Formation of viscoelastic protein droplets on a chemically functionalized surface.

Droplet formation during adsorption of the protein lactoferrin from an aqueous solution on a surface functionalized by plasma deposited poly(acrylic acid) is studied using quartz crystal microbalance and atomic force microscopy. The formation of protein droplets is particularly favored at pH values close to the isoelectric point of lactoferrin, where the molecules carry little excess charge and intermolecular attraction exceeds the molecule-surface interaction. By combining topographic data with information on the system dynamics, it is possible to describe the viscoelastic properties of the adsorbate within a quantitative model for nonhomogeneous layers.

Systemic hypertension in snorers with and without sleep apnea.

To investigate the impact of sleep-disordered breathing events on daytime hypertension (HT) in patients with increased upper airway resistance during sleep, we studied 191 male snorers aged 49.9 +/- 0.8 years. In 116 of them, an apnea-hypopnea index (AHI) above 10--defined as the presence of obstructive sleep apnea (OSA)--was found; the other 75 subjects had an AHI lower than 10 and were classified as habitual snorers (HSN). Prevalence of HT was not different between OSA (56 of 116 = 48 percent) and HSN (33 of 75 = 44 percent) and there was also no difference in systolic, diastolic, and mean blood pressures between the two groups. Hypertensive OSA patients had higher body mass index (BMI) than normotensive OSA subjects (31.4 +/- 0.7 vs 29.4 +/- 0.6; p less than 0.05), but there was no difference in age, AHI, and nocturnal oxygenation parameters. The same was true for the HSN group, with hypertensive subjects being more obese than normotensive subjects (BMI: 30 +/- 0.8 vs 27.3 +/- 0.8; p less than 0.05), but no difference in age and polysomnographic features. Discriminant analysis with HT as the classification variable and age, BMI, AHI, mean, and lowest nocturnal oxyhemoglobin saturation as independent variables, revealed an independent influence on HT only for BMI (F-prob = 0.001). Thus, our results stand against the hypothesis of a causal relationship between sleep-disordered breathing events and daytime hypertension. We conclude that the high prevalence of HT in male snorers is more directly linked to obesity than to sleep apnea, but an independent effect of snoring per se cannot be excluded.

Nasal continuous positive airway pressure for nonapneic snoring?

The feasibility of nasal continuous positive airway pressure (CPAP) for heavy snoring associated with daytime sleepiness was studied in 118 consecutive patients with an apnea hypopnea index below 5. Fifty-nine of them reported daytime sleepiness in a questionnaire and were offered treatment with nasal CPAP. Whereas 48 patients refused it, the remaining 11 (19%) accepted nasal CPAP for home therapy. Acceptors and refusers did not differ in sleep structure, but acceptors had slightly more sleep-disordered breathing events per hour of sleep than refusers. The pressure needed to abolish snoring in these 11 patients was 7.3 +/- 1.6 cm H2O. Six months after prescription, the built-in time counters of the patients' devices were read. By dividing the hours of operation by the days since initiation of treatment, we found a mean daily use time of only 2.8 +/- 1.5 h. Nevertheless, eight patients (73%) reported that their sleepiness had improved with therapy. We conclude that only a minority of nonapneic snorers accept treatment with nasal CPAP on a long-term basis and that this subgroup is not predictable from polysomnography.

Breathing during sleep in patients treated for obstructive sleep apnea. Nasal CPAP for only part of the night.

To determine whether long-term NCPAP therapy influences severity of sleep disordered breathing during the second part of a night when NCPAP is applied for only the first four hours of sleep, we studied 21 patients with OSA receiving NCPAP therapy for 253 +/- 41.6 days. Results from polysomnography for the period after withdrawal from NCPAP (night B) were compared to the corresponding period of sleep prior to initiation of NCPAP therapy (night A). There was no significant change in RDI from night A (53.9 +/- 8.6) to night B (28.7 +/- 3.3), but maximal apnea length diminished from 55 +/- 2.9 s to 40 +/- 2.9 s (p less than 0.05). Whereas daytime Po2 and the amplitude of desaturations during sleep remained equal, overall oxygenation during sleep improved slightly (mean SaO2 night A = 90.6 +/- 0.9 percent; night B = 92.8 +/- 0.5 percent; p less than 0.05). Differences between nights A and B were more prominent the more severe sleep apnea had been prior to treatment and could not be explained by weight loss. There was strong correlation between improvements in oxygenation measurements and the daily time of NCPAP use. In conclusion, we found a subgroup of OSA patients receiving long-term NCPAP therapy with less disturbed ventilation during sleep following use of NCPAP for only the first part of the night, but in the majority of patients, sleep disordered breathing off NCPAP remained unchanged.

