Correlation between movement of concanavalin A membrane receptors and cytolysis. A scanning electron microscopy study

The present study was undertaken to test whether cytolysis induced by Concanavalin A (Con A) requires lateral mobility of membranal lectin receptor sites into caps. Treatment of interphase murine mastocytoma cells with 10(-4) M colchicine promoted cap formation by Con A in about 30% of the cells, followed by cytolysis. Pretreatment of the cells with NaN3, low temperature, or glutaraldehyde decreased the degree of capping and, to the same extent, the degree of cytolysis. The addition of antibodies to cells bound with Con A increased the appearance of capping and cytolysis. A linear relationship with a high correlation coefficient exists between the degree of capping and cytolysis, suggesting that lateral mobility of membrane Con A receptors is required for cytolysis by the lectin. The process of cap formation by Con A up to the stage of cytolysis was followed by scanning electron microscopy.     

A scanning electron microscope study of microvascular anastomoses.

The abdominal aortas of 30 rats were sutured under an operating microscope. The results were studied under a scanning electron microscope at 8 different periods after operation, ranging from 3 minutes to one month. The observations are presented.     

Cosmos pollen ontogeny: A scanning electron microscope study

Summary Ontogenetic data concerning pollen not only clarifies the mode of deposition of the elaborate walls but has considerable functional and taxonomic relevance. Hitherto such studies have used optical or transmission electron microscopy but here a recently devised preparative technique has enabled pollen development inCosmos bipinnatus to be studied using the scanning electron microscope. The technique involves freeze-fracturing of osmium fixed, cryoprotected anthers, maceration in dilute osmium tetroxide, critical point drying, sputter coating and examination. The processes of pollen wall development can then be observed in three dimensions, an important aid to understanding the spatial relationships involved in the determination of ornamentation and apertures. Details of the pollen and tapetum are described at various stages between meiosis and anthesis. A close conformity is demonstrated between the results obtained and those of earlier transmission electron microscopic studies of the same and related species although very different interpretations are made.     

A scanning electron microscope study of early sea urchin reaggregation

Sea urchin embryos were observed with SEM during the first 2 h of reaggregation, following dissociation of the 16-cell stage. A dense meshwork, composed of elongated microvilli embedded in the hyaline layer, surrounds the egg during early development. The dissociation procedure strips off some of the meshwork layer leaving fewer and smaller microvilli on the cell surface. Shortly after reaggregation has begun, several types of cell extensions are formed, including filopodia, which anchor the cells to the substrate, and ruffles and pseudopods, which enable the cells to move. Possible factors involved in the behavior of dissociated cells are discussed with regard to (1) the source of additional membrane in the formation of new cell extensions; (2) the ability of the cells to move.     

A scanning electron microscope study of human cerebral arteries.

Human cerebral arteries were obtained from autopsy, fixed under pressure, cut open, and tacked onto pieces of cork. For one artery the intima was partly teased away, exposing the media, and treated with a silver nitrate process. For another artery the adventitia was exposed. Both arteries were processed through graded ethanols and coated with gold paladium for the scanning electron microscope. The collagen fibers of the adventitia were approximately 5 mum in diameter and consisted of a bundle of microfilaments, each of which had a diameter of 800-1000 A (1 A = 10(-10) m). The collagen fibers were oriented parallel to the long axis of the artery. The muscle cells of the media had a diameter of 2-5 mum and were arranged circumferentially with a pitch of approximately 20 degrees. The collagen fibers of the media travel perpendicular to the muscle cells, and parallel to the long axis of the artery. The fibrillar components of the elastin in the intima had a diameter of approximately 700-1000 A and were arranged parallel to the long axis of the artery. It was postulated that the fibrillar part of the elastin was the elastic component of the elastin.     

A scanning electron microscope study of mouse peritoneal mesothelium.

As seen in the scanning electron microscope, peritoneal mesothelial cells of the mouse diaphragm, anterior abdominal wall and intestinal serosa carry numerous microvilli. These microvilli are absent over certain areas of the cell surface and are sometimes, interlocked in meshwork patterns or coronal formation. The apical cell membranes of the mesothelium at the base of the microvilli, are invaginated by many plasmalemmal vesicles and vacuoles and carry a number of protruding spherical structures. Deep circular craters, giving the impression of stomata, are also visible.     

A scanning electron microscope study of a microsporidian with a pansporoblast: Thelohania maenadis

Air drying is not adequate for the preservation of the pansporoblastic membrane of Thelohania maenadis (Protozoa, Microsporidia), a parasite of the crabs Carcinus mediterraneus and Carcinus maenas. Freeze-drying and critical point drying preserve the pansporoblast membrane and reveal that isolated spores of the microsporidian are covered with a thick hairy coat. This coat originates as secretory product within the pansporoblast cavity.     

A study of the budding ofSaccharomyces uvarum Beijerinck with the scanning electron microscope

Vegetative cells ofSaccharomyces uvarum Beijerinck in the exponential growth phase were examined with the scanning electron microscope. The existence of two types of scars — birth scars and bud scars — was confirmed. Birth scars had larger diameters than bud scars; both remained visible on old cells. The distribution of the buds on the mother cell did not appear to be a random one: there seemed to be a more or less emphasized cell polarity. The author wishes to thank Mr. Bert for technical assistance in the use of the scanning electron microscope.     

