some SAF are long (0.5–0.6 μm) and bilaterally symmetrical, with a central fusiform segment and, on each side, coarsely banded segments. While the fusiform segment presents 5 or 6 diffuse cross striations, the coarsely banded segments show distinct bands labeled B1−B4. Shorter SAF show a coarsely banded segment alone or a coarsely banded segment plus a fusiform segment. Some SAF also branch at the level of the fusiform segments, in which case they from star‐shaped structures with three or more branches that have their extremities inserted into plaques. The plaques, as well as the lamina densa, are immunohistochemically reactive to type IV collagen, laminin, and heparan sulfate proteoglycan, whereas the SAF are not immunoreactive to these substances. SAF and plaques, considered as integral components of this basement membrane, form a series of arches or open tunnels traversed by collagen fibrils. It is thus apparent that these elements contribute to the attachment of the basement membrane and the overlying epithelium to the underlying dense connective tissue of the lamina propria.
Unilateral hindpaw amputation causes bilateral articular cartilage remodeling of the rat hip joint
Authors: Joseph Threlkeld A. , Smith Stephen D.
Published: February 2005

The purpose of this paper was to describe the remodeling of adult coxofemoral articular cartilage (AC) in response to altered weight bearing. Twelve adult male Sprague‐Dawley rats underwent unilateral hindpaw transection at the distal tibiofibular junction (AmpCont group); another group of eight rats served as normal controls (Norm group). Subpopulations of both groups were injected with 35SO4 24 hr before harvest. All femora were harvested after 8 weeks. Safranin O stained longitudinal sections were used to determine AC thickness, cellularity, and proteoglycan (PG) staining. Regional grain counting was performed on autoradiographs. Analysis of the data revealed that the AC of Norm hips in the region near the fovea capitis femoris was significantly thicker, had a lower cell density, a greater PG density, and a lower 35SO4 incorporation rate per chondrocyte than the AC of the Norm lateral edge region. The intact limbs of the AmpCont animals demonstrated a relative thinning of the AC near the fovea capitis femoris, compared with the edge region, and reduced 35SO4 incorporation rate in the lateral edge region, compared with normal values. The operated limb of the AmpCont animals displayed a relative increase of PG density in the edge region compared with the foveal region and a reduced 35SO4 incorporation rate in the lateral edge region, compared with normal values We concluded that rat coxofemoral AC responds bilaterally to unilateral hindpaw amputation through appropriate morphologic remodeling.
Functional units in rainbow trout (Salmo gairdneri, Richardson) liver: II. The biliary system
Authors: Hampton James A. , Clark Lantz R. , Goldblatt Peter J. , Lauren Darrel J. , Hinton David E.
Published: February 2005

The intrahepatic biliary system was studied in the rainbow trout (Salmo gairdneri), a teleost known to form liver neoplasms after exposure to various carcinogens. Normal adults (N = 25) were examined using light microscopic, enzyme histochemical, and transmission and scanning electron microscopic methods. In light micrographs, longitudinal arrays of hepatocytes appeared as double rows incompletely divided by elongated darkly stained cells. Electron micrographs showed tubules of five to nine pyramidally shaped hepatocytes with their apices directed toward a central biliary passageway and their bases directed toward sinusoids. Sequentially, beginning with hepatocytes, biliary passageways included canaliculi, preductules, ductules, and ducts. Canaliculi were short and joined transitional passageways (preductules) formed by junctional complexes between plasma membranes of hepatocytes and small, electron‐dense cells with a high nuclear to cytoplasmic ratio. Ductules, completely lined by biliary epithelial cells, occupied central regions of hepatic tubules. Relatively elongated, ductular cells were intimately associated with surrounding hepatocytes, separated from them by only a thin extracellular space devoid of a basal lamina. Epithelium of bile ducts included cuboidal through mucus‐laden columnar cells, surrounded by basal lamina and, in larger ducts, by fibroblasts, smooth muscle cells, and a capillary plexus. Bile ducts and hepatic arterioles, but not venules, were distributed together. The ultrastructure of biliary epithelium, periductular, and periductal cells is presented.
Histochemical, immunohistochemical, and ultrastructural observations on the iris muscles of Gallus gallus
Authors: Scapolo P. A. , Peirone S. M. , Filogamo G. , Veggetti A.
Published: February 2005

The distribution and typology of fibers in the two muscular systems (sphincter and dilator) of the iris in Gallus gallus were determined histochemically, immunohistochemically, and ultrastructurally. The sphincter muscle in proximity to the ciliary margin was composed predominantly of slow fibers. In the intermediate tract, a large group of fast oxidative fibers were evident and the pupillary margin was exclusively composed of slow fibers. The fast‐fibers had histochemical and immunohistochemical patterns similar to the α fibers in the skeletal control muscle (biventer cervicis). In contrast, the slow fibers were composed of at least three slow types, which were comparable to the isoforms of the different myosins in β1 and β2 skeletal fibers.

In the dilator muscle, the oblique system was uniquely composed of fast oxidative fibers. The radial system was predominantly composed of slow fibers with isoforms of myosins different from the slow fibers of the sphincter and control muscles.

