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J D Cook

Publications and source records attributed to J D Cook.

At least 109 records · Page 6Linked to original sources
PubMed1989

The clinical measurement of serum transferrin receptor.

Monoclonal antibody reagents were used to develop a sensitive enzyme-linked immunoassay for clinical measurement of circulating transferrin receptor. By using transferrin-bound receptor for the preparation of the immunologic reagents, we developed an assay that gives an identical dose-response curve with either free or transferrin-bound receptor. The mean concentration of circulating receptor in 82 normal male and female volunteers was 5.63 +/- 1.42 mg/L. The level was reduced significantly in patients with primary aplastic anemia and post-transplant aplasia (2.58 +/- 1.07 mg/L and 2.32 +/- 0.48 mg/L, respectively) and was sharply elevated in patients with hemolytic anemia and iron deficiency anemia (33.1 +/- 17 and 18.0 +/- 11.4 mg/L, respectively). Our assay values are approximately 20-fold higher than results published previously in a study that used an immunoradiometric assay. The disparity apparently relates to a difference in sensitivity of the latter assay for free and transferrin-bound receptor. Measurements of serum transferrin receptor provide a useful clinical index of either total or iron-deficiency erythropoiesis.

Adult↗
PubMed1988

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.

Adult↗
PubMed1988

Iron absorption from fortified flat breads.

1. Radio-iron absorption measurements were performed in healthy volunteer subjects to assess the availability of fortification Fe added to various bread products. 2. When ferrous sulphate was used as a fortifier, Fe absorption from a traditional Egyptian flat bread (Baladi) averaged only 16% of that observed with European bread. This difference was attributed to the high extraction flour used to prepare Baladi bread. 3. The inhibiting effect of Baladi bread was largely eliminated by adding EDTA to the flour before baking.

Adult↗
PubMed1988

Iron absorption in humans: bovine serum albumin compared with beef muscle and egg white.

We studied the influence of bovine serum albumin and beef meat on nonheme iron absorption in humans and on dialyzable iron in vitro. The addition of serum albumin to a maize gruel had no significant effect on nonheme Fe absorption whereas the addition of beef meat caused a threefold increase. When added to a bread meal, serum albumin caused a modest 60% increase in nonheme Fe absorption and beef meat had no effect. When added to a protein-free meal, serum albumin reduced Fe absorption by 47% compared with a 72% reduction on addition of egg white. The bioavailability of nonheme Fe from meals containing serum albumin was consistently overestimated by the in vitro technique. We conclude that the facilitation of nonheme Fe absorption by meat is not a general property of all animal protein but is better explained by the action of one or more specific animal tissues.

Adult↗
PubMed1988

An immunoassay for human transferrin.

The laboratory measurement of serum transferrin is a valuable adjunct in the assessment of both iron and protein nutritional status. Conventional assays based on the Fe-binding properties of this protein are tedious to perform, susceptible to Fe contamination, and require volumes of serum that can only be obtained by venous sampling. We describe in this report a two-site enzyme immunoassay (EIA) developed with the use of monoclonal antibodies. Ten microliters serum is diluted 1:20,000 before assay, reflecting a high degree of sensitivity. The variability of this EIA is comparable to conventional colorimetric assays for total iron-binding capacity (TIBC), and excellent correspondence was observed between these methods over a range in TIBC of 150-500 micrograms/dL (27-90 mumol/L). No consistent difference was observed with the EIA when performed on venous and capillary specimens obtained simultaneously. This method will facilitate the evaluation of Fe and protein status in nutritional surveys.

Animals↗
PubMed1988

Interaction of acidic isoferritins with human promyelocytic HL60 cells.

We have used undifferentiated human promyelocytic HL60 cells to study the binding of radioiodinated human ferritin in vitro. Specific binding of human heart ferritin could be demonstrated at 37 degrees C, whereas no binding of liver ferritin could be found. The uptake of labelled heart ferritin was abolished by incubation at 4 degrees C, by prior treatment of the HL60 cells with pronase and by the addition of human plasma to the medium. On the other hand, the addition of excess unlabelled human liver or rat liver ferritin had no effect on the uptake of labelled human heart ferritin. Dissociation studies showed that about 55% of the bound heart ferritin radioactivity could be released by incubation with medium alone and at least 90% with excess unlabelled heart ferritin. Over 70% of the dissociated ferritin could be precipitated with polyclonal anti-ferritin serum or trichloroacetic acid. More than two-thirds of the radioactivity which could not be released after washing in medium alone was recovered in the soluble intracellular fraction following cell lysis. Almost all of the soluble radioactivity could be precipitated with the polyclonal antiserum, indicating that very little lysosomal degradation of internalized heart ferritin had occurred. The present studies demonstrate a protein-mediated binding mechanism for acidic isoferritins on HL60 cells. These observations agree with published evidence that ferritin is often associated with cell membranes and are consistent with a possible role for the protein in the regulation of haematopoiesis or in iron transfer.

