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Biomedical subjects

J D Cook

Publications and source records attributed to J D Cook.

At least 163 records · Page 9Linked to original sources
PubMed1982

A screening test for assessing iron status.

Intervention strategies to combat iron deficiency anemia in developing countries may hasten the development of iron overload in patients with an inherited defect in hemoglobin synthesis. This risk could be diminished if there was a rapid and simple method available for detecting iron overload in population screening programs. We have developed such a method, which is in effect a semiquantitative ferritin measurement based on a modification of a two-site enzyme-linked immunoassay. The assay requires only 2 drops of whole blood and a total incubation time of 90 min. The procedure, which can readily distinguish iron deficiency from even a modest increase in storage iron, has a potentially wide application in settings where a prompt assessment of iron status is required.

Anemia, Hypochromic↗
PubMed1981

The inhibitory effect of soy products on nonheme iron absorption in man.

Radioiron absorption studies were performed in male volunteer subjects to determine the effect on nonheme iron absorption of various semipurified proteins. When egg albumen and casein were substituted in protein-equivalent quantities in a semisynthetic meal, similar mean absorptions of 2.5 and 2.7% were observed. In contrast, isolated soy protein reduced absorption sharply, to an average of 0.5%. When egg albumen in the semisynthetic meal was replaced with full fat soy flour, textured soy flour, and isolated soy protein, absorption fell from 5.5 to 1.0, 1.9, and 0.4%, respectively, indicating an inhibitory effect by a wide range of soy products. The effect of substituting textured soy flour for meat in a meal containing a hamburger, french fries, and a milkshake was also evaluated. With 3:1 and 2.1 ratios of meat to unhydrated textured soy flour, absorption decreased by 61 and 53%, respectively. The soy products tested in this study have a pronounced inhibitory effect on the absorption of nonheme iron.

Absorption↗
PubMed1981

Iron availability from infant food supplements.

Radioiron absorption tests are performed in human volunteer subjects to measure iron absorption from five infant food supplements. These products included corn-soya-milk, corn-soy blend, wheat-soy blend, wheat protein concentrate blend, and whey-soy drink mix. In iron replete adult males, mean percentage absorption ranged from 0.6 to 1.4%. By relating these results to absorption from a reference dose of inorganic iron, it was estimated that iron-deficient infants would absorb between 1.7 and 4.1% of the iron contained in the infant foods. These results indicate that this fortification iron is poorly absorbed, and probably supplies only about half of the daily iron requirement for iron deficient children between 6 months and 3 yr of age.

Absorption↗
PubMed1981

The inhibitory effect of bran on iron absorption in man.

The effects of whole wheat bran and its components on the absorption of nonheme dietary iron were measured using a double isotope technique in human volunteers. When 12 g bran was added to a light meal, absorption decreased by 51 to 74%; this inhibitory effect of bran was shown for meals of both high and low iron availability. Inhibition was not explained by monoferric phytate, the major form of iron in bran, because labeled iron from monoferric phytate was absorbed at least as well as the common pool of nonheme dietary iron. Furthermore, removal of phytate from bran by endogenous phytase did not in itself alter the inhibitory effect of the bran on iron absorption. Studies in which dephytinized bran was separated into a soluble, phosphate-rich fraction and an insoluble, high-fiber fraction indicated that the soluble fraction was more inhibitory than the insoluble fraction.

Adult↗
PubMed1981

Diagnosis and treatment of neuromuscular disease.

There are over 50 treatable conditions that can produce signs and symptoms of fatigue, weakness, sensory complaints, or muscle atrophy [Table 3]. The examiner should be able easily to identify, by history and physical examination, the affected site of the motor unit causing the patient's syndrome. Following this, by using other aspects of the history and physical examination, the clinician can decide which are treatable disorders by appropriate selection of the laboratory studies. Thus, any patient who complains of neuromuscular symptoms can be approached as if he had a potentially treatable disorder and not merely as a diagnostic curiosity.

Anterior Horn Cells↗
PubMed1981

Role of gastric acid in food iron absorption.

Radioiron absorption tests in human volunteers demonstrated a modest but significant 28% reduction in the absorption of dietary nonheme iron from a meal that was preceded by the administration of 300 mg cimetidine. More pronounced decreases of 42% and 65% were observed with 600 and 900 mg cimetidine, respectively. Antacid caused a 52% decrease in iron absorption whereas pentagastrin had no significant effect. Since 300 mg cimetidine reduces gastric acid secretion by 60%-80% but iron absorption by only 28%, it appears that under normal conditions more gastric acid is secreted than is required for optimal iron absorption; absorption falls only when acid secretion is markedly reduced. Cimetidine in the doses currently recommended would not be expected to have a major effect on iron nutrition, although the combination of high doses of cimetidine with antacids would impair nonheme iron absorption significantly.

Absorption↗
PubMed1980

Idiopathic hemochromatosis, an interim report.

Experience over the last 20 years with 34 patients with idiopathic hemochromatosis is summarized and the literature is reviewed. Methods are now available which are highly effective in the diagnosis of iron overload and virtually all diagnoses are made antemortem. The nature of the disease has changed through the removal of iron by phlebotomy. Early deaths are limited to patients with severe and rapidly progressive heart disease and to those presenting with neoplasm. The major mortality has shifted to a much later period and the incidence of hepatoma is increasing. There is particular interest at the present time in family studies since excessive iron stores are frequently found within the family. The significance of intermediate degrees of iron overload is unclear, but future attention should be given to the recognition of iron overload long before clinical manifestations appear.

