bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Expression of Two Tadpole Stage Specific Myosin Heavy Chains in Xenopus laevis
Authors: Radice G.P.
Published: July 2008

Vertebrate skeletal muscles contain a family of myosin heavy chain (MyHC) proteins whose expression varies with clonal origin, developmental age, hormonal state, and innervation patterns. The number of MyHC genes and their regulation have been intensely studied in mammals and birds. However, comparatively little is known about MyHC expression in other vertebrates. To understand better MyHC regulation in amphibians, I have examined the fiber type expression of two tadpole stage-specific MyHC transcripts in Xenopus laevis. cDNAs for these transcripts, called MyHC E3 and MyHC E19, were used to synthesize digoxigenin labeled antisense RNA probes. In situ hybridization of these probes revealed that MyHC E3 was expressed throughout the myotome but was most abundant in the core fibers of the axial muscles, which are larval type II. In contrast, El9 was expressed most abundantly in the small diameter peripheral fibers of the axial muscles, which are larval type I. Transcripts of both genes were detected exclusively in skeletal muscle; neither heavy chain was expressed in cardiac muscle, smooth muscle, or lymph heart muscle. E3 expression was first detected at late gastrula in both segmented and unsegmented dorsal mesoderm. It remained abundant throughout premetamorphosis in myotomal muscle, and was also found in the levator hyoideus and mandibularis muscle of the head, and in abdominal wall muscles. In contrast, E19 was first detected at tailbud in the tail tip and its expression spread anteriorly among larval type I and type II fibers of the myotome and head muscles during the next few hours of development. The patterns of expression suggest that MyHC E3 is expressed predominately in larval type II fibers, and MyHC E19 is initially expressed predominately in larval type I fibers but as development proceeds is expressed in both type I and type II.
Spermatophagy in the Stallion Epididymis: A Scanning and Transmission Electron Microscopy Study
Authors: López Alvarez M.L. , Bustos Obregón E.
Published: July 2008

The occurrence of phagocytosis of spermatozoa in the epididymis is a controversial issue in male reproductive biology. In this paper we documented, by scanning and electron microscopy, the presence of spermatophages in the lumen of the proximal region of stallion epididymis. Sperm phagocytosis involving the principal cells that line the cauda epididymidis region was also observed. The possible meaning of this process in the removal of damaged, aged or surplus spermatozoa is discussed. These observations were made in samples obtained from random cases, during the course of research work carried out on the stallion male seminal duct system.
Stereological Analysis of the Urethra in Sexually Intact and Spayed Female Dogs
Authors: Augsburger H.R. , Cruz-Orive L.M.
Published: July 2008

The perfusion-fixed urethrae of 5 sexually intact nulliparous and 5 ovario-hysterectomized beagles were analyzed stereologically. Different urethral tissue components were estimated stereologically in each of the three proximal urethral quarters and compared between the two groups of dogs. Considerable individual variability within all groups was observed. In all the three urethral quarters considered, average smooth muscle and connective tissue volumes were generally lower in spayed than in intact animals, both in absolute and relative terms. However, only the difference between the mean relative volumes of urethral quarter I was statistically significant. In contrast, mean absolute and relative volumes of the vascular plexus were generally greater in the ovariohysterectomized dogs as compared to the animals of the other group – deviations in statistical relevance concerning the first urethral quarter were noted. Mean epithelial and striated muscle volumes did not vary essentially between the spayed and intact group of dogs. Despite the fact that all findings were not always statistically meaningful, our research nevertheless demonstrates that ovariohysterectomy decreases smooth muscle mass and connective tissue; it also elevates vascular plexus volumes in the urethra of spayed animals. Moreover, our results imply a general weakening of the urethral wall as a sequel to ovariohysterectomy, and this, in turn, could be seen to affect the closure mechanism of the urethra.
Electron-Microscopic Study of Gamma-Aminobutyric Acid Immunoreactivity in the Chief Cells of the Mouse Carotid Body
Authors: Oomori Y. , Ishikawa K. , Satoh Y. , Ono K.
Published: July 2008

The present study shows gamma-aminobutyric acid (GABA) immunoreactivity in almost all chief cells of the mouse carotid body. GABA immunoreaction products were distributed diffusely in the cytoplasm as well as in the dense-cored granules. These findings suggest that GABA may be localized in the cytoplasm and granules, and may be released from the cells.
Abnormal Spermatozoa in the Cauda epididymidis of Adult and Aged Hamsters (Mesocricetus auratus): A Study by Electron Microscopy
Authors: Calvo A. , Pastor L.M. , Gallego-Huidobro J. , Horn R. , Pallares J.
Published: July 2008

The morphology of the spermatozoa in the cauda epididymidis of 6- and 24-month-old (adult and aged) hamster was studied by electron microscopy. Lesions found in the spermatozoa included alterations in the acrosomal matrix and nuclear membranes, abnormal or absent mitochondria, alterations in the axonemes, dense fibres and microtubules, and bent flagella. All these abnormalities are similar to those found in other species and few alterations were exclusive to the older animals. Ultrastructurally abnormal spermatozoa were observed in both groups but were present at a significantly greater frequency in aged hamsters (p < 0.005). The percentage of sperm with abnormal acrosomes, mitochondria and dense fibres and of bent (but not disrupted) spermatozoa was significantly greater in the older animals. These results show that the ultrastructural alterations in hamster sperm are similar to those found in other mammals. Moreover, the percentage of ultrastructurally abnormal spermatozoa in aged hamsters is greater than 6-month-old hamsters, this increase is not accompanied by any new kinds of alteration.
A Scanning Electron-Microscopic Analysis of the Morphology of Equine Lower Lip Sinus Hair
Authors: von Rotz A. , Friess A.E.
Published: July 2008