Cell Line↗
PubMed1987

Stability of radioiodinated ferritin.

Ferritin which had been radioiodinated using chloramine T exhibited marked instability on storage at 4 degrees C. Both [125I]human liver and heart ferritins showed a similar rate of decline in immunoreactivity (t 1/2 = 20-23 days) indicating that deterioration with storage was not a function of isoferritin composition. The decrease in radioactivity associated with ferritin was due not only to loss of 125I from the molecule but also to protein degradation as shown by enzyme-linked immunoassay and gel filtration. The degradation products had an Mr of at least 69,000 although low Mr material could be identified by gel filtration when a marked reduction in immunoreactivity had occurred. Ferritin instability was much more pronounced than when other proteins such as immunoglobulin and albumin were radioiodinated with chloramine T. These observations indicate that when performing in vivo and in vitro studies with labeled ferritin, degradation of the protein during storage should be carefully monitored and the protein repurified before use.

Antibodies↗
PubMed1987

Mammalian folylpoly-gamma-glutamate synthetase. 4. In vitro and in vivo metabolism of folates and analogues and regulation of folate homeostasis.

The regulation of folate and folate analogue metabolism was studied in vitro by using purified hog liver folylpolyglutamate synthetase as a model system and in vivo in cultured mammalian cells. The types of folylpolyglutamates that accumulate in vivo in hog liver, and changes in cellular folate levels and folylpolyglutamate distributions caused by physiological and nutritional factors such as changes in growth rates and methionine, folate, and vitamin B12 status, can be mimicked in vitro by using purified enzyme. Folylpolyglutamate distributions can be explained solely in terms of the substrate specificity of folylpolyglutamate synthetase and can be modeled by using kinetic parameters obtained with purified enzyme. Low levels of folylpolyglutamate synthetase activity are normally required for the cellular metabolism of folates to retainable polyglutamate forms, and consequently folate retention and concentration, while higher levels of activity are required for the synthesis of the long chain length derivatives that are found in mammalian tissues. The synthesis of very long chain derivatives, which requires tetrahydrofolate polyglutamates as substrates, is a very slow process in vivo. The slow metabolism of 5-methyltetrahydrofolate to retainable polyglutamate forms causes the decreased tissue retention of folate in B12 deficiency. Although cellular folylpolyglutamate distributions change in response to nutritional and physiological modulations, it is unlikely that these changes play a regulatory role in one-carbon metabolism as folate distributions respond only slowly. 4-Aminofolates are metabolized to retainable forms at a slow rate compared to folates. Although folate accumulation by cells is not very responsive to changes in folylpolyglutamate synthetase levels and cellular glutamate concentrations, cellular accumulation of anti-folate agents would be highly responsive to any factor that changes the expression of folylpolyglutamate synthetase activity.

Animals↗
PubMed1987

Use of capillary blood for the evaluation of iron status.

The accuracy and precision of measurements of iron status made on the capillary blood from a single 75 X 1-mm microhematocrit tube were evaluated in 301 normal volunteers. After recording the hematocrit value, a hematofluorometer was used to assay erythrocyte protoporphyrin directly on the packed red cell fraction. Values in the low normal range were 50-100% higher than assays by an extraction technique in simultaneously collected venous blood. However, measurements in the iron deficient range were only 12% greater. Plasma ferritin concentration was determined by using an enzyme-linked immunoassay on 10-microliters plasma retrieved after measuring the hematocrit. Capillary values were approximately 7% higher than venous concentrations, the proportional difference being consistent throughout the measured range. When the individual measurements were combined to calculate the iron storage status of each individual, the frequency distribution of iron stores in 141 female volunteers between 18 and 36 years of age was approximately Gaussian and paralleled that calculated for women aged 18-44 years in NHANES II. These studies demonstrate that iron status can be determined accurately from the measurement of hematocrit, erythrocyte protoporphyrin, and ferritin on a single microhematocrit tube of capillary blood.

Adolescent↗
PubMed1987

Intestinal regulation of body iron.

A significant proportion of the world's population suffers from iron deficiency or iron overload. These disorders arise primarily from defects in the gastrointestinal absorption of iron. The intestinal mucosal cell plays a key role in this process because it lies at the interface between the gastrointestinal lumen which supplies its iron and body compartments which control its behaviour. The concentration of mucosal ferritin is closely linked to absorption, but it is still not clear whether it plays an active or a passive role. Transferrin also has been detected in the mucosal cell, but firm evidence that it participates in the absorptive process is lacking. Deficiencies in the luminal phase are responsible for the high global prevalence of iron deficiency which is predominantly dietary in origin. Much information has accumulated in recent years on dietary factors that enhance or impair iron absorption but their quantitative importance as determinants of iron status remains to be determined.

Humans↗
PubMed1987

Screening test for iron overload.

