11†Convergence insufficiency: are we making a difference in patients' lives or is it a waste of time!

Convergence insufficiency (CI) is a common condition that can impair visual performance and comfort during close visual work. This prospective study evaluated the effectiveness of interventions on clinical outcomes and quality-of-life using the adult strabismus quality-of-life questionnaire (AS20) in patients with CI.Data was extracted from a database collected at first consultation from 2015 to 2022. Demographics, interventions and outcomes of 84 patients with CI (mean age 47.0±24.9 years) were analysed.Orthoptic exercises were prescribed to 56% of patients, 32% received prisms, 15% received no treatment, with 3 discharged on the same day. At latest follow-up review, 22.6% were recommended to continue exercises, 28.6% had prisms, 1 underwent bimedial resection and 2 had botox. The median follow-up was 5.5(5.0-55)months, 88.1% were discharged with 29.8% following failure to attend and 9.5% deceased. Near-point of convergence (NPC) improved from a median of 15(6-50)cm to 10(6-30)cm. The median AS20 score at presentation were 100(30-100) and 47.5(0-100), and post-intervention were 100(80-100) and 77.5(12.5-97.5) for psychosocial and functional components, respectively.At the latest follow-up, the attendance failure rate was higher for exercises (36%) than for prisms (15%). Improvement was noted in NPC (33%) and mean AS20 scores was 9% higher psychosocially and 32.8% functionally, highlighting the benefits of intervention on patients' quality-of-life.This cohort provides valuable insights into the clinical management of CI, as evidenced by improvements in NPC and AS20 scores. However, the study also found that long-term compliance with treatment is intrinsically challenging, emphasising the importance of disease education.

Assessment of daily exposure of endodontic personnel to extremely low frequency magnetic fields.

AIM: To measure daily exposure levels to extremely low frequency magnetic fields (ELF MFs) in endodontic clinics. METHODOLOGY: In total, 10 subjects (five endodontic trainees, five hygienists) participated. Each volunteer wore a 60-Hz MF measurement device on the left upper arm during working hours. Measurements were taken continuously throughout the working day except at lunch time. Separate measurements were taken for specific items of equipment at several distances. RESULTS: The average MF exposure for the 10 personnel was 0.03±0.04micro-Tesla (µT) (range, 0.01-6.4µT). The average MF exposure of endodontic personnel was lower than that of other hospital personnel according to the literature. Furthermore, all monitored exposure levels were well below the maximum acute exposure level, 500µT, recommended by the International Committee on Non-ionizing Radiation Protection for the protection of workers against ELF MFs. However, relatively high levels of exposure occurred in an operating room and X-ray room, presumably as a result of the use of surgical equipment such as microscopes and monitors, various motors and power cables of X-ray machines with large current flows. CONCLUSIONS: The total average MF exposure level of 0.03µT was lower than the typical background level at home. Although high levels of exposure were measured in an operating room and X-ray room, the MF exposure level to dental personnel was minimal during routine endodontic clinical work.

Simulation of atomic force microscopy operation via three-dimensional finite element modelling.

Numerical modelling of atomic force microscopy cantilever designs and experiments is presented with the aim of exploring friction mechanisms at the microscale. As a starting point for this work, comparisons between finite element (FE) models and previously reported mathematical models for stiffness calibration of cantilevers (beam and V-shaped) are presented and discrepancies highlighted. A colloid probe (comprising a plain cantilever on which a particle is adhered) model was developed, and its normal and shear interaction were investigated, exploring the response of the probe accounting for inevitable imperfections in its manufacture. The material properties of the cantilever had significant impact on both the normal response and the lateral response. The sensitivity of the mechanical response in both directions was explored and it was found to be higher in terms of normal rather than lateral sensitivity. In lateral measurements, generic response stages were identified, comprising a first stage of twisting, followed by lateral bending, and then slipping. This was present in the two cantilever types explored (beam and V-shaped). Additionally, a model was designed to explore the dynamic sensitivity by comparing the simulation of a hysteresis loop with a previously reported experiment, and the results show good agreement in the response pattern. The ability to simulate the scan over an inclined surface representing the flank of an asperity was also demonstrated.

The phosphatidylinositol polyphosphate 5-phosphatase SHIP and the protein tyrosine phosphatase SHP-2 form a complex in hematopoietic cells which can be regulated by BCR/ABL and growth factors.

