Nonlinear and asymmetric open channel characteristics of an ion-selective porin in planar membranes

The open channel characteristics of the bacterial porin Omp32 from Comamonas acidovorans were investigated by means of conductance measurements in planar lipid bilayers of the Montal-Mueller type. Particularly at low salt conditions (< or = 30 mM KCl) Omp32 exhibited some unusual asymmetric and nonlinear functional properties. Current-voltage relationship measurements showed that conductance depends on the orientation of porin molecules and is a nonlinear function of the applied membrane potential. Conductance also depends on the salt concentration in a manner not common to porins and the salt concentration modulates the nonlinearity of conductance-voltage relationships. Omp32 is strongly anion-selective. The nonlinear and asymmetric conductance of the open channel is a new observation in porins.     

Probing the structure of the diphtheria toxin channel. Reactivity in planar lipid bilayer membranes of cysteine-substituted mutant channels with methanethiosulfonate derivatives

Community development for health (CD4H) is defined as the mobilization of communities actually or potentially suffering from a health problem to eliminate its causes or alleviate its consequences. This paper links this with questions of social identity, focusing on issues of ethnicity and 'race', in health promotion. When combined with notions of ethnicity and 'race'. CD4H is frequently a reaction to inequalities which are communally experienced and believed to increase risk of ill-health for the group. This paper theorizes the link between communal experience and activity to promote health, by drawing on sociological theory linking structure and agency. It examines how discourses of belonging and exclusion are enacted in struggles for health. Via examples from the Caribbean and the UK, instances of 'identity politics' in CD4H are identified, viewed as the use of essentialist, binary notions of self and other in the attempt to gain an advantage over the other. It is argued that such instances should not be considered in isolation, but should be viewed as responses to experience, particularly, in the UK context, the experience of racism in the Health Service.     

"I didn't do it:" Responsibility biases in open and closed groups.

Group members often take more responsibility for the group's outcomes than others give to them. Extending evidence that egocentrism can be muted when group members are individuated (the "unpacking effect"), the authors predicted that members of open groups would be less egocentric than members of closed groups. In open groups, the possibility of membership fluctuation reduces collectiveness, breaking the group into individuals, which in turn lessens egocentrism. The authors tested these predictions in a study of groups of students working on a task relevant to their academic success. Members claimed more personal responsibility when they worked in closed groups relative to open groups (egocentrism), and lack of cohesion mediated the open- versus closed-group link to responsibility allocations. Moreover, members of open groups did not take more responsibility after a success than a failure, whereas those in closed, successful groups claimed more credit than members of failure groups (self-serving bias). The discussion suggests that open groups, although often thought to create conflict as members compete, may contribute to a reduction in both egocentrism and self-serving responsibility allocations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Similarity in calcium channel activity of annexin V and matrix vesicles in planar lipid bilayers

Matrix vesicles (MVs), structures that accumulate Ca2+ during the initiation of mineral formation in growing bone, are rich in annexin V. When MVs are fused with planar phospholipid bilayers, a multiconductance Ca2+ channel is formed, with activity essentially identical to that observed when annexin V is delivered to the bilayer with phosphatidylserine liposomes. Ca2+ currents through this channel, from either MV or annexin V liposomes, are blocked by Zn2+, as is Ca2+ uptake by MV incubated in synthetic cartilage lymph. Blockage by Zn2+ was most effective when applied to the side containing the MV or liposomes. ATP and GTP differentially modulated the activity of this channel: ATP increased the amplitude of the current and the number of conductance states; GTP dramatically reduced the number of events and conductance states, leading to well-defined Ca2+ channel activity from either MV or the annexin V liposomes. In the distinctive effects of ATP, GTP, and Zn2+ on the Ca2+ channel activity observed in both the MV and the liposome systems, the common factor was the presence of annexin V. From this we conclude that Ca2+ entry into MV results from the presence of annexin V in these membrane-enclosed structures.     