Acceptance of CPAP therapy for sleep apnea.

Although NCPAP is the most efficient nonsurgical treatment for patients with OSA, many patients do not accept sleeping with a nose mask. To determine the factors influencing acceptance, treatment with NCPAP was offered to 95 patients with an AHI greater than 15. After the first night on NCPAP, 47 of 65 patients decided to have NCPAP as a home therapy. Excessive daytime sleepiness was more frequently reported by acceptors than refusers. The frequency of complaints about psychomental symptoms such as poor mental performance and bad memory, was not different between the two groups. There was a close correlation between the rate of acceptance and the AHI as well as the number of positive answers to questions about symptoms of daytime sleepiness in a questionnaire, which correlated with the number and length of apneas. Acceptance of NCPAP was found to be dependent on the subjective feeling of impairment by hypersomnolence due to OSA.

Self-reported vs measured compliance with nasal CPAP for obstructive sleep apnea.

To estimate reliability of self-reported compliance with nasal continuous positive airway pressure (CPAP) therapy for obstructive sleep apnea (OSA), we studied 63 OSA patients aged 53.7 +/- 1.2 years (mean +/- SEM) with an apnea hypopnea index (AHI) of 50.8 +/- 2.9 and lowest sleep SaO2 of 65.6 +/- 2.3 percent receiving nasal CPAP for 539 +/- 44 days. During a follow-up polysomnography (PSG) on the pressure prescribed for home therapy (10.3 +/- 0.3 cm H2O), the hours of operation shown on the built-in time counter of the patients' devices were read to determine objective compliance by dividing the run time by the days since initiation of therapy. This parameter was compared with subjective compliance reported in a self-administered questionnaire. Mean measured use time was 4.9 +/- 0.3 h per night, whereas reported daily use time calculated from reported nights a week and hours a night was 6.1 +/- 0.3 h per night. As predominantly patients with poor compliance misestimated daily use time, we conclude that self-reports are unable to distinguish between compliant and noncompliant patients.

Prediction of interstitial lung involvement in rheumatoid arthritis. The value of clinical data, chest roentgenogram, lung function, and serologic parameters.

We initiated the present study to predict interstitial lung involvement in rheumatoid arthritis (RA) by means of logistic regression analysis of clinical data, lung function, chest roentgenogram, and serologic parameters. Fifty-eight nonsmoking patients with RA were randomized from the rheumatologic unit and sent for investigation to the pulmonary department. Bronchoalveolar lavage (BAL) was performed in the middle lobe and the BAL fluid was considered abnormal in case of increased cell count per milliliter and/or lymphocytosis and/or neutrophil granulocytosis; these findings or combinations thereof were found in 42 (72.4 percent) of 58 cases. The patients' data that had an impact on the normality of BAL were the sex (p = 0.001), vital capacity (p = 0.028), peripheral blood T-helper cells (OKT4+) (p = 0.025), DR(+)-lymphocytes (p = 0.002), and antinuclear antibodies (p = 0.025). By means of the logistic regression analysis, it was possible to reach high significance in the prediction of interstitial lung involvement, with a sensitivity of 92.9 percent and a specificity of 75.0 percent (p less than 10(-6)). The efficiency of prediction was 87.9 percent. From these results, we conclude that interstitial lung involvement in RA is predictable from laboratory findings that have been yielded by noninvasive diagnostic techniques. These data should be used in clinical routine monitoring and they may help to facilitate the assessment of whether bronchoscopy is indicated.

Inspiratory muscle performance relative to the ventilatory threshold in healthy subjects.

Inspiratory muscle performance, ventilation, and gas exchange were studied during exercise in healthy subjects to look for typical changes of pattern of contraction at the ventilatory threshold (VT). The steepening of the slope of carbon dioxide output (VCO2) vs oxygen uptake (VO2) at the VT was accompanied by a nonlinear increase of the mean rate of esophageal pressure development (Pes/TI) vs the esophageal pressure time index (PTIes) reflecting both the relative force (Pbreath/Pesmax) and duration (TI/TTOT) required for inspiration. The esophageal pressure time integral within one breath (Pbreath.dTI) was one of the best single predictors of the ventilatory equivalent for oxygen (VE/VO2) at the VT. Moreover, we presented inspiratory muscle load indices as a mirror image of breathing pattern, with the obvious advantage that the ventilation component can be compared with better established methods of presenting ventilatory output. Inspiratory muscle performance during exercise should link the increased metabolic rate to ventilatory output. We conclude that 1) there exists an inspiratory muscle threshold that is well correlated to commonly used gas exchange thresholds, and 2) the efficiency of ventilation and gas exchange during exercise could be linked to pressure and timing of inspiratory muscle contraction.

