Clear cell, giant myoepithelioma of tongue base: a diagnostic and surgical challenge

Clear cell variant is a rare histological type of myoepithelioma seen in parotid and soft palate. This article describes clear cell variant of myoepithelioma in the tongue base, which has not been reported in the literature so far. A 34-year-old man presented with dysphagia and foreign body sensation of throat. Video laryngostroboscopy using a 70° rigid telescope showed a smooth globular mass in the oropharynx arising from the tongue base. Based on clinical and radiological findings, the lesion was considered as benign. Fine needle aspiration cytology was not attempted fearing risk of bleeding, aspiration and airway compromise. Hence, an excisional biopsy followed by definitive histopathological examination without frozen section was planned. The patient underwent coblator-assisted excision and subsequently sent for histopathological analysis. There were cuboidal cell nests with abundant clear cytoplasm which stained positive for p63 by immunohistochemistry. This helped in establishing the diagnosis of clear cell myoepithelioma.

Lontra longicaudis infected with canine parvovirus and parasitized by Dioctophyma renale

ABSTRACT: This study describes a case of parvovirus infection in a river otter (Lontra longicaudis) assisted at the Wildlife Rehabilitation Center and Wildlife Screening Center, Federal University of Pelotas (UFPel), Rio Grande do Sul state, Brazil. Clinical signs included apathy, dark and fetid diarrhea, and crusted lesions on the palmar pads of the fore and hind limbs. The animal died after undergoing support treatment with antibiotics, anti-inflammatory, and fluid therapy. At necropsy, the intestines were reddened and edematous and the right kidney was diminished by one third of its normal size and covered with whitish, spongy material. A female Dioctophyma renale was found free in the abdominal cavity. Histologically, dilatation of the intestinal crypts and fusion and blunting of the intestinal villi were observed. In addition, moderate, multifocal lymphocytic enteritis with lymphoid depletion in Peyer’s patches and mesenteric lymph nodes were present. Immunohistochemistry with anti-canine parvovirus monoclonal antibody (anti-CPV) was strongly positive in the bone marrow cells and enterocytes of the intestinal crypts, confirming the diagnosis of parvovirus infection. The peritoneum on the right kidney was expanded with a cuboidal cell border, forming multiple papillary projections associated with eggs of D. renale and severe inflammatory infiltrate (giant cells, macrophages, lymphocytes, eosinophils, and plasma cells). Areas of necrosis and mineralization were also observed. Due to fragmentation and degradation of its natural habitat, the otter approached the urban area and was contaminated with the virus, which is hosted and disseminated by domestic animals. Infection with D. renale can be associated with the large population of parasitized domestic animals, which eliminate the helminth eggs through urine, contaminating the environment where the parasite intermediate and paratenic hosts co-inhabit. The diseases of these animals can be a decline factor of wild populations that inhabit the region and are an alert to spillover risk.

Regulation of tensile stress in response to external forces coordinates epithelial cell shape transitions with organ growth and elongation

The role of actomyosin contractility at epithelial adherens junctions has been extensively studied. However, little is known about how external forces are integrated to establish epithelial cell and organ shape in vivo. We use the Drosophila follicle epithelium to investigate how tension at adherens junctions is regulated to integrate external forces arising from changes in germline size and shape. We find that overall tension in the epithelium decreases despite pronounced growth of enclosed germline cells, suggesting that the epithelium relaxes to accommodate growth. However, we find local differences in adherens junction tension correlate with apposition to germline nurse cells or the oocyte. We demonstrate that medial Myosin II coupled to corrugating adherens junctions resists nurse cell-derived forces and thus maintains apical surface areas and cuboidal cell shapes. Furthermore, medial reinforcement of the apical surface ensures cuboidal-to-columnar cell shape transitions and imposes circumferential constraints on nurse cells guiding organ elongation. Our study provides insight into how tension within an adherens junction network integrates growth of a neighbouring tissue, mediates cell shape transitions and channels growth into organ elongation.

