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Biomedical subjects

A S Patel

Publications and source records attributed to A S Patel.

At least 19 recordsLinked to original sources
PubMed1994

Endogenous Fusarium endophthalmitis in a patient with acute lymphocytic leukemia.

Endogenous fungal endophalmitis is an uncommon complication of systemic mycosis. Only a few cases involving Fusarium have been reported, most with unfavorable visual outcomes. We examined a 31-year-old woman with acute lymphocytic leukemia who developed sudden visual loss in her right eye. A dense, white placoid infiltrate was present in the right macula extending into the vitreous. An iris nodule and hypopyon were present in the left eye. A vitreous aspirate of the right eye was positive for Fusarium species. The patient progressively lost vision despite amphotericin B and 5-fluorocytosine therapy. She died from bronchopneumonia, fungemia, and multisystem failure. Histopathologic study disclosed a panophthalmitis with Fusarium organisms invading all the ocular coats in the right eye. Leukemic infiltrates were present in the left iris, anterior chamber, and trabecular meshwork. The ocular destructiveness of Fusarium may be caused by marked mycotic vascular invasion and occlusion with consequent infarction and necrosis of ocular tissues.

Adult↗
PubMed1993

Water properties of hydrogel contact lens materials: a possible predictive model for corneal desiccation staining.

A set of properties of the water contained within hydrogel contact lens materials was determined with the aim of developing a model which would predict the propensity of a hydrogel contact lens material to induce corneal desiccation staining. We postulated that materials containing a larger proportion of water with the properties of bulk water would tend to induce corneal desiccation more readily than materials with the same overall water content but containing a larger proportion of water that interacts strongly with the polymer. The water structure [as measured by differential scanning calorimetry (DSC)] and the permeabilities of water and glucose were determined for a series of commercial hydrogel lenses. Both glucose permeability and DSC measurements are sensitive indicators of water structure and able to distinguish between various materials. To illustrate the potential of our model, the results of a short-term clinical study are presented. Lower levels of staining were noted for a material with a lower glucose permeability and a larger amount of water melting below 0 degrees C than for a control lens, even though both materials were similar in water content and water permeability. Further clinical studies are needed to validate this model.

Biocompatible Materials↗
PubMed1991

Lipid adsorption onto hydrogel contact lens materials. Advantages of Nile red over oil red O in visualization of lipids.

An artificial tear solution containing the major types of proteins, glycoproteins, and lipids represented in human tears has been developed. The adsorption of lipids onto various hydrogel lens materials (polymacon, lidofilcon A, phemfilcon A, etafilcon A) was examined by exposing the lenses to our artificial tear solution for 18 h. The adsorbed lipids were detected using Nile red stain. The patterns of deposits obtained in vitro were similar to those obtained with human worn lenses. The Nile red stain appeared far more sensitive in detecting lipids adsorbed to hydrogel lenses than the oil red O stain. It was found that lipids adsorb to hydrogel materials quite readily either in a pure state or combined with mucin or other proteins. In view of this work more attention should be given to the role of lipids in the etiology of various contact lens wear complications.

Adsorption↗
PubMed1991

Effect of proteins on water and transport properties of various hydrogel contact lens materials.

The effect of adsorbed substances on the properties of the water in various hydrogel contact lens materials was examined by exposing contact lenses (Hydron Zero 4, B&L 70, DuraSoft 3, Vistamarc, and Acuvue) to an artificial tear solution for various periods up to 14 days. The only materials affected were the high-water/ionic lenses which adsorbed a large amount of protein, predominantly lysozyme. In the DuraSoft 3 lenses the equilibrium water content (EWC) dropped from 49% to 46% and the freezing water from 28% to 21%. Similar changes were seen with the Vistamarc lenses. After a 10-day exposure of the Acuvue lens to artificial tears, the EWC decreased from 53% to 47% and the amount of freezing water from 33% to 23%. The decrease in the permeability of water seen with these materials was consistent with the decrease of the freezing water, i.e., the water able to participate in diffusion. Since the content of freezing water determines the transport through hydrogels it can be expected that any lens characteristics that depend upon the amount of this portion of water would be affected by the presence of proteins inside the polymer matrix. We extrapolated that an absolute change of 10% in the amount of freezing water could lead to a decrease in oxygen permeability of as much as 7 Dk units. In view of this work more attention should be given to changes in the properties of lenses during wear, in particular, in the high-water/ionic lenses.

Adsorption↗
PubMed1989

Acute type A hepatitis presenting with hypotension, bradycardia, and sinus arrest.

The cardiovascular complications of viral hepatitis are not widely recognized. Profound hypotension and a variety of dysrhythmias, including sinus arrest, have been reported in association with viral hepatitis, but most of these cases were described before the advent of specific viral serologic markers. Furthermore, previous instances of cardiovascular complications occurred during the course of an established viral syndrome. We report the cases of two previously healthy women who presented with unexplained hypotension and bradycardia as the initial manifestations of acute icteric hepatitis A. This phenomenon appears to represent a variant clinical presentation of a common viral entity.

Acute Disease↗
PubMed1989

At least two mutant alleles of ornithine delta-aminotransferase cause gyrate atrophy of the choroid and retina in Finns.

