Lower body negative pressure identifies altered central vein characteristics without accompanying changes to baroreflexes in astronauts within hours of landing.

Cardiovascular deconditioning and altered baroreflexes predispose returning astronauts to Orthostatic Intolerance. We assessed 7 astronauts (1 female) before and following long-duration spaceflight (146 ± 43 days) with minimal upright posture prior to testing. We applied lower body negative pressure (LBNP) of up to - 30 mmHg to supine astronauts instrumented for continual synchronous measurements of cardiovascular variables, and intermittent imaging the Portal Vein (PV) and Inferior Vena Cava (IVC). During supine rest without LBNP, postflight elevations to total peripheral resistance (TPR; 15.8 ± 4.6 vs. 20.8 ± 7.1 mmHg min/l, p < 0.05) and reductions in stroke volume (SV; 104.4 ± 16.7 vs. 87.4 ± 11.5 ml, p < 0.05) were unaccompanied by changes to heart rate (HR) or estimated central venous pressure (CVP). Small increases to systolic blood pressure (SBP) and diastolic blood pressure (DBP) were not statistically significant. Autoregressive moving average modelling (ARMA) during LBNP did not identify differences to either arterial (DBP → TPR and SBP → HR) or cardiopulmonary (CVP → TPR) baroreflexes consistent with intact cardiovascular control. On the other hand, IVC and PV diameter-CVP relationships during LBNP revealed smaller diameter for a given CVP postflight consistent with altered postflight venous wall dynamics.

The upper limit of normal CSF opening pressure is related to bilateral transverse sinus stenosis in headache sufferers.

There are limited data on the relationship between normal cerebrospinal fluid (CSF) opening pressure and bilateral transverse sinus stenosis (BTSS); there are also several conflicting reports about the upper limit of normal CSF opening pressure. To evaluate the influence of BTSS on the upper limit of normal CSF opening pressure, we prospectively recorded lumbar CSF opening pressures in 217 adult patients with neurological symptoms who underwent cerebral magnetic resonance venography (MRV). The CSF opening pressures ranged between 65 and 286 mmH(2)O (mean = 149.3, s.d. = 47.5). The upper limit of opening pressure in patients with both normal appearance of transverse sinuses and unilateral transverse sinus stenosis on MRV (n = 167) was 195 mmH(2)O with a range of 65-195 mmH(2)O. All patients with BTSS were headache sufferers, and the upper limit of opening pressure in patients with BTSS (n = 50) was 286 mmH(2)O with a range of 91-286 mmH(2)O. All patients with opening pressures > 200 mmH(2)O displayed BTSS, whereas only 13% of patients with a pressure < 200 mmH(2)O displayed BTSS. Our findings demonstrate that the upper limit of normal CSF opening pressure is related to BTSS, and they also highlight that headache sufferers with opening pressures > 200 mmH(2)O should be tested for BTSS by MRV.

Ultra-narrow emission from single GaAs self-assembled quantum dots grown by droplet epitaxy.

We realized ultra-narrow excitonic emission from single GaAs/AlGaAs quantum dots (QDs) grown by a refined droplet epitaxy technique. We found that uncapped quantum dots can be annealed at 400 degrees C without major changes in their morphology, thus enabling an AlGaAs capping layer to be grown at that temperature. Consequently, we demonstrate a fourfold reduction of the linewidth of the emission together with an increased recombination lifetime, compared to the conventional droplet epitaxial QDs. The averaged linewidth of neutral excitons measured by micro-photoluminescence on single quantum dots was around 35 microeV.

Bilateral transverse sinus stenosis and idiopathic intracranial hypertension without papilledema in chronic tension-type headache.

Previous MR studies have established that bilateral transverse sinus stenosis (BTSS) predicts idiopathic intracranial hypertension without papilledema (IIHWOP) in migraine. However, it is uncertain whether BTSS identifies IIHWOP in patients with chronic tension-type headache (CTTH): using cerebral MR venography this study aimed to address this question.In a prospective study from February 2002 to December 2006, 198 consecutive patients with CTTH underwent MR venography. Of these patients, 58 underwent lumbar puncture to measure cerebrospinal fluid (CSF) pressure. MR venography and lumbar puncture were also performed in 45 age-matched control subjects. BTSS was considered present when the signal flow was poor or lacking (flow gap) in the mid-lateral portion of both transverse sinuses. IIHWOP was diagnosed if the patient met the diagnostic criteria for idiopathic intracranial hypertension and did not have papilledema. Among the 198 patients with CTTH who underwent MR venography, 18 (9%) had BTSS. Thirteen of these 18 patients with BTSS underwent lumbar puncture, and nine (69.2%) had IIHWOP. CSF opening pressure was normal in all 45 patients as well as in all 45 controls with normal MR venography.These data suggest that BTSS on MR venography is associated with increased intracranial pressure in the absence of papilledema in patients with headache mimicking CTTH.

Transverse sinus stenoses persist after normalization of the CSF pressure in IIH.

BACKGROUND: Bilateral transverse sinus (TS) stenosis has been found in more than 90% of patients with idiopathic intracranial hypertension (IIH). OBJECTIVE: To evaluate whether TS stenosis changed after normalization of CSF pressure in patients with IIH during medical treatment. METHODS: Fourteen consecutive patients with IIH with bilateral TS stenosis on cerebral MR venography (MRV) during the medical treatment were studied. Patients were followed for over a 6-year period. During the follow-up, patients underwent repeated lumbar punctures (LPs) and cerebral MRV. MRV was always performed before each LP. RESULTS: TS stenosis persisted in all the patients during the follow-up. In 9 of 14 (64%) patients with IIH, CSF pressure normalized during medical treatment. CONCLUSIONS: Transverse sinus (TS) stenoses, as revealed by MR venography, persist in patients with idiopathic intracranial hypertension after normalization of CSF pressure, suggesting the lack of a direct relationship between the caliber of TS and CSF pressure.