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Biomedical subjects

S R Lynch

Publications and source records attributed to S R Lynch.

At least 55 records · Page 3Linked to original sources
PubMed1982

Reduction of the soy-induced inhibition of nonheme iron absorption.

Recent studies in normal men have demonstrated that soy products have a pronounced inhibitory effect on the absorption of nonheme dietary iron. The purpose of the present investigation was to explore approaches to overcoming this inhibition. A modest but significant increase in iron absorption was observed when test meals containing either isolated soy protein or whole soybeans were baked at 200 degrees C. The addition of 100 mg ascorbic acid to a meal containing isolated soy protein had a more dramatic effect, increasing mean absorption from 0.6 to 3.2%. A similar but less pronounced increase was observed when meat was added to the isolated soy protein meal. These results indicate that the inhibitory effect of soy can be reversed to some extent by substances known to enhance nonheme iron absorption.

Adolescent↗
PubMed1982

Iron status of elderly Americans.

Studies of iron nutriture in the elderly are limited and very few include observations on individuals over the age of 75. The two Health and Nutrition Examination Surveys carried out by the United States Department of Health, Education and Welfare demonstrate that the mean iron intake of Americans is adequate until the age of 75. However, with changes in the major food sources there is a decrease in iron derived from meat and a concomitant rise in the proportion supplied by breakfast cereals. Alterations in dietary iron bioavailability++ that may result from this have not been studied. Physiological data suggest that the elderly do not represent a target population for iron deficiency since iron requirements are no greater than those of adult men and lower than those of children and menstruating women. Furthermore, there is little direct evidence of a high prevalence of iron deficiency in the elderly, but the laboratory measurements that have proved useful in defining iron status in younger people have not been standardized for or extensively used in older people. Anemia is still the most important known consequence of significant iron deficiency. However, the application of Hb or hematocrit standards used in younger people to the elderly as well as the assumption that anemia can be equated with iron deficiency invalidates the conclusions of many surveys. Hb and hematocrit measurements are not suitable screening tests for iron deficiency in the elderly and there is an urgent need for a clearer understanding of the physiological and nutritional factors responsible for lower Hb values in older people, particularly older Blacks.

Adolescent↗
PubMed1982

Myelosuppression in Legionnaires' disease.

A patient undergoing examination for moderately severe renal insufficiency had fulminant five-lobed pneumonia caused by Legionella pneumophila. Her clinical course was complicated by granulocytopenia. Bone marrow aspiration showed notable inhibition of myelopoiesis, involving all stages of maturation. The presence of a serum inhibitor of granulopoiesis was demonstrated by in vitro bone marrow culture. Normal bone marrow cultured in the presence of serum from two normal control subjects yielded 69 +/- 5.2 (mean +/- SE) and 61 +/- 5 granulocyte colonies. When the patient's serum was substituted for normal human serum only 14.3 +/- 2.3 colonies were formed. Each of the drugs to which she had been exposed was tested in the in vitro system, using therapeutic concentrations, and none showed significant suppression of granulocyte colony formation. These observations indicate that legionnaires' disease was associated with a serum factor that notably inhibited the growth of granulocyte colonies in this patient.

Aged↗
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

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

Equilibration of tracer radioiron with body iron.

1. The degree to which a tracer quantity of 55Fe bound to transferrin and introduced into the plasma 36 months previously had equilibrated with the body iron was studied in a subject who was phlebotomized repeatedly until iron-deficiency anaemia developed. 2. Analysis of the results with two mathematical models showed that equilibration with haemoglobin iron and storage iron was complete. 3. Estimates of the quantity of iron initially stored in the body by three different methods yielded values of 37.3, 33.1 and 34.8 mmol. 4. Since the previously determined mean initial plasma ferritin concentration was 185 micrograms/1 (462 pmol/1), there was 0.179-0.197 mmol of stored iron per 1 microgram of plasma ferritin/1. 5. The study suggests that the assumption on which currently accepted values for daily body iron loss were calculated is valid.

Anemia, Hypochromic↗
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

Iron overload.

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Bloodletting↗
PubMed1978

B- and T-cell markers in lymphoproliferative disorders with blood and bone marrow involvement.

