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 study microscope of the gills of the lamprey,Lampetra fluviatilis (L.)

The gills of larval and adult lampreys were fixed in 0.1, 5.0 and 25.0% glutaraldehyde and studied with the scanning electron microscope. The secondary lamellae, which alternated on either side of the filaments, were enlarged at their free edge, a feature probably related to the presence in this region of marginal blood vessels. After fixation in 5.0% glutaraldehyde, the surface of the secondary lamellae were seen to be covered with a thick layer of mucus. Only isolated clumps of mucus were present, however, at the very low and very high concentrations of glutaraldehyde and at 0.1%, which yielded the best fixation, it was often virtually absent. Prominent raised edges separated the adjacent cells, and on the cell surface could clearly be detected a mass of short convoluted low microridges. Pores were occasionally observed at the junction of epithelial cells. These are believed to correspond to the apical surface of mucous cells, a view supported by the presence of individual plumes of mucus in these regions of the lamellar surface. It is suggested that fixation with 5.0% glutaraldehyde stimulates discharge of the mucus cells and that mucous is not normally present as a thick layer over the gill epithelium. If this is the case, the microridges increase the surface area by 1.8 times and would produce a very localized area of microturbulence at the cell surface thereby facilitating gaseous exchange.     

A scanning electron microscope study of the mesothoracic and metathoracic scolopophorous organs of Lethocerus (Belostomatidae-heteroptera)

The presence of scolopophorous organs in aquatic Heteroptera has been reported in a number of species. This study presents a morphological investigation of these sensory structures of Lethocerus (Belostomatidae) as observed with the scanning electron microscope (SEM). Paired mesothoracic and metathoracic organs are present. Externally, each sensory structure consists of a raised sensory membrane. The distal-most portion consists of thickenings of this sensory membrane (sclerite). The receptor neurons of the mesothoracic organ are of two types—one discolopidial sensillum and 12 monoscolopidial sensilla. The former is attached to the internal wall and distal thickening of the sensory membrane, while the latter are dispersed throughout the interior and attached to the internal wall of the sensory membrane. The structure of the organs suggest that an effective stimulus could be a compression of the membrane. A discussion of possible functions (pressure reception and hearing) is included.     

Cornea of ommatidia in Lepidoptera (Insecta)--a scanning electron microscope study

The external surface of facets of representatives of 19 families of Lepidoptera is discussed and illustrated. Two types of structures are recognized, this with nipples predominate. The other structures (pleats) developed probably in the course of a reduction. The ultrastructure of surface in the form of granulation is described.     

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 the stem structure in the West African Cane Palms (Calamoideae)

The canes of thirteen rattan taxa comprising two Calamus, three Eremospatha, five Laccosperma and three Oncocalamus were studied anatomically by scanning electron microscopy (SEM). Six out of the taxa tagged L. secundiflorum a, b, c; Oncocalamus sp. d, Oncocalmus sp. e and Calamus sp. f were unresolved herbarium voucher specimens many decades old. SEM photomicrographs revealed cell‐tissue specific differences in anticlinal cell wall of the epidermis, fibrous sheaths, sheath parenchyma and phloem strands, leaf traces, and vessel diam‐ eter. Metaxylem vessel diameters varied between 20–212 µm in the outer peripheral zone and 90–310 µm in the central cylinder, except in L. secundiflorium c where the trend is reversed. Regression analysis of the metaxylem diameter values along radial distance shows large interspecific differences from central to outer cylinder. The weak R² values (P ≤ 0.5) in nine of the thirteen species suggests that other unmeasured variables contribute to the observed trend. The structure of the unresolved voucher specimens appear to follow the same general trend in the identified specimens suggestive of phenotypic divergence between po‐ pulations brought about by developmental plasti‐ city. The leaf trace observed in Oncocalamus sp. e is unique and deserved to be examined more closely. A simple arithmetical expression indicat‐ ing structural synergy between protoxylem and metaxylem for possible volume ratio balance is included. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

An electron microscope study of the tegument of Hunterella nodulosa Mackiewicz and McCrae, 1962 (cestoidea: Caryophyllidea)

Ultrastructural observations using transmission and scanning electron microscopy reveal the tegument to be basically similar to that of other cestodes. The syncytial distal cytoplasm is devoid of organelles except for rod-shaped bodies, believed to be secretory vesicles, and lamellated bodies which probably contribute the raw material for new microtriches. There is evidence that these vesicles originate from the Golgi found in the sub-cuticular cells.Three types of microtriches are described: typical ones with well-developed spines, ones with short filaments instead of spines, and ones with no spines. Microtriches with spines are found only on the anterior part of the worm and may serve to anchor the worm. Microtriches on the posterior have no spines and are believed to be primarily involved in the absorption of nutrients. Between these two regions there is a transitional zone where all three types of microtriches can be found. In general the microtriches are quite uniformly distributed throughout the surface of the worm. The presence of cestodarian-like microtriches raises interesting evolutionary questions.Histochemical tests localized acid and alkaline phosphatase activity on various parts of the tegument, as well as on host intestine, while acian blue tests showed that acid mucopolysaccharide levels correspond with the concentration of the tegument vesicles.     

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.