Detection and analysis of tracers in experimental drowning

In animal experiments, studies on the mechanisms involved in drowning were carried out using latex and gold tracers of defined size and concentration. The tracers were detectable by fluorescence microscopy (latex tracers) and by electron microscopy (gold tracers) in the lungs, kidneys and lymph nodes and were analysed further by X-ray microanalysis using a transmission scanning electron microscope. Tracers with small diameters were shown to penetrate intercellular gaps of the alveolar epithelium and the larger tracers were incorporated into the epithelial and endothelial cells by active pinocytotic mechanisms thus passing through the air-blood barrier. The detection and analysis of tracers in organs of the systemic circulation originating from the immersion fluid can assist in understanding the pathophysiology of drowning and in some selected cases, in making a more definitive diagnosis.

Structural relationship between the primary crystal formations and the matrix macromolecules in different hard tissues. Discussion of a general principle

For many years we have investigated the earliest crystal formations of different developing hard tissues (matrix vesicle, bone, dentine, enamel, etc.) by different electron microscopic measurements. It was observed that primarily Ca-phosphate (apatite) "chains," composed of nanometer sized particles (dots, islands), exist, which coalesce rapidly to needles. For the mineralization of collagen (e.g., bone, dentine) the center to center distances between the dots in the mineral chains represent the distances between nucleating sites, so-called "active sites" of collagen which bind primarily Ca for a subsequent nucleation. For the mineralization of noncollagen macromolecules (e.g., enamel) the same principle of mineral nucleation at such "active sites" exists being represented indirectly by corresponding center to center distances between the dots in the mineral chains.

Biological evaluation of an ionomeric bone cement by osteoblast cell culture methods

Periosteal derived bovine osteoblast-like cells migrated in culture onto an ionomeric cement. Cell cultures were maintained for 4 weeks and used to study the in vitro behaviour of cells on the ionomeric bone cement (IC). The cells produced bone matrix proteins (osteocalcin, bone sialoprotein II) and were osteoblast-like. The osteoblast-like cells colonized the substrate in monolayers and produced an extracellular matrix as seen by light and scanning electron microscopy. Morphological comparison between cells growing on the ionomeric bone cement and cortical bone revealed no significant difference in phenotypic expression. Staining for aluminium in osteoblasts growing on the IC showed an uptake and storage of aluminium in the cells. Energy dispersive X-ray microanalysis revealed high concentrations of aluminium and silicon in the periosteal tissue. Despite the known toxic effect of aluminium in vivo and in vitro on osteoblasts, no signs of toxicity were apparent on light and scanning electron microscopy analysis.

Analysis of early hard tissue formation in dentine by energy dispersive X-ray microanalysis and energy-filtering transmission electron microscopy

Thin cryosections and sections of embedded tissue were prepared from dentine of cryofixed rat incisors. Energy dispersive X-ray microanalysis (EDX) and electron energy-loss spectroscopy (EELS) have been applied to study the calcium and phosphorus distribution in predentine of these incisors. A small enrichment of calcium and phosphorus was found in the predentine zone near the dentine border. Element distributions were correlated with analyses of the early crystal formation in dentine. These investigations were carried out by parallel applications of electron spectroscopic diffraction (ESD) and electron spectroscopic imaging (ESI) using zero-loss filtering. It was found that the earliest crystal formations already showed the lattice of the hexagonal mineral apatite. They form parallelly arranged chains of dots which coalesce rapidly to form "needle-like" crystallites along the collagen microfibrils.

Analysis of the calcium distribution in predentine by EELS and of the early crystal formation in dentine by ESI and ESD

Predentine is a collagen-rich extracellular matrix between the odontoblasts and the dentine with a width of about 15-20 microns. Electron energy-loss spectroscopy of rat incisors shows a significantly higher calcium content in the predentine at the predentine-dentine border than in the middle region of the predentine. At the predentine-dentine border in the dentine, the calcium and the phosphate groups combine to form apatite crystallites. Electron spectroscopic diffraction with zero-loss filtering revealed that the earliest crystallites contain only Debye-Scherrer rings of apatite, which are fewer in number and more diffuse than the diffraction rings from the mature crystallites. We therefore conclude that the early crystallites still contain lattice defects, which are annealed out to some degree with crystal growth. Electron spectroscopic imaging with zero-loss filtering also showed that the earliest crystallites are chains of dots (or small islands); they build up strands composed of islands, which rapidly acquire a needle-like character and coalesce laterally to form ribbon-or plate-like crystallites. The parallel strands sometimes appear to reinforce the macroperiod of the collagen microfibrils (67 nm) by tiny holes without any crystal-substance lined up perpendicular to the parallel strands of the crystallites.

