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Biomedical subjects

P A McIntyre

Publications and source records attributed to P A McIntyre.

At least 19 recordsLinked to original sources
PubMed1983

The folacin contents of foods as measured by a radiometric microbiologic method.

A radiometric microbiologic assay for folate was applied to measure food folacin levels. Sixteen different foods were analyzed. The total folacin content of the 16 foods obtained by the radiometric microbiologic method was found to compare well with that obtained by the turbidimetric microbiologic method. The folacin content ranged from 9 ng/ml of frozen reconstituted grape juice to 1820 micrograms/100 g of the cereal Total. The study showed that the radiometric microbiologic assay can be used to measure folacin content in foods.

Biological Assay↗
PubMed1983

111In oxine-labeled rabbit platelets: in vivo distribution and sites of destruction.

We have studied the kinetics, biodistribution, and fate of autologous platelets labeled with 111In-oxine in rabbits. The initial recovery was 75% and mean survival time was 2.8 days when the data were analyzed by the multiple-hit gamma function model. Using a modified geometric mean for correction of attenuation, there was good correlation between the values obtained by in vivo quantification and those obtained by postmortem measurements of the radioactivity in the liver and the spleen (i.e., r = 0.854 and 0.899, respectively, n = 32). Using this method, it was shown that after infusion, the 111In-platelets rapidly accumulated in these two organs reaching 35% and 12% of the injected dose in the liver and spleen, respectively, by 1 day. Thereafter, there was little subsequent change. On the sixth day, when essentially all of the 111In-platelets had cleared from the circulation, a total of 82% of the injected dose was deposited in the three major reticuloendothelial organs: liver (40%), spleen (14%), and bone marrow (28%). Our results suggest that in addition to liver and spleen, bone marrow played an important role in sequestering platelets in rabbits.

Animals↗
PubMed1982

Kinetics and distribution of 111Indium-labeled platelets in patients with homocystinuria.

Homocystinuria is an inborn error of metabolism involving a high incidence of thromboembolism. It sometimes improves with large doses of pyridoxine. We investigated the kinetics and distribution of 111Indoxine-labeled platelets in 11 normal volunteers and 12 patients with homocystinuria, none of whom had clinical evidence of acute thrombosis at the time of the study. Six of the patients were resistant to pyridoxine and had homocystinemia. There were no statistical differences in mean platelet-survival times between pyridoxine responders and nonresponders or between normal subjects and pyridoxine responders or nonresponders, regardless of whether a linear, exponential, or multiple-hit model was used to analyze the kinetic data. Plasma homocystine levels had no apparent effect on mean platelet-survival time. There was no abnormal accumulation of platelets in any of the patients, and the distribution of platelets in liver and spleen was similar to that in normal subjects. Our results suggest that the kinetics and distribution of platelets in patients with homocystinuria who have no clinical evidence of thromboembolism are normal. Thus, the data do not provide evidence for disordered platelet function or for an ongoing interaction of platelets with vessel walls in this condition.

Adolescent↗
PubMed1982

Human platelets labeled with In-111 8-hydroxyquinoline: kinetics, distribution, and estimates of radiation dose.

Platelets from nine normal male subjects were labeled with In-111 8-hydroxyquinoline (In-111 oxine) in the presence of plasma in either "closed" blood transfer packs or in "open" test tubes. The mean labeling efficiencies in these two systems were 27 and 53%, respectively. Mean survival time of In-111-labeled autologous platelets was 8.76 days, with a standard deviation of 1.05 according to the maximum-likelihood estimate of the gamma-function model. The initial recovery of In-111 platelets in the circulation was 57% with a standard deviation of 11%. The distribution of In-111 platelets in liver and spleen was quantitated by anterior, posterior, and transmission gamma-camera imaging. During the first 30 min, 38% of the injected dose accumulated in the spleen, 13% in the liver. No significant increase in In-111 radioactivity was observed in either of the two organs over a 3-9-day period. The bone marrow was an additional site of In-111 accumulation. The spleen was the critical organ with respect to radiation dose. The splenic dose was estimated to be 34 rad/mCi In-111 platelets, that of the liver 2.1 rad/mCi. With the injection of 100-150 microCi of In-111-labeled platelets in normal subjects, giving a splenic radiation of 5 rad, a complete 10-day survival study can be performed and uptake of In-111 in different organs can be measured quantitatively for at least 3-4 days.

Adult↗
PubMed1981

Radiometric-microbiologic assay fo vitamin B-6: analysis of plasma samples.

A radiometric microbiologic assay for the analysis of vitamin B-6 in plasma was developed. The method is based on the measurement of 14CO2 generated from the metabolism of DL-l-14C-valine (L-l-14C-valine) by Kloeckera brevis. The assay is specific for the biologically active forms of the vitamin, that is, pyridoxine, pyridoxal and pyridoxamine, and their respective phosphorylated forms. The biologically inert vitamin B-6 metabolite (4-pyridoxic acid) did not generate a response at concentrations tested. The radiometric technique was shown to be sensitive to the 1 nanogram level. Reproducibility and recovery studies gave good results. Fifteen plasma samples were assayed using the radiometric and turbidimetric techniques. The correlation coefficient was r = 0.98. Turbid material or precipitated debris did not interfere with the radiometric microbiologic assay, thus allowing for simplification of assay procedure.

