Establishing reference intervals for DPC's free testosterone radioimmunoassay.

OBJECTIVE: To establish reference intervals for serum free testosterone for DPC's Free Testosterone assay. METHODS: We used data from healthy subjects and patients to determine reference intervals by parametric and non-parametric methods after partitioning by sex and age. RESULTS: In males, there was a significant decrease in free testosterone concentrations with age. Reference intervals derived from a combination of 2075 "healthy" and patients' results gave similar values by parametric and nonparametric methods. However, the subgroups failed the test for Gaussian distribution. For each decade from 20 years on and > or = 60 years, the intervals based on 2.5th and 97.5th percentiles were: 24.1-94.8, 25.0-89.3, 23.4-81.7, 22.5-80.4, and 21.5-74.3 pmol/L respectively, in females, there was little change with age. The frequency distribution of 1915 patients was positively skewed, and showed a wider range than "healthy." Using square roots of values gave a Gaussian distribution. The central 95% intervals based on 187 "healthy" subjects were: 0.5-8.1 and 0.0-6.4 pmol/L for 20-59 and > or = 60 years, respectively. CONCLUSION: Developing reference intervals for free testosterone was complicated by the need to partition data by gender and age, difficulty in establishing disease in subjects and presence of physiological and other factors which can affect concentration in health and disease.

Cytokine responses to cardiopulmonary bypass with membrane and bubble oxygenation.

The systemic inflammatory response to cardiopulmonary bypass was assessed in 20 patients who underwent elective coronary artery bypass grafting with flat-sheet membrane oxygenation (group I; n = 10; age, 59 +/- 5 years) or bubble oxygenation (group II; n = 10; age, 62 +/- 8 years). The duration of cardiopulmonary bypass was 46 +/- 12 minutes in group I and 47 +/- 15 minutes in group II. Plasma interleukin-6, plasma interleukin-1 beta, transpulmonary leukocyte counts, pulmonary hemodynamic variables, and respiratory index were determined in all patients perioperatively. The plasma interleukin-6 response (median [range]) was similar in both groups at the end of the operation, peaked 4 hours postoperatively (99 [30 to 320] pg/mL in group I; 123 [21 to 300] pg/mL in group II; p greater than 0.05), and remained elevated 48 hours postoperatively (76 [9 to 140] pg/mL in group I; 65 [25 to 159] pg/mL in group II; p greater than 0.05). No significant interleukin-1 beta response was demonstrated. Pulmonary neutrophil and lymphocyte sequestration was observed on commencement of cardiopulmonary bypass in group II but did not occur in either group on discontinuation of cardiopulmonary bypass. Pulmonary vascular resistance at the end of the operation (82 [48 to 320] dynes.s.cm-5 in group I; 119 [54 to 385] dynes.s.cm-5 in group II; p greater than 0.05) was similar to preoperative values (151 [30 to 327] dynes.s.cm-5 in group I; 185 [62 to 291] dynes.s.cm-5 in group II; p greater than 0.05). The respiratory index at the end of the operation was similarly and significantly increased in both groups (1.26 [0.92 to 4.17] in group I; 1.44 [0.73 to 3.30] in group II).(ABSTRACT TRUNCATED AT 250 WORDS)

Early extubation after coronary artery bypass surgery: effects on oxygen flux and haemodynamic variables.

The effect of extubation within the first postoperative hour was evaluated in 13 patients (mean +/- SD age 59 +/- 6 years) undergoing elective coronary artery bypass surgery without active systemic hypothermia. The mean cardiopulmonary bypass time was 50 +/- 14 minutes. Postoperative improvements in cardiac index and oxygen uptake (from 2.0 +/- 0.4 l/min/m2 and 144 +/- 26 ml/min postinduction to 2.88 +/- 0.76 l/min/m2 and 229 +/- 104 ml/min, p less than 0.01) were maintained following extubation. Lower postoperative systemic and pulmonary vascular resistances (p less than 0.01) did not change to a significant extent following extubation. Despite a two-fold rise in the intrapulmonary shunt (Qs/Qt) following surgery (18.5 +/- 9.7% vs 9.6 +/- 3.2% before surgery) the immediate post-extubation value was similar (18.8 +/- 8.2%) and all patients were discharged from the cardiac recovery area within 16 hours without complication. Extubation within the first postoperative hour is a safe procedure following elective coronary artery surgery with short bypass times where sustained hypothermia less than 32 degrees C is avoided.

Frequency of the delta Phe508 mutation and correlation with XV.2c/KM-19 haplotypes in an American population of cystic fibrosis patients: results of a collaborative study.

The cystic fibrosis (CF) gene has been recently cloned, and a deletion of 3 basepairs (bp) of DNA was found on most of the CF chromosomes. This deletion leads to the synthesis of a protein that lacks a phenylalanine residue at position 508. Using two polymerase chain reaction protocols to study the frequency of this mutation in a series of 192 CF patients, we found the mutation on 72% of affected chromosomes. We then used this value to calculate the predictive value of a negative test result in a population-based screening program for CF carrier status. Haplotype analysis with the polymorphic markers XV.2c and KM-19 on 239 CF chromosomes revealed that 90.7% of CF chromosomes with the deletion had a single haplotype. This haplotype was also associated with 60.4% of CF chromosomes with unknown mutations. These values can be used to calculate the probability of whether an individual from the general population is a carrier of any CF mutation.

A simple assay for the screening of the cystic fibrosis allele in carriers of the Phe508 deletion mutation.

With the recent identification of the cystic fibrosis gene and the elucidation of one of the major mutations responsible for the disease, it is now possible to screen directly for carriers of this particular mutation at the DNA level. The mutation that accounts for approximately 70% of the affected population in North America has been identified as a deletion of a phenylalanine residue at position 508 of the deduced amino acid sequence of the putative protein. We describe herein a method for screening carriers of this mutation which makes use of the polymerase chain reaction and direct viewing of the mutation by staining with ethidium bromide after electrophoresis of the polymerase chain reaction products on a polyacrylamide gel. This quick and sensitive method avoids the need for hybridization assays and the hazard associated with isotopically labeled probes.

Kinetics of protease hydrolysis of extended peptide substrates: measurement by flow-injection analysis.

A flow-injection analysis (FIA) system was developed to study the enzyme-catalyzed hydrolysis of synthetic peptides, each of which contained one scissile bond. The concentrations of alpha-amino groups in reactions mixtures were determined by FIA with o-phthalaldehyde as a fluorescence reagent. The method allows a rapid, precise, and sensitive determination of kinetic constants for proteases acting on extended peptide substrates.

Interaction of trypsin, beta-factor XIIa, and plasma kallikrein with a trypsin inhibitor isolated from barley seeds: a comparison with the corn inhibitor of activated Hageman factor.

A trypsin inhibitor was purified from barley seeds by a modification of published procedures. We determined the dissociation constant, Ki, for the complexes of the barley inhibitor with trypsin, beta-Factor XIIa, and plasma kallikrein. We compared these constants for those of the same enzymes with the corn Hageman Factor inhibitor, which is a homolog of the barley inhibitor. The strength of interaction of the barley inhibitor with the three enzymes was: trypsin greater than beta-Factor XIIa greater than plasma kallikrein. In contrast, the corn inhibitor inhibits beta-Factor XIIa most strongly and does not inhibit plasma kallikrein at all. A possible structural basis for the difference in inhibition specificity is discussed.