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Biomedical subjects

G L Lankford

Publications and source records attributed to G L Lankford.

15 recordsLinked to original sources
PubMed2001

Hematocrit correlates well with circulating red blood cell volume in very low birth weight infants.

Although circulating red blood cell (RBC) volume is a better measure of total body oxygen delivering capacity than hematocrit (HCT), circulating RBC volume is more difficult to measure. Thus, the HCT is often used in RBC transfusion decisions. However, several previous studies of low birth weight infants have reported that the correlation between HCT and circulating RBC volume is poor. Using a robust nonradioactive method based on in vivo dilution of biotinylated RBC enumerated by flow cytometry, the present study reexamined the correlation between HCT and circulating RBC volume in very low birth weight infants. Venous and capillary HCT levels were compared with circulating RBC volume measured using the biotin method. Twenty-six stable very low birth weight infants with birth weights less than 1300 g were studied on 43 occasions between 7 and 79 d of life. Venous HCT values correlated highly with circulating RBC volume (r = 0.907; p < 0.0001). However, the mean 95% confidence limits for prediction of circulating RBC volume from venous HCT (the average error of prediction) was +/-13.4 mL/kg. The correlation between HCT and circulating RBC volume is strong in older stable very low birth weight infants. However, clinically important uncertainty exists in estimating circulating RBC volume and the associated RBC transfusion needs of an individual infant based on venous HCT. Because direct measurement of circulating RBC volume is not yet practical, the HCT (or the blood Hb concentration) remains the best available indirect indicator.

Erythrocyte Transfusion↗
PubMed1999

Measurement of circulating red cell volume using biotin-labeled red cells: validation against 51Cr-labeled red cells.

BACKGROUND: Anemia is a serious problem in the fetus and preterm infant. To investigate the physiology and pathophysiology of anemia and to assess responses to blood transfusions or erythropoietin therapy, measurement of circulating red cell volume would be useful. Because the standard 51Cr method exposes the subject to radiation, a method of measuring circulating red cell volume without radiation exposure, sufficiently sensitive for use in fetuses and infants, was developed. STUDY DESIGN AND METHODS: In 10 healthy adults whose body mass ranged from 56.8 to 115.9 kg, aliquots of autologous red cells were labeled with biotin or with 51Cr, mixed, and transfused intravenously. Circulating red cell volume was measured in posttransfusion blood by quantitating the in vivo dilution of biotinylated red cells. Biotinylated red cells were detected by two methods: 1) 125I-streptavidin and 2) fluorescein-labeled avidin with flow cytometry. RESULTS: Circulating red cell volume measured by 125I-streptavidin detection agreed well with that measured by 51Cr (slope = 1.07, y-intercept = -97, correlation = 0.987). Similarly, circulating red cell volume measured by flow cytometry agreed well with that measured by 51Cr (slope = 1.05, y-intercept = -20, correlation = 0.987). CONCLUSIONS: Circulating red cell volume measured by the use of biotin with either 125I-streptavidin or flow cytometry agrees with that measured by 51Cr. Each system provides a method of performing these studies without exposing the subject to radiation.

Adult↗
PubMed1999

Measurement of red cell survival using biotin-labeled red cells: validation against 51Cr-labeled red cells.

BACKGROUND: Anemia is a serious problem in the fetus and preterm infant.To investigate the physiology and pathophysiology of anemia and to assess responses to blood transfusions and erythropoietin therapy, measurement of circulating red cell survival would be useful. STUDY DESIGN AND METHODS: Because the standard 51Cr method exposes the patient or subject to radiation, a practical, accurate method for measuring red cell survival was developed on the basis of determining the number of biotin-labeled red cells that persist in the circulation by using fluorescein-labeled avidin and flow cytometry. In addition, disappearance of total biotin label was measured by using 125I-streptavidin. Results of each detection method were compared to red cell survival measured by the standard 51Cr method. RESULTS: Biotinylated cells persisted in circulation with life spans approaching normal. Despite near-normal persistence in circulation of the biotin-labeled cells, about one-half of the biotin label left the circulation over the first few weeks, causing early curvilinear disappearance. This observation is consistent with the hypothesis that about one-half of the biotin label leaves the red cells. However, about one-half of the biotin was permanently attached, which produced linear disappearance and approximately normal life span estimates for the linear survival curve appearing after the first few weeks. CONCLUSION: Red cell survival can be measured accurately in humans using enumeration of biotinylated red cells. The method is practical and does not expose the patient to radiation.

Adult↗
PubMed1997

[14C]cyanate labeling of sheep red cells: covalent binding to hemoglobin continues in vivo for a day.

