Cytochemical and biochemical studies of mitochondria in Xenopus laevis oocytes
Cytochemical and biochemical studies of mitochondria in Xenopus laevis oocytes
The differentiation of mitochondria in the previtellogenic oocytes of Xenopus laevis was investigated by means of morphometry, cytochemistry and biochemistry. Morphometrical studies revealed that the number of mitochondria in the previtellogenic oocytes increases enormously. The volume density of these mitochondria was found to remain essentially constant. Changes in the number of cristae in the mitochondria accompanied similar changes of the mean mitochondrial volume. Ultrastructural cytochemistry using 3,3'-diaminobenzidine revealed that cytochrome oxidase activity is exclusively localised on the cristae and intermembrane space of mitochondria. The pattern of staining was always the same and no mitochondria were found unstained. Quantitation of the DAB staining of mitochondria revealed that the amount of stain per unit area in 1 pm sections of the mitochondrial cloud varied, attained a maximum value when 200 pm oocytes were used, and that in late previtellogenic oocytes was significantly reduced. Biochemical assays of succinate dehydrogenase and cytochrome oxidase using mitochondrial fractions obtained from oocytes of various developmental stages suggested that in oocytes from 100 to 300 pm in size a significant decrease in the specific activity of cytochrome oxidase occurs, whereas that of SDH remains essentially constant. However, the low purity of the mitochondrial fractions from oocytes 400-1200 Fm suggests that in these oocytes the specific activities are higher than those estimated, and may actually increase rather than decrease. Previouss workers have found that the amount of mtDNA increases in the previtellogenic oocytes and then is kept at a constant level. In the light of this finding, the results support the view that enrichment of the oocytes in both enzymes is preceded by accumulation of mtDNA. The possible existence of a derepression mechanism, which may trigger the commencement of accumulation of SDH and cytochrome oxidase, is discussed.
University of Southampton
1977
Marinos, Evangelos
(1977)
Cytochemical and biochemical studies of mitochondria in Xenopus laevis oocytes.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
The differentiation of mitochondria in the previtellogenic oocytes of Xenopus laevis was investigated by means of morphometry, cytochemistry and biochemistry. Morphometrical studies revealed that the number of mitochondria in the previtellogenic oocytes increases enormously. The volume density of these mitochondria was found to remain essentially constant. Changes in the number of cristae in the mitochondria accompanied similar changes of the mean mitochondrial volume. Ultrastructural cytochemistry using 3,3'-diaminobenzidine revealed that cytochrome oxidase activity is exclusively localised on the cristae and intermembrane space of mitochondria. The pattern of staining was always the same and no mitochondria were found unstained. Quantitation of the DAB staining of mitochondria revealed that the amount of stain per unit area in 1 pm sections of the mitochondrial cloud varied, attained a maximum value when 200 pm oocytes were used, and that in late previtellogenic oocytes was significantly reduced. Biochemical assays of succinate dehydrogenase and cytochrome oxidase using mitochondrial fractions obtained from oocytes of various developmental stages suggested that in oocytes from 100 to 300 pm in size a significant decrease in the specific activity of cytochrome oxidase occurs, whereas that of SDH remains essentially constant. However, the low purity of the mitochondrial fractions from oocytes 400-1200 Fm suggests that in these oocytes the specific activities are higher than those estimated, and may actually increase rather than decrease. Previouss workers have found that the amount of mtDNA increases in the previtellogenic oocytes and then is kept at a constant level. In the light of this finding, the results support the view that enrichment of the oocytes in both enzymes is preceded by accumulation of mtDNA. The possible existence of a derepression mechanism, which may trigger the commencement of accumulation of SDH and cytochrome oxidase, is discussed.
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Published date: 1977
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Local EPrints ID: 458660
URI: http://eprints.soton.ac.uk/id/eprint/458660
PURE UUID: e3860a63-c1d6-4791-a785-f938cbd5b185
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Date deposited: 04 Jul 2022 16:53
Last modified: 04 Jul 2022 16:53
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Author:
Evangelos Marinos
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