Chemical and electronic properties of Al/
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Journal Article↗
Biomedical subjects
S Chang
Publications and source records attributed to S Chang.
Long-term results of vitrectomy and perfluorocarbon gas for the treatment of severe proliferative vitreoretinopathy.
The results of 87 patients who underwent vitrectomy, scleral buckling, and injection of perfluorocarbon gas in one eye each for proliferative vitreoretinopathy of grade C3 (marked, involving three quadrants) or worse were studied. The retinas of 60 of the 87 patients (69%) were attached posterior to the scleral buckle one month after disappearance of the gas, with the initial reattachment rate being inversely proportional to the severity of proliferative vitreoretinopathy. Follow-up data ranging from six to 106 months were available on 54 eyes with attached retinas. Final visual acuity in those patients ranged from light perception to 20/40 and was not related to severity of proliferative vitreoretinopathy or duration of reattachment. Thirty-eight of the 54 patients (70%) had a visual acuity of 20/400 or better. Twenty-nine of the 37 patients (78%) with retinas attached 24 months or longer had the same or better visual acuity than at six months postoperatively. Macular pucker was observed in 16 of the 54 eyes (30%) and was the most frequently seen long-term retinal complication affecting visual acuity.
Adolescent↗
Tractional elevations of the retina in patients with diabetes.
Tractional retinoschisis and tractional retinal detachment are both complications of proliferative diabetic retinopathy. The two conditions are frequently confused because they are similar in diagnostic features. We determined the respective incidence of tractional retinoschisis and tractional retinal detachment in 200 eyes with tractional elevations of the retina in patients with diabetes. In 39 eyes, the diagnosis was unequivocally tractional retinoschisis because the retinal elevation maintained its concave contour despite the development of retinal holes. In 65 eyes, tractional retinal detachment was diagnosed with equal certainty, either because pigment lines were present or because the elevation, after a retinal hole developed, rapidly became convex and extended to the ora serrata. The remaining 96 eyes, in which retinal holes or pigment lines were absent, were classified by other features that had been tested for significance in the already diagnosed eyes. On that basis, the diagnosis was retinoschisis in 46 eyes and retinal detachment in 50 eyes.
Diabetes Mellitus, Type 1↗
Genetic and molecular analysis of DNA43 and DNA52: two new cell-cycle genes in Saccharomyces cerevisiae.
Two Saccharomyces cerevisiae genes previously unknown to be required for DNA synthesis have been identified by screening a collection of temperature-sensitive mutants. The effects of mutations in DNA43 and DNA52 on the rate of S phase DNA synthesis were detected by monitoring DNA synthesis in synchronous populations that were obtained by isopycnic density centrifugation. dna43-1 and dna52-1 cells undergo cell-cycle arrest at the restrictive temperature (37 degrees C), exhibiting a large-budded terminal phenotype; the nuclei of arrested cells are located at the neck of the bud and have failed to undergo DNA replication. These phenotypes suggest that DNA43 and DNA52 are required for entry into or completion of S phase. DNA43 and DNA52 were cloned by their abilities to suppress the temperature-sensitive lethal phenotypes of dna43-1 and dna52-1 cells, respectively. DNA sequence analysis suggested that DNA43 and DNA52 encode proteins of 59.6 and 80.6 kDa, respectively. Both DNA43 and DNA52 are essential for viability and genetic mapping experiments indicate that they represent previously unidentified genes: DNA43 is located on chromosome IX, 32 cM distal from his5 and DNA52 is located on chromosome IV, 0.9 cM from cdc34.
Amino Acid Sequence↗
Nematode acetylcholinesterases: molecular forms and their potential role in nematode behavior.
Nematode movement is reliant upon the somatic musculature that runs longitudinally along the body wall. Neuromuscular synapses occur in the ventral and dorsal cords and employ the excitatory neurotransmitter, acetylcholine (ACh), for modulation of muscle activity. Acetylcholine activity is terminated by hydrolysis by acetylcholinesterase (AChE). Here, Charles Opperman and Stella Chang discuss the molecular forms and potential role of this enzyme.
