Participation in intellectual disability research: a review of 20 years of studies.

BACKGROUND: Researchers have noted difficulties in attracting adequate numbers of participants with intellectual disabilities (ID) to their studies. METHODS: This study was a review of participation by adults with ID in research conducted in South Eastern Ontario over a 20-year period (1987-2006). Original research studies were identified by local investigators and then reviewed for inclusion and exclusion criteria. The report of each study was then reviewed by three reviewers and key information was extracted. The extent of study participation was calculated using three methods and compared along with key design characteristics. RESULTS: Nine studies met all inclusion/exclusion criteria and provided sufficient data to calculate participation. Among the studies there was a variety of purposes, research designs and recruitment strategies. Using the participant/approached calculation, participation varied between 41.8% and 100%. Higher participation was observed in studies where investigators had direct access to participants, the data collection was non-invasive and consent was required from substitute decision-makers only. There was no clear trend of increasing or decreasing participation over time. CONCLUSIONS: Researchers seeking the participation of adults with ID in their studies must incorporate factors influencing participation into study designs to ensure robust results and effective use of research resources.

Epidemiological features of Turkish patients with sarcoidosis.

Epidemiological characteristics of sarcoidosis differ according to geographical distribution. The aim of our study was to disclose epidemiological characteristics in our country. The data was collected from investigators, who sent information on newly-diagnosed patients via internet. In 2 years 198 female and 95 male patients were enrolled to the study (f/m:2.08). Mean age of patients was 44+/-13 years (17-90). Mean age of male patients was 38+/-12 while mean age of female patients was 48+/-13 (p<0.001). 73.4% of patients were nonsmokers (85.4% of females; 48.4% of males; (p<0.001)). About 50% of our 293 patients were housewives. Familial sarcoidosis was found in 3 patients' first degree relatives. Estimated annual incidence of sarcoidosis for Turkey was calculated as 4 per 100,000 person. According to our study, 2/3 of sarcoidosis patients were women; mean age of patients was 45 and the disease began 10 years later in female patients. 80% of patients were nonsmokers; negative relation between sarcoidosis and smoking was evident especially in women. Familial sarcoidosis frequency was lower compared to other studies in the literature. There was no occupational exposure history in our patients. Our incidence rate, is similar with the results of other European studies.

Prevalence and comorbidity of allergic eczema, rhinitis, and asthma in a city in western Turkey.

BACKGROUND: Allergic diseases co-occur in many patients. There is no published population-based epidemiologic study about allergic diseases in Turkey. OBJECTIVE: The aim of this population-based study was to investigate the prevalence of allergic eczema, allergic rhinitis, and asthma and their co-occurence in Manisa. METHODS: The sample size was calculated using an estimated prevalence of ever wheezing for the analyzed age group. Interviews were conducted with 725 children. The survey instrument consisted of a set of sociodemographic questions plus the questionnaire of the International Study of Asthma and Allergies in Childhood. RESULTS: The mean (SD) age of the children studied was 8.94 (5.16) years. The prevalence of ever having allergic eczema was 4.7% whereas that of current allergic eczema was 3.2%. Current allergic rhinitis and allergic conjunctivitis were present in 14.5% and 13%, respectively. Asthma was reported in 14.7% of the children older than 3 years of age while the prevalence of physician-diagnosed asthma was 7.9%. The burden of allergy was 27.1%. The prevalence of concomitant eczema and rhinitis was 1.9%. Among children aged between 3 and 17 years, 1.5% and 4.7% had asthma along with eczema and rhinitis respectively. Asthma was significantly more common in children with rhinitis (31.5% vs 11.8%; P < .01; odds ratio [OR], 3.45). Asthma was diagnosed in 28.1% of children with eczema and 14% of children without eczema (P = .03; OR, 2.41). CONCLUSIONS: Atopic diseases seem to significantly increase the risk of developing another atopic disease with ORs that range from 2.4 to 3.4.

Effect of recombinant human activated protein C on apoptosis-related proteins.

The recombinant human activated protein C (rhAPC) has been reported to reduce mortality in patients with severe sepsis. An anti-apoptotic effect of rhAPC in sepsis is known, but the mechanism through which it acts on the apoptotic pathway is still unclear. Therefore, immunopositivity of the apoptosis-related proteins Bcl-2, an anti-apoptotic protein, c-myc, a proliferative protein, p-21 and p-53, two apoptotic proteins, was determined after rhAPC treatment in a mouse sepsis model. Sepsis was induced by Escherichia coli endotoxin injection. Increased neutrophil infiltration and immunoreactivity to p53 and p21 were observed in the group with sepsis and these immunoreactivities were decreased by rhAPC treatment. In the sepstic group; immunopositivity of Bcl-2 and c-myc was mild and moderate, respectively. In conclusion; p21- and p53-mediated apoptosis was increased in the sepsis model, and for the first time it has been shown that rhAPC decreases sepsis-induced apoptosis resulting from increased p21 and p53 proteins.

Lipid-layer crystallization and preliminary three-dimensional structural analysis of AcrA, the periplasmic component of a bacterial multidrug efflux pump.