Ultrastructural features (width of Z bands, extension of the sarcoplasmic reticulum and SR‐T tubule junctions, and number of mitochondria) confirm the histochemical and immunohistochemical assessments of fiber types, even if some peculiar aspects in several fibers were observed. Smooth muscle cells separated from striated fibers were evident at the pupillary margin. The hypothesis of a mesenchymal origin for all irideal striated muscles is discussed.
Ultrastructural characteristics of sustentacular cells in control and odorant‐treated olfactory mucosae of the salamander
Authors: Zielinski Barbara S. , Getchell Marilyn L. , Getchell Thomas V.
Published: February 2005

The ultrastructural characteristics of five morphologically distinct regions of sustentacular cells in the salamander olfactory mucosa are described. 1) The apical region was characterized by a microvillar surface that lay below the level of the olfactory knob of olfactory receptor neurons and contained endosome‐like vesicles and a filamentous array at the level of the zonula adherens. 2) The supranuclear region contained rough and smooth endoplasmic reticulum, a Golgi complex, and secretory vesicles. Few sustentacular cells showed morphological signs of secretion, suggesting a low rate of baseline secretory activity. 3) The nuclear region contained the cylindrical nucleus surrounded by a thin band of cytoplasm containing bundles of filaments. 4) The central stalk contained filamentous arrays, Golgi‐like cisternae, multivesicular bodies, and peroxisomes. Cytoplasmic veils that extended from the central stalk contained filamentous aggregates. 5) The basilar expansion had a complex series of lateral and basal folds. The lateral folds enveloped extracellular material and nonmyelinated axons of the receptor neurons. The basal folds formed complex interdigitations with the basal lamina, particularly in regions occupied by blood vessels and the acini of Bowman's glands in the subjacent lamina propria. These characteristics, and the presence of endosome‐like vesicles and mitochondria, suggest that the basilar expansion is metabolically active and participates in cellular transport of material. Treatment with the odorant 2‐isobutyl‐3‐methoxypyrazine caused ultrastructural changes in the apical and supranuclear regions that were associated with secretion and in the basilar expansion region that were indicative of an increase in metabolic and transport activity.
H+‐K+‐ATPase activity in the rat incisor enamel organ during enamel formation
Authors: Sasaki Takahisa , Tadokoro Katsumi , Yanagisawa Takaaki , Higashi Shohei , Garant Philias R.
Published: February 2005

The enamel organ of growing rat incisors was perfusion‐fixed with a mixture of formaldehyde and glutaraldehyde and processed for ultracytochemical demonstration of ouabain‐resistant, K+ ‐stimulated p‐nitrophenylphosphatase representing the second dephosphoylative step of H‐K‐ATPase by use of the one‐step lead method. Throughout the stages of amelogenesis, the enzymatic activity was found in the plasma membranes, mitochondrial membranes, and lysosomal structures of the cells of stratum intermedium, papillary layer, and ameloblast layer. Gap junctions and desmosomes between these cells were, however, free of reaction product or showed slight precipitates of reaction. The stellate reticulum and the outer enamel epithelium at the stage of enamel secretion were usually negative for reaction. Although secretory, transition, and ruffle‐ended maturation ameloblasts showed enzymatic activity at their basolateral cell surfaces, their distal cell surfaces facing the enamel were always free of reaction product. On the other hand, the smooth‐ended maturation ameloblasts seldom showed a positive reaction, except in lysosomes and along their basal cell surfaces. An energy‐dispersive X‐ray microanalysis of reaction products of H‐K‐ATPase in unosmicated tissue sections demonstrated that they were composed of lead and phosphorus, which had been released during the dephosphorylation of substrate. In cytochemical controls, the enzymatic activity was completely dependent on substrate and potassium ion, resistant to ouabain and levamisole, and inhibited by nelinium bromide, a specific inhibitor of H‐K‐ATPase. In addition, inorganic trimetaphosphatase as enzymatic marker of lysosome was localized in dark and pale lysosomes, phagosomes, multivesicular bodies, and ferritin‐containing vesicles of the ameloblasts and the cells of stratum intermedium and papillary layer. These membrane‐bound structures were also positive for H‐K‐ATPase reaction. These results suggest that: 1) H‐K‐ATPase functions to maintain an acidic internal pH of lysosomes in the enamel organ cells; and 2) H‐K‐ATPase localization in the plasma membranes of enamel organ cells is concerned with efflux of protons derived from cytoplasmic water.
Survival of satellie cells in whole muscle transplants
Authors: Schulitz Edward , Albright David J. , Jaryszak Debra L. , David Tracy L.
Published: February 2005