We report here that interleukin-3 (IL-3) and erythropoietin (EPO) induce formation of a complex composed of two SH2-containing phosphatases, the tyrosine phosphatase SHP-2 and the SH2 containing inositol 5-phosphatase (SHIP). Both SHP-2 and SHIP are known to be involved in growth factor signal transduction, but their potential interaction in the same pathway is novel. SHIP has previously been shown to associate with SHC, and potentially to be involved in regulating apoptosis. In contrast, in some model systems, SHP-2 has been demonstrated to positively regulate cell growth. Both phosphatases in the complex were tyrosine phosphorylated, and the amount of SHIP coprecipitating with SHP-2 was inversely related to the amount of SHIP coprecipitating with SHC. In hematopoietic cells transformed by the BCR/ABL oncogene, this phosphatase complex was found to be constitutively present with both components heavily tyrosine phosphorylated. Also, other proteins were detected in the complex, including BCR/ABL itself and c-CBL. However, transformation by BCR/ABL was associated with a reduced SHIP protein expression, which could further affect the accumulation of various inositol polyphosphates in these leukemic cells. These data suggest that the function of SHIP and SHP-2 in normal cells are linked and that BCR/ABL alters the function of this signaling complex.

Sequential activation of phoshatidylinositol 3-kinase and phospholipase C-gamma2 by the M-CSF receptor is necessary for differentiation signaling.

Binding of macrophage colony stimulating factor (M-CSF) to its receptor (Fms) induces dimerization and activation of the tyrosine kinase domain of the receptor, resulting in autophosphorylation of cytoplasmic tyrosine residues used as docking sites for SH2-containing signaling proteins that relay growth and development signals. To determine whether a distinct signaling pathway is responsible for the Fms differentiation signal versus the growth signal, we sought new molecules involved in Fms signaling by performing a two-hybrid screen in yeast using the autophosphorylated cytoplasmic domain of the wild-type Fms receptor as bait. Clones containing SH2 domains of phospholipase C-gamma2 (PLC-gamma2) were frequently isolated and shown to interact with phosphorylated Tyr721 of the Fms receptor, which is also the binding site of the p85 subunit of phosphatidylinositol 3-kinase (PI3-kinase). At variance with previous reports, M-CSF induced rapid and transient tyrosine phosphorylation of PLC-gamma2 in myeloid FDC-P1 cells and this activation required the activity of the PI3-kinase pathway. The Fms Y721F mutation strongly decreased this activation. Moreover, the Fms Y807F mutation decreased both binding and phosphorylation of PLC-gamma2 but not that of p85. Since the Fms Y807F mutation abrogates the differentiation signal when expressed in FDC-P1 cells and since this phenotype could be reproduced by a specific inhibitor of PLC-gamma, we propose that a balance between the activities of PLC-gamma2 and PI3-kinase in response to M-CSF is required for cell differentiation.

Identification of G-Box Sequence as an Essential Element for Methyl Jasmonate Response of Potato Proteinase Inhibitor II Promoter.

The potato proteinase inhibitor II promoter was studied to identify cis-acting regulatory sequences involved in methyl jasmonate (MJ) response using transgenic tobacco plants carrying various lengths of the promoter fused to a chloramphenicol acetyltransferase reporter gene. An internal fragment between -625 and -520 was sufficient to confer a response to MJ, wounding, or sucrose when it was placed upstream of the nos promoter -101, which contains the CAAT-TATA region. Deletion of the proteinase inhibitor II promoter sequence upstream of -611 did not affect the MJ response, but a further deletion to -573 eliminated the response. The 3'-deletion study showed that the DNA sequence downstream from -520 is dispensable. However, 3'-deletion mutant -574 did not respond to the MJ treatment. These results indicated that an element essential for the MJ response is located at the -574/-573 region where the G-box sequence (CACGTGG) is located. The G-box sequence was not required for the sucrose enhancer effect, suggesting that the MJ response mechanism is different from that of sucrose.

Short term effects of oxidized ascorbic acid on bovine corneal endothelium and human placenta.

Studies on the toxic effects of dehydro-L-ascorbic acid (DHAA) have been extended to include evaluations over time periods up to 3 hr. and to test for specific effects on a membrane transport protein, a membrane-bound enzyme and a soluble intracellular enzyme. In studies on cultured corneal endothelial cells, DHAA concentrations of 1, 2, and 5 mM over 3 hr. had an inhibitory effect on subsequent uptake of DHAA present at a tracer level. Surviving fragments of human placenta and alkaline phosphatase activity of the placental brush-border membrane were susceptible to the effect of DHAA at a high concentration (10 mM). Because intracellular metabolism of DHAA was not affected, and an increase in membrane permeability was not detected, it is concluded that a specific membrane transport protein might be the site of DHAA-induced damage. These studies support the concept that the oxidized form of ascorbic acid (vitamin C) has potential toxic effects on biological systems and suggests that proteins that mediate transport and metabolism may be sites where DHAA causes damage.

Intestinal absorption and metabolism of ascorbic acid in rainbow trout.

