Biomedical subjects
Publications and source records attributed to M T Coroneo.
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OBJECTIVE: To assess the role of intravitreal administration of high doses of ganciclovir as a supplement and alternative to intravenous administration in the treatment of cytomegalovirus (CMV) retinitis in patients with acquired immunodeficiency syndrome (AIDS). DESIGN: A retrospective study of visual outcome, relapse and complications of intravenous and high dose intravitreal administration of ganciclovir alone and in combination. METHOD: Twenty-three patients with AIDS and CMV retinitis (37 eyes) were examined by the authors and notes, fundal drawings and photographs reviewed. Initially patients were treated with intravenous ganciclovir alone and given supplementary intravitreal therapy for relapse or vision-threatening retinitis; however, later patients were managed with combination maintenance ganciclovir or maintenance intravitreal treatment alone. RESULTS: Relapse and loss of vision occurred frequently in patients treated with intravenous ganciclovir alone or in combination with intermittent intravitreal therapy. Eyes managed with maintenance high dose intravitreal ganciclovir alone or in combination with intravenous treatment did not relapse or lose vision. The most important complication of intravenous administration of ganciclovir was neutropenia (73% of patients), whereas that of intravitreal therapy was endophthalmitis (three eyes). CONCLUSION: High dose ganciclovir given intravitreally effectively suppressed CMV retinitis and preserved vision without adverse systemic effects or deterioration of quality of life.
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I describe a safe, easily learned, accessible, and inexpensive method for excision of the pterygium head using the tip of a 23-gauge needle as a cutting tool. The incision is controlled precisely, and excision of unaffected tissue, particularly at the limbus, is minimized by using point cutting edge techniques and by varying tissue tension to control tissue sectility ("cuttability").
Although trabecular meshwork cells are presumed to play an important role in determining ocular aqueous outflow resistance, little is known about their membrane transport characteristics. As in vivo access by microelectrodes is difficult, we used cell culture techniques to facilitate membrane voltage recording from cultured bovine trabecular meshwork cells. Phase-contrast microscopy revealed the presence of epithelial-like and spindle-shaped cell types. The mean membrane voltage for epithelial cells was -49.7 +/- 0.8 mV (S.E.M., n = 143) and for spindle cells was -70.9 +/- 1.9 mV (S.E.M., n = 48). These cells possess an electrogenic Na+/K(+)-ATPase and a K+ conductance. K transference numbers (tk) for [K+] from 5 to 80 mM were 0.50 for epithelial cells and 0.71 for spindle cells. The epithelial cells lack the electrogenic Na+/HCO3-symport, thereby enabling their differentiation from corneal endothelial cells and confirming previous reports of differences between these cell types. A proportion of spindle cells demonstrated spontaneous and induced fluctuations of membrane voltage. One millimolar Ba2+ (n = 9) induced an immediate depolarization of membrane voltage, with the onset of 'overshooting' action potentials, which were dependent on extracellular Ca2+ and Na+ but were not blocked by tetrodotoxin, 10(-6) M. Spindle cells showed parallel alignment of intracellular smooth muscle specific alpha-isoactin filaments, whereas epithelial cells showed specks of non-fibrous staining. Electron microscopy revealed that epithelial cells had the characteristics of metabolically active cells, with few intermediate filaments (10-12 nm) and microfilaments (6-7 nm) and short cytoplasmic processes. Spindle cells had long cytoplasmic processes and abundant intermediate- and microfilaments. These data provide further evidence for multiple bovine trabecular cell types. The smooth muscle-like spindle cell may represent the previously proposed contractile element of the angle and its action could conceivably alter ocular outflow resistance.
