Actin modulates shape and mechanics of tubular membranes.

The actin cytoskeleton shapes cells and also organizes internal membranous compartments. In particular, it interacts with membranes for intracellular transport of material in mammalian cells, yeast, or plant cells. Tubular membrane intermediates, pulled along microtubule tracks, are formed during this process and destabilize into vesicles. While the role of actin in tubule destabilization through scission is suggested, literature also provides examples of actin-mediated stabilization of membranous structures. To directly address this apparent contradiction, we mimic the geometry of tubular intermediates with preformed membrane tubes. The growth of an actin sleeve at the tube surface is monitored spatiotemporally. Depending on network cohesiveness, actin is able to entirely stabilize or locally maintain membrane tubes under pulling. On a single tube, thicker portions correlate with the presence of actin. These structures relax over several minutes and may provide enough time and curvature geometries for other proteins to act on tube stability.

Optogenetic dissection of Rac1 and Cdc42 gradient shaping.

During cell migration, Rho GTPases spontaneously form spatial gradients that define the front and back of cells. At the front, active Cdc42 forms a steep gradient whereas active Rac1 forms a more extended pattern peaking a few microns away. What are the mechanisms shaping these gradients, and what is the functional role of the shape of these gradients? Here we report, using a combination of optogenetics and micropatterning, that Cdc42 and Rac1 gradients are set by spatial patterns of activators and deactivators and not directly by transport mechanisms. Cdc42 simply follows the distribution of Guanine nucleotide Exchange Factors, whereas Rac1 shaping requires the activity of a GTPase-Activating Protein, ß2-chimaerin, which is sharply localized at the tip of the cell through feedbacks from Cdc42 and Rac1. Functionally, the spatial extent of Rho GTPases gradients governs cell migration, a sharp Cdc42 gradient maximizes directionality while an extended Rac1 gradient controls the speed.

Cell-sized liposome doublets reveal active tension build-up driven by acto-myosin dynamics.

Cells modulate their shape to fulfill specific functions, mediated by the cell cortex, a thin actin shell bound to the plasma membrane. Myosin motor activity, together with actin dynamics, contributes to cortical tension. Here, we examine the individual contributions of actin polymerization and myosin activity to tension increase with a non-invasive method. Cell-sized liposome doublets are covered with either a stabilized actin cortex of preformed actin filaments, or a dynamic branched actin network polymerizing at the membrane. The addition of myosin II minifilaments in both cases triggers a change in doublet shape that is unambiguously related to a tension increase. Preformed actin filaments allow us to evaluate the effect of myosin alone while, with dynamic actin cortices, we examine the synergy of actin polymerization and myosin motors in driving shape changes. Our assay paves the way for a quantification of tension changes triggered by various actin-associated proteins in a cell-sized system.

Preservation of extraction socket in immediate implant placement: a clinical study.

AIM: The objective of this study was to compare different approaches temporary restoration in an immediate implant placement. To determine the respective influence of each parameter, two treatment groups were formed; a strict and standardized study protocol was applied to minimize the influence of bias and confounding factors. The Pink Esthetic Score (PES) - the esthetic out-come of soft tissue appearance was evaluated. MATERIAL AND METHODS: Sixteen patients with a single failing tooth in the maxilla and a natural contralateral site were randomly distributed into two groups. Treatment variations affected the provisional restorative in detail, group 1 with immediate implant placement and immediate temporary restoration with the simulation of the first three mm of the root and the seal of the socket, group 2 with immediate implant placement and immediate temporary restoration without the seal of the socket. All patients received the final prosthetic restoration 10-12 weeks after implant placement. Standardized photographs were taken eight months after tooth extraction. Five competent observers analyzed the esthetic outcome according to the PES. RESULTS: The overall scores of the four treatment groups revealed PES values of 8.47 (SD 2.08, group 1), 6.62 (SD 3.24, group 2). The differences between groups 1 and 2 and were statistically significant (P=0.015 and P=0.047). The single parameter analysis displayed a certain range of fluctuation and heterogeneity. CONCLUSIONS: Immediate implant placement and restoration appear to be a suitable alternative to early implant placement if an experienced surgeon is entrusted with the implantation procedure.

Association of perinatal factors and school performance in primary school Chilean children.

The associations between school performance and cognitive abilities with birth characteristics have mostly been studied without taking into consideration the effects of gestational age (GA). Our aim was to study the association between prenatal growth and cognitive function in term-born Chilean school children. A cohort of over 200,000 term-born fourth graders who took the regular national test for school performance was studied. Outcome parameters were language and mathematics test scores in relation to prenatal growth. A total of 256,040 subjects took the test and 220,940 were included in the final study sample. Prenatal growth was modestly, but significantly, associated with school performance. Adjusted ß coefficients for 1 cm increase in birth length were 1.28 and 0.77 for mathematics and language, respectively; the corresponding values for 100 g increase in birth weight were 0.59 and 0.34, respectively. Increased GA was associated with lower test scores. Adjusted ß coefficients for the birth measurements generally had a lower strength of association than those of socio-economic factors. However, the confounders most strongly associated with educational achievements were socio-economic factors, known to be associated with birth size. Lower socio-economic status is known to negatively influence both prenatal growth and cognitive function, supporting the overall importance of prenatal growth in relation to cognitive outcomes.

Ionic liquid-based membranes as electrolytes for advanced lithium polymer batteries.

