Comment on "period doubling of a torus near the ferroelectric phase transition of a KH2PO4 crystal".
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Journal Article↗
Biomedical subjects
J H Yeo
Publications and source records attributed to J H Yeo.
The effects of Pva/chitosan/fibroin (PCF)-blended spongy sheets on wound healing in rats.
The effects of poly vinyl alcohol (PVA)/Chitosan/Fibroin (PCF)-blended sponge on wound healing in rats were investigated. We excised the skin of a rat, including the dermis, approximately 2 x 2 cm in size. The wound was covered with PCF-blended spongy sheets. The spongy sheets absorbed the exudate, and gained flexibility and softness. Histopathological inspection of the wound 12 d later showed an increase of vascular ingrowth and the absence of inflammatory cells. Regeneration of the skin around the wound was faster than that of the control. We also tested wound healing effects of PVA, Chitosan and Fibroin, alone or in various combinations. Wound healing was accelerated in the order of PCF-blended sponge>Chitosan/Fibroin (CF)-blended sponge>Fibroin (F) sponge > PVA/Chitosan-blended sponge (PC) > Chitosan (C) sponge.
Animals↗
Synthesis and antibacterial activities of novel C(7)-catechol-substituted cephalosporins (I).
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Animals↗
Synthesis and antibacterial activities of novel C(7)-catechol-substituted cephalosporins (II).
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Animals↗
Synthesis and antimicrobial activity of novel 3-[(aminopyrimidiniumyl)thio]methyl cephalosporins.
A series of novel cephalosporin compounds which have 3-[(aminopyrimidiniumyl)thio]methyl substituents was synthesized. They show high antimicrobial activity against various bacterial species including Pseudomonas aeruginosa. Structure-activity relationships with various thiopyrimidines, thiopyrimidiniums, bicyclic thiotriazolopyrimidiniums, and bicyclic thioimidazolopyrimidiniums as 3'-substituents were also studied; cephalosporins with quarternized pyrimidinium moieties have better antimicrobial activities than neuteral pyrimidine cephalosporins, and stabilization of the positive charge on the pyrimidinium moieties is essential for better activity. According to semiempirical PM3 calculations, amino and alkylthio substituents on the pyrimidinium rings play a major role in charge stabilization and delocalization.
Cephalosporins↗
Structural analysis of highly oriented poly(p-phenylene-terephthalamide) by 15N solid-state nuclear magnetic resonance.
The structure of an aromatic polyamide, poly(p-phenylene-terephthalamide) (PPTA), was studied in the solid state using 15N nuclear magnetic resonance (NMR) spectroscopy. Spectra of uniaxially aligned molecules placed with the axis of alignment both parallel with and perpendicular to the applied magnetic field were analyzed to yield the orientations of specific molecular bonds with respect to the fiber axis. The 15N chemical shift tensor was characterized by simulating powder pattern spectra of both PPTA and a model compound, benzanilide. Chemical shift and dipolar coupled chemical shift line shapes were calculated through Euler angle transformations from the principal axis system (PAS) reference frame to the fiber axis system (FAS) frame. The orientations of NH and NC' bonds in PPTA are determined as well as the orientational distribution of the PPTA fiber axis. The structural parameters determined for PPTA are compared with those obtained by X-ray diffraction.
Magnetic Resonance Spectroscopy↗
The rate of sulfur hexafluoride escape from a plastic syringe.
Sulfur hexafluoride (SF6) gas is widely used for internal tamponade during retinal reattachment surgery and is commonly injected into the eye from a 10-mL plastic syringe. The rate of diffusion of SF6 out of a plastic syringe has not bee studied. We measured the percentage of SF6 gas in a 10-mL plastic syringe by gas chromatography, confirmed by infrared spectrometry. Measurements were obtained immediately after aspiration, and at 30 s and 10, 15, 60, 90, and 120 minutes, and 18 hours. A marked decrease in SF6 concentration, from 97% at 30 s to 76% at 60 minutes and 2% at 18 hours, was noted. The results were highly reproducible. Sulfur hexafluoride gas should be injected into the patient's eye as soon as possible after aspiration from the tank to ensure accurate concentrations.
Chromatography, Gas↗
Interphotoreceptor retinoid-binding protein levels in subretinal fluid from rhegmatogenous retinal detachment and retinopathy of prematurity.
