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Biomedical subjects

H Gross

Publications and source records attributed to H Gross.

At least 91 records · Page 5Linked to original sources
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

Evaluation of purified H and M antigens of histoplasmin as reagents in the complement fixation test.

Complement-fixation (CF) tests were performed with purified H and M antigens, histoplasmin, and Histoplasma capsulatum whole cell yeast phase antigen using sera of 126 patients with proven or suspected histoplasmosis. Specific titers for either H or for M antibody were obtained with the individual purified antigens; the highest titers were comparable to those obtained with histoplasmin. However, in sera containing only anti-M antibody, the titers obtained with the purified M antigen were 2 to 16 times those obtained with the histoplasmin or yeast phase antigens. The CF test for either H or M antibody was 4 to 32 times as reactive as the agar-gel microimmunodiffusion test; in general precipitin lines were obtained with either H or M antigens from sera with CF titers greater than or equal to 8. With sera containing H antibody, there was an excellent correlation between the CF titers obtained with purified M antigen and histoplasmin. The correlations of CF titers with H antigen and either histoplasmin or yeast phase antigen were very low.

Antibodies, Fungal↗
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↗
PubMed1978

Cholesterol in preteen children of parents with premature coronary disease.

A pediatric population at high risk for the development of coronary artery disease has been identified. Using a simple and inexpensive protocol, serum cholesterol determinations were performed on 50 children 12 years old and younger. These children were taken from 28 families in which one parent had suffered a myocardial infarction before the age of 50. Eight of the 50 children were found to have significant elevation of serum cholesterol. This was an incidence of 16%--twice that of the general pediatric population. Subjects with both adverse genetic and metabolic backgrounds need to be identified in this simple way. Preventive and therapeutic measures in such children may alter in the future the serious morbidity and mortality of coronary artery disease.

Age Factors↗
PubMed1977

[Adult metachromatic leukodystrophy manifested as schizophrenic psychosis (author's transl)].

An autopsy case of adult metachromatic leukodystrophy (MLD) manifested clinically as schizophrenic psychosis is reported. A 50-year-old man developed progressive mental changes 10 years before his death, and later manifested a schizophrenic syndrome without neurologic deficits or EEG changes. After his death from uremia neuropathology disclosed MLD with demyelination accentuated in the frontal lobes and abundant metachromatic deposits in the preserved areas of cerebral white matter. Neurochemical examination of the demyelinated frontal area showed reduced concentration of cerebrosides and sulfatides, decreased amounts of total lipids in the tissue, and an increase of sulfatides, and particularly of their cerebron fractions in lipid extract. The problems of adult forms of MLD with prolonged course are discussed with special reference to cases showing mainly psychiatric syndromes.

Atrophy↗
PubMed1977

Immunogenicity and characteristics of M protein released by phage-associated lysin from group-A streptococci types 1 and 23.

A phage-associated lysin (PAL) was used to release M protein from goup-A streptococci of types 1 and 23. Much of the lysin-released-M protein (LYSIN-M) of both types was of high molecular weight, since LYSIN-M appeared just after the void volume on Sephadex G-200 gel-filtration. Some of the LYSIN-M appeared just after the void volume on Sephadex G-200 gel-filtration. Some of the LYSIN-M of both types was found to be firmly attached to group-A carbohydrate. Type-1 LYSIN-M was partially purified by ammonium-sulfate precipitation followed by absorption and elution from an immunoabsorbent column containing antibody for group-A carbohydrate. Type-23 LYSIN-M was partially purified by precipitation at its isoelectric point, pH 4-9. Rabbits immunised in the footpads with either type-1 or type-23 LYSIN-M responded by producing both precipitins and bactericidal (opsonising) antobodies. Some of the antiesera were absorbed and rendered specific for homologous acid extracts. The LYSIN-M preparations of both types 1 and 23 were originally contaminated with heat-labile antigen(s). Antibodies to these heat-labile antigen(s), which cross-react from type to type, were found in the type-specific antisera distributed by the Center for Disease Control. The specificity of Lancefield typing antisera depends on their being tested with extracts of streptococci prepared at pH 2 and 100 degree C for 10 min. Although LYSIN-M is more difficult to prepare and purify then acid-heat released M protein, it might prove useful for studying the nature of native streptococcal M protein.

Antigens, Bacterial↗
PubMed1976

H and M antigens of Histoplasma capsulatum: preparation of antisera and location of these antigens in yeast-phase cells.

Antiserum has been prepared in rabbits against the H and M antigens of H. capsulatum with immunoelectrophoretic precipitin arcs used as vaccines. The antiserum is specific for H. capsulatum in the immunodiffusion test and can be used as reference serum for identifying antibodies to these antigens in sera from suspected cases histoplasmosis. We found that (1) hand m antigens are not located on the surface of yeast-phase cells and (ii) complement fixation releases the antigens reactive in the complement fixation test from yeast-phase cells.

Antibodies, Fungal↗
PubMed1975

Simple procedure for production by group C streptococci of phage-associated lysin active against group A streptococci.

Phage-associated lysin of high potency was prepared by growing the host group C streptococcal strain 26RP66 in a semisynthetic medium. The lysin was stabilized by adding dithiothreitol and neutralized ethylenediaminetetraacetic acid (EDTA) to facilitate further concentration and partial purification. The lysin remained active when stored at -65 C for 1 year. Lysin was active against all strains of group A streptococci tested and was more active against living cells than heat-killed cells. The procedure outlined is practicable for most bacteriological research laboratories and does not require column purification or other complex biochemical procedures. It should be useful to any laboratory which requires small amounts of lysin to produce L-forms and protoplasts or to release streptococcal antigens.

Ammonium Sulfate↗
PubMed1975

Evaluation of histoplasmin for the presence of H and M antigens: some difficulties encountered in the production and evaluation of a product suitable for the immunodiffusion test.

The development of a single histoplasmin suitable for use in immunodiffusion testing of a variety of human histoplasmosis sera depends not only upon the presence of both antigens, but on relative concentration of one to the other, and perhaps on the chemical characteristics of the H and M antigens of a given strain.

Antigens, Fungal↗