Polyharmonic hypersurfaces into pseudo-Riemannian space forms.

In this paper, we shall assume that the ambient manifold is a pseudo-Riemannian space form N t m + 1 ( c ) of dimension m + 1 and index t ( m ≥ 2 and 1 ≤ t ≤ m ). We shall study hypersurfaces M t ' m which are polyharmonic of order r (briefly, r-harmonic), where r ≥ 3 and either t ' = t or t ' = t - 1 . Let A denote the shape operator of M t ' m . Under the assumptions that M t ' m is CMC and Tr A 2 is a constant, we shall obtain the general condition which determines that M t ' m is r-harmonic. As a first application, we shall deduce the existence of several new families of proper r-harmonic hypersurfaces with diagonalizable shape operator, and we shall also obtain some results in the direction that our examples are the only possible ones provided that certain assumptions on the principal curvatures hold. Next, we focus on the study of isoparametric hypersurfaces whose shape operator is non-diagonalizable and also in this context we shall prove the existence of some new examples of proper r-harmonic hypersurfaces ( r ≥ 3 ). Finally, we shall obtain the complete classification of proper r-harmonic isoparametric pseudo-Riemannian surfaces into a three-dimensional Lorentz space form.

Thalamic hemorrhage. 30 cases studied: clinico-tomodensitometric correlations.

The clinico-tomographic correlations in 30 patients hospitalized for primary thalamic hemorrhage were studied. Arterial hypertension, observed in 90% of patients, represented the most important risk factor. Twenty-six subjects showed a sensory-motor hemisyndrome contralaterally to the lesion, nineteen showed alteration in level of consciousness from confusion to stupor and coma. Twelve subjects had poorly reactive pupils and eleven speech disturbances with involvement of the left thalamus. Seven patients died following hemorrhage; all subjects presented ventricular bleeding, severe disturbance of consciousness and arterial hypertension. On admission to hospital impairment of consciousness was the most significant unfavourable prognostic factor.

gamma-Aminobutyric acid and pentobarbital enhance 2-[3H]oxoquazepam binding to type I benzodiazepine recognition sites in rat and human brain.

2-Oxoquazepam (2oxoquaz) is a novel benzodiazepine which shows preferential affinity for type I benzodiazepine recognition sites. In the present study, we analyzed the effect of gamma-aminobutyric acid (GABA), pentobarbital, and chloride ions on [3H]2oxoquaz and [3H]flunitrazepam ( [3H]FNT) binding to membrane preparations from rat and human brain. GABA stimulated [3H]-2oxoquaz and [3H]FNT binding in a concentration-dependent manner. The maximal enhancement produced by GABA on [3H]2oxoquaz binding was higher than that produced on [3H]FNT binding in both rat and human tissues. In the rat brain, the effect of GABA on [3H]2oxoquaz was similar throughout different brain areas, whereas the effect on [3H]FNT binding was lower in the cerebral cortex and hippocampus than in the cerebellum. Moreover, both [3H]2oxoquaz and [3H]FNT binding were stimulated by chloride ions and pentobarbital. The results are consistent with the hypothesis that type I benzodiazepine recognition sites are linked functionally to the GABA recognition site and the chloride ionophore.

Characterization of 3H-2-oxo-quazepam binding in the human brain.

1. 2-oxo-quazepam (2oxoquaz) is a novel benzodiazepine (BZD) hypnotic containing a trifluoethyl substituent on the ring nitrogen at position 1, which, unlike other BZDs, distinguishes two populations of BZD binding sites. In the present study we characterized the binding of 3H-2oxoquaz to human brain membrane preparations. 2. Self and cross displacement curves for 3H-FNT and 3H-2oxoquaz binding in different brain areas indicate that 2oxoquaz binds with different affinities to two populations of binding sites in the human brain. 3. Competition studies of 3H-2oxoquaz (2 nM) and 3H-FNT (0.5 nM) binding with a series of unlabelled ligands indicate that compounds which preferentially bind to Type I sites are more potent at displacing 3H-2oxoquaz than 3H-FNT from cerebral cortex membrane preparations. 4. The binding of 3H-2oxoquaz is stimulated by gamma-aminobutyric acid (GABA) and pentobarbital in a concentration-dependent manner. 5. The results suggest that in the human brain 3H-2oxoquaz binds with high affinity to a subpopulation of BZD recognition sites (Type I sites) which are functionally linked to the GABA receptor and the chloride ionophore.

Preferential affinity of 3H-2-oxo-quazepam for type I benzodiazepine recognition sites in the human brain.

The hypnotic drug quazepam and its active metabolite 2-oxo-quazepam (2-oxo-quaz) are two benzodiazepines (BZ) containing a trifluoroethyl moiety on the ring nitrogen at position 1, characterized by their preferential affinity for Type I BZ recognition sites. In the present study we characterized the binding of 3H-2-oxo-quaz in discrete areas of the human brain. Saturation analysis demonstrated specific and saturable binding of 3H-2-oxo-quaz to membrane preparations from human cerebellum. Hill plot analysis of displacement curves of 3H-flunitrazepam (3H-FNT) binding by 2-oxo-quaz yielded Hill coefficients of approximately 1 in the cerebellum and significantly less than 1 in the cerebral cortex, hippocampus, caudate nucleus, thalamus and pons. Self and cross displacement curves for 3H-FNT and 3H-2-oxo-quaz binding in these brain areas indicated that 2-oxo-quaz binds with different affinities to two populations of binding sites. High affinity binding sites were more abundant in the cerebellum (95% of total sites), cerebral cortex, hippocampus and thalamus, whereas low affinity sites were predominant in the caudate nucleus and pons. Competition studies of 3H-2-oxo-quaz (2 nM) and 3H-FNT (0.5 nM) using unlabelled ligands indicated that compounds which preferentially bind to Type I sites are more potent at displacing 3H-2-oxo-quaz than 3H-FNT from cerebral cortex membrane preparations. The results suggest that 3H-2-oxo-quaz may be used for selectively studying Type I BZ recognition sites in the human brain.

Evidence for the presence of benzodiazepine receptor subclasses in different areas of the human brain.

The kinetic characteristics of [3H]flunitrazepam ([3H]FNT) and [3H]ethyl-beta-carboline-3-carboxylate ([3H]beta-CCE) were compared in three different areas of the human brain. As revealed by the Scatchard plot analysis the total number of binding sites labelled by [3H]beta-CCE was markedly lower than that labelled by [3H]FNT. In fact, only 50% of the binding sites for [3H]FNT were also available for [3H]beta-CCE. This finding indicates that in the cerebral cortex, hippocampus and cerebellum of the human brain at least 50% of the benzodiazepine recognition sites are that of Type II. This conclusion is further supported by the evidence that CL-218872 (5 X 10(-6) M), a specific ligand for Type I benzodiazepine recognition site, inhibited [3H]FNT binding by 50% in membranes from the above brain areas. The results suggest that two distinct types of benzodiazepines recognition sites are present in different areas of the human brain.