The ability of satellite cells to survive the ischemic conditions at the core of orthotopically free grafted rat extensor digitorum longus muscles was examined. Cell cultures of isolated core and peripheral regions of whole muscle grafts maintained in vivo for more than 24 hours indicated that no viable cells were present in the core, whereas the number of cells from the peripheral region was greatly increased. Muscles were examined with the electron microscope to determine the fate of satellite cells of the core at various times after transplantation. The population of satellite cells in the core was reduced beginning at 18 hours and had virtually disappeared by 24–28 hours. This reduction did not appear to be the result of satellite cell death. Although there was abundant morphological evidence that myonuclei as well as myofiber cytoplasmic organelles were degenerating, there was little indication of satellite cell death in situ at any time period studied. These studies suggest that satellite cells cannot survive, but migrate from the ischemic core to more peripheral regions of whole muscle transplants. In addition, they suggest that migration is an important aspect of the regeneration response in the free graft system and permits the myogenic population to contribute en masse to the centripetal wave of regeneration from the time it is initiated at the muscle periphery.
Embryological development and prevalence of thumb flexion creases
Authors: Kimura Sumiko , Schaumann Blanka
Published: February 2005

A study of the embryological development and morphology of the thumb flexion creases is presented. We used 178 human fetuses, at 6–20 weeks of gestational age, and 225 normal adults, aged 19–81 years, to observe the morphology and the timing and location of the appearance of the flexion creases. Most creases, that is, the regular, extra, and oblique creases, were found to develop concurrently with the appearance of the fetal volar pads, apparently independently of the thumb flexion movements. Although the regular creases usually appear to be simple, single creases, they seem to be formed by the radial and ulnar lateral crease segments that develop inwards from each lateral side. Our observations also suggest that the oblique and extra creases on the proximal phalanx of the thumb should be considered as common or “regular” creases, rather than anomalies, because of their high freqency in fetuses and in normal healthy adults.
Lifetime of the osteoblast in mouse periodontium
Authors: McCulloch C. A. G. , Heersche J. N. M.
Published: February 2005

The kinetics of osteoblasts and osteocytes on appositional and resorptive surfaces of mouse alveolar bone were examined using 3H‐thymidine and 3H‐proline radioautography. Our results show that the osteoblasts at the appositional surface of the the mouse periodontium are recruited from a progenitor population in the G1 phase of the cell cycle that goes through a single S‐phase before differentiating into osteoblasts and that the active lifetime of the osteoblasts on the periodontal surface is approximately 20 days. The lifetime of the osteoblasts on periosteal and endosteal surfaces is 10 days. The active lifetime of an osteoblast appears to be independent of the amount of matrix produced.
Architecture and structure of canine veins with special reference to confluences
Authors: Stone Elizabeth A. , Stewart Gwendolyn J.
Published: February 2005

The occurrence of cell‐infiltrated intimal lesions at the confluence of many small tributaries with canine jugular and femoral veins suggested that these areas (confluences) might (1) differ structurally from the rest of the receiving vein and (2) serve as initiation sites for thrombi. To explore these possibilities, the number of tributaries was determined by careful blunt dissection, and the architecture of confluences was studied by light and scanning and transmission electron microscopy. In addition to confluences formed by a named tributary (omobrachial), canine jugular veins averaged 11 confluences formed with small (0.2 to 2.5 mm diameter) unnamed tributaries that had not been previously described. Femoral veins averaged eight confluences of which four were formed with small unnamed tributaries. Double‐leafed valves were found at 90% of jugular and 76% of femoral vein confluences. Previously such valves were described only at the confluence of superficial with deep leg veins. Corrosion casts of iliac, saphenous, azygous, costocervical, and maxillary veins as well as cranial and caudal vena cava demonstrated a similar pattern of tributaries and valves.

The three structures (receiving vein, tributary, valves) that formed the confluence differed, necessitating considerable modification as they approached the area of fusion. Jugular and femoral vein walls contained 5 to 10 layers of smooth muscle, abundant collagen, and a small amount of elastin. Tributary walls contained 0 to 2 discontinuous smooth muscle cell layers, limited collagen, and no elastin. As receiving veins approached a confluence, the thickness decreased by 15 to 77% except at valve attachment sites, which were thickened. A cluster of smooth muscle cells formed the junction of valve leaflets with vein. Endothelium was continuous over the luminal surface of all three structures. Calculations showed that these small‐valved tributaries make only a small contribution to venous return. On the other hand, there is considerable information to support the concept that local attenuation of the vein wall would lead to localized vessel dilation, resulting in rupture of the endothelium and basement membrane.
Development of the pulmonary vein in the american alligator (Alligator mississippiensis)
Authors: Kutsche Lynn M. , Van Mierop L. H. S.
Published: February 2005

The origin of the embryonic common pulmonary vein in terrestrial vertebrates is still uncertain. Most earlier studies in nonhuman embryos describe the vein as entering the sinus venosus. The currently prevailing view, however, based largely on the study of human material, is that the embryonic common pulmonary vein is associated with the left atrium from its inception.

