Search PubMed⌕ Search

Biomedical subjects

J D Cook

Publications and source records attributed to J D Cook.

At least 199 records · Page 11Linked to original sources
PubMed1977

Effect of blood donation on iron stores as evaluated by serum ferritin.

Serum ferritin was measured in 2982 blood donors. First-time male donors had a geometric mean of 127 microgram/liter and female donors 46 microgram/liter. While values were essentially constant in the women between the ages of 18 and 45, there was a rapid increase in the men between 18 and 30 years of age consistent with the establishment of iron stores during that time. Blood donation was associated with a decrease in serum ferritin. One unit per year, equivalent to an increased requirement of 0.65 mg/day, halved the serum ferritin level in the male. More frequent donations were associated with further decreases. From the data obtained it would appear that male donors, while depleting their iron stores, were able to donate 2-3 U/yr without an appreciable incidence of iron deficiency. Women could donate only about half that amount, and more frequent donations were associated with a high incidence of iron deficiency and donor dropout. These data have provided information on the effect of graded amounts of iron loss through bleeding on iron balance.

Adolescent↗
PubMed1976

Slow saccades in spinocerebellar degeneration.

Two patients with spinocerebellar degeneration made abnormally slow horizontal refixations. One patient produced quick phases of nystagmus with identical maximum velocities, suggesting her refixations were abnormal saccades and not voluntary pursuit movements. In response to double target jumps, neither patient showed an obligatory refractory period after each saccade; they responded to every target movement after one reaction time. Their slow refixations were not preprogrammed since they could be modified in flight. To reconcile these observations with normal saccadic behavior, we hypothesized a neural network that made saccades by driving the eyes to an orbital position rather than preprogramming a distance for movement. Computer simulation of this model produced both realistically appearing normal saccades and, when appropriately "lesioned" to simulate a loss of saccadic "burst" neurons in the pontine reticular formation, slow saccades that could be modified in flight.

Adolescent↗
PubMed1976

Food iron absorption in human subjects. IV. The effects of calcium and phosphate salts on the absorption of nonheme iron.

The influence of physiological levels of calcium and phosphorus on the absorption of nonheme iron from a semisynthetic meal was evaluated. Each of the 34 participating subjects received two to four test meals. In three studies where both calcium and phosphate were added, absorption of nonheme iron was reduced to 27 to 47% of that absorbed when no salts were added. However, with the single addition of either calcium or phosphate to the test meals no significantly inhibiting effect was observed. As the absorption of nonheme iron was significantly reduced only with the combined addition of calcium and phosphate, it is suggested that a calcium-phosphate-iron complex forms which inhibits iron absorption.

Absorption↗
PubMed1976

Food iron absorption in man II. The effect of EDTA on absorption of dietary non-heme iron.

One hundred and eighty iron absorption tests were performed in 45 normal men to determine the effect of EDTA on the absorption of dietary non-heme iron. The addition of 50 mg EDTA to test meals containing 4.1 mg iron reduced absorption by approximately one-half from meals of both high (standard meal) and low (semisynthetic meal) iron availability. Studies employing dual radioiron labels demonstrated complete isotopic exchange of ferric EDTA with dietary non-heme iron. Further studies were carried out to determine the decrease in food iron absorption at varying levels of EDTA. At a 1:1 molar ratio of EDTA to iron, absorption of non-heme iron was reduced to 72% and at a 2:1 molar ratio, to 50% of absorption without EDTA. These levels of EDTA are within the range believed to be present in the United States diet.

Adolescent↗
PubMed1976

Food iron absorption in human subjects. III. Comparison of the effect of animal proteins on nonheme iron absorption.

The ability of various animal proteins to enhance the absorption of dietary nonheme iron was evaluated by performing multiple radioiron absorption measurements in 70 volunteer subjects. Protein equivalent substitutions of nine animal foods were made in two basic test meals. The first was a standard meal of high iron availability (mean absorption, 8.3%) containing beef muscle as the animal protein. The second was a semisynthetic meal of low iron availability (mean absorption, 1.4%) containing ovalbumin as the protein source. Two categories of animal protein were defined. Substitution of beef, lamb, pork, liver, fish, and chicken for the egg ovalbumin in the sannisynthetic meal resulted in a significant, 2-fold to 4-fold increase in iron absorption whereas no increase was observed with milk, cheese, or egg. Reciprocal findings were obtained when these foods were substituted for the beef contained in the standard meal. All sources of animal proteins are not equivalent in their effect on nonheme iron absorption.

Absorption↗
PubMed1976

Evaluation of the iron status of a population.

The iron status of a population of 1564 subjects living in the northwestern United States was evaluated by measurements of transferrin saturation, red cell protoporphyrin, and serum ferritin. The frequency distribution of these parameters showed no distinct separation between normal and iron-deficient subjects. When only one of these three parameters was abnormal (transferrin saturation below 15%, red cell protoporphyrin above 100 mug/ml packed red blood cells, serum ferritin below 12 ng/ml), the prevalence of anemia was only slightly greater (10.9%) than in the entire sample (8.3%). The prevalence of anemia was increased to 28% in individuals with two or more abnormal parameters, and to 63% when all three parameters were abnormal. As defined by the presence of at least two abnormal parameters, the prevalence of iron deficiency in various populations separated on the basis of age and sex ranged from 3% in adolescent and adult males to 20% in menstruating women. It is concluded that the accuracy of detecting iron deficiency in population surveys can be substantially improved by employing a battery of laboratory measurements of the iron status.

Adolescent↗
PubMed1975

Food iron absorption. I. Use of semisynthetic diet to study absorption of nonheme iron.

