Effect of concanavalin A on the palatine ridges in vitro]

Concanavalin A acts in three ways on palatal shelves cultivated in vitro: 1. it has a mitogen effect, particularly on the medio palatal epithelium; 2. this produces thickening of this epithelium; 3. a delayed fusion or no fusion of the palatal shelves. The renewed mitogen activity and loss of adhesion properties seem to be linked.     

In vivo and in vitro incorporation of 3H-thymidine in the uterus of the rabbit during pseudopregnancy

During pseudopregnancy in the Rabbit the DNA synthesis in the uterine epithelium is very reduced. These results conjoined with the decrease of the mitotic index and previous ultrastructural observations allow to think that multinucleated cells proceed mainly by cell fusion.     

Carbonic anhydrase type II in regenerating retinal pigment epithelium. A histochemical study in the rabbit

Type II carbonic anhydrase (CAII) in the cytoplasm of the retinal pigment epithelium (RPE) may contribute to the transport of water and solutes across the RPE. The activity of this enzyme in RPE during its response to damage, e.g., during regeneration, is therefore of interest in understanding retinal disease. Immuno-histochemistry was used to compare CAII activity of normal RPE and RPE experimentally induced to regenerate. In normal rabbits, the RPE stained intensely with a peroxidase-linked antibody specific for human CAII. Regenerating RPE stained less intensely. Within the regenerating epithelium, staining appeared more intense in mature cells than in immature ones, suggesting that CAII activity gradually returns during RPE regeneration.     

Multinucleated cells in the retinal pigment epithelium: A scanning electron microscopic study

Summary Multinucleated cells in the retinal pigment epithelium of the albino rat are shown with the scanning electron microscope beside normal mononucleated cells. We suggest that such elements are formed during foetal life, owing to the absence of any mitotic activity in adult rats.     

Common Molecular Mechanisms of Mammary Gland Development and Breast Cancer

During its lifetime, the mammary gland undergoes many phases of development and differentiation. Much of this occurs during puberty, when the ductal epithelium expands by branching morphogenesis, invading the surrounding fat pad to form an organised mammary tree. Throughout its existence, the epithelium will go through several cycles of proliferation and cell death during pregnancy, lactation and involution. Many of the signalling mechanisms which control the initial invasion of the fat pad by the epithelium, and regulate its continuing plasticity, can be harnessed or corrupted by tumour cells in order to support their aberrant growth and progression towards invasion. This is true not just for the epithelial cells themselves but also for cells in the surrounding microenvironment, including fibroblasts, macrophages and adipocytes. This review examines the complex web of signalling and adhesion interactions controlling branching morphogenesis, and how their alteration can promote malignancy. Current in vivo and in vitro mammary gland models are also discussed. (Part of a Multi-author Review)     

Seasonal variations in mitosis in the frog: a field study.

Field studies have shown that there is a seasonal variation in mitosis of lens and corneal epithelium (high in May and June, low during the rest of the year). This phenomenon can be reproduced in the laboratory by temperature manipulation. The response in the lens depends on the presence of the pituitary gland while the corneal one seems to be independent of it.     

The membrane domain of vacuolar H<Superscript>+</Superscript>ATPase: a crucial player in neurotransmitter exocytotic release

V-ATPases are multimeric enzymes made of two sectors, a V1 catalytic domain and a V0 membrane domain. They accumulate protons in various intracellular organelles. Acidification of synaptic vesicles by V-ATPase energizes the accumulation of neurotransmitters in these storage organelles and is therefore required for efficient synaptic transmission. In addition to this well-accepted role, functional studies have unraveled additional hidden roles of V0 in neurotransmitter exocytosis that are independent of the transport of protons. V0 interacts with SNAREs and calmodulin, and perturbing these interactions affects neurotransmitter release. Here, we discuss these data in relation with previous results obtained in reconstituted membranes and on yeast vacuole fusion. We propose that V0 could be a sensor of intra-vesicular pH that controls the exocytotic machinery, probably regulating SNARE complex assembly during the synaptic vesicle priming step, and that, during the membrane fusion step, V0 might favor lipid mixing and fusion pore stability.     

