PubMed Health⌕ Search

Biomedical subjects

B L Therrell

Publications and source records attributed to B L Therrell.

9 recordsLinked to original sources
PubMed1992

Genotypic confirmation from the original dried blood specimens in a neonatal hemoglobinopathy screening program.

Dried blood spots are used for newborn screening because of ease of sample collection, handling, and shipment. DNA is stable and accessible in the filter paper matrix. Genotypic confirmation using initial specimens is demonstrated for a regional screening program. Seventy-five blinded samples underwent DNA analysis after Hb electrophoresis. DNA was microextracted from a 1/2-inch semicircle (25 microL whole blood equivalent), amplified, and analyzed by four different methods. Direct amplification without microextraction and automated sequencing from microextracted DNA also was performed. All four analyses agreed for the A and S alleles in 70 of 75 specimens. Three disagreements were clarified by the other semicircle from the original sample: two were due to polymerase chain reaction contamination and one to contamination of one of four analytical tests. Two would have required analysis of a second specimen, one because of polymerase chain reaction failure and the second because the patient had S/beta-thalassemia. Direct amplification without microextraction was successful in an additional 77 of 78 specimens for analysis of the A, S, C, and E alleles. Automated direct sequencing from microextracted DNA was demonstrated for the A, S, and C alleles. Analysis of microextracted DNA from dried blood specimens for A and S alleles reduced the need for and costs of obtaining a second specimen for confirmation by 97%. Direct amplification without microextraction for analysis of A, S, and C alleles permits additional reduction in personnel time and costs. We have demonstrated that microextracted DNA is amenable to automated sequencing after asymmetric polymerase chain reaction. Direct genotypic confirmation can facilitate diagnosis and initiation of medical intervention.

Alleles↗
PubMed1978

Analysis for lead in undiluted whole blood by tantalum ribbon atomic absorption spectrophotometry.

We describe a modified tantalum ribbon atomic absorption procedure for determining lead in undiluted whole blood. An instrumentation Laboratory (I.L.) Model 151 atomic absorption spectrophotometer equipped with an I.L. Model 355 Flameless Sampler was used. The Flameless Sampler was slightly modified to include three-cycle operation instead of the normal two cycles. This modified single-beam system, equipped with background correction, allows 5-microliter specimens of whole blood to be quickly and accurately analyzed. No sample preparation other than vortex mixing is involved and method reliability has been demonstrated during an extended period of successful participation in proficiency testing studies conducted by the Center for Disease Control. This tantalum ribbon methodology has further been demonstrated to be effective both as a primary screening procedure and as a confirmatory procedure, when coupled with erythrocyte protoporphyrin determinations, in screening over 300 000 clients during a three-year period of use in the Early and Periodic Screening, Diagnosis and Treatment (EPSDT) Program in Texas.

Humans↗
PubMed1977

Syphla-Chek: a qualitative study.

A qualitative evaluation of the newly marketed Syphla-Chek Test (Hyland, Div. of Travenol Laboratories, Inc., Costa Mesa, Calif.), a macroscopically read, nontreponemal card test, was undertaken in order to further evaluate the validity of this procedure as an aid in the diagnosis of syphilis. A total of 1,074 randomly selected sera submitted to the Texas Department of Health Resources for routine analysis, for confirmational analysis, and as a result of problems in analysis, were examined using the Venereal Disease Research Laboratory (VDRL) slide test, the Rapid Plasma Reagin (circle) Card Test (RPRCT), Syphla-Chek Test, and the fluorescent treponemal antibody absorption (FTA-ABS) test. Comparison of the reagin testing procedures studied versus the FTA-ABS procedure led to the following order of agreement with FTA-ABS reactive results: Syphla-Chek, 88.8%; RPRCT, 87.1%; and VDRL, 83.2%. Agreement with FTA-ABS nonreactive results was in order: RPRCT, 86.7%; Syphla-Chek, 79.6%; and VDRL, 78.7%. The relatively few minor procedural problems encountered with the Syphla-Chek Test during this study are also discussed.

Antibodies↗
PubMed1977

Hemoglobin Lufkin: beta 29 (B11) Gly replaced by Asp. An unstable hemoglobin variant involving an internal amino acid residue.

Hemoglobin Lufkin was found in a Black-American family. Structural analysis of the abnormal hemoglobin indicates a substitution of aspartic acid for glycine at position 29 in the beta chain. Marked instability of the variant hemoglobin is demonstrated by the rapid formation of inclusion bodies upon exposure of the red cells to redox dyes and by the large percentage of precipitated hemoglobin at 65 degrees C. The oxygen affinity, the Bohr effect, and the degree of cooperativity of Hb Lufkin and Hb A are similar over the physiologic pH range. However, at acid pH the oxygen affinity of the variant is increased. Unlike several other reported variants in the B helix, Hb Lufkin is not associated with methemoglobinemia.

Amino Acids↗
PubMed1976

Hemoglobin Fannin-Lubbock [alpha2 beta 2 119 (GH2) Gly replaced by Asp]. A new hemoglobin variant at the alpha1 beta 1 contact.

Hemoglobin Fannin-Lubbock was found in a 9-year-old Mexican-American female. The abnormal hemoglobin was detected as a fast-moving variant by electrophoresis on cellulose acetate at pH 8.4. Structural analysis indicated a substitution in the beta-chain of aspartic acid for glycine at position 119, a position involved in the alpha1beta1 contact of the hemoglobin tetramer. This contact between unlike chains is larger and undergoes a smaller shift during the process of oxygenation and deoxygenation that the alpha1beta2 contact (Perutz, M.F., Muirhead, H., Cox, J.M. and Goaman, L.C.G. (1968) Nature 219, 131-139). Mutations in this contact tend to cause slight or no changes in functional behavior. Apart from a mild anemia, the propositus did not exhibit any obvious clinical symptoms.

Amino Acids↗
PubMed1976

Qualitative evaluation of the reagin screen test.

After a preliminary study of 557 sera used as a procedural training exercise, the Reagin screen test (RST) for the macroscopic detection of reagin (as an aid to detecting syphilis) was qualitatively compared to the rapid plasma Reagin (RPR) (circle) card test and Veneral Disease Research Laboratory (VDRL) slide test on 435 random portions of sera using fluorescent treponemal antibody adsorption (FTA-ABS) results as a comparative base. A comparison of total agreement (positive and negative) with the FTA-ABS results led to the following order. RPRCT (I5.5%), VDRL (79.8%), and RST (74.5%). Of the total samples shown to be reactive by the FTA-ABS procedure, the percentage of these interpreted as nonreactive (i.e., "false negative") by the procedures compared was considerably higher with the RST procedure (29.3%) than with either the RPRCT (10.9%) or the VDRL (7.1%) procedures. Minor problems encountered with procedural techniques are also mentioned.

Antibodies↗