The multidrug efflux complex AcrAB-TolC confers intrinsic drug resistance in Escherichia coli by pumping antibiotics out of the cell. We determined a low-resolution (20 A) structure of AcrA, the periplasmic component, by electron crystallography. Expressed with a His-tag at its carboxyl-terminus, the protein bound to lipid layers containing the nickel-chelating phospholipid DOGS-NTA. Under the lipid layers, AcrA crystallized in layer group P2(1)22, with a unit cell size of 157 by 95 A and a thickness of about 100 A. The four asymmetric units in the unit cell are organized into what appears to be two rings, each with a central opening of 30 A in diameter. Within each ring, the density can be interpreted as following a pseudo-helical path, approximately 210 A long. This length matches that of monomeric AcrA in solution, previously estimated by light scattering and hydrodynamic measurements. On one side the density has a tubular shape, with a thickness of about 25 A, while on the other side the densities of the upper and lower parts of the pseudo-helical path are fused into a shield.

Membrane-bound 3D structures reveal the intrinsic flexibility of annexin VI.

Several quasi-ordered arrays and three two-dimensional crystal forms of annexin VI were obtained on artificial lipid monolayers. Three-dimensional reconstructions of the crystal forms exhibit marked differences in the orientations of the two lobes, revealing flexibility of the linker between the two lobes of annexin VI. Evidence is presented that the lobes may bind the monolayer in a parallel orientation, or an antiparallel orientation, in which the second lobe is turned away from the monolayer. It is hypothesized that annexin VI may also adopt several conformations in vivo, underlying different functional roles.

Crystal structure of bovine annexin VI in a calcium-bound state.

The crystal structure of a calcium-bound form of bovine annexin VI has been determined with X-ray diffraction data to 2.9 A by molecular replacement. Six Ca2+ ions were found, five in AB loops, one in a DE loop. Two loops (II-AB, which binds calcium, and V-AB, which does not) have conformations that differ significantly from those in calcium-free, human recombinant annexin VI. There are only small differences between the calci- and the apo-annexin VI in the rest of the molecule. Calcium by itself does not promote a major conformational change.

El consultorio: carta de presentación ante los pacientes / The dental office: cover letter to the patients

Se revisan y analizan aspectos generales en el mantenimiento de un consultorio y que sirven para carta de presentación para con los pacientes

Electron crystallography of macromolecular periodic arrays on phospholipid monolayers.

Electron crystallography has the potential of yielding structural information equivalent to x-ray diffraction. The major difficulty has been preparing specimens with the required structural order and size for diffraction and imaging in the electron microscope. 2D crystallization on phospholipid monolayers is capable of fulfilling both of these requirements. Crystals can form as a result of specific interactions with a protein's ligand or an analog, suitably linked to a lipid tail; or on a surface of complementary head-group charge. With such choices, the availability of a suitable lipid is limited only by synthetic chemistry. Ultimately, it is the quality and regularity of the protein-protein interactions that determine the crystalline order, as it is with any protein crystal. In the case of streptavidin, the monolayer crystal diffracts beyond 2.5 A. A 3 A projection map reconstructed from electron diffraction amplitudes and phases from images shows density which can be interpreted as beta-sheets and clusters of side chains. It remains to be shown that the monolayer crystals are flat and diffract as well at high tilt angle as untilted. Technological issues such as charging must be resolved. With parallel advances in data collection and processing, electron crystallography of monolayer macromolecular crystals will eventually take its place beside x-ray crystallography and NMR as a routine and efficient structural technique.

The crystal structure of annexin VI indicates relative rotation of the two lobes upon membrane binding.

The crystal structure of bovine liver annexin VI has been determined to low resolution by molecular replacement. The first lobe (domains 1-4) is rotated about 90 degrees relative to the second lobe (domains 5-8). Since the same crystal form (P4(3), 68 X 68 X 205 A) grew from (NH4)2SO4, polyethylene glycol, and sodium acetate with and without added calcium, this probably reflects the structure in solution. When bound to a lipid monolayer both lobes of annexin VI are coplanar. This implies a significant change in conformation upon binding to membranes.

Visualization of beta-sheets and side-chain clusters in two-dimensional periodic arrays of streptavidin on phospholipid monolayers by electron crystallography.

The biotin-binding protein streptavidin was crystallized as two-dimensional periodic arrays on biotinylated phospholipid monolayers. Electron diffraction patterns and images of the arrays embedded in vitreous ice were recorded to near-atomic resolution. Amplitudes and phases of structure factors were computed and combined to produce a 3 A projection density map. The reliability of the map was verified by comparing it to the available x-ray atomic model of the molecule. Projection densities from beta-strands and some amino acid side chains were identified from the electron cryomicroscopy map. These results demonstrate the first near-atomic image of this type of protein periodic array by electron crystallography, which has a great potential to aid in the structural characterization of molecular arrays engineered on a monolayer for various basic or biotechnological applications.

Electron cryomicroscopy of Bacillus stearothermophilus 50 S ribosomal subunits crystallized on phospholipid monolayers.