We recently observed the pulmonary vein entering the sinus venous part of the right atrium in several normal dog embryos of a stage comparable to horizon XIV in man (Streeter: Contrib. Embryol. Carnegie Inst. Wash., 31:53, 1945). In slightly older specimens the vein entered the left atrium just to the left of septum primum. This observation, and the fact that some atrial septal and pulmonary venous anomalies in man still await a plausible pathogenetic explanation, stimulated a restudy of the origin of the vein. The alligator was used because we already had prepared a large number of closely graded serially sectioned embryos for other purposes. Wax plate reconstructions clearly showed that the common pulmonary vein entered the left side of the sinus venosus. With the formation of the atrial septum, this part of the sinus venosus is “pinched off” and becomes incorporated into the left atrium, thus transferring the pulmonary venous ostium to that atrium.
Bone cell populations and histomorphometric correlates to function
Authors: Simmons D. J. , Menton D. N. , Russell J. E. , Smith R. , Walker W. V.
Published: February 2005

A circadian context has been used to develop information about the proliferative and functional behavior of the cell populations that function to model the long bones of growing rats. We asked: Are the proliferating cells in the growth cartilages and diaphyseal bone of young adult growing rats distributed within single or multiple populations? Can cytomorphometry (TEM‐C) be used to determine ultrastructural correlates to the well‐defined circadian rhythm of matrix formation displayed by functionally synchronous populations of metaphyseal osteoblasts? Can TEM‐C reveal changes in osteoclast ultrastructure that could index a biological rhythm for osteoclastic bone mineralysis/resorption? Kinetic results derived from multiple radiothymidine labeling (DNA synthesis) support the single population model for chondrocytes and disphyseal osteoprogenitor cells. TEM‐C studies at the midpoints of the daily light and dark spans show that osteoblast RER‐membrane development and cysternal volumes are maximal at the recorded daytime peak of net collagen synthesis. The extent of metaphyseal osteoclast surface ruffling (mineralysis) is also twofold greater during the day than the night—an observation supporting the concept that bone formation and resorption activities are coupled.
Surface modifications at the periosseous region of chick osteoclast as revealed by freeze‐substitution
Authors: Akisaka Toshitaka , Subita Gus Permana , Shigenaga Yoshio
Published: February 2005

Improved preservation of osteoclast fine structure can be achieved by quick freezing, freeze‐substitution, or detergent extraction. With such techniques the ruffled border mainly contains a disorganized, interconnected meshwork of microfilaments (5–7 nm in diameter), whereas in the clear zone a few ordered arrays of intermediate‐type filaments (10–12 nm in diameter) are detectable among the network of microfilaments. In well‐frozen samples, well‐preserved matrix may have occluded the cytoskeleton; detergent extraction permits visualization of the cytoskeletal components. In fresh‐frozen cells an extracellular fuzzy coat overlays the ruffled border. At the site of attachment of the clear zone to the bone surface, extracellular cementing material is detected only after quick freezing. The superiority of quick freezing to preserve ultrastructure is shown in various cytoplasmic organelles. Most vesicles and vecuoles found close to the ruffled border seemed not to make contact with the extracellular matrix. Anhydrous procedures using quick freezing and freezesubstitution stabilize bone mineral in some vacuoles and in the channels of the ruffled border.
Platelike and globelike inclusion bodies associated with rough endoplasmic reticulum in alveolar type 2 cells of the sheep
Authors: Shibamoto Toshishige , Kobayashi Toshio , Nagata Tetsuji
Published: February 2005

We studied the ultrastructure of alveolar type 2 cells of sheep. The inclusion bodies of rodlike structures or cisternal bodies derived from the endoplasmic reticulum were found in 13.6 ± 7.0% (± SD) of type 2 cells. The length of the Rod‐like structures were usually straight and arranged in parallel stacks. An electron‐dense line ran longitudinally at the center of the rodlike structures. Serial ultrathin sections revealed that the rodlike structures did not seem to be threedimensionally rod‐shaped structures but were actually plate‐disc or cup‐shaped, and the piled‐up rodlike structures were connected to each other at their ends. This rodlike structure in type 2 cells of sheep seems rather to be a platelike inclusion body. The cisternal body, on the other hand, was circular or oval‐shaped cisternae containing aggregated electron‐dense materials distributed in an arabesque or speckled pattern. Serial ultrathin section examination revealed the cisternal body to be three‐dimensionally a globe. Some plate bodies were arranged near the cisternal body, suggesting the transformation from the latter to the former. The functional significance of these findings has not yet been elucidated.
Distribution of fibronectins and laminin in the early pig embryo
Authors: Richoux Véronique , Darribère Thierry , Boucaut Jean‐Claude , Flèchon Jacques‐Edmond , Thiery Jean‐Paul
Published: February 2005

Fibronectins (FN) and laminin (LN) distributions were studied in the pig embryo by indirect immunofluorescence using antiporcine FN and antimurine LN antibodies.

Extracellular FN are first detected in the early blastocyst before endodermal cell migration. They appear between the cells and on the blastocoelic face of the inner cell mass; thus, they are located at the interface of the trophectoderm and extraembryonic endoderm. Mesodermal cells migrate in a tridimensional network of fibrillar FN. These glycoproteins are also in the extraembryonic membranes (chorion and yolk sac wall) contiguous to the FN‐rich basement membranes of embryonic ectoderm and endoderm.