Gel-type polymer electrolytes are formed by immobilizing a solution of lithium N,N-bis(trifluoromethanesulfonyl)imide (LiTFSI) in N-n-butyl-N-ethylpyrrolidinium N,N-bis(trifluoromethanesulfonyl)imide (Py24TFSI) ionic liquid (IL) with added mixtures of organic solvents, such as ethylene, propylene and dimethyl carbonates (EC, PC, and DMC, respectively), into a poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) matrix, and their properties investigated. The addition of the organic solvent mixtures results in an improvement of the ionic conductivity and in the stabilization of the interface with the lithium electrode. Conductivity values in the range of 10⁻³-10⁻²  S cm⁻¹ are obtained in a wide temperature range. These unique properties allow the effective use of these membranes as electrolytes for the development of advanced polymer batteries based on a lithium metal anode and an olivine-type lithium iron phosphate cathode.

Will architecture win the technology wars?

Success today flows to the company that establishes proprietary architectural control over a broad, fast-moving, competitive space, Charles R. Morris and Charles H. Ferguson claim in "How Architecture Wins Technology Wars" (March-April 1993). No single vendor can keep pace with the outpouring of cheap, powerful, mass-produced components, so customers have been stitching together their own local systems solutions. Architectures impose order on the system and make interconnections possible. An architectural controller has power over the standard by which the entire information package is assembled. Because of the popularity of Microsoft's Windows, for example, companies like Lotus must conform their software to its parameters to be able to compete for market share. Proprietary architectural control has broader implications for organizational structure too: architectural competition is giving rise to a new form of business organization.

Adolescents' first and most recent use situations of smokeless tobacco and cigarettes: similarities and differences.

This study compared first and most recent use situations of adolescent smokeless tobacco experimenters with those of adolescent cigarette experimenters. Structured, open-ended interviews were conducted with 320 seventh and tenth grade youths in 16 Southern California schools. Students were categorized as nonusers (those who had never experimented with any tobacco product), minimal experimenters (those who had experimented with smokeless tobacco or cigarettes between 1 and 9 times), and persistent experimenters (those who had experimented with smokeless tobacco or cigarettes 10 or more times). The situations reported by smokeless tobacco were similar to those reported by cigarette experimenters. The most important differences between the two groups are highlighted. In particular, smokeless tobacco users seemed less concerned about negative social consequences of use than cigarette smokers. In addition, nonusers' observations of use and implications for prevention and cessation are discussed.

Digital foot deformities in the arthritic patient.

Relieving pain and preventing deformity in the rheumatoid foot are best accomplished early in the disease course. Although the treatment of digital deformities may not differ significantly in the rheumatoid versus the nonrheumatoid patient, early and more aggressive management is most important in the rheumatoid patient. The digital deformities associated with inflammatory arthritis are progressive as long as the disease is active. Therefore, it becomes necessary to treat these patients both medically and mechanically to slow the progression of the digital deformities. In determining whether medical, surgical, or biomechanical treatment options are appropriate, the physician must examine multiple considerations. These include disease activity, presence or absence of symptoms, degree of deformity and resultant potential for complications, shoe intolerance, and level of activity. Changing attitudes have dictated that little benefit is gained from withholding treatment until the disease is so-called burnt out. It is in the patient's best interest to maintain function whenever possible to allow for increased productivity. The psychosocial ramifications of this approach are obvious.

[Questionnaire for the evaluation of mental health in adolescence]. / Cuestionario para evaluar salud mental en la edad juvenil.

Procedures resorted to in building up a questionnaire for assessing adolescent's Mental Health are submitted. Questions were selected from DSM-III diagnosis categories and from Goldberg's General Health Questionnaire (GHQ) as well. The following variables were considered: socioeconomic characteristics, developmental level, and normal vs. psychopathologic criteria. The main results may be summarized as follows: a) Reliability and validity of data obtained allow the researchers to infere that this is an apt test for discriminating between normal and psychopathologic adolescents, b) Factorial analysis results confirm the constructional validity of the questionnaire, c) The most relevant variable was normal vs. psychopathological criteria even though the developmental level variable was also of significance. No significative differences were obtained in connection with socioeconomic level, d) As demonstrated in previous papers, psychopathology in adolescents is a mixed syndrome, and e) In similar questionnaires, adolescents got higher scores than adults.

Cuestionario para evaluar salud mental en la edad juvenil. / [Questionnaire for the evaluation of mental health in adolescence]

Procedures resorted to in building up a questionnaire for assessing adolescents Mental Health are submitted. Questions were selected from DSM-III diagnosis categories and from Goldbergs General Health Questionnaire (GHQ) as well. The following variables were considered: socioeconomic characteristics, developmental level, and normal vs. psychopathologic criteria. The main results may be summarized as follows: a) Reliability and validity of data obtained allow the researchers to infere that this is an apt test for discriminating between normal and psychopathologic adolescents, b) Factorial analysis results confirm the constructional validity of the questionnaire, c) The most relevant variable was normal vs. psychopathological criteria even though the developmental level variable was also of significance. No significative differences were obtained in connection with socioeconomic level, d) As demonstrated in previous papers, psychopathology in adolescents is a mixed syndrome, and e) In similar questionnaires, adolescents got higher scores than adults.

Nonmetallic foreign bodies in the foot: radiography versus xeroradiography.

Nonmetallic foreign bodies were embedded in cadaver feet. Standard x-rays and xerograms were taken and compared. The results appear to indicate that standard x-rays remain the more clinically practical means of screening for foreign bodies. The literature regarding xeroradiography suggests that this is superior to radiography in detection of nonmetallic foreign bodies. By embedding nonmetallic foreign bodies in cadaver feet and comparing standard x-rays to xerograms, the examiner should be able to confirm or disprove this premise.

A radiopaque-labeling technique to visualize the distribution of local anesthesia.

The authors describe a technique to inject radiopaque dye for labeling the distribution of local anesthetic and illustrate the method with a case report. They have found the technique useful in establishing the diagnosis and planning treatment for rearfoot pain.