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Biomedical subjects

J Hegenauer

Publications and source records attributed to J Hegenauer.

At least 19 recordsLinked to original sources
PubMed1992

Metal-ion-directed site-specificity of hydroxyl radical detection.

A wide variety of .OH detectors are in use for determination of biological .OH production. The chemical generation of .OH is site-specific with respect to the metal-binding site, and thus .OH detectors with metal-binding properties may affect the biological damage and bias .OH detection. The present study shows that both salicylate and phenylalanine, added as low molecular weight .OH indicators, decreased Cu(II) binding to erythrocyte ghosts. In a cell-free system, Cu(II) complexed to both salicylate and phenylalanine. Phenylalanine is a stronger Cu(II) chelator than salicylate, both when competing for Cu(II) bound to ghosts and when competing directly with each other. When OH radicals were generated by ascorbate and Cu(II), the amount of .OH detected as dihydroxybenzoates was proportional to the amount of .OH produced. However, when phenylalanine was added to this system, the efficiency of .OH detection by salicylate strongly decreased, concomitant with the transfer of Cu(II) binding from salicylate to the amino acid. This decrease was larger than that predicted by calculations for random competition of the two detectors for .OH. Deoxyribose and mannitol, which do not bind copper appreciably, competed poorly with salicylate for the .OH. Hydroxylation of phenylalanine, on the other hand, was only slightly affected by the presence of salicylate and unaffected by deoxyribose and mannitol. These results suggest that the detection of .OH by low molecular weight .OH indicators was related to the relative affinity of the detectors for the catalyzing metal, and thus partially site-specific. Furthermore, glutamate, which does not contain an aromatic ring but binds Cu(II) with considerable affinity, competed strongly with salicylate for the .OH, indicating that metal-binding properties rather than the presence of an aromatic ring were the cause of the deviation from random competition. The results indicate that .OH indicators with metal-binding properties affect the distribution of catalytic metal ions in a biological system, causing a shift of free radical damage and localizing a site-specific reaction of .OH on these detectors, with a resulting positive bias in the apparent .OH production.

Ascorbic Acid↗
PubMed1987

Isolation and characterization of a new zinc-binding protein from albacore tuna plasma.

The protein responsible for sequestering high levels of zinc in the plasma of the albacore tuna (Thunnus alalunga) has been isolated by sequential chromatography. The glycoprotein has a molecular weight of 66,000. Approximately 8.2% of its amino acid residues are histidines. Equilibrium dialysis experiments show it to bind 3 mol of zinc/mol of protein. The stoichiometric constant for the association of zinc with a binding site containing three histidines was determined to be 10(9.4). This protein is different from albumin and represents a previously uncharacterized zinc transport protein.

Amino Acids↗
PubMed1986

Age-related differences in the bone mineralization pattern of rats following exercise.

The effect of 12 weeks of treadmill exercise on the mineralization of trabecular and cortical bone was studied in rats 7, 14, and 19 months of age. Bone mineralization was evaluated by measuring concentrations of Ca, Mg, and hydroxyproline as well as uptake of 45Ca concentration in the femur, humerus, rib and calvaria. The 7- and 14-month-old rats increased mineralization in those cortical bones directly involved in exercise. The 19-month animal responded to exercise by increasing mineralization in all bones examined, including the nonweight bearing trabecular calvaria and cortical rib. From these data, it is apparent that the older animals undergo a total skeletal mineralization in response to exercise compared with local adaptation in the younger animal. Further, we provide evidence to support the use of the rat as a model in which to study mammalian bone physiology during the aging process.

Aging↗
PubMed1986

Effects of long-term dietary manganese and copper deficiency on rat skeleton.

Experiments were designed to produce biochemical changes in both serum and bone in rats by long-term dietary deficiencies of manganese (Mn) and copper (Cu). Weanling rats were fed one of three diets: 1) normal Mn and Cu (N), 2) low Mn and Cu (L) and 3) depleted Mn and normal Cu (D). After 12 mo, serum Ca and P were significantly greater in the D rats than the N rats (134, 50 mg/L and 103, 39 mg/L, respectively). Serum and femur Mn levels were lower in D rats than in normal rats. Serum and femur Cu levels were lower in L rats than N rats. Femur Ca concentrations were significantly lower in D rats than in N rats (180 and 272 mg/g, respectively). Radiographic differences could be detected in some rats fed the L and D diets. In the two deficient groups, increased serum Ca was negatively correlated with bone Ca (r = -0.69; P less than 0.01). This biochemical association may represent alterations in regulatory control of Ca at the level of the bone (decreased mineralization) combined with an increase in bone resorption. The effect of long-term dietary deficiencies in Mn and Cu should be considered in human bone metabolism.

Animal Nutritional Physiological Phenomena↗
PubMed1982

Mitochondrial NADH dehydrogenase in iron-deficient and iron-repleted rat muscle: an EPR and work performance study.

Iron may affect both respiratory O2 transport and mitochondrial electron transport in the performance of muscle work. This study was designed to elucidate the molecular defect of iron-deficient work performance by identifying heretofore unmeasurable mitochondrial enzymes that are diminished by iron deficiency and may be restored by iron repletion. Female rats were made iron-deficient by dietary control and were repleted by oral iron. Iron deficiency reduced physical work capacity (treadmill running time), haemoglobin (Hb), and mitochondrial iron-sulphur (Fe-S) centres in heart and skeletal muscles; mitochondrial number was unaffected. Oral iron supplementation restored work capacity and Hb within 4 d to normal or near-normal levels, but in general Fe-S centres of mitochondria due to NADH dehydrogenase remained at iron-deficient levels. Subnormal concentrations of mitochondrial iron-dependent NADH dehydrogenase in muscle are not by themselves rate-limiting in work performance.

