Scanning electron microscope studies of some skink papillae basilares

Summary The papilla basilaris of scincid lizards is relatively long, slightly curved or bowed, and characteristically has an apical terminal expansion. A limbus-attached tectorial membrane is present but is apparently not continuous with the tectorial material covering the hair cells of the papilla. The hair cells of the apical expansion are covered by a thick spongy mass of tectorial material, while the hair cells above (dorsal to) the apical region are covered by thickened tectorial material that is in the form of uniquely sculptured, twisted or folded drape-like masses (sallets). The surface of the basal (dorsal) quarter of the papilla is unusual in that it is concave rather than convex. The expanded terminals of the hair cell kinocilia are also unusual in being arrowhead-shaped.Kinocilial orientation of the non-apical papillary hair cells is simply bidirectional; the hair cells on each side of the papillary axial midline are oriented toward the midline. Kinocilial orientation of the hair cells of the apical expansion is more complex with the peripheral neural and abneural rows both being abneurally directed, and the central rows being at first neural in orientation, but becoming abneurally oriented as the apical tip is approached. At the apical tip region, most all hair cells are abneurally oriented.I would like to thank Ms Maria Maglio for her skill in handling the technical aspects of the electron microscope, Mr. David Akers for expert photographic assistance, and Ms. Michiko Kasahara for aid in all aspects of the work. Research sponsored by United States Public Health Service Grant NS-09231.     

Further electron microscope studies of the conidium of Alternaria brassicicola

Summary The freeze-etching technique, aldehyde fixation and heavy metal shadowing of wall material were used in an electron microscope study of the maturing spores of Alternaria brassicicola (Schw.) Wiltshire. The walls are composed of fibres, probably of chitin. The plasmalemma has rectangular grooves in its outer surface and corresponding ridges on the inner one; both surfaces bear particles of two distinct sizes. Endoplasmic reticulum may be lamellated or vesicular and its involvement in wall formation is confirmed; vesicles produced by the endoplasmic reticulum fuse with the plasmalemma. The structure of nuclei, mitochondria and vacuoles is also demonstrated.     

Light and electron microscope studies on ovarian follicles in the lizard Chalcides ocellatus

The development of ovarian follicles in a skink has been studied with light and electron microscopy. In early stages the previtellogenic oocyte has a follicular covering (granulosa) comprising only two cell types, small cells and pyriform cells. A complex microvillous interdigitation between follicle cells and oocyte is present from very early stages but regresses as a mature size is reached. The outer thecal layer differentiates into distinct interna and externa as growth proceeds. Occasional biovular follicles are formed. Pyriform cells establish direct continuity with the oocyte via cytoplasmic bridges which traverse the layer of microvilli interdigitating in the zona pellucida. Such bridges appear most frequently just before the onset of yolk deposition; the organelles and cytoplasmic constituents presumed to be transferred across them may stimulate this activity. As the follicles grow, the pyriform cells shrink and disappear to leave just the small cells forming the single layered granulosa. There is asynchrony in recruitment and/or early growth rates of follicle crops and uniformity of oocyte size appears only as vitellogenesis nears completion (with up to five oocytes, about 1 cm in diameter, on each side). Yolk deposition may involve transformation of golgi vesicles or pinocytotic vesicles but there is no evidence to show mitochondria as foci for deposition.     

Biological applications of the scanning transmission electron microscope

The STEM has the capability to acquire spatial and chemical information from almost all scattered electrons. Dedicated STEMs do not have any post-specimen lenses but many different detectors instead.The STEM axial bright field mode is quite insensitive to multiple scattering occurring while imaging thick samples such as vitrified whole cells. The blur of small gold sphere has been simulated by Monte Carlo calculations.Direct electron detectors record the rich information of microdiffraction patterns from every irradiated spot while the STEM beam raster-scans over the sample.

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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.     

Examination of several selected fungi by scanning electron microscope

Scanning electron microscopy with high resolution and great depth of focus has been known to be able to show the fine features of surface ornamentation of fungi, and with this technique we could obtain the interesting results about the surface structures of the selected fungi,Penicillium chrysogenum, Aspergillus niger, Aspergillus oryzae andCandida utilis.     

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.     

Blood vascular architecture of the rat lingual papillae with special reference to their relations to the connective tissue papillae and surface structures: a light and scanning electron microscope study

Subepithelial blood vessels of the rat lingual papillae and their spatial relations to the connective tissue papillae and surface structures were demonstrated by light and scanning electron microscopy. In the rat, four types of papillae were distinguished on the dorsal surface of the tongue, i.e. the filiform, fungiform, foliate and circumvallate papillae. Vascular beds of various appearance were found in all four types of lingual papillae: a simple or twisted capillary loop in the filiform papilla; a basket- or petal-like network in the fungiform papilla; a ring-like network in the foliate papilla, and a conglomerated network surrounded by double heart-shaped capillary networks in the circumvallate papilla. These characteristic vascular beds corresponded to the shape of the connective tissue papillae and surface structures. The vascular bed beneath the gustatory epithelium in the fungiform, foliate and circumvallate papilla consisted of fine capillary networks next to the taste buds.     

A scanning electron microscope technique for restoring deformed fossils

Deformed fossils which originally had a regular geometric outline, such as crinoid columnals, can be restored using a scanning electron microscope technique called tilt correction. This magnifies the specimen in one direction only. It is unsuitable for specimens where deformation has occurred unevenly and can also distort small structures while restoring the whole specimen. D Crinoid columnals, scanning electron microscope, tilt correction.     

Mammalian fertilization as seen with the scanning electron microscope

For several years we have been looking at mammalian gametes and their interactions with the scanning electron microscope (SEM). Examining the images produced by the SEM has given us a three-dimensional view of sperm, eggs, and egg investments. We are particularly impressed with the structural variation among gametes of different mammalian species. In this short report we examine the structure of mammalian spermatozoa, eggs, zonae pellucidae, and cumuli. Our observations and those of others have led us to believe that variation in gamete structure and function may have evolved as a mechanism for reproductive isolation of mammalian species.     

Observations on estuarine microfouling using the scanning electron microscope

Scanning electron microscopy was used to observe microbiological primary fouling of glass surfaces exposed in estuarine waters. Observations on clean glass, and glass treated with water-repellent coatings, showed that bacterial slimes adhered less strongly to the waterrepellent glass. An experiment using pure cultures of bacteria and latex particles showed that attached bacteria promoted the settlement of latex particles on the glass.     

Toxoplasma Gondii: scanning electron microscope studies on the small intestine of infected and uninfected cats

The mucosal surfaces of villi from the small intestine of cats infected with Toxoplasma gondii were studied with the scanning electron microscope and compared with those from uninfected control cats. In uninfected cats villi were predominantly leaf shaped and were lined with ridges; goblet cell openings could be seen. The enterocytes had a hexagonal surface outline and were dome-shaped. Infected cats had both normal and abnormal villi. Injured villi were shortened and attained a broad leaf shape, often with blunt edges. Enterocytes containing oocysts were enlarged, and microvilli were resolvable only on these surfaces. Ruptured cells from which parasite discharge had occurred were seen. Oocysts were observed and possessed a smooth coat.