The results of vitreous surgery for chronic macular holes

PURPOSE: To evaluate the visual and anatomic results of macular hole surgery in eyes that have had symptoms of a macular hole for 2 years or longer. METHODS: Fifty-one eyes with chronic macular holes (> or = 2 years' duration) were treated in a retrospective analysis of the results of vitrectomy, 16% perfluoropropane gas tamponade, and one of three adjunctive agents (bovine transforming growth factor beta-2, recombinant transforming growth factor beta-2, or autologous platelet extract). Of 51 eyes, 45 (88.2%) were examined 3 months after surgery. Visual acuity of these 45 eyes was measured preoperatively and 3 months postoperatively using the Early Treatment Diabetic Retinopathy Study (ETDRS) visual acuity chart. Twenty-eight eyes (62.2%) had no prior vitrectomy and 17 eyes (37.8%) had a prior vitrectomy for the macular hole that failed. RESULTS: The macular holes had a mean duration of 3.7 years and were successfully closed in 32 of 51 total eyes (62.7%) and 32 of 45 eyes (71.1%) that were examined 3 months after surgery. The mean preoperative visual acuity was 20/100 -2 and the mean visual acuity at 3 months was 20/80 for a mean gain of 6.6 ETDRS letters (+ 1.3 lines). Of 45 eyes, 17 (37.8%) were 20/63 or better 3 months after surgery; 21 (46.7%) gained 2 or more ETDRS lines. There was no statistically significant difference in macular hole closure (P = 0.311) or visual acuity change (P = 0.095) in eyes with or without prior vitreous surgery. Eyes with macular holes between 2-2.99 years experienced a somewhat better anatomic and functional result overall than eyes with macular hole from 3-14 years, duration, but the visual acuity change was not statistically significant (P = 0.187). There was substantial variability in visual improvement among eyes with successful closure of the chronic macular hole. CONCLUSIONS: Macular holes of > or = 2 years' duration may be more difficult to close successfully than are more recent macular holes, and the visual improvement appears to be less favorable. Many eyes with chronic macular holes in our study gained substantial visual acuity, so vitreous surgery can be considered in selected eyes with chronic macular holes based on visual needs.     

Myelin basic protein is a zinc-binding protein in brain: possible role in myelin compaction

The zinc-binding proteins (ZnBPs) in porcine brain were characterized by the radioactive zinc-blot technique. Three ZnBPs of molecular weights about 53 kDa, 42 kDa, and 21 kDa were identified. The 53 kDa and 42 kDa ZnBPs were found in all subcellular fractions while the 21 kDa ZnBP was mainly associated with particulate fractions. This 21 kDa ZnBP was identified by internal protein sequence data as the myelin basic protein. Further characterization of its electrophoretic properties and cyanogen bromide cleavage pattern with the authentic protein confirmed its identity. The zinc binding properties of myelin basic protein are metal specific, concentration dependent and pH dependent. The zinc binding property is conferred by the histidine residues since modification of these residues by diethyl-pyrocarbonate would abolish this activity. Furthermore, zinc ion was found to potentiate myelin basic protein-induced phospholipid vesicle aggregation. It is likely that zinc plays an important role in myelin compaction by interacting with myelin basic protein.     

Crystalline retinopathy associated with chronic retinal detachment

OBJECTIVE: To describe the presence of crystalline opacities located at the level of the inner retina in patients with chronic retinal detachment. METHODS: We reviewed the clinical records, fundus photographs, and fluorescein angiograms of patients with superficial retinal crystals in the presence of a chronic retinal detachment. RESULTS: Eleven eyes in 11 patients with chronic retinal detachment were found to have these peculiar crystalline opacities on the inner retinal surface. In 5 patients, the crystalline opacities were noted on initial assessment prior to surgery and persisted without change in appearance or number after surgical repair. In 6 eyes, the crystals were not appreciated until after surgical repair of the retinal detachment. The crystals appeared similar in all 11 eyes, were highly refractile, and were located in the posterior pole. Eight of the eyes had retinal detachment associated with retinal dialysis and 6 of these had a history of trauma. There was a definite history of vitreous hemorrhage in 2 eyes. The crystals did not seem to be associated with any visual deficit. CONCLUSIONS: Chronic retinal detachment can be associated with crystals on the inner retinal surface. The cause and composition of these crystals are unknown. They seem to be visually inconsequential and unchanging.     

