A unique distortion in K1/3Ba2/3AgTe2: X-ray diffraction determination and electronic band structure analysis of its incommensurately modulated structure.

The incommensurately modulated structure of a square Te-net, namely that of K1/3Ba2/3AgTe2, is determined from single-crystal X-ray diffraction data within a (3+1)D higher dimension formalism. The phase is shown to crystallize in the monoclinic symmetry, P2(1)(alpha 0 gamma) superspace group with the following lattice parameters: a = 4.6441(10) A, b = 4.6292(12) A, c = 23.765(9) A, and beta = 101.28(2) degrees with q = 0.3248(6)a* -0.071(8)c*, that is, in a symmetry different from that reported for the average structure (tetragonal) or that assumed from electron diffraction measurements (orthorhombic). After the introduction of a crenel function for the Te displacive description, the refinement converged to a residual factor R = 0.033 for 2583 observed reflections and 115 parameters (R = 0.024 and 0.101 for 1925 main reflections and 658 first-order satellites, respectively). The [Ag2-Te2] and the Ba/K layers are found to be only weakly modulated. The modulation of the square Te-net is, however, both substantial and unique. Namely, it results in two different units: a "V"-shaped Te3 trimer and a "W"-shaped Te5 pentamer. To examine both unit types, which are segregated in domains that aperiodically alternate within the Te layers, first principles electronic band structure calculations were carried out for three model commensurate structures using the tight-binding linear-muffin-tin-orbital method (LMTO). The calculations show that the distorted structures of V-pattern (model 2) and W-pattern (model 3) are more stable than the average structure (model 1) and that the V-pattern distortion provides a slightly larger stabilization than does the W-pattern distortion. The Fermi surface calculated for the average structure shows nesting vectors that are consistent with the occurrence of the V- and W-pattern distortions in the Te layers. However, these vectors do not predict the observed modulation vector of the incommensurately distorted structure, because the stabilization energy associated with the distortion is not mainly dominated by the energy lowering of the occupied band levels near the Fermi level.

A double blind, randomised, parallel group study to investigate the dose equivalence of Dysport and Botox in the treatment of cervical dystonia.

OBJECTIVE: This study was designed to establish whether a ratio of three units of Dysport is equivalent to one unit of Botox for the treatment of cervical dystonia. METHODS: Patients with predominantly rotational cervical dystonia, and a minimum of four previous Botox treatments, were randomised to receive either the clinically indicated dose of Botox or three times that dose in Dysport units. Study botulinum toxin was administered in a double blind fashion, to one or more clinically indicated muscles, at one or more sites per muscle. Patients returned for assessment two, four, eight, and 12 weeks after treatment. RESULTS: A total of 73 patients (Dysport, 38; Botox, 35) were entered. The Dysport group received a mean (SD) dose of 477 (131) (range 240-720) Dysport units, and the Botox group received a mean (SD) dose of 152 (45) (range 70-240) Botox units. The mean (SEM) post-treatment Tsui scores for the Dysport group (4.8 (0.3)) and the Botox group (5.0 (0.3)) were not statistically different (p=0.66). The study had 91% power to detect a clinically significant difference of two points. Both groups showed substantial improvement in Tsui score by week 2 (mean (SD); Dysport, 46 (28)%; Botox, 37 (28)%), with a peak effect at week 4 (mean (SD); Dysport, 49 (29)%; Botox, 44 (28)%). A similar response profile was seen for other assessments of efficacy. The duration of effect, assessed by time to retreatment, was also similar (mean (SD); Dysport, 83.9 (13.6) days; Botox, 80.7 (14.4) days; p=0.85). During the study 22 of 38 (58%) Dysport patients reported 39 adverse events, and 24 of 35 (69%) Botox patients reported 56 adverse events (p=0.35). A global assessment of efficacy and safety considered that 29 of 38 (76%) Dysport patients and 23 of 35 (66%) Botox patients were treatment successes (p=0.32). CONCLUSION: Patients with predominantly rotational cervical dystonia treated with the clinically indicated dose of Botox or three times that dose in Dysport units show similar improvements and do not have significantly different safety profiles.

Moyamoya with arterial anomalies: relevance to pathogenesis.

We report five patients with moyamoya associated with arterial anomalies, including five aneurysms, one with ectasia of the parent artery, a basilar artery fenestration and an arteriovenous malformation. Possible pathogenetic factors for moyamoya are discussed, and a prenatal origin is suggested.