Extracellular LN appears in the blastocyst when the endoderm is already established as a continuous cellular monolayer, and is located between the trophectoderm and the extraembryonic endoderm, which produces it. Laminin also accumulates at the basal surface of the embryonic ectoderm at the onset of gastrulation. In the extraembryonic membranes, LN appears at the interface of the endoderm and mesoderm and at the interface of the trophectoderm and mesoderm. It is produced and secreted by extraembryonic mesodermal cells.

Analysis of the distribution of these glycoproteins suggests that FN allow the migration of endodermal and mesodermal cells by providing them with a suitable substrate. When these cells become immobilized, they synthesize LN, probably to stabilize their interactions with the underlying extracellular material and epithelia.
Perisynaptic satellite cells in human external intercostal muscle: A quantitative and qualitative study
Authors: Wokke J. H. J. , van Den Oord C. J. M. , Leppink G. J. , Jennekens F. G. I.
Published: February 2005

It is not known whether or not satellite cell nuclei are more common in the vicinity of motor endplates than in extrasynaptic regions of human muscle, as in animals. If so, perisynaptic satellite cells may have a role in preserving neuromuscular function. We compared the frequencies of satellite cell nuclei and of myonuclei in perisynaptic and extrasynaptic regions of human external intercostal muscle, and found an absolute as well as a relative increase of perisynaptic satellite cells. The mean frequency of satellite cell nuclei per sarcomere was 0.016 in perisynaptic and 0.00003 in extrasynaptic regions. The mean frequency of myonuclei per sarcomere was 0.098 in perisynaptic and 0.014 in extrasynaptic regions. We could not demonstrate any influence of aging on satellite cell distribution. Perisynaptic satellite cells had many processes, and some features suggested a more active state. These cells might add to the pool of junctional myonuclei for synthesis of acetylcholine‐receptor molecules or help in the repair of the postsynaptic membrane. Alternatively, they may synthesize basal lamina substances that are specific for the endplate.
Glycoconjugates in normal wound tissue matrices during the initiation phase of limb regeneration in adult Ambystoma
Authors: Young Henry E. , Dalley Bernell K. , Markwald Roger R.
Published: February 2005

The present study identifies localizes, and reports the relative composition of specific glycosaminoglycans within tissue matrices during the initiation phase of limb regeneration. The regenerate tissues were harvested and assayed morphologically, histochemically, and chemically. We observe 1) a population of cells interspersed among the cells of the dermis, epimysium, perimysium, perichondrium, and periosteum. 2) This population was distinguishable by a unique pattern of glycoproteins and extracellularly associated hyaluronate and glycoproteins. 3) Cells with these staining characteristics aggregated to a position directly beneath the apical epicermal cap. 4) Extracellular hyaluronate and glycoproteins colocalized with undifferentiated tissues. And 5) extracellular chondroitin sulfate, dermatan sulfate, and keratan sulfate glycosaminoglycans colocalized with differentiated tisues. The correlations of distinct glycoconjugate compositions with specific regeneration morphologies suggest the possibility that these components may be related to the phenotypic expression of tissues during regeneration.
Progesterone promotes a massive infiltration of the rat uterine cervix by the eosinophilic polymorphonuclear leukocytes
Authors: Luque Enrique H. , Montes Gregorio S.
Published: February 2005

Rat uterine cervices contained an eosinophilic infiltrate during labor, whereas samples of cervices obtained from nonpregnant controls had no infiltrate. A heavy eosinophilic invasion, which closely resembled that of the cervix uteri at term, could be reproduced in ovariectomized rats following progesterone administration, but not in spayed rats injected with estrogen. Light and electron microscopic evidence showing a widespread collagenolysis in the cervical stroma at term is presented. This collagenolysis follows the eosinophilic invasion. On the basis of these observations, a possible role for the eosinophilic infiltrate of the uterine cervix is discussed.
Primary cell culture and morphological characterization of ventricular myocytes from the adult newt, notophthalmus viridescens
Authors: Tate John M. , Oberpriller John O.
Published: February 2005

Previous work has demonstrated that adult newt cardiac myocytes possess a proliferative ability in response to an experimentally induced in jury, in vivo. This study describes an in vitro model in which the proliferative events of the adult cardiac myoctye may be studied. Ventricles were minced and then enzymatically dissociated in a Ca++‐ and MG++‐free salt solution containing 0.5% trypsin and 625 U/ml of CLS II collagenase for 8 to 10 hours at 25°C. Enzyme digests were preplated and then cultured on bovine corneal endothelial‐derived basement membrane “carpets” in either serum‐free or serumsupplemented modified Leibovitz's medium for up to 30 days. Light and transmission electron microscopic characterization demonstrated that a majority of the myocytes underwent an initial period of disorganization characterized by a “rounding up” of the cell and a loss of myofibrillar organization. Once the myocytes had attached to the culture substratum they began to spread out, underwent a reassembly of their contractile elements, resumed spontaneous contractions, and demonstrated ultrastructural evidence of protein synthesis. Mitosis was observed in several myocytes 8 to 15 days following isolation. In 15‐day serum‐supplemented and serum‐free cultures, 6.5% ± 0.9% and 8.1% ± 1.4% of the myocytes were binucleated, respectively. These results demonstrate that adult newt ventricular myocytes can be successfully placed into primary culture and are capable of undergoing mitosis. This work may be considered as a foundation for future investigations which will focus on the mechanisms which control cardiac myocyte proliferation.
Synthesis and secretion of collagen by cells of connective tissue, bone, and dentin
Authors: Leblond C. P.
Published: February 2005

The production of type I collagen by fibroblasts, odontoblasts, and osteoblasts is reviewed on the basis of results obtained by electron microscopy, 3H‐proline radioautography, and immunostaining for type I procollagen.