Synthesis,characterization, and comparative study of conducting polyaniline/lead titanate and polyaniline–dodecylbenzenesulfonic acid/lead titanate composites

To study the effect of a surfactant on the properties of polyaniline (PANI)/metal oxide composites, PANI/lead titanate (PbTiO₃) composites were synthesized with different weight percentages (10, 20, 30, 40, and 50 wt %) of PbTiO₃ in both the absence and presence of dodecylbenzenesulfonic acid (DBSA) by the polymerization of aniline with ammonium persulfate as an initiator. The structural characteristics and stability, surface characteristics, and electric properties of PANI/PbTiO₃ and PANI–DBSA/PbTiO₃ were studied and compared. The interfacial interactions and thermal stability of these composites were characterized with X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and thermogravimetry techniques. The results indicate significant changes in the physicochemical properties of the composites with the incorporation of DBSA. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Oxidation resistance of decorative (Ti,Mg)N coatings deposited by hybrid cathodic arc evaporation-magnetron sputtering process

Titanium-magnesium nitride coatings (Ti,Mg)N were deposited on steels and silicon substrates by hybrid reactive arc evaporation-magnetron sputtering process from cathodic Ti and sputter Mg targets in an argon/nitrogen gas mixture. X-ray diffraction analyses (XRD) of as-deposited coatings with various Mg/Ti atomic ratios gave evidence of a fcc TiN-like structure strongly oriented in the [111] direction. The TiN lattice parameter increases with the addition of Mg resulting from the substitution of Ti atoms by Mg ones. Optical investigations by spectrophotometry revealed that Mg addition to TiN leads to a change in colour from golden through coppery and violet to grey. Nanoindentation measurements showed that increasing Mg content does not alter the hardness of coatings. As-deposited films were annealed in air from 450 to 750 °C with a 100 °C step. XRD and Raman analyses revealed the formation of rutile TiO₂ and MgTiO₃ phases. Secondary neutral mass spectrometry measurements were performed to study the elemental depth profiles after air annealing. A diffusion of Mg atoms towards the film surface was evidenced above 650 °C, leading to the formation of the MgTiO₃ phase. However, thermogravimetric measurements showed that this oxide phase did not protect the films against high temperature oxidation. On the contrary, below 650 °C Mg affords to TiN a beneficial protective effect, able to reduce the oxidation kinetics by half.     

Neuroendocrine responsivity to monoaminergic system probes in generalized social phobia

We examined neuroendocrine correlates of central monoamine function in patients with the generalized type of social phobia compared to healthy volunteers in order to test hypotheses of dopaminergic, noradrenergic, and/or serotonergic dysregulation in patients with this disorder. A double-blind, placebo-controlled, neuropharmacological challenge study was performed using probes for the serotonergic (fenfluramine), dopaminergic (levodopa), and noradrenergic (clonidine) systems. Twenty-one patients with DSM-III-R social phobia (generalized type) and 22 "never mentally ill" volunteers participated in the study after providing informed consent. Patients with social phobia had an augmented cortisol response to fenfluramine administration compared to the volunteers. In contrast, we found that neither the prolactin response to fenfluramine, the growth hormone or norepinephrine response to clonidine, nor the prolactin or eye-blink responses to levodopa, differed between patients with social phobia and healthy volunteers. The findings suggest that patients with social phobia may exhibit selective supersensitivity of serotonergic systems, but that dopaminergic and noradrenergic function appear normal. Further challenge studies with more specific serotonin probes before and after treatment may assist in the clarification of the pathophysiology of social phobia.     

Indirect effect of insulin to suppress endogenous glucose production is dominant, even with hyperglucagonemia

Suppression of endogenous glucose production (EGP) is one of insulin's primary metabolic effects and failure of this action is a major contributor to fasting hyperglycemia of type 2 diabetes mellitus. Classically, insulin was thought to suppress the liver directly, via hyperinsulinemia in the portal vein. Recently, however, we and others have demonstrated that at least part, and possibly most of insulin's action to suppress EGP is normally mediated via an extrahepatic (i.e., indirect) mechanism. We have suggested that this mechanism involves insulin suppression of adipocyte lipolysis, leading to lowered FFA and reduced EGP ("Single Gateway Hypothesis"). Previous studies of the indirect insulin effect from this laboratory were done under conditions of lowered portal glucagon. Because of the possibility that the direct (i.e., portal) effect of insulin may have been underestimated with hypoglucagonemia, these studies examined the relative importance of portal insulin, versus peripheral insulin (administered at one-half the dose to equalize peripheral insulin levels) at four rates of portal glucagon infusion: 0, 0.65 (under-), 1.5 (basal-), and 3.0 ng/kg per min (over-replacement). Portal versus peripheral insulin suppressed steady-state EGP to the same extent (52%), confirming that the primary effect of insulin to suppress EGP is via the peripheral mechanism. This conclusion was maintained regardless of portal glucagonemia, although there was some evidence for an increase in the direct insulin effect at hyperglucagonemia. The indirect effect of insulin is the primary mechanism of steady-state EGP suppression under normal conditions. The direct effect increases with hyperglucagonemia; however, the indirect effect remains predominant even under those conditions.     