The sheep is a useful model to study fetal and newborn physiology including perinatal erythropoiesis and red cell kinetics. A practical, economical method for measuring red cell survival (RCS) in sheep would be very valuable. However, 51Cr is unsatisfactory, and suitable alternatives have not been published. In the course of investigating [14C]cyanate as a label for sheep red cells, we observed continued covalent labeling over 24 h in vivo that was great enough to introduce a substantial artifact into two commonly used parameters of RCS: posttransfusion recovery (PTR24) and time to 50% decrease (T50) when referenced to time zero. In a simulation of in vivo conditions, the amount of 14C bound to Hb increased 26 +/- 6% (mean +/- 1 SD, n = 11) over 24 h. To investigate the mechanism of the increasing 14C bound, acid-acetone extraction, molecular sieve chromatography, and density gradient separation were used separately or in combination to quantitate intracellular free 14C and 14C covalently bound to intracellular proteins. Free 14C decreased as protein-bound [14C]cyanate increased. These studies provide evidence that covalent binding of [14C]cyanate to intracellular Hb continues in vivo for the first 24 h and that the source of the increase is intracellular free [14C]cyanate. We conclude that 1) PTR24 cannot be accurately determined by [14C]cyanate unless labeled red cells are incubated before infusion to allow the cyanate reaction to approach completion and 2) RCS by [14C]cyanate should be referenced to blood concentrations at 24 h.

Acetone↗
PubMed1997

Circulating red cell volume and red cell survival can be accurately determined in sheep using the [14C]cyanate label.

The sheep commonly serves as an animal model for investigation of human fetal and newborn erythropoiesis and red blood cell kinetics. Measurement of red cell volume (RCV) and survival (RCS) in sheep would be useful for studying mechanisms of neonatal anemia. Unfortunately 51Cr, the standard method for RCV, is not suitable for RCS in sheep because 51Cr leaves the red cell too rapidly. We developed and validated the permanent label [14C]cyanate as a method for measuring both RCV and RCS in sheep. In 19 sheep, RCV was determined simultaneously using [14C]cyanate and 51Cr. RCV determined by [14C]cyanate agreed almost perfectly with RCV by 51Cr; correlation coefficient = 0.990. The line of regression had a slope of 0.94 and an intercept of 40; these parameters are not significantly different from a line of identity. In nine sheep, RCS was determined using [14C]cyanate. Survival after d 1 accurately fit a model containing two components: 1) an early exponential loss likely related to damage caused by labeling and handling and 2) a linear decrease that reflected normal survival of undamaged red cells. Mean potential life span (MPL) determined from the linear phase was 114 +/- 12 d (mean +/- 1 SD). These results agree with reported MPL values determined either by 59Fe or differential hemolysis. Together, these observations establish [14C]cyanate-labeled red cells as a tool for measuring both RCV and RCS in sheep and enhance the value of the ovine model for investigating neonatal anemia.

Anemia↗
PubMed1995

Biotin accounts for only half of the total avidin-binding substances in human serum.

In studies using an avidin-binding assay to measure the serum or plasma concentration of biotin, biotin is sometimes assumed to be equal to the avidin-binding substances detected. To provide a range of values for serum concentrations of biotin, bisnorbiotin, and biotin sulfoxide, HPLC was used to separate avidin-binding substances in human serum, and the chromatographic fractions were assayed for avidin-binding substances (biotin and biotin metabolites). In sera from 15 normal fasting adults, substantial concentrations of avidin-binding substances other than biotin were detected. Two of the principal substances were identified as bisnorbiotin and biotin sulfoxide based on their chromatographic properties. The serum concentrations of bisnorbiotin and biotin sulfoxide varied widely among the individuals. In three subjects, the concentration of bisnorbiotin exceeded that of biotin. The presence of avidin-binding substances in addition to biotin may have confounded previous measurements of the concentration of biotin in serum, plasma, and blood when avidin-binding assays were used. Because bioassay methods for biotin sometimes use organisms for which one or more of these biotin metabolites are growth factors, measurements of biotin in blood using some bioassays are likely to overestimate the concentrations of biotin.

Adult↗
PubMed1993

Biotin and biotin analogs in human urine: biotin accounts for only half of the total.

In studies using avidin-binding assays to measure the urinary excretion of biotin, biotin is sometimes assumed to be equal to the detectable avidin-binding substances present. High performance liquid chromatography was used to separate avidin-binding substances in human urine, and the chromatographic fractions were assayed for avidin-binding substances (biotin and biotin analogs) by a sensitive, specific assay based on binding of biotin to [125I]avidin. In a study of ten normal adults, substantial amounts of avidin-binding substances other than biotin were detected, two of which were bisnorbiotin and biotin sulfoxide. These biotin analogs were initially identified by their chromatographic properties, and identities were confirmed by chemical conversion. The presence of avidin-binding substances in addition to biotin may have confounded previous measurements of the urinary excretion of biotin using avidin-binding assays. Because bioassay methods for biotin often use organisms for which one or more of these biotin analogs are growth factors, measurements of biotin in urine using some bioassay methods are likely to overestimate the concentrations of biotin.