Sinus hairs, which are tactile organs of most mammals, are differentiated into cavernous and sinus types. The horse has the cavernous type. Horse lower lips were perfused in diluted Karnovsky’s fixative and sinus hair processed for scanning electron microscopy. Anastomosing trabeculae of different thickness and shape originate from the internal connective tissue layer and extend to the external layer, thus forming a dense meshwork suspending the hair root like a net. However, many of the distal trabeculae do not reach the external wall of the blood sinus but end in a finger-like knob within the sinus, thus sharing some features of the sinus type. The sinus wall and trabeculae are completely covered by polygonal endothelial cells showing characteristically protruding nuclei, sparse microvilli and distinct cell borders. Endothelial cells on the trabeculae are more elongated. Openings of small blood vessels were found exclusively on the internal wall, indicating that blood exchange occurs via the internal wall only and that turnover of blood may be minimal. The supposed significance and function of the finger-like trabeculae in the distal part of the blood sinus lying close to the majority of nerve terminals is discussed.
Three-Dimensional Structure of the Sarcoplasmic Reticulum at the Neuromuscular Junctions of the Rat Diaphragm
Authors: Segretain D.
Published: July 2008

The three-dimensional structure of the sarcoplasmic reticulum at the neuromuscular junctions of the rat diaphragm was investigated by means of a selective staining technique allowing studies of thick sections combined with stereoscopic observations. The sarcoplasmic reticulum (SR) has different organizations related to the various regions of the postsynaptic cytoplasm. At the base of the membranous folds or deep region, flattened cisternae are smaller and connected by numerous anastomosed tubules. In the mitochondria-rich region, the SR is composed of large flattened cisternae. Between the postsynaptic folds, the SR is formed of poorly anastomosed thin tubes which give rise to single tubules running close to the plasmalemma. The SR is also associated with the Golgi apparatus present in the deeper mitochondria-rich region. This specific organization of the SR in the postsynaptic cytoplasm of the neuromuscular junctions might, like the Golgi apparatus, be involved in the synthesis of some specific proteins, enzymes and receptors.
Biphalangeal and Triphalangeal Toes in the Evolution of the Human Foot
Authors: Le Minor J.M.
Published: July 2008

The number of phalanges of the human toes was investigated in a series of 2,550 radiographs. Classical triphalangia of the lateral toes (2-5) was observed in 1,440 cases (56.47%). Biphalangeal disposition was observed for the 5th toe in 1,110 cases (41.02%), for the 4th toe in 64 cases (2.51%), for the 3rd toe in 5 cases (0.20%), and for the 2nd toe in 3 cases (0.12%). The frequency of bipha-langia of a given toe was not independent of the others. Biphalangeal toes result primarily from the absence of development of the distal interphalangeal joint. Biphalangia of the toes is a derived character which is restricted, within primates, to the human species, in relation to the reduction of the toes in adaptation to bipedalism.
Extracellular Matrix and Adhesive Molecules in the Early Development of the Gut and Its Innervation in Normal and Spotting Lethal Rat Embryos
Authors: Newgreen D.F. , Hartley L.
Published: July 2008

The distribution of fibronectin (FN), laminin (LM), Jl/tenascin, chondroitin sulphate proteoglycan (CSPG), neural cell adhesion molecule (NCAM), neurofilament (NF) and the HNK-1 epitope were studied immunohistochemically in the developing mid- and hindgut of E12.5-E16.5 rat embryos. Over this period the gut wall changed from a uniform mesenchyme to an annular organisation. FN and LM remained widely distributed, but Jl/tenascin became concentrated in mesenchyme outside the nascent circular muscle layer, and CSPG declined in, and NCAM increased in, the circular layer. Protease and fixation treatments suggested that CSPG could mask other molecules such as LM. This re-organisation proceeded bidirectionally, as a rostrocaudal wave which was met in the colon by a caudorostral wave. The caecum, however, was conspiciously delayed in all maturation events and also showed mesenchymal and serosal epithelial labelling for the cell-adhesion-related HNK-1 epitope, which was absent elsewhere. This period also covered the appearance of enteric neurons, recognised by HNK-1 and NF antibodies. Cells labelled by these antibodies appeared in a unidirectional rostrocaudal wave, from the duodenum at El2.5 to the rectum at El6.5. This wave was not in exact synchrony with the wave of intestinal maturation, but lagged behind so that neuronal cells first appeared in increasingly mature micro-environment at progressively more caudal levels. These cells initially were positioned imprecisely about mid-way across the gut mesenchyme layer and were not clearly related spatiotemporally to any of the above molecules. Slightly later, however, this neural region was broadly defined by relatively low levels of both CSPG and Jl/tenascin. The final position of the myenteric neurons was very precise, and was related to a thin Jl/tenascin layer and to a step in NCAM labelling intensity. Litters of pups, of which 25% would be expected to be spotting lethal homozygous embryos which develop total colonic and caecal aganglionosis, showed no difference in any of the molecules studied, but in 4 embryos out of 12, the progress of the rostrocaudal wave of neuron appearance was distinctly slowed even in the duodenum and proximal small intestine, regions well outside the final aganglionic zone. The observations suggest that this Hirschsprung’s-disease-like regionalised defect is a result of a generalised abnormality which does not involve gross changes in extracellular matrix and NCAM expression.
Gap Junctions between Mast Cells and Fibroblasts in the Developing Avian Eye
Authors: Oliani S.M. , Girol A.P. , Smith R.L.
Published: July 2008