Animals↗
PubMed1981

Radiometric--microbiologic assay of vitamin B-6: application to food analysis.

A radiometric microbiologic assay for vitamin B-6 was applied to food analysis. The method was shown to be specific, reproducible and simpler than the standard turbidimetric microbiologic technique. The analysis of seven commercially available breakfast cereals was compared to a high performance liquid chromatography method. Three out of the seven cereals agreed when assayed with both methods (P greater than 0.1). Four cereals, however, differed in value considerably (P less than 0.05). Further studies are required to determine whether these differences were due to different extraction procedures used. The study showed that the new radiometric-microbiologic method can be used to measure total vitamin B-6 or, combined with a column separation procedure, to analyze for specific forms of the vitamin.

Biological Assay↗
PubMed1980

Growth response of the yeasts Saccharomyces uvarum and Kloeckera brevis to the free biologically active forms of vitamin B-6.

The ideal microorganism for the microbiological assay of total vitamin B-6 should respond equally to all forms of vitamin B-6. The yeasts Saccharomyces uvarum (ATCC 9080) and Kloeckera brevis (ATCC 9774) were compared in their ability to utilize pyridoxine, pyridoxal and pyridoxamine in the concentration range needed for the measurement of vitamin B-6 in biological materials. Our results showed that K. brevis responded equally to all three free forms of vitamin B-6 at a dosage range of 2--10 ng molar equivalent of pyridoxine. In contrast, S. uvarum, which is currently widely used for the vitamin B-6 assay, had a significantly different growth response to three forms of vitamin B-6 at the comparable dosage range. The results suggest that the yeast K. brevis is better suited for the microbiological assay of total vitamin B-6.

Biological Assay↗
PubMed1979

Labeling of human platelets with [111In) 8-hydroxyquinoline.

We have evaluated the factors influencing the labeling of human platelets in the presence of autologous plasma. The labeling efficiency was found to be dependent on a) the time and temperature of incubation, b) the platelet concentration, c) the concentration of citrate ions (in ACD anticoagulant), and d) the concentration of 8-hydroxyquinoline in the suspending medium. Contrary to what was expected, unsaturated transferrin was found not to interfere with the transfer of In-111 from the [111In] 8-hydroxyquinoline complex to the platelets. Based on the findings of this study, a protocol was established by which human platelets can be labeled with In-111 in plasma with a labeling efficiency of 55.5 +/- 9.3 (mean +/- 1 s.d.) percent.

Anticoagulants↗
PubMed1979

A radiometric microbiologic assay for the biologically active forms at niacin.

A radiometric microbiologic assay has been developed for the determination of niacin in biologic fluids. Lactobacillus plantarum produced 14CO2 from L-[U-14C] hr malic acid in quantities proportional to the amount of niacin present. The assay is specific for the biologically active forms of niacin in humans. Thirty normal hemolysates were analyzed and the values ranged from 13.0 to 17.8 micrograms niacin/ml RBC (mean = 15.27 +/- 1.33 s.d.). Good recovery and reproducibility studies were obtained with this assay. On thirty blood samples, correlation was excellent between the radiometric and the conventional turbidimetric assays.

Animals↗
PubMed1978

Neuronal ceroid-lipofuscinosis. Studies of granulocyte enzyme activities.

Neuronal ceroid-lipofuscinosis is characterized by pigmentary degeneration of the retina, psychomotor degeneration, epilepsy and intracellular deposition of ceroidlipofuscin. Recent reports have suggested that deficiency of peroxidase is the basic genetic defect. However, deficiency of myeloperoxidase could be demonstrated in some but not all patients; this deficiency was noted only when p-phenylenediamine (PPD) was used as hydrogen donor and could not be confirmed with guaiacol. We found that horseradish peroxidase (HR-P) oxidized PPD in the absence of added H2O2. The oxidative product of PPD showed the same absorption spectrum as the peroxidative product. The oxidation of PPD by HR-P was not inhibited by catalase or superoxide dismutase. In addition, catalase oxidized PPD in the presence of H2O2. Soluble and granular fractions obtained from human polymorphonuclear leukocytes (PMN) also oxidized PPD in the absence of H2O2. Addition of H2O2 inhibited the oxidation of PPD in some cell fractions. This inhibition could be partially eliminated by dialysis of the cell fractions. Thus, PPD is not a suitable hydrogen donor for the study of peroxidase. This may explain the variable results obtained by the previous investigators. In contrast, guaiacol did not show these undesirable characteristics. The PMN peroxidase (measured with guaiacol), catalase, beta-glucuronidase, acid and alkaline phosphatases were studied in individuals from three families with juvenile neuronal ceroid-lipofuscinosis. Family 1: an affected boy and healthy parents; all showed normal enzyme activities in both soluble and granular fractions. Family 2: two affected sisters, one healthy sib and mother, and Family 3: one affected boy; all showed reduced peroxidase activities in the granular fractions. Other enzymes were normal. The role of peroxidase deficiency in the pathogenesis of neuronal ceroid-lipofuscinosis is not clear. The basic defect of this syndrome remains uncertain.