[Obstructive sleep apnea--a risk factor for arterial hypertension]. / Obstruktive Schlafapnoe--ein Risikofaktor für arterielle Hypertonie.

Obstructive sleep apnea is frequently found in middle-aged men. Usually, these patients are obese and therefore predisposed to hypertension. This study aimed to elucidate the relationships between hypertension, obesity and obstructive sleep apnea in 48 men suffering from sleep apnea. Hypertension was found in 39 of them (= 81%), 27 patients (= 56%) were morbidly obese (Broca index above 125%), 17 patients (= 36%) were moderately obese (Broca index between 100 and 125%) and 4 patients (= 8%) showed normal weight (Broca index below 100%). Severity of sleep apnea did not correlate with obesity or hypertension. Patients with sleep apnea who were hypertensive were significantly (p less than 0.025) more obese than those with normal blood pressure. Compared with an unselected population showing a similar degree of obesity, patients with obstructive sleep apnea showed a higher prevalence of hypertension and this is independent of age. These findings establish sleep apnea as a risk factor for hypertension.

Neural stem cells from human cord blood on bioengineered surfaces--novel approach to multiparameter bio-tests.

Stem cell technology combined with emerging surface nano/micro-technologies provides a new tool for better understanding of the mechanisms involved in cell fate decisions and compound-induced adverse reactions. This article provides state-of-the-art on the development of modern multiparameter bio-tests based on interactions between neural stem cells derived from human cord blood and bioengineered surfaces. Cell growth platforms with controlled content, geometry and spatial distribution of bioactive and stem cell attractive areas were fabricated either by micro-contact printing or piezoelectric spotting of polycationic biomolecules or extracellular matrix proteins (ECM) on cell-repellent surfaces. HUCB-NSCs were shown to adhere, differentiate and respond to neurotoxic MeHgCl on functional domains in a manner dependent on protein type and concentration, cell density and serum conditions. While receptor-mediated interactions with ECM proteins under absence of serum promote neuronal differentiation, non-specific adhesion to polycationic molecules maintain cells attached to the surface in non-differentiated stage. Functional domains were further engineered to create "smart" microenvironment by immobilizing to the surface signaling molecules together with ECM proteins. Stimulation of selected intracellular pathways by molecules of Wnt, Shh, CNTF or Notch type resulted in differentiation of HUCB-NSC to either neuronal or astroglial lineage. Sensor techniques applied to HUCB-NSC included measurements of electrical activity using multielectrode array chips. Spontaneous electrical field potentials of HUCB-NSCs were dependent upon developmental stage of tested cells. Bioengineered surfaces, on protein microarrays and micro-electrode array chips provide a novel approach to the multiparameter bio-tests by adding an important information on the sensitivity of certain molecular pathways and functional cellular responses to selected neurotoxins.

Pt(x)Ru(1-x)/Ru(0001) surface alloys-formation and atom distribution.

The formation of PtRu surface alloys by deposition of submonolayer Pt films on a Ru(0001) substrate and subsequent annealing to about 1350 K and the distribution of the Pt atoms in the surface layer were investigated by scanning tunneling microscopy. Quantitative statistical analysis reveals (i) negligible losses of Pt into subsurface regions up to coverages close below 1 monolayer, (ii) a homogeneous distribution of the Pt atoms over the surface, and (iii) the absence of a distinct long-range or short-range order in the surface layer. In addition, the density of specific adsorption ensembles is analyzed as a function of Pt surface content. Possible conclusions on the process for surface alloy formation are discussed. The results are compared with the properties of PtRu bulk alloys and the findings in previous adsorption studies on similar surface alloys (H. Rauscher, T. Hager, T. Diemant, H. Hoster, F. Bautier de Mongeot and R. J. Behm, Surf. Sci., 2007, 601, 4608; T. Diemant, H Rauscher and R. J. Behm, J. Phys. Chem. C, in press).

Poly(N-isopropylacrylamide) grafted on plasma-activated poly(ethylene oxide): thermal response and interaction with proteins.

Thermoresponsive polymer layers offer the possibility of preparing smart surfaces with properties that are switchable through a phase transition, usually close to the lower critical solution temperature of the polymer. In particular, poly( N-isopropylacrylamide) (pNIPAM) has gained a great deal of attention because it has such a phase transition in a physiologically interesting temperature range. We have prepared ultrathin thermoresponsive coatings by grafting pNIPAM on a plasma-CVD-deposited, poly(ethylene oxide)-like polymer substrate that was activated in an Ar plasma discharge to initiate the grafting. The presence and integrity of pNIPAM was verified by XPS and ToF-SIMS, and a dramatic change in the wettability during the phase transition was identified by temperature-dependent contact angle measurements. The transition from the hydrated to the collapsed conformation was analyzed by temperature-dependent QCM measurements and by AFM. An unusual, reversible behavior of the viscoelastic properties was seen directly at the phase transition from the swollen to the collapsed state. The phase transition leads to a switching from protein repulsion to a state that allows the adsorption of proteins.