Avidin↗
PubMed1989

Quantification of urinary 3-hydroxyisovaleric acid using deuterated 3-hydroxyisovaleric acid as internal standard.

Deficiency of biotin at the tissue level can be assessed indirectly by measuring the urinary excretion of 3-hydroxyisovaleric acid. This paper describes the application of an improved method of quantifying urinary 3-hydroxyisovaleric acid using unlabeled and uniformly deuterated 3-hydroxyisovaleric acid. These compounds were synthesized by a modification of the lithioacetic acid method for generation of beta-hydroxy acids. Elemental analysis, nuclear magnetic resonance, gas chromatographic and gas chromatographic/mass spectrometric data demonstrated that the compounds are greater than 95% pure. Mass spectrometry confirmed the identity of the unlabeled compound, demonstrated that the deuterated compound is uniformly labeled, and offered insight into the pattern of mass fragmentation. The method for determination of the concentration of 3-hydroxyisovaleric acid in rat urine uses gas chromatographic/mass spectrometric quantification of the di-trimethylsilyl derivative with the deuterated compound as the internal standard. Results provide evidence that this method is more accurate than a previously published method that did not utilize the unlabeled and deuterated standards.

Animals↗
PubMed1984

Rat intestinal vitamin D-dependent calcium-binding protein: immunocytochemical localization in incisor ameloblasts.

Antiserum raised against the 10,000-Dalton vitamin D-dependent calcium-binding protein (CaBP10) from rat intestine was used to localize CaBP10 immunocytochemically in histological sections of rat mandible using an indirect immunoperoxidase method. Ameloblasts in the zone of maturation, along the continuously erupting incisor, contained CaBP10 throughout their cytoplasm. It was present in both smooth-ended ameloblasts and ruffle-ended ameloblasts. CaBP10 was not found in earlier developmental stages of ameloblasts or in other cells involved in tooth formation, i.e., odontoblasts, pulpal cells, cells of the stellate reticulum, papillary layer, and outer dental epithelium. The presence of CaBP10 in ameloblasts suggests that the vitamin D-endocrine system may have a direct effect on tooth formation in addition to the indirect effect of maintaining the required levels of serum calcium and phosphorus required for mineralization.

Ameloblasts↗
PubMed1984

Immunocytochemical localization of rat intestinal vitamin D-dependent calcium-binding protein.

Vitamin D-dependent calcium-binding protein (CaBP) was localized in intestinal tissue sections obtained from rats raised under three different nutritional conditions: a normal vitamin D-replete diet, a vitamin D-free diet followed by supplementation with vitamin D3, or a vitamin D-free diet without additional supplementation. An indirect immunoperoxidase technique, with immunocontrols, was used to visualize the specific sites of CaBP. CaBP was visualized only in the cytoplasm of absorptive cells. In the duodenum of animals raised on a normal diet, CaBP was present in absorptive cells from the upper crypt region to the villus tips. In the jejunum, many fewer absorptive cells contained CaBP, while in the ileum only random absorptive cells near the villus tips contained CaBP. In rats raised on a vitamin D-deficient diet then supplemented with vitamin D3, CaBP was present in cells at the full depth of the crypts and in absorptive cells along the total villus length in the duodenum. Rats raised on the same deficient diet but without supplementation with additional vitamin D exhibited no CaBP in crypt cells nor in absorptive cells more than half way up the villi. Absorptive cells higher on the villi contained immunoreactive CaBP but the intensity of immunostaining and number of CaBP-containing cells was markedly reduced compared to the vitamin D-supplemented group.

Animals↗
PubMed1982

Intestinal calcium-binding protein in the baboon (Papio cynocephalus).

1. Calcium-binding protein (CaBP) has been isolated from baboon (Papio cynocephalus) intestinal mucosa by gel filtration and ion-exchange chromatography. 2. Similarity in electrophoretic behavior, size and charge and immunologic structure are demonstrated between the baboon CaBP and CaBPs isolated from other species. 3. Baboon intestinal CaBP is resistant to neuraminidase digestion.

Animals↗
PubMed1982

Experimental protein malnutrition decreases calcium-binding protein in rat intestinal mucosa.

Calcium-binding activity was measured in duodenal mucosal homogenates of rats 50 days after weaning onto a protein-deficient diet providing 3-4 g of protein per kilogram of body weight per day compared to control animals, who were fed an isocaloric diet providing 9-12 g of protein per kilogram of body weight per day. Calcium-binding activity was decreased (44% of control) further than can be explained by the decrease in intestinal mucosal weight (70% of control) or supernatant protein content (80% of control). The results suggest that the decrease in calcium-binding activity reflects decreased synthesis of the vitamin D-dependent calcium-binding protein (CaBP) as an adaptive response to the stunted growth associated with protein malnutrition.

Animals↗