Electron spectroscopic diffraction and imaging of the early and mature stages of calcium phosphate formation in the epiphyseal growth plate

A review of different models of biomineralization in collagen-rich hard tissues shows that further investigations of crystal formation are necessary. The electron spectroscopic diffraction (ESD) mode of operation of an energy-filtering electron microscope offers the possibility of being able to avoid the background from inelastic scattering in selected-area electron diffraction patterns. First experiments on the different stages of mineralization in the epiphyseal growth plate have only indicated the presence of apatite. The ESD mode can be complemented by the electron spectroscopic imaging mode and by elemental mapping of calcium.

Microprobe analyses of the potassium-calcium distribution relationship in predentine

Apex regions of continuously growing incisors of Wistar rats were quickly dissected, shock-frozen in liquid nitrogen-cooled propane, freeze-dried at -80 degrees C and infiltrated with Spurr's resin. 400nm thick dry sections were cut with a diamond knife on an ultramicrotome. Relatively flat sections were transferred with an eye lash onto collodium coated aluminum grids. They were flattened with a glass stick and by placing another collodium coated aluminum grid just on top of the first one, exerting a uniform pressure. After carbon coating the sections were observed using the backscattered and secondary electron signals in a scanning microscope. The predentine was analyzed for calcium and potassium with an energy dispersive x-ray analysis system. The x-ray spectra revealed in the predentine regions with beginning dentine formation, near the apex, an uneven K-distribution with very low as well as more prominent x-ray peaks. The K peaks were always lower than those of calcium. In areas with advanced dentine formation, prominent K-peaks were always observed. They were normally higher than the Ca-peaks up to a distance of 5-10 microns from the dentine border. Closer to the dentine border the K concentration decreased while the Ca-peak increased. This might indicate that (besides Na) K is used to balance the negative charges of the macromolecules till K is replaced by Ca at the onset of apatite crystal formation.

Electron probe X-ray microanalysis of calcium and phosphorus distribution in developing hamster tooth germs in vitro and in vivo

The aim of the present study was to investigate the spatial distribution of Ca and P in dentin and enamel of developing first (M1) and second (M2) maxillary hamster molars (age: 3-5 days) in comparison with cultured molars. For culturing the germs were dissected from 3-day-old hamsters and incubated for 1 and 2 days, respectively, in a modified BGJb medium. Electron probe X-ray measurements were carried out on 3 regions extending in a vertical axis from cusp tip over cusp middle to cusp base next to the cervical loop region. Neither the in vivo nor the in vitro group was statistically different in the Ca and P concentration in the regions of dentin. In both groups the measurements in enamel showed a gradient with an increase in Ca and P from enamel surface towards dentin-enamel junction and a gradient with an increase from cusp base towards cusp tip. Direct comparison of the in vivo group with the in vitro group did not demonstrate a statistical difference between the mineral content of the 4-day-old germs and the 1-day culture germs, respectively the 5-day-old germs and the 2-day culture germs. The results indicate a high correspondence between the mineralization process of in vitro and in vivo tooth germ development.

Electron-microscopic and microprobe analyses on the pigmented and unpigmented enamel of Sorex (Insectivora)

Sorex belongs to the Insectivora and has a pigmented tooth enamel due to iron. The pigmented enamel (PE) has a mean Ca/P weight ratio, analyzed by quantitative electronprobe X-ray microanalysis, of about 1.9 (mean molar Ca/P ratio 1.46), and the unpigmented enamel (UE) a Ca/P weight ratio of about 2.0 (mean molar Ca/P ratio 1.59). The PE has a higher iron content (with a value of about 8%) than the UE, as shown by microanalysis of ultrathin sections. Laser microprobe mass analysis (LAMMA) has shown that the carbonate content in the UE is higher than in the PE. In the LAMMA spectrum of the negatively charged ions the carbonate lines could be compared directly with those of negatively charged iron ions. The pigmentation is associated with a low Ca/P ratio but may transfer mechanical strength and acid resistance strength to the PE.

