Sequence variations in the Fanconi anaemia gene,FAC: pathogenicity of 1806insA and R548X and recognition of D195V as a polymorphic variant

Fanconi anaemia (FA) is a rare autosomal recessive disorder associated with diverse clinical symptoms, increased chromosomal instability and a marked hypersensitivity to crosslinking agents. At least five complementation groups have been defined, the gene for group C (FAC) being the only FA gene cloned thus far. Several sequence variations have been detected in FA patients, whose assignment to group C, however, had not been ascertained by complementation studies. Using a functional assay, in which we tested the capacity of a variant sequence to correct the defect in FA-C lymphoblasts, we provide evidence for the pathogenic status of 1806insA and R548X and for non-pathogenicity of D195V. Received: 23 April 1996     

A nonlinear dynamic approach reveals a long-term stroke effect on cerebral blood flow regulation at multiple time scales

Cerebral autoregulation (CA) is an important vascular control mechanism responsible for relatively stable cerebral blood flow despite changes of systemic blood pressure (BP). Impaired CA may leave brain tissue unprotected against potentially harmful effects of BP fluctuations. It is generally accepted that CA is less effective or even inactive at frequencies >∼0.1 Hz. Without any physiological foundation, this concept is based on studies that quantified the coupling between BP and cerebral blood flow velocity (BFV) using transfer function analysis. This traditional analysis assumes stationary oscillations with constant amplitude and period, and may be unreliable or even invalid for analysis of nonstationary BP and BFV signals. In this study we propose a novel computational tool for CA assessment that is based on nonlinear dynamic theory without the assumption of stationary signals. Using this method, we studied BP and BFV recordings collected from 39 patients with chronic ischemic infarctions and 40 age-matched non-stroke subjects during baseline resting conditions. The active CA function in non-stroke subjects was associated with an advanced phase in BFV oscillations compared to BP oscillations at frequencies from ∼0.02 to 0.38 Hz. The phase shift was reduced in stroke patients even at > = 6 months after stroke, and the reduction was consistent at all tested frequencies and in both stroke and non-stroke hemispheres. These results provide strong evidence that CA may be active in a much wider frequency region than previously believed and that the altered multiscale CA in different vascular territories following stroke may have important clinical implications for post-stroke recovery. Moreover, the stroke effects on multiscale cerebral blood flow regulation could not be detected by transfer function analysis, suggesting that nonlinear approaches without the assumption of stationarity are more sensitive for the assessment of the coupling of nonstationary physiological signals.