Conrad A. Knutsen

Effects of hepatic arterial yttrium 90 glass microspheres in dogs

A 22‐μm glass microsphere called TheraSphere (Theragenics Corp., Atlanta, GA) has been developed in which yttrium 89 oxide is incorporated into the glass matrix and is activated by neutron bombardment to form the beta‐emitting isotope yttrium 90 (Y 90) before using the spheres as radiotherapeutic vehicles. The injection of up to 12 times (on a liver weight basis) the anticipated human dose of nonradioactive TheraSphere into the hepatic arteries of dogs was well tolerated and produced clinically silent alterations within centrolobular areas. The hepatic arterial (HA) injection of radioactive TheraSphere also produced portal changes similar to those observed in humans after external beam therapy. While the extent of damage increased with the delivered dose, radiation exposures in excess of 30,000 cGy did not cause total hepatic necrosis and were compatible with survival. No microspheres distributed to the bone marrow and absolutely no myelosuppression was encountered in any animal. Proposed hepatic exposures to humans of 5000 to 10,000 cGy by means of these microspheres, therefore, would appear to be feasible and tolerable. Radiotherapeutic microsphere administration preceded by regional infusion of a radiosensitizing agent and/or immediately following the redistribution of blood flow toward intrahepatic tumor by vasoactive agents can potentially yield a synergistic, highly selective attack on tumors confined to the liver.

Effect of zinc on increasing oxygen affinity of sickle and normal red blood cells

Abstract We have hypothesized a state of zinc deficiency in sickle cell disease (SCD). This could at least partially explain the growth problems, hypogonadism, and slow healing leg ulcers associated with SCD. Preliminary findings revealed abnormally low red blood cell zinc levels in 10 of 16 patients studied. Before suggesting zinc supplementation in SCD we thought it important to look at the effect of zinc on red cell metabolism and function. It was found that zinc chloride added to normal and SCD blood to a final concentration of 1.5 × 10 −3 M caused a left-shift of the blood oxygen affinity curve (increased oxygen affinity) varying from 1.5 to 3.5 mm Hg change in half saturation (p50). This curve shifting property has important implications for SCD since recent work with cyanate suggests that such shifts are very beneficial in treatment of SCD. Thus zinc supplementation in SCD, in addition to its potential role in correcting wound healing and growth problems, may have a beneficial effect on the basic pathological process. Data are given which suggest that zinc and 2, 3-diphosphoglycerate may not be competing for the same site on the hemoglobin molecule.

Studies on the interaction of zinc with human hemoglobin

Abstract Zn has previously been shown to increase the oxygen affinity of both normal and sickle red blood cells. Experiments are presented which demonstrate that the oxygen affinity effect of Zn is due to a Zn-hemoglobin binding mechanism rather than a Zn-2,3 diphosphoglycerate binding mechanism. Further a large shift (6 mm Hg) in the oxygen affinity of a red cell-saline suspension occurs with a low Zn/hemoglobin (tetramer) molar ratio (0.4). Zn had no influence on the Bohr effect of hemoglobin but it did decrease the Hill coefficient. Hemoglobin binding experiments using partially purified hemoglobin indicated that Zn can bind to more than one amino acid residue but it appears that the amino acid residue with the highest binding capacity for Zn is also the residue involved in the oxygen affinity effect of Zn. Hydrogen ion concentration (pH 5–8) had no influence on the Zn/hemoglobin ratios obtained in these binding experiments. The possible (and the improbable) Zn binding sites on the hemoglobin molecule are discussed.

Hexokinase isozyme variability in Drosophila robusta

Several isozymes of hexokinase have been found in Drosophila robusta. These have been defined in this paper in several dimensions, including genetic variation, ontogenic variation, tissue-organ variation, and substrate specificity.

Potential Effects of Hemoglobin Concentration on Red Cell Metabolism Together with Observations on Red Cell Metabolic Differences Between Men and Women

One of our major interests has been the glycolytic control mechanisms in the red cell which determine DPG levels normally and during hypoxic stress. We have increasingly utilized the method of assaying the measurable intermediates throughout the glycolytic pathway, along the lines suggested by Yoshikawa and Minakami (1968), in order to determine the key enzymatic step or steps which bring about changes in DPG. Through these studies we have begun to discern a rather consistent pattern, suggesting that the activity of hexokinase, already known to be one of the key regulators of erythrocyte glycolysis (Rapoport, 1968; Yoshikawa and Minakami, 1968), may be a very important factor in regulating DPG levels, in a number of circumstances. This pattern is illustrated in papers on anemia (Oelshlegel, et al. 1972) and altitude adaptation (Moore, et al. 1972) in this volume, but we would also like to illustrate it in the first part of this paper in differences between normal men and women.

A Dog Model Using an implanted System for Protracted Hepatic Arterial Chemotherapy

A model for hepatic arterial chemotherapy studies using large dogs and an implantable infusion pump has been developed. Using this technique near complete perfusion (greater than 90%) of the liver can be achieved in vivo as determined by hepatic arterial perfusion scintigraphy with technitium 99m macroaggregated albumin. The system is reliable and has been in use for a total of 1353 days (mean of 104 days, range 52-239) in 13 dogs. Pump implantation causes no apparent acute liver damage based on pre- and post-operative alkaline phosphatase and serum glutamic-pyruvic transaminase determinations and does not affect the general mobility or behavior of the animals. Careful placement of the catheter and attention to the physicochemical properties of the solutions loaded are factors contributing to the success of the model. The model permits comprehensive preclinical pharmacokinetic and toxicologic studies of new or preexistent chemotherapeutic agents in the same device that will be used for later administration in human subjects. By providing the means to examine and develop new treatment modalities, it enables the design of even more potent cytotoxic therapy directed into the tumor vascular bed.

A technique for the processing of blood samples for subsequent assay of ATP, and an investigation of the method of standardization of the firefly-luciferase ATP assay☆

Quantitative measurement of adenosine triphosphate (ATP) in erythrocytes is of increasing interest in genetic studies of human population groups I. The concentration of ATP in erythrocytes appears to be under at least partial genetic control*?*, and recently has been shown to be of potential significance in selective processes related to malariaa. In addition, measurement of erythrocytic ATP is of importance in certain clinical situation+, particularly in connection with blood bankingh-11. At present, accurate evaluation of the physiological level of ATP of erythrocytes can only be made on reasonably fresh blood samples, and then only if the samples are stored in acid-citrate-dextrose (ACD) solution and kept carefully refrigerated at all times12. Even with such precautions, appreciable changes in levels of ATP may occur after only a few days of storage. A method is herein described in which blood can be collected and processed in the field, the samples stored in the frozen state for up to six weeks, and accurate determination of ATP subsequently made in the investigator’s base laboratory. In addition, we have reinvestigated the method of standardization employed in the firefly-luciferase luminescence assay for ATP of erythrocytes13.

A simple method for long-term biliary access in large animals.

A simple method to obtain long-term access to the biliary tree in dogs and pigs is presented. In ten dogs and four pigs, a cholecystectomy was performed, the cystic duct isolated, and a catheter inserted into the cut end of the cystic duct. The catheter was connected to a subcutaneous infusion port, producing a closed, internal system to allow long-term access. The catheter placement was successful in three of the pigs and all of the dogs. Thirty-five cholangiograms were obtained in the 13 subjects by accessing the port with a 20 gauge Huber needle and injecting small amounts (4-10 mL) of contrast under fluoroscopic control. Cholangiograms were obtained up to four months after catheter placement without evidence for catheter failure or surgically induced changes in the biliary tree. This model provides a simple, reliable means to obtain serial cholangiograms in a research setting.