PubMed Health⌕ Search

Biomedical subjects

L J Bowie

Publications and source records attributed to L J Bowie.

At least 19 recordsLinked to original sources
PubMed1997

Sequence-based diagnosis of hemoglobinopathies in the clinical laboratory.

Electrophoresis at alkaline and acid pH values is the most widely used method for screening for hemoglobinopathies in the clinical laboratory. Nevertheless, the method does not provide definitive diagnostic information for a number of hemoglobins. New automated DNA sequencing techniques make it possible to definitively identify mutations which cause hemoglobinopathies. Moreover these techniques take about the same time as it takes to perform hemoglobin electrophoresis and globin chain electrophoresis. Although the reagent cost is somewhat higher, the results are definitive.

Base Sequence↗
PubMed1997

Alpha thalassemia and its impact on other clinical conditions.

Mild alpha thalassemia is the most prevalent genetic trait worldwide. We have recently developed a multiplex polymerase chain reaction method to screen for the most common deletions which give rise to alpha thalassemia. The authors have used this method to investigate a potential association of alpha thalassemia with hypertension. Our results show that the prevalence of hypertension in hospitalized blacks who have the -alpha 3.7 deletion is 71 percent higher than the prevalence in hospitalized blacks who do not have the deletion. The authors present a potential mechanism to explain this association.

Chromosomes, Human, Pair 16↗
PubMed1995

Amniotic fluid lamellar body count: a rapid and reliable fetal lung maturity test.

OBJECTIVE: To evaluate the lamellar body count as a predictor of fetal lung maturity. METHODS: We conducted a prospective clinical outcome study. Amniocentesis was performed for evaluation of fetal lung maturity status within 72 hours of delivery in 130 patients. A lamellar body count was performed on each specimen, and a lecithin-sphingomyelin ratio and lung phospholipid profile were performed when possible (insufficient sample or contamination in eight cases). Each infant was evaluated for evidence of respiratory distress syndrome (RDS). RESULTS: A lamellar body count exceeding 30,000/microL predicted pulmonary maturity correctly in all cases (negative predictive value 1.00). All 16 cases of RDS had counts of 30,000/microL or less. If the lamellar body count was less than 10,000/microL, the positive predictive value for RDS was 67%, and the likelihood of a mature result from chromatographic phospholipid analysis was low (one of 14, 7%). Values between 10,000-30,000/microL indicated intermediate risk (four of 39, 10%) for developing RDS. Phospholipid analysis indicated fetal lung maturity in 35 of 39 (90%) cases with lamellar body counts in the intermediate risk range. CONCLUSIONS: The lamellar body count compares favorably with traditional phospholipid testing in the prediction of fetal lung maturity. Phospholipid analysis is not needed with lamellar body counts greater than 30,000/microL or less than 10,000/microL, but may be of benefit for values in the intermediate risk range. Advantages of this test include speed, objectivity, small sample volume required, and universal availability of instrumentation.

Amniocentesis↗
PubMed1994

Detection of alpha-thalassemias by multiplex polymerase chain reaction.

Although alpha-thalassemia is the most common genetic abnormality in the world, there is currently no routine laboratory method to definitively identify individuals who are affected. We describe a rapid and simple method that utilizes deletion-sensitive primers to amplify normal DNA sequences. Deletions involving the regions responsible for most of the alpha-thalassemia cases in the US prevent amplification with these primers. In tests with DNA isolated from small amounts (10 microL) of whole blood, the deletion-sensitive primers gave rise to the expected 248- and 375-bp (base pair) amplification products in normal individuals. These primers, along with primers designed to bind to a nonaffected control sequence from the hemoglobin beta chain, could be amplified simultaneously (multiplex polymerase chain reaction). This made it possible to detect heterozygotes for alpha-thalassemia-2 (one alpha locus deleted) by determining the ratios of the 248- and 375-bp amplification products to the product of the control sequence (268 bp). The method is rapid and simple and can be performed in a routine clinical laboratory.

Base Sequence↗
PubMed1991

Lamellar body number density and the prediction of respiratory distress.

