Edward C. Knoblock

The determination of chromium in biological materials by atomic absorption spectroscopy.

Abstract Biological samples were mineralized with a mixture of nitric, sulfuric, and perchloric acids. The chromium was oxidized to chromium(VI) followed by extraction into methyl isobutyl ketone in the cold. The ketone extract was aspirated into a fuel-rich hydrogen-air flame, and the absorption recorded using the 357.9 nm line of chromium. The limit of detection for chromium was found to be 10 p.p.b. Tissue chromium levels of normal albino rats were determined. Increased chromium values were observed for animals maintained on a high chromium diet compared to those fed a deficient diet.

A polarographic study of chromium-insulin-mitochondrial interaction

Abstract 1. 1. Insulin exhibits a polarographic wave due to the reduction of a disulfide group. This wave most probably arises from the reduction of the intrachain disulfide. 2. 2. Chromium(III) forms complexes with insulin and mitochondria, both complexes involving chromium-sulfur linkages. 3. 3. Insulin reacts with mitochondria through the formation of a sulfhydryl-disulfide linkage. This reaction is enhanced by the presence of chromium(III).

Heparin-calcium complexes as a measure of serum low-density lipoproteins

Abstract The cholesterol and phospholipid content of serum calcium-heparin complexes agreed quite well with the low-density lipoprotein fractions obtained by ultracentrifugation. A significant difference was found in myocardial infarct patients compared to controls.

Polarographic study of copper complexes with radiation protective drugs correlation of instability constant with radiation prophylaxis

Abstract A correlation has been demonstrated between the instability constant of the copper-agent complex and the protective capacity of the agent against ionizing radiation. The instability constants for the complexes formed between copper and 8 agents have been. reported in a Michaelis phosphate buffer of pH 7–4.

APPARENT INSTABILITY CONSTANTS OF 2-MERCAPTOETHYLAMINE COMPLEXES

The apparent instability constants of the MEA complexes of Zn, Co, Cd, and Cu were determined polarographically in a phosphate buffer of pH 7.4 and in a sodium bicarbonate solution. In these media, the Zn complex is least strong and the Cu complex rnost strong. These data are discussed in relation to the role of Zn in enzymatic oxidation. (auth)

Inaccuracies in digoxin measurement

Six commercial digoxin immunoassay kits were evaluated for their accuracy of calibration and their extent of interference by digoxin-like immunoreactive substance (DLIS). Calibration accuracy was investigated with digoxin reference standards in pooled human serum. The Abbott and Becton Dickinson kits underestimate while the other kits overestimate digoxin concentration. The magnitude of this bias generally increases with increasing concentration of digoxin. Sera from digoxin-free patient populations with potential DLIS interference--pregnant women, newborns, hypertensives, and uremics--were analyzed with each kit. Healthy subjects not on digoxin therapy served as controls. Groups with DLIS interference, as exemplified by a significant difference of p less than 0.05 from controls, are: Abbott--newborns and pregnant women; Becton Dickinson--newborns and pregnant women; Dade--no difference; Dupont--newborns, uremics, pregnant women, and hypertensives; Kallestad--newborns; and Syva--newborns. The limitations of each individual digoxin method should be realized for DLIS interference and bias, and patient results from that method should be interpreted accordingly.

Polarographic study of mitochondrial suspensions

Abstract 1. 1. Mitochondrial suspensions exhibit a characteristic polarographic wave which is independent of tissue source. This same wave was found in the mitochondria of two species of animals. 2. 2. This polarographic wave is anodic in character, irreversible, and diffusion controlled. 3. 3. The anodic process results in the formation of a mercury mercaptide. The source of mercaptan in fresh mitochondrial preparations is sulfhydryl groups within the mitochondrial membrane. These appear to be due to sulfhydryl groups contained in the protein structure of the mitochondrial membrane. 4. 4. Aging of the mitochondrial preparation results in loss of the early wave and the appearance of a second wave. This latter wave originates from the contents of the mitochondria.

Effect of Salicylates on Respiration and Phosphorylation in Heart Mitochondria

Summary 1) The polarographic method for measuring changes in O2 concentration has been employed for assessing ability of salicylates and related compounds to uncouple phosphorylation. The extent of stimulation of respiration caused by addition of these compounds to rat heart mitochondria oxidizing alpha-ketoglutarate in a phosphate-acceptor deficient system was used as a criterion of uncoupling action. 2) Thiosalicylate was many times more active than salicylate and other salicy late-derivatives tested. Some chemical and physical properties possibly responsible for the uncoupling action of salicylate and certain of its congeners were considered. The in vitro action of salicylates was discussed in relation to their anti-rheumatic activity and cardiovascular effects.