Zur Frage der Neubildung von Primordialfollikeln aus dem Keimepithel während der Geschlechtsreife im menschlichen Ovar

Summary Findings in the human ovary confirmed the fact already pointed out in animal ovaries that under the influence of oestrogens the germinal epithelium is capable of forming new oocytes. Whether the germinal epithelium of the mature woman can form new oocytes under normal conditions cannot be determined as yet, but the present findings allow the conclusion that neo-oogenesis during the reproductive period of women seems possible. Further investigations, now in progress, are required to determine this possibility.     

Mesenchymal–epithelial interactions during digestive tract development and epithelial stem cell regeneration

The gastrointestinal tract develops from a simple and uniform tube into a complex organ with specific differentiation patterns along the anterior–posterior and dorso-ventral axes of asymmetry. It is derived from all three germ layers and their cross-talk is important for the regulated development of fetal and adult gastrointestinal structures and organs. Signals from the adjacent mesoderm are essential for the morphogenesis of the overlying epithelium. These mesenchymal–epithelial interactions govern the development and regionalization of the different gastrointestinal epithelia and involve most of the key morphogens and signaling pathways, such as the Hedgehog, BMPs, Notch, WNT, HOX, SOX and FOXF cascades. Moreover, the mechanisms underlying mesenchyme differentiation into smooth muscle cells influence the regionalization of the gastrointestinal epithelium through interactions with the enteric nervous system. In the neonatal and adult gastrointestinal tract, mesenchymal–epithelial interactions are essential for the maintenance of the epithelial regionalization and digestive epithelial homeostasis. Disruption of these interactions is also associated with bowel dysfunction potentially leading to epithelial tumor development. In this review, we will discuss various aspects of the mesenchymal–epithelial interactions observed during digestive epithelium development and differentiation and also during epithelial stem cell regeneration.     

Fibulin-2 is involved in early extracellular matrix development of the outgrowing mouse mammary epithelium

Cell–matrix interactions control outgrowth of mammary epithelium during puberty and pregnancy. We demonstrate here that the glycoprotein fibulin-2 (FBLN2) is strongly associated with pubertal and early pregnant mouse mammary epithelial outgrowth. FBLN2 was specifically localized to the cap cells of the terminal end buds during puberty and to myoepithelial cells during very early pregnancy (days 2–3) even before morphological changes to the epithelium become microscopically visible, but was down-regulated thereafter. Exposure to exogenous oestrogen (E2) or E2 plus progesterone (P) increased Fbln2 mRNA expression in the pubertal gland, indicating hormonal control. FBLN2 was co-expressed and co-localised with the proteoglycan versican (VCAN) and co-localised with laminin (LN), while over-expression of FBLN2 in HC-11 cells increased cell adhesion to several extracellular matrix proteins including LN and fibronectin, but not collagens. Mammary glands from Fbln2 knockout mice showed no obvious phenotype but increased fibulin-1 (FBLN1) staining was detected, suggesting a compensatory mechanism by other fibulin family members. We hypothesise that similar to embryonic aortic smooth muscle development, FBLN2 and VCAN expression alters the cell–matrix interaction to allow mammary ductal outgrowth and development during puberty and to enable epithelial budding during pregnancy.     

Intestinal epithelial barrier and mucosal immunity

Intestinal mucosa integrates primary digestive functions with immune functions such as pathogen surveillance, antigen transport and induction of mucosal immunity and tolerance. Intestinal adaptive immunity is elicited in organized mucosa-associated lymphoid tissue (O-MALT) that is composed of antigen-presenting cells and lymphocytes and achieved by effector cells widely distributed in mucosa (diffuse MALT or D-MALT). Interaction between the intestinal epithelium, the O-MALT and the diffuse MALT plays a critical role in establishing an adequate immune response. In regions associated to O-MALT, lympho-epithelial cross-talks lead to acquisition of a specific epithelial phenotype that contributes to O-MALT organization and functionality. Beyond the expression of several innate immune functions, the intestinal epithelium may directly take up and present antigens due to the expression of major histocompatibility complex (MHC) and MHC-related molecules. A complex genetic program that will be outlined in the present review controls the development of immune functions of the intestinal epithelium. The effect of environmental signals on the modulation of this ontogenetic program during development and neonatal life, from bioactive components of amniotic fluid to lactation and bacterial colonization, will be discussed.     