Mast cells are present in the eye of chick embryos from the 14th day onward, displaying metachromatic granules, mainly in the iris anterior surface and pectinate ligament. Ultrastructurally these cells show electron-dense granules and a few thin and short cytoplasmic projections in close contact with fibroblasts. Sometimes these contacts are extensive, with long fibroblast projections partially involving the mast cells. Gap junctions between mast cells and fibroblasts are observed only in the eyes of 16- and 20-day-old embryos. These intercellular specializations are represented by a close apposition of cytoplasmic membranes with an extension up to 300 nm. Gap junctions between mast cells and fibroblasts were not observed previously in vivo or in vitro, although in vitro studies have shown that a number of functionally critical interactions may occur between these cells. Our morphological findings suggest that, in vivo, fibroblasts interact with mast cells and may influence their maturation.
Behavior of the Basement Membrane during Carcinoma Cell Invasion in Chemically Induced Carcinomas of the Skin
Authors: Köpf-Maier P. , Flug M.
Published: July 2008

Immunohistochemical localizations of the intrinsic basal lamina (BL) components laminin-1 and type IV collagen, the adhesion molecules type VII collagen and laminin receptor (a6p, integrin), and the type IV collagenase (72 kDa, MMP2) were analyzed in carcinomas of the mouse skin which were chemically induced by benzo[a]pyrene with or without the addition of the promotor phorbol 12-myristate 13-acetate. Normal skin, dysplastic lesions, and invasive carcinomas were investigated by histological and immunohistochemical (immunofluorescence and APAAP) methods. A regular and continuous staining of laminin-1 and type IV collagen was present in the normal skin and in areas of slight and moderate dysplasia. Underneath highly dysplastic epithelium, the BL became thin, loosened and sometimes disrupted, and accumulations of globular BL material were found in the connective tissue underneath the BL. Type VII collagen retained a more linear, continuous and uniform distribution in the areas of progressed epithelial dysplasia. All invasive carcinomas were characterized by a BL which was disrupted by gaps of varying size but, again, showed a more uniform and less discontinuous distribution of the anchoring molecule type VII collagen. Expression of the integrin laminin receptor investigated increased quantitatively in dysplastic lesions and in areas of invasive carcinomas, showing a circular presence at the surface of most epithelial cells of the basal and spinous layers of the epidermis, whereas, in the normal skin, the laminin receptor was polarized to the basal and lateral cell membrane of basal epithelial cells in contact with the BL. These results suggest that the discontinuities occurring in the BL during carcinoma cell invasion are not caused by a local loss of the anchoring molecules type VII collagen and/or laminin receptor, though alterations in the pattern of expression of the laminin receptor document fundamental changes in the cellular organization occurring during malignant transformation. On the other hand, the presence of the type IV collagenase increased in epithelial dysplasias and invasive carcinomas. In many dysplastic lesions, it was deposited in a plaque-like and sometimes linear manner near the basement membrane (BM) region indicating that, in chemically induced carcinomas, this enzyme may be involved in the process of BM perforation during carcinoma cell invasion.
Ontogeny of the Rat Bladder: Smooth Muscle and Epithelial Differentiation
Authors: Baskin L.S. , Hayward S.W. , Young P.F. , Cunha G.R.
Published: July 2008

The sequential expression of smooth muscle and epithelial markers in the rat bladder has been defined. Smooth muscle differentiation, based on cell morphology and immunohistochemical localization of smooth muscle oc-actin, myosin, vinculin, desmin, vimentin and laminin, begins at 16 days of gestation (birth = 22 days) in the rat bladder. Smooth muscle cell differentiation begins in the periphery of the bladder mesenchyme immediately subadjacent to the serosa and continues toward the urothelium. The cytokeratins 5, 7, 8, 14, 18, and 19 are expressed in the bladder epithelium as a function of developmental age with cytokeratin 7, 8, 18, and 19 being coexpressed at 15 days’ gestation followed by cytokeratin 5 at 17 days’ gestation and cytokeratin 14 in the newborn bladder. An understanding of the ontogeny of both smooth muscle and epithelial differentiation markers in the normal bladder will allow us to study events that occur in the diseased bladder.
Axotomy Induces Retraction of the Dendritic Arbor of Adult Rat Rubrospinal Neurons
Authors: Tseng G.F. , Hu M.-E.
Published: July 2008

