A piezomotor using longitudinal actuators.

A new travelling wave type ultrasonic motor has been developed which uses longitudinal piezoelectric actuators to generate a progressive wave on the surface of a metallic ring. The rotor, which moves through frictional force, is pressed on this elastic plate. This paper deals with the motor construction and its characteristics.

Characterization of the mechanical nonlinear behavior of piezoelectric ceramics.

A characterization of the nonlinear behavior with high signal excitation in piezoceramic resonators was carried out. The behavior of power devices working at resonance, in which high strains are involved, is explained. A theoretical model previously described is used to explain the motional impedance variation proportional to the square of the motional current.

New equivalent lumped electrical circuit for piezoelectric transformers.

A new equivalent circuit is proposed for a contour-vibration-mode piezoelectric transformer (PT). It is shown that the usual lumped equivalent circuit derived from the conventional Mason approach is not accurate. The proposed circuit, built on experimental measurements, makes an explicit difference between the elastic energies stored respectively on the primary and secondary parts.

Modal control of beam flexural vibration.

An active control system was developed to control the flexural vibrations of a beam with a modal filtering with only one secondary actuator. Segmented piezoelectric actuators and sensors were used for driving and sensing the bending beam vibrations. The primary actuator was fed by a broadband random disturbance signal in order to excite the first five modes of the structure.

[Primary leiomyosarcoma of the pulmonary artery. Apropos of a case. Review of the literature].

A 59-year-old woman hospitalised because of dyspnea and a heart murmur in a context of pyrexia was found to have evidence of obstruction of the pulmonary arterial system, clearly defined by ultrasonography, catheterisation and angiography and Imatron scan. The particular feature of this fifth reported case of pulmonary artery leiomyosarcoma is its documentation by transesophageal ultrasonography and tumor biopsy during catheterisation. Surgery with partial excision of the tumor was followed by survival for 6 months, bearing in mind the absence of chemo- or radiosensitivity of this type of tumor.

Uptake and binding of serotonin by primary cultures of mouse astrocytes.

Primary cultures of glia contain a high glial fibrillary acidic protein level and exhibit important glutamine synthetase activity. They take up serotonin via a high affinity carrier-mediated system with a Km of micromolar range. The Km of this transport process does not vary during cell growth or maturation; however, during the last period of morphological change induced by dibutyryl cyclic AMP, an increase in Vmax is observed.

Benzodiazepine receptors on primary cultures of mouse astrocytes.

Benzodiazepines bind to glial membranes on a single type of site, with a high affinity (KD = 5 x 10(-9) M) on about 100 fmol of sites per mg protein. The number of binding sites is increased when the membranes are treated with Triton X-100. Antiepileptic drugs such as clonazepam and phenobarbital and hypnotic drugs such as Ro-11-3128 and Ro-11-6896 are able in pharmacological concentrations to displace [3H]flunitrazepam from its glial binding sites.

Effect of prostaglandins and dibutyryl cyclic AMP on the morphology of cells in primary astroglial cultures and on metabolic enzymes of GABA and glutamate metabolism.

Prostaglandins (PGE1) and dibutyryl cyclic AMP (dBc AMP) induce similar morphological changes in astrocytes obtained in primary cultures. PGE1 and dBc AMP increased 2 enzymes of GABA and glutamate metabolism, GABA-T and AAT, but did not modify GDH and GLN-S. Prostaglandins probably affect the cAMP content of glial cells and act in the same way as dBc AMP on glial cell differentiation.

Two forms of GABA transaminase in pig brain: purification and properties.

Two forms of GABA transaminase which could be distinguished by ion-exchange chromatography have been separated and purified in pig brain. The two forms have different Km values for alpha-ketoglutarate and show different degrees of inhibition by various salts. Although the two forms are separable, they have identical antigenic properties, pH optima, and NH2 terminal amino acid composition, and they appear to be of the same molecular size.

Cyclic guanosine monophosphate in primary cultures of glial cells.

Cyclic GMP was found in primary cultures of glial cells obtained by dissociation of newborn mouse brain hemispheres. Its basal level (0.52 pmoles/mg cell protein) was as high as that found in adult mouse brain cortex but 10 times lower than in cerebellum.

In vivo effects of noradrenaline and noradrenergic receptor agonists and antagonists on rat cerebellar cyclic GMP levels.

Cerebellar cyclic GMP levels can be altered by neurotransmitters and their receptor agonists and antagonists. In this study, we investigated the action of noradrenaline and certain drugs affecting alpha- and beta-adrenoceptors on rat cerebellaceptor agonists such as methoxamine and phenylephrine increased cGMP levels. alpha-Adrenoceptor antagonists such as phentolamine, phenoxybenzamine and ARC 239 decreased cGMP levels, whereas yohimbine and piperoxane which are known to act as presynaptic alpha-adrenoceptor antagonists had no effect.

Effect of fenfluramine administration on synaptosomal uptake of some neurotransmitters and on synaptosomal enzymes which metabolise GABA.

Fenfluramine has been considered to deplete neuronal 5-hydroxytryptamine (5-HT). This compound is able to reduce the synaptosomal uptake of 5-HT and other neurotransmitters such as GABA and glutamic acid (Glu). The effects of fenfluramine on these three compounds considered as neurotransmitters are different.

GABA metabolism in cultured glial cells.

GABA-transaminase has been characterized in cultured astrocytes. It is identical to the synaptosomal and perikaryal enzyme in terms of charge, molecular weight, and stability, but it differs in its affinity for GABA, which is much higher in the glial compartment. GABA-transaminase has been shown to be inducible by high GABA concentrations, which suggests that astrocytes have the possibility not only to transport GABA but also to metabolize the amino acid which is taken up.

Effect of L-glutamate and kainate on rat cerebellar cGMP levels in vivo.

L-glutamate and kainate administered intracerebroventricularly (i.c.v.

Purification and properties of 4-aminobutyrate 2-ketoglutarate aminotransferase from pig liver.

4-Aminobutyrate-transaminase (4-aminobutyrate: 2-oxoglutarate amino-transferase, EC 2.6.1.

The effect of electrical stimulation upon the activity of brain glutamate decarboxilase "in vitro".

Using the cytoplasmic soluble fraction from rat brain as a source of glutamate decarboxilase, its enzymatic activity was induced by electrical stimulation and determined by gas release. Modified Warburg's flasks were used for such determination. The limits of frequency and the use of sinusoidal waves were based on normal cerebral rhythms.