50 S ribosomal subunits from Bacillus stearothermophilus have been crystallized as 2-dimensional periodic arrays on phospholipid monolayer films at the water-air interface. These crystals were preserved in vitreous ice and imaged with 100 keV electrons under low dose and low temperature conditions. The unit cell parameters of the crystals are a = 371.3(+/- 3.8) A, b = 152.3(+/- 1.6) A, gamma = 96.3(+/- 1.0) degrees. Some of the image arrays of these crystals have twofold rotational symmetry with a phase residual of less than 25 degrees. The mean figure of merit of the merged structure factors from these image arrays out to 20 A resolution is higher than 0.87. The 2-dimensional projection map shows a level of detail not seen in previous structural studies of the 50 S ribosome subunit. Some of these features may be related to the current 3-dimensional model of the subunit. This analysis illustrates the potential of using the electron crystallographic approach for determining the 3-dimensional structure of the 50 S ribosomal subunit crystallized on a monolayer surface. In addition, the structural information retrieved by electron crystallography might be useful for phasing X-ray data towards an atomic resolution model of the ribosome.

Preliminary electron crystallographic analysis of ice-embedded tropomyosin crystals.

Electron images and diffraction patterns of ice-embedded tropomyosin crystalline sheets have been recorded at 100 and 400 kV. Optical diffractograms from the images indicated an elongated, centered unit cell with a = 799.2 +/- 10.6 A, b = 55.1 +/- 3.5 A. Evaluation of the phases in the computed Fourier transforms up to 7 A resolution revealed the presence of symmetry axes consistent with two-dimensional space group cmm. Electron diffraction patterns show diffuse arcs and discrete sampling at a resolution of 5.1 A, arising from the alpha-helical coiled-coil features of the molecule. These results demonstrate that tropomyosin thin sheets are highly ordered and suggest that retrieval of its high-resolution three-dimensional structure may be feasible by electron crystallography.

Differential effects of ryanodine and tetracaine on charge movement and calcium transients in frog skeletal muscle.

1. Charge movement and myoplasmic calcium transients were simultaneously recorded from frog skeletal muscle fibres by using the double-seal Vaseline-gap technique. Calcium transients were monitored with the fluorescent indicator Rhod-2. 2. Ryanodine modified the kinetics and the total amount of charge moved during depolarizing pulses (Q(on)), while it did not significantly modify the charge after repolarization (Q(off)). The extracellular application of 100 microM-ryanodine elicited a temporary initial increase of the delayed component of charge movement (Q gamma) and the calcium transient. Both phenomena were later blocked with the same temporal course and to the same extent. 3. The blockade of Q gamma and the calcium transient was also observed with ryanodine concentrations of 1-10 microM. For membrane potentials positive to -10mV, the Qon measured was larger in the presence of ryanodine; Qoff was not modified. 4. Tetracaine (400-500 microM) blocked a similar delayed component of Qon, identified as Q gamma, as well as the calcium transient monitored simultaneously. This effect was observed in the first minutes after the addition of tetracaine to the extracellular solution. 5. Tetracaine blocked a faster initial component of Qon for voltages positive to -10 mV, corresponding to the voltage range of activation of the calcium current. At these same membrane potentials, Qoff was also reduced to a similar extent to Qon. 6. Ryanodine and tetracaine showed different effects on calcium current. Whereas the slow calcium current was not modified upon the addition of ryanodine, it was completely blocked in the presence of tetracaine. The blockade of the slow calcium current made evident the fast calcium current. The effects of tetracaine on the charge movement, the calcium transient and the slow calcium current were reversible. 7. These results suggest that ryanodine and tetracaine may act at different sites. Ryanodine exerts its effect on the sarcoplasmic reticulum ryanodine receptor, blocking calcium release and Q gamma, while tetracaine at these concentrations may affect the release channel and the dihydropyridine receptor, causing a blockade of the charge movement, calcium transient and calcium current.

Técnica para la polimerización de resina acrílica para dentaduras con irradiación de microondas / Acrylic resin poliymerization technique for dentures with microwaven radiation

Se describe detalladamente la técnica para la polimerización de resina de acrílico para dentaduras con irradiación de microondas, así como las precauciones que deben tomarse y el equipo recomendado

Repetitive stimulation increases the activation rate of skeletal muscle Ca2+ currents.

Voltage clamp experiments were conducted in frog skeletal muscle using repetitive stimulation protocols. The activation rate of Ca2+ currents increased by prepulses to depolarizing potentials or by stimulating the fiber with a frequency of 1.7 Hz at 0 mV. The effect was observable with Ca2+ or Ba2+ ions, and was clearly voltage-dependent. Physiologically, it is relevant that such activation rate increase can take place during a train of action potentials.

Skeletal muscle Ca2+ channels.

Ca2+ channels are widely distributed among different cell types. We shall describe in this paper kinetic properties of voltage-dependent slow Ca2+ channels in mammalian and frog skeletal muscle fibres. In addition, recent data on a fast-activated Ca2+ channel will be presented. Finally, the possible physiological role of the channel will be considered.