Journal Article↗
Production of the cytostatic agent aeroplysinin by the sponge Verongia aerophoba in in vitro culture.
1. The marine sponge Verongia aerophoba contains two bioactive secondary metabolites from tyrosine, (+)-aeroplysinin-1 [3',5'-dibromo-1',2'-dihydroxy-4'- methoxycyclohexa-3',5'-dien-1'-yl-methyl-cyanide; abbreviated AP] and dibromoverongia-quinol [3',5'-dibromo-1'-hydroxy- 4'-oxocyclohexa-2',5'-dien-1'-yl-acetamide; abbreviated DV], which display strong cytostatic activity. 2. The concentrations causing 50% inhibition of cell growth are 0.47 microM (AP) and 1.21 microM (DV), resp. 3. Depending on depth regions from which the sponges were collected, differences in occurrence of metabolites were observed. 4. AP and DV were found to be present in sponges collected at a depth of 5-10 m, whereas only DV could be detected in material from deeper regions (20-30 m). 5. AP is present only in the surface layers (both the outer and oscular region) of the sponge, while in the centre of the sponge only DV is detected. 6. Cubes from sponges, collected at a depth of 30 m, were cultivated in seawater in vitro and were found to have the capacity (i) to synthesize AP, and (ii) to release this bioactive material into the medium under defined conditions. Under optimal conditions (light and aeration) 100 g of sponge synthesize and release 13.02 mg of AP during a 10-day incubation period. 7. In the dark and without aeration this synthesis was prevented. 8. These data show that also under in vitro conditions sponges retain the capability of producing bioactive compounds and can be induced to produce even substances which they did not secrete in their natural environment.
Acetamides↗
Iris neovascularization in proliferative vitreoretinopathy.
PURPOSE: The purpose of this study is to report on the prevalence, incidence, and associated risk factors of iris neovascularization in nondiabetic patients undergoing vitrectomy for retinal detachment complicated by proliferative vitreoretinopathy (PVR). METHODS: The authors conducted a retrospective review of 141 consecutive non-diabetic patients undergoing vitrectomy for recurrent retinal detachment resulting from PVR. Univariate and multivariate analyses were performed on all patients to determine which preoperative, intraoperative, and postoperative factors were associated with the development of postoperative iris neovascularization. RESULTS: Twenty-seven of the 141 (19%) patients were noted with preoperative and/or postoperative iris neovascularization. Four of eight patients presenting with preoperative iris neovascularization had complete regression after successful reattachment of the retina. Results of analysis of the remaining 133 patients without iris neovascularization preoperatively showed residual retinal detachment as the most significant risk factor for postoperative iris neovascularization. In the absence of panretinal photocoagulation, none of the 27 patients developed neovascular glaucoma. CONCLUSIONS: The development of iris neovascularization preoperatively or post-operatively is not necessarily a predictor of a poor anatomic and/or visual result. Iris neovascularization in PVR rarely if ever progresses to neovascular glaucoma. Panretinal photocoagulation is not indicated in these patients. Retinal reattachment is the most important factor in the prevention and/or resolution of postoperative iris neovascularization. The development of iris neovascularization in PVR appears to be a multifactorial process requiring multiple variables acting in concert.
Adolescent↗
CTL cross reactivity between HIV strains.
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Antigenic Variation↗
Perfluorocarbon liquids in vitreoretinal surgery.
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Eye Injuries, Penetrating↗
Experimental studies of the combined use of vitreous substitutes of high and low specific gravity.
