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Biomedical subjects

L T Chylack

Publications and source records attributed to L T Chylack.

At least 19 recordsLinked to original sources
PubMed1992

Indirect spectral transmission ratio measurements of the aging crystalline lens nucleus.

A new objective approach to characterize color and opalescence in the lens nucleus, using wavelength indexed transmission ratios (TR) is described. Transmission ratios, i.e. the transmissivity per unit lens thickness, for the whole visible spectral range (390-720 nm) were calculated using fast scanning spectral colorimetry (FSSC). The lowest transmission ratios values were obtained in the blue part of the spectrum in general and at 450 nm in particular. They inversely followed the subjectively determined LOCS II color grading. The difference between transmission ratios at the absorbed part of the spectrum (less than 500 nm) and the non-absorbed part (greater than 550 nm) also reflects the LOCS II color grading. The overall mean transmission ratios for all wavelengths in the spectrum gives an index that closely followed the nuclear opalescence grading of the LOCS II system. The transmission ratios are theoretically independent of the spectral characteristics of the incident light as long as it contains suprathreshold energies in the whole measured spectral range.

Absorption↗
PubMed1979

Posterior subcapsular cataracts: histopathologic study of steroid-associated cataracts.

Long-term steroid therapy is associated with production of a posterior subcapsular cataract (PSC). Five steroid-associated cataractous lenses were studied, using light, scanning, and transmission electron microscopy. Anterior, equatorial, and posterior regions were examined. Findings were compared with five age-matched senile PSCs and five nuclear cataractous lenses with no cortical opacities. The posterior polar region of steroid-associated cataractous lenses consists of (1) a superficial zone of liquefaction and (2) a deep zone of segmentally swollen lens fibers. Nucleated lens fibers are present in posterior cortical regions. Cytoplasm at knob and socket junctions had become lucent and plasma membranes were disappearing, leaving empty spaces. Laminated membranous configurations were seen. Although the same basic histopathologic abnormalities were found in steroid-associated cataracts and in nonsteroid senile PSCs, it is their organization and localization that may be the distinguishing characteristics of the steroid-associated cataract.

Adrenal Cortex Hormones↗
PubMed1979

Choroidal effusion during glaucoma surgery in patients with prominent episcleral vessels.

Rapid intraoperative choroidal effusion and flattening of the anterior chamber occurred during glaucoma filtering surgery in four young patients with prominent episcleral vessels, elevated episcleral venous pressure, and advanced open-angle glaucoma. Two of these four patients had Sturge-Weber syndrome. Intraoperative release of suprachoroidal fluid (SCF) through a posterior sclerotomy facilitated reformation of the anterior chamber and repositioning of the iris and ciliary body. Posterior sclerostomy performed prior to opening the anterior chamber minimized the above-mentioned untoward series of events. Analysis of SCF and serum demonstrated considerable differences in total protein and individual immunoglobulin levels; this appears to be a manifestation of molecular sieving at the level of the choriocapillaris. Choroidal detachment and postoperative serous retinal detachment are manifestation of this phenomenon.

Adult↗
PubMed1979

Efficacy of Alrestatin, an aldose reductase inhibitor, in human diabetic and nondiabetic lenses.

Immediately after cataract extraction, lenses from diabetic and nondiabetic patients were collected, classified, and assayed or incubated in high-glucose medium. The distribution of cataract types within the diabetic and nondiabetic groups was almost identical. The aldose reductase (AR) inhibitor AY22,284 (Alrestatin) was as effective in blocking sorbitol formation in diabetic as in nondiabetic lenses. While there was no difference in the level of intralenticular glucose, the diabetic lens produced significantly more sorbitol than did the nondiabetic lens. Also, the activity of polyol dehydrogenase (PD) was much lower in the diabetic population. The diabetic lenses swelled slightly more (P <.2) than nondiabetic lenses in high glucose media, and AY22,284 was effective in reducing the swelling of diabetic lenses in 35.5 mM glucose medium. While these results are preliminary, they suggest that diabetes, in some way, may confer on the human lens an increased susceptibility to osmotic stress via the sorbitol pathway. It is also reassuring to note that an AR inhibitor is no less effective in blocking the more active AR in the diabetic than in the nondiabetic lens. The therapeutic implications of this are discussed.

