Three-dimensional force measurements on mandibular implants supporting overdentures.

The purpose of this study was to determine masticatory and functional forces in three axes on mandibular implants supporting overdentures. Five edentulous test subjects were selected, each having two mandibular implants. Three-dimensional piezoelectric force transducers were mounted on the two-part ITI Bonefit implants and rigidly connected to the denture. Forces in vertical, lateromedial, and anteroposterior directions were measured by means of electrostatic plotter records. The test modalities were light tapping, grinding, maximal occlusal force, and chewing test food. Results showed that the five subjects developed similar stress patterns but quantitatively different occlusal and chewing forces. In all but one subject, reduced maximal occlusal force was found compared to dentate subjects and edentulous subjects with fixed partial prostheses supported by implants. The recordings of chewing cycles when eating test food resulted in very regular rhythmic strokes, similar to those of dentate subjects but with slightly reduced speed. All stress patterns showed that occlusal and chewing forces were mainly directed in vertical, medial, and anterior dimensions. The dominating component was vertical.     

Binding and antimineralocorticoid activities of spirolactones in toad bladder

The role of the soluble pool (cytoplasmic or cytosolic) of [3H]-aldosterone binding sites in the toad bladder was assessed by the use of two spirolactones, prorenone and spironolactone as a reference drug. Prorenone fulfills all the criteria for a specific competitive antagonist of aldosterone for its effect on Na+ transport. Compared with spironolactone (Ki approximately equal to 1 microM), prorenone was about eightfold less potent (Ki approximately equal to 8 microM). Competition for [3H]aldosterone binding sites by spironolactone and prorenone revealed an order of potency (spironolactone greater than prorenone) that corresponded to their antagonist activities in the Na+ transport assay. There was a linear correlation between the effects of the two spirolactones on the aldosterone-stimulated Na+ transport and their ability to displace [3H]aldosterone from its binding sites in the soluble pool. Finally [3H]prorenone binding sites were detected in the soluble pool but an insignificant number of antagonist-receptor complexes were found associated with the nuclear pool. Our study indicates that the aldosterone binding sites of the soluble pool are indeed mineralocorticoid receptors, which are probably the first intracellular mediators leading to an increased Na+ reabsorption.     

Blood-liquor distribution of ampicillin in children with meningitis and without (author's transl)]

The distribution of ampicillin between blood and cerebrospinal fluid was compared in patients with serous meningitis to that in patients without inflammation of the meningeal membranes. Ampicillin was applied as a continuous intravenous infusion. Samples of blood and cerebrospinal fluid were taken after 1,2,4 or 12 h for the determination of the ampicillin concentrations. In both groups of patients the ratio of concentration in cerebrospinal fluid to concentration in plasma rose between the first and second hour after administration and reached a steady-state value thereafter. This steady-state ratio was 0.025 in patients without meningitis and 0.061 in patients with meningitis. These results are discussed in the context of a pharmacokinetic model which describes the distribution of drugs between blood and cerebrospinal fluid.     

Arteriovenous malformation of the vertebral artery

A case of congenital arteriovenous fistula of the vertebral artery is presented. The hemodynamic, diagnostic and therapeutic aspects of this malformation are discussed. Diagnosis was suspected clinically and confirmed by angiography. It was successfully treated surgically by ligation of the vertebral artery and excision of the fistula.     

A third Na+-binding site in the sodium pump

The sodium pump, or Na,K-ATPase, exports three intracellular sodium ions in exchange for two extracellular potassium ions. In the high resolution structure of the related calcium pump, two cation-binding sites have been identified. The two corresponding sites in the sodium pump are expected to be alternatively occupied by sodium and potassium. The position of a third sodium-specific site is still hypothetical. Here, we report the large effects of single residue substitutions on the voltage-dependent kinetics of the release of sodium to the extracellular side of the membrane. These mutations also alter the apparent affinity for intracellular sodium while one of them does not affect the intrinsic affinity for potassium. These results enable us to locate the third sodium-specific site of the sodium pump in a space between the fifth, sixth, and ninth transmembrane helices of the alpha-subunit and provide an experimental validation of the model proposed by Ogawa and Toyoshima [Ogawa, H. & Toyoshima, C. (2002) Proc. Natl. Acad. Sci. USA 99, 15977-15982].     

Effects of neuropeptide Y on the blood pressure response to various vasoconstrictor agents

Neuropeptide Y (NPY) is known to potentiate the pressor effect of norepinephrine. In the present work, we evaluated in unanesthetized normotensive rats the effect of NPY on blood pressure responsiveness not only to norepinephrine, but also to tyramine, a sympathomimetic agent acting indirectly to B-HT933, a selective alpha-2 adrenoceptor stimulant, to angiotensin II and vasopressin. Dose-response curves to the various pressor agents were established starting at the 45th min of an i.v. infusion with either NPY (0.025 and 0.1 microgram/min) or its vehicle. The two doses of NPY increased blood pressure by an average of approximately 6 mm Hg, which was not significantly different from the vehicle-induced blood pressure changes. NPY significantly enhanced the pressor effect of norepinephrine, tyramine and angiotensin II, but not that of B-HT933 and vasopressin. We also tested whether NPY inhibits the enzyme activity of Na, K-adenosine triphosphatase using a purified toad kidney preparation. Concentrations of NPY from 10(-14) M up to 10(-6) M had no effect on the enzyme activity. It appears therefore that the blood pressure potentiating effect of NPY is not restricted to alpha adrenoceptor stimulation with norepinephrine, but involves also the vasoconstrictor hormone angiotensin II. This NPY-induced potentiation does not seem to depend upon stimulation of alpha-2 adrenoceptors or inhibition of Na,K-adenosine triphosphatase.     

Complete genome sequence of a novel badnavirus, banana streak IM virus

In 1999, banana streak disease outbreaks occurred at two locations in Australia in new banana hybrids that were being screened for fusarium wilt resistance. Two different badnaviruses, banana streak GF virus and a newly discovered virus called banana streak IM virus (BSIMV), were detected in these plants. The complete nucleotide sequence of the BSIMV genome was determined and comprised 7768 nt. Three open reading frames were detected, the first beginning with a non-conventional start codon (CUG). A 55-nt repetition in the putative pregenomic RNA promoter was also identified. Phylogenetic analysis suggests that BSIMV is most closely related to banana streak VN virus.