Tear lysozyme activity in frozen Schirmer strips and salivary gland biopsy as parameters of lacrimal gland function.

PURPOSE: The lysozyme concentration in human tears is an important parameter for tear gland function. The decline of lysozyme in tears reflects lacrimal gland destruction. In Sjögren's patients, lacrimal gland destruction parallels labial salivary gland destruction. The objective of this study was to determine whether human tear lysozyme that was frozen on Schirmer strips at -20 degrees C for several years maintained activity and whether there was a linear relation with inflammatory changes in labial salivary glands. METHODS: A total of 200 frozen Schirmer strips were processed. They were collected from 20 randomly selected patients each year of five consecutive years, all attending the UCSF Sjögren's Clinic. The tear lysozyme in the Schirmer strips was measured by a colorimetric assay. The average lysozyme concentration each year was calculated and compared. One third of the patients underwent labial salivary gland biopsy. The correlation was calculated between the tear lysozyme concentration and the lymphocytic focus scores in biopsy specimens. RESULTS: No significant difference of average lysozyme concentration in the Schirmer strips was found when the five different years of collection were compared. The linear relation between the tear lysozyme concentrations and the focus score in labial salivary gland biopsies showed a coefficient of r = -0.41. The linear relation between other diagnostic measurements, like Schirmer test, tear breakup time, or rose bengal staining pattern, and the focus score was lower. CONCLUSIONS: Human tear lysozyme in Schirmer strips can be stored at -20 degrees C for at least five years. There is little difference in lysozyme activity of frozen compared to unfrozen specimens. The lysozyme concentration in tears correlates better with the lymphocytic focus score in labial salivary gland biopsy than does clinical assessment and is therefore a parameter for the actual degree of tear gland destruction.

Clinical application of a homogeneous colorimetric assay for tear lysozyme.

PURPOSE: Tear lysozyme and tear lactoferrin are enzymes synthesized by the lacrimal gland. Their concentration in human tears reflects tear gland function. Tear gland dysfunction can lead to ocular surface disease. We developed a colorimetric lysozyme assay. The objective of this study was to determine the diagnostic power and the clinical application of this assay that allows rapid and precise quantification of tear lysozyme. METHODS: Tear specimens of 120 eyes (30 Sjögren's patients and 30 controls) were collected using standardized filter paper discs. Tear lysozyme concentration was determined using p-nitrophenyl penta-N-acetyl-beta-chitopentaoside as substrate in the colorimetric assay. The results were compared to clinical findings and to two commonly used tests, the Micrococcus agar diffusion assay for tear lysozyme and the tear lactoferrin immunodiffusion assay. RESULTS: The colorimetric assay showed a good dose-response relationship. The use of the assay as a method of diagnosing aqueous tear deficiency, using the clinical findings and the medical history as gold standard, demonstrated 85% sensitivity and 92% specificity. The results of the colorimetric assay when compared with the Micrococcus agar diffusion assay showed a linear relationship of r=0.77; when compared with the lactoferrin immunoassay r=0.73. CONCLUSIONS: The colorimetric assay is simple to perform and does not require sophisticated laboratory equipment and personnel. Results can be precisely quantified within one hour after tear collection. The diagnostic power of the test is comparable to previously reported assays for lysozyme and lactoferrin and will be useful in the diagnosis of ocular surface disease.

An elevated level of copper zinc superoxide dismutase fails to prevent oxygen induced retinopathy in mice.

BACKGROUND: To determine whether a higher level of copper zinc superoxide dismutase (CuZnSOD) can reduce the severity of oxygen induced retinopathy (OIR) in a mouse model. METHODS: CuZnSOD transgenic mice with a threefold increase in CuZnSOD activity and control non-transgenic mice were exposed to 90% oxygen for 12 hours a day during the first 5 days of life. After oxygen treatment, all mice were reared in room air for 10 days. Another group of transgenic and non-transgenic mice were kept in room air for 15 days and served as control groups for the oxygen effect. At day 15, all mice were killed and perfused with India ink. The retinas were flat mounted on slides and examined with a light microscope. RESULTS: There was a statistically significant increase in the incidence of OIR in mice exposed to high levels of oxygen, whether or not they were transgenic. However, there was no statistically significant difference in the severity of OIR between oxygen treated transgenic and non-transgenic mice. CONCLUSION: A threefold higher CuZnSOD activity does not protect against OIR in mice. This is an unexpected finding, since oxygen radicals are considered a major factor causing OIR, and increased CuZnSOD activity has reduced oxygen radical induced damage in several neuronal and non-neuronal systems. The possibility of a damaging role for other radicals not affected by CuZnSOD cannot be excluded.