Transport and metabolism of the reduced and oxidized forms of vitamin C were evaluated in trout intestine in vitro. Transepithelial fluxes of [14C]ascorbic acid were determined with the substrate present at 10 microM. The mucosa-to-serosa flux was fourfold greater than the serosa-to-mucosa flux with ascorbic acid present in both bathing solutions. Cellular accumulation of the reduced molecule occurred with a final tissue-to-medium ratio of 1.64. Ascorbic acid influx across the brush-border membrane was determined under conditions that inhibit transport of other nutrients. Influx was not reduced because of the presence of the D- or L-stereoisomeric form of glucose but was highly dependent on the presence of Na in the bathing medium. Brush-border influx was saturable with a Km of 220 microM. Short-term (8 min) exposure of intestinal loops to the oxidized form of vitamin C, dehydro-L-ascorbic acid, was followed by high-performance liquid chromatography analysis of the 14C label present in the tissue. Total uptake of substrate was greater from the serosal solution than from the mucosal solution; in either situation most of the 14C label was found in the reduced state. It is concluded that transport and metabolic capabilities are present in the trout intestine to absorb oxidized and reduced forms of vitamin C and to help regulate the redox potential of circulating ascorbic acid by recycling dehydro-L-ascorbic acid.

Transport and metabolism of ascorbic acid in human placenta.

The role of human placenta in cellular transport and metabolism of the potentially toxic oxidized form and the useful reduced form of ascorbic acid was examined in surviving tissue fragments in vitro. At the end of a 60-min incubation with the 14C label nominally present in the reduced form, a tissue-to-medium ratio in excess of unity was reached. The importance of evaluating uptake of the ascorbic acid metabolites is evident from a careful assay of 14C label present in the bathing media. Significant spontaneous oxidation occurs, which is slowed or reversed to a limited extent by the presence of placental tissue. Uptake of the oxidized substrate, dehydro-L-ascorbic acid, proceeds much more rapidly than uptake of ascorbic acid. At the end of a 15-min incubation, most of the substrate taken up was in the reduced form. From an additional evaluation of 14C label in the bath it is calculated that 25% of ascorbic acid formed by the tissue is released within 15 min. The cellular uptake mechanism for dehydro-L-ascorbic acid is not shared by glucose and is not dependent on the presence of Na+ but is dependent on intact cellular metabolism. The finding of avid cellular uptake and reduction of the oxidized form of ascorbic acid supports the concept that the placenta helps to clear the toxic molecule from the maternal circulation, metabolizes it, and delivers the useful reduced form to the fetus.

Regeneration of ascorbic acid by rat colon.

Plants and animals alike use ascorbic acid in a variety of reactions that result in net generation of dehydro-L-ascorbic acid. The ability to reduce dehydro-L-ascorbic acid back to ascorbic acid would conserve "total ascorbate" and would help to maintain the toxic oxidized form of the molecule at a low level. This study evaluated the rate of dehydro-L-ascorbic acid reduction either by following the rate of NADPH consumption or by analysis of the amount of 14C-labeled dehydro-L-ascorbic acid converted to ascorbic acid. A large percentage of the NADPH consumed by a semipurified preparation of rat colonic mucosa in vitro was dependent on the presence of dehydro-L-ascorbic acid. The tissue factor active in regenerating ascorbic acid is intermediate in size between cytochrome c and blue dextran. The present results indicate that the mucosa reduced dehydro-L-ascorbic acid by a cytosolic enzyme that uses NADPH as a hydrogen donor. Subsequent to precipitation by ammonium sulfate, the 55-70% fraction contains most of the reductase activity while consisting of only 17% of the cellular soluble protein.

Intestinal transport and metabolism of oxidized ascorbic acid (dehydroascorbic acid).

The transport and metabolic properties of dehydroascorbic acid have been evaluated in the small intestine of one ascorbic acid-dependent animal species (guinea pig) and one ascorbic acid-synthesizing animal species (rat). Loops of guinea pig jejunum in vitro brought about net transepithelial absorption of L-[14C]dehydroascorbic acid with most of the absorbed substrate appearing in the reduced form (ascorbic acid). Saturation of brush-border transport occurs at a lower concentration than saturation of the enzymatic reduction. Rat intestine did not bring about net transepithelial transport. The intestines of both guinea pigs and rats took up substantial dehydroascorbic acid from the serosal bathing solution, with the majority appearing in the mucosa as ascorbic acid. It is proposed that in guinea pig intestinal mucosa, dehydroascorbic acid reductase has a nutritional role in extracting the vitamin from chyme and reducing it for subsequent use in the body. The intestines of both guinea pig and rat appear to take up dehydroascorbic acid across the basolateral surface and reduce it, thus maintaining a substantial endogenous level of ascorbic acid in the mucosa. The transport and metabolic properties described might play an important role as a protective antioxidant mechanism in intestinal mucosa.