Interphotoreceptor retinoid-binding protein (IRBP) has been detected qualitatively in subretinal fluid associated with rhegmatogenous retinal detachments. We have used a quantitative enzyme-linked immunosorbent assay to determine the IRBP concentrations in 24 fluid specimens collected at retinal reattachment surgery from 22 patients, and from 17 patients who underwent surgery for retinopathy of prematurity with traction detachment. We observed a wide range of concentrations (1 to 176 micrograms of IRBP per milligram of protein). Higher concentrations were found only in fluid from the more recent rhegmatogenous detachments. The lowest concentrations were detected among fluids drained from under rhegmatogenous detachments ranging from five days' to one year's duration. The IRBP concentration in subretinal fluid showed no correlation with visual outcome and may be influenced by IRBP turnover in the vitreous cavity. Most strikingly, none of the 17 samples from patients with retinopathy of prematurity contained detectable amounts of IRBP.
Adult↗
Photocoagulation to prevent retinal detachment in acute retinal necrosis.
Retinal detachment (RD) occurs in more than 50% of eyes with acute retinal necrosis (ARN) and is the leading cause of visual loss in this syndrome. In order to decrease the incidence of RD in ARN, the authors treated 12 eyes of 10 patients with prophylactic laser photocoagulation. Retinal detachment occurred in two eyes (17%). Over the same time period, seven eyes with ARN did not receive prophylactic laser treatment, most often because of dense vitreous debris, with a 67% rate of RD. Prophylactic photocoagulation treatment should be considered in the management of patients with ARN.
Acute Disease↗
Retinal pigment epithelial tears. Patterns and prognosis.
Increasing experience with the diagnosis of retinal pigment epithelial (RPE) tears has led to expanded recognition and understanding of this clinical entity. The authors report 18 RPE tears followed for an average of 28 months; 16 were associated with age-related macular degeneration and 2 with presumed ocular histoplasmosis syndrome. Retinal pigment epithelial dehiscences fell into four categories: nine spontaneous tears associated with choroidal neovascularization, one tear associated with an RPE detachment without choroidal neovascularization, four iatrogenic tears occurring at krypton treatment of choroidal neovascularization, and four iatrogenic tears developing weeks to months after laser treatment of choroidal neovascularization. Eight patients had a final visual acuity of 20/100 or better, four were 20/200, and six were 20/400 or worse. Photocoagulation, particularly with the use of krypton red laser, may be modified on the basis of possible RPE tear formation. Heightened awareness of the possibility of inducing pigment epithelial rips should improve diagnosis and management of these cases.
Adult↗
Silicone oil in the treatment of complicated retinal detachments.
Silicone oil is now used with increasing frequency to treat cases of complicated retinal detachment (RD). The authors report their results using silicone oil in eyes with RD resulting from proliferative diabetic retinopathy (PDR) or proliferative vitreoretinopathy (PVR). The retina was completely reattached at last examination in 16 (70%) of 23 eyes with PDR and 20 (67%) of 30 eyes with PVR. Final vision of 5/200 or better was obtained in 5 eyes with PDR (22%) and 16 eyes with PVR (53%) (P = 0.0016). Reproliferation of epiretinal membranes occurred in 26% of diabetics and 23% of eyes with PVR. Silicone oil did not cause regression of iris neovascularization. Complications of silicone oil included corneal decompensation, lens opacification, intraocular pressure elevation, and hypotony.
Diabetic Retinopathy↗
Conjunctival pigmentation following pars plana vitrectomy.
A 32-year-old white man developed distinctive episcleral and conjunctival pigmentation surrounding a sclerotomy site 6 weeks after vitrectomy and retinal reattachment surgery. The conjunctival lesion was biopsied during a second operation to remove an epiretinal membrane causing macular pucker. Light and electron microscopic studies demonstrated melanin granules extracellularly and within macrophages.
Adult↗
Intravitreous fibronectin and platelet-derived growth factor. New model for traction retinal detachment.
In proliferative vitreoretinopathy and trauma, traction retinal detachments result from cellular migration into the vitreous cavity with contractile membrane formation. Cleary and Ryan have established the efficacy of intravitreous injection of autologous blood in reproducing this pathologic process in the rabbit eye. It has previously been shown that two serum components, fibronectin and platelet-derived growth factor, stimulate cellular migration. We now show that contractile membranes and traction retinal detachments occur in 72% of rabbit eyes within three weeks following intravitreous injection of fibronectin and platelet-derived growth factor. These results provide a straightforward new model to study the development of intravitreous cellular membranes and traction retinal detachments.
