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Biomedical subjects

T P Link

Publications and source records attributed to T P Link.

5 recordsLinked to original sources
PubMed2000

Laser pointers and the human eye: a clinicopathologic study.

We report the absence of photic retinal injury after exposing the retina to light from class 3A laser pointers for durations of up to 15 minutes. Three patients with uveal melanomas were scheduled to have an enucleation. Each agreed to have his or her retina exposed to laser light from a class 3A laser pointer prior to enucleation. Continuous exposure was directed to the fovea for 1 minute, to the retina 5 degrees below fixation for 5 minutes, and to the retina 5 degrees above fixation for 15 minutes. Ophthalmoscopic evaluation of the cornea, lens, and retina and fluorescein angiographic studies of the retina were conducted before, 24 hours after, and 11 days after laser exposure in the first case; before and 86 hours after exposure in the second case; and before, 96 hours after, and 15 days after exposure in the third case. Other than transient afterimages that lasted only a few minutes, we were unable to document any functional, ophthalmoscopic, fluorescein angiographic, or histologic evidence of damage to any structures of the eyes. Transmission electron microscopic studies of retinal sites targeted by the laser pointers in the second and third cases revealed ultrastructural abnormalities in the outer retina and the pigment epithelium that were similar to abnormalities seen in the retina approximately 8 mm away from the targeted sites. The risk to the human eye from transient exposure to light from commercially available class 3A laser pointers having powers of 1, 2, and 5 mW seems negligible.

Adult↗
PubMed1982

Snowflake degeneration of the retina.

Ten patients in four families with white or yellow-white granular-like deposits of the peripheral retina, consistent with the description of snowflake degeneration are reported. The granular changes are observable near the equatorial fundus as numerous ophthalmoscopically discrete deposits commonly up to 100 to 200 microns in size that focally thicken the retina. They can be rather evenly distributed about the entire circumference of the eye, but sometimes they may show a predilection for the inferior quadrants. The lesions need not be associated with recognizable vitreous liquefaction, vitreoretinal traction, retinal breaks, or retinal pigmentation, and in some instances the condition appears relative stable for intervals as long as five years. The similar appearance in a mother and her 9-year-old son suggests further the relative stability of the condition. In its pure form, snowflake degeneration may be an innocent dominant familial finding but when associated with other conditions such as lattice degeneration, snowflake degeneration may be of clinical significance. Affected members may have co-existing extensive white with and without pressure changes and/or lattice degeneration.

Adolescent↗
PubMed1975

Preparation and properties of three specific active derivatives of ribonuclease A obtained by methylation of methionine residues in 8 M urea.

In 8 M urea at low pH, CH3I reacts specifically with the four methionine residues of ribonuclease A, and all four residues react at the same rate. Uon removal of the denaturant, only unmodified ribonuclease and 3 of the 15 possible derivatives modified on methionine refold to regenerate activity. All the enzymatic activity is recored after chromatography on IRC-50 and the four active proteins separate from each other and from the 12 inactive derivatives, which are not eluted from the resin under the conditions used. By the use of 14CH3I, performic acid oxidation, chymotryptic digestion, and separation of the resulting peptides by ion exchange, the active species were determined to be unmodified ribonuclease, CH3Met-29-RNase, CH3Met-79-RNase, and CH3Met-29, CH3Met-79-RNase. these proteins have melting temperatures of 63, 58, 43, and 36 degrees, respectively, at pH 6.3-70. Methylation at methionine-29 or -79 has no effect on enzymatic activity. Conversely, methylation at methionine-13 or -30 prevents refolding to an active conformation at 25 degrees elution from IRC-50. These results are consistent with the positions of the four methionine residues in crystals of ribonuclease A and ribonuclease S as determined by X-ray diffraction.

Amino Acid Sequence↗