Recent studies have established the validity of employing an extrinsic radioiron tag to measure the absorption of nonheme iron from a complex meal. In the present study, extrinsic tagging was used to measure absorption of nonheme iron from a standard meal chosen as representative of a typical American meal, and from a semisynthetic meal having the same total chemical composition. The latter was designed so that the major dietary components could be systematically altered to determine their separate effects on food iron absorption. Absorption from the standard meal in 32 healthy women averaged 10.0% as compared with a mean absorption of 1.8% from semisynthetic meal. Most but not all of this fivefold difference in absorption could be explained by the enhancing effect of meat in the standard meal. The low availability of iron from the semisynthetic meal will be of particular value in studying factors which enhance food iron absorption, whereas the standard meal is suitable for studying factors which reduce availability of food iron.

Absorption↗
PubMed1975

Ferritin in formed blood elements (38539).

The ferritin concentration of the formed elements of the blood has been measured. Nearly equal amounts were found in plasma, red cells, granulocytes, and in the mononuclear (monocyte and lymphocyte) cell fraction. Platelets contained a negligible amount. Concentrations of ferritin were greatest in blood leukocytes, amounting to approximately 24 mug/ml. Changes occurring with iron depletion and iron overload were consistent with those expected in body tissues in general. With infection, increased levels of ferritin were observed in the mononuclear cell fraction, consistent with that which occurs in RE cells.

Adolescent↗
PubMed1975

Iron nutrition.

Explore the source record for details and available documents.

Diet↗
PubMed1975

Relationship of maternal and infant iron stores as assessed by determination of plasma ferritin.

Using plasma ferritin derminations, iron stores have been evaluated at the end of pregnancy in 26 women and followed sequentially in their healthy, full-term infants. It has been shown that the iron storage status of the mother does not affect the iron status of the infant. Determinations of plasma ferritin in the infants have demonstrated that by 6 months of age the iron status of the infant reflects the adequacy of the dietary intake of iron. In the absence of effective iron supplementation during the first six months, plasma ferritin levels fall to low levels, indicating the depletion of iron stores in the infant.

Adult↗
PubMed1975

Effect of methamphetamine on norepinephrine metabolism in various regions of brain.

The effects of methamphetamine on tritiated and endogenous norepinephrine metabolism was examined in various regions of brain. In acute experiments, 30 minutes or 5 hours after methamphetamine i.p., 3H-norepinephrine was injected into the cisterna magna. In chronic experiments, rats were administered increasing doses of methamphetamine twice a day for 17 days, then 18 hours after the last dose of methamphetamine, 3H-norepinephrine was injected intracisternally. All rats were killed 5 minutes after the intracisternal injection and their brains removed, dissected into five parts and assayed for endogenous norepinephrine, 3H-norepinephrine and its metabolites. In rats treated acutely, methamphetamine caused a significant block in uptake of 3H-norepinephrine and a marked increase in the content of 3H-normetanephrine in all regions except the cortex. Five hours after methamphetamine administration, increased levels of 3H-norepinephrine occurred in the pons-medulla, whereas endogenous norepinephrine content tended to decrease in most regions. In rats treated chronically, enhanced accumulation of 3H-norepinephrine was also confined to the pons-medulla region, whereas endogenous levels of norepinephrine were high in the pons-medulla and low in the hypothalamus and cortex. These data suggest that chronic administration of methamphetamine affects either catecholaminergic nerve cell bodies or nerve terminals in the pons-medulla differentially, as compared to other regions studied.

Animals↗
PubMed1975

The absorption of iron as supplements in infant cereal and infant formulas.

The absorption of iron was measured from isotopically tagged salts used in supplementing infant cereals and as the iron supplement in cow's milk and soy-based formulas. Iron as sodium iron pryophosphate and ferric orthophosphate were poorly absorbed from infant cereal (mean, smaller than 1.0%) and thus are not dependable sources of iron to meet the nutritional needs of infants. Reduced iron of very small particle size and ferrous sulfate when added to cereal was absorbed to a greater extent (mean, 4.0% and 2.7% respectively). For technical reasons, these two forms of iron had not been added to commercial cereal products because of discoloration, distribution problems of the iron in the product, and shortened shelf life. Therefore, at the present time, iron supplementation of infant cereals with sodium iron pyrophosphate, ferric orthophosphate, and reduced iron of large particle size does not provide a predictable and available source of iron to meet the needs of infants. Supplemental iron as ferrous sulfate in milk- and soy-based formulas gave a mean absorption of 3.4% and 5.4%. The iron supplements in these formulas can essentially meet the needs for dietary iron of healthy infants.

Animals↗
PubMed1974

Storage iron kinetics. VII. A biologic model for reticuloendothelial iron transport.

The processing of erythrocyte iron by the reticuloendothelial cell has been characterized by kinetic measurements of blood radioactivity made after the intravenous injection of heat-damaged erythrocytes labeled with (59)Fe and of transferrin-bound (55)Fe. The early reticuloendothelial release of iron, a matter of hours, was calculated from the plasma turnover rate of (55)Fe and the plasma reappearance of (59)Fe. Late release was calculated from the ratio of the cumulative incorporation of both tracers into the circulating red cell mass over a period of 2 wk. There was an initial processing period within the reticuloendothelial cell, after which radioiron either rapidly returned to circulation (t(1/2) 34 min) or was transferred to a slowly exchanging pool of storage iron within the reticuloendothelial cell (t(1/2) release to plasma of 7 days). These pathways were of equal magnitude in the normal dog. Reticuloendothelial release of iron was largely independent of the pre-existing plasma iron level or transferrin saturation. Diurnal fluctuations in the plasma iron level were shown to be the result of a variable partitioning of iron between the early and late release phases. Acute inflammation resulted in a prompt and marked increase in the fraction of iron stored (late phase), whereas depletion of iron stores resulted in a marked increase in early release.

Animals↗