Glycosylation process in gonadotrophs: a quantitative electron microscope autoradiographic study with labeled glucosamine

Incorporation of [3H]glucosamine into dispersed anterior pituitary cells was studied by electron microscope autoradiography. Gonadotrophs were examined to determine the intracellular route and kinetic patterns of glycosylation. Studies were performed with cells from; (a) normal adult male rats; (b) rats orchidectomized 3 wk earlier; and (c) orchidectomized rats treated with tunicamycin. Our results show that incorporation of [3H]glucosamine first occurs in the rough endoplasmic reticulum (RER), then proceeds in the Golgi elements (where peripheral carbohydrates are attached). Treatment with tunicamycin results in a decrease in labeling of these 2 organelles. Comparison of the kinetic patterns in normal and castrated male rats shows that the accumulation of labeled glycosylated proteins in granules reaches a plateau within 2 hr post-pulse in normal rats, and rises during a 6-hr chase in castrated rats. However, because of the necessity for a rather long 15 min pulse, we cannot exclude the possibility that incorporation of glucosamine during the pulse may occur concomitantly in the RER and the Golgi saccules, to be followed by rapid transfer to the secretory granules.     

Fine structure of a periciliary ridge complex of frog retinal rod cells revealed by ultrahigh resolution scanning electron microscopy

We studied the junctional region between rod inner segments (RIS) and outer segments (ROS) in frog retinas by high resolution scanning electron microscopy (SEM). Retinas of dark adapted or light exposed Rana pipiens were critical-point-dried and RIS and ROS were split and coated with ultrathin metal films of niobium and chromium--or decorated with gold--and imaged in a new SE-I imaging mode. The connecting cilium (CC) usually broke at the base of the RIS and remained attached to the ROS. The outer part of the CC plasmalemma expanded to form liplike protrusions beyond which disks evaginated with successively larger diameter until they reached the full width of the ROS. The CC rose out from an invagination of the RIS apical plasma membrane (PM). On the lateral walls of this invagination, a highly ordered complex of nine symmetrically arrayed ridges and grooves rose steeply and extended laterally approximately 0.4-1 micron on the adjacent RIS PM. On the apical plasmalemma, the ridges and grooves formed groups of three to four parallel rows that surrounded the invagination. The grooves were bridged by filaments anchored at the top edges of the ridges. This highly ordered structure we term the periciliary ridge complex (PRC). Its ninefold symmetry apparently reflects the 9 + 0 microtubule organization of the CC axoneme. The three-dimensional structure revealed by SEM was confirmed by transmission electron microscopy (TEM) of sections of Epon-embedded retinas. TEM-immunocytochemistry on thin sections of retinas embedded in glutaraldehyde cross-linked albumin suggested that the PRC and the CC may participate in opsin transport and disk morphogenesis.     

Plant-microbial interaction under gnotobiotic conditions: A scanning electron microscope study

Inoculation of canola seeds withPseudomonas putida GR12-2 stimulates root elongation under gnotobiotic conditions. Transformation ofP. putida GR12-2 with the broad-host-range plasmid pGSS15 abolishes the enhancement of root elongation. With scanning electron microscopy it was found that both transformed and nontransformedP. putida GR12-2 are capable of binding to canola seed coats. In addition, it was observed that 4 days after the initial inoculation the roots of bothP. putida GR12-2- and GR12-2/pGSS15-treated seedlings were free of adhering bacteria despite the fact that it was subsequently shown that both bacterial strains are capable of binding to roots. Thus, adhesion to roots is not necessary for the initial phase of enhanced root elongation that is induced byP. putida GR12-2 under gnotobiotic conditions.     

Paraneuronal pseudobranchial neurosecretory cells in scorpion catfish Heteropneustes fossilis: an environment scanning electron microscope and transmission electron microscope study

Yadav, L., Sengar, M., Zaccone, D. and Gopesh, A. 2011. Paraneuronal pseudobranchial neurosecretory cells in scorpion catfish Heteropneustes fossilis: an environment scanning electron microscope and transmission electron microscope study. —Acta Zoologica (Stockholm) 00 : 1–8. Pseudobranchial neurosecretory system (PNS), found in the gill region of certain groups of teleosts, falls under the category of the ‘diffuse neuroendocrine system’ (DNES). The cells belonging to the system share morpho‐functional features with the paraneuronal cells observed in respiratory tract and airway surfaces of higher vertebrates. On the basis of the experimental observations, a role in condition of hypoxia has been recorded for this system. In an attempt to elucidate the ultrastructure of pseudobranchial neurosecretory cells, present investigation was undertaken using environment scanning electron microscope (ESEM) and TEM in an air‐breathing catfish, Heteropneustes fossilis. The external morphology of PNS under ESEM appeared as a mass of cells supplied with nerves and blood capillaries. Each cell mass is made up of numerous pear‐shaped neurosecretory cells, confirmed by neurosecretion‐specific acid violet stain. The TEM investigation of the cells revealed the presence of different sizes of dense‐cored vesicles in the cytoplasm, which was observed as granular cytoplasm under light microscope. Presence of large number of mitochondria in the cytoplasm confirmed active involvement of these cells in the physiology of fishes. Although lacuna prevails regarding the exact function of this system of fish, its probable role in hypoxic condition and surfacing behavior are speculated.