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R J Keller

Publications and source records attributed to R J Keller.

At least 19 recordsLinked to original sources
PubMed1991

Spectrophotometric and ESR evidence for vanadium(IV) deferoxamine complexes.

Complexes of vanadium(IV), vanadyl, are reported to be formed with the trihydroxamic acid deferoxamine (H3DF+). One complex exhibits a reddish-violet color, with a major absorbance peak at 386 nm and a smaller peak at 520 nm. This complex is potentially useful for the microdetermination of vanadyl. The apparent molar absorptivity is 3.91 mM-1 cm-1, and the complex obeys Beer's law in the concentration range of 0.6-63 ppm. Electron spin resonance studies indicate the formation of two vanadyl complexes that are 1:1 in vanadyl and deferoxamine, but have two or three bound hydroxamate groups. ESR and spectrophotometric evidence indicate that the red, low pH form, involves an octahedral vanadium (4+) ion coordinated by three hydroxamate ligands. One of these hydroxamates is displaced by an oxygen at pH greater than 2.8 according to the following equilibria: VO2+ + H3DF+ in equilibrium with VIV(DF)2+ + H3O+, VIV(DF)2+ + H2O in equilibrium with VO(HDF)+ + H+, where pk2 = 2.8.

Deferoxamine↗
PubMed1991

Nonpalpable ductal carcinoma in situ versus infiltrating carcinoma of the breast--can they be differentiated by mammography?

The radiologic patterns of 193 consecutive women with nonpalpable breast carcinoma were evaluated. The results were correlated with patient age and with the histopathologic diagnosis. Of the 193 women in the study, 135 (70%) were older than 50 years; 102 women had ductal carcinoma in situ, and 67 (62%) of them were over age 50; the remaining 91 women had infiltrating carcinoma, and 73 (80%) of these patients were older than 50 years. Of the 58% of women who presented with microcalcifications, 75% had ductal carcinoma in situ and 25% infiltrating carcinoma. Of the 36% of patients who presented with a mass, 87% had infiltrating carcinoma and 90% were over age 50. Six percent presented with a mass with microcalcifications; 75% of these masses were found to be infiltrating carcinoma. Most of the masses were infiltrating carcinoma, and of these 90% were high-density masses. The small number of masses representing ductal carcinoma in situ were proportionately of low density.

Adult↗
PubMed1990

Cellular immunity to human insulin in individuals at high risk for the development of type I diabetes mellitus.

In order to investigate the role of insulin as a potential target autoantigen of cellular immunity in the prediabetic period, proliferative responses of T lymphocytes to human insulin were studied in nine islet-cell antibody (ICA) + first-degree relatives of patients with Type I diabetes (individuals at high risk for the development of Type I diabetes, or the 'prediabetic' group, which was never treated with insulin) and in 12 control individuals. Insulin autoantibodies were present in 6/9 (67%) of the prediabetic subjects and none of the controls. Peripheral blood lymphocytes were collected on Ficoll and incubated with human insulin, control antigens, or media alone for 5-6-day and 9-10-day incubation periods. Cells were pulsed with 3H-thymidine, harvested, and analysed in a scintillation counter. Results are expressed as stimulation index (SI = cpm with antigen/cpm without antigen), with a SI greater than or equal to 1.5 considered a positive response. Eight of nine (89%) prediabetic individuals responded positively to insulin after a 9-10-day incubation period, in contrast to four of 12 (33%) control subjects, P less than 0.05. The mean proliferative response to insulin after 9-10 days' incubation was 2.1 +/- 0.4 and 1.2 +/- 0.1, for the prediabetic and control groups, respectively. The proliferative response to insulin was not directly correlated with levels of insulin autoantibodies (r = -0.05, NS). These data suggest that most individuals at high risk for the development of Type I diabetes display a cellular immune response to insulin, and a subset of these individuals does not display a concomitant humoral immune response to insulin based on the presence or absence of insulin autoantibodies.

Adolescent↗
PubMed1990

Glucose therapy for glycogenosis type 1 in infants: comparison of intermittent uncooked cornstarch and continuous overnight glucose feedings.

