Computer simulations of the diffusion of Na+ and Cl- ions across POPC lipid bilayer membranes.

We have carried out molecular dynamics simulations using NAMD to study the diffusivity of Na and Cl ions across a POPC lipid bilayer membrane. We show that an imbalance of positively and negatively charged ions on either side of the membrane leads to the diffusion of ions and water molecules. We considered the cases of both weak and very strong charge imbalance across the membrane. The diffusion coefficients of the ions have been determined from the mean square displacements of the particles as a function of time. We find that for strong electrochemical gradients, both the Na and Cl ions diffuse rapidly through pores in the membrane with diffusion coefficients up to ten times larger than in water. Rather surprisingly, we found that although the Na ions are the first to begin the permeation process due to the lower potential barrier that they experience compared to the Cl ions, the latter complete the permeation across the barrier more quickly due to their faster diffusion rates.

Effects of a mandibular repositioning appliance on sleep structure, morning behavior and clinical symptomatology in patients with snoring and sleep-disordered breathing.

BACKGROUND: Mandibular repositioning appliances (MRAs) have become an established treatment for snoring and sleep-disordered breathing - though most studies only focused on the evaluation of respiratory variables. METHODS: This single-blind, placebo-controlled case-series study investigated the effects of an individually adjustable MRA on psychopathology, macro-/microstructure of sleep, periodic leg movements, morning performance, mood/affect and psychophysiology. Fifty patients (37 males) aged 59.7 +/- 10.3 years, suffering from primary snoring (7), mild (22), moderate (15) and severe apnea (6), spent 4 nights in the sleep laboratory (adaptation, placebo, drug and MRA night). The drug night is not subject of the present paper. RESULTS: Confirmatory statistics showed an improvement of the snoring index by 72%. Descriptively, the apnea index and the apnea-hypopnea index normalized. A clinical improvement was seen in the Pittsburgh Sleep Quality Index, the Zung Anxiety/Depression Scales and the Epworth Sleepiness Scale. The restless legs syndrome also improved. Polysomnographically, sleep stages REM and 4 as well as REM latency increased, stage 3, movement time, stage shifts and periodic leg movements decreased, as did all arousal measures. Subjectively, morning well-being, drive, affectivity and wakefulness improved. Objectively, attention, motor and reaction time performance, critical flicker frequency as well as muscular strength increased, diastolic blood pressure and the pulse rate decreased. CONCLUSION: Apart from its good therapeutic effects on snoring and respiratory variables (snoring showed complete or partial response in 68%, the apnea-hypopnea index in 67% of the apnea patients), the MRA also improved psychopathology, objective and subjective sleep and awakening quality.

Oct-4 expression in human endometrium.

The transcription factor Oct-4 is crucial for the maintenance of cell pluripotency and is known to be expressed in embryonic stem cells, germ cells and whole embryos at various stages of development. Oct-4 regulates cell fate in a dose-dependent manner and plays a key role in germ-cell tumours. In the past, several stem-cell markers have been detected, and their role in the pathogenesis of diseases has been discussed frequently. Thus, we investigated the expression of Oct-4 comparing its occurrence in endometrium of healthy and diseased women using immunohistochemistry (IHC) and RT-PCR. IHC demonstrated Oct-4 expression in 25 of 60 sections (42%), respectively in 11 out of 25 patients (44%). Oct-4 mRNA was detected by RT-PCR in all tested samples (9 of 9) of endometrium, although the levels of expression varied. To our knowledge, this is the first study demonstrating Oct-4 expression in human endometrium.

Efficiency of an infiltration basin in removing contaminants from urban stormwater.

