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 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 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 tarsal adhesive setae in the Coleoptera

Scanning electron micrographs of the tarsal adhesive setae of 84 species of beetle are described. These show a vast range of setal structure and distribution.     

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.     

A scanning electron microscope study of the pseudobranchs of two marine teleosts

The pseudobranchs of bass, Dicentrarchus labrax L. , and grey mullet, Liza ramada (Risso) ( Mugil capito ), were examined in the scanning electron microscope (S.E.M.). Both pseudobranchs appeared gill-like in situ but the S.E.M. revealed their gross morphology to be different. The bass pseudobranch was a'free' pseudobranch, having separate lamellae along the filaments, with areas of fusion on the leading edges of some lamellae, whilst the mullet pseudobranch was 'semi-free' since the secondary lamellae were fused over a large area and only free along their trailing (opercular) edge where the chloride cells were situated. The surface of the epithelial cells presented different patterns of microridges and microvilli depending on their position in the pseudobranch. Three types of cell opening were found at the cell surface, belonging to chloride cells, mucous cells, and possibly rodlet cells. The S.E.M. observations were correlated with those of transmission electron microscope (T.E.M.) studies.     

A scanning electron microscope study of the papilla basilaris of Gekko gecko

Summary The sensory hair cells of the ventral 2/3 of the papilla basilaris of Gekko gecko are divided into anterior (pre-axial) and posterior (post-axial) portions by a mid-axial gap or hiatus where there are no hair cells. There is no separation of the hair cells in the dorsal third of the papilla. There are three tectorial membrane modifications: an attached thickened membrane covering the pre-axial hair cells, sallets covering the post-axial hair cells, and an attached filamentous membrane covering the dorsal hair cells. The number of hair cells is greatest ventrally and decreases dorsally. There are approximately 2000 to 2100 hair cells. The kinocilia of the hair cells of the anterior halves of both the pre- and the post-axial vertical hair-cell rows are oriented posteriorly, while the kinocilia of the posterior halves are oriented anteriorly. The kinocilia of the hair cells of the dorsal third of the papilla are mostly oriented posteriorly. Thus, kinocilial orientation of the ventral 2/3 of the papilla is doubly bidirectional, and the dorsal 1/3, largely unidirectional.I would like to thank Ms. Maria Maglio for her skill in handling the technical aspects of the scanning electron microscopy as well as her artistry in achieving photographic excellence on the scope, David Akers for expert photographic assistance, and Wayne Emery for the drawings. Research sponsored by United States Public Health Service Grant NS-09231.