Size dependent enzyme activities of multinucleated (osteoclastic) giant cells in bone tumors

In osteoclastic giant cells of six different tumors of bones and joints (fibrous dysplasia, proliferating giant cell tumor, malignant giant cell tumor, osteosarcoma after chemotherapy, malignant synovioma and Ewing's sarcoma) activities of tartrate-resistant acid phosphatase, NADH-tetrazolium-oxidoreductase and, in three of them, of non-specific esterase are determined by enzyme histochemical methods. Quantitative microphotometry makes it possible to determine relative enzyme activities in the cut sections of giant cells of different sizes. Giant cells of the various tumors reveal similar trends: With an increase in cell size, mean extinctions of NADH-tetrazolium-oxidoreductase and non-specific esterase decrease. Mean extinctions of tartrate-resistant acid phosphatase increase in cells of medium size, whereas the large cells reveal in part low activities. An additional ultrastructural examination of the giant cells in the proliferating giant cell tumor as well as in the osteosarcoma shows morphological signs of degeneration in the large cells. Electron probe microanalysis of the proliferating giant cell tumor exhibits evidence of phagocytosis of Ca and/or Fe containing particles. The similar size dependent reaction pattern of enzymes in osteoclastic giant cells of different tumors favors the concept of a common histogenesis, i.e. a host reaction.

Potassium concentration in membrane-associated particles in the epiphyseal growth plate

Electron-dense particles with a diameter of 50-200 nm have been observed at the cell membrane of chondrocytes in the zone of the initiation and advance of mineralization, using the dark field STEM mode. Electron-probe x-ray microanalysis and laser microprobe mass analysis indicate that these particles contain predominantly K and Na. They appear only in dry thin sections of shock-frozen, freeze-dried embedded tissue and not in sections of water-treated samples; hence they contain water-extractable potassium and sodium. The function of the two elements at these special sites is not yet clear. On the one hand, they might reflect exocytotic processes connected with a Na-K-ATPase; on the other hand, they might exist as a transitory state before being replaced by Ca and phosphate in the mineralizing matrix and later transported elsewhere by the blood vessels.

Dynamics of Galactolipids and Plastids in Nonphotosynthetic Cells of Glycine max Suspension Cultures : A Morphological and Biochemical Study

The age-dependent interrelationship of galactolipids and plastids in heterotrophic cell suspension cultures of Glycine max (soybean) was studied with regard to aging of nonphotosynthetic cells. Cells were propagated in the dark and under illumination with white light, and were harvested at days 7 (end of logarithmic phase), 14, and 21 (extended stationary phase). Electron microscopy revealed in dark-grown cells a proliferating decay of the amyloplast-type plastids, which could be correlated to a decrease of galactolipids. This trend was dramatically reversed in irradiated cultures, where the plastids of day 21 cells appeared rejuvenated. A concomitant increase of galactolipid content in the cells was observed, yet chlorophyll synthesis and photosynthetic activity were not induced. The dynamics of galactolipid contents did not correlate with total lipid contents in dark-grown as well as in irradiated cultures. [(3)H]Galactose served as a radioactive probe for the subcellular localization of galactolipids by electron microscopic autoradiography. Apart from plastids, galactolipids may also be constituents of the plasma membrane. The results render the heterotrophic cell suspension culture a suitable model to study the impact of senescence on plastids of nonphotosynthetic cells.

Electron-microscopic microprobe analysis on the initial stages of mineral formation in the epiphyseal growth plate

Dry thin sections (300-500 nm thick) of shock-frozen, freeze-dried and embedded epiphyseal growth plates from the proximal tibia of guinea pigs were cut longitudinally from the plate. Dark round bodies (phi less than 0.5 micron) were observed using the scanning transmission mode of the electron microscope initially directly in the vicinity of the chondrocytes. They gradually spread out in the direction of the metaphysis to the center of the longitudinal septum and represent most probably the matrix vesicles. By use of a microscan of 0.25 X 0.25 micron the element-concentrations of these bodies were measured. The measurements started on those bodies that could be clearly recognized and were extended to a length of 30-40 micron in the metaphyseal direction. To obtain approximate quantitative results the registered CaK alpha and PK alpha x-ray counts were directly compared with counts of fully mineralized regions, the Ca and P contents of which are known. Ca as well as p could be detected in the first visible vesicle-like structures (Ca approximately 0.2%, P approximately 0.4%) and increased steeply in the metaphyseal direction, amounting to approximately 6% Ca and 3% P. These results may lead to the conclusion that Pi becomes split from phosphate esters and transformed into the matrix vesicles already in a very early stage of enrichment. Incorporation of Ca may be coupled with this process.