Cerebrospinal Fluid Secretion by the Choroid Plexus

The choroid plexus epithelium is a cuboidal cell monolayer, which produces the majority of the cerebrospinal fluid. The concerted action of a variety of integral membrane proteins mediates the transepithelial movement of solutes and water across the epithelium. Secretion by the choroid plexus is characterized by an extremely high rate and by the unusual cellular polarization of well-known epithelial transport proteins. This review focuses on the specific ion and water transport by the choroid plexus cells, and then attempts to integrate the action of specific transport proteins to formulate a model of cerebrospinal fluid secretion. Significant emphasis is placed on the concept of isotonic fluid transport across epithelia, as there is still surprisingly little consensus on the basic biophysics of this phenomenon. The role of the choroid plexus in the regulation of fluid and electrolyte balance in the central nervous system is discussed, and choroid plexus dysfunctions are described in a very diverse set of clinical conditions such as aging, Alzheimer's disease, brain edema, neoplasms, and hydrocephalus. Although the choroid plexus may only have an indirect influence on the pathogenesis of these conditions, the ability to modify epithelial function may be an important component of future therapies.

Abstract 222: Dkk1 and Msx2-Wnt7b Signaling Reciprocally Regulate the Endothelial-Mesenchymal Transition in Aortic Endothelial Cells

Objective Endothelial cells (ECs) can undergo an endothelial-mesenchymal transition (EndMT) during tissue fibrosis. Wnt- and Msx2-regulated signals participate in arteriosclerotic calcification and fibrosis. We studied the impact of Wnt7, Msx2, and Dkk1 (Wnt7 antagonist) on EndMT in primary aortic endothelial cells (AoECs). Methods and Results Transduction of AoECs with vectors expressing Dkk1 suppressed EC differentiation and induced a mineralizing myofibroblast phenotype. Dkk1 suppressed claudin 5, PECAM, cadherin 5 (Cdh5), Tie1 and Tie2. Dkk1 converted the cuboidal cell monolayer into a spindle-shaped multilayer and inhibited EC cord formation. Myofibrogenic and osteogenic markers - e.g., SM22, type I collagen, Osx, Runx2, alkaline phosphatase – were upregulated by Dkk1 via activin-like kinase / Smad pathways. Dkk1 increased fibrosis and mineralization of AoECs cultured under osteogenic conditions - the opposite of mesenchymal cell responses. Msx2 and Wnt7b maintained the “cobblestone” morphology of differentiated ECs and promoted EC marker expression. Deleting EC Wnt7b with the Cdh5-Cre transgene in Wnt7b(fl/fl);LDLR-/- mice upregulated aortic osteogenic genes (Osx, Sox9, Runx2, Msx2) and nuclear pSmad1/5, and increased collagen accumulation. Conclusions Dkk1 enhances EndMT in AoECs, while Msx2-Wnt7 signals stabilize EC phenotype. EC responses to Dkk1, Wnt7b, and Msx2 are the opposite of mesenchymal cell responses, coupling EC phenotypic stability with osteofibrogenic predilection during arteriosclerosis.

276 CHARACTERIZATION OF BOVINE EPIBLAST OUTGROWTH COLONIES DERIVED FROM DAY 12 BLASTOCYSTS

Isolation and culture of mouse embryonic stem (ES) cells has been performed for many years, and the improvements achieved throughout the last decade in the human field has evoked great hopes for future cell replacement therapies. However, despite certain similarities in the molecular regulation of pluripotency between man and mouse, there is a need for developing large animal models. The aim of our study was to isolate, culture, and characterize bovine ES-like cell colonies derived from the epiblast. Embryos were produced by in vitro maturation, fertilization, and culture. After 6 days of in vitro culture, blastocysts were transferred to synchronized heifers and allowed to develop for an additional 6 days in vivo. At Day 12 after insemination, embryos were collected by nonsurgical flushing. Embryonic discs were isolated from 15 blastocysts by microsurgery and cultured on mitomycin-inactivated mouse embryonic fibroblasts (SLN cells) in DMEM/F12 medium supplemented with 15% fetal calf serum (FCS), 5% knockout serum replacement (KSR), 106UmL–1 leukemia inhibitory factor (LIF), basic fibroblast growth factor (bFGF), nonessential amino acids (NEAA), and nucleosides. After 4 (n = 6), 6 (n = 4), and 8 days (n = 5) of culture, the primary outgrowth colonies were fixed in 4% paraformaldehyde, embedded in paraffin, sectioned, and exposed to antisera recognizing Oct-4 (pluripotency marker; Santa Cruz Biotechnology, Santa Cruz, CA, USA), Vimentin (mesenchyme marker; Zymed Laboratories, South San Francisco, CA, USA), Cytokeratin-8 (trophectoderm marker; Becton, Dickinson and Co., Franklin Lakes, NJ, USA), and α-1-Fetoprotein (hypoblast marker; DakoCytomation, Glostrup, Denmark). The site of antigen-antibody reaction was revealed using the ABC-AEC-method and counterstained with hematoxylin. At Day 4, all colonies had developed a compact central core of cells with a low cytoplasm-to-nucleus ratio, surrounded by a monolayer of squamous cells. At Days 6 and 8, 3 out of 4 and 3 out of 5 colonies, respectively, still presented the compact core which occasionally was encapsulated by a squamous or cuboidal cell sheet. In the remaining colonies, a compact core was less defined. Oct-3/4 staining was observed in the nuclei of the compact core in 5 out of 6 colonies on Day 4, and in all colonies presenting a compact core on Days 6 and 8. However, whereas all nuclei in the core were stained on Days 4 and 6, only scattered nuclei were stained on Day 8. Vimentin staining was observed in the cytoplasm of cells in the compact core in 3 out of 6 Day 4 colonies, in all Day 6 colonies presenting a compact core, but not in any Day 8 colonies. In contrast, α-1-Fetoprotein staining intensity increased with culture period and was mostly observed in squamous monolayer portions. Cytokeratin-8 staining was weak and restricted to the cytoplasm of the cells encapsulating and surrounding the core in 2 Day 6 colonies and a single Day 8 colony. In conclusion, epiblasts isolated from Day 12 bovine blastocysts efficiently attach to feeder cells and develop outgrowth colonies with cores containing presumptive pluripotent cells (Oct-4). However, these cells to some degree lost Oct-4 expression toward Day 8 and were, in parallel, to some degree overgrown by cells of hypoblast (α-1-Fetoprotein) and trophectoderm (Cytokeratin-8) origin.