The combined use of high and low specific gravity liquid vitreous substitutes has been studied in the rabbit. Eyes having undergone 1) vitreous replacement with silicone liquid combined with a perfluoropolyether liquid of high viscosity; 2) replacement with the perfluoropolyether or silicone alone; or 3) vitrectomy only (control) were compared under conditions of a cell-injection model of traction retinal detachment. Some of the control eyes (3 out of 9) and silicone-filled eyes (2 out of 10) developed total retinal detachments involving all quadrants; in the silicone-filled eyes the detachments extended behind the silicone globule. Conversely, in the eyes undergoing replacement with the two liquids or with the perfluoropolyether liquid alone, retinal detachments never extended to the inferior quadrants underlying the perfluoropolyether globule. In other experiments, the tendency toward emulsification of a low-viscosity perfluorocarbon liquid was reduced when it was used in combination with silicone liquid, in comparison to when this liquid was used alone.
Animals↗
Treatment of dislocated crystalline lens and retinal detachment with perfluorocarbon liquids.
Removal of a crystalline lens dislocated into the vitreous cavity can be hazardous, particularly in the presence of a retinal detachment. Hard pieces of nuclear material may be difficult to extract and may repeatedly fall onto the retina when emulsification is attempted in the vitreous cavity. Cases involving four eyes with dislocated crystalline lens and rhegmatogenous retinal detachment, into which liquid perfluorocarbon was injected after vitrectomy to float the dislocated lens material off the retina and reattach the retina, are reported. The dislocated lens was removed while floating on the perfluorocarbon liquid, which also provided a cushion that prevented dropped fragments of lens from traumatizing the retina. In all four cases, surgery was not associated with complications and resulted in improvement in visual acuity and retinal reattachment.
Adult↗
Evaluation of the blood-aqueous barrier after vitreous replacement with perfluoropropane gas and liquid silicone.
Fluorophotometric measurements of blood-aqueous barrier permeability after intravitreal injection of perfluoropropane gas in rabbit eyes revealed fluorescein leakage immediately after injection; 3 days later, recovery of barrier integrity had begun to occur and 7 days and 14 days after gas injection, when the gas bubble was still in the eye, anterior chamber fluorescein concentrations were normal. Similarly, in eyes undergoing vitrectomy and injection of silicone liquid or vitrectomy only, anterior chamber fluorescein levels were elevated 3 days and 1 week after surgery. Nevertheless, normal barrier integrity was reestablished in both the silicone-filled eyes and the vitrectomized eyes after 1 week. Since there was no difference between the group injected with silicone and the group that underwent vitrectomy only with respect to anterior chamber fluorescein concentration at any of the times studied, it is concluded that the temporary disruption of the blood-aqueous barrier is associated with the surgical procedure rather than the presence of silicone liquid in the vitreous cavity.
Animals↗
A statistical model based fundamental frequency synthesizer for Mandarin speech.
A novel method based on a statistical model for the fundamental-frequency (F0) synthesis in Mandarin text-to-speech is proposed. Specifically, a statistical model is employed to determine the relationship between F0 contour patterns of syllables and linguistic features representing the context. Parameters of the model were empirically estimated from a large training set of sentential utterances. Phonologic rules are then automatically deduced through the training process and implicitly memorized in the model. In the synthesis process, contextual features are extracted from a given input text, and the best estimates of F0 contour patterns of syllable are then found by a Viterbi algorithm using the well-trained model. This method can be regarded as employing a stochastic grammar to reduce the number of candidates of F0 contour pattern at each decision point of synthesis. Although linguistic features on various levels of input text can be incorporated into the model, only some relevant contextual features extracted from neighboring syllables were used in this study. Performance of this method was examined by simulation using a database composed of nine repetitions of 112 declarative sentential utterances of the same text, all spoken by a single speaker. By closely examining the well-trained model, some evidence was found to show that the declination effect as well as several sandhi rules are implicitly contained in the model. Experimental results show that 77.56% of synthesized F0 contours coincide with the VQ-quantized counterpart of the original natural speech. Naturalness of the synthesized speech was confirmed by an informal listening test.