Bloodletting↗
PubMed1980

Interaction of vitamin C and iron.

Food iron is absorbed by the intestinal mucosa from two separate pools of heme and nonheme iron. Heme iron, derived from hemoglobin and myoglobin, is well absorbed and relatively little affected by other foods eaten in the same meal. On the other hand, the absorption of nonheme iron, the major dietary pool, is greatly influenced by meal composition. Ascorbic acid is a powerful enhancer of nonheme iron absorption and can reverse the inhibiting effect of such substances as tea and calcium/phosphate. Its influence may be less pronounced in meals of high iron availability--those containing meat, fish, or poultry. The enhancement of iron absorption from vegetable meals is directly proportional to the quantity of ascorbic acid present. The absorption of soluble inorganic iron added to a meal increases in parallel with the absorption of nonheme iron, but ascorbic acid has a much smaller effect on insoluble iron compounds, such as ferric oxide or ferric hydroxide, which are common food contaminants. Ascorbic acid facilitates iron absorption by forming a chelate with ferric iron at acid pH that remains soluble at the alkaline pH of the duodenum. High cost and instability during food storage are the major obstacles to using ascorbic acid in programs designed to combat nutritional iron deficiency anemia.

Animals↗
PubMed1980

The clinical significance of ferritinuria.

Urinary ferritin levels were measured by a "2-site" immunoradiometric assay in normal volunteers and in patients with various hematologic disorders. The mean urinary ferritin concentration in normal subjects averaged 2.2 microgram/liter, only 3% of the serum ferritin level. Elevated urinary ferritin levels averaging 45 microgram/liter were observed in patients with hematologic malignancies, but there was a proportional increase in serum ferritin so that the urinary level still averaged only 7% of the serum value. The highest urinary ferritin values (mean 170 microgram/liter) were associated with chronic hemolytic anemia, and in these patients, urinary ferritin rose disproportionately in relation to the serum, averaging 82% of it. This higher urinary level apparently reflects increased ferritin in renal tubular cells due to glomerular filtration of unbound hemoglobin, a mechanism that is supported by a highly significant correlation between urinary ferritin and serum haptoglobin levels. In normal subjects and in patients with malignancy, the source of urinary ferritin appears different, since a highly significant correlation was observed between urinary ferritin and reticuloendothelial iron stores as measured by serum ferritin or total iron-binding capacity. In this setting, the most likely source of urinary ferritin is the iron contained in renal tubular cells, which is apparently in equilibrium with body iron stores.

Adult↗
PubMed1980

Mucosal iron transport by rat intestine.

Using highly sensitive 2-site immunoradiometric assays, we examined the relationship between iron absorption from closed intestinal loops and transferrin and ferritin concentrations in isolated duodenal mucosal cells. As in prior studies, mucosal ferritin correlates inversely with iron absorption and directly with body iron stores as measured by the concentration of nonheme iron in liver. Mucosal transferrin, on the other hand, varies directly with both the total mucosal uptake of radioiron and the proportion of this radioiron transferred from the mucosa to the carcass. The highest correlation with iron absorption was observed with the transferrin-ferritin ratio in isolated mucosal cells. These results suggest that there are two functionally distinct iron-binding compartments in the duodenal mucosa. One is a strong compartment, ferritin, and the other is a transport compartment, transferrin. Control of iron absorption by the intestinal mucosa is closely tied to the balance between these two intracellular iron compartments.

Absorption↗
PubMed1979

Assessing iron status of a population.

Reliable methods for assessing the iron status of a population are essential for developing effective public health measures to combat iron deficiency. The hemoglobin concentration, transferrin saturation, free erythrocyte protoporphyrin, and serum ferritin are all useful but they vary widely in their specificity and sensitivity for detecting iron deficiency. In applying these laboratory parameters, the usual approach in nutritional surveys is to determine the percentage of values outside the normal range. As an alternative, a model is presented here that uses these measurements to estimate the distribution of iron stores in a population. This approach may be particularly useful for evaluating the effectiveness of iron supplementation and fortification programs.

Adult↗
PubMed1979

Food iron absorption in human subjects. V. Effects of the major dietary constituents of semisynthetic meal.

Studies were performed in adult volunteer subjects to determine the effect on nonheme iron absorption of protein, carbohydrate, and fat. These constituents were administered as egg albumin, dextrimaltose, and corn oil, respectively, in a semisynthetic meal containing 700 kcal and 4.1 mg iron. Because any one of these ingredients are unpalatable when administered alone, their effect was determined by serially deleting or doubling their content in the basal semisynthetic meal. With both approaches, carbohydrate and fat had little influence whereas egg albumin had a significant inhibitory effect on the absorption of nonheme iron.

Absorption↗
PubMed1979

Absorption of monoferric phytate by dogs.

Recent studies have shown that the iron in wheat is predominantly in the form of monoferric phytate (MFP). Unlike phytate complexed with two or more iron atoms, MFP is soluble at pH 7.0 and above and may therefore be a relatively available form of dietary iron. To examine this point, we tested iron absorption in adult dogs using a double radioisotope method and total body counting. When given without food, MFP was about one-half as available as ferrous sulphate at an iron-equivalent dose of 1.5 mg and only about one-seventh as available at a dose of 15 mg iron. When administered with food, MFP underwent complete isotopic exchange with the nonheme pool of dietary iron. When added to meals of either high or low iron availability in amounts that might be used for iron fortification, the absorption was the same for MFP iron as for the major pool of dietary inorganic iron.

Animals↗