Simultaneous measurement of spectroscopic and physiological signals from a planar bilayer system: detecting voltage-dependent movement of a membrane-incorporated peptide

We developed an experimental system that can measure spectroscopic and physiological signals simultaneously from ion channels in a planar lipid bilayer, to study the relationship between the structure and function of the ion channels. While the membrane potential was clamped, fluorescent emission and ionic currents were measured simultaneously. The fluorescent emissions from a planar bilayer constructed in a specially designed chamber were monitored exclusively, and the signal intensity was measured with a photon-counting system. The intensity of fluorescence and spectral shape were measured successfully from the planar bilayer, with a high signal-to-noise ratio. The system can measure the intensity of fluorescence from a restricted area of the planar bilayer, with a diameter of 70 micrometer and a focal depth of 15 micrometer. The low background signal was achieved by optimizing the optical system. More than 95% of the measured fluorescence comes from the planar lipid bilayer. A 22-mer peptide with a sequence identical to that of the S4 segment of the electric eel sodium channel domain IV was synthesized and fluorescence-labeled. This peptide formed a voltage-dependent ion channel in a planar bilayer. The changes in the intensity of the fluorescence accompanying ionic currents generated by a voltage clamp suggest that voltage gating involves the insertion of the N-terminal of the peptide into the membrane. The electrical and optical signals were measured with a gate time of 10 ms. This measurement enabled the detection of movement of the membrane-incorporated peptides with channel opening.     

A single fluid level: radiographic aspect of a closed duplication of the ileum (author's transl)

A five-year-old boy is admitted for an important loss of weight with diarrhoea and fever, recently appeared. The clinical investigations find out a ten-centimeter-large tumor, located in the hypogastrium area and x-rays findings, a single fluid level with no evidence of communication on the radiographs after barium meal and barium enema. The operation confirms the previous diagnosis of duplication of the distal small intestine, and sections the absence of opening into the gut lumen. The clinical signs and the presence of gas in that close duplication, are most likely, due to a colon bacillus superinfection.     

A molecular basis for the different local anesthetic affinities of resting versus open and inactivated states of the sodium channel

Among patients with severe mental illness attending a large, urban, outpatient mental health clinic, fathers are described and compared with nonfathers and with mothers on demographic, clinical, and child-related characteristics, and on resources and service needs. While fathers and nonfathers with mental illness differed significantly on most variables, fathers and mothers with mental illness were remarkably similar except on child-related characteristics. Issues regarding fathers' experiences and service needs are discussed.     

Simulations of postvagal tachycardia at the single cell pacemaker level: a new hypothesis

Simulations performed on a single cell model of rabbit sinoatrial node activity after prolonged vagal stimulation have been able to reproduce the known characteristics of cycle length recovery, including the presence of rapid and slow recovery phases and the transient undershoot phenomenon known as postvagal tachycardia (PVT). In the model, the PVT component has been hypothesized to result from the recovery of background levels of the muscarinic K+ current iK,ACh from desensitization due to prolonged exposure to acetylcholine (ACh) neurotransmitter. Other components of the recovery were found to be due to the inactivation of iK,ACh after the hydrolysis of ACh (rapid phase) and the recovery of the hyperpolarizing-activated current i(f) from its ACh-induced inhibition (slow phase). The magnitudes of both the rapid component and the PVT were found to increase linearly with preceding vagally mediated increase in cycle length, whereas the gain of the slow component was found to saturate, reflecting the limited contribution of i(f) inhibition to cycle prolongation.     

Diameter of the common bile duct in the elderly patient: measurement by ultrasound

We wanted to assess the width of the common bile duct (CBD) in an asymptomatic elderly (> 75 years) population, since no previous report has particularly considered the important age-related increase in CBD diameter for this patient group. CBD width of 92 asymptomatic people over 75 years of age (mean 84.7 years, range 75-96 years) without clinical or laboratory evidence for biliary, hepatocellular or pancreatic disease was measured by real-time high-resolution ultrasound of the upper abdomen. All examinations were performed by one experienced radiologist. Mean values were calculated for three groups: patients with and without cholecystolithiasis and after cholecystectomy. Statistical analysis was carried out by analysis of variance. Considering the measurements of all patients, the mean width (+/- SD) of the CBD was calculated as 6.5 +/- 2.5 mm. The difference between patients without cholecystolithiasis (6.2 +/- 2.3 mm) and patients after cholecystectomy (8.7 +/- 2.9 mm) was statistically significant (P < 0.0001). Cholecystolithiasis (6.0 +/- 1.6 mm) proves not to be an additional factor for CBD widening in comparison with patients without stone disease. The CBD of these very elderly subjects shows a considerable increase in comparison with the recommended borderline values in the ultrasound literature. An upper limit of 10 mm seems reasonable for patients with and without cholecystolithiasis. A significant increase in CBD width after cholecystectomy was found and measurements up to 14 mm may occur. Measurements have to be correlated with clinical and laboratory findings.     

