Identification of functionally variant MDR1 alleles among European Americans and African Americans

MDR1 (P-glycoprotein) is an important factor in the disposition of many drugs, and the involved processes often exhibit considerable interindividual variability that may be genetically determined. Single-strand conformational polymorphism analysis and direct sequencing of exonic MDR1 deoxyribonucleic acid from 37 healthy European American and 23 healthy African American subjects identified 10 single nucleotide polymorphisms (SNPs), including 6 nonsynonymous variants, occurring in various allelic combinations. Population frequencies of the 15 identified alleles varied according to racial background. Two synonymous SNPs (C1236T in exon 12 and C3435T in exon 26) and a nonsynonymous SNP (G2677T, Ala893Ser) in exon 21 were found to be linked (MDR1*2 ) and occurred in 62% of European Americans and 13% of African Americans. In vitro expression of MDR1 encoding Ala893 (MDR1*1 ) or a site-directed Ser893 mutation (MDR1*2 ) indicated enhanced efflux of digoxin by cells expressing the MDR1-Ser893 variant. In vivo functional relevance of this SNP was assessed with the known P-glycoprotein drug substrate fexofenadine as a probe of the transporter's activity. In humans, MDR1*1 and MDR1*2 variants were associated with differences in fexofenadine levels, consistent with the in vitro data, with the area under the plasma level-time curve being almost 40% greater in the *1/*1 genotype compared with the *2/*2 and the *1/*2 heterozygotes having an intermediate value, suggesting enhanced in vivo P-glycoprotein activity among subjects with the MDR1*2 allele. Thus allelic variation in MDR1 is more common than previously recognized and involves multiple SNPs whose allelic frequencies vary between populations, and some of these SNPs are associated with altered P-glycoprotein function.

Comparison of Roche MONITOR and Organon Teknika NucliSens assays to quantify human immunodeficiency virus type 1 RNA in cerebrospinal fluid

We compared Roche MONITOR and Organon Teknika NucliSens assays for human immunodeficiency virus type 1 (HIV-1) RNA in cerebrospinal fluid (CSF). Results of 282 assays were highly correlated (r = 0.826), with MONITOR values being 0.29 +/- 0.4 log(10) copies/ml (mean +/- standard deviation) values. Both assays can reliably quantify HIV-1 RNA in CSF.

Evidence of a source of HIV type 1 within the central nervous system by ultraintensive sampling of cerebrospinal fluid and plasma

Defining the source of HIV-1 RNA in cerebrospinal fluid (CSF) will facilitate studies of treatment efficacy in the brain. Four antiretroviral drug-naive adults underwent two 48-hr ultraintensive CSF sampling procedures, once at baseline and again beginning on day 4 after initiating three-drug therapy with stavudine, lamivudine, and nelfinavir. At baseline, constant CSF HIV-1 RNA concentrations were maintained by daily entry of at least 10(4) to 10(6) HIV-1 RNA copies into CSF. Change from baseline to day 5 ranged from -0.38 to -1.18 log(10) HIV-1 RNA copies/ml in CSF, and from -0.80 to -1.33 log(10) HIV-1 RNA copies/ml in plasma, with no correlation between CSF and plasma changes. There was no evidence of genotypic or phenotypic viral resistance in either CSF or plasma. With regard to pharmacokinetics, mean CSF-to-plasma area-under-the-curve (AUC) ratios were 38.9% for stavudine and 15.3% for lamivudine. Nelfinavir and its active M8 metabolite could not be accurately quantified in CSF, although plasma M8 peak level and AUC(0-8hr) correlated with CSF HIV-1 RNA decline. This study supports the utility of ultraintensive CSF sampling for studying HIV-1 pathogenesis and therapy in the CNS, and provides strong evidence that HIV-1 RNA in CSF arises, at least in part, from a source other than plasma.

Prosthetic above-knee femoropopliteal bypass for intermittent claudication

There is no consensus about the most appropriate management of the patient with intermittent claudication due to a superficial femoral artery occlusion. To evaluate the natural history of prosthetic above-knee femoropopliteal (AKFP) bypass, 200 operations for intermittent claudication were reviewed. One hundred AKFP bypasses were done with PTFE and 100 with dacron. In the 30 day postoperative period, four PTFE and three dacron grafts occluded without consequence and only one patient died. Analysis of results by the life-table method demonstrated statistically similar primary graft patency rates at five years (PTFE 65% SE +/- 6.5, dacron 57% +/- 6.2) and ten years (PTFE 31% +/- 18/9, dacron 32% +/- 13.2) (p greater than 0.10). Redo procedures (e.g., thrombectomy, angioplasty) were necessary on 21 grafts (12 PTFE, 9 dacron) and "secondary" patency rates at five years were 76% PTFE and 62% dacron; no grafts which required a redo procedure were patent at ten year follow-up. Major amputations during ten year follow-up were necessary in 16 (8%) patients; all amputations were in diabetic patients. Survival rates were 79% at five and 42% at ten years. An anticipated, the leading cause of death was cardiac related (25 patients); 28 (14%) patients underwent aortocoronary bypass during follow-up. A prosthetic AKFP bypass graft is a safe and durable operation which provides relief from the symptoms of intermittent claudication while allowing for the preservation of the saphenous vein for use later in the coronary or infrapopliteal circulations, should the need arise. These results indicate that the risk of amputation after AKFP is no greater than the natural history of untreated claudication; however, AKFP offers a significant improvement in life-style.