Animals↗
Extension of retinal detachments as a complication of pneumatic retinopexy.
Pneumatic retinopexy is a promising new alternative technique to scleral buckling for the treatment of selected cases of retinal detachment. We describe two cases, however, in which intravitreal gas injection caused further extension of the retinal detachment that in one case led to new macular detachment. This complication of pneumatic retinopexy has not been reported before, to our knowledge, and it may represent a significant limitation to the technique.
Adult↗
Oral colchicine for the treatment of experimental traction retinal detachment.
In proliferative vitreoretinopathy and trauma, long-term reattachment of the retina is often prevented by the formation of contractile cellular membranes on the retinal surface and within the vitreous cavity. Colchicine, a well-documented inhibitor of microtubule assembly, is a potent inhibitor of retinal pigment epithelium cell, astrocyte, and fibroblast proliferation and migration. To study the therapeutic value of orally administered colchicine, we used an experimental animal model in which intravitreally injected platelet-derived growth factor and fibronectin produced traction retinal detachments in rabbits. With oral administration of colchicine, we were able to decrease the incidence and severity of traction retinal detachment from 74% in controls (20 of 27 eyes) to 29.6% in the treated animals (eight of 27 eyes) at five weeks (P less than .0009). These results, and the apparent lack of retinal and systemic toxicity, suggest that oral therapy with colchicine may prove to be of value in the treatment of human disease.
Administration, Oral↗
Acute retinal necrosis syndrome following herpes zoster dermatitis.
The acute retinal necrosis (ARN) syndrome has been recently linked to intraocular infection with one or more members of the herpesvirus family. The authors report two cases of ARN following herpes zoster skin eruptions, and one case following ipsilateral facial nerve palsy (Ramsay Hunt syndrome). Evaluation of serial serum antibody titers against cytomegalovirus (CMV), herpes simplex virus (HSV) (types 1 and 2), and varicella zoster (VZ) virus revealed diagnostic changes for VZ virus alone following the retinitis. Immune precipitation of radiolabeled VZ proteins by these sera followed by gel fractionation yielded radioimmune precipitation profiles characteristic of a recent zoster reactivation. These cases further implicate a central role for VZ virus infection in the etiology of the ARN syndrome.
Acute Disease↗
Potential acuity meter for predicting visual acuity after Nd:YAG posterior capsulotomy.
We studied 30 patients with opacifications of the posterior capsule to determine if the potential acuity meter (PAM) could accurately predict final visual outcome after Nd:YAG discussion. The final visual acuity was within one line of the PAM prediction in 22 of 30 patients (73%), better by two or more lines in seven patients (23%), and worse in one patient (4%) by two lines. Although in thicker capsules the final acuity was occasionally better than the PAM prediction, the rates of false negative and false positive predictions were very low. Mild cystoid macular edema (3 patients), age-related macular degeneration (3 patients), intraocular lens status, and level of initial acuity did not diminish PAM accuracy. The PAM effectively predicts final visual acuity after YAG posterior capsulotomy, when used in a patient, unhurried manner.
Adult↗
Pathologic features of senile macular degeneration.
Senile macular degeneration (SMD) has several morphologic forms that may exist singly or in various combinations. Patients with drusen are at an increased risk to develop SMD. Types of drusen that have been recognized clinically and histopathologically include hard or nodular, soft, glistening or calcified, and diffuse. Hard drusen are probably a consequence of extrusion of material from one or a cluster of retinal pigment epithelial (RPE) cells. Soft drusen are a sign of more widespread disease of the RPE, develop in eyes with hard drusen, and represent small areas of serous detachment of the RPE and the thickened inner aspect of Bruch's membrane. RPE areolar atrophy can occur in the setting of hard and soft drusen and in larger RPE detachments. From the morphologic point of view, we propose that the process leading to disciform scar formation in SMD begins with thickening of the inner aspect of Bruch's membrane due to production of abnormal basement membrane by the RPE. This thickened area is weakly attached and allows the development of localized detachments (soft drusen). These localized detachments become confluent into large detachments of the RPE. Choroidal neovascularization occurs in association with diffuse and soft drusen and larger serous RPE detachments. Bleeding from neovascular tissue leads to disciform scar formation.
Atrophy↗