[Prospective evaluation of fracture risk in osteoporotic patients after low cement volume vertebroplasty]. / Suivi prospectif du risque fracturaire après vertébroplastie utilisant un faible volume de ciment chez des patients ostéoporotiques.

PURPOSE: To prospectively compare the incidence of new fractures (as demonstrated on MR) within the first 3 months after an initial fracture in a population treated with low cement volume vertebroplasty and a population treated conservatively. MATERIALS AND METHODS: From 49 patients admitted for osteoporotic vertebral compression fracture, 22 underwent CT guided vertebroplasty with injection of 1-3 ml of PMMA, and 27 were treated conservatively. All patients underwent MR at presentation and at 3 months to detect new compression fractures. RESULTS: Twelve patients (54%) treated with vertebroplasty showed new fractures at 3 months compared to 10 (37%) in the control group. This was not statistically different (p=0.049). In the vertebroplasty group, the new fractures involved vertebrae adjacent to the treated vertebra in 77% of cases (p=0.009) compared to only 15% in the control group. During the 3-month period, 3 patients, including 2 treated with vertebroplasty, required hospital admission due to fracture related acute lumbar back pain. CONCLUSION: The small amount of injected cement does not prevent fractures of adjacent vertebrae but does reduce the extravasation of PMMA in adjacent tissues.

Pressure pulse injection: a powerful alternative to electrokinetic sample loading in electrophoresis microchips.

We present a new and simple capillary electrophoresis microsystem in which the sample is injected hydrodynamically using a pressure pulse. This technique maintains the sample composition, in contrast to a classical electrokinetic injection, in which the magnitude of the electric field in the sample reservoir in combination with variations in electrophoretic mobility can lead to a biased injection. The sample is loaded using a well controlled and variable pressure pulse (0.1-1.0 s) generated by the mechanical actuation of a flexible membrane placed on the chip sample reservoir. A fluorescein/calcein-containing borate-Tris-hydroxymethylaminoethane (TRIS) sample solution is taken as a model system for CE analysis. The separation results using pressure pulse injection clearly demonstrate the advantages of our technique. In addition to the reduced bias due to the absence of an electrode in the sample well, this method allows injection of variable plug volumes by simply changing the pulse length. Moreover, a very high speed, repeatability, and sensitivity of the separation is obtained.

Noradrenergic-GABAergic interaction in anterior hypothalamus from normotensive and sinoaortic denervated rats.

1. GABA content is decreased in anterior hypothalamus and medulla oblongata of hypertensive rats by sinoaortic denervation (SAD) when compared to control animals which underwent a sham-operation (sham). 2. Lesion of noradrenergic pathways by 6-hydroxydopamine (6-OHDA), intracerebroventricularly administered, induced depletion of noradrenergic content in frontal cortex, anterior and posterior hypothalamus in both SAD and sham-operated rats. 3. As a consequence of this noradrenergic depletion there was an increase of GABA content in anterior hypothalamus only, from sham- and SAD-operated animals, without changes in other areas. 4. There is a noradrenergic-GABAergic interaction in the anterior hypothalamus of normotensive rats which is not impaired in hypertensive rats by sinoaortic denervation.

GABAergic mechanism involved in sinoaortic denervation in rats.

GABAergic neurotransmission in sinoaortic denervated (SAD) rats with that in sham-operated animals 15 days after operation. In sham-operated rats, glutamic acid decarboxylase (GAD) and 4-amino-butyrate-2-oxoglutarate aminotransferase (GABA-T) activities were higher in dorsal than in ventral regions of pons and medulla oblongata and a higher GAD activity was observed in anterior than in posterior hypothalamus. Fifteen days after SAD, GAD and GABA-T activities were significantly reduced in dorsal pons and in anterior hypothalamus whereas GABA-T activity was increased in ventral medulla oblongata. The results indicate the involvement of GABAergic neurotransmission in the deafferentation of the nucleus tractus solitarii by sinoaortic denervation. GABA hypothalamic inputs could be involved in the baroreflexes.

Studies on the GABAergic system in cardiovascular control in normotensive and in sinoaortic denervated rats.

The cardiovascular effects of i.v. gamma-amino-beta-hydroxybutyric acid (GABOB) were investigated in rats anaesthetized with urethane. GABOB produced a dose-dependent hypotensive response. Treatment with GABA-A receptor antagonists prevented the GABOB response while the GABA stimulation by diazepam enhanced this response. The beta 1-adrenoceptor antagonist reduced the GABOB-induced hypotension but beta 2-adrenoceptor antagonists did not affect it. Picrotoxin, bicuculline or diazepam produced an increase in basal blood pressure. Fifteen days after sinoaortic denervation in rats the glutamic acid decarboxylase and the aminobutyric acid transaminase (GABA-T) activities were significantly reduced in dorsal pons and in anterior hypothalamus whereas GABA-T activity was increased in ventral medulla oblongata. Our results demonstrate that GABOB stimulates GABA-A receptors in anaesthetized rats and thus exerts a neuromodulatory effect on cardiovascular function. GABAergic neurotransmission participates in the sinoaortic deafferentation in rats.