Anemia, Hypochromic↗
PubMed1979

Iron(III)--phosphoprotein chelates: stoichiometric equilibrium constant for interation of iron(III) and phosphorylserine residues of phosvitin and casein.

Estimates of the strength of iron binding to model phosphoproteins were obtained from equilibrium dialysis experiments. Iron-free phosvitin (chicken and frog) or alpha sl-casein (cow) was dialyzed against the iron(III) chelates of nitrilotriacetate (NTA), )ethylenedinitrilo)tetraacetate (EDTA), or citrate. Protein-bound metal was measured at equilibrium; competition of chelator and phosphoprotein for iron(III) was determined by reference to comprehensive equilibrium equations presented in the Appendix. Analysis of the iron-binding data for phosvitin suggested that clusters of di-O-phosphorylserine residues (SerP.SerP) were the most probable iron-binding sites. A stoichiometric equilibrium constant of 10(18.0) was calculated for the formation of the Fe3+(SerP.SerP) chelate. When comared on the basis of phosphate content, casein bound iron more weakly than phosvitin. However, if the stoichiometric equilibrium constant for the formation of the casein Fe3+(SerP.SerP) chelate (10(17.5) was adjusted to account for the fact that a smaller percentage of casein phosphoserines occurs in di-O-phosphorylserine clusters, the affinity of casein and phosvitin for iron was very similar. A theoretical comparison showed that the "strengths" of the ferric chelates can be ranked: EDTA greater than phosphoprotein di-O-phosphorylserine greater than citrate greater than NTA.

Animals↗
PubMed1979

Removal of cadmium(II) from crystallized ferritin.

The cadmium content of crystallized horse spleen ferritin, usually about 2% by weight without special treatment, can be substantially decreased by prolonged dialysis against certain chelating agents, chaotropic ions, or weakly reducing anions. For example, neutral bisulphite buffer (2M) removed 95% of the bound cadmium of crystallization without affecting the iron content, and may thus be valuable for preparing "metal-free" holoferritin for physical-chemical studies.

Cadmium↗
PubMed1979

Degradation of ascorbic acid (vitamin C) in iron-supplemented cows' milk.

The fate of [6-carbon-14] ascorbic acid in iron-supplemented and unsupplemented raw milk was studied by anion-exchange chromatography, which permitted quantitative analysis of the conversion of ascorbate to dehydroascorbate and diketogulonate as a function of time. Iron catalyzed an increase in the rate of autoxidation of ascorbate to dehydroascorbate but did not alter the equilibrium concentrations of ascorbate, dehydroascorbate, and diketogulonate. The conversion of ascorbate to dehydroascorbate and of dehydroascorbate to diketogulonate occurred rapidly even in unsupplemented milk. Thus, trace metal supplementation may not affect materially the vitamin C content of stored milk.

2,3-Diketogulonic Acid↗
PubMed1977

Correlation of serum ferritin and liver ferritin iron in the anemic, normal, iron-loaded rat.

We developed a two-site immunoradiometric assay for rat serum ferritin that uses antibody immobilized on agarose. Individual serum ferritin values were significantly correlated with iron stores as determined chemically by liver ferritin iron content. This group correlation was not sufficiently great, however, to allow confident prediction of iron stores in a given animal on the basis of serum ferritin alone. Significant differences in mean liver ferritin iron concentration between groups of rats raised on diets of differing iron content were not always reflected by differences in mean serum ferritin values. Data correlating the serum levels of ferritin and a liver-specific transaminase suggested that hepatocellular death may sometimes contribute ferritin to the serum. Strong postitive correlations between serum ferritin and iron stores in the rat were not observed when serum transaminase levels were in the normal range.

Alanine Transaminase↗
PubMed1977

A hydrostatic device for tissue dehydration.

A simple device for mixing water and organic solvents can be easily constructed to dehydrate tissue for electron microscopy. The device utilizes hydrostatic leveling between a reservoir and a mixing chamber to produce a continuously increasing concentration of dehydrating solvent. The rate of dehydration may be regulated by geometry and/or outflow rate. A prototype model is described which compactly incorporates the solvent reservoirs and a tissue tray that can accommodate ten tissue specimens in stainless steel mesh baskets. The device can be fabricated cheaply and replaces manual dehydration.

Desiccation↗
PubMed1975

Effect of milk and casein on the absorption of supplemental iron in the mouse and chick.

Milk is an attractive vehicle for introducing iron supplements into iron-deficient infants and children. This study compares the effects of milk and caseins on the whole-body absorption of radioactive iron complexes in an attempt to resolve the controversy over whether milk and its constituent phosphoproteins seriously impair iron absorption. Evidence is presented to clarify the role of the calcium-casein micelles of cow's milk in binding iron donated by the ferric-nitrilotriacetate (NTA) complex. The absorption of iron from isolated Fe(III)-casein complexes was studied in mice as a function of the casein--to--Fe ratio and was compared with the absorption of Fe(III)-NTA at equivalent levels. Even at casein--to--Fe ratios higher than those found in conventional iron-supplemented cow's milk (10-15 mg Fe/qt; casein P:Fe congruent to 34), absorption of iron(III) from the casein or NTA complex was not significantly different. There was no significant difference in the absorption of iron administered to mice and chicks as ferrous ion, ferric-NTA, or ferric fructose; nonfat cow's milk did not inhibit the absorption of these iron compounds. For the chick, in fact, milk significantly enhanced the absorption of iron from the ferric-NTA chelate. In order to affect iron absorption significantly casein would have to be present considerably in excess of that found in conventionally supplemented cow's milk.

Absorption↗