The effect of distal axonal injury on the soma-dendritic morphology of intrinsic central neurons was examined using adult rat lumbar spinal cord-projecting rubrospinal neurons as a model. The soma-dendritic morphology was revealed using an improved Golgi-aldehyde method. Impregnated neurons were reconstructed in the two-dimensional plane for analysis. Four weeks after axotomy, neurons had reduced soma sizes and remained multipolar in shape. Some dendrites were found to end not far from their cell bodies. In addition, no long dendrite was identified following axotomy. Sholl’s analysis [The Organization of the Cerebral Cortex. London, Methuen, 1956] revealed that axotomized neurons had fewer dendritic branches than control neurons. Total dendritic length was also reduced. Subsequent analyses showed that the average number of dendritic trunks was not altered however the mean number of terminal branches per dendritic trunk was reduced. The dendritic membrane of the normal neurons was usually smooth with occasional short protuberances on the proximal dendrites and spines on the distal dendrites, which did not change after axotomy. In control neurons, we identified an elaborate type of dendritic structures named dendritic appendage aggregates. These aggregates were located preferentially on terminal dendrites and were classified into three categories according to their complexity. The incidence of occurrence for these aggregates decreased following distal axotomy. These phenomena indicate that rat lumbar spinal cord-projecting rubrospinal neurons retract their distal dendrites in response to distal axotomy. The observed anatomic restructuring following axonal injury is likely to be accompanied by an alteration of afferents which normally synapse on distal dendrites.
The Lumbar Anterior Epidural Cavity: The Posterior Longitudinal Ligament, the Anterior Ligaments of the Dura Mater and the Anterior Internal Vertebral Venous Plexus
Authors: Plaisant O. , Sarrazin J.L. , Cosnard G. , Schill H. , Gillot C.
Published: July 2008

The contents of the anterior epidural cavity were studied to elucidate the relationship between veins, ligaments, and membranous formations. Anatomical, radiological and histological studies on human specimens after latex or gelatin/ gadolinium venous injection at the level of the lumbar spine show that the posterior longitudinal ligament is a cross-shaped formation which includes the septum, the superficial part extending into the intervertebral foramen and the anterior ligaments of the dura mater. The anterior epidural cavity contains two medial and two lateral spaces. The two medial cavities enclose anterior and medial venous plexuses, which together receive the basivertebral veins; the two lateral cavities receive the anterior longitudinal veins. Contents of the medial and lateral cavities pass freely between the two. The lateral cavity connects with the intervertebral canal and dorsally into the posterior epidural space.
Pulmonary Surfactant Migrates into the Alveolar Capillaries of Newborn Rats: An Immunoelectron Microscopic Study
Authors: Wasowicz M. , Kashima K. , Yokoyama S. , Nakayama I.
Published: July 2008

The goal of the present study was to elucidate the migration of surfactant-like material into the alveolar capillaries of newborn rats. The lungs of experimental animals were studied by ultrastructural techniques – standard electron microscopy as well as immunoelectron microscopy – using antibodies against synthetic polypeptide complementary to the noncollagenous part of surfactant protein A (SP-A). Antibodies exhibited specific reaction with native rat SP-A in Western blot and immunohistochemical analysis. Surfactant was observed in the alveolar space, type II pneumocytes, macrophages, type I pneumocytes, endothelial cells, the extracellular space of the alveolar septa and in the alveolar capillaries. Lamellar structures observed in all elements of the blood-air barrier as well as in the alveolar capillaries were stained positively with anti-SP-A antibodies. Transport of the pulmonary surfactant into the circulatory system was observed more frequently during the first 6-8 h of extrauterine life of newborn rats, although it was also seen in the blood vessels till 48 h after delivery. The results of our investigation suggest that clearance of surfactant via the circulatory system plays an important role in the early postnatal period.
Ultrastructure of the Organic Matrix of Embryonic Avian Bone after en bloc Reaction with Various Electron-Dense ‘Stains’
Authors: Bonucci E. , Silvestrini G.
Published: July 2008

The morphological distribution of noncollagenous proteins in bone matrix is poorly known, chiefly because their amount changes with the type of bone, and they are not easily recognizable under the electron microscope. The aim of this study was to obtain further ultrastructural data on these proteins and on their relationships with collagen fibrils and the calcification process. Specimens of woven bone from the upper metaphysis of the tibia of chick embryos were examined after en bloc treatment with acetone solution of KMn04, or aqueous or alcoholic solutions of phosphotungstic acid or uranyl acetate. Untreated specimens were used as controls. Untreated, decalcified, and decalcified and stained sections were examined. As expected, the results showed that the woven bone matrix of the chick embryo consists of irregularly oriented collagen fibrils which outline wide interfibrillary spaces. These contain calcification nodules at the calcification front and are full of irregularly oriented crystals in completely calcified matrix. These spaces contain greater than expected amounts of filamentous or granular organic structures (probably corresponding to noncollagenous proteins), which are in a close relationship with needle- and filament-like crystals. The collagen fibrils are calcified to a lower degree than the interfibrillary spaces, and often appear uncalcified, or decalcified, when the interfibrillary spaces do not. This suggests that either the former calcify after the latter, or the respective mineral phases differ in their degree of solubility, so that the decalcification of collagen fibrils precedes that of interfibrillary spaces. The results confirm that woven bone contains an amount of interfibrillar noncollagenous material greater than lamellar bone, and show that woven bone calcification occurs not only in and on collagen fibrils, but chiefly between them, in relationship with noncollagenous filamentous material.
Quantitative Study and Architecture of Nerves and Ganglia of the Rat Heart
Authors: de Souza R.R. , Gama E.F. , de Carvalho C.A.F. , Liberti E.A.
Published: July 2008