Aldehyde Reductase↗
PubMed1979

Dermatological and ocular examinations in rabbits chronically photosensitized with methoxsalen.

Four groups of female Dutch-belted rabbits (Oryctulagus cuniculus) were given methoxsalen (12 mg/kg) or placebo by oral intubation and 1 hr later were exposed to UVA for either 2 or 8 hr. This procedure was repeated 5 days each week for 18 mo. A fifth group received no drug and no UVA exposure. The skin of the animals given methoxsalen and UVA showed signs of acute and chronic phototoxicity. Multiple peripheral blood parameters of hepatic, renal and hematologic function were normal and were not different between groups. Complete ophthalmoscopic examinations were performed periodically. No cataracts were seen in any of the animals. This data provides the perspective that in one species the daily dose of methoxsalen and UVA required to induce chronic cutaneous photosensitization is lower than the daily dose required to induce cataracts. It is inadvisable to interpret this data as suggesting that no risk exists for patients being treated with oral methoxsalen photochemotherapy. The experimental evidence supporting photosensitization as a cause of cataracts and implicating a role of lens DNA in this cataractogenesis is reviewed. Because methoxsalen-UVA alterations of lens DNA or protein could lead to delayed onset of cataracts, and because of the serious nature and potential preventability of phototoxic lens opacification, appropriate protective eye wear is recommended for all patients receiving oral psoralen photochemotherapy.

Animals↗
PubMed1979

Thermal burns: the management of thermal burns of the lids and globes.

Our experience with 40 patients with eyelid and globe burns is reviewed. Initial emphasis should be placed on close monitoring, particularly of partially alert patients, debridement and treatment of corneal exposure with artificial tears and scleral shells when needed. The use of soft contact lenses in 2 patients with exposure was unsuccessful. Surgical treatment should be initiated when corneal exposure fails to respond to medical therapy. It is advisable to wait for the end stage of scarring so as to optimize chances for a single definitive correction. The use of retroauricular, supraclavicular or inner arm skin for grafting whenever possible is advised. The use of Frost sutures, tie-on dressings, and separate operations for upper and lower lids is recommended. Superficial wound sepsis is not a contraindication to grafting. Preoperative systemic or topical antibiotics do not seem to affect the outcome of the graft.

Adult↗
PubMed1978

Classification of human cataracts.

A stereoscopic system of lens photography was developed and was applied in the classification of different forms of cataract. Lenses, after surgical extraction, can be classified by a technician, independent of ophthalmological collaboration. This system meets the needs of the laboratory scientist and has been adopted by the Cooperative Cataract Research Group.

Cataract↗
PubMed1978

Molecular sieving in suprachoroidal fluid formation in man.

Suproachoroidal fluid (SCF) obtained at the time of the surgical evacuation of a clinically significant choroidal detachment (CD) was analyzed for its chemical and cellular components in four distinct subgroups: (1) CD following cataract surgery, (2) CD (nonhemorrhagic) following glaucoma surgery, (3) CD (hemorrhagic) following glaucoma surgery, and (4) intraoperative CD during glaucoma surgery in patients with elevated episcleral venous pressure. The fluid obtained in groups 1, 2, and 4 was clear and slightly xanthochromic and contained low-molecular-weight substances in concentrations essentially equal to serum. Proteins and other high-molecular-weight substances were present in lesser amounts than in serum. Albumin, alpha1-antitrypsin, and transferrin were present in amounts approximately equal to those in serum, whereas alpha2-macroglobulin, IgM and IgG were decreased. beta-Lipoprotein and beta-complement were absent. It is postulated that this distribution of serum proteins is a manifestation of molecular sieving and is consistent with the existence of an isoporous membrane between the intravascular and suprachoroidal space with a pore diameter of 144 A. In the intraoperative choroidal effusions, there was evidence for exclusion of more of the lower, as well as all of the higher, molecular weight proteins. This suggested that the degree of molecular sieving increased with increasing filtration rate. In the hemorrhagic SCF, the distinctive character of the fluid and the protein concentrations indicated that the integrity of the capillary membrane was mardkedly disrupted, thereby allowing higher-molecular-weight proteins and cellular elements to enter the space.

