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Articles by D Thomas
Total Records ( 2 ) for D Thomas
  A Quintas Cardama , H Kantarjian , D Jones , J Shan , G Borthakur , D Thomas , S Kornblau , S O'Brien and J. Cortes
 

Patients not in complete cytogenetic response (CCyR) continuously face the competing possibilities of eventually achieving a cytogenetic response versus progressing. We analyzed the probability of achieving a CCyR, major molecular response, and progression in 258 patients with chronic myeloid leukemia in early chronic phase at 3, 6, and 12 months from imatinib start. The initial imatinib dose was 800 mg/day in 208 (81%) and 400 mg/day in 50 (19%) patients. For patients not in CCyR, the probability of achieving CCyR (P = .002) or major molecular response (P = .004) significantly decreased, whereas the risk of progression increased (P = .16) at each time point. Patients with a BCR-ABL1/ABL1 ratio greater than 1% to 10% after 3 months of imatinib had a 92% probability of achieving CCyR with continued therapy, similar to the 98% for those with 1% or less, but their risk of progression (11%) was almost 3-fold that of patients with a BCR-ABL1/ABL1 transcript ratio of 1% or less (4%) and similar to that of patients with transcript levels more than 10% (13%). These results suggest that patients not in CCyR after 12 months on imatinib have a higher risk of progression. This risk is discernible as early as 3 months into imatinib therapy by molecular analysis and may provide the rationale to institute therapies that render higher rates of early response.

  P. A Schweizer , N Duhme , D Thomas , R Becker , J Zehelein , A Draguhn , C Bruehl , H. A Katus and M. Koenen
  Background—

HCN channels activate the pacemaker current If, which is thought to contribute significantly to generation and regulation of heart rhythm. HCN4 represents the dominant isotype in the sinoatrial node and binding of cAMP was suggested to be necessary for autonomic heart rate regulation.

Methods and Results—

In a candidate gene approach, a heterozygous insertion of 13 nucleotides in exon 6 of the HCN4 gene leading to a truncated cyclic nucleotide-binding domain was identified in a 45-year-old woman with sinus bradycardia. Biophysical properties determined by whole-cell patch-clamp recording of HEK293 cells demonstrated that mutant subunits (HCN4-695X) were insensitive to cAMP. Heteromeric channels composed of wild-type and mutant subunits failed to respond to cAMP-like homomeric mutant channels, indicating a dominant-negative suppression of cAMP-induced channel activation by mutant subunits. Pedigree analysis identified 7 additional living carriers showing similar clinical phenotypes, that is, sinus node dysfunction with mean resting heart rate of 45.9±4.6 bpm (n=8) compared with 66.5±9.1 bpm of unaffected relatives (n=6; P<0.01). Clinical evaluation revealed no ischemic or structural heart disease in any family member. Importantly, mutant carriers exhibited normal heart rate variance and full ability to accelerate heart rate under physical activity or pharmacological stimulation. Moreover, mutant carriers displayed distinctive sinus arrhythmias and premature beats linked to adrenergic stress.

Conclusions—

In humans, cAMP responsiveness of If determines basal heart rate but is not critical for maximum heart rate, heart rate variability, or chronotropic competence. Furthermore, cAMP-activated If may stabilize heart rhythm during chronotropic response.

 
 
 
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