Background— In this prospective follow-up study, the effect of myocardial fibrosis on myocardial performance in symptomatic severe aortic stenosis was investigated, and the impact of fibrosis on clinical outcome after aortic valve replacement (AVR) was estimated. Methods and Results— Fifty-eight consecutive patients with isolated symptomatic severe aortic stenosis underwent extensive baseline characterization before AVR. Standard and tissue Doppler echocardiography and cardiac magnetic resonance imaging (late-enhancement imaging for replacement fibrosis) were performed at baseline and 9 months after AVR. Endomyocardial biopsies were obtained intraoperatively to determine the degree of myocardial fibrosis. Patients were analyzed according to the severity of interstitial fibrosis in cardiac biopsies (severe, n=21; mild, n=15; none, n=22). The extent of histologically determined cardiac fibrosis at baseline correlated closely with New York Heart Association functional class and markers of longitudinal systolic function (all P <0.001) but not global ejection fraction or aortic valve area. Nine months after AVR, the degree of late enhancement remained unchanged, implying that AVR failed to reduce the degree of replacement fibrosis. Patients with no fibrosis experienced a marked improvement in New York Heart Association class from 2.8±0.4 to 1.4±0.5 ( P <0.001). Only parameters of longitudinal systolic function predicted this functional improvement. Four patients with severe fibrosis died during follow-up, but no patient from the other groups died. Conclusions— Myocardial fibrosis is an important morphological substrate of postoperative clinical outcome in patients with severe aortic stenosis and was not reversible after AVR over the 9 months of follow-up examined in this study. Because markers of longitudinal systolic function appear to indicate sensitively both the severity of myocardial fibrosis and the clinical outcome, they may prove valuable for preoperative risk assessment in patients with aortic stenosis.

Background— Enzyme replacement therapy with recombinant α-galactosidase A reduces left ventricular hypertrophy and improves regional myocardial function in patients with Fabry disease during short-term treatment. Whether enzyme replacement therapy is effective in all stages of Fabry cardiomyopathy during long-term follow-up is unknown. Methods and Results— We studied 32 Fabry patients over a period of 3 years regarding disease progression and clinical outcome under enzyme replacement therapy. Regional myocardial fibrosis was assessed by magnetic resonance imaging late-enhancement technique. Echocardiographic myocardial mass was calculated with the Devereux formula, and myocardial function was quantified by ultrasonic strain-rate imaging. In addition, exercise capacity was measured by bicycle stress test. All measurements were repeated at yearly intervals. At baseline, 9 patients demonstrated at least 2 fibrotic left ventricular segments (severe myocardial fibrosis), 11 had 1 left ventricular segment affected (mild fibrosis), and 12 were without fibrosis. In patients without fibrosis, enzyme replacement therapy resulted in a significant reduction in left ventricular mass (238±42 g at baseline, 202±46 g at 3 years; P for trend <0.001), an improvement in myocardial function (systolic radial strain rate, 2.3±0.4 and 2.9±0.6 seconds −1 , respectively; P for trend=0.045), and a higher exercise capacity obtained by bicycle stress exercise (106±14 and 122±26 W, respectively; P for trend=0.014). In contrast, patients with mild or severe fibrosis showed a minor reduction in left ventricular hypertrophy and no improvement in myocardial function or exercise capacity. Conclusions— These data suggest that treatment of Fabry cardiomyopathy with recombinant α-galactosidase A should best be started before myocardial fibrosis has developed to achieve long-term improvement in myocardial morphology and function and exercise capacity.

Xenopus laevis possess a gene repertoire encoding two distinct classes of olfactory receptors: one class related to receptors of fish and one class similar to receptors of mammals. Sequence comparison indicates that the fish-like receptors represent closely related members of only two subfamilies, whereas mammalian-like receptors are more distantly related, most of them representing a different subfamily. The fish-like receptor genes are exclusively expressed in the lateral diverticulum of the frog's nose, specialized for detecting water-soluble odorants, whereas mammalian-like receptors are expressed in sensory neurons of the main diverticulum, responsible for the reception of volatile odors.

Olfactory sensory neurons expressing a given odorant receptor gene project their axons with great precision to a few specific glomeruli in the olfactory bulb. It is not clear to which extent the positions of these glomeruli are fixed. We sought to evaluate the constancy of the glomerular array in the mouse by determining the relative positions of glomeruli for various odorant receptors, using a method that affords single-axon resolution, and in a large number of bulbs. We used a genetic strategy to visualize neuronal populations that express one of three members of the mOR37 subfamily. We generated by gene targeting five strains of mice in which expression of a given mOR37 gene is linked to expression of an axonal maker, which is either taulacZ or tauGFP. The patterns of marker expression faithfully mimic those of the cognate receptors. Axons of neurons expressing a given mOR37 gene converge onto one or two glomeruli per bulb. Each mOR37 gene has its own glomeruli, and the mOR37 glomeruli are grouped within a restricted domain of the bulb. Serial sectioning of 214 bulbs reveals that the relative positions of the three types of glomeruli are not fixed but display local permutations. Importantly, this is also the case among the two bulbs from one individual, ruling out the genetic manipulation itself and differences in genetic background or olfactory experience as causes for the observed variability. These local permutations may reflect the developmental history of the glomeruli and are relevant for the construction of spatial odor maps.Key words: olfaction; olfactory system; olfactory bulb; glomerulus; sensory neuron; olfactory receptor; odorant receptorThe vertebrate olfactory system detects and discriminates numerous chemical compounds. Odorant reception initiates when odorous molecules interact with specific odorant receptors (ORs) on the surface of olfactory sensory neurons (OSNs) (Shepherd, 1994). The OR repertoire is encoded by the largest gene family in the vertebrate genome, comprising as many as 1000 genes in mouse and rat (Buck and Axel, 1991) (for review, see Mombaerts, 1999a,b). Individual OSNs express a few OR genes, perhaps only a single one (Malnic et al., 1999). For most ORs, OSNs expressing a given OR are segregated within one of four zones of the olfactory epithelium in which they are interspersed with OSNs expressing other ORs (Ressler et al., 1993;Vassar et al., 1993;Strotmann et al., 1994). In contrast to their scattered distribution within an epithelial zone, OSNs expressing a given OR project their axons to a few common glomeruli in the olfactory bulb, as was revealed indirectly by in situ hybridization (Ressler et al., 1994;Vassar et al., 1994) and directly by axonal labeling (Mombaerts et al., 1996;Zheng et al., 2000). The latter approach is based on gene targeting in mice and results in ␤-galactosidase staining of the cell bodies, axons, and axon terminals of individual OSNs expressing a given OR. Using a similar genetic strategy, we provided evidence that ORs have instructive roles in ...

The molecular mechanisms mediating the chemoelectrical signal transduction in olfactory receptor cells are still elusive. In this study odor induced formation of second messengers in rat olfactory cilia was monitored in a subsecond time range using a rapid kinetic device. Application of micromolar concentration of citralva induced a rapid, transient elevation of the cyclic adenosine monophosphate level, whereas the concentration of inositol trisphosphate was not affected. In contrast, pyrazine caused a rise in the concentration of inositol trisphosphate, not affecting the level of cyclic adenosine monophosphate. Analysis of the kinetic parameter for the odorant induced reaction indicated that apparently two systems are operating simultaneously.The activating effects of odorants appear to be mediated via different G-proteins. Thus, at least two different second messenger pathways appear to be involved in olfactory signal transduction.