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Biomedical subjects

T A Hall

Publications and source records attributed to T A Hall.

At least 19 recordsLinked to original sources
PubMed1991

Suggestions for the quantitative X-ray microanalysis of thin sections of frozen-dried and embedded biological tissues.

When a microregion in a thin section of frozen-dried and embedded tissue is analysed by the conventional electron-probe X-ray continuum-normalization method, the measured quantity is in mmol of element per kg of embedded specimen. As each microregion contains an unknown amount of embedding medium, this quantity generally lies indeterminately somewhere within the wide range between mmol of element per kg of hydrated tissue and mmol of element per kg of dehydrated tissue. However, if a 'tag' element is incorporated in the embedding medium, the contribution of the medium to the local continuum count in each probed field should be measureable, and the X-ray data may then unambiguously yield mmol of element per kg of dehydrated tissue. This result should not be affected by shrinkage on freeze-drying or by incomplete replacement of water by embedding medium. The same X-ray data can additionally provide estimates of mmol of element per unit volume, mmol of element per kg of hydrated tissue and local dry-mass fraction. However, these estimates are subject to errors due to tissue shrinkage, incomplete replacement of water and beam damage.

Animals↗
PubMed1979

Biological X-ray microanalysis.

By means of X-ray microanalysis it is now practical to detect approximately 10(-19) g of an element in a static-probe analysis within an ultrathin section, with analytical spatial resolution in the range 20--30 nm. The main difficulties for biological microanalysis are connected not with sensitivity but with specimen preparation and beam damage. Careful cryopreparation, beginning with the quench-freezing of a small block of tissue, is essential even for determining the storage sites, or sites of binding in vivo, of physiologically active elements. In frozen-dried or frozen-hydrated sections of quench-frozen tissue, it is now possible to measure local mass fractions of diffusible as well as of bound elements.

Biology↗
PubMed1979

The quantitative measurement of electrolyte elements in nuclei of maturing erythrocytes of chick embryo using electron-probe X-ray microanalysis.

Na, K and Cl measurements have been made on frozen sections of chick red blood cells throughout embryonic development, using electron-probe microanalysis. There is an apparent fluctuation in the levels of these elements during maturation, although the Na/K ratio remains fairly constant. The nuclear Na concentration resembles that of the cytoplasm, rather than that of the medium, at all stages. Inhibitor studies indicate that when cytoplasmic Na, K and Cl levels are altered, their corresponding nuclear levels are similarly affected. Additionally, the measurements in nuclei isolated in anhydrous media from lyophilized cells have shown artefactual accumulation of high Na, K, Ca and Mg.

Animals↗
PubMed1979

Quantitative electron probe X-ray microanalysis of electrolyte elements within epithelial tissue compartments.

The electron probe X-ray microanalysis of 1-micron thick frozen-hydrated sections provides a method to measure local concentrations of electrolyte elements (and H2O) in and around the cells in situ with an analytical spatial resolution of better than 0.2 micron and a sensitivity limit better than 10 mM with a standard error of less than 10%. Our microprobe studies on several epithelia transporting isotonic fluids have provided strong evidence that the electrolyte concentration in the interspaces suspected to be the sites of solute-solvent coupling may, on average, be as much as 35% more than in the bathing fluid. There also appear to be distinct concentration gradients in interspaces, the profiles of which differ according to the tissue geometry but particularly according to the location of the leaky cell junctions, suggesting that the osmotic equilibration of the transported fluid may require substantial mass flow through the junctions. In addition, there is evidence a) that the major electrolytes in the cytoplasm of the epithelial cells are not uniformly distributed but may have distinct axial and radial concentration gradients that depend on active solute transport (e.g., that abolished by ouabain); b) that in some epithelia (e.g., rabbit ileum) there is a peripheral cytoplasmic zone that may support fast convective flow for transcellular fluxes; c) that the extracellular structures like the glycocalyx and basement membrane preferentially sequester potassium (and calcium) and could have a non-zero reflection coefficient; and d) that in normal cells, nuclei have ionic composition similar to that of the circumnuclear cytoplasm.

Animals↗
PubMed1978

Calcium and sulphur in neurosecretory granules and calcium in mitochondria as determined by electron microscope x-ray microanalysis.

Sections of neurosecretory cells fixed in glutaraldehyde and osmium tetroxide were studied by means of an EMMA-4 analytical microscope. Secretory granules in neurosecretory cells of the corpus cardiacum and of the brain, both in the desert locust Schistocerca and in the blowfly Calliphora, as well as neurosecretory granules in posterior pituitaries of the frog Rana and of the albino rat all contain a high concentration of calcium. A distinct sulphur peak was also a constant feature. In neurosecretory cells of the corpus cardiacum of Schistocerca the chromatin contained a high concentration of calcium. The mitochondria also contained much calcium, but part of this disappeared during preparation except when fixative and wash contained calcium chloride. By block staining with uranyl acetate most calcium is displaced from the mitochondria, whereas most of the calcium remains in the neurosecretory granules. Since the calcium peaks in spectra from neurosecretory granules appear of similar size, regardless of variations in the preparative procedure, this calcium must be firmly bound. The possible role of the calcium bound to the neurosecretory substance is discussed. The presence of sulphur in insect neurosecretory granules indicated the presence of a protein besides the hormone, i.e., an insect neurophysin.

