[Introduction of the Couder manoeuvre and perineal injuries]. / Introduction de la manœuvre de Couder et évolution des lésions périnéales.

OBJECTIVE: To analyse the introduction of the Couder manoeuvre in our level 3 maternity unit shortly after its introduction in 2019. Then, to evaluate and compare the rate of perineal injuries between 2017, when the manoeuvre was not performed at all, and 2020. MATERIALS AND METHOD: A single-centre retrospective study of patients who delivered a singleton eutociously at term from 1 January to 31 December 2017 and 2020. RESULTS: In total, 2930 records were analysed. The Couder manoeuvre rate was 32.12% in 2020. A change in the distribution of perineal lesions was observed: the rate of intact perineum increased (P<0.001), while 2nd degree lesions decreased between 2017 and 2020 (P<0.05). The 1st degree perineum and obstetric anal sphincter injuries remained stable. The rate of episiotomy decreased significantly by almost a factor of 7. CONCLUSION: The practice of the Couder manoeuvre can be implemented fairly quickly after training of the actors with nearly a third of normal deliveries at term concerned one year after its introduction. This manoeuvre seems, in our practice, to have contributed to the reduction, as previously reported, of the rate of second degree perineal injuries.

Evolution of myosin filament arrangements in vertebrate skeletal muscle.

A survey of skeletal muscles throughout craniates shows basic kinds of myosin filament arrangement, simple-lattice and superlattice, within the A-band of each sarcomere. Distribution of simple- and superlattice arrangements across a phylogeny of craniates suggests that the superlattice arrangement is primitive and that Amia and teleosts are derived in showing simple-lattice arrangements. Two taxa examined (Scyliorhinus and Acipenser) show both lattice types within the same organism implying that there is not a simple evolutionary transformation of one to the other fiber arrangement. We discuss the possible functional significance of the different lattice types. We believe that the crossbridges may have greater competition for actin binding sites in simple-lattice muscles compared to the superlattice types.

Conodont affinity and chordate phylogeny.

Current information on the conodonts Clydagnathus windsorensis (Globensky) and Promissum pulchrum Kovács-Endrödy, together with the latest interpretations of conodont hard tissues, are reviewed and it is concluded that sufficient evidence exists to justify interpretation of the conodonts on a chordate model. A new phylogenetic analysis is undertaken, consisting of 17 chordate taxa and 103 morphological, physiological and biochemical characters; conodonts are included as a primary taxon. Various experiments with character coding, taxon deletion and the use of constraint trees are carried out. We conclude that conodonts are cladistically more derived than either hagfishes or lampreys because they possess a mineralised dermal skeleton and that they are the most plesiomorphic member of the total group Gnathostomata. We discuss the evolution of the nervous and sensory systems and the skeleton in the context of our optimal phylogenetic tree. There appears to be no simple evolution of free to canal-enclosed neuromasts; organised neuromasts within canals appear to have arisen at least three times from free neuromasts or neuromasts arranged within grooves. The mineralised vertebrate skeleton first appeared as odontodes of dentine or dentine plus enamel in the paraconodont/euconodont feeding apparatus. Bone appeared later, co-ordinate with the development of a dermal skeleton, and it appears to have been primitively acellular. Atubular dentine is more primitive than tubular dentine. However, the subsequent distribution of the different types of dentine (e.g. mesodentine, orthodentine), suggests that these tissue types are homoplastic. The topology of relationships and known stratigraphic ranges of taxa in our phylogeny predict the existence of myxinoids and petromyzontids in the Cambrian.