Small town lead levels: a case study from the homes of pre-schoolers in Mt. Pleasant, Michigan.

This study evaluates the relationship between household Pb levels and four variables (home age, distance to road, traffic volume adjacent to the home, and the amount of exposed soil) for 42 homes in a small city. As a whole, Pb levels for the Mt. Pleasant sample were very low compared to large cities. Home age appeared to have the greatest impact on Pb levels as determined by atomic absorption soil = 65 microg g(-1), vacuum dust = 620 microg g(-1), window sill = 291 microg m(-1), indoor play area = 22 microg m(-1), and home entrance = 291 microg m(-1). The correlation coefficient for increasing home age and soil Pb level was r=0.63 (p<0.000). An inverse relationship (r=-0.45, p=0.003) occurred between soil Pb levels and distance from the road. Household Pb levels generally increased both with higher traffic volumes and greater amounts of exposed soil although both trends were not statistically significant. Study participants kept their home in a good to excellent state of repair and resided on lightly trafficked streets; as such, Pb deposition through the weathering of Pb-based paint and the former combustion of leaded gasoline was minimized.

CT-scanning and magnetic resonance imaging in idiopathic spasmodic torticollis.

Twenty-five consecutive patients with idiopathic spasmodic torticollis (IST) were investigated with computerized tomography (CT) or magnetic resonance imaging (MRI) of the brain. In only six patients (24%) did CT or MRI reveal brain pathology (focal cortical atrophy and lacunary infarcts). No consistent pathological pattern was detected. Consequently, CT and MRI of the brain provides little diagnostic information in this disorder.

Electrical field stimulation in cerebral and peripheral arteries: a critical evaluation of the contractile response.

Electrical field stimulation with recording of isometric contraction in vitro was carried out on small circular segments of pial arteries, in comparison with peripheral arteries from several regions of rat, rabbit, cow, cat, dog and man. It was found that tetrodotoxin (TTX)-resistant contractions were obtained more readily in pial arteries of various species, including man, than in peripheral arteries of similar size. In fact, it was not possible to obtain a purely neurogenic response -- without a TTX-resistant change in tone -- in any pial vessels tested. The stimulation parameters that induced TTX-resistant contraction in pial arteries were similar to those weak parameters that could reveal a purely neurogenic response in certain other arteries, such as rabbit central ear artery and rabbit and feline mesenteric arteries. In these arteries, release of noradrenaline (NA) onto postjunctional alpha-adrenoreceptors was found to be fully responsible for the contraction. The contractile response could be considerably potentiated by blockade of neuronal and extraneuronal uptake, prejunctional alpha-receptor blockade, and 4-aminopyridine (4-AP)-induced enhancement of transmitter release. Addition of compounds to prevent oxidation of released NA (EDTA by its ability to bind metal ions, and ascorbic acid-glutathione, which prevents formation of free radicals) did not enhance the neurogenic response. However, not even under any of these conditions was it possible to reveal a purely neurogenic response in cerebral arteries. Only TTX-resistant contractions, likely to be due to direct smooth muscle activation, were obtained. The explanation may be morphological differences related to myogenic propagation, probably together with poorly sensitive alpha-adrenoreceptors, in these pial arteries. The situation was further complicated by the fading of the TTX-resistant contraction which often occurred upon repeated stimulation. Therefore, acceptance of partial blockade by TTX as a criterion for a neurogenic response in cerebral vessels, as by several previous investigators, may lead to misinterpretation of the true nature of the response. Hence, when studying neurogenic mechanisms in vitro in these arteries, parameters other than vascular tone should be recorded in conjunction with electrical field stimulation, such as registration of junction potentials and measurements of released transmitter.

Neuropeptide Y induces and modulates vasoconstriction in intracranial and peripheral vessels of animals and man.