Analysis of oxygen radical toxicity in pancreatic islets at the single cell level

Despite extensive studies on streptozotocin, alloxan and nitric oxide toxicity in pancreatic islets the mechanism of oxygen radical induced islet cell death has not been determined. The present study shows at the level of single cells that following exposure to oxygen radicals generated from xanthine oxidase DNA strand breaks occur in cell nuclei within 5-60 min and precede cell death by several hours. Similar kinetics were seen when treating islet cells with the alkylating agent streptozotocin. Immunofluorescence studies demonstrated the endogenous formation of ADP-ribose polymers in nearly all islet cell nuclei within minutes of treatment with xanthine oxidase, indicating activation of the enzyme poly(ADP-ribose) polymerase (PARP). Concomitantly, cellular NAD+ depletion was noted. Nicotinamide largely prevented NAD+ depletion and in parallel resulted in islet cell survival. These findings identify islet cell nuclear DNA as a primary target of oxygen radical toxicity and suggest related pathways of oxygen radical, nitric oxide and streptozotocin toxicity.     

Creating tobacco control policy at the local level: implementation of a direct action organizing approach

This article describes the community activation and policy change process in seven Minnesota communities involved in the Tobacco Policy Options for Prevention (TPOP) study. The study's intervention employed a direct action organizing model, which relies on mobilizing large numbers of people to alter decision making and leverage the power of elites. As part of the organizing process, TPOP organizers and teams made 1,319 personal contacts with community members, generated 309 media stories, and initiated 445 public events related to tobacco use. These actions resulted in the establishment of comprehensive tobacco ordinances in all seven communities. The authors discuss the goals, training, activities and political factors relevant to four phases of the TPOP intervention: information gathering and team recruitment, community awareness building and ordinance development, preparing for city council, and ordinance establishment and enforcement. Included are suggestions for practitioners interested in using policy change and community-based advocacy to resolve public health problems.     

Detection and quantification of melphalan-DNA adducts at the single cell level in hematopoietic tumor cells

Bifunctional alkylating agents, such as melphalan, are widely used in the treatment of hematological malignancies. The effects of these drugs on particular types of hematological cells and the causes of treatment failure are poorly understood. The aim of this work was to establish an ability to measure the extent to which melphalan reacts with the DNA of individual tumor cells, thereby creating new possibilities for molecular pharmacological studies on clinical samples. A novel approach for staining drug-DNA adducts is described in which cells were embedded in agarose and then lysed. The DNA from each cell remained in an ideal state for quantitative immunofluorescent staining using a previously described monoclonal antibody. Immunofluorescence and DNA-Hoechst dye fluorescence were quantified using a cooled slow scan charge coupled device camera and image analysis procedures. Immunofluorescence of drug-treated cells from a human leukemia cell line was partially correlated with DNA content. Mean integrated immunofluorescence of 50 to 100 cells was dependent on drug concentration and was linearly related to adduct levels. In these cells and in chronic lymphocytic leukemia cells obtained from patients, there was considerable intercell heterogeneity in apparent adduct levels. This was also seen in peripheral blood mononuclear cells isolated from a patient after melphalan therapy.     

Statistical analysis of the ratio of open and closed porosities in sintered materials

Translated from Poroshkovaya Metallurgiya, No. 6(330), pp. 36–40, June, 1990.     

The cell wall porin of Nocardia farcinica: biochemical identification of the channel-forming protein and biophysical characterization of the channel properties

The doctrine of sovereign or official immunity has protected medical examiners in cases alleging negligent performance of the autopsy and in cases involving negligent harvesting of organs. It has not protected examiners in cases alleging performance of autopsy without authorization. The medical examiner, therefore, is well advised to determine whether there may be any objection by the next-of-kin to an autopsy and particularly any religious objection-and if there is such an objection, to proceed only after making contemporaneous and documented decision that there is a compelling need for the autopsy.     

