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Biomedical subjects

H Moor

Publications and source records attributed to H Moor.

At least 19 recordsLinked to original sources
PubMed1990

[Lung metastases].

Neither functionally not metabolically do pulmonary metastases represent an isolated problem of the respiratory organs. Rather, they are a problem of the organism as a whole, and represent the "home straight" that is common to almost all malignant diseases. This "home straight" has not yet been fully understood from the pathophysiological point of view, is not always readily accessible to diagnostic evaluation, and its response to treatment is disappointing. The key to successful therapy in the future will, presumably, be seen not so much in the eradication of existing metastases, as in the avoidance of their manifestation. Tangible results--that is, clinically useful results--are, as yet, not realiable.

Combined Modality Therapy↗
PubMed1987

Parathyroid ultrastructure after aldehyde fixation, high-pressure freezing, or microwave irradiation.

Parathyroid cell variants, commonly observed in parathyroid glands fixed by immersion in glutaraldehyde, are believed to be the result of cyclic changes in the course of parathyroid hormone secretion. Immersion of bovine parathyroid glands in a mixture consisting of 1% glutaraldehyde, 1.5% formaldehyde, and 2.5% acrolein, followed by post-fixation in 1% osmium tetroxide, resulted in high uniformity with only one cell variant, whereas the same fixation procedure led to disruption of cell membranes and formation of cell variants in rat parathyroids. Parathyroid glands of both cattle and rats prepared by high-pressure quick-freezing and subsequent freeze-substitution contained only one cell variant. Excellent preservation of the ultrastructure of bovine and rat parathyroids, also exhibiting only one cell variant, was achieved by microwave irradiation in the presence of 2.5% glutaraldehyde in Na-cacodylate followed by post-fixation with OsO4 in Na-cacodylate or s-collidine, both containing Ca2+ and Mg2+. Use of the appropriate buffer, as well as osmication, is essential for successful fixation utilizing microwave energy. The main effects are considered to be heating specimens within sufficient short periods and enhancement of subsequent osmium fixation. The results support the idea, arising after examination of perfusion-fixed parathyroid tissue, that parathyroid cell variants occur during improper aldehyde fixation rather than that they express functional diversity.

Air Pressure↗
PubMed1978

Complementary structures of membrane fracture faces obtained by ultrahigh vacuum freeze-fracturing at -196 degrees C and digital image processing.

Conventional freeze-etch replicas of the cytoplasmic fracture face (PF) of the yeast plasmalemma membrane show hexagonally ordered regions. Complementary features on the extraplasmic face (EF) could not be identified. Replicas with improved topographical resolution were obtained for both fracture faces by ultrahigh vacuum freeze-fracturing at -196 degrees C. The hexagonally ordered structure on the PF is seen to consist of volcano-like particles with a crater of 5 nm diameter. The lattice constant is 16.5 nm. On the EF, ring-like depressions corresponding to particles on the PF can occasionally be detected; the existence of ordered regions can be established by optical diffraction. Complementarity of periodic features on the PF and EF is demonstrated by digital image filtration. A main structure, coarse features of which appear on conventional PF replicas is shown to have perfect complementarity at a resolution level of 2 nm. On the EF an additional substructure, completely obscured on normal replicas, is revealed. Its complementarity remains tentative as shadows cast by the main structure impair identification of substructural features on the PF.

Cell Membrane↗
PubMed1978

Freeze-fracturing in ultrahigh vacuum at -196 degrees C.

Conventional freeze-etching is carried out in a vacuum of approximately 10(-6) torr and at a specimen temperature of -100 degrees C. The relatively poor topographic resolution of most freeze-etch replicas, and the lack of complementarity of morphological details in double replicas have been thought to be caused by structural distortions during fracturing, and radiation damage during replication. Both phenomena can be reduced by lowering the specimen temperature. To prevent condensation of residual gases (especially H2O) on the fracture faces at lower specimen temperature, an improved vacuum is required. Therefore, an ultrahigh vacuum freeze-fracture apparatus has been developed which allows fracturing and Pt/C-shadowing of specimens at -196 degrees C while maintaining a vacuum of 10(-9) torr. It consists of a modified Balzers BA 350 ultrahigh vacuum (UHV) unit, equipped with an airlock which enables the input of nonhoar-frosted specimens directly into the evacuated bell jar. A comparison of the paracrystalline plasmalemma structure in yeast cells portrayed by the conventional technique and by UHV-freeze-fracturing at -196 degrees C shows the improved topographic resolution which has been achieved with the new technique. The improvement is explained by less structural distortions during fracturing at lower temperatures. The particles of the paracrystalline regions on the P face are more regularly arranged and exhibit a craterlike substructure which corresponds with a ringlike depression in the E face. The optical diffraction patterns of these paracrystalline regions demonstrate the improvement of the structural record by showing well-defined third- and fourth-order spots.

Cell Membrane↗
PubMed1978

Decoration of specific sites on freeze-fractured membranes.