This study was undertaken to test the glycemic response of five infants with glycogen storage disease type 1, aged 0.7 to 1.5 years, to uncooked cornstarch under various dietary conditions, and to evaluate the long-term effects of a dietary regimen consisting of uncooked cornstarch in milk every 4 hours, in addition to three meals daily, on biochemical values and physical growth. The results were compared with previous experience in treating six infants with continuous overnight glucose infusion via gastrostomy plus multiple daily feedings containing an adequate source of glucose. A test dose of cornstarch (1.6 to 1.8 gm/kg) providing four times the calculated hourly glucose production rate, when given in water 15 to 30 minutes after a continuous overnight intragastric glucose infusion was stopped, did not maintain normoglycemia. When the same dose was given in 2% cow milk 4 hours later, mean blood glucose levels remained greater than 68 mg/dl (3.8 mmol/L) for up to 4 hours. A regimen of uncooked cornstarch in 2% cow milk at 4-hour intervals in addition to three meals daily prevented hypoglycemia, and maintained blood lactate at nearly normal levels and serum uric acid and cholesterol within the normal range; triglyceride levels were increased only modestly. Overnight blood glucose levels were comparable to those achieved with continuous intragastric glucose infusion. With this regimen the five infants have maintained linear growth rates normal for their age and genetic potential; the mean percentage of ideal body weight for length percentile did not change significantly, although two of the five patients were overweight (123% and 124% of ideal body weight respectively) after 3 years of treatment. We conclude that a trial of uncooked cornstarch in feedings of milk every 4 hours should be attempted as soon as a more frequent feeding schedule with dextrose-containing formulas proves ineffective, because the former has the potential to provide the continuous glucose required by infants with glycogen storage disease type 1 in a safer and less invasive fashion than continuous intragastric glucose infusion.

Blood Glucose↗
PubMed1990

Nonpalpable breast masses: radiologic predictability of malignancy.

Of 568 nonpalpable breast lesions detected by screening mammography 242 proved to be noncalcified masses; biopsy showed 165 to be benign and 77 malignant. The lesions were evaluated with respect to contour, radiographic density and size. Of the malignant lesions 90% were infiltrating carcinomas, 88% of which had an indistinct contour and were of moderate to high density. Of the benign lesions 40% of those with an indistinct contour demonstrated high radiographic density. Low-density, distinct masses were all benign. There was no correlation between the size of the lesion and whether it was malignant.

Aged↗
PubMed1989

Oxidation of NADH by vanadium compounds in the presence of thiols.

The nonenzymatic oxidation of NADH was studied spectrophotometrically in the presence of two vanadium compounds, sodium orthovanadate and vanadyl sulfate. At physiological pH 7.4, in 25 mM sodium phosphate buffer, addition of the synthetic thiol, dithioerythritol (DTE) results in a marked increase of NADH oxidation in the presence of sodium orthovanadate, but not in the presence of vanadyl sulfate. Other reductants, such as dithiothreitol and cysteine, can also increase NADH oxidation, whereas glutathione and ascorbate cannot. In all reactions, superoxide dismutase and catalase completely inhibit the vanadium-stimulated oxidation of NADH. Inhibition occurs in a concentration-dependent manner, and the boiled enzymes do not inhibit the thiol reaction. The hydroxyl radical scavenger, thiourea, inhibits the reaction, whereas urea cannot. ESR studies show that the ability of the thiol to reduce vanadate can be correlated with the degree of NADH oxidation. Using spin trapping techniques, hydroxyl radicals are detected during the course of the reaction. Addition of hydrogen peroxide to vanadyl in the presence of DTE greatly increases NADH oxidation; however, no NADH oxidation occurs when hydrogen peroxide is added to vanadyl and ascorbic acid. These results provide a partial explanation for the ability of vanadium compounds to both decrease cellular reducing equivalents and promote lipid peroxidation.

Ascorbic Acid↗
PubMed1989

Jejunal interposition.

Seventeen cases of jejunal interposition for distal esophageal lesions, primarily achalasia, eventuated in excellent clinical function in almost all patients. These results compare favorably with other reported series of the same procedure. The radiologic appearance of the anastomosis with the few complications that occur, however, have not been emphasized and are presented in this paper.

Adult↗
PubMed1989

Importance of hydroxyl radical in the vanadium-stimulated oxidation of NADH.

Vanadium compounds are known to stimulate the oxidation of NAD(P)H, but the mechanism remains unclear. This reaction was studied spectrophotometrically and by electron spin resonance spectroscopy (ESR) using vanadium in the reduced state (+4, vanadyl) and the oxidized state (+5, vanadate). In 25 mM sodium phosphate buffer at pH 7.4, vanadyl was slightly more effective in stimulating NADH oxidation than was vanadate. Addition of a superoxide generating system, xanthine/xanthine oxidase, resulted in a marked increase in NADH oxidation by vanadyl, and to a lesser extent, by vanadate. Decreasing the pH with superoxide present increased NADH oxidation for both vanadate and vanadyl. Addition of hydrogen peroxide to the reaction mixture did not change the NADH oxidation by vanadate, regardless of concentration or pH. With vanadyl however, addition of hydrogen peroxide greatly enhanced NADH oxidation which further increased with lower pH. Use of the spin trap DMPO in reaction mixtures containing vanadyl and hydrogen peroxide or a superoxide generating system resulted in the detection by ESR of hydroxyl. In each case, the hydroxyl radical signal intensity increased with vanadium concentration. Catalase was able to inhibit the formation of the DMPO--OH adduct formed by vanadate plus superoxide. These results show that the ability of vanadium to act in a Fenton-type reaction is an important process in the vanadium-stimulated oxidation of NADH.

