Amphibian lens histones and their relation to the cell cycle

Histones have been electrophoretically separated from acid extracts of the frog lens for the first time. The five conventional histone fractions, representing four electrophoretic bands (f1; f2b, f3; f2a2; and f2a1), are present in both the epithelial and fiber cells. In addition, a fifth fraction was isolated from both sources and the evidence suggests that it may be a tissue-specific histone, possibly related to the lysine-rich f2c fraction found previously only in nucleated erythrocytes. The epithelial cells contain a substantially greater amount of histone than the fiber cells. Moreover, the fibers, unlike the epithelium, manifest no net histone synthesis or turnover following lenticular explantation. Microspectrophotometric, radioautographic, and gel electrophoretic studies indicate that the histones are synthesized in frog lenses concurrently with DNA. Inhibition of DNA synthesis does not completely abolish that of histones but reduces it by about one-half. In the early stages of culture (prior to their synthesis and that of DNA) the histones appear to undergo alterations which are prevented by treatment with cycloheximide.

Pterygia measurements are more accurate with anterior segment optical coherence tomography - A pilot study

Introduction: Slit-lamp beam measurements of a pterygium can be difficult to reproduce accurately. Purpose: To compare standard slit-lamp beam measurements of pterygia to computer caliper measurements of Anterior Segment Optical Coherence Tomography (OCT) images. Subjects and methods: Thirteen pterygia of ten patients were evaluated. Two physicians independently measured each pterygium using the slit lamp beam. Caliper measurements of two different OCT images of each pterygium were obtained. All measurements determined the distance from the limbus to the pterygium apex. Results: The difference in the slit lamp beam measurements of each pterygium was calculated and the mean of the differences was 0.3 and the standard deviation was 0.32. The difference in the two OCT measurements of each pterygium was also calculated and the mean of the differences was 0.1 and the standard deviation was 0.12. A two-tailed t-test demonstrated a statistically significant difference in these measurements (p = 0.0256). Conclusion: Anterior Segment Optical Coherence Tomography (OCT) gives significantly more reproducible results than the slit lamp beam for measurements of the distance of a pterygium’s apex from the limbus. This tool may provide more accurate clinical assessment of extension of pterygia onto the cornea and may be useful for research purposes. Key words: pterygium; pterygia; anterior segment optical coherence tomography; OCT DOI: 10.3126/nepjoph.v3i1.4271Nepal J Ophthalmol 2011;3(5):9-12