The cardiac plexus of the Wistar rat was investigated in whole-mount preparations of the atria by NADH-diaphorase staining and by the acetylcholinesterase (AChE) histochemical technique. The plexus lies over the muscular layer of the atria, dorsal to the muscle itself, in the connective tissue of the subepicardium. The plexus contains on average 975 ± 150 neurons, occurring singly or gathered in packed ganglia. The ganglia are found regularly in certain situations, namely, cranially to the pulmonary veins (44% of total); cranially and to the left of superior vena cava (10%); in the interatrial groove (21%); to the left of the left pulmonary vein (11%); caudally to the pulmonary veins (12%) and in the wall of the coronary sinus (1%). Ganglia are never found on the auricular appendages. For the histochemical demonstration of AChE, the ‘direct coloring’ copper ferrocyanide method was used. Extrinsic nerves enter the atria along the superior vena cava, along the pulmonary veins and along the coronary sinus, forming ganglion-containing plexuses. From specific sites of these plexuses, nerves proceed to the ganglia located to the left of the superior vena cava, to the ventral and dorsal ventricular wall and to the wall of the right atrium, where they form a delicate plexus accompanying the muscle fibers. Most of the neurons of the plexuses displayed AChE activity in the cytoplasm though they presented different reaction intensities. The distribution of cardiac nerves from groups of neurons located at discrete sites may indicate that postganglionic nerves selectively project to and thus control specific cardiac regions and/or functions.
Anatomical Relationship between Vagal Afferent Fibers and CCK-Immunoreactive Entero-Endocrine Cells in the Rat Small Intestinal Mucosa
Authors: Berthoud H.-R. , Patterson L.M.
Published: July 2008

There is evidence for a pathway involving small intestinal CCK-producing entero-endocrine cells and visceral afferent nerve fibers in signaling the effect of luminal nutrients on gastrointestinal and food intake regulation. In order to investigate the type of anatomical apposition that exists between CCK cells and vagal afferents, CCK immunocytochemistry was performed on tissue from rats whose vagal afferent fibers to the abdomen had previously been labeled in vivo by injecting the fluorescent carbocyanine dye Dil into the nodose ganglia. CCK immunoreactive (CCK-IR) cells were more abundant than vagal afferent fibers, but both were present throughout the small intestine as well as in crypts and villi. Few CCK-IR cells were in close (<5 um) anatomical contact with vagal afferent axons, and the latter did not produce suspicious terminal specializations near CCK-IR cells. Most labeled vagal afferent axons, which distributed strictly within the crypt and villous lamina propria, were at distances of tens to hundreds of microns to the nearest CCK-IR cell. These findings strongly support the idea that CCK released from entero-endocrine cells acts on vagal sensory fibers in a paracrine fashion, but do not rule out the presence of a few very close, neurocrine-like contacts or a humoral mode of action. Possible implications of such an arrangement on CCK-mediated satiety are discussed.
An Anatomical Analysis of the Relationships between the Intercostal Nerves and the Thoracic and Abdominal Muscles in Man. II. Detailed Analysis of Innervation of the Three Lateral Abdominal Muscles
Authors: Sakamoto H. , Akita K. , Sato T.
Published: July 2008

Minute dissection was performed in one male adult cadaver in order to elucidate the detailed distribution of muscular branches of intercostal nerves within the lateral abdominal muscles as well as the segmental relationships. In the obliquus internus and transversus abdominis, as well as in the upper half of the obliquus externus, each muscle fascicle receives the nerve of the corresponding segmental attachment to the rib. On the other hand, in the lower half, the obliquus externus abdominis receives a twig from the lower adjacent segmental nerve, because within the muscle the corresponding segmental nerve first runs horizontally and enters the upper adjacent fascicle before descending obliquely, parallel to the fiber direction.
Mesenchyme to Epithelium Transition during Development of the Mammalian Kidney Tubule
Authors: Davies J.A.
Published: July 2008

Kidney epithelia have two separate origins. Collecting ducts develop in the manner of most glandular organs, by growth and branching of a bud derived from a pre-existing epithelium. Excretory tubules develop by a direct mesenchyme to epithelium transition (MET), which is induced by the tips of the developing collecting duct system as it invades a specialised area of mesenchymal cells. The process by which these metanephrogenic mesenchyme cells achieve MET can be divided into several stages; induction, acquisition of stem cell character, fate determination, condensation, epitheliogenesis, polarisation and maturation. Progress through these stages is regulated by ‘checkpoints’ at which permission to proceed requires specific signals. The stages of development are characterised by the expression of new combinations of genes that code for transcription factors (Hox genes, Pax genes, zinc finger proteins), signalling effectors (growth factors, Wnts, receptor tyrosine kinases) and morphoregulatory molecules (CAMs, cadherins, extracellular matrix ligands). This review summarises current knowledge about the molecular interactions that control MET in the kidney, and also about how their failure might result in Wilms’ tumour, one of the most common cancers of childhood.
Epithelial-Mesenchymal Transitions in Cancer Progression
Authors: Birchmeier C. , Birchmeier W. , Brand-Saberi B.
Published: July 2008

