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At least 19 recordsLinked to original sources
PubMed1979

Morphological studies on the periostracum of the fresh-water mussel Amblema (Uniondae): light microscopy, transmission electron microscopy, and scanning electron microscopy.

The structure of the periostracum in the fresh-water mussel Amblema has been described using light microscopy, transmission elec;ron microscopy, and scanning electron microscopy. The structure and evolutive course of the periostracum was studied along its entire length, from the periostracal groove until it forms the tough outer covering of the shell. At least five structurally and functionally distinct regions were identified. In addition, the periostracum itself was seen to be a multilayered structure consisting of three major layers which are themselves subdivided into minor layers. From these morphological observations, a regulatory role for the various periostracal layers in mineral trapping, nucleation, and the subsequent formation of the prismatic and nacreous layers of the shell can be postulated.

Animals↗
PubMedDate not supplied

Observations on embryonic chick-bone crystals by high resolution transmission electron microscopy.

High resolution transmission electron microscopy of bone mineral at a vary early stage in its deposition in embryonic chick frontal bone demonstrates crystals of 2-2.5 nm thickness and a profile up to 40 nm long. They appear in groups which may show as few as one or two crystals. Associated with the crystals is a less dense amorphous material. Using specimen tilting, the change in crystal appearance indicates that crystals are tablet-shaped (rectangular) rather than rod-shaped. The amorphous material may be tablet-shaped crystals in orientations which are not dense enough to register as crystals in the image. Truly amorphous mineral does not show by bright-field electron microscopy, but preliminary results indicate that the dark-field technique may prove to be useful in imaging amorphous mineral provided that sections can be cut thinly enough and that precautions are taken during specimen preparation to avoid mineral loss. Crystals have been located in various parts of the osteoid zone and were not associated specifically with any one component. Rapid processing using anhydrous techniques must be used to avoid the possibility of artefactually altering the in vivo conditions of the mineral at the time of excision of the specimen.

Animals↗
PubMed1978

Pressure effects on flow channels in the lining endothelium of Schlemm's canal. A quantitative study by transmission electron microscopy.

A quantitative investigation, using transmission electron microscopy, was conducted to determine the relative incidence of nuclei, giant vacuoles and their pores, non-vacuolar transcellular channels and minipores in the endothelium lining the trabecular aspect of Schlemm's canal at various levels of intraocular pressure in the range 0--50 mmHg. The eyes of twelve rhesus monkeys were used and prior to intracameral fixation, the intraocular pressure was maintained at the appropriate level for one hour. The results obtained from a single section analysis showed that the incidence of giant vacuoles, vacuolar and non-vacuolar transcellular channels and minipores could be related to pressure. An analysis of serial reconstructions of samples of the vacuoles indicated that vacuolar transcellular channels became more numerous and more enlarged as pressure was increased. We concluded that the transcellular pore system serves as a major outflow route for aqueous humour.

Animals↗
PubMed1979

Comparative scanning and transmission electron microscopy of the prostatic gland in different species (mouse, rat, dog, man).

Man, dog, rat and mouse prostatic glandular cells were compared by light microscopy (LM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). In rodents and dogs, a merocrine secretion exists, and in these species the undulating surface represented a confluence of secretory granules. The prominent secretory blebs observed in dog and human benign prostatic hyperplasia (BPH) corresponded to apocrine secretions. Also variations in the amount of secretory activity were seen. Androgenic hormones were responsible for the differentiation of the prostatic epithelial cells during development. Therefore, an absence of microvilli as well as the appearance of ruffles, microplicae, and bare cells were seen in the prepuberal and castrated rat. In the elderly rat and in human BPH, a pleomorphism of the apical cell surface was evident.

Age Factors↗
PubMed1978

Positive detection of mycoplasma contamination by the whole-mount preparation of cell cultures for transmission electron microscopy.

Low-level mycoplasma contamination of cell cultures is difficult to recognize with presently available techniques. This report describes the adaptation of the whole-mount technique, usually used for scanning microscopy, for transmission electron microscopy. The differentiation between microvilli and the equal-sized filamentous mycoplasma is based on the differential density obtained by the use of the method described. This method allows positive identification of mycoplasma and reduces the preparation time and the time necessary for scanning the preparation.

