Experiments with developing euthyroid, hypothyroid and hyperthyroid rats show that the transition from neonatal to adult fast myosin is orchestrated by thyroid hormones acting directly upon fast muscle cells. Denervation studies reveal the switch from neonatal to adult fast myosin synthesis is independent of the motoneuron. However the synthesis of slow myosin during development is critically dependent on innervation. MyosinIsozyme Transition

Extensor digitorum longus muscles of male adult White New Zealand rabbits were indirectly stimulated at 10 Hz for 12 h daily for periods ranging up to 28 days. After four weeks the stimulated muscles showed a nearly uniform profile of high succinate dehydrogenase activity and, when incubated after acid preincubation for myofibrillar adenosine triphosphatase, displayed more dark- and intermediate-staining fibers than their contralateral counterparts. Muscles stimulated from between 6 to 21 days revealed degenerative foci and phagocytosis of degenerated fibers. These fibers were mostly of the fast-twitch, glycolytic type. Small myofibers, which often contained central nuclei, and structures identified as myoblasts or myotubes, reacted with a monoclonal antibody prepared against embryonic myosin heavy chains. The data suggest that under the employed conditions the fast to slow conversion of chronically stimulated fast-twitch rabbit muscle is not exclusively caused by adult fiber transformation, but results in part from the substitution of fast-twitch glycolytic fibers with newly formed fibers that have a high oxidative profile.

The results of the multicenter evaluation show that the Micral-Test II test strip permits an immediate and reliable semiquantitative determination of low albumin concentrations in urine samples with an almost user-independent color interpretation.

Stereoisomerization of Ketene lminesBarriers to racemization in solution of the ketene imines 1 a -y and X-ray structures of the ketene imines 1 s and z are described. Similar to allenes all ketene imines have dihedral angles of 90" between the C-and N-substituents. The barriers to racemization range from 30 to 63 kJmol-' and are lowered by electron attracting substituents on C and N. The barriers of m-and p-substituted N-arylketene imines give a linear Hamme// correlation with 0 -constants. N-Arylketene imines racemize through inversion at nitrogen and simultaneous rotation of the aryl group around the N -aryl bond.Ketenimine 1 sollten wie Allene gebaut sein, bei denen ein Substituent durch ein freies Elektronenpaar ersetzt ist. Am C-Ende ungleich substituierte Ketenimine (1, R' # R2) waren also chiral.Die Frage nach dem raumlichen Bau von Keteniminen ist nicht trivial, denn die isoelektronischen Cyanamidiumsalze 2 haben beispielsweise ein lineares Molekiilgerust N -C = N -C mit C2,.-Symmetrie, sind also auch fur R' # R2 achiral'). Nach einer Rontgenstrukturanalyse2) ist weiterhin das C = C = N -C-Gerust des Ketenimins 3 linear gebaut und weist eine kurze Kumulen-CN-Bindung von nur 115 pm auf, wie sie typisch fur Nitriliumsalze ist 3). Ahnlich sind einige andere Ketenimine g e b a~t~.~) .Erst neuerdings wurden Kristallstrukturen von Keteniminen mit allenartigem Molekulgeriist 1 mit CiSymmetrie und einer Lange der C = N-Doppelbindung von 122 pm bekannt6).Nach diesen Befunden mu8 man vermuten, daR der Energieunterschied zwischen der gewinkelten Form 1 und der linearen Anordnung 3 nicht gro8 ist, da8 Ketenimine mit R' # R2 also ahnlich wie Carbodiimide') in Losung bereits bei tiefen Temperaturen Chem. Ber. 114(1981) +

A multiccntcr evaluation including nine Sports medicine Institutes was performed to assess the performance and suitability of the Accusport® System. The imprecision study vvith aqueous lactate Solutions gave mean coefficients of Variation of 3.4% (in-series) and 4.8% (day-to-day), respectively. The accuracy was determined by comparison of the Accusport® System with Test Combination Lactate for Sports Medicine (TCL): capillary blood (TCL) vs. capillary blood (Ac-cusport® BL mode) and capillary plasma (TCL) vs. capillary blood (Accusport® PL mode). The regression analysis according to Passing-Bablok gave slopes of 0.994 and 0.949, respectively, and intercepts of significant but negligible size. The hematocrit of the sample had no influence on the measurement result in the ränge tested (35-55%). Bilirubin (up to 0.204 mmol/1), cholesterol (up to 9.05 mmol/1), triglycerides (up to 5.72 mmol/1), and hemolytic samples (hemoglobin up to 0.36 mmol/1) did not cause measurable interference. The sample volume had no effect on the measurement between 15 and 50 . No interference was found with the 16 drugs tested. Accusport® proved to be a reliable and exact System for determination of the lactate concentration in capillary blood samples. Since it is battery-powered and portable, it can be used in the field and thus allows immediate on-site control of training.