Epithelial cells are the most important cell type in the development of human malignancies. More than 90% of all malignant tumors are carcinomas, and thus of epithelial origin. Aberrant growth and the ability to invade the underlying tissues are intrinsic properties of the fatally altered cells. Multiple genetic alterations that can influence growth and genetic stability of the carcinoma cells have been characterised during tumor progression. Loss of epithelial morphology and the acquisition of mesenchymal characteristics are typical for carcinoma cells late in tumor progression and correlate with metastatic potential. In vitro, epithelial-mesenchymal transitions can be induced by interference with the integrity of the adherens junction, by signalling via tyrosine kinases, and by oncogene expression. In carcinoma cells, loss or downregulation of E-cadherin expression are frequently observed in carcinomas, and correlate with the malignancy of the tumor. In general, this change in expression is regulated at the transcriptional level. However, tumor types or cell lines exist which show mesenchymal characteristics but nevertheless express E-cadherin protein or mRNA. A more-detailed analysis demonstrated that other mechanisms that interfere with E-cadherin-mediated cell adhesion can be operative. Mutations in the E-cadherin gene and loss or mutation of the second, intact copy as well as mutation in the catenin genes, which encode proteins that interact with the cytoplasmic portion of E-cadherin, can be observed. In addition, transient or unregulated phosphorylation by receptor tyrosine kinases or oncogenic tyrosine kinases, respectively, can interfere with the epithelial morphology and induce a mesenchymal conversion. Since tyrosine phosphorylation of β-catenin correlates with the epithelial-mesenchymal transition that is observed, E-cadherin-mediated cell adhesion might be modulated by such a mechanism. Interestingly, the same molecules implicated in the control of malignant properties turn out to play fundamental roles in the control of normal epithelial growth, differentiation and morphogenesis.
Thymic Nurse Cells: Entry of Exogenous Horseradish Peroxidase via a Transcytotic Route
Authors: Wiemann M. , Ehret G.
Published: July 2008

In order to address the question whether thymocytes inside thymic nurse cells (TNCs) are secluded against exogenous proteins, TNCs were isolated and kept in the presence of horseradish peroxidase. The distribution of horseradish peroxidase reaction product (HRP) within the TNCs was studied by light (LM) and electron microscopy (EM). Stained and unstained TNCs could be distinguished by LM. At the EM level, stained TNCs had a widened lumen and HRP lined the luminal surfaces. In unstained TNCs the lumen appeared normal and contained almost no HRP. In both types of TNCs the epithelial cell contained HRP in endosomes and, together with cellular debris, in larger vacuoles. Exocytosis of the latter was observed. Conglomerates of HRP were found inside the lumen and also within thymocytes. Data suggested that TNCs can shield secluded thymocytes against exogenous proteins except those which are provided by a transcytotic pathway. Such a pathway has not been demonstrated before in TNCs.
Study by Scanning Electron Microscopy of the Morphogenesis of Three Types of Lingual Papilla in the Mouse
Authors: Iwasaki S. , Yoshizawa H. , Kawahara I.
Published: July 2008

Tongues were removed from fetuses of mice on the 15th day of gestation (E15), from newborns (PO), from juveniles on the 7th day (P7) and on the 14th day (P14) after birth for examination by scanning electron microscopy. In the fetuses at E15, rudiments of fungiform papillae with a relatively regular, lattice-like pattern were visible on the anterior half of the dorsal surface of the tongue. The outline of the rudiment of a circumvallate papilla could be recognized on the median line between the lingual body and the lingual radix. No rudiments of filiform papillae could be seen. At PO, rudiments of filiform papillae were compactly distributed over the dorsal surface, as are the filiform papillae in the adult, their width was approximately one-third of that of fungiform papillae, and their tips were rounder than those of the filiform papillae in the adult. The fungiform papillae then increased in size and became somewhat irregular in shape. In juveniles at P7, the filiform papillae were long and slender, being relatively large on the intermolar eminence. A taste pore was visible in the center of each fungiform papilla at this stage. The shape of the circumvallate papilla was similar to that in the adult. In juveniles at P14, the shapes of all three types of papilla were almost the same as those in the adult. The rudiments of each of the three kinds of lingual papilla appeared at a different stage of development of mice; rudiments of the fungiform and circumvallate papillae, which are related to the sense of taste, were formed earlier than those of the filiform papillae, which are not involved in taste.
Immunohistochemical Changes in the Distribution of Nerve Fibers in the Periodontal Ligament during an Experimental Tooth Movement of the Rat Molar
Authors: Kato J. , Wakisaka S. , Kurisu K.
Published: July 2008

We examined the distribution of nerve fibers containing neurofilament protein (NFP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP) and neuropeptide Y (NPY) in the periodontal ligament (PDL) of the rat first molar. In addition, we observed changes in the distribution of these nerve fibers in the PDL during experimental tooth movement induced by insertion of a separating elastic. In normal animals, both NFP- and CGRP-containing nerve fibers were observed in the apical part of the PDL, smaller numbers being found in the cervical part in normal rats. They terminated as free nerve endings in the apical part; no specialized endings were observed. VIP- and NPY-containing nerve fibers were associated with blood vessels near the alveolar bone in the apical part of the PDL of normal animals. Three days after tooth movement, the number of NFP- and CGRP-containing nerve fibers increased in both stretched and compressed parts of the PDL, and returned to normal levels after 14 days. Immediately after tooth movement, VIP-containing nerve fibers disappeared in the stretched part, and returned to the normal level after 14 days. VIP-containing nerve fibers were always observed during tooth movement in the compressed part of the PDL. NPY-containing nerve fibers disappeared immediately after tooth movement in the stretched part and returned to the normal level after 3 days. NPY-containing nerve fibers were not observed 1 day after insertion of the elastic in the compressed part and were the same as in the normal controls after 14 days. These results suggest that NFP-, CGRP-, VIP- and NPY-containing nerve fibers in the PDL play important roles in the modulation of pain, tissue remodeling and blood flow regulation during tooth movement.
Study of the Arterial Pattern of the Rectum and Its Clinical Application
Authors: Shafik A. , Mostafa H.
Published: July 2008