Cells, Cultured↗
PubMed1979

[Study of an oral protozoan Trichomonas tenax using scanning and transmission electron microscopy].

The study with scanning and transmission electron microscopy of Trichomonas tenax gave morphological information on this protozoon. The oval-shaped cell body showed at the anterior pole four free flagella and a trailing flagellum which had an undulating membrane. The axostyle which consisted of microtubules and produced the cellular rigidity emerged at the posterior pole. An ovoid nucleus and a well-developed Golgi apparatus were located at the anterior pole. At the latter, a pelta consisting of horizontal microtubulus surrounding the kinetoplats from which started the flagella was also found. No mitochondria were observed: they were replaced by chromatin granules or hydrogenosomes. Numerous vacuoles and developing vesicles were found in the cytoplasm. Phagocytized bacteria were in an advanced stage of lysis. Others seemed intact showing even division phases.

Bacteria↗
PubMed1975

[Scanning transmission electron microscopy of dendritic spines stained by the Golgi method].

Scanning transmission electron microscopy of the dendritic spines of multipolar neurons in the cat inferior Colliculus was achieved on Golgi semi-thin sections. The three basic types of dendritic spines (ST, MS, TH) were identified. Scanning transmission electron microscopy provides a reliable method for a three dimensional view of these structures at high resolution and consequently a more accurate appreciation of their size. In addition, it could prove very useful in the quantitative analysis of the dendritic spines.

Animals↗
PubMed1977

Fixation of platelets for scanning and transmission electron microscopy.

A double fixation method of preparing platelet suspensions for both scanning and transmission electron microscopy is outlined. Prefixation in 0.1% glutaraldehyde allows for immediate preservation of morphologic characteristics induced by experimental procedures, but does not completely destroy platelet surface stickiness. Preservation of surface stickiness allows subsequent production of a platelet pellet for processing for transmission electron microscopy. This pelleting cannot be achieved when higher initial concentrations of glutaraldehyde are used for prefixation. Prefixation in 0.1% glutaraldehyde is also an appropriate initial step for preservation of platelets in suspension for scanning electron microscopy.

Blood Platelets↗
PubMed1979

Calcification in a pineal tumour studied by transmission electron microscopy, electron diffraction and x-ray microanalysis.

The calcification in a totally calcified pineal tumour was studied. Transmission electron microscopy indicated that the tumour was a pinealoma. The type of calcification was investigated by bright-field and dark-field transmission electron microscopy in addition to electron diffraction and electron-induced x-ray fluorescence. The calcified material consisted predominantly of amorphous calcium phosphate. The type of calcification differs from the normal calcification present in pineal acervuli which consists of crystalline hydroxypatite.

Brain Neoplasms↗
PubMed1979

A rapid technique for preparing microorganisms for transmission electron microscopy.

A rapid and efficient method of preparing microorganisms for transmission electron microscopy is reported. In developing the method Salmonella, streptococcal, and protozoal specimens were fixed with glutaraldehyde. After fixation cells are collected on a membrane filter, washed with buffer, postfixed with osmium tetroxide, then washed with distilled water and stained en bloc with uranyl acetate. Specimens are dehydrated using a graded series of acetone and then infiltrated with graded mixtures of acetone and Spurr embedding medium. Finally the membrane filter is cut into small pieces and embedded in fresh embedding medium polymerized in polyethylene capsules. By collecting and processing the specimens on membrane filters, numerous centrifugations are eliminated from standard procedures. The use of a low viscosity embedding medium allows for rapid infiltration and embedding of the specimen. Using this technique microbial specimens can be sectioned after less than 4 hours preparation.

Animals↗
PubMed1979

The fine structure of the hypostome and mouth of hydra. II. Transmission electron microscopy.