Gill lesions in Cichlid fishes after intoxication with the insecticide Fenthion.

The toxic effects of Fenthion on the gills of Cichlid fishes were investigated. In Herotilapia multispinosa hyperplasia and separation of the respiratory epithelium, lamellar telangiectasis and thrombosis occurred. The lamellar epithelium of surviving fish regenerated in all cases. In Tilapia leucosticta no telangiectasis was found, but all the secondary lamellae were fused due to the severe hyperplasia of the gill epithelium.     

Gill lesions in Cichlid fishes after intoxication with the insecticide Fenthion

Summary The toxic effects of Fenthion on the gills of Cichlid fishes were investigated. In Herotilapia multispinosa hyperplasia and separation of the respiratory epithelium, lamellar telangiectasis and thrombosis occurred. The lamellar epithelium of surviving fish regenerated in all cases. In Tilapia leucosticta no telangiectasis was found, but all the secondary lamellae were fused due to the severe hyperplasia of the gill epithelium.This work was undertaken with the aid of Prof. Dr. E. Kulzer.     

Frequency of the various stages of the seminiferous epithelium in different strains of male mice

Summary The duration of the various development stages of the seminiferous epithelium in different strains of male mice was determined by scoring the frequency distribution in randomly selected tubule cross-sections. The results obtained show a difference in the duration of the various stages between the different strains.Acknowledgments. The authors would like to thank Dr.J. Baarli and many other members of the Health Physics Group for their help and valuable assistance during the process of this work.     

Über die Beteiligung von Hauptstückepithel am parietalen Blatt im corpusculum renale bei der Maus (Mus musculus)

Summary The epithelium of the proximal convoluted tubule participates in the formation of the parietal layer in the area of the urinary pole, as can already be observed in the first renal corpuscles of the mouse fetus. Sexual hormones do not seem to have any influence on this structural characteristic, neither during prenatal nor postnatal life.     

Hedgehog signaling in pancreas development and disease

Since its discovery, numerous studies have shown that the Hedgehog (Hh) signaling pathway plays an instrumental role during diverse processes of cell differentiation and organ development. More recently, it has become evident that Hh signaling is not restricted to developmental events, but retains some of its activity during adult life. In mature tissues, Hh signaling has been implicated in the maintenance of stem cell niches in the brain, renewal of the gut epithelium and differentiation of hematopoietic cells. In addition to the basal function in adult tissue, deregulated signaling has been implicated in a variety of cancers, including basal cell carcinoma, glioma and small cell lung cancer. Here, we will focus on the role of Hh signaling in pancreas development and pancreatic diseases, including diabetes mellitus, chronic pancreatitis and pancreatic cancer. Received 5 August 2005; received after revision 4 November 2005; accepted 22 November 2005     

Progress in understanding the neuronal SNARE function and its regulation

Vesicle budding and fusion underlies many essential biochemical deliveries in eukaryotic cells, and its core fusion machinery is thought to be built on one protein family named soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE). Recent technical advances based on site-directed fluorescence labelling and nano-scale detection down to the single-molecule level rapidly unveiled the protein and the lipid intermediates along the fusion pathway as well as the molecular actions of fusion effectors. Here we summarize these new exciting findings in context with a new mechanistic model that reconciles two existing fusion models: the proteinaceous pore model and the hemifusion model. Further, we attempt to locate the points of action for the fusion effectors along the fusion pathway and to delineate the energetic interplay between the SNARE complexes and the fusion effectors. Received 01 July 2008; received after revision 29 August 2008; accepted 23 September 2008     

The age-dependent difference in the response of the vagina to the neonatal administration of testosterone propionate in Long-Evans female rats

Summary The ability of the vaginal epithelium to respond to testosterone propionate by producing keratin was established when female rats were 3 days of age, whereas the vaginal stroma from rats 2 days old or less was capable of responding to the androgen and might destroy the vaginal epithelium.     

Visual pigment regeneration: occurrence in frog retina upside down upon the pigment epithelium

Visual pigment regeneration in the frog requires apposition between the retina and retinal pigment epithelium. However, regeneration occurs nearly as well with the retina upside down (i.e. with the inner limiting membrane facing the pigment epithelium) as right side up.