Ascorbic Acid↗
PubMed1977

Stability of mammalian lens phosphofructokinase.

Two interconvertible phosphofructokinase (PFK) forms were found in rat and human lenses; whereas only one predominant form was found in calf lens. PFK isolated from these lenses possessed a common property, i.e., pH-dependent cold (or acid) lability. The inactivation was prevented by including either adenosine triphosphate (ATP) or fructose-6-phosphate (fru-6-P) in the incubating media. The protective effect of ATP or fru-6-P was complete in rat or calf lenses. In human lens, although fru-6-P was fully protective, ATP protected only partially. The inactivation could be reversed by addition of fru-6-P, but not ATP, to the incubating media at 37.5 degrees C. Lens organ culture studies showed that the depletion of lenticular ATP seemed to precipitate the loss of PFK.

Adenosine Triphosphate↗
PubMed1977

The ocular manifestations of juvenile rheumatoid arthritis.

We followed 210 cases of JRA closely for 14 years. Thirty-six patients (17.2%) developed iridocyclitis; it most frequently occurred in young females (0-4 years) with monarticular or pauciarticular form of the disease. In 30% of the patients iridocyclitis was first detected after 16 years of age. Forty-two percent had active iridocyclitis on entry. By combining quantitative antinuclear antibody titers with age, sex, and time on onset of arthritis, it has been possible to define the risk of developing iridocyclitis in individual patients. Our approach was effective in detecting iridocyclitis in new cases and exacerbations of the disease in established cases. Forty-four percent of patients with iridocyclitis had one or more identifiable early signs or symptoms. Iridocyclitis in 36% of patients did not respond to more than 6 months of intensive topical treatment with corticosteroids and mydriatics. Despite this statistic, patients had a better outcome than those experiencing the 50% incidence of blinding complications cited in earlier studies. Cataract and band keratopathy occurred in only 19% and 11% of our group, respectively. Only one case of chorioretinopathy was found in 173 patients who had received antimalarials; a significant number of posterior subcapsular cataracts were found in 75 patients who had received systemic corticosteroids. Keratoconjunctivitis sicca developed in 3 patients with iridocyclitis. Surgical treatment of cataracts, band keratopathy, and glaucoma achieved uniformly discouraging results.

Adrenal Cortex Hormones↗
PubMed1976

Properties of rat lens phosphofructokinase.

Two interconvertible forms of phosphofructokinase (PFK) have been eluted from a DEAE-cellulose column from the supernatant fraction of rat lens homogenates centrifuged at 96,000 x g for 1 hour at 0 to 4 degrees C. The interconversion can be manipulated by a change in the pH of the extracting and eluting buffers. PFK-I is the dominant form at pH between 7.4 to 7.05, while PFK-II dominates at pH 7.4 to 8.2. PFK-II is believed to be the functional form; it is inhibited by high concentrations of ATP and the inhibitory effect is enhanced by more acidic pH. Fructose-6-phosphate counteracts ATP inhibition, but the most potent de-inhibitors are ADP and AMP. Among the inorganic ions tested, sulfate, phosphate, ammonium, and potassium also de-inhibit, whereas calcium further inhibits the enzyme. The behavior of PFK under physiologic conditions and the significance of the presence of two forms of PFK in the lens are discussed.

Adenosine Triphosphate↗