Peripheral focusing of light by the anterior eye may provide a unifying concept to explain the location and etiology of sun-related eye conditions (ophthalmohelioses). Using a bovine eye model, along with computer-assisted ray-tracing techniques to model limbal focusing, we demonstrated a correlation between the locations of the foci of scattered incident light (resulting in a 20-fold concentration of light at the limbus) and the usual locations of pterygium and cortical cataract. These findings suggest the need for improved ocular protective devices, particularly ones that provide lateral protection of the eye against the increased ultraviolet insolation resulting from thinning of the ozone layer.
A simple method for preparing the bovine eye as an in vitro model for training cataract surgeons is described and illustrated. This model allows basic skills to be gained in a graded fashion, using readily available materials. Also, more advanced surgical techniques can be refined by using this model. Manipulation of the model enables mimicking of real-life surgical challenges. Use of bovine eyes may represent, in bioethical terms, efficient use of available biological materials.
I describe concentrations of reflected solar radiation (albedo) found at the usual sites of various conditions associated with exposure to the sun--pterygium, pinguecula, climatic droplet keratopathy and cataract and eyelid malignancy. Since the degree of limbal albedo concentration appears to be related to corneal curvature, patients at risk can be identified by a simple test and preventative measures taken.
Human nonpigmented ciliary epithelial cells (NPE) were grown in tissue culture after transformation with an origin-defective mutant of SV-40 DNA. In these cells membrane potentials (V) were measured using the microelectrode technique. Addition of 10(-4) M acetylcholine led to a bisphasic voltage response. An immediate, transient hyperpolarization was followed by a sustained depolarization below the steady state level. These responses were irreversibly blocked by 10(-5) M atropine. In Ca2+-free media the initial addition of acetylcholine resulted in an unchanged voltage response. A second application of acetylcholine in Ca2+-free solution evoked only an abortive response of V, and further addition had no effect on V. In the presence of Ca2+ channel blockers (10(-5) M verapamil, 1 mM Co2+) the acetylcholine-induced response of the membrane potential was not changed. The initial hyperpolarization induced by acetylcholine was reduced by 33 +/- 3% (n = 6) in the presence of 2 mM Ba2+ and by 79 +/- 6% (n = 6) in the presence of 1 mM quinidine. Moreover, the amplitude of the hyperpolarization was dependent on the extracellular K+ concentration. With increasing extracellular K+ concentration (and decreasing transmembrane K+ gradient) the acetylcholine-induced hyperpolarization was reduced. To further elucidate the role of Ca2+ in the acetylcholine-induced responses, we measured cytoplasmic Ca2+ activity using the fluorescence of intracellularly trapped Fura-2. Cytoplasmic Ca2+ activity increased immediately and transiently upon addition of acetylcholine. We conclude that acetylcholine transiently hyperpolarizes V in cultured human NPE by activation of K+ channels mediated by mobilization of Ca2+ from intracellular stores.
The effects of hypotonicity on cultured bovine corneal endothelial cells were investigated using standard microelectrode and superfusion techniques. Confluent monolayers of cells were superfused with an isotonic (305 +/- 5 mosm/kg) control solution until a stable membrane voltage (V) was obtained, then with a hypotonic (240 +/- 5 mosm/kg) solution. Under control conditions, V was - 51.4 +/- 0.8 mV (means +/- SEM, n = 154). Decreasing solution osmolality resulted in an immediate depolarization: mean maximal delta V = 18.7 +/- 0.9 mV at 2.6 +/- 0.2 minutes with a gradual recovery to a new but still depolarized steady-state V (delta v = 11.1 +/- 0.9 mV at 8.2 +/- 0.3 minutes, n = 25). The depolarizing response to hypotonicity persisted in the presence of amiloride (10(-3)M), DIDS (10(-3)M), bumetanide (10(-4)M) or ouabain (10(-4)M) as well as in the absence of extracellular Cl-, Na+, HCO3- or Ca2+. Relative K+ conductance was estimated by the effect on V of increased extracellular [K+] - this was significantly reduced at 5, 10 and 20 mM K+ under hypotonic conditions. The depolarization induced by 1mM Ba2+ was also reduced from 19.6 +/- 0.5 mV (n = 8) under isotonic conditions to 15.4 +/- 0.4 mV (n = 6) under hypotonic conditions (p less than 0.001). The conductive HCO3- pathway - as judged by the hyperpolarization of V induced by increasing extracellular [HCO3-] from 28 to 60 mM, was also reduced under hypotonic conditions (delta V = 17.2 +/- 0.8 mV, n = 13 (isotonic) compared to delta V = 9.5 +/- 0.3 mV, n = 15 (hypotonic].(ABSTRACT TRUNCATED AT 250 WORDS)
Pathologic myopia is a relatively common blinding condition for which current treatment is limited and controversial. Macular changes and vision loss proceed from the development of a posterior staphyloma. A scleral reinforcement technique has been used in seven eyes of six patients. The procedure is technically uncomplicated and safe.
