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Query: UMLS:C0276640 (TEM)
 20,729 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The relevance of the continuum method for a quantitative X-ray microanalysis of epon embedded tissue sections in the particular conditions offered by the Camebax-TEM system was tested and an improved model of specimen holder is proposed. The absolute calcium concentration [Ca] of membrane-bound intracellular glio-interstitial granules was determined by X-ray microanalysis in transmission electron microscopy of Mytilus retractor muscle. The Ca peak and background values were measured by the wavelength-dispersive spectrometer of the Camebax; the mass thickness of the section was recorded simultaneously with an added energy-dispersive detector. The tissue was frozen at approximately equal to 77 K in a mixture of liquid propane and butane, freeze-substituted in the presence of oxalic acid and embedded in epoxy resin. The calcium concentration of glio-interstitial granules can be as high as 180 mmol.kg-1 of epoxy-embedded tissue, with an average of 40 mmol.kg-1. The sampling of the data through repeated experiments is discussed and it is proposed that the cell would be the main level of variation. The Ca content of glio-interstitial granules is significantly lower in the tissues of animals submitted to high-potassium artificial sea-water for 10 min. This finding was predicted by the hypothesis that glio-interstitial tissue is a regulator of calcium concentration in extracellular spaces.
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PMID:Quantitative X-ray microanalysis of calcium with the Camebax-TEM system in frozen, freeze-substituted and resin-embedded tissue sections. Application to molluscan glio-interstitial granules. 369 21

Male Wistar rats were treated by ethylene glycol (0.8 Vol% in water) or a diet low in magnesium (70 mg/kg). The intrarenal crystallisation and stone formation of calcium oxalate was investigated by SEM, TEM and energy dispersive X ray analysis. The first stage in crystallisation was amorphous deposits of calcium surrounding microvilli of the lower part of the nephron, followed by multicentric, intratubular calcium crystals. Finally calcium plaques of the papilla seemed to be precursors of the urinary stone.
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PMID:[Intrarenal calcium crystallization. An electron microscopy study]. 371 39

A 2.45-GHz microwave exposure facility was developed for long-term TEM irradiation of cellular monolayers. Culture flasks with cells attached to the inside bottom surface were filled with medium, submerged in a 60 X 60 X 12-cm water bath on the field central axis, and exposed in the far-field 2 m below the ceiling-mounted antenna. A quarter-wave transformer plate increased the power transmitted into the water bath, and treatment temperatures were maintained by closed circulation with an external temperature control reservoir. Power density mapped below the quarter-wave plate indicated uniform TEM fields in the 25 X 25-cm region where flasks were located. With 1 kW of forward power to the antenna, the SAR [W/kg] = 45 exp(-0.607d) where d [cm] is the depth in water at any point within this area.
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PMID:Far-field 2.45 GHz irradiation system for cellular monolayers in vitro. 385 49

The osmotic behavior of control lymphocytes (CL) and polymorphonuclears (CPMN) was compared with that of cells from patients with chronic lymphocytic leukemia (CLL) and chronic myelocytic leukemia (CML), using the method of gradual dialysis against distilled water. The results were evaluated with a fragiligraph, and by scanning (SEM) and transmission (TEM) electron microscopy. The fragiligraphy curves showed that CLL cells are more resistant to osmotic pressure than the CL, whereas the curves for CPMN and CML cells showed an overlap. Surface alterations in CL appeared as early as 1 min of dialysis, while in CLL cells the membrane did not show major alterations even after 5 min of dialysis. CPMN also showed alterations earlier than CML cells, but this difference was not as prominent as in the case of lymphocytes and was observed for a maximum of 3 min of dialysis. The internal structure of the cells was altered earlier than the surface membrane and this was expressed mainly in the nucleus in both control and leukemic cells. Also in this respect, the internal structure of CL was altered earlier than that of CLL cells, whereas no major differences were observed between CPMN and CML cells.
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PMID:SEM and TEM studies on the osmotic behavior of control and leukemic lymphocytes and polymorphonuclears. 612 53

To resolve discrepancies between its enzymological activity and its in vitro or in vivo activity, 6-acetylmethylenepenicillanic acid (Ro 15-1903), a potent beta-lactamase inhibitor, was investigated for its chemical stability and its ability to penetrate the bacterial cell envelope. Although Ro 15-1903 was fairly stable in water or saline, it was found to be unstable in a rich medium, in mouse plasma and in human serum. Decomposition half-lives in Tryptic Soy Broth (TSB) and mouse plasma were determined by spectrometry to be 1.3 hours and 12 minutes respectively. These values were confirmed by a biochemical method for determination of Ro 15-1903. Furthermore, a large enhancement of the in vitro activity was noticed when the assay medium was changed from TSB to a synthetic medium in which Ro 15-1903 was more stable. The ampicillin-potentiating activity marginally increased if a permeability mutant harboring the R6K plasmid, which codes for TEM-1 beta-lactamase production, was used instead of the wild-type strain. These results prove that the chemical instability of Ro 15-1903 is the main cause of its disproportionally low activity in vitro and in vivo. Ro 15-1903 is not nonspecifically inactivated by proteins, since it did not lose its activity after incubation with bovine serum albumin (50 mg/ml) for 2 hours at 37 degrees C. It seems to react specifically with beta-lactamase.
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PMID:Studies on 6-acetylmethylenepenicillanic acid (Ro 15-1903). III. Relationship between in vitro activity and chemical stability. 631 68