Direct identification of critical clusters in chemical vapor deposition.

The kinetics of heteroepitaxial island nucleation on the Si(111) surface during ultrahigh vacuum chemical vapor deposition with the precursor GeH4 was studied by scanning tunneling microscopy. The results can be described within the framework of rate-equation based nucleation theory, modified by an additional energetic barrier for the attachment of adatoms at steps. This barrier results from the passivation of steps by dissociation products from the GeH4 precursor. A critical nucleus size of 9 atoms is derived. Scanning tunneling microscopy images provide direct evidence for the existence of stable clusters consisting of 10 atoms and allow the unequivocal identification of their structure.

Computerized detection of respiratory events during sleep from rapid increases in oxyhemoglobin saturation.

A computerized search for rapid resaturation (RES)--defined as increases in oxyhemoglobin saturation (SaO2) of 3% or more within 10 s--was used to detect apneas and hypopneas during sleep by the episodes of compensatory hyperventilation following them. Results were compared to those from computerized search for desaturations (DESAT)--defined as decreases in SaO2 of 4% or more within 40 s--and to simultaneous polysomnography. We studied 30 patients with obstructive sleep apnea (OSA) with an apnea plus hypopnea index (AHI) of 30.8 +/- 6.9 (median +/- SEM) and 23 habitual snorers (HSN) with an AHI of 7 +/- 1.5. Manual scoring of polysomnography revealed 7965 respiratory events (6192 apneas, 1773 hypopneas) in OSA patients and 940 events (411 apneas, 529 hypopneas) in the HSN group. In OSA patients, the computer found 96% of events by searching for RES and 87% by searching for DESAT. The percentage of computer-found events in OSA classified as true positive was 91% for RES and 97% for DESAT. In the HSN group, 83% of polysomnographically scored events were found by RES and 55% by DESAT, with 72% of RES and 84% of DESAT being true positive. The correlation of the number of computer-found RES with the number of events from polysomnography was better in OSA (r = 0.862, p less than 0.0001) than in HSN (r = 0.722, p less than 0.001). The same was true for DESAT (OSA: r = 0.896, p less than 0.0001; HSN: r = 0.637, p less than 0.01). In conclusion, computer-found rapid resaturations are more sensitive than desaturations for the detection of respiratory events during sleep from oximetry.(ABSTRACT TRUNCATED AT 250 WORDS)

Flow-volume curves in obstructive sleep apnea and snoring.

The diagnostic value of flow-volume curves for sleep apnea was studied in 32 patients with obstructive sleep apnea, 40 simple snorers, and 30 healthy nonsnorers. A sawtooth appearance of the flow-volume curve was seen in 22 of the sleep apnea patients (69%), 14 of the simple snorers (35%), and 10 of the nonsnorers (33%). The ratio of midexpiratory flow (FEF 50) to midinspiratory flow (FIF 50) was greater than 1 in 6 of the sleep apnea patients (19%), 3 of the simple snorers (8%), and 2 of the nonsnorers (7%). Thus, only the sawtooth sign was more frequently found in sleep apnea patients than in controls (p less than 0.01). Sleep apnea patients with a sawtooth appearance of the flow-volume curve had a higher apnea index (38.7 +/- 22 vs. 21.5 +/- 12.1; p less than 0.01) and lower nocturnal minimum oxygen saturation (68.1% +/- 16.8 vs. 81.3% +/- 9.97; p less than 0.01) than those without. In symptomatic snorers, sensitivity of the sawtooth sign for sleep apnea was 72% and specificity 61%, for a FEF50/FIF50 ratio above 1 sensitivity was 17% and specificity 83%. In asymptomatic patients, sensitivity of either sign was extremely poor (33%) and specificity was 67% for the sawtooth sign and 85% for FEF50/FIF50 greater than 1. We conclude that abnormal flow-volume curves are of limited value for predicting sleep apnea.

Indirect immunofluorescent test on spore sampling preparations: a technique for diagnosis of individual mold allergies.

To calculate their respective exposure to mold spores, volumetric spore sampling was performed with Burkard personal air samplers in the homes of six asthmatic patients with different mold allergies, of three patients with baker's asthma and of four healthy controls. The spore samples were investigated with an indirect immunofluorescent test. Spore-specific IgE was detected in the serum of all the asthmatic patients with mold allergies, even in patients with only slightly increased or no detectable specific IgE in Phadezym-RAST. In serum of patients with baker's asthma and healthy controls, no spore-specific IgE was found.