Indoor cricket has become a popular form of recreation in Australia. Four cases of significant ocular trauma in indoor cricketers are reported. Three of the patients had diminished visual acuity in at least one eye before their injury. One patient may suffer long-term consequences as a result of his injuries. These injuries could probably have been prevented by the use of appropriate eye protection. Indoor cricketers might well be advised to undergo ocular assessment before taking up this sport.
The effect of physalaemin, an undecapeptide belonging to a family known collectively as the tachykinins, on water and electrolyte excretion of the mandibular and sublingual salivary glands of the rat has been investigated and compared to that of acetylcholine. Drugs were administered intravenously or by close-arterial infusion. Physalaemin is a powerful stimulant of fluid secretion by both glands although less potent than acetylcholine. The Na and K excretion patterns in physalaemin-evoked saliva resembled, but were by no means identical to those evoked by acetylcholine and other parasympathomimetic drugs: saliva evoked by physalaemin was considerably poorer in Na and K at all secretory rates. The HCO3 excretion curves, on the other hand, seemed to be identical to those evoked by parasympathomimetic drugs. From an analysis of the Na and K excretion patterns, it can be concluded, both for the mandibular and the sublingual glands, that physalaemin stimulated Na reabsorption and K secretion across the gland duct epitheluim, whereas acetylcholine has the opposite effect. These findings agree nicely with what has previously been demonstrated in vitro in the isolated perfused main excretory duct of the rat mandibular gland.
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By the development of a disc-electrode and of an electrically neutral calcium carrier a precise determination of calcium ions in the parotid saliva has become available. With this new and simple method an exponential flow rate dependance of the concentration of calcium ions was found in normal persons. A steady state was observed in higher flow rates than 0.5 ml/min. The ionized/total calcium ratio was 54% in the average and was not influenced significantly by the flow rate. The values of both the ionized and total calcium concentrations were slightly lower in females than in men. The salivary ionized calcium concentration was significantly reduced in patients with arterial hypertension, and was not influenced by the flow rate. Its percentage against total calcium was 42% and was reduced to 39% by increased flow rates.
A simple clinical method for detecting the presence of unilateral proptosis or enophthalmos is described. It is important that in a patient with orbital disease, a detailed ophthalmic and orbital history be taken and a careful clinical evaluation be performed. In the clinical assessment of such a patient, it is also essential to determine the presence of any asymmetry of eye position after excluding any asymmetry in eye size or in the skeletal structure of the face. Observation of the patient's head from above and noting the relative positions of the two eyes has been the traditional method in the clinical assessment of proptosis. We believe that this method of assessment of proptosis has not been adequately described or fully exploited in the past. This paper describes an extension of the same technique. It involves the examiner making the observation from above while slowly moving the patient's head passively from a position of neck flexion to one of neck extension, and then noting which eye in a patient comes into view first. We believe that this kinetic technique provides an accurate method of noting any asymmetry in eye position in relation to the supraciliary ridge. It should therefore prove to be a clinically useful method in the initial assessment of a patient with suspected ocular displacement.