The determination of amniotic fluid lamellar body number density (LBND) has recently been shown to correlate well with other established indicators of fetal lung maturity. The authors have compared the LBND with a fetal lung phospholipid profile in predicting the clinical outcome in 52 well-documented cases. If a cutoff of 30,000/microL was used to indicate fetal lung maturity, there were no false-negative results for the LBND whereas there was one for the fetal lung profile. On the other hand, this cutoff resulted in 22 false-positive results for the LBND, whereas there were only 7 false-positive results by the fetal lung profile. The number of false-positive results by the LBND can be decreased by using a separate cutoff of less than 10,000/microL to indicate high risk for development of respiratory distress, while leaving the cutoff for predicting mature lung at 30,000/microL. This resulted in only four false-positive results for the LBND; each of these were from the same patients who also had false-positive results by the fetal lung profile. Care must be taken to ensure that the particle counter used is properly calibrated and that the appropriate cutoffs for both lung maturity and immaturity are used.

Amniotic Fluid↗
PubMed1986

Degree of unsaturation of the fatty acid chains of phospholipids influences the fluorescence polarization: implications for evaluating fetal lung maturity.

To study the effect of fatty acid chain saturation on the fluorescence polarization assay as a measure of fetal lung maturity, we used purified phospholipids isolated from human amniotic fluid and various commercial phospholipids. We found that the fluorescence polarization value decreased as the concentration of unsaturated fatty acids increased. In contrast, the lecithin/sphingomyelin ratio increases with increasing amounts of saturated lecithin, produced as the fetal lung matures. Since only saturated lecithins are surface active, the two indices of fetal respiratory status must reflect different properties of lung surfactant.

Amniotic Fluid↗
PubMed1986

Effect of streptokinase on fibrinogen and related proteins in plasma.

We investigated the effect of streptokinase on determination of fibrinogen and related clottable proteins in an effort to assess the relative reliability of these determinations in monitoring patients being treated with streptokinase. Citrated plasma was incubated with and without streptokinase, then assayed for fibrinogen (I), fibrin(ogen) degradation products (II), total clottable protein (III), and plasminogen (IV). Values for I decreased rapidly. Values for III and IV generally paralleled those for I, values for III lacked adequate sensitivity. II, low initially, increased to 80 mg/L in 1-2 h. Soybean trypsin inhibitor effectively stabilized all these constituents (except IV) in streptokinase-treated plasma, and we recommend that this (or some other such) inhibitor of fibrinolysis be used routinely when specimens are collected for these determinations. Data are presented that suggest that transient polymers are formed, the clinical significance of which is not known.

Blood Coagulation Tests↗
PubMed1984

Hemoglobin Evanston (alpha 14 Trp----Arg). An unstable alpha-chain variant expressed as alpha-thalassemia.

A new hematologic syndrome with phenotypic features of mild Hb H disease was identified in three children from two unrelated black American families. Erythrocytes from each of these children contained Hb H (beta 4) and Hb Barts (gamma 4), as well as a slowly migrating hemoglobin fraction that made up 7-10% of the total hemoglobin. The parents of the affected children all showed mild thalassemia-like changes, with one of the parents in each family also expressing the variant hemoglobin; in the latter individuals the mutant alpha-chains made up less than 2% of the total, and were present mainly or exclusively in combination with delta-chains in the form of a slowly migrating Hb A2. Purified Hb Evanston showed an increased oxygen affinity, but its Bohr effect, cooperativity, and 2,3-diphosphoglycerate effect were normal. The mutant hemoglobin appeared to have normal stability to heat and to isopropanol, and the stability of its alpha-chain in an extended time course synthesis study also appeared to be similar to that of alpha A. However, the results from short-term globin synthesis studies, and from mRNA translation in vitro, suggest that the two types of alpha-chains were synthesized at relatively equal rates, with a major fraction of the newly synthesized variant alpha-chains undergoing rapid catabolism. The hematologic data taken in combination with DNA hybridization and globin synthesis findings indicate that the proposita in each of these families has the genotype--, alpha A/--, alpha Ev. These observations suggest that two separate mechanisms are contributing to the alpha-thalassemia-like expression of Hb Evanston : the newly synthesized alpha EV-chains are unstable and are subject to early proteolytic destruction; and the mutant alpha-allele is linked to an alpha-globin gene deletion.