Acid Phosphatase↗
PubMed1978

Rapid radiometric susceptibility testing of Mycobacterium tuberculosis.

A 48-hour radiometric test for determining the drug susceptibility of Mycobacterium tuberculosis has been developed. The test is based on the measurement of 14CO2 produced by the oxidation of formate labeled with carbon-14. The test system uses 5 X 10(7) organisms in 1 ml of Middlebrook 7H9 medium plus albumin-dextrose-catalase enrichment and 1 muCi of [14C]formate. The 14CO2 produced is measured in an ionization chamber at 24-, 48-, and 72-hour intervals, with and without the addition of antituberculous drugs. Isoniazid, streptomycin, rifampin, and ethambutol were each tested at 3 concentrations by the radiometric method and the reference (agar dilution) method. Six standard strains and 21 patient isolates were compared by both methods. Production of 14CO2 was quantitatively decreased in the presence of drugs that inhibit the organism. The radiometric method requires 2 days; the agar dilution, 14 to 21 days.

Antitubercular Agents↗
PubMed1978

Tc-99m human serum albumin: a suitable agent for plasma volume measurements in man.

In 16 patients we have carried out simultaneous plasma-volume measurements with human serum albumins tagged with Tc-99m (Tc-99m HSA) and I-131 (I-131 HSA). The correlation coefficient was 0.987. Tc-99m HSA, prepared from kits that predictably yield high labeling efficiency (and thereby negligible amounts of TCO4-), is clearly a superior agent for repeat plasma volume determinations, because of its shorter half-life and the reduced radiation dose to the subject.

Humans↗
PubMed1978

Measurement of folates in human plasma and erythrocytes by a radiometric microbiologic method.

A radiometric microbiologic assay for the determination of folic acid in human plasma and red blood cells is described. The assay is based upon the measurement of 14CO2 produced from the metabolism of [1-14C] gluconate by Lactobacillus casei. The 14CO2 evolved was shown to be proportional to the amount of added DL-N-5-methyltetrahydrofolage (DL-N-5-methyl FH4). A total of 26 normal plasma and 57 blood hemolysates were assayed in parallel by this radiometric and the standard (turbidimetric) microbiologic assay. The correlation coefficients for the two assays were r = 0.96 for plasma and r = 0.98 for red-cell folate. Lyophilization of L. casei was found to simplify this radiometric assay by eliminating routine maintenance and culture of this microorganism.

Biological Assay↗
PubMed1977

Functional development of phagocytic activity of the spleen.

The improvement of phagocytic activity of organs was studied in rats by means of 99mTc sulfur colloid uptake. This function was measured in the newborn rat, 1-, 2-, 3-, and 4-week-old baby rats and in adult rats. Organ distribution of the 99mTc-S-colloid showed marked phagocytic activity of the liver in all age groups including the newborn period. Phagocytosis in bone marrow was markedly increased and that in spleen markedly decreased at the time of birth. However, rapid improvement of phagocytic activity with age was prominent in the spleen.

Animals↗
PubMed1977

Hydrogen peroxide production and killing of Staphylococcus aureus by human polymorphonuclear leukocytes.

The effects of bacterial neuraminidase on production of hydrogen peroxide (H2O2) and killing of Staphylococcus aureus by human polymorphonuclear leukocytes (PMN) were studied. The concentration of H2O2 was measured by the disappearance of scopoletin fluorescence in the presence of horseradish peroxidase. The results indicated that desialylation of human PMN inhibited the stimulation of H2O2 production during phagocytosis. It also markedly impaired the killing of S. aureus. Impaired killing of S. aureus by desialylated PMN was due to impaired intracellular killing rather than defective phagocytosis.

Blood Bactericidal Activity↗
PubMed1977

Evaluation of indium-111 as a new high photon yield gamma-emitting "physiological" platelet label.

In order to evaluate indium-111 (111In) as a "physiological" platelet label, rabbit platelets were labeled in vitro with 111In-8-hydroxyquinoline. The in vivo behavior of 111In labeled platelets was then compared with that of chromium-51 51Cr) labeled platelets in the rabbit. Several important features were evident. First, unlike 51Cr, reasonable platelet labeling efficiency could be achieved with 111In, even when the platelets were suspended in small amounts of autologous plasma. Second, the initial recovery of platelets at 20 minutes after infusion was significantly higher for the 111In labeled platelets than for 51Cr labeled platelets, providing the platelets were suspended and "washed" in plasma. Third, the mean survival time of 111In labeled platelets, as estimated using four different mathematical models, was comparable with that of 51Cr platelets. Finally, the high photon yield of gamma emitting 111In, unlike 51Cr, permits quantitative gamma camera imaging of the in vivo distribution of labeled platelets. Thus, this nuclide possesses advantages as a platelet label that will foster statistically more accurate kinetic research as well as quantitative in vivo distribution studies in humans.

Animals↗