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Biomedical subjects

H Mach

Publications and source records attributed to H Mach.

At least 55 records · Page 3Linked to original sources
PubMed1991

[Nitrate and nitrite levels in daily food rations of children from the rural Puławy regions].

In the region of Puławy where the operation of the Nitrogen-Compound Manufacturing Plant has lead to an increase in nitrogen compound emission to the environment, nitrate and nitrite contents in daily food rations of children were determined. Daily food rations of children aged 8-9 and 12-13 years were collected from individual farms in four villages situated in the vicinity of the Nitrogen Plant, as well as--for control--from individual farms in Janowiec, a village distant from this Plant. Nitrate and nitrite contents were assayed in 300 daily food rations taken in spring and autumn. Nitrate was reduced to nitrite on a cadmium column whereupon it was determined colorimetrically using sulphanilic acid and N-1-napthyl-ethylenediamine. It was found that in the group of younger children as many as 70%, on the average, of the examined food rations displayed nitrate contents exceeding the admissible levels. In the group of the 12-13 years old children, the percentage of daily food rations whose nitrate content exceeded the admissible level was lower, averaging ca. 30% of all rations examined. The percentage of the daily food rations in which the nitrite content was higher than admissible level was closely similar in both groups of children, averaging ca. 30% of all rations examined. Food rations collected in spring, as compared with those taken in autumn, contained significantly greater amount of nitrate. In both periods of studies, nitrate contents were greater in the food rations from the farms situated near the Nitrogen Plant than in the food rations from farms in Janowiec.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1990

Inhibition of alpha-crystallin aggregation by gamma-crystallin.

The transparency of the mammalian lens is primarily maintained by short range order among the major proteins of the lens fiber cells, the crystallins. Although these proteins are highly conserved at the amino acid sequence level, it has proven difficult to establish that they possess other than structural functions. We find that when non-lens proteins are added to concentrated solutions of alpha-crystallin, aggregation is induced, presumably through excluded volume effects. In contrast, the monomeric gamma-crystallins and the low molecular weight form of beta-crystallin (beta L) cause a decrease in the size of alpha-crystallin. When the naturally aggregated form of alpha-crystallin is examined, gamma- and beta L-crystallin, as well as a reducing agent, also cause partial dissociation as detected by dynamic light scattering and size exclusion chromatography, while no effect is seen with non-crystallin proteins. Furthermore, the chemical cross-linking of alpha-crystallin is inhibited by gamma- and beta L-crystallin but not by other proteins. The ability of gamma-crystallin to inhibit the association of alpha-crystallin is primarily localized to the gamma-II form which contains a high degree of exposed thiols. Only small amounts of gamma- and beta L-crystallin, however, can be cross-linked to alpha-crystallin in mixtures of the three proteins even at very high protein concentrations. These results suggest that one possible role for the lower molecular weight crystallins may be to minimize through a reductive effect the intrinsic tendency of alpha-crystallin to aggregate, an association reaction implicated in the loss of lens transparency.

Animals↗
PubMed1989

Quantitative analysis of protein mixtures by second derivative absorption spectroscopy.

A new method for the quantitative analysis of protein mixtures based on multicomponent analysis of the second derivative near uv spectra is described. Using bovine eye lens crystallins, we demonstrate that the technique can provide precise concentrations of closely related proteins within mixtures, under both native and denaturing conditions. We have also successfully used the method to analyze the subunit composition of a heteromultimeric protein aggregate. The method is more rapid and precise than alternative approaches and offers the advantage of substantially reduced interference from many extraneous solution components and light scattering. It is also nondestructive and extremely sensitive, requiring only small volumes of sample at low total protein concentrations. Prospective applications are proposed for the study of eye lens crystallins, as well as for other protein/protein and protein/nonprotein mixtures.

Animals↗
PubMed1989

[Use of nitrates in hypertension. Cardiac and peripheral effects before and during antihypertensive therapy at rest and during stress].

The acute effects of 1.6 mg glycerol trinitrate (2 x 0.8 mg) on the hemodynamic function were compared in 11 healthy subjects and 25 hypertensive patients (WHO stages I and II), at rest and during exercise. The nitrate testing was performed before the beginning of antihypertensive treatment, during nonmedical therapy, as well as under additional oral therapy with diisopropylamin. Right-heart-catheterization, echocardiography, radionuclide-ventriculography and venous occlusion plethysmography were performed. Nitroglycerin consistently led to a reduction of blood pressure in the systemic and pulmonary circulation both at rest and during exercise. There was a small decrease of peripheral arterial resistance (TPR) at rest and a more pronounced decrease of pulmonary arteriolar resistance (PAR) at rest and during exercise. The documented effects may be important with regard to combined antihypertensive treatment. In addition, the application of nitrates in hypertensive crises may be useful.

Administration, Sublingual↗
PubMed1988

[Regulation of the fetoplacental unit. 3. Suppression of the fetoplacental unit by cortisol in relation to the maturity of the fetus].

The present study investigates the suppression of free plasma oestriol by cortisol in mature and immature foetuses. 6 patients in the 32nd week of gestation and 6 patients in the 38th week received an infusion of 100 mg cortisol (Hydrocortison Hoechst) from 10 a.m. to 12 a.m. Blood specimens (5 ml) were drawn from 8 a.m. to 5 p.m. in 60 or 30 minutes intervals, respectively. Free plasma oestriol was measured by radioimmunoassay, total plasma cortisol by the protein binding method. In the 32nd week of gestation plasma oestriol rose from 501 +/- 240 ng/ml to 1035 +/- 301 ng/ml, whereas oestriol decreased from 5.2 +/- 1.0 ng/ml to 3.9 +/- 1.5 ng/ml (p less than 0.001). After an analogous rise of cortisol, oestriol levels in the 38th week were suppressed from 12.5 +/- 3.3 ng/ml to 4.0 +/- 1.6 ng/ml (p less than 0.001). The degree of oestriol suppression of 68 percent in the 38th week markedly exceeded that of the 32nd week (25%). According to these results, the hypothalamic-hypophyseal system of mature foetuses exhibits a higher sensitivity to the feed back action of cortisol than immature foetuses.

Estriol↗