Child, Preschool↗
PubMed1983

Proportion of hemoglobin S in blood, as determined from solubility measurements.

We exploited the concentration dependence of hemoglobin S on its solubility in concentrated phosphate buffer to determine the percentage of hemoglobin S or hemoglobin A in whole blood or hemolysates. A sample is incubated for 1 h at 37 degrees C in "SickleQuik" (General Diagnostics) tubes, and the absorbance of the aqueous phase is then measured at 555 nm and 650 nm, the latter wavelength to correct for turbidity. The fractional hemoglobin S or hemoglobin A content is read from standard-curve data on mixtures of hemoglobin A and hemoglobin S. Such curves can be prepared with the use of hemoglobin A alone, because under our conditions all hemoglobin S is precipitated. The curve is reproducible for up to three weeks. Day-to-day CVs ranged from 1.8% at 10% hemoglobin S to 8.1% at 68% hemoglobin S. For similar concentration ranges, day-to-day CVs for electrophoresis, with densitometry, ranged from 4.9% to 18%. Results on 29 patients are presented. We recommend the method for rapid quantification of hemoglobin S percentage for patients with sickle cell disease in acute-care situations.

Adult↗
PubMed1981

Total surface-active phospholipid/sphingomyelin ratio as an index of fetal lung maturity.

As an index of fetal lung maturity, the ratio of total surface-active phospholipid (phosphatidylethanolamine + phosphatidylinositol + phosphatidyglycerol + lecithin) to sphingomyelin performs as well as or better than any other indicator that we tested, showing 92% sensitivity and 98% specificity. The sensitivity and specificity, respectively, of the other methods were: (a) lecithin/sphingomyelin ratio, 92% and 95%; (b) alkaline phosphatase/glutamyltransferase ratio, 100% and 49%; (c) microviscosity, 75% and 97%; and (d) adsorbance at 650 nm, 50% and 73%. The procedure requires 2 h or less and its simplicity allows it to be offered on a 24 h/day basis without necessitating special training.

Amniotic Fluid↗
PubMed1980

Sickle-cell hemoglobin: fall in osmotic pressure upon deoxygenation.

Macromolecules such as hemoglobin exert both kinetic and matrix effects on osmotic pressure. The kinetic osmotic pressure of sickle-cell hemoglobin is lost upon deoxygenation at physiological erythrocyte concentrations. The non-kinetic or matrix component of osmotic pressure remains relatively unchanged. Loss of thermal-osmotic activity during deoxygenation occurs throughout a hemoglobin concentration range between 2.5 and 35 g/100 ml. Deoxygenation of sickle-cell hemoglobin causes aggregation such that the matrix effect is unchanged but the kinetic (van't Hoff) effect nearly vanishes. A loss of intracellular osmotic pressure during deoxygenation could dehydrate the erythrocyte sufficiently to promote more rapid sickle-cell hemoglobin aggregation. Subsequently, complete gelation of these aggregates could cause additional water loss and thrust the sickled cell into an irreversible cycle. The osmotic pressure of normal hemoglobin does not change appreciably during deoxygenation and is essentially the same as the osmotic pressure of oxygenated sickle-cell hemoglobin.

Erythrocytes, Abnormal↗
PubMed1979

An examination of the role of vitamin E in glucose-6-phosphate dehydrogenase deficiency.

The effect of vitamin E on erythrocyte glutathione stability was studied both in vitro and in vivo on subjects with glucose-6-phosphate dehydrogenase deficiency. The results suggest that lipid membrane peroxidation in glucose-6-phosphate dehydrogenase deficient erythrocytes, which has been postulated to occur under conditions of oxidative stress, does not result in significant depletion of erythrocyte reduced glutathione pools. Vitamin E supplementation in these individuals was shown to have little or no effect on the response of their erythrocytes to oxidative stress.

Erythrocytes↗