In the three cell types, the percursors of type I collagen are processed along the rough endocplasmic reticulum (rER)‐Golgic‐secretory granule pathway in the same manner as secretory proteins, but the available evidence suggests a few special features: (1) From the rER site of synthesis, the initial collagen procursors, known as pro‐alpha chains, are transported to the Golgi apparatus within tubular structures, referred to as intermediate tubules, rather than within vesicles. (2) The pro‐alpha chains coil into a triple helix within spherical distensions present along the saccules on the cis side of Golgi stacks. (3) The resulting procollagens are fairly raigid and form bundles that cause spherical distensions to lengthen into cylindrical ones, whereas by an unknown mechanism these distensions become part of the saccules on the trans‐side of Golgi stacks. (4) The procollagen‐containing cylindrical distensions are resleased from trans‐saccules to become secretory granules, and some procollagen material finds its way into lysosomes. (5) The secretory granules release their procollagen content by exocytosis at the cell surface. (6) The released procollagen is transformed into collagen before or, more probably, after associating with the surface of a collagen fibril.
Role of lipids in calcification of cartilage
Authors: Boyan Barbara D. , Schwartz Zvi , Swain Larry D. , Khare Aruna
Published: February 2005

This review addresses the role of lipids and membranes in biologic calcification and examines their regulation during endochondral ossification. The close association of lipids with mineral deposition has been well established. Early observations indicated that lipids, particularly phospholipids, can not be totally extracted from calcified tissues until the tissues are decalcified. Phospholipids associated with mineral are also enriched in extracellular membrane vesicles, called matrix vesicles. Numerous studies indicate that mineral deposits in calcifying cartilage are first seen in these phosphatidylserine and alkaline phosphatase enriched vesicles and that the process of endochondral calcification of epiphyseal growth plate is possibly mediated by them. Matrix vesicles, and the phospholipids present in them, appear to be involved in initial formation of calcium hydroxyapatite crystals via the interaction of calcium and phosphate ions with phosphatidylserine to form phospholipid:Ca:Pi complexes (CPLX). CPLX is present in tissues which are undergoing initial mineral deposition but are absent from nonmineralizing tissues. Evidence suggests that CPLX resides in the interior of matrix vesicles where the earliest mineral crystals are formed in association with the vesicle membrane. More recently, it has been determined that specific membrane proteins, called proteolipids, participate in CPLX formation and hydroxyapatite deposition, in part by structuring phosphatidylserine in an appropriate conformation. Phosphatidylserine involvement in the initiation of mineralization has been extensively investigated because of its extremely high binding affinity for Ca2+. In addition to structuring a specific phospholipid environment, proteolipids may also act as ionophores, promoting export of protons and import of calcium and phosphate, both requirements of biologic calcification. In cartilage, enzyme activity, phospholipid and CPLX content and composition, and ability of proteolipids to support in vitro hydroxyapatite formation, are all part of the initial calcification cascade and are regulated by metabolites of vitamin D.
Organization of crystals in enamel
Authors: Warshawsky H.
Published: February 2005

It has been variously suggested that the organic matrix associated with the mineral phase of enamel is present as either calcified fibrils, central dark lines, peripheral sheaths around hexagonal crystals, or organic ghosts apparently contained within crystal profiles. The most consistent findings confirm the crystal ghost conception. Grid decalcification of nearly mature sectioned enamel and staining revealed hollow, noncrystalline structures whose external measurements were statistically identical to those of the dissolved crystallites, but with internal measurements too small to accommodate the crystallites. To explain these apparent ghosts in view of the incompatibility of ghosts with crystal structure, it has been proposed that the crystallites are not hexagonal in cross‐sections and the hexagonal appearance is due to projections of parallelepiped‐shaped crystallite segments with cut surfaces that are rhombiodal in shape. Material on the surface of such profiles would project as if it were contained within the profile. Hexagonal forms could not be demonstrated in isolated crystallites examined by transmission electron microscopy, high‐resolution scanning electron microscopy, and replicas made of the isolated crystallite preparations examined by transmission electron microscopy. Existing evidence does not rule out the possibility that the noncrystalline profiles represent stain drawn into the holes left by the dissolved crystallites as a result of high capillarity forces.
Morphometric analysis of bone marrow sinus cell elements after induction of monomyelocytic leukemia in BALB/c mice
Authors: Leonardi Gary Paul , Manthos Michael , Orlic Donald , Lobue Joseph
Published: February 2005

