Search

The absence of the interstitial cells of Cajap (ICC) have been suggested as the cause of abnormal intestinal motility in W/W(super V) mice as a result of the lack of slow-wave-type action potentials. In a study of the small intestine of W mutant mice, L-type calcium channel blocker abolished action potentials whereas potassium channel blockers evoked action potentials. Electron microscopy reveal that generation of action potentials was due to the presence of a few ICC at the deep muscular plexus of the small intestine.

The Kit receptor tyrosine kinase is expressed by the intestinal cells of Cajal. This tyrosine kinase is the cause for the pacemaker activity in mammalian gut resulting in phase contraction. The intestinal cells of Cajal are absent in the mice which have mutations in the Kit gene which is responsible for the functions of the Kit receptor tyrosine kinase.

The muscle coat of the human lower oesophageal sphincter and stomach was studied 5 cm above and 4 cm below the gastro-oesophageal junction. Four subjects were operated on for motility disorders of the esophagus, two for a hypertensive lower oesophageal sphincter and two for an epiphrenic diverticulum; six subjects were operated on for oesophageal or gastric carcinomas. Specimens were fixed in phosphate-buffered OsO4, embedded in Epon, contrasted with uranyl acetate and lead citrate and observed under a Siemens Elmiskop Ia electron microscope. Both the oesophageal and gastricmuscle cells, which showed features typical of this cell type, were innervated by multiple varicosities that were rich in synaptic vesicles; these varicosities were generally rarely encountered at distances less than 1000Å from muscle cells. Only a very few, close neuromuscular junctions were detected. Special cells, which correspond to the "interstitial cells of Cajal" as reported by other authors, were discerned at the periphery of muscle cell bundles. These cells were characterized by an elongated cell body with many thin branches and an oval, sometimes indented nucleus. Some pinocytotic vesicles were located at the cell periphery. These cells were surrounded by a discontinuous basal lamina and were seen in close contact with each other and with muscle cells; the close contact areas were often very wide. The cytoplasm contained variable amounts of mitochondria, a well-developed smooth endoplasmic reticulum and a Golgi complex. As a characteristic feature, bundles of thin filaments were located at the cell periphery and were attached to electron-dense areas of the cell membrane. Morphologically, these filaments resembled myofilaments; they were present in variable amounts and were sometimes very numerous. The observation that the cytoplasmic organelles and filaments varied in number, is probably related to the different functional properties of these cells. Interstitial cells were richly innervated by varicose nerve fibers that were densely packed with synaptic vesicles; many close junctions to nerve endings were also detected. These morphological data lead us to assume that the interstitial cells demonstrated by the electron microscope do not correspond to the cells initially identified by Cajal and cannot even be considered connective tissue cells. We propose that they are specialized smooth muscle cells that are involved in generating spontaneous, myogenic electrical activity in the gastrointestinal tract. [ABSTRACT FROM AUTHOR]

The effects of a large dose of vinblastine sulfate (2 mg/kg body weight) on proliferating odontoblast precursors and secretory odontoblasts in the continuously growing rat incisor were studied. The rats were killed 6 h, 24 h, 3 d and 7 d after vinblastine injection. Most cells in the proliferating zone contained arrested mitoses, or had perished after 24 h After 3 and 7 d, the odontoblasts derived from this zone were reduced in number, and showed altered cell shapes The odontoblasts had produced irregular dentin The secretory odontoblasts had displaced nuclei and altered cell shapes after 24 h Those most affected were opposite early mineralized dentin In some incisors the cells had perished. In the protracted experiments almost all the odontoblasts were changed and had produced abnormal dentin In the early mineralized dentin area, accumulations of cells were present after 3 d, and osteodenun-like material after 7 d. [ABSTRACT FROM AUTHOR]

The secreted glycoprotein YKL-40 participates in cell differentiation, inflammation, and cancer progression. High YKL-40 expression is reported during early human development, but its functions are unknown. Six human embryonic stem cell (hESC) lines were cultured in an atmosphere of low or high oxygen tension, in culture medium with or without basic fibroblast growth factor, and on feeder layers comprising mouse embryonic fibroblasts or human foreskin fibroblasts to evaluate whether hESCs and their progeny produced YKL-40 and to characterize YKL-40 expression during differentiation. Secreted YKL-40 protein and YKL-40 mRNA expression were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative RT-PCR. Serial-sectioned colonies were stained for YKL-40 protein and for pluripotent hESC (OCT4, NANOG) and germ layer (HNF-3β, PDX1, CD34, p63, nestin, PAX6) markers. Double-labeling showed YKL-40 expression in OCT4-positive hESCs, PAX6-positive neuroectodermal cells, and HNF-3β-positive endodermal cells. The differentiating progeny showed strong YKL-40 expression. Abrupt transition between YKL-40 and OCT4-positive hESCs and YKL-40-positive ecto- and neuroectodermal lineages was observed within the same epithelial-like layer. YKL-40-positive cells within deeper layers lacked contact with OCT4-positive cells. YKL-40 may be important in initial cell differentiation from hESCs toward ectoderm and neuroectoderm, with retained epithelial morphology, whereas later differentiation into endoderm and mesoderm involves a transition into the deeper layers of the colony.

The hypothesis was put forward by Thuneberg that rhythmically contracting interstitial cells of Cajal (ICC) were sensing stretch of the musculature and that this information was transmitted to smooth muscle cells via peg and socket contacts. The present study provides the evidence for the contractile nature of ICC as perceived by Thuneberg. The contractile activity is shown by video frame subtraction and by tracking areas of interest in sequential video frames. Thuneberg used neonatal ICC in culture maintained between two coverslips thereby allowing growth factors to quickly reach optimal concentrations. Contractions of ICC were seen to precede smooth muscle contractions. In addition, strong contractions were observed solely in branches of ICC. It is hoped that this communication will stimulate discussion about the contractile nature of ICC and that this phenomenon will eventually find its place amongst the physiological properties of the ICC networks of the gut musculature., (2010. © 2010 Wiley-Liss, Inc.)