Neuropeptide Y (NPY) has recently been reported to coexist with noradrenaline (NA) in central as well as peripheral noradrenergic nerves. NPY-containing nerve fibres are particularly numerous around blood vessels. Studies were performed on isolated pial arteries as well as on arteries and veins from several peripheral vascular beds from rabbit, cat and man. NPY induced a varying degree of direct contraction of the vessels with an EAm up to 15 mN. Pial arteries were more sensitive than peripheral arteries to NPY (mean EC50 = 7.6 X 10(-9) M). The presence of NPY did not cause any consistent or significant potentiation of the contractile response to NA in any of the vessels tested. Transmural electrical stimulation of the perivascular nerves (including blockade with tetrodotoxin) was performed mainly with auricular artery from the rabbit. Blocking experiments confirmed that the neurogenic contraction was mediated by noradrenergic-type fibres. NPY caused a concentration-related potentiation of the neurally evoked contractile response. The peptide also potentiated the tetrodotoxin-resistant probably non-neurogenic contractions obtained during enhanced electrical field stimulation. It is concluded that NPY interacts with NA during sympathetic nerve activation primarily through a presynaptic effect.

Calcitonin gene-related peptide is present in mammalian cerebrovascular nerve fibres and dilates pial and peripheral arteries.

Calcitonin gene-related peptide (CGRP) is a novel 37-amino acid peptide occurring in neurones within sensory ganglia, in brain stem, as well as in the walls of blood vessels of peripheral organs. Pial arteries of cat showed a well-developed supply of CGRP-positive nerve fibres. The peptide was found to be a potent dilator of both pial and peripheral vessels of rabbit and cat, and of pial vessels from man. The dilatory effect was independent of the vascular endothelium and was not mediated through adrenergic, cholinergic or histaminergic smooth muscle receptors. The neurogenic vasoconstriction induced by electrical field stimulation was temporarily inhibited by CGRP, as studied in central ear arteries from rabbits. The results suggest that CGRP is a transmitter or modulator playing a role in the regulation of vascular tone.

Species variation in the cerebrovascular response to neurotransmitters and related vasoactive agents.

Constrictory and dilatory responses of pial arteries to various receptor stimulants and modulators were evaluated in vitro and compared in rat, rabbit, cat and man. For the constrictory response, differences were noted especially in the rabbit, which responded strongly to histamine but poorly to noradrenaline and prostaglandin F2 alpha. Histamine was a prominent dilator, but only in rat and man. Isoprenaline induced effective vasodilation only in rat, and dopamine was efficient only in human pial arteries.

VIP (vasoactive intestinal polypeptide)-containing nerves of intracranial arteries in mammals.

Immunohistochemical and radioimmunochemical investigations have shown, in various species, the occurrence of numerous nerve fibres containing vasoactive intestinal polypeptide (VIP) in connection with blood vessels of the central nervous system. Pial arteries from pig, cat, and rat have the richest supply of VIP nerve fibres; those of cow, dog guinea pig and hamster have an intermediary number of nerves, while only few are found in pial arteries from the monkey, rabbit, gerbil, and mouse. The regional variation in VIP-nerve density follows the order: cerebral arteries greater than basilar greater than vertebral greater than spinal cord arteries. Unilateral extirpation of either the pterygopalatine or the superior cervical ganglia does not affect the amount or distribution of VIP fibres in the wall of brain vessels of the ipsilateral side. Measurement of the VIP content by radioimmunoassay shows mean concentrations in the pial arteries varying between 19 and 82 pmol/g tissue wet weight. Regional and species variations in measured VIP levels are similar to the variations in distribution of immunoreactive nerve fibres.

Enkephalin-induced dilatation of pial arteries in vitro probably mediated by opiate receptors.

Feline pial arteries in an actively contracted state were dilated in a dose dependent manner by enkephalins and morphine in vitro. This vasodilatation was blocked by naloxone suggesting the presence of opiate receptors in the vessel walls.

The crossed extensor hallucis response in neurological disorders; an electromyographic analysis.

The electromyographic activity in several leg muscles during the elicitation of "the crossed up-going toe sign" (CUT) was studied in patients and compared with that obtained in connection with the Babinski sign and in normal subjects. The results indicate that the patterns of activation and the responsible pathways are different for the CUT and Babinski signs. The difference between the normal subjects and the CUT positive patient is a matter of quantitative difference of coactivation of distal leg muscles during the test procedure rather than a change of reflex patterns.

The significance of a crossed extensor hallucis response in neurologic disorders: a comparison with the Babinski sign.

The significance of a crossed extensor hallucis response on active flexion of the hip was analysed in various neurological disorders. It is concluded that this sign, not formerly described, is a pathological reflex or synkinesia. In the cooperative patient the crossed extensor response is a more sensitive indicator of a minor disturbance within the cortico-spinal motor pathways than the Babinski sign. With lesions above the foramen magnum a crossed extensor hallucis response is observed more frequently than the Babinski sign.