No abstract

The contraction times of the cat's tongue muscles were measured by recording the fine movements of their surfaces and movements of the tongue's surfaces. The recordings were made by means of a commercial, high-sensitive light reflection transducer (Fairchild FPLA 850) which could be operated without any mechanical loading of the tongue. The contraction times of the intrinsic muscles (including pars longitudinalis superior m. hypoglossi and pars longitudinalis inferior m. styloglossi) measured about 22 ms, while the extrinsic muscles were somewhat slower, around 33 ms. The data are considered in the light of the recently reported histochemical composition of these muscles. The study of the hypoglossal nerve supply to individual tongue muscles revealed that, contrary to earlier reports, the medial nerve sends branches to the intrinsic muscles not only at its distal end but during its entire course through the tongue. The transversal and vertical muscles were found to receive numerous fibers innervating small units of their muscle fibers.

The morphology of the tongue muscles was studied by in situ dissection as well as by histological and histochemical methods. By means of the latter an anatomical reassessment of attachments and fiber courses was made. The histochemistry was studied in sections stained for myofibrillar adenosine triphosphatase (mATPase), succinic dehydrogenase, NADH diaphorase, phosphorylase, esterase, glycogen and lipids. Fibers of type I and type II were identified, and the latter were subdivided into II1 (highly glycolytic), II12 (intermediately glycolytic and lipolytic) and II123 (highly lipolytic). In the extrinsic muscles, the fibers were 19-25% type I (mean diameter 27 micrometers) and 75-81% type II (37 micrometers); the three type II subgroups appeared in equal proportions, each accounting for 22-30% of the total fiber amount. Pars longitudinalis superior m. hyoglossi and pars longitudinalis inferior m. styloglossi contained only type II fibers, mainly type II12 (67% and 46%, respectively), of diameters like those in m. hyoglossus and m. styloglossus. The intrinsic muscles also consisted entirely of type II fibers (23 micrometers). II123 fibers predominated in m. verticalis (83%), which has only 10% H12 and 6% II1, whereas the fiber composition of m. transversus was more balanced: 37% type II1, 32% II12 and 31% II123.

The effect of steady-state moderate hypoglycaemia on human brain homeostasis has been studied with positron emission tomography using [U-11C]-D-glucose as tracer. To rule out any effects of insulin, the plasma insulin concentration was maintained at the same level under normo- and hypoglycaemic conditions. Reduction of blood glucose by 55% increased the glucose clearance through the blood-brain barrier by 50% and reduced brain glucose consumption by 40%. Blood flow was not affected. The results are consistent with facilitated transport of glucose from blood to brain in humans. The maximal transport rate of glucose from blood to brain was found to be 62 +/- 19 (mean +/- SEM) mumol hg-1 min-1, and the half-saturation constant was found to be 4.1 +/- 2.3 mM.

Two patients with complex partial epilepsy and tumour of the temporal lobe scheduled for gamma knife radiosurgery were evaluated pre- and postoperatively by multichannel magnetoencephalography (MEG). Centers of epileptic dipole activity found preoperatively disappeared after the focal irradiation as did the epileptic seizures. Thus, to combine stereotactic MEG and gamma knife radiosurgery seems to be a non-invasive alternative to the conventional neurosurgery in focal epilepsy.