The efficiency of a Stormwater Infiltration Basin (SIB) to remove contaminants from urban stormwater was assessed in the current investigation. The SIB, installed in an urban suburb in eastern Sydney (Australia), was monitored over seven rainfall events to assess the removal efficiency of the remedial device for total suspended solids (TSS), nutrients (TP, TKN, N(ox), TN), trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn), organochlorine pesticides and faecal coliforms (FC) from stormwater. The weighted average concentration (WAC) of TSS in the stormwater effluent from the SIB was reduced by an average of 50%, whereas the WAC of Cu, Pb and Zn were also reduced by an average 68%, 93% and 52%, respectively. However, the WAC of Cr, Fe, Mn and Ni displays either similar concentrations as the stormwater influent (Cr and Mn), or substantially higher concentrations (Fe and Ni), due possibly to leaching of fine-grained zeolite clay particles in the filtration bed. The mean removal efficiency of the SIB for total phosphorus (TP) and total Kjeldahl nitrogen (TKN) was 51% and 65%, respectively. In contrast, the average WAC of oxidisable nitrogen (nitrate and nitrite nitrogen or N(ox) is about 2.5 times greater in the effluent (1.34 +/- 0.69 mg L(-1)) than in the incoming stormwater (0.62 +/- 0.25 mg L(-1)). The WAC of total nitrogen (TN) was similar for stormwater at the in-flow and out-flow points. The SIB was very efficient in removing FC from stormwater; and the WAC of almost 70000 cfu (100 mL)(-1) at inflow was reduced to <2000 cfu (100 Ml)(-1) at the outflow, representing a mean removal efficiency of 96%. Due to the low concentrations of Cd, organochlorine pesticides and PAHs in the stormwater, it was not possible to assess the efficiency of the SIB in removing these contaminants.

Investigation of the forest-fire model on a small-world network.

It is shown that the forest-fire model of Bak et al. run on a square lattice network with additional long-range interactions in the spirit of a small-world network results in a scale-free system reminiscent of self-organized criticality without recourse to fine tuning. As the number of these long-range interactions is increased, the cluster size distribution exponent is found to decrease in magnitude as the small-world regime is entered, indicating a change in its universality class. It is suggested that such a model could have applicability in the study of disease spreading in human populations.

Simulation studies of polymer translocation through a channel.

Monte Carlo simulation studies of the translocation of homopolymers of length N driven through a channel have been performed. We find that the translocation time tau depends on temperature in a nontrivial way. For temperatures below some critical temperature theta(c), tau approximately T-1.4, whereas for T>theta(c), tau increases with temperature. The low temperature results are in good agreement with experimental findings as is the dependence of tau on the driving field strength. The velocity of translocation displays the same characteristics as found in experiment but the N dependence of tau shows the linear relationship observed in experiment only for large values of N. A possible reason for this is suggested.

Wavelet and receiver operating characteristic analysis of heart rate variability.

Multiresolution wavelet analysis has been used to study the heart rate variability in two classes of patients with different pathological conditions. The scale dependent measure of Thurner et al. was found to be statistically significant in discriminating patients suffering from hypercardiomyopathy from a control set of normal subjects. We have performed Receiver Operating Characteristc (ROC) analysis and found the ROC area to be a useful measure by which to label the significance of the discrimination, as well as to describe the severity of heart dysfunction.

Small-scale spatial and temporal variance in the concentration of heavy metals in aquatic sediments: a review and some new concepts.

Uncertainty associated with data derived by the analyses of heavy metals in aquatic sediment is due to variance produced in the laboratory (precision), plus 'natural', small-scale spatial variance, (or field variance) at the sampling site. Precision is easily determined and is usually reported in contaminant studies, but field variance is poorly understood and seldom documented. It is important to have an understanding of the field variance because if small-scale spatial variance in the concentration of heavy metals is excessive, regional trends may be limited value. Similarly, if temporal change is large, the results of single synoptic surveys may be questionable and the ability to demonstrate anthropogenic contributions over time will be difficult. However, it is evident from the literature that the information needed to address problems of spatial and temporal variance in the field is beyond the resources of most researchers. Analytical precision of about 5% relative standard deviation (RSD) for heavy metal analysis is typical of a well-managed laboratory. Many studies of small-scale spatial variability made during the current investigation indicate that field variance is related to ambient energy and to the type of sedimentological environment. Total variance (analytical plus field variance) is approximately 10% RSD (mean for a suite of nine trace elements) for depositional parts of estuaries and the marine environment, but increases to about 20-35% RSD for the more dynamic parts of the estuarine environment and the fluvial system. Repeated sampling over periods of up to 7 years undertaken during the present study, indicate a similar order of magnitude for temporal variability in these sedimentological environments. A proposed scheme to provide information on field variance is to undertake small-scale spatial and temporal studies in discrete sedimentological environments in the study area after sediment sampling and characterisation has been completed. The comparatively large proportion of total variance associated with small-scale spatial and temporal variability in the field questions the often excessive cost and effort made in attempting minor reductions in analytical precision in contaminant investigations.