The purpose of this communication was to study rectal arterial supply in order to characterize its various patterns and use them to help avoid rectal ischemic complications and, in addition, to explain some of the unknown rectal pathologic conditions. Thirty-two cadavers were studied. The pelvic organs were eviscerated. The rectal arteries were examined by direct dissection in 12 specimens and after injecting the inferior mesenteric artery with barium sulfate in 20 specimens. The superior rectal artery (SRA) and vein were found to be enclosed in a fibrous sheath which was connected to the posterior rectal surface by an anterior meso-rectum containing the ‘transverse rectal branches’, and to the sacrum by an avascular posterior mesorectum. Small lymph nodes were scattered alongside the anterior mesorectum. The SRA gave rise to 4 branches: transverse rectal, descending rectal, rectosigmoid and terminal. The transverse rectal arteries arose from the SRA in 24 specimens and from the descending rectal artery in 8. They were distributed to the upper half of the rectum. The rectosigmoid artery was distributed to the descending limb of the sigmoid colon and rectosigmoid junction. We found 2 terminal branches in 21/32 cadavers and 3 in 11/32. They communicated in the lower half of the rectum. The inferior rectal arteries were present in all the dissected cadavers while the middle rectal arteries could be identified in only 50% of the cadavers. Two arterial patterns were recognized: annular in the upper rectal half provided by the transverse rectal arteries and plexiform in the lower half supplied by the SRA terminal branches.
Migration of Enteric Neural Crest Cells in Relation to Growth of the Gut in Avian Embryos
Authors: Newgreen D.F. , Southwell B. , Hartley L. , Allan I.J.
Published: July 2008

Neural crest cell migration in the gut and the growth of the mid- and hindgut of avian embryos was investigated by a combination of whole-mount immunofluorescence of the HNK-1 neural crest marker epitope, chorioallantoic membrane grafting and morphometry. HNK-1-labelled cells advanced rostrocaudally in the gut of quail embryos (to the duodenum by stage HH 21 to the umbilicus by HH 25, to the ceca by HH 27, to the cloaca by HH 33). The timetable in chick embryos appeared to be slightly slower, but neural cells were obscured by background fluorescence in this species. More rostral regions of the gut commenced rapid growth earlier than more caudal regions (preumbilical small intestine after HH 26, postumbilical small intestine after HH 27 and colorectum after HH 28), and the small intestine and ceca grew most rapidly in length while the colorectum grew most rapidly in diameter. The rates of growth of the gut were low prior to the stage when HNK-1-labelled cells normally arrive in the small intestine, ceca and rostral colorectum, but increased dramatically after arrival. In the caudal colorectum rapid growth had commenced at the time of arrival of these cells. These data are consistent with the idea that a delay in arrival of vagal neural crest cells at any point in the intestine could jeopardize the ability of the cells to fully populate the remainder of the gut, due to the normal growth spurt causing the migration end-point to recede faster than the rate of neural crest cell migration. Thus, a mismatch in timing of neural crest cell migration and gut growth could play a role in the etiology of some forms of Hirschsprung’s disease.
Myocardial Bridging as a Factor in Heart Disorders: Critical Review and Hypothesis
Authors: Yamaguchi M. , Tangkawattana P. , Hamlin R.L.
Published: July 2008

The purpose of this report is to review the previous and current methods for the detection of a MB and to summarize results of work by other investigators as well as our own recent morphological studies with emphasis on work since 1983. We will discuss the presumable association of MBs with heart disorders, on the basis of significant publications. We describe the importance of both basic and clinical research for the assessment of MB influence in various heart disorders. Aspects covered are: (1) historical background of MBs and the relationship between the MB and CA; (2) general characteristics of MBs; (3) methods for studying MBs; (4) compressive effect of the MB on the CA; (5) clinical symptoms including myocardial ischemia, angina pectoris, myocardial infarction, development of atherosclerosis and thrombosis, ventricular fibrillation and sudden death; (6) treatment of MB-associated heart disorders by resection of MBs and (7) future research trends.
Protein Kinase G Phosphorylates Soluble Guanylyl Cyclase on Serine 64 and Inhibits Its Activity
Authors: Zhou Zongmin , Sayed Nazish , Pyriochou Anastasia , Roussos Charis , Fulton David , Beuve Annie , Papapetropoulos Andreas
Published: July 2008

Objective—Binding of nitric oxide (NO) to soluble guanylyl cyclase (sGC) leads to increased cGMP synthesis that activates cGMP-dependent protein kinase (PKG). Herein, we tested whether sGC activity is regulated by PKG.

Methods and Results—Overexpression of a constitutively active form of PKG (ΔPKG) stimulated32P incorporation into the α1 subunit. Serine to alanine mutation of putative sites revealed that Ser64 is the main phosphorylation site for PKG. Using a phospho-specific antibody we observed that endogenous sGC phosphorylation on Ser 64 increases in cells and tissues exposed to NO, in a PKG-inhibitable manner. Wild-type (wt) sGC coexpressed with ΔPKG exhibited lower basal and NO-stimulated cGMP accumulation, whereas the S64A α1/β1 sGC was resistant to the PKG-induced reduction in activity. Using purified sGC we observed that the S64D α1 phosphomimetic /β1 dimer exhibited lower Vmax; moreover, the decrease in Km after NO stimulation was less pronounced in S64D α1/β1 compared to wild-type sGC. Expression of a phosphorylation-deficient sGC showed enhanced responsiveness to endothelium-derived NO, reduced desensitization to acute NO exposure, and allowed for greater VASP phosphorylation.

