Biomedical subjects
Publications and source records attributed to H Buettner.
We studied four histologically verified cases of isolated neurofibromas of the conjunctiva. The histologic pattern was diffuse in two patients, plexiform in one patient, and solitary in one patient. Simple excision was curative in all cases. We emphasize the importance of distinguishing neuromas (which may be associated with multiple endocrine neoplasia) from neurofibromas.
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Retinal arteriovenous communications proximal to extensive areas of complete vascular closure developed in three patients with occlusive disease of the carotid arteries. In one case, the authors document the development of the arteriovenous communications through successive enlargement of small retinal vessels after progressive signs of retinal ischemia in the form of narrowed retinal arteries, venous dilation and beading, microaneurysms, retinal dot and blot hemorrhages, cotton-wool spots, and capillary nonperfusion. The development of arteriovenous communications in carotid occlusive disease has not been described previously.
Neovascularization of the disc (NVD) was present in 9 of 163 patients with pars planitis. In all cases, NVD was unilateral and observed in eyes with recent exacerbation of the inflammatory process. To reduce intraocular inflammation, all nine eyes were treated with varying combinations of topical, periocular, and systemic corticosteroids. In addition to corticosteroids, one eye received Argon laser photocoagulation, two eyes underwent peripheral cryotherapy, and one eye was treated with both Argon laser photocoagulation and peripheral cryotherapy. With decrease or disappearance of intraocular inflammation, NVD resolved in all cases without recurrence during follow-up study, which ranged from 6 to 189 (mean, 81) months. Rhegmatogenous retinal detachments developed in two eyes treated with peripheral cryotherapy. Both detachments were successfully repaired with surgery. Control of intraocular inflammation appears to be the key factor for regression of NVD in pars planitis. If NVD does not regress or vitreous hemorrhage occur, photocoagulation and peripheral cryotherapy may be beneficial.
The effects of methylenecyclopropylglycine (MCPG), the lower homologue of hypoglycin A, on starved rats are described. Upon oral ingestion of MCPG (43 mg/kg), a 50% decrease in blood glucose compared with controls was observed after 4 h. The plasma concentrations of lactate and non-esterified fatty acids were substantially increased during this period. The activity of general acyl-CoA dehydrogenase from isolated rat liver mitochondria was not significantly changed. By contrast, the activity of 2-methyl-(branched-chain)-acyl-CoA dehydrogenase decreased by over 80%. The enzyme activity of enoyl-CoA hydratase (crotonase) from pig kidneys decreased by 80% on incubation with the hypothetically toxic metabolite of MCPG, methylenecyclopropylformyl-CoA. These results suggest that the inhibition spectrum of MCPG is quite different from that of hypoglycin A and that similar physiological effects might result from inhibition of different enzymes of beta-oxidation, e.g. hypoglycaemia and lacticacidemia. Accumulation of medium-chain acyl-CoA thioesters is probably at the origin of disturbances in pyruvate metabolism.
A 30 year old white woman presented at term with vaginal bleeding, dizziness and blurred vision due to bilateral serous retinal detachments. Extensive areas of choroidal occlusion with focal leakage of dye from the posterior retinal pigment epithelium and choroid were demonstrated by fluorescein angiography. With the diagnosis of abruptio placentae, a dead fetus and disseminated intravascular coagulation (DIC) the patient underwent removal of the uterine contents by cesarean section. DIC and retinal detachments resolved with improvement of vision, DIC, frequently observed in obstetric complications, has a tendency to occlude the posterior choroidal vessels, which often results in serous retinal detachments. In the setting of pregnancy, especially complicated late pregnancy, the occurrence of serous retinal detachments may be an early ocular sign of DIC.
Thirty-six pars plana vitrectomies were performed on 30 eyes of 17 patients with biopsy-proven vitreous amyloidosis. Reopacification of the retrolental vitreous was the most common reason for vitrectomy revision, required in 24% of patients. Complications of amyloid or vitrectomy included retinal detachment requiring scleral buckling in 17% of eyes and glaucoma requiring filtering surgery in 17% of eyes. After a mean 35-month post-vitrectomy follow-up, 48% of eyes had visual acuities of 20/40 or better, and 32% of eyes had visual acuities between 20/50 and 20/100. Twenty percent of eyes had visual acuities of 20/200 or worse due either to persistent retinal detachment, open angle glaucoma, or residual opacification of the vitreous.