Fracturing under ultrahigh vacuum (UHV, P less than or equal to 10(-9) Torr) produces membrane fracture faces devoid of contamination. Such clean surfaces are a prerequisite for studies of interactions between condensing gases and distinct regions of a surface. For the study of water condensation, a device has been developed which enables production of pure water vapor and controlled variation of its partial pressure in an UHV freeze-fracture apparatus. Experiments with yeast plasmalemma fracture faces, produced at -196 degrees C and exposed to pure water vapor before replication, resulted in a "specific decoration" with ice crystals of those pits in the extraplasmic face where the corresponding particles of the plasmic face had been removed. Because water condenses as discrete ice crystals which resemble intramembrane particles, ice crystals might easily be misinterpreted as actual membrane structures. At low specimen temperature (T less than or equal to 110 degrees C) the structural features of membrane fracture faces produced under high vacuum (P approximately 10(-6) Torr) should, therefore, be interpreted with caution.

Cell Membrane↗
PubMed1977

The Ranvier nodes in the neurogenic electric organ of the knifefish Sternarchus: a freeze-etching study on the distribution of membrane-associated particles.

The two types of Ranvier nodes (type I with narrow gap, type II with giant gap) and internodes in nerve fibers composing the Sternarchus electric organ have been studied by means of freeze-etching electron microscopy. Numerical analysis of the distribution of membrane-associated particles revealed the following features: (1) the P-faces of both types of nodes and of the internodal axon bear a similarly high density of particles (1000-1200 particles/sq. micron on the average). (2) particle density is differential in E-faces: the histogram for type I nodes has a wider range of particle concentrations (114-1522 particles/sq. micron) than that for type II nodes (45-576 particles/sq. micron) whose density values are in the same range as those of the internodal axon. At least some type I nodes (narrow gaps) generate spikes and probably have a low resistivity; these nodes may be those with high particle density on E-faces. The low particle density on E-faces of type II nodes may be associated with high resistivity and absence of excitability. Similarly, the low particle density in internodes may reflect inexcitability. There is evidence that the transition from one nodal type to the next is gradual: as the gap width of type I nodes increases, there is an occurrence of surface elaborations and the density of E-face particles tends to drop towards the range of type II nodes.

Animals↗
PubMed1976

The fine structure of the perineural endothelium.

Fine strands of motor nerves were examined with the electron microscope using thin section as well as freeze-etching techniques. The specimens were taken from frog cutaneous pectoris nerve, rat sciatic nerve, mouse and shrew phrenic nerves and from human skin nerves. The perineural sheath (Henle, Ranvier, Key and Retzius) consists of one to several concentric laminae of endothelial cells; it encases nerve fascicles and eventually individual nerve fibers and terminals. The endothelial cells are extremely thin and fitted togeether smoothly by overlap and dove-tailing of their border zones. The cell contacts are formed by continuous zonulae occludentes, often reinforced by maculae adhaerentes, and in depth they comprise 3-15 strands with an average of 5-6 strands per junction. The membranes of endothelial cells are studded with attachment sites and stomata of plasmalemmal vesicles suggesting a high level of pinocytotic activity. This phenomenon is by no means restricted to the external laminae of the endothelial sheath. Each endothelial lamina is vested with basement membranes on both (epineural and endoneural) sides, and the spaces between laminae contain a few collagen fibers and fibroblasts. Occasionally, punctate tight junctions are seen between laminae. Cytological evidence supports the hypothesis that the perineural endothelium provides a relatively tight and highly selective barrier separating the peripheral nerves from surrounding tissue and its extracellular fluid spaces. This effect is achieved on the one hand by the sealing of pericellular spaces and on the other hand by a membrane controlled transcellular transport mechanism (pinocytosis), both of which are enhanced by their serial arrangement.

Animals↗
PubMed1975

Ultrastructural evidence for sinusoid spaces and coupling between pituicytes in the rat.

The pericapillary palisade of the rat neurohypophysis was examined by means of thin-section and freeze-etch electron-microscopy. Special attention was given to pituicyte processes intermingled with neurosecretory terminals. These processes are identified by the presence of lipid droplets and ribosomes. Extracellular spaces are conspicuously enlarged in circumscribed regions between fingerlike protrusions of pituicyte processes. Neurosecretory axons seem to have free access to these enlarged spaces. Zonulae occludentes often combined with small gap junctions are found at the border of these sinusoid spaces. Gap junctions and occasionally intermediate junctions are seen between pituicyte processes. The topographic relationship and the functional significance of these structural features remain to be further elucidated.

Animals↗
PubMed1975

[Behavior of serum IgE in patients with atopic extrinisic asthma. Studies with a modified radioimmunologic sorbent technic, Phadebas-IgEtest].

Serum IgE levels were measured by radioimmunosorbent techniqueera from patients with atopic extrinsic asthma, from patients with chronic bronchitis and from healthy adults. 51 of 65 patients with atopic extrinsic asthma had IgE values above the mean normal. Patients who were hypersensitive to different allergens commonly showed higher IgE concentrations than those who were hypersensitive to a single allergen only. Compared with IgE values found in patients with chronic bronchitis the differences were statistically highly significant. However the measurement of serum IgE may be a valuable diagnostic tool but only in supplement to other clinical investigations.

Adsorption↗