Undergraduate honors paper--Mount Holyoke College, 2007. Program in Biochemistry. / Includes bibliographical references (leaves 64-67).

The crystalline lens is a unique cellular organ that performs metabolic processes while maintaining optical functionality. Mitochondria play a vital role in providing the cell with the energy necessary for these metabolic processes and have recently been shown to be more metabolically active than previously thought. To test the hypothesis that mitochondrial function directly influences the optical function of the lens, bovine lenses were treated with 50 μM, 200 μM, 600 μM and 1000 μM menadione, a mitochondrial specific toxin that renders the mitochondria inactive, and the Back Vertex Distance (BVD) variability was observed over 216 hours. Confocal micrographs of secondary fibre cells’ mitochondria were also analyzed for 50 μM, 200 μM, and 600 μM menadione treatment over 48 hours. Increase in BVD variability (± s.e.m.) was observed within 24 hours from 0.28 ± 0.021 to 1.83 ± 0.75 for the 600 μM treated lenses. Confocal micrograph analysis showed a trend toward a decrease in the average length of mitochondria from 7.9 ± 0.8 to 3.7 ± 0.9 over for 200 μM treated lenses and from 5.9 ± 1.0 to 3.6 ± 0.6 for the 600 μM treated lenses over 48 hours. These data show that indeed menadione has a detrimental effect on mitochondria as a function of both time and concentration and this change in mitochondria precedes changes in BVD variability directly linking mitochondrial function to optical function.

The crystalline lens is a unique cellular organ that performs metabolic processes while maintaining optical functionality. Mitochondria play a vital role in providing the cell with the energy necessary for these metabolic processes and have recently been shown to be more metabolically active than previously thought. To test the hypothesis that mitochondrial function directly influences the optical function of the lens, bovine lenses were treated with 50 μM, 200 μM, 600 μM and 1000 μM menadione, a mitochondrial specific toxin that renders the mitochondria inactive, and the Back Vertex Distance (BVD) variability was observed over 216 hours. Confocal micrographs of secondary fibre cells’ mitochondria were also analyzed for 50 μM, 200 μM, and 600 μM menadione treatment over 48 hours. Increase in BVD variability (± s.e.m.) was observed within 24 hours from 0.28 ± 0.021 to 1.83 ± 0.75 for the 600 μM treated lenses. Confocal micrograph analysis showed a trend toward a decrease in the average length of mitochondria from 7.9 ± 0.8 to 3.7 ± 0.9 over for 200 μM treated lenses and from 5.9 ± 1.0 to 3.6 ± 0.6 for the 600 μM treated lenses over 48 hours. These data show that indeed menadione has a detrimental effect on mitochondria as a function of both time and concentration and this change in mitochondria precedes changes in BVD variability directly linking mitochondrial function to optical function.

published_or_final_version / Anatomy / Master / Master of Philosophy

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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2006. / Title from title screen (site viewed on Nov. 13, 2006). PDF text: xiii, 188 p. : ill. ; 11.13Mb. UMI publication number: AAT 3217532. Includes bibliographical references. Also available in microfilm and microfiche format.

Ultrastructural observations on the six-day chick embryo lens reveal that fibre cell differentiation, which involves extensive cell elongation, is characterized by the presence of numerous oriented microtubules and by marked changes in intercellular relationships which are felt to be important for cell extension. Increased Golgi activity in cells initiating elongation appears to be related to the formation of intercellular junctions and the elaboration of new surface membrane. Studies concerning the differentiation in vitro of anterior lens epithelia demonstrate that their cells elongate either to a great extent or to a limited extent, depending on factors deriving from the epithelial conformation.The conformation of an explanted anterior lens epithelium can be manipulated so that its cells elongate consistently to either a limited or a great extent. These cells, whether elongated to a limited or to a great extent, are ultrastructurally similar with respect to features reflecting cytoplasmic differentiation, including those important for morphogenesis. Their fine structure closely resembles that of fibre cells differentiating in vivo. The cells of anterior lens epithelia differentiating in vitro, whether elongating to a limited or to a great extent, are the same in terms of the nature and relative proportions of their soluble proteins as indicated by polyacrylamide gel electrophoresis. There is a change in the relative proportions of the soluble proteins accumulated by the anterior lens epithelia when they differentiate in vitro that is similar to that which occurs in cells undertaking fibre cell differentiation in vivo. It is concluded that those factors deriving from the conformation of the anterior lens epithelium that affect the degree of elongation of its cells differentiating in vitro are physical in nature. Since such physical factors are important with regard to restraining or encouraging the expression of morphogenetic potential in vitro, it is suggested that similar physical forces are important in lens morphogenesis in vivo. Observations concerning anterior lens epithelia elongating to a great extent in vitro demonstrate that their cells progressively elongate for only about three days. Well differentiated explants cultured for longer periods do not show greater elongation or further cytoplasmic differentiation. Their cells, at the ultrastructural level, resemble differentiating fibre cells in vivo rather than differentiated ones. It is concluded that the anterior lens epithelium has some capacity for differentiation independent of the ocular environment, but that the latter is essential for the expression of its full developmental potential. / Science, Faculty of / Zoology, Department of / Graduate

No description available.

Maintenance of reduced protein sulfhydryl groups is an important function of lens metabolism. In an attempt to inter-relate how lens sulfhydryl metabolism, low molecular weight peptides and trace molecular weight Zn-containing protein population was studied. The concentration of rate lens Zn-containing protein population was studied. The concentration of rat lens Zn decreased 30% from day 10 to day 35 postpartum. After 6 weeks on a low-Zn diet, rats had 25% less lens Zn than control groups. Selenite-induced cataract did not affect lens Zn concentration. Of the total lens Zn, 25% was recovered in the ultrafiltration fraction of less than 20,000 molecular weight which contained 1% of the total soluble protein. Lens tissue has low molecular weight TCA-soluble components that can bind Hg. Isoelectric points of low molecular weight protein fractions were between pI 5.2-5.5. Polypeptide molecular weight was determined to be less than 5,000 daltons by gel filtration chromatography. Aggregation on SDS-polyacrylamide gel electrophoresis yielded apparent higher molecular weights of these proteins. Although the proteins isolated had metallothionein-like character in that they were of low molecular weight, contained Zn and had acidic pI values, the paucity of cysteine residues indicates that metallothionein is not a component of low molecular weight Zn-containing lens proteins. / Master of Science