Analysis of the crystal arrangement in collagen fibrils of mineralizing turkey tibia tendon

Mineralized pieces of tendons from the tibio-tarsus of turkeys were (i) shock-frozen, freeze-dried, embedded and cut without staining, or (ii) fixed, embedded and stained after sectioning. Micrographs were taken with an electron microscope on longitudinally cut sections. The center-to-center distances of neighboring apatitic needles within collagen fibrils were measured. For shock-frozen and freeze-dried specimens, the average of these distances is 4.7 nm and the most frequent value 4.2 nm; for the fixed and stained specimens, 3.8 nm and 3.6 nm, respectively. Laser diffraction of the electron micrographs showed a dumbbell-like intensity pattern (two diffuse maxima of intensity on the equator, one on each side of the central spot), giving an average distance of about 6 nm. This value represents the upper range of the direct measurements. The measurements demonstrate that the arrangement of the collagen microfibrils is mainly preserved during mineralization. However, using laser diffraction, distances of 9-11 nm were also observed. Such large distances can also be demonstrated by X-ray diffraction on collagen fibrils stained under special conditons. this may indicate that special conditions of apatitic mineralization or staining may alter the arrangement of the microfibrils.

Electron microscopical microprobe analysis of freeze dried and unstained mineralized epiphyseal cartilage

Electron micrographs have been taken of unfixed, freeze dried, unstained epiphyseal cartilage. In the mineralized long septa round to elliptic clusters (up to 0.6 micron in diameter) consisting mainly of dots and needles could be observed. The clusters were surrounded by microareas with a low contrast consisting mainly of ribbon plate-like crystallites. With the aid of scanning mode (STEM) of a transmission electron microscope, equipped with a Si(Li)-detector system, both regions were analyzed for calcium and phosphorus by electronprobe X-ray microanalysis. In ten series of 106 measurements in each region, it could be determined by registration of the CaKalpha and PKalpha X-ray counts that the mineral content in the clusters was in the range of 30-100% higher than in the light regions. The question of the sequence of the epiphyseal plate mineralization is discussed and whether the dense clusters represent the mineralized matrix vesicles.

Localisation and characterization of the fatty acid synthesizing system in cells of Glycine max (soubean) suspension cultures

In course of a study of fatty acid synthetase in higher plants, non-green cell suspension cultures of Glycine max (soybean) served as model tissues. For the first time, a fatty acid synthesizing system was characterized in cell cultures of higher plants and was found to be solely located in proplastids of the cells. Optimum activity of the fatty acid synthesizing system in proplastids was observed between pH 8.0 and 8.2; with [1-14C]acetate as substrate, cofactors required were CoA, ATP, Mn2+, Mg2+, HCO3-, NADH and NADPH. The system was more sensitive towards NADH than NADHP. [1-14C]Acetate,[2-14C]-malonate and [3-14C]pyruvate served as precursors for fatty acids, indicating the presence of pyruvate dehydrogenase activity in proplastids. In disrupted proplastids, [2-14C]malonylCoA was a better precursor than [1-14C]acetylCoA. After incubation of proplastids with [2-14C]malonate, a small shift, from palmitic acid to higher homologs, of label incorporated was observed, as compared to incorporation of label from [1-14C]acetate and [3-14C]pyruvate. Under the conditions of the experiment, only small amounts of polyunsaturated fatty acids, the main fatty acid components of this organelle, were synthesized. In respect to fatty acid synthesis, the non-green cell suspension culture resembles photosynthetic leaf tissue.

Electron microscopic microprobe analysis of mineralized collagen fibrils and extracollagenous regions in turkey leg tendon

Bundles of tibia tendon from 19 week-old turkeys were deep frozen, freeze dried and embedded in styrol methacrylate or Epon. In the distal mineralized region, bundles of unmineralized collagen fibrils as well as mineralized regions consisting of round microcompartments with low contrast surrounded by a mineral sheath with high contrast were found. The inner regions with low contrast corresponded to the mineralized collagen fibrils, while the contrast-rich peripheral zones corresponded to the mineralized collagen-free "ground substance". Using electron microscopic microprobe analysis, it was shown that the peripheral mineralized region, consisting mainly of closely packed needles, often contained 100% more mineral substance than the central, mineralized collagen zone, which consisted mainly of plate-like crystallites. Possible reasons for this difference in mineral content are discussed on the molecular level.