Modeling and measurement of the spontaneous mutation rate in mammalian cells

In order to examine the respiratory effects of tonic-clonic seizures and their treatment with i.v. diazepam or lorazepam, we utilized a spontaneously breathing piglet seizure model. A tracheostomy, arterial catheter, and epidural electrodes were inserted and pigs were maintained under ketamine anesthesia. After baseline recordings, seizures were induced with a pentylenetetrazol (PTZ) bolus and a 20 min infusion (5-6 mg/kg/min). After 10 min of PTZ infusion, randomly assigned animals received diazepam (D; N = 7; 0.5 mg/kg), lorazepam (L; N = 7; 0.2 mg/kg), or 0.9% saline (C; N = 7; controls) by rapid peripheral vein injection. Minute ventilation (Ve), Pa(CO2), and the pressure change in response to airway occlusion at end-expiration (P0.1) were measured at standard intervals. All groups had comparable increases in respiratory drive during untreated seizures. Changes in Ve and P0.1 were reduced to at or below baseline values in groups D and L, but not C, from 2 to 45 min after treatment (P < 0.05). No significant changes were observed in Pa(CO2) after either intervention. Following anticonvulsants, the cumulative duration of seizures was significantly reduced in L and D groups, compared to C (P < 0.05). We conclude that increases in respiratory drive occur during tonic-clonic seizures induced with PTZ. Amelioration of seizure activity with lorazepam or diazepam results in a reduction in respiratory drive, but not respiratory failure, in this tracheostomized model.     

Detection of apoptosis at the single-cell level by direct incorporation of fluorescein-dUTP in DNA strand breaks

Apoptosis induced in different cell lines can be detected and quantified in one step. Direct labeling of apoptotic cells (DLAC) was performed by incorporation of fluorescein-dUTP (F-dUTP) in DNA strand breaks by terminal deoxynucleotidyl transferase (TdT). Nick-end-labeling using F-dUTP obviates the need for second-step revelation reagents without reducing the specificity of detection. Cells were analyzed by microscopy or flow cytometry for objective quantification of apoptotic cells in controlled dilution samples. Furthermore, we demonstrate that DLAC is compatible with surface labeling by monoclonal antibodies, allowing dual-color analysis. The data presented here illustrate the simplicity and potential of this method, which allows the preservation of fragile cells and the possibility of combining apoptosis detection with immunostaining.     

Approximations of open quotient and speed quotient from glottal airflow and EGG waveforms: effects of measurement criteria and sound pressure level

A sample of speech acts in everyday discourse referring to persons or events having to do with the term mental retardation was analyzed in order to investigate the belief that language use both constructs and reflects cultural norms that define the social roles of persons reduced to object status through categorical membership. Speech acts gathered suggest four emergent themes: the discourse of category membership, the dichotomy of normal and abnormal, issues of place and space, and fear. These themes were explicated from a social constructionist perspective, displaying the way speech acts construct mental retardation and subvert individuals with the label into demeaned and ridiculed objects of cultural fear.     

Spin-label studies on the anchoring and lipid-protein interactions of avidin with N-biotinylphosphatidylethanolamines in lipid bilayer membranes

The specific binding of hen egg white avidin to phosphatidylcholine lipid membranes containing spin-labeled N-biotinylphosphatidylethanolamines (biotin-PESLs) was investigated by using ESR spectroscopy. Spin-labeled biotin-PEs were prepared with the nitroxide group at position C-5, C-8, C-10, C-12, or C-14 of the sn-2 chain and were incorporated at 1 mol % in lipid bilayer membranes of dimyristoylphosphatidylcholine. Binding of avidin produced a strong and selective restriction of the biotin-PE lipid mobility at all positions of chain labeling, as shown by the ESR spectra recorded in the fluid lipid phase. The spectral components of the fraction of the biotin-PESLs that were not complexed by avidin indicated that the mobility of the bulk membrane lipids was unperturbed by binding avidin, as demonstrated by difference spectroscopy. Comparison of the positional profiles and temperature dependences of the outer hyperfine splittings from the biotin-PESLs suggests that the C-12 and C-14 positions of the avidin-bound biotin-PEs are in register with the C-5 and C-7/C-6 positions, respectively, of the chains of the bulk membrane lipids. This indicates that the biotin-PEs are partially withdrawn from the membrane, with a vertical displacement of ca. 7-8 A, on complexation with avidin. In addition, the specific lipid-protein interaction with avidin results in a selective reduction in the rates of lipid chain motion, as shown by the increased ESR line widths. These data define the way in which avidin is anchored to lipid membranes containing biotin-PEs.