Morphometric measurements of bone marrow sinus wall adventitial and endothelial cells were made in normal and leukemic samples by using a Bioquant II computer image analysis program (R & M Biometrics, Nashville TN). Electron micrographs of bone marrow from at least eight mice per group were studied in normal and day‐2, day‐4, and day‐6 leukemic postinoculation groups. The adventitial cells abuting the sinus endothelium was found to be significantly reduced with disease progression. In addition, adventitial cell area and perimeter were found to be drastically reduced with disease progression whereas endothelial cell area and perimeter showed no significant differences. Other investigators have suggested that the marrow sinus adventitial cell cover is drastically reduced in rodent leukemias (Chen et al.; Blood, 39:99–112, 1972; Campbell; Am. J. Anat., 142:319–334, 1975). Our findings give quantitative data to support this hypothesis.
Atrioventricular node and input pathways: A correlated gross anatomical and histological study of the canine atrioventricular junctional region
Authors: Racker Darlene K.
Published: February 2005

To determine the architecture of the atrioventricular (AV) junctional region, structures in atrial preparations were correlated to those in serial sections made either parallel or perpendicular to the long axis of the AV node (AVN)/AV bundle complex. The results demonstrated the following for the first time: (1) A right medial atrial wall (MAW) extends anteriorly from the interatrial septum, superior to the interventricular septum (IVS). (2) An atrial interventricular septum (A‐IVS) groove is located between the base of the MAW and the crest of the IVS. (3) Three atrionodal bundles converge to form a proximal AV bundle (PAVB), which in turn is contiguous with the AVN. The atrionodal bundles are associated with the MAW or the superomedial and inferolateral margins of the coronory sinus. Terminal portions of the atrionodal bundles and the PAVB reside within the A‐IVS groove. The AV bundle was termed distal (DAVB) to avoid confusion. (4) The location of the AVN/DAVB complex topographically is deep to the apex of the septal cusp of the tricuspid valve subjacent to the MAW. Intracardially, the AVN/DAVB complex is within the central fibrous body. Significantly, this study resulted in the first unequivocal demonstration of discrete bundles of myocardial fibers associated with the atrial end of the AV node. Moreover, it appears likely that the atrionodal AV bundles are continuous with the sinoatrial nodal extensions, thereby forming internodal tracts.
Three‐dimensional reconstruction of the myofiber pattern in the fetal and neonatal mouse heart
Authors: McLean Miriam , Alison Ross M. , Prothero John
Published: February 2005

A methodology for three‐dimensional reconstruction from serial sections and interactive computer graphics is described briefly. This methodology was applied to study the morphogenesis of the cardiac myofiber pattern in the fetal and neonatal mouse heart (ventricles). Few organized in‐plane myofibers were found in the myocardial wall before 12 days postconception, but many fibers were observed in the very numerous trabeculae at all times up to birth. However, beginning at about 12 days, the number of fibers in the myocardial wall increases rapidly: these are seen predominantly in the transverse plane. The neonatal mouse heart, especially the left ventricle, resembles a small adult muscular artery. But the global myofiber pattern in the mouse heart at these stages appears to be more complex than might be inferred from earlier studies of the local myofiber pattern at a few sites in the ventricles of a few species of adult mammals. In particular, the pattern in and adjacent to the interventricular septum appears quite complex.
Jaw movements and muscle activity during mastication in growing rabbits
Authors: Weijs Wim A. , Brugman Peter , Grimbergen Cees A.
Published: February 2005

To investigate the biomechanical effects of juvenile growth changes in the rabbit masticatory apparatus a comparison was made of mastication in just‐weaned and adult animals. Mandibular movements in two planes were registered by cineradiography. Masticatory muscle activity was recorded by finewire electromyography. The same pattern of unilateral mastication was present in the two ages. The most important changes in the jaw movements are (1) a decrease of jaw opening speed and chewing frequency and an increase in jaw opening time, (2) a decrease in maximum gape in soft food and an unaltered gape in small‐particle hard food, and (3) an increase in lateral jaw excursion, mainly due to a more pronounced movement of the jaw to the balancing side (lingual phase). The contraction patterns were basically similar in the two ages. The higher chewing frequency in young animals was attained by a larger degree of overlap between opening and closing muscle activities. Young animals used relatively more EMG activity to chew hay, the hardest food. The changes in opening speed, gape, and chewing frequency are consistent with earlier predictions from the morphological changes, and so is the extra activity needed to chew hard food. The increase in lateral excursion was not predicted. It is suggested to be caused by cheek teeth wear, making possible smooth occlusal guidance of the jaw at the balancing side. Some of the changes in juvenile morphology can be viewed as adaptations to a changing diet.
Deformation‐corrected computer‐aided three‐dimensional reconstruction of immunohistochemically stained organs: Application to the rat heart during early organogenesis
Authors: Laan Alfons C. , Lamers Wouter H. , Huijsmans Dionysius P. , Kortschot Anita Te , Smith Jerry , Strackee Jan , Los Jan A.
Published: February 2005

The application of a computer‐assisted, three‐dimensional reconstruction procedure for serial sections to embryonic rat hearts during the period of cardiac looping and compartmentation is described. The procedure relies on immunohistochemical staining for the introduction of selective contrast and on episcopic and diascopic images of each of the sections for alignment and correction of compression due to sectioning. Episcopic (reference) images are taken from the embedding block just before the cutting of a slice and are still aligned and undeformed. Diascopic images are taken from the sections after immunohistochemical processing and, hence, contain selective contrast but are deformed and no longer aligned. The three‐dimensional images are visualized as shaded voxel models.