B- and T-cell surface markers were determined in 26 adult patients with lymphoproliferative malignancies who had bone marrow and blood involvement. The patients in whom more than 60% of the abnormal cells were immunoglobulin-bearing cells were considered to have B-cell lymphoproliferative malignancy. The diagnosis of a T-cell disorder was made in those patients in whom more than 70% of the cells formed E rosettes (T cells). Those patients in whom 30% and more of the abnormal cells did not show B- and T-cell surface markers were regarded as suffering from "null" cell disorder. The B-cell type of lymphoproliferative malignancy was the most commonly encountered (63%) with an equal male to female ratio. In addition, 4 male patients with "hairy-cell" leukaemia were shown to have a B-cell disorder. T-cell disorders were found in 3 male patients; 1 patient had acute lymphoblastic leukaemia and in the other 2 the histopathological diagnosis was well-differentiated lymphoma and Sternberg sarcoma. Four patients with "null" cell lymphoma were found, the histopathological diagnoses in all were poorly-differentiated lymphocytic lymphoma, and 3 of the 4 patients were males. Further haematological investigations of the B-cell and the non-B-cell disorders showed that although the bone marrow was equally extensively infiltrated in both groups, the non-B-cell disroders were more commonly associated with complications of anemia and thrombocytopenia. It is therefore postulated that the abnormal lymphoid cell involved in B-cell disorders is an end-stage cell and not the haemopoietic stem cell.

Adult↗
PubMed1978

Fanconi's anaemia, with special reference to erythrokinetic features.

Serial haematological investigations were carried out in 5 patients with Fanconi's anaemia over periods of 6 months--11 years. All the patients were pancytopenic with a depression of the granulocytic and megakaryocytic elements of the bone marrow throughout the greater part of their illnesses. Erythropoietic acitvity was variable. The initial bone marrow examination revealed depressed erythroid function in 3 patients. The erythroid hypoplasia persisted in 2 of them, while in the third, erythroid activity increased with time, possibly as the result of therapy with oxymetholone. Erythroid hyperplasia was present in the remaining 2 patients, both at presentation and throughout the course of the illness. This could not be attributed to treatment in either patient. Six erythrokinetic studies were carried out in the 5 patients at variable intervals after the diagnosis had been made. In 2 studies erythroid activity was unequivocally depressed, while in a further 3 a significant, though probably suboptimal, erythroid marrow response was present. In the final study erythropoiesis was increased but was markedly ineffective in terms of the delivery of viable red cells into the circulation. In vivo counting suggested that some degree of ineffective erythropoiesis was also present in the other patients and studies with 51Cr indicated a shortened red cell survival in all subjects studied. In 2 of them significant splenic sequestration was present. Leukaemic transformation occurred in 2 patients. In 1 of them its development was heralded by the appearance of micromegakaryocytes in the bone marrow.

Adolescent↗
PubMed1978

The mechanism of endotoxin-induced hypoferraemia.

The effect of endotoxin on the processing of erythrocyte iron by reticuloendothelial cells of the liver and spleen was studied in rats using heat damaged erythrocytes labelled with 59Fe. Endotoxin did not alter the uptake of the damaged cells but markedly inhibited the subsequent early phase of iron release from the reticuloendothelial cells. The inhibition seemed to be due to both a decreased rate of labelled haem destruction and an increased incorporation of radioiron into ferritin. Although early iron release was decreased 0--2 h after endotoxin administration, the diversion of iron into ferritin was more marked when endotoxin was given 18 h before. The block in iron release was partially overcome in animals that had been kept on an iron free diet or had been phlebotomised. In these animals the decreased rate of haem catabolism remained unaltered but less iron was diverted into ferritin.

Anemia, Hypochromic↗
PubMed1977

Anaemia, iron deficiency and exercise: extended studies in human subjects.

1. Ventilation and cardiac frequency were measured during repeated treadmill exercise in three healthy subjects over 36 weeks, before, during and after iron-deficiency anaemia was produced and after iron treatment. The haemoglobin and 2,3-diphosphoglycerate concentrations and the oxygen-binding (P50) were measured. 2. There was an inverse relationship between the haemoglobin concentrations and the 2,3-diphosphoglycerate concentrations and the P50 values. 3. The mean cardiac frequencies during the fourth to tenth minutes of exercise showed a negative correlation with the haemoglobin concentrations in all three subjects, and the mean minute ventilations in two of them.

Adult↗