The preparation and high resolution observation of frozen hydrated thin sections has been studied by transmission electron microscopy (TEM and STEM) on model systems, including pure water, protein solutions, catalase crystals, myelin sheath and various tissues. The state of the ice is determined by electron diffraction. Mass measurement in the electron microscope is used to determine section thickness and control hydration. An adequate depth of vitrified material for sectioning can be obtained from many biological suspensions or untreated tissues. Frozen hydrated sections around 100 nm thick can be produced under optimal conditions from vitreous ice or from vitrified biological samples. Sectioning, transfer and observation in the electron microscope is feasible without alteration of the sample hydration or its initial vitrification. Biological structures can be preserved and observed down to 10 nm. Under favourable working conditions, specimen compression during sectioning and electron beam damage are the factors limiting high resolution observations.
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PMID:Electron microscopy of frozen hydrated sections of vitreous ice and vitrified biological samples. 635 May 98

The fine-structural analysis of injuries and injury-related damages of the arteries in the head and neck region, such as vital endothelial injuries resulting from death by hanging, is of considerable importance in legal medicine, as it involves numerous forensic problems. The problems and difficulties of vessel preparation, including the occurrence of artefacts, have been widely discussed in medical journals, indicating the necessity for a special method of preparation to be developed. This method has to take individual differences of the autopsy material into consideration, including osmolarity changes caused by hypoxia, and autolysis. The method developed by us and described here meets these conditions. Optimization and standardization of the method was achieved by perfusion fixation of the vascular system in situ. The particular characteristics of the vessels involved made it necessary to open the skull. After removing the upper half of the brain and applying a partially permeable sealing to the skull base, we proceeded with the perfusion, using slightly hyperosmotic perfusion media (450-680 mOsm) via a hydrostatic system, and keeping pressure and flow rates low (max. 65 cm H2O). The perfusion technique we developed, and which is described in detail, has proven suitable for the preparation of other vessels as well, which is demonstrated on the venae cerebri superiores. The method of preparation was designed to provide conditions for a routine application of SEM, LM and TEM for forensic purposes.
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PMID:A preparative technique for morphological analysis of the vessels in head and neck for medico-legal examinations. 636 17

A method for preparing and handling large, clean, distortion-free cut surfaces through small and delicate tissues for correlated SEM/TEM examination is described. In this method, tissues are fixed according to conventional protocols; however, instead of critical-point-drying after fixation, tissues are first embedded in polyethylene glycol (PEG), a water-soluble waxy solid. Tissue blocks are easily oriented and sectioned to the desired regions, immersed in a solvent to remove PEG, critical-point-dried, and examined with an SEM. The same tissue blocks can be reworked for TEM by immersing in propylene oxide and embedding in an epoxy resin.
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PMID:A method for exposing the internal anatomy of small and delicate tissues for correlated SEM/TEM studies using polyethylene glycol embedding. 636 35

Microanalytical experiments have been performed to answer the question whether the main cellular cation, K+, follows the water distribution in the striated muscle cell or whether K+ follows the distribution of negative fixed charges (beta- and gamma-carboxyl groups of aspartic and glutamic acid residues). Subcellular localization of K and/or of the K surrogates Rb, Cs, and Tl has been investigated by the following methods: Chemical precipitation of K with tetraphenylborate. Autoradiography of alkali-metals and Tl in air-dried and frozen-hydrated preparations. TEM visualization of electron dense Cs and Tl in sections of freeze-dried and plastic embedded muscle. X-ray microanalysis of air-dried myofibrils and muscle cryosections. The experiments consistently show that K, Rb, Cs, and Tl do not follow the water distribution but are mainly accumulated in the A band, especially in the marginal regions, and at Z lines. The same sites preferentially accumulate Cs or uranyl cations when sections of freeze-dried, embedded muscle are exposed to these electron microscopic stains. It is concluded that the detected uneven distribution of K, Rb, Cs, and Tl in muscle is neither a freeze-drying artifact nor an embedding artifact and may result from a weak ion binding to the beta- and gamma-carboxyl groups of cellular proteins.
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PMID:Subcellular distribution of potassium in striated muscles. 648 3

The structure of the acini in the swine sweat gland is described here at the TEM level. The acini of the sweat gland in the pig is formed by 2 secretory cell types: dark seromucous cells and clear cells. The dark seromucous cells are actively secretory and their secretion is apocrine. The clear cells seem to be involved in an active transport of water and electrolytes through their cytoplasms.
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PMID:The fine structure of the swine sweat gland. I. The acini. 672 Dec 13


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