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Biomedical subjects

R L Rettmer

Publications and source records attributed to R L Rettmer.

12 recordsLinked to original sources
PubMed1999

Zinc protoporphyrin/heme ratio for diagnosis of preanemic iron deficiency.

OBJECTIVE: Iron deficiency anemia is known to impair cognitive and psychomotor development. The zinc protoporphyrin/heme (ZPP/H) ratio is a simple, accurate, and sensitive laboratory screening test that detects early iron depletion before the onset of anemia. The objective of this work was to evaluate this test in a primary pediatric practice setting. METHODS: The iron status of a cohort of 361 children was screened during routine examinations at a community pediatric practice. Whole blood hemoglobin concentration, hematocrit ratio, serum transferrin saturation, ferritin concentration, and the ZPP/H ratio were measured. The ZPP/H ratio then was evaluated as a single indicator of iron status by comparing it with other tests for detecting the onset of iron deficiency and for monitoring recovery after iron supplementation. RESULTS: Significant age- and sex-related differences in the ZPP/H ratio were found. In this cohort, serum ferritin concentration and the ZPP/H ratio independently identified the same fraction of iron-deficient patients (3%-4%), and both tests were more specific than was either hemoglobin or hematocrit. A concordance of three iron status parameters changed the prediction of iron deficiency to </=1%. Children <3 years of age and adolescent girls had significantly higher ZPP/H results. CONCLUSION: The prevalence of iron deficiency anemia in the typical healthy American pediatric population is low, but iron deficiency without anemia remains relatively common at some stages of development. Increase in the ZPP/H ratio is demonstrated to be a sensitive, specific, and cost-effective test for identifying preanemic iron deficiency in a community pediatric practice. anemia, nutrition, development.

Adolescent↗
PubMed1992

Laboratory monitoring of nutritional status in burn patients.

Most nutrition laboratory testing relies on serum concentrations of ingested nutrients, their coenzymes, proteins, or lipids. Alternatively, functional tests measure a specific physiological process or biochemical reaction. We compared these two approaches to nutritional assessment in intensive-care burn patients, in whom the serum concentrations of transthyretin (prealbumin), albumin, transferrin, carotene, retinol, ascorbic acid, copper, cholesterol, iron, and calcium were all below established reference ranges. In contrast, serum triglyceride concentrations were often above the reference range. Functional tests for thiamin, riboflavin, pyridoxine, and iron (by zinc protoporphyrin/heme ratio) in these patients all showed normal values. Dietary intake, weight trends, and nitrogen balances all indicated that these patients' estimated caloric and protein needs had been met. These findings suggest that static measurements of serum concentrations may be unreliable indicators of nutritional status in burn patients.

Adolescent↗
PubMed1990

Laser photobioactivation mechanisms: in vitro studies using ascorbic acid uptake and hydroxyproline formation as biochemical markers of irradiation response.

Clinical investigations of laser photobioactivation, or biostimulation, might be differently designed and more fruitful if knowledge of basic biochemical mechanisms were better understood. In this investigation, biochemical events identified as responses to 904 nm irradiation included increased ascorbic acid uptake by fibroblasts. These cells also showed increased hydroxyproline formation, and this was increased several-fold by the addition of proline to the medium. Maximum biochemical responses were observed at a pulse frequency of 67 Hz and a pulse width of 150 nsec with an energy density of approximately 7 mJ/cm2 per exposure. Elements in the mitochondrial cytochrome system are proposed as the radiation absorbing chromophore(s). Hypothetically, the energy generated is linked to ascorbic acid uptake, which in turn stimulates collagen synthesis.

Ascorbic Acid↗
PubMed1990

Chemiluminescent measurement of total urinary nitrogen for accurate calculation of nitrogen balance.

This instrumental method for total urinary nitrogen (TUN) is based on the principle of gas-phase chemiluminescence. Results correlate well with measurements of TUN by the Kjeldahl method, which has long provided the means to calculate nitrogen balances for nutritional management. In recent years, because of speed and convenience of measurement, determination of urinary urea nitrogen (UUN) has been substituted for Kjeldahl TUN. However, in patients requiring aggressive nutritional support, the UUN may not be a valid indicator of total nitrogen excretion. We compared nitrogen balances calculated for patients, using both UUN and chemiluminescence TUN data. For both normal and hospitalized populations, nitrogen balance calculated from UUN data exceeded that calculated from TUN data. We show that use of UUN data in calculating nitrogen balance may result in an incorrect assessment of many patients as being in positive nitrogen balance. TUN determined by chemiluminescence evidently provides a simple means of calculating nitrogen balance more nearly accurately.

False Positive Reactions↗
PubMed1989

Cancer risk in relation to serum copper levels.

A nested, matched case-control study was conducted to assess the relationship between serum levels of copper and the subsequent risk of cancer. One hundred thirty-three cases of cancer were identified during 1974-1984 among 5000 members of a northwest Washington State employee cohort from whom serum specimens had been previously obtained and stored. Two hundred forty-one controls were selected at random from the cohort and were matched to the cases on the basis of age, sex, race, and date of blood draw. Serum copper levels were measured by atomic absorption spectrometry. Risk of a subsequent diagnosis of cancer was positively associated with serum copper levels, but only among those cases diagnosed within 4 years of the time the serum specimens were collected. Among cases diagnosed more than 4 years after specimen collection, there was no consistent association between serum copper levels and risk. Adjustment for age, sex, race, occupational status, cigarette smoking, family history of cancer, alcohol consumption, and, among females, use of exogenous hormones had no appreciable effect on these relationships. The findings suggest that the presence of cancer may increase serum copper levels several years prior to its diagnosis. They are less supportive of the hypothesis that serum copper levels affect cancer risk.