Gyrate atrophy of the choroid and retina (GA) is an inherited chorioretinal degeneration caused by deficiency of ornithine delta-aminotransferase (OAT; L-ornithine: 2-oxo-acid aminotransferase; EC 2.6.1.13). GA is one of the "Finnish genetic diseases," a group of several rare monogenic disorders that occur with increased frequency in the Finnish population. Using a combination of RNase A protection, genomic cloning, and polymerase chain reaction amplification of genomic DNA, we found one of two missense mutant OAT alleles to be present in each of 16 Finnish GA pedigrees. The first mutation R180T, in which arginine-180 is replaced by threonine, was present in homozygous form in patients from two pedigrees. The second mutation L402P, in which leucine-402 is replaced by proline, was present in homozygous form in patients from 14 pedigrees. Neither mutation was present in 19 Finnish controls. L402P was not present in 18 non-Finnish GA patients but R180T was found in an American GA patient. We constructed full-length mutant cDNAs by amplifying patient cDNA with the polymerase chain reaction and cloning a restriction fragment containing the mutation into an otherwise normal human OAT cDNA. These mutant cDNAs were then expressed in CHO-K1 cells, which lack endogenous OAT. Both R180T and L402P inactivate OAT. These results show molecular heterogeneity in GA alleles even in the Finnish population.

Alleles↗
PubMed1989

Amebic colitis masquerading as acute inflammatory bowel disease: the role of serology in its diagnosis.

Amebic colitis needs to be considered in the differential diagnosis of infectious colitis or inflammatory bowel disease (IBD). Misdiagnosing amebic colitis as idiopathic inflammatory disease may be fatal. Although stool studies remain the initial approach to diagnosis, the incidence of false-negatives associated with this method is high. We report two cases of amebic colitis presenting as inflammatory bowel disease in which the diagnosis of amebic colitis was made by serology. Neither patient had any risk factors for acquiring amebiasis. Paired serology for amebic infections (2-4 weeks apart) should be performed in patients being evaluated for infectious colitis and inflammatory bowel disease.

Animals↗
PubMed1988

Optimum anesthesia with intrapleural lidocaine during chemical pleurodesis with tetracycline.

Chemical pleurodesis with tetracycline is frequently complicated by pleuritic chest pain. The most promising approach to control pain is to optimize the use of intrapleural lidocaine. While administering amounts of intrapleural lidocaine larger than commonly reported, we attempted to determine a safe and more effective dose, by using a subjective and objective assessment of pain, by measuring serum concentrations of lidocaine, and by observing patients for possible toxic effects of lidocaine. Chemical pleurodesis with tetracycline was performed on ten patients receiving an intrapleural dose of 200 mg of lidocaine (group 1) and on ten patients receiving a 250-mg dose (group 2). A significantly greater number of patients in group 2 were free of pain following pleurodesis (7/10 vs 1/10; p = 0.006). Of the 80 serum lidocaine levels obtained, only one value (6.1 micrograms/ml), in an asymptomatic patient in group 1, exceeded the therapeutic range (1.5 micrograms/ml to 5.5 micrograms/ml). One patient in group 2 experienced transient numbness of the right hand, a possible side effect of lidocaine. We conclude that to achieve optimum anesthesia during chemical pleurodesis with tetracycline, it is necessary to use doses of intrapleural lidocaine large than previously reported. Until the feasibility of a further escalation is demonstrated, 250 mg should be considered the standard dose.

Anesthesia, Local↗
PubMed1987

Synthetic keratophakia for the correction of aphakia.

Although the majority of aphakic patients will have intraocular lens implants (IOLs), there are several groups of patients for whom IOLs are not indicated. Synthetic keratophakia for the correction of aphakia has several inherent advantages over alternative forms of refractive surgery which use lathed corneal tissue. For example, the ability to produce a synthetic lens to precise specifications before surgery is a dramatic advantage over the use of lathed tissue lenses whose refractive properties cannot be determined until weeks or months after the lens is in place on the recipient cornea. Synthetic materials appear to behave in a predictable manner and are biocompatible. Both polysulfones and hydrogel materials can be used to correct aphakia in clinical situations where other modalities are less appropriate.

Animals↗
PubMed1987

Keratoconus in a rhesus monkey.

A 15-year-old female rhesus monkey was observed to have bilaterally thinned and prominently curved corneas. Slit lamp observations, pachymetry, keratometry, and corneoscopy were consistent with a diagnosis of keratoconus, a relatively common corneal dystrophy in humans heretofore not described in a subhuman primate.

Animals↗
PubMed1987

Myopic hydrogel keratophakia. Improvements in lens design.

In order for a refractive surgical procedure to be generally accepted, it must give a predictable result as well as generate a suitable optical surface. Previously, in a non-human primate model, we showed that hydrogel intracorneal lenses could flatten the cornea and thereby be used as a potential treatment for myopia. Over 20 D of central corneal flattening was observed in some cases. It was evident that the major corneal flattening occurred only in a very small area covered by the first corneascopic ring and that this area was irregular in that an elliptical reflection was generally obtained. We herein present the results of myopic hydrogel lens design modification. By enlarging the size of the lens and optical zone, the central corneal flattening became more regular as judged by corneascopic analysis. With the most recent lens designs, animals with high-minus implants showed circular corneascopic images with an average of 10.0 D of central flattening. This observation of corneal flattening was confirmed with autorefractor readings (average, -8.5 D) and keratometric readings (average, -9.0 D). These results are compared with earlier lens implants 5.5 mm in diameter where flattening was documented by reading the central corneascopic ring and could not be confirmed with either keratometric or autorefractor data. We feel these preliminary attempts at lens design modification have significantly enhanced the potential for future clinical application of this technique.

Animals↗