Physical resuspension and vertical mixing of sediments on a high energy continental margin (Sydney, Australia).

Four sediment cores from the continental margin adjacent to Sydney were analyzed for 210Pb, 137Cs, trace metals (Ag, Cd, Co, Cu, Mn, Ni, Pb, Zn), iron, dry bulk density, mud and moisture content. The concentrations of trace metals in the total sediment are low at all sites, although slightly elevated concentrations of Ag, Cu, Pb and Zn are present in the fine fraction of sediment (< 62.5 microns) near a major ocean outfall. Concentrations of trace metals in the fine fraction of sediment are similar in the upper 10-15 cm, indicating strong vertical mixing of the sediments, whereas an upward coarsening grain size in the upper 1-3 cm of sediment supports physical resuspension during storms. Sediment accumulation rates on the middle shelf adjacent to Sydney were estimated from downcore profiles of 210Pb and 137Cs and range between 0.2 and 0.4 cm yr-1. Although the mass fluxes of Cu, Pb and Zn within a distance of 2 km from the outfall (up to 36.1, 30.8 and 86.2 micrograms cm-2 yr-1, respectively) are greater than 20 km north of the outfall (< 23.5 micrograms cm-2 yr-1), the low concentrations of trace metals in sediments near the outfall support an efficient dispersal of anthropogenic contaminants on this continental margin.

Detection of anthropogenic Cu, Pb and Zn in continental shelf sediments off Sydney, Australia--a new approach using normalization with cobalt.

Concentrations of Co, Cu, Pb and Zn were determined in 107 surficial sediment samples from the continental margin adjacent to Sydney, Australia. The spatial distributions of trace metals in the sediments and the mud content are similar and increase with greater distance from the coast. In contrast, normalization of the concentrations of Cu, Pb and Zn in the total sediment with Co enables a coastal anthropogenic source to be identified. The spatial distribution of Co-normalized concentrations of Cu, Pb and Zn in total sediment is similar to the distribution of these trace metals in the fine fraction of sediment (<62.5 microm), indicating that Co may be used as a normalizing element for determining contaminant sources in the marine environment near Sydney.

Trace metals and organochlorines in sediments near a major ocean outfall on a high energy continental margin (Sydney, Australia).

Sewage effluent from a large ocean outfall south of Sydney, southeastern Australia, is efficiently dispersed on this high energy continental margin. An enrichment of Ag, Cu, Pb and Zn is only detectable in the fine fraction (<62.5 microm) of sediment. Ag, Co, Cu, Ni, Pb and Zn in the bulk sample correlate strongly with the mud content of surficial sediment, making an identification of the anthropogenic trace metal source difficult using total sediment analyses. The concentrations of HCB and DDE in the total sediment are also slightly elevated near the outfall. In the vicinity of the outfall, the estimated sewage component in the fine fraction of sediment, using Ag, Cu and Zn in a conservative, two-endmember physical mixing model, is <5% and is <0.25% of the total sediment. A greater anthropogenic Pb component in the fine fraction (mean: 24.8%) of surficial sediment compared to Ag, Cu and Zn may suggest a source other than sewage to Sydney continental margin sediments.

Force-extension curves for a single polymer chain under varying solvent conditions.

We show that Langevin dynamics can be used to obtain force-extension curves for a single polymer chain under varying solvent conditions. We find that the chains obey Hooke-type and Pincus regime behavior for Theta and good solvents. However, in poor solvents a coil-strand coexistence is observed in the equilibrium state and this leads to a quite different type of deformation behavior.