Adult↗
PubMed1988

Ascorbic acid status: biochemical and clinical considerations.

Ascorbic acid (AA) plus dehydroascorbic acid (DHAA) was stable in whole blood in unopened vacutainer tubes. Oxidation of DHAA in plasma was irreversible and rapid at 25 degrees C but not at 4 degrees C. The half-life of AA + DHAA in total parenteral nutrition solutions was greater than 24 h. Conditions are described for dithiothreitol reduction of DHAA followed by assay of total AA, with DHAA being determined by difference. DHAA accounted for less than 5% of the total plasma AA + DHAA in both healthy and diabetic subjects. Infection and postpartum-induced stresses resulted in no significant change in the AA content of polymorphonuclear leukocytes (PMN) per unit of blood but AA content per cell was decreased. When glucose concentration was increased, the Km for AA uptake by PMNs doubled. These chemical and physiological factors combined with the rapid movement of the vitamin between plasma and cells suggest that a reliable indicator of AA status remains to be identified.

Ascorbic Acid↗
PubMed1987

Zinc protoporphyrin. Past, present, and future.

The course of zinc protoporphyrin research has progressed at an increasingly rapid pace on several fronts. A variety of biochemical and clinical evidence viewed in toto now suggests that ferrochelatase catalyzes zinc protoporphyrin formation in states of relative iron-deficient erythropoiesis and in lead-inhibited iron metabolism. Furthermore, a redefinition of the relationship of zinc protoporphyrin to certain other parameters of iron status has been made based upon changes during the earliest states of iron depletion. These clinical studies show that the zinc protoporphyrin level and the ferritin level vary in concert but that changes in the percent transferrin saturation and in the hematocrit results are less consistent. Thus zinc protoporphyrin and ferritin are closely linked metabolically such that iron-deficient erythropoiesis becomes an initial manifestation of iron depletion. The measurement and expression of results as mumoles zinc protoporphyrin/mole heme have improved the quality of results, partly by the elimination of the assumed hematocrit designed into existing instruments. Other refinements in hematofluorometry technology have permitted exploration of the potentially extensive applications of zinc protoporphyrin measurements for lead surveillance and diagnosis, blood banking, pediatrics, obstetrics, sports medicine, and other clinical situations where a very sensitive, cost-effective indication of iron status is required.

Erythrocytes↗
PubMed1987

Interpreting results of coulometry and immunoprecipitation in diagnosing iron disorders.

Concentration of iron in plasma, total iron-binding capacity (TIBC), and transferrin saturation are often determined by standard spectrophotometric methods, but iron concentration may be quantified by immunoprecipitation or, electrochemically, by controlled-potential coulometry. Because these iron assays do not all measure the same form(s) of iron, we studied subjects in various states of iron nutriture: normal adults, iron-deficient patients, thalassemia patients with unsaturated transferrin or oversaturated transferrin, and patients with idiopathic hemochromatosis. The spectrophotometric and coulometric methods detected essentially all non-heme iron in plasma; results correlated well but showed a negative bias toward the coulometric method. Results by an immunoprecipitation procedure, which measures only transferrin-bound iron, correlated well with those obtained coulometrically but were slightly higher than the latter. The characteristics of the various methods for iron must be understood by the clinical laboratory if diagnosis of iron disorders is to be accurate.

Electrochemistry↗
PubMed1987

Plasma iron and transferrin iron-binding capacity evaluated by colorimetric and immunoprecipitation methods.

We evaluated plasma iron (PI) and total iron-binding capacity (TIBC) or transferrin in normal individuals and in patients with iron imbalance. The standard colorimetric measurements of PI and TIBC and the standard isotope-dilution measurement of TIBC were compared with an immunoprecipitation method and also with immunoelectrophoresis of transferrin. PI concentrations as measured by the standard and immunoprecipitation methods agreed closely for all individuals except those with saturated transferrin, where nontransferrin iron increased the results in the standard assay. This excess iron in saturated plasma may be derived from either free iron or iron-bearing ferritin. There were also differences in TIBC between the two methods. Iron-deficient sera gave higher values for transferrin when measured by immunoelectrophoresis. Unsaturated iron-binding capacity was increased in the isotope-dilution method in some iron-saturated plasma, compounding errors when added to erroneously high PI values to compute TIBC. Perhaps some exchange of iron occurred between added iron and transferrin iron in the isotope-dilution method. These measurements confirm the accuracy of the standard colorimetric method of measuring PI and TIBC except in iron-saturated plasma. However, the greater specificity of a polyclonal immunoprecipitation method of measuring PI and TIBC makes it particularly useful in differentiating transferrin-bound iron from nontransferrin iron.

Colorimetry↗
PubMedDate not supplied

Effect of parenteral nutrition and enteral feeding on D-lactic acidosis in a patient with short bowel.

D-Lactic acid can accumulate in blood in some patients with intestinal failure, leading to a clinical syndrome of severe acidosis and encephalopathy. The possible impact of parenteral nutrition on its clinical course has not been established. One patient with a severe short-bowel syndrome supported by long-term parenteral nutrition who suffered repeated episodes of ataxia and disorientation associated with elevated serum levels of D-lactate was studied. Results demonstrated no impact of glucose- vs lipid-based parenteral nutrition formulations on total acid production or serum D-lactic acid levels, increased serum D-lactate levels during administration of neomycin, but prompt resolution of both acidosis and clinical symptoms with discontinuation of oral intake. This study confirms the findings of other investigators that D-lactic acidosis may be a significant, heretofore unappreciated complication in patients with severe short-bowel syndrome, and that prompt resolution may be effected with abrupt discontinuation of oral intake. Furthermore, the present study suggests neither a detrimental nor a beneficial effect of parenteral nutrition on this syndrome.

Acidosis, Lactic↗