China↗
Pathfinding by cranial nerve VII (facial) motorneurons in the chick hindbrain.
Cranial nerve VII (facial) motorneurons begin extending axons through rhombomeres 4 and 5 (R4 and R5) in the chick hindbrain on the second day of incubation. Without crossing the midline, facial motorneuron axons extend laterally from a ventromedial cell body location. All facial motorneuron axons leave the hindbrain through a discrete exit site in R4. To examine the importance of the exit site in R4 on motorneuron pathfinding, we ablated R4 before motorneuron axonogenesis. We find that mechanisms intrinsic to R5 direct the initial lateral orientation of R5 motorneuron axons. Upon reaching a particular lateral position, all R5 motorneuron axons must turn. In normal embryos the axons all turn rostrally to reach the nerve exit in R4. In embryos with R4 ablated, sometimes the axons turn rostrally and sometimes they turn caudally. A model combining permissive fields and chemotropic cues is presented to account for our observations.
Animals↗
Department of pharmacy-initiated program for streamlining empirical antibiotic therapy.
The outcome of a department of pharmacy-initiated "streamlining" study designed to promote cost-conscious modifications of empirically selected antibiotic therapy is described. Two hundred forty-one evaluable adult patients started on restricted-use antibiotics at this university-affiliated community private teaching hospital were enrolled in a 9-week prospective streamlining study. Patients were alternately assigned to a Control (i.e., no pharmacist-initiated streamlining recommendations offered based on culture and susceptibility reports) or a Pharmacist Intervention group (i.e., pharmacist offers recommendations to streamline therapy). A statistically significant greater number of patients had their empiric antibiotic treatment courses modified to more appropriate antibiotic choices after receipt of culture and susceptibility reports among private prescribers in the Pharmacist Intervention group (83%) than in the Control group (38%) (p = .006). Additionally, pharmacists were overall successful in gaining prescriber acceptance for 64% of recommended changes of empiric antibiotic treatment courses before the receipt of culture and susceptibility reports (e.g., dose and/or frequency changes). There was no program effect observed with respect to improved physician response to microbiologic data that would allow streamlining empirical antibiotic choices in the Housestaff (i.e., medical or surgical residents), or infectious disease consultant prescriber groups. Projected overall annual cost savings that would be achieved as a result of continued efforts by pharmacists directed at streamlining empirical "restricted" antibiotic regimens is approximately +40,000.
Analysis of Variance↗
Posterior chamber IOL implantation in traumatic cataract with injured complications.
Twenty-five cases of posterior chamber IOL implantation in traumatic cataract with complications associated with primary injury were reported. The operating methods were described and the post-operative complications were discussed. Seventy-two percent of patients have the correct vision over 20/40. It is suggested that the posterior chamber IOL can be implanted in traumatic cataract with some injured complications.
Adolescent↗
The effects of lipid lowering on diabetic retinopathy.
The effect of lipid lowering on hard exudates was determined in six consecutive patients with insulin-dependent diabetes mellitus. Diet and hypolipidemic drug therapy including the use of pravastatin, a new inhibitor of 3-hydroxy-3-methylglutaryl coenzyme-A reductase, were used to treat patients for one year. The total cholesterol concentration decreased from a mean baseline value of 231 mg/dl to a treatment mean value of 165 mg/dl. The mean low-density lipoprotein cholesterol concentration decreased from 157 mg/dl to 93 mg/dl. Masked grading of fundus photographs indicated an improvement in hard exudates in all six patients and a decrease in microaneurysms in four patients. Visual acuity improved in one patient and did not change (one line or less change) in five patients. No remarkable side effects resulting from treatment were observed. Our pilot study suggests that aggressive therapy of diabetic patients with hyperlipidemia may have a beneficial effect on background retinopathy.
Adult↗
Correlation of deep-level and chemically-active-site densities at vicinal GaAs(100)-Al interfaces.
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Journal Article↗