[Lung cancer in the DDR with special reference to histological types and cigarette consumption]. / Lungenkrebs in der DDR unter besonderer Berücksichtigung der histologischen Typen und des Zigarettenkonsums.

By an analysis in detail of incidences of lung cancer of the years 1971 to 1984 and of the data of consumption of cigarettes per head in GDR during the years 1960 to 1984 we discussed the further trends of morbidity and mortality in lung cancer in our country. We pointed out: 1. From 1972 to 1985 the mortality of lung cancer in males dropped from 6,023 per year to 5,213, while that of females increased from 698 to 959. 2. In the time from 1971 to 1983 the over-all incidence (crude rates) of lung cancer in males decreased from 87.1 per 100,000 to 75.5 per 100,000, but came up to 77.2 per 100,000 in 1984. The females rose from 9.7 to 12.3 per 100,000 in the same interval. 3. The age related incidences showed different courses not regarding the different levels of both sexes. In the age group of 30-59 we found a significant incidence rise. The incidence of the 60-69 year old males dropped in a range of 10%; that of the females with the same age had an undulating course with rising trend. Males and females of an age of 70 years and older also had an undulating course with increasing trend. 4. Between 1970 and 1979 the proportions of histological types moved. The adenocarcinomas of males rose significantly from 10.0 to 12.6% and that of large cell carcinomas from 3.6 to 6.0%. In the females the proportions of large cell cancers rose also from 4.2 to 7.5%. 5. The histological types of lung cancer have a significant age relation: Undifferentiated cancers and adenocarcinomas decrease with the age while proportions of squamous cell cancers rise with the age. 6. During 1960 to 1969 the market share of filter cigarettes changed from less than 10% to 79% and rose to 91% until 1975. In the same time the cigarette consumption per head of population increased continuously until now (1984: consumption of cigarettes per head 1,845). 7. In the age group of 18-25 the proportions of smokers is 50% and their middle consumption of cigarettes per day amounts to 11 cigarettes. In the age group of 45-55 the proportion of smokers runs to 34% and their cigarette consumption per day comes to 15 cigarettes. The proportion of male smokers amounts to 47%. The proportion of female smokers amounts to 18%.(ABSTRACT TRUNCATED AT 400 WORDS)

[Epidemiologic aspects of the histologic types of lung cancer]. / Epidemiologische Apekte der histologischen Typen beim Lungenkrebs.

An epidemiological study was performed in the county of Erfurt including all lung cancer patients of the years 1963, 1968, and 1972 to 1977, together 2,585 males and 358 females. The following results were found: 1. The incidence of lung cancer increased significantly from 1963 to 1977. 2. About 60% of all lung cancer patients were younger than 70 years. 3. In male patients squamous cell carcinomas prevailed with 44.8%. Small cell cancers came up to 34.6% and adenocarcinomas to 10.1%. Large cell cancers reached 10.5%. These types in female patients had a proportion to each other like 26.9%: 30.8%: 30.4%: 11.9%. The proportion of adenocarcinomas increased significantly during 1963 to 1977. 4. We found a non significant age relation of histological types. The adenocarcinoma and the small cell cancers dropped with rising age. 5. The classification of histological types and the conditions of detection of lung cancers did not change in the study interval. Therefore the altering of patterns of histological types, especially the increase of adenocarcinomas was attached to the beginning of cigarette smoking in younger ages and the increasing proportion of filter tipped brands as well to a variation of exposition against professional cancerogens. 6. Patients with adenocarcinomas have the highest survival rate after 5 years: 8.1%. Squamous cell lung cancer patients have a 5 year survival rate of 6.8%. Patients with small cell cancers and large cell cancers ranged at 2.7% or 2.6%. 7. Peripheral tumors of each histological type will be detected earlier by fluorographic screening than central carcinomas. Therefore the 5 year survival rates of peripheral cancers always are more favourable than that of central cancers. 8. For the problems in exact typing and staging we propose an internationally adjusted definition of tumor localization as a third parameter for prognosis.