The importance of dominant negative effects of amino acid side chain substitution in peptide-MHC molecule interactions and T cell recognition

Previous studies on the role of specific residues of the peptide or MHC molecule in Ag presentation have revealed the sensitivity of this complex system to even small changes in structure. In our study, we have analyzed the effect of amino acid substitution in a major CD4+ T cell determinant (T1) of HIV-1 gp160 on binding and recognition in the context of various E alpha E beta MHC class II molecules. Individual alanine substitutions at all but three positions had little or no negative effect on either MHC binding or recognition by a specific T hybridoma, whereas substitutions with larger side chains often diminished reactivity. A poly-alanine peptide containing only four of the original residues was an effective MHC class II binder and in vivo immunogen, although lacking the ability to stimulate the hybridoma. Replacement of a glutamic acid in T1 with alanine or a size-conservative, uncharged glutamine, but not a negatively charged aspartic acid produced a peptide at least 100-fold more potent than the parent peptide, indicating an inhibitory effect of the negative charge. Conversely, substitution of a glutamic acid for valine at position 29 in the floor of the peptide binding site of the E alpha E beta molecule decreased functional presentation of this peptide by more than 2 logs. However, these two effects of glutamic acid were not complementary and were mediated by distinct mechanisms, as the change in the peptide altered the extent of binding to class II, but the change in the MHC molecule decreased recognition without inhibiting peptide binding. Taken together, the data all suggest the conclusion that changes in side-chains of peptides and MHC molecules affect Ag presentation and T cell stimulation most often by introducing dominant negative or interfering groups that prevent or alter the pattern of binding events primarily mediated by a very limited number of other residues in the Ag or presenting molecule. These results have important implications for understanding the biochemistry of peptide-MHC-TCR interactions and for the possible design of vaccines both more potent and less subject to allele-specific limitations on immunogenicity.     

Finger Seal Solid Modeling Design and Some Solid/Fluid Interaction Considerations

The technology of shaft compliant seals was revolutionized when brush seals first replaced the labyrinth seals at many locations along compressor and turbine shafts. Finger seals present a compliant seal alternative to brush seals and through their geometric configuration bring about the added potential of hydrodynamic lifting and thus non-contacting operational features. Their manufacturing costs are well below those of brush seals and their potential lifting capability, by eliminating the wear factor, increases considerably their life span while making them a preferred embodiment to brush seals. The fingers' compliance allows both axial and radial adjustment to rotor excursions without damage to the integrity or performance of the seal. The work to be presented here concerns design development through numerical simulation of the motion of an assembly of two high pressure (HP) and one low pressure (LP) fingers arranged axially in a staggered configuration and subject to an axial pressure drop. This combination of fingers represents the smallest repetitive basic elemental cell component of a Finger Seal (FS). The numerical 3-D results presented herein were obtained using customized commercial packages. The solid models using ALGOR as the computational engine study the deformations and stresses of the finger(s) and its/their lifting capabilities. The integrated numerical approach coupling the hydrodynamic fluid model (Navier-Stokes based) to the solid fingers deformation and motion (CFD-ACE+ and FEMSTRESS) allows calibration of the floating and sealing capabilities of the FS at the same time. The entire study is aimed at generating reliable design procedures for the parametric design of a finger seal.     

Caustic injury of the oesophagus. Sixteen years experience, and introduction of a new model oesophageal stent

Caustic ingestion can lead to oesophageal stenosis. We studied 251 patients, 205 of whom were children, in a sixteen-year period. Seventeen patients, of whom one was an adult, acquired deep burns in the oesophagus which had to be treated, to prevent the development of oesophageal strictures. These patients were treated with long-term stenting of the oesophagus with specially designed, silicone rubber stents, impregnated with silicone oil 20 cS, designed by one of us (R.N.P.B.) as the only treatment. Of all models, the twin-tube dilator was the most satisfactory. No corticosteroids were administered. Only one patient developed a mild stenosis. It is therefore our opinion that, when life-saving operations are not indicated, twin-tube stenting of the oesophagus is helpful in treating caustic lesions of the oesophagus and will prevent stricture formation. Corticosteroids were not given in this series, and should be abandoned in the treatment of caustic lesions.