Apical cytoplasm

About: Apical cytoplasm is a research topic. Over the lifetime, 1080 publications have been published within this topic receiving 36131 citations.

Fine structure of the oxynticopeptic cells in the gastric glands of the ruin lizard, Podarcis sicula campestris De Betta, 1857.

Abstract: The results of an ultrastructural investigation of the gastric glands of the ruin lizard are reported. In this reptile the stomach can be divided into a larger fundus and a smaller pars pilorica. Fundic glands are characterized by three main kinds of cells: mucous, endocrine, and oxynticopeptic; the latter were not observed in the pyloric glands. The morphological features of the oxynticopeptic cells change from the proximal to the distal region of the fundic mucosa. In the proximal region, numerous electron-dense secretory granules, a well-developed granular endoplasmic reticulum, an evident Golgi complex, and a reduced system of smooth-surfaced vesicles and tubules in the apical cytoplasm characterize these cells. In the distal fundic region, oxynticopeptic cells possessed numerous mitochondria and a well-developed smooth-surfaced endoplasmic reticulum, but secretory granules were rare. These data suggest the existence of a gradient in the production of proteolytic enzymes, and perhaps also of hydrochloric acid, along the oral-aboral axis of the stomach. The results are discussed with regard to the evolution of the gastric glands and of the digestive mechanism in vertebrates.

Fine structure of the striated border of the intestinal cells of Ancylostoma caninum.

Abstract: The striated border of the intestinal cells is composed of numerous microvilli. The terminal web is separated from the apical surface of the intestinal cell by a cytoplasmic layer. This layer is joined with the main body of cytoplasm beneath the terminal web by many connections which perforate the latter. However, the apical layer is devoid of fibrous elements, mitochondria, and pigment granules found in the cytoplasm proper. The terminal web is densely homogeneous and has extensions upwards through the apical cytoplasm into the microvilli forming a dense cytoplasmic core in each. The web extends some distance down the lateral plasma membranes forming a perforated cap over the main cytoplasmic mass of the intestinal cell. This type of terminal web has not been described in other nematodes. Browne and Chowdhury (1959) concluded from electron microscopy that the intestinal lumen of Ancylostoma caninum was lined with true cilia. In a later study Browne, Chowdhury, and Lipscomb (1965) modified that conclusion and stated that the structures were suggestive of cilia but that inadequate fixation prevented a specific determination. In the present study the structure of the luminal area of the intestinal cell of A. caninum was clarified by the use of modern techniques of fixation and embedding. MATERIALS AND METHODS Adult A. caninum were obtained from experimentally infected dogs. Each worm was placed in ice-cold 4% glutaraldehyde in phosphate buffer (Pease, 1964). A transverse slice, 1 mm long, was cut just posterior to the esophagus and placed in fresh ice-cold fixative for 1 hr. The tissue was then removed and washed in phosphate buffer without additives (Millonig, 1961, 1962) for 16 hr at 8 C. Postfixation was with ice-cold 1% osmium tetroxide in phosphate buffer (Millonig, 1961, 1962) for 1 hr. Dehydration was by means of an ethanol series with two 15-min washes in propylene oxide. The tissue was infiltrated with a mixture of equal parts of propylene oxide and Araldite 502 mixture (Luft, 1961) for 16 hr at 25 C, followed Received for publication 6 May 1966. * This investigation was supported by Public Health Service Research Grant AI-02347 from the NIAID of the NIH. by several rinses of 2 hr each in Araldite 502 mixture. Polymerization was accomplished in a third change at 60 C for 24 hr. Thin sections were cut with glass knives using an LKB Ultratome and were picked up on naked 400-mesh copper grids. Contrast was enhanced by staining 20 min with each of two solutions, 1.5% uranyl acetate and lead citrate (Reynolds, 1963). Sections were examined and photographed at 50 kv in a Hitachi HU 11A electron microscope with initial magnifications up to 50,000 X.

The intestinal intermediate filament network responds to and protects against microbial insults and toxins.

Abstract: The enrichment of intermediate filaments in the apical cytoplasm of intestinal cells is evolutionarily conserved, forming a sheath that is anchored to apical junctions and positioned below the microvillar brush border, which suggests a protective intracellular barrier function. To test this, we used Caenorhabditiselegans, the intestinal cells of which are endowed with a particularly dense intermediate filament-rich layer that is referred to as the endotube. We found alterations in endotube structure and intermediate filament expression upon infection with nematicidal B.thuringiensis or treatment with its major pore-forming toxin crystal protein Cry5B. Endotube impairment due to defined genetic mutations of intermediate filaments and their regulators results in increased Cry5B sensitivity as evidenced by elevated larval arrest, prolonged time of larval development and reduced survival. Phenotype severity reflects the extent of endotube alterations and correlates with reduced rescue upon toxin removal. The results provide in vivo evidence for a major protective role of a properly configured intermediate filament network as an intracellular barrier in intestinal cells. This notion is further supported by increased sensitivity of endotube mutants to oxidative and osmotic stress.

A morphologic study of the ductus of the epididymis of Sus domesticus

Abstract: The head, body, and tail regions of the epididymal duct (or caput, corpus, and cauda epididymis) in two healthy and sexually mature Sus domesticus males were examined by light microscopy and by scanning or transmission electron microscopy. The epididymal duct is lined with a pseudostratified epithelium with stereocilia and covered by a muscular-connective tissue sheath that is thickest in the tail region. Diameter of the epididymal duct and height of epididymal epithelium are maximal in the head region. Length of the sterocilia and spermatic density are higher in the head and body regions. Somatic cells are abundant in the tail region. The epididymal epithelium is made up of five cell types: basal cells, principal cells, clear cells, narrow cells, and basophilic cells. Abundant secretory units are observed in the supranuclear cytoplasm of columnar principal cells. Each mature secretory unit is constituted by electron-dense secretion granules covered by more than eight layers of cisternae of reticulum between which the mitochondria are intercalated. In the apical cytoplasm the isolated secretion granules become larger and less electron dense. The apical surface is covered by numerous sterocilia. Basal cells are pyramidal and less high than principal cells. The clear cells, arranged between the principal cells, are characterized by the presence of abundant vesicular elements and electron-lucid secretion granules, and by an apocrine secretory process. The narrow cells are characterized by their highly vacuolized cytoplasm. Intermediate cell typologies can be found among basal, principal, clear, and narrow cells, which could be four developmental stages of the same cell type. The basophilic cells are spheroidal and are found at different levels between the epithelial cells and in the connective tissue underlying the epithelium. © 1993 Wiley-Liss, Inc.