The flavoprotein medium-chain acyl coenzyme A (acyl-CoA) dehydrogenase from pig kidney exhibits an intrinsic hydratase activity toward crotonyl-CoA yielding L-3-hydroxybutyryl-CoA. The maximal turnover number of about 0.5 min-1 is 500-1000-fold slower than the dehydrogenation of butyryl-CoA using electron-transferring flavoprotein as terminal acceptor. trans-2-Octenoyl- and trans-2-hexadecenoyl-CoA are not hydrated significantly. Hydration is not due to contamination with the short-chain enoyl-CoA hydratase crotonase. Several lines of evidence suggest that hydration and dehydrogenation reactions probably utilize the same active site. These two activities are coordinately inhibited by 2-octynoyl-CoA and (methylenecyclopropyl)acetyl-CoA [whose targets are the protein and flavin adenine dinucleotide (FAD) moieties of the dehydrogenase, respectively]. The hydration of crotonyl-CoA is severely inhibited by octanoyl-CoA, a good substrate of the dehydrogenase. The apoenzyme is inactive as a hydratase but recovers activity on the addition of FAD. Compared with the hydratase activity of the native enzyme, the 8-fluoro-FAD enzyme exhibits a roughly 2-fold increased activity, whereas the 5-deaza-FAD dehydrogenase is only 20% as active. A mechanism for this unanticipated secondary activity of the acyl-CoA dehydrogenase is suggested.
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Ocular involvement in patients with systemic lupus erythematosus (SLE) is most commonly noted in the form of retinal hemorrhage, exudates and cotton wool spots resulting from occlusion of small retinal blood vessels. Less frequently, SLE is associated with extensive obliteration of larger retinal vessels, as demonstrated in the 2 cases reported here. In both cases large parts of the retina lost their function due to extensive occlusions of retinal arteries and veins. Marked retinal neovascularizations developed in one of the 2 cases. Awareness and early detection of retinal vascular occlusive disease and its complications are important in averting serious visual loss in SLE.
A patient had a 12-year history of relapsing disseminated histoplasmosis. None of the characteristic lesions of the presumed ocular histoplasmosis syndrome were present in either eye. Ocular involvement began as a peripheral focal retinitis associated with vitreitis and iritis. Histoplasma capsulatum organisms grew in cultures from aqueous and vitreous and were demonstrated histologically in an iridectomy specimen. Despite intraocular and subconjunctival administration of amphotericin B, intractable pain associated with progressive necrotizing granulomatous iridocyclitis necessitated enucleation. Histoplasma capsulatum organisms were seen extracellularly in the vitreous cavity and both intracellularly and extracellularly in areas of granulomatous inflammation involving the iris, ciliary body (diffusely), and the retina (focally). The choroid was not involved.
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A 27-year-old white woman with anorexia, abdominal pain, arthralgias, spiking fever, diarrhea, and bizarre neurologic symptoms developed yellowish-gray plaques surrounded by hemorrhage in the posterior choroid of both eyes. Progressive thrombocytopenia, hypofibrinoginemia, and accelerated fibrinolysis supported the diagnosis of disseminated intravascular coagulation (DIC). Death occurred from complications of DIC. Widespread thrombotic occlusion of small blood vessels was present in numerous organs, including the posterior choriocapillaris and larger choroidal vessels of both eyes. Other ocular vessels were normal.
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Endothelial cell density and thickness of the cornea do not appear to be affected by long-standing diabetes mellitus. Standard intra- or extracapsular cataract surgery results in a statistically significant reduction of endothelial cell density, but not in a long-term change of corneal thickness. Endothelial cell loss after trans pars plana surgery averages 8.5%. Differences in endothelial cell loss between phakic eyes of diabetics and phakic and aphakic eyes of nondiabetics subjected to lens removal and/or vitrectomy are not statistically significant. Corneal thickness is increased to a statistically significant degree in all eyes after trans pars plana surgery. Although the cornea in diabetics requires more time to recover after trans pars plana surgery, we found no evidence that it suffers significantly more damage than the cornea in nondiabetics.
In our animal model, silastic scleral sponges retained bactericidal levels of neomycin sulfate for at least 1 week, when thoroughly infiltrated prior to episcleral placement. This would provide an effective protection against acute buckle infections caused by bacteria contaminating the surgical field. Our clinical experience in 1,081 consecutive scleral buckling procedures substantiates the validity of this conclusion.