This approach allowed the unequivocal delineation of the developing myocardium and the inspection of its changing architecture both from the outside and from within. Furthermore, it allowed a quantification of myocardial volume. Because standardized and hence comparable views of three different stages were generated, changes in the shape of the cardiac loop, the atria, and the ventricles as well as changes in the position of the atrioventricular canal and interventricular foramen could be accurately described. Characteristic changes in the position of both the right ventricle and the atrioventricular canal that are essential for the formation of a correctly functioning four‐chambered heart could be observed. These changes in shape occur while the myocardial size increases dramatically.
Scanning electron microscope study of the morphology of the reptilian lung: The savanna monitor lizard varanus exanthematicus and the pancake tortoise malacochersus tornieri
Authors: Maina J. N. , Maloiy G. M. O. , Warui C. N. , Njogu E. K. , Kokwaro E. D.
Published: February 2005

The morphology of the langs of two reptilian species, Varanus exanthematicus and Malacochersus tornieri, have been studied on gross preparations, latex casts, and critical‐point‐dried tissues. The shape of these lungs was observed to conform with that of the body, the lung of the monitor lizard (Varanus) being long and ovoid while that of the pancake tortoise (Malacochersus) was rounded and laterally indented. With respect to the size distribution of the gas exchange compartments, the lungs were observed to be notably heterogenous. In both species these units were generally smaller in diameter in the cranial region of the lung while those in the caudal region were larger. The gas exchange compartments in the tortoise were more profusely compartemented with the primary, secondary, and tertiary septa being well developed white in the lizard only the primary and secondary septa were observed. The tertiary septa in the tortoise lung and the secondary septa in that of the monitor lizard defined the terminal gas exchange units, the favoli. The cast impressions closely resembled the actual lung tissue and convincingly revealed the hierarchical design of the gas exchange compartments as they radiate from the air chambers and ducts, terminally giving rise to the faveoli. This stratification clearly increases the surface area available for gas exchange in these lungs. Disparate refinements of the basic reptilian lung design, as noted here, may lead to differing anatomic pulmonary diffusing capacities for oxygen to which characteristics like energetics and mode of respiration in this taxon may be attributed.
Skeletal muscle in the diabetic mouse: Histochemical and morphometric analysis
Authors: Klueber Kathleen M. , Feczko John D. , Schmidt Gordon , Watkins John B.
Published: February 2005

Despite the extensive literature concerning the neuropathy associated with diabetes, only limited information describes changes in the associated muscle. The objective of this study was to evaluate the histochemical and morphometric characteristics of diabetic muscle in the C57BL/KsJ db‐m strain of mouse. The histochemical analysis of myofiber type for the diabetic mouse revealed that the extensor digitorum longus muscle consisted of 53.1% type 2a, 46.0% type 2b, and 0.9% type 1 myofibers, a significant shift from the percentages found in the nondiabetic litter mates (44.4% type 2a, 55.6% type 2b, no type 1). Computer‐assisted morphometric analysis of myofiber size by fiber type indicated a significant difference in myofiber size for the type 2b fibers in muscles from diabetic mice. Similarly, there was a shift in the fiber size distribution to include a greater number of small type 2b myofibers when compared to controls. Skeletal muscle from diabetic mice exhibited a significant change in the percentage of fiber types, with an increase in the number of type 2a fibers, a fiber type grouping that implies possible denervation and reinnervation, and a decrease in myofiber size. These findings may explain why some diabetic patients complain of muscle weakness.
Influence of epithelial‐mesenchymal interaction on the viability of facial mesenchyme in vitro
Authors: Saber Georges M. , Parker Susan B. , Minkoff Robert
Published: February 2005

Separation and recombination experiments, employing a variety of tissue configurations in organ culture, were performed to determine the extent to which the epithelium of the maxillary process influences the viability of the underlying mesenchyme during organogenesis. The results of these studies indicated that the viability of mesenchyme of the maxillary process of early stage embryos was severely impaired when separated from the overlying epithelium. The influence of epithelium on the viability of mesenchyme was stage dependent; that is, the requirement for the presence of epithelium for the maintenance of the viability of mesenchyme became progressively less pronounced at older developmental stages. The response of mesenchyme to the presence of recombined epithelium resulted in the appearance of a delimited zone of influence extending, within specific boundaries, from the epithelial‐mesenchymal interface. Preliminary data from homotypic (maxillary epithelium‐maxillary mesenchyme), heterotypic (limb apical ectodermal ridge—maxillary mesenchyme) and heterochronic (stage 28 epithelium‐stage 22 mesenchyme) recombination experiments indicated that viability of mesenchyme could be achieved only through direct epithelial‐mesenchymal contact which allowed restoration of normal morphological relationships at the interface of the two tissues.