It is presently estimated that 2-3/10(3) people living in the United States are homozygous for the iron-loading gene and are thereby susceptible to severe iron overload. The complications of this disorder can be prevented if recognized in the asymptomatic precirrhotic stage. We have developed a simple, inexpensive screening method for its early laboratory detection based on the fact that one of the earliest laboratory manifestations of hemochromatosis is a reduction in unsaturated iron-binding capacity. The sequential addition of a small measured quantity of saturating iron and bathophenanthroline disulfonate will result in color with highly saturated but not with normal sera. This screening test almost completely differentiated between 40 normal individuals and 40 patients with iron overload (as defined by a transferrin saturation greater than 55%). The test provides a cost-effective method for screening large segments of the population to detect this genetic disorder.

Adult↗
PubMed1987

Specific binding of acidic isoferritins to erythroleukemia K562 cells.

An investigation of ferritin binding by human erythroleukemia K562 cells was prompted by recent studies suggesting that acidic isoferritins may act as regulators of granulopoiesis and hemopoiesis. Purified human heart and liver ferritins were labeled with iodine 125 and incubated with K562 cells at 37 degrees C. Specific uptake was calculated from the reduction in labeled ferritin binding in the presence of a 1000-fold excess of unlabeled ferritin. Specific uptake of 125I-labeled heart ferritin increased progressively, reaching a maximum after 2 to 3 hours' incubation, although nonspecific binding was too high to derive an affinity constant. There was no specific binding with 125I-labeled liver ferritin, and K562 cells bound neither 125I-labeled human serum albumin nor free 125I. Uptake of heart ferritin was negligible at 4 degrees C and was sharply reduced in the presence of 10% human plasma or fetal calf serum. There was no apparent relationship between the number of days of subculture and the level of uptake of acidic isoferritins by whole cells. These studies demonstrate a selective binding mechanism for acidic isoferritins on erythroleukemia cells and imply that these isoferritins have additional functions besides the storage of iron.

Animals↗
PubMed1987

Strength evaluation in neuromuscular disease.

Strength evaluation in neuromuscle disease is necessary to track the natural history of the disease, to understand its pathophysiology, to determine the efficacy of treatment, and, most importantly, to evaluate an experimental treatment regimen. This article describes the physiology of muscle activity, discusses fatigue, examines various testing methods, and suggests appropriate measurements to assess the neuromuscular patient's strength and endurance in a variety of clinical settings. The minimal amount of equipment necessary to follow patients with NMD is a stop watch, a goniometer, a hand-held dynamometer, a hand-grasp dynamometer, and a creative mind.

Biomechanical Phenomena↗
PubMed1986

Cerebrospinal fluid ferritin levels in screening for meningism.

To evaluate the potential diagnostic value of the ferritin concentration in cerebrospinal fluid (CSF), measurements were performed with an immunoradiometric assay in 23 control patients and in 65 patients with various neurologic disorders. The geometric mean ferritin level of 3.5 micrograms/L in controls was approximately 10% of the level in normal serum with an upper cutoff level of 10 micrograms/L. Only modest elevations in CSF ferritin concentration were observed in patients with viral meningitis and in those with various non-infectious neurologic disorders. On the other hand, marked elevations ranging between 27 and 322 micrograms/L (geometric mean, 90 micrograms/L) were observed in patients with bacterial or fungal meningitis. Results of the study indicate that CSF ferritin levels are a valuable adjunct in the early evaluation of patients presenting with meningism.

Cell Count↗
PubMed1986

A serum ferritin assay for prevalence studies of iron deficiency.

A specialized serum ferritin assay has been developed for the detection of iron deficiency in epidemiologic studies. An enzyme immunoassay (EIA) was employed to eliminate the need for radioisotopes. The problem of low sensitivity inherent with the EIA for serum ferritin was eliminated by the use of monoclonal immunologic reagents. The working range of the assay is 1-100 micrograms/L with a sensitivity of 0.5 micrograms/L. Excellent agreement in serum ferritin levels was observed between the present method and the two-site immunoradiometric assay (IRMA), while the variability at low ferritin concentrations was significantly less with the EIA. Because only 10 microliter of serum is required for each assay, duplicate measurements can be performed on a single capillary tube of blood. When an automatic microtiter plate reader for optical density measurements is used, 80-100 duplicate determinations can be completed by one technologist in a single working day.

Anemia, Hypochromic↗
PubMed1986

The liabilities of iron deficiency.

Iron has been recognized as a potent hematinic since the inception of hematology as a clinical discipline. Even ancient civilizations believed in the beneficial effects of medicinal iron. Nevertheless, the precise functional liabilities of iron lack remain the subject of continuing debate. The consequences of iron deficiency, particularly from a socioeconomic standpoint, are especially important in light of its high global prevalence. A recent review of the literature indicates that approximately 30% of the estimated world population of nearly 4.5 billion are anemic, and at least half of these, 500 to 600 million people, are believed to have iron deficiency anemia.

Adult↗