Conclusions—We conclude that PKG phosphorylates sGC on Ser64 of the α1 subunit and that phosphorylation inhibits sGC activity, establishing a negative feedback loop.
Transcriptional Regulation During Development of the Ductus Arteriosus
Authors: Ivey Kathryn N. , Sutcliffe David , Richardson James , Clyman Ronald I. , Garcia Joseph A. , Srivastava Deepak
Published: July 2008

The ductus arteriosus is a specialized blood vessel containing highly differentiated and contractile vascular smooth muscle, derived largely from neural crest cells, that is essential for fetal life but typically closes after birth. Impaired development of the ductus arteriosus or disruption of signaling pathways that initiate postnatal closure can result in persistent patency of the ductus arteriosus, the third most common congenital heart defect. We found that Tfap2β, a transcription factor associated with patent ductus arteriosus in humans, was uniquely expressed in mouse ductal smooth muscle.
Endothelin-1
and the hypoxia-induced transcription factor,
Hif2
α were also highly enriched in ductal smooth muscle at embryonic day 13.5 and were dependent on Tfap2β for their expression in this domain. Hif2α functioned as a negative regulator of Tfap2β-induced transcription by disrupting protein–DNA interactions, suggesting a negative feedback loop regulating Tfap2β activity. Our data indicate that Tfap2β, Et-1, and Hif2α act in a transcriptional network during ductal smooth muscle development and that disruption of this pathway may contribute to patent ductus arteriosus by affecting the development of smooth muscle within the ductus arteriosus.
Cathepsin B, K, and S Are Expressed in Cerebral Aneurysms and Promote the Progression of Cerebral Aneurysms
Authors: Aoki Tomohiro , Kataoka Hiroharu , Ishibashi Ryota , Nozaki Kazuhiko , Hashimoto Nobuo
Published: July 2008

Backgroud and Purpose—

A cerebral aneurysm (CA) causes catastrophic subarachnoid hemorrhage. Degradation of extracellular matrix in arterial walls is a prominent feature of cerebral aneurysms. We investigated the expression and role of cysteine cathepsins, collagen- and elastin- degrading proteinases, in CA progression.

Methods—

CAs were induced in Sprague-Dawley rats with or without cysteine cathepsin inhibitor, NC-2300. Expression of cathepsin B, K, S, and cystatin C, an endogenous inhibitor of cysteine cathepsins, in aneurysmal walls was examined in quantitative RT-PCR and immunohistochemistry. The activity of cysteine cathepsins and collagenase I and IV in aneurysmal walls was also assessed. Finally, expression of cysteine cathepsins and cystatin C in human CAs was examined.

Results—

Quantitative RT-PCR and immunohistochemistry revealed upregulated expression of cathepsin B, K, and S in the late stage of aneurysm progression. In contrast, cystatin C expression was reduced with aneurysm progression. Treatment with NC-2300 resulted in the decreased incidence of advanced CAs. The activity of cysteine cathepsins and collagenase I and IV in aneurysmal walls was reduced and elastin content was increased in the NC-2300–treated group. Finally, immunohistochemistry for cysteine cathepsins and cystatin C expression in human CAs showed the same expression pattern as in the rat study.

Conclusions—

Data obtained by using NC-2300 revealed an important role of cysteine cathepsins in the progression of CAs. Our findings strongly suggest that an imbalance between cysteine cathepsins and their inhibitor may cause the excessive breakdown of extracellular matrix in the arterial walls leading to the progression and rupture of CAs.
Protecting Against Cerebrovascular Injury
Authors: Jin Guang , Arai Ken , Murata Yoshihiro , Wang Sophia , Stins Monique F. , Lo Eng H. , van Leyen Klaus
Published: July 2008

Background and Purpose—

The concept of the neurovascular unit suggests that effects on brain vasculature must be considered if neuroprotection is to be achieved in stroke. We previously reported that 12/15-lipoxygenase (12/15-LOX) is upregulated in the peri-infarct area after middle cerebral artery occlusion in mice, and 12/15-LOX contributes to brain damage after ischemia–reperfusion. The current study was designed to investigate 12/15-LOX involvement in vascular injury in the ischemic brain.

Methods—

In cell culture, a human brain microvascular endothelial cell line was subjected to either hypoxia or H
2
O
2
-induced oxidative stress with or without lipoxygenase inhibitors. For in vivo studies, mice were subjected to 90 minutes middle cerebral artery occlusion, and the effects of either 12/15-LOX gene knockout or treatment with lipoxygenase inhibitors were compared. Expression of 12/15-LOX and claudin-5 as well as extravasation of immunoglobulin G were detected by immunohistochemistry. Edema was measured as water content of brain hemispheres according to the wet–dry weight method.

Results—

Brain endothelial cells were protected against hypoxia and H
2
O
2
by the lipoxygenase inhibitor baicalein. After focal ischemia, 12/15-LOX was increased in neurons and endothelial cells. The vascular tight junction protein claudin-5 underwent extensive degradation in the peri-infarct area, which was partially prevented by the lipoxygenase inhibitor baicalein. Leakage of immunoglobulin G into the brain parenchyma was significantly reduced in 12/15-LOX knockout mice as well as wild-type mice treated with baicalein. Likewise, brain edema was significantly ameliorated.

Conclusion—

12/15-LOX may contribute to ischemic brain damage not just by causing neuronal cell death, but also by detrimental effects on the brain microvasculature. 12/15-LOX inhibitors may thus be effective as both neuroprotectants and vasculoprotectants.