Changes in the epithelium of Rathke cleft cyst associated with inflammation

Object. Rathke cleft cysts (RCCs) are composed of tall, well-differentiated, ciliated columnar epithelia. Their structures are altered by hyperplasia or squamous metaplasia, but their cause remains unknown. Methods. The authors studied pathological findings and anterior pituitary function in 20 patients harboring RCCs. They classified RCC epithelium as either single (a single ciliated columnar cell lining or a flattened cuboidal cell lining) or stratified (a stratified ciliated columnar cell lining, basal cell hyperplasia, columnar cell hyperplasia, or squamous metaplasia). Inflammation was classified as acute, subacute, chronic, or end stage. The epithelial cell lining was observed in 13 specimens obtained during surgery (six specimens contained single and seven contained stratified epithelia). Inflammation had penetrated the cyst epithelium or subjacent stroma in 10 patients, and the stage of inflammation correlated well with the type of epithelia group: early stages of inflammation in the single epithelium group and chronic or end-stage inflammation in the stratified epithelia (p = 0.0027). The adenohypophysis was identified in 21 surgical specimens. Postoperatively, growth hormone (p = 0.019), cortisol (p = 0.027), and thyroid-stimulating hormone (p = 0.039) responses significantly worsened as the inflammation progressed. The presence of diabetes insipidus correlated well with advanced stages of neurohypophysitis (p = 0.025). Conclusions. Epithelial stratification in the RCC is caused by inflammation that may extend into the adjacent adenohypophysis or neurohypophysis and overwhelm the hypophysis, resulting in panhypopituitarism. Transsphenoidal excision may represent the best choice for treatment, at least for cases of RCC in which there is partial impairment of hypophysial function.

Neonatal Clara cell toxicity by 4-ipomeanol alters bronchiolar organization in adult rabbits

Nonciliated bronchiolar (Clara) cells metabolize environmental toxicants, are progenitor cells during development, and differentiate postnatally. Because differentiating Clara cells of neonatal rabbits are injured at lower doses by the cytochrome P-450-activated cytotoxicant 4-ipomeanol than are those of adults, the impact of early injury on the bronchiolar epithelial organization of adults was defined by treating neonates (3–21 days) and examining them at 4–6 wk. Bronchiolar epithelium of 6-wk-old animals treated on day 7 was most altered from that of control animals. Almost 100% of the bronchioles were lined by zones of squamous epithelial cells. Compared with control animals, the distal bronchiolar epithelium of 4-ipomeanol-treated animals had more squamous cells (70–90 vs. 0%) with a reduced overall epithelial thickness (25% of control value), fewer ciliated cells (0 vs. 10–20%), a reduced expression of Clara cell markers of differentiation (cytochrome P-4502B, NADPH reductase, and 10-kDa protein), and undifferentiated nonciliated cuboidal cell ultrastructure. We conclude that early injury to differentiating rabbit Clara cells by a cytochrome P-450-mediated toxicant inhibits bronchiolar epithelial differentiation and greatly affects repair.