Attempts were made to study the relative frequency of the degenerating cells in the Bar eye discs at different developmental stages of Drosophila melanogaster. The cells of the degenerative area in the eye discs contain several dense inclusion bodies of varied internal structure. These are myelin like figure, cell organelles fragment and lipid droplet and which are found in the eye disc cells. The frequency of these types of fragments changes in different stages of the eye disc. Most of these electron dense bodies which were limited by a single membrane showed acid phosphatase reaction products. This acid phosphatase-positive and membrane-bounded structure may be defined as lysosomes. These fine structural changes and their association with acid phosphatase reaction products are interpreted as changes in lysosomes going from prelysosomes to lysosomes and finally to post types. The lysosomes in the Bar eye discs decrease considerably resulting from the acetamide-treatment. These results further suggest that acetamide acts to inhibit the formation of lysosomes during cytodifferentiation of the cell clusters in the Bar eye discs

View full abstract

A comparison was made of the frequency patterns for the different kinds of dumpy exceptions induced by X-rays in mature sperm of Drosophila.
The results obtained indicate that (i) the yield of dumpy exceptions of the o and v types (complete) increases with exposure up to 3000R beyond which there is no further increase; (ii) the frequency of ol and vl exceptions (complete) tends to increase faster than linearly with no evidence for a decrease at 4500R; (iii) the exposurefrequency relationship for the ov and olv exceptions (complete) does not depart from linearity; (iv) the over-all frequencies of o, v, ol and vl (complete) at the three exposure levels are also consistent with a linear increase with exposures; (v) such a linear does-dependency is also observed on the yield of recovered mutations (complete) at the other marker loci, y, w, m and f; (vi) the frequency of fractional dumpy mutants appears to remain approximately the same irrespective of exposure. The present findings tend to suggest that the exposure-frequency relationships for the ifferent kinds of dumpy mutations are different.

View full abstract

Using human diploid cells derived from a 5-month embryonic lung studies were made on optimal culture conditions for colony formation (plating efficiency) and the effects of some chemical mutagens and a selective agent on the plating efficiency.
Among the various media tested, Ham's medium F12 supplemented with 10% calf serum gave the highest plating efficiency, followed by Eagle's basal medium, Eagle's minimum essential medium, each supplemented with 10% calf serum, Puck's medium N16CF and Puck's medium F16 with 10% calf serum.
The effects of various concentrations of ethyl methanesulfonate (EMS), N-methyl- N'-nitro-N-nitrosoguanidine (MNNG) and 8-azaguanine (8AG) on the plating efficiency of cells were tested and D₀ values were calculated from the concentration-survival curves. The D₀ value for 14 day-treatment with EMS was 9.6×10^-4M. The D₀ values for 2 hour- and 14 day-treatments with MNNG were 1.2×10^-5M and 1.1×10^-5M, respectively. The D₀ value for 8AG was 0.73μg/ml (4.8×10^-6M).

View full abstract

Human diploid cells were treated with ethyl methanesulfonate (EMS) and cultured in selection medium containing 8-azaguanine (8AG) to induce mutation to 8AG-resistance. The effects of factors such as the inoculum size and the mutation expression time on the induced mutation frequency of cells were examined. When cells were treated with 10^-2M EMS for 2 hours and selected with 10μg/ml of 8AG, the induced mutation frequency was highest on inoculation of 2.5×10⁵ cells, although this frequency was not significant statistically. When EMS-treated cells were selected with 30μg/ml of 8AG, the highest induced mutation frequency was obtained on inoculation of 10⁵ cells. The mutation frequency was higher when 10⁵ cells treated with EMS were cultured in normal medium for 48 hours (mutation expression time) before selection with 8AG, than in cultures with longer or shorter mutation expression times. This mutation expression time of 48 hours corresponds to the time during which about half the cell population treated with EMS divides once. Microscopic examination on the numbers of cells in colonies indicated that human diploid cells treated with or without EMS do not all grow exponentially but that in some cases after each cell division only one daughter cell continued to divide.

View full abstract

Monosomic analysis was carried out to determine the chromosomal locations of the fertility-restoring genes of Triticum compactum cv. No. 44 against the Aegilops caudata cytoplasm, and those of T. aestivum cv. Chinese Spring against the Ae. umbellulata cytoplasm. T. compactum cv. No. 44 carried two duplicated restoring genes, Rfc₂ and Rfc₃ on its chromosomes, 6B and 1D, respectively. T. aestivum cv. Chinese Spring carried two complementary genes, Rfu₁ and Rfu₂ on its chromosomes, 1B and 2B, respectively. A review of the literature, together with the present results revealed that all the satellited chromosomes so far tested carry some restoring genes. Additional evidence from the study of T. aestivum strain Salmon suggested that the restoring genes are located in the nucleolus organizer region of the respective chromosomes. The restoring genes on the four homoeologous chromosomes of group 1 are also assumed to be homoeologous.

View full abstract