Cyclic N-Oxides↗
PubMed1989

Mucosal proctectomy and ileoanal anastomosis.

The classical surgical therapy of ulcerative colitis and familial polyposis has been total proctocolectomy and ileostomy. In order to avoid a cutaneous stoma and to achieve continence without disruption of gastrointestinal continuity, responding to a demand particularly among younger patients, a mucosal proctectomy in association with an ileoanal anastomosis has been devised. The addition of an ileal reservoir proximal to the anastomosis results in fewer bowel movements and a greater degree of continence. In our series of 70 cases, we have analyzed the normal roentgen anatomy of the ileoanal anastomosis and the proximal ileal reservoir and present our findings on plain film and contrast examinations. To assess patients postoperatively, the radiologist should be aware of the basic surgery involved and the normal roentgen anatomy resulting from this procedure.

Adenomatous Polyposis Coli↗
PubMed1988

Vanadium and lipid peroxidation: evidence for involvement of vanadyl and hydroxyl radical.

The present study was designed to determine which form of vanadium is involved in initiating conjugated diene formation in both purified and partially peroxidized fatty acids, and to determine if active oxygen radicals are involved in this process. We report that vanadyl is the active form of vanadium in initiating conjugated diene formation in micelles prepared from purified fatty acids or partially peroxidized fatty acids. Vanadate did not initiate conjugated diene formation in either case. Hydroxyl radicals were shown to be involved in the initiation of diene conjugation when vanadyl and hydrogen peroxide were added together in a reaction mixture. In this case, there was a rapid burst of conjugated diene formation which quickly leveled off. Using spin trapping techniques, hydroxyl radicals were shown to be generated in the vanadyl-catalyzed break-down of fatty acid hydroperoxides. A comparison was made between the ability of vanadyl or vanadyl chelates to decompose hydrogen peroxide and catalyze the decomposition of fatty acid hydroperoxides. It was found that strongly chelated vanadyl (vanadyl/EDTA) was much less effective in decomposing both hydrogen peroxide and fatty acid hydroperoxides than the weak vanadyl chelates (e.g., vanadyl/ADP). This study suggests a mechanism to explain the effects of vanadium on lipid peroxidation.

Electron Spin Resonance Spectroscopy↗
PubMed1987

Vanadate-dependent oxidation of pyridine nucleotides in rat liver microsomal membranes.

An enzymatic Na3VO4-dependent system for the oxidation of reduced pyridine nucleotides in purified rat liver microsomes was characterized. The system has a pH optimum of 6.5, and appears to be specific for vanadate, since activity in the presence of a related transition metal, molybdate, was not detected. Vanadate-dependent oxidation occurred with a concomitant consumption of O2 and, contrary to previous reports, preferred NADPH over NADH. At pH 6.5, the NADPH/NADH oxidase activity ratio was greater than 2:1. Sodium vanadate-dependent oxidation of NADH was inhibited by rotenone, antimycin A, NaN3, and NaCN. Conversely, Na3VO4-dependent NADPH oxidation was slightly affected by rotenone, but was insensitive to antimycin A, NaN3, NaCN, or quinacrine. Vanadate-dependent oxidation of either pyridine nucleotide was inhibited by the addition of either superoxide dismutase or catalase, indicating that both superoxide and hydrogen peroxide may be intermediates in the process. Linear sucrose gradient purification of the microsomes showed that the vanadate-dependent system for NADPH oxidation resides primarily in the endoplasmic reticulum. These studies indicate the existence of separate and distinct enzymatic systems for vanadate-stimulated oxidation of NADPH and NADH in mammalian microsomal membranes, and argue against an exclusive role of endogenous superoxide in the process.

Animals↗
PubMed1985

In vitro and in vivo effects of vanadate on K+-dependent phosphatase activities from subcellular fractions of brain, kidney and liver.

Inhibition of K+-dependent phosphatases by sodium orthovanadate was studied in the subcellular fractions of brain, kidney and liver from male Sprague-Dawley rats. The concentration required to produce an in vitro phosphatase inhibition of 50% ranged from a low of 0.2 microM in the kidney 900 X g fraction to a peak of 400 microM in the brain soluble fraction. The concentrations required to produce 50% inhibition occurred in the micromolar range for most fractions studied. Injection of sodium vanadate (i.p., 8 mg/kg) produced phosphatase inhibition in several of the fractions, but not as pronounced as the in vitro treatment. The results indicate that vanadate is a potent inhibitor of phosphatase activity in vitro, and may have similar potential in vivo.

Animals↗
PubMed1985

Esophageal moniliasis: a new radiographic presentation.

A previously unreported manifestation of esophageal moniliasis is described. Two patients with acquired immunodeficiency syndrome and Kaposi's sarcoma presented with solitary esophageal ulcers. Endoscopic biopsy confirmed the clinical diagnosis of esophageal moniliasis. The clinical and radiographic features of esophageal moniliasis are described.

Acquired Immunodeficiency Syndrome↗