The normal morphology of the hypostome and mouth of hydra were examined by transmission electron microscopy with conventional thin sections and freeze-fracture replicas. Myonemes of the hypostome are small in diameter, have gap and intermediate-type cell junctions within each epithelial layer and are associated with the opposite epithelial layer by transmesogleal processes and gap junctions. Nematocysts and sensory cells are aggregated in the circumoral region. The fine structure of adherent flagella arising from gastrodermal gland cells, and the transition region at the mouth between epidermis and gastrodermis are described in detail for the first time. The possible functional significance of the findings is discussed.

Animals↗
PubMed1978

Methods of preparation of fossil bone samples for light and transmission electron microscopy.

The methods described make possible the preparation of fossil samples for light nad transmission electron microscopy. To obtain good images with ground sections of bone, both the grinding process and classical bone staining techniques were modified, the latter by staining already made ground sections. Ground sections of suitable thickness were etched with a 4:1 mixture of 5% HNO3 and 2% OsO4 at a lowered temperature, thereby obtaining isolated osteocytes with a complete network of processes. Using the same method with thicker ground sections, the contents of vascular canals were isolated. The contents retained spatial relations permitting complete reconstruction of the vascular system of the bone in question. The isolated osteocytes, the vascular canal contents, and the isolated remnants of the intercellular organic part of this bone, subsequently embedded in Epon 812 and in methacrylate, made possible sections suitable for detailed analysis of the image of the surfaces of these elements. Polished surfaces of the fossil bone were replicated by the so-called clearing replicas technique adapted to fossil bone. The latter facilitated analysis of the ultrastructure of the surfaces of the vascular canals, isolated osteocytes and their processes, and analysis of the immediate proximity of these elements, since the technique preserves the mutual spatial relations intact.

Animals↗
PubMed1979

Scanning and transmission electron microscopy of the blood-bubble interface in decompressed rats.

Scanning and transmission electron-microscopy have been applied for study of the ultrastructural features of the blood-bubble interface in the vasculature of explosively-decompressed rats. In scanning electron-microscopy, the surface facing the bubble appeared smooth, with slight undulation and frequent roundish protrusions. In cross sections of the material between the bubbles, there could be observed a continuous surface layer facing the bubble, a loosely-bound meshwork of fibrous material, and extreme congestion of erythrocytes. In transmission electron-microscopy there were found alignment of platelets along the interface, and a thin (10-20 nm) layer of osmiophilic material, in accordance with earlier ultrastructural studies. The platelets were often rounded. It is concluded that the initial phase of the blood-bubble interaction is the deposition of a plasma protein coat, followed by the attachment platelets, possibly related to activation of the coagulation system.

Animals↗
PubMed1979

Fine structure of the tegument of Mesocestoides tetrathyridia by scanning and transmission electron microscopy.

The tegumental surface of tetrathyridial stages of the tapeworm, Mesocestoides corti, was studied by scanning and transmission electron microscopy. Two structural types of microvilli were observed--blade-shaped or conical ones, and elongated, slender microvilli. The distribution and relative frequency of the two types of microvilli differs in different areas of the body surface. Host peritoneal cells were observed attached to the blade-shaped microvilli by slender cytoplasmic projections.

Animals↗
PubMed1979

Transmission electron microscopy of fetal rat brain cells during neoplastic transformation in cell culture.

Fetal rat brain cells were investigated by transmission electron microscopy during neoplastic transformation in long-term cell culture. Before transfer of the cells to culture, BD IX rat fetuses were treated with a single transplacental pulse of N-ethyl-N-nitrosourea (75 micrograms/g body wt) on the 18th day of gestation. During the early stages (3--4 mo), both glia-like and neuron-like cells were present in the culture, and after 2 months they formed complex aggregates ("nodules"). In contrast, corresponding secondary control cultures consisted of flat, epithelioid neural cells without neuron or astrocyte differentiation. After 3 months, cells with neuron morphology gradually disappeared. Some of the remaining cells contained many autophagosomes. After 5 months, rapid proliferation of rather homogeneous, glia-like populations was accompanied by reduction of microfilament bundles and microtubules, as well as atypical nuclei. Ability to form tumors upon sc implantation into syngeneic hosts was not observed until about 3 months later.

Animals↗