After several weeks of cold acclimation, the swimming performance of some fish is increased at low temperatures and decreased at high temperatures. The temperature compensation of locomotory activity involves changes in central patterns of muscle fiber recruitment and in the properties of the peripheral nervous system and muscle tissues. In some freshwater fish belonging to the family Cyprinidae, including the goldfish (Carassius auratus), the common carp (Cyprinus carpio), and the roach (Rutilus rutilus), the intrinsic contractile properties of muscles are modified by thermal acclimation. Parameters that can be altered by temperature acclimation in both fast and slow muscle fibers include isometric twitch contraction time, maximum force production, and unloaded shortening speed. The molecular mechanisms responsible for these changes in contractility are discussed.

Common carp (Cyprinus carpio L.) were acclimated to either 5-8°C or 20-25°C for a minimum of 1 month, and the twitch contraction kinetics of a myotomal nerve-muscle preparation were investigated. A significant compensation for the acute effects of temperature was achieved in twitch kinetics by acclimation to 8°C. An acute drop in temperature from 20 to 8°C in preparations from warm-acclimated fish led to approximately two-to three-fold increases in the half-times for activation and relaxation. At 8"C, values were 50% faster in 8°C-than in 20°C-acclimated fish, indicating a partial capacity adaptation in rates of both twitch activation and relaxation.The mechanisms underlying temperature compensation of twitch contraction kinetics were investigated. A quantitative ultrastructural study was performed on the sarcoplasmic reticulum (S.R.) of fast and slow myotomal muscles. No differences were found in the surface and volume densities of the S.R. in fast-twitch fibres between cold-and warm-acclimated fish. The surface densities of terminal cisternae and S.R. were higher in slow-twitch fibres from the warmacclimated fish. Parvalbumin concentration in fast fibres was found to be independent of acclimation temperature (0.61-0.68 mmolikg wet weight). Although the relative proportions of parvalbumin isoforms (I-IV) showed considerable individual variation this was not correlated with environmental temperature. The Ca" -ATPase activity of S.R.-enriched microsomes prepared from fast myotomal muscle was 60% higher a t 8°C in cold-than warm-acclimated carp. This suggests that changes in the kinetics and/or density of Ca2+ pumps contribute to the observed capacity adaptation in relaxation rate with temperature acclimation. Other possible mechanisms underlying the plasticity of twitch contraction kinetics in carp are briefly discussed.

A unique Pro250Arg point mutation in fibroblast growth factor receptor 3 (FGFR3) was initially reported by Bellus et al. [1996: Nat Genet 14:174-176] and the phenotype subsequently by Muenke et al. [1997: Am J Hum Genet 60:555-564], Reardon et al. [1997: J Med Genet 34:632-636], and Graham et al. [1998: Am J Med Genet 77:322-329]. These authors emphasized the pleiotropic nature of this form of coronal craniosynostosis, including brachydactyly with carpal and/or tarsal coalitions, with other anomalies at lower frequency. We report on a family with autosomal dominant coronal synostosis, segmentation and fusion anomalies of the vertebra and ribs, and Sprengel shoulder due to the Pro250Arg mutation. We also report a single case with an identical phenotype without the mutation.