Animals↗
PubMed1977

Zinc distribution in injured myocardium. EMMA-4 examinations of dogs' hearts after coronary ligation.

Electron microscopic X-ray microanalysis and atomic absorption spectrophotometry were used to determine changes in zinc concentration after myocardial ischemic injury by coronary ligature in dogs. The zinc concentration increased in the damaged myocardium especially in specific intracellular locations identified by means of the microprobe. It was concluded that the selective zinc augmentation was related to proliferative and biosynthetic reactive processes in the myocardium.

Animals↗
PubMed1977

Origin, structure, composition and age-dependence of mineralized dense bodies (concretions) in the midgut epithelium of the adult housefly, Musca domestica.

The epithelial cells of the midgut in 1-40 day old adult female houseflies were examined by electron microscopic X-ray microalnalytic and histochemical techniques in order to study the mode of genesis, chemical nature and age-associated distribution of dense bodies. Dense bodies contain high concentration of phosphorus sulphur, chlorine, calcium, iron and copper; they are therfore termed concretions. Concretionary material is initially deposited within Golgi vesicles, lamellar bodies and residual bodies. The average size of the concretion granules and the concentration of the sequestered material increases with age, while new concretions are continually formed throughout life. With advancing age, concretions accumulate in the epithelial cells and occupy a considerable proportion of the cytoplasm in old flies. It is postulated that the concretions sequester superfluous minerals and may play an important role in the excretory system of the adult housefly.

Acid Phosphatase↗
PubMed1976

Fine structure and x-ray microanalysis of mineralized concretions in the malpighian tubules of the housefly, Musca domestica.

The epithelium and the lumen of the Malpighian tubules of the housefly contains mineralized dense bodies called concretions. The morphological characteristics, mode of origin, nature of the sequestered elements and the age-associated changes in the distribution of concretions are reported. There are three types of concretions in the cytoplasm, which have been designated as type A, type B, and type C. Type A concretions are membrane-bound spherical structures which may arise by the gradual intravacuolar accumulation of dense material. Type B concretions appear to be related to multivesicular bodies. Type C concretions are heteromorphic and morphologically resemble the residual bodies. They show a positive localization of acid phosphatase reaction product. X-ray microanalysis of intracytoplasmic and intraluminal concretions revealed the presence of phosphorus, sulphur, chlorine, calcium, iron, zinc and copper. There was no evidence suggesting the extrusion of the intracytoplasmic concretions into the lumen of the Malpighian tubules. There is an age-associated increase in the distribution of type C concretions. It is hypothesized that the sequestration of metal ions within the concretions may provide a means for the effective excretion of these elements.

Aging↗
PubMed1976

Electron microscopic x-ray microanalysis of normal and leukemic human lymphocytes.

A comparative study of the elemental content of normal and leukemic cells was undertaken on a few subjects, using electron microscopic x-ray microanalysis. Phosphorus, sulfur, chlorine, calcium, copper, and zinc were detected in intracellular loci. The concentration of some of the above elements appeared to be disease related. In leukemic lymphocytes, the nuclear zinc was significantly lower than that recorded in normal lymphocytes, while the phosphorus was only moderately decreased. This suggests a faulty zinc uptake or binding in leukemic cells. The possible consequences of intracellular zinc deficiency are discussed.

Calcium↗
PubMed1976

Gold tracer studies of muscle regeneration.

Rabbits were injected with soluble gold, and cold injury was inflicted upon their extraocular muscles. Following the typical freeze-thaw damage in which the myofiber basement membrane is preserved, a polymorphonuclear granulocyte exudation occurred. At this stage only a few interstitial cells with long processes contained gold. At one and two days abundant mononuclear cells with gold were observed at the site of injury. In subsequent stages of muscle regeneration the amount of tracer decreased but myoblasts, and even fully formed myotubes, often contained detectable gold. Some data on "in vivo" gold salt kinetics and the specificity of gold localization were utilised in the study of the relation between mononuclear interstitial cells and myoblasts.

Animals↗
PubMed1976

Aurothiomalate as an ultrastructural marker. Electron microscopy and x-ray microanalysis of various tissues after in vivo gold injections.

Rabbits and rats were given single injections of aurothiomalate by different routes. The animals were killed at progressive intervals, and sections from various organs were examined by electron microscopic x-ray microanalysis. Ultrastructurally, characteristic material was regularly found in vacuoles, dense and heterogeneous bodies of macrophages, hepatocytes and renal epithelial cells. Occasionally, other mesenchymal cells also contained gold. Histochemical and analytical tests showed that the gold-containing organelles were devoid of acid phosphatase activity. The generalized rapid spread, retention and selectivity of localization after a single small dose make aurothiomalate a useful marker substance for ultrastructural studies.

Acid Phosphatase↗