الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 104 |  |  |
| | | from | 104 | | |
Abstract
--~’-----_ ..._._----------._,._-- .._--”------ ._------ _._-- .._ ...
SUJOlARY AllD COlfCLUSIOll ----------------------
.In the present work, a comparison between the
genetic activities of the two organophosphorus insecticides
hostathion and dimethoate ~ yeast S. cerevisiae
was carried out. The main results obtained can be summarized
as follows:
1- Both chemicals were genetically active in the diploid
yeast strain ex -adl-14 X ~5 v-p4. The technical
preparation of hostathion (60 % E.C.) was more active
than the formulated one (40” E.C.) at all cODcentrations.
No wide variation was observed with the two
preparations of the d1methoate. The latter seems to
be less affected by the additives and impurities in
these preparations.
2- With the technical preparation, the BUrri val curve
of hostathion treatment showed two shoulders. The
corresponding curve of dimethoate was somewhat linear.
J- Hostathion had induced higher frequencies of colonies
with altered sectors than dimethoate, which mainly
induced completely altered colonies. However, the
curve of the genetic actiVity ot hostath10D showed
84
two peaks. one of them for the sectored colonies and
the other for the completely altered ones. These
peaks were at the same positions of the shoulders recovered
in the survival curve.
4- The degree of sporulation in altered colonies induced
by hostathion and dimethoate was obviously decreased
specially at higher concentration. Viability of. spores
has also dropped. Dimethoate was more active in
this respect.
5- When the haploid strainS -ad2-1148 was treated with
both insecticides, isolates surviving these treatments
showed higher frequencies and UV-induced reversion.
6- Similar samples of asci t..romthe UJItreat~ and ”.r•••.~ed
with each of hostatbllon and d:iJnethoate diploid strain Sl~95D
X a -5 2072 A were dissected. fhe tetratype asci containing
recombinant chromatides, were recovered in percentages
ot 10. 23, and 60 for the three cases, respectively.
7- WhenDone, one or both at the two haploid ccaplelaenting
strains were treated with either hostathioD or
dimethoate before ero_ing, higher frequencies of
-- 1
85
sectored colonies among diploid were only induced
after hostath1on treatments.
On the basis ot these results, the following conclusions
can be stated:
1- It seemed that dimethoate gave mainly lesions, which
could be fixed in the presynthetic period in the cell
cycle leading to the formation of completely. altered
colonies. The role of error-prone repair -mechanisms
WBS more obvious in case of hostathion leading to
consequent formation of sectored colonies. ~hese
types were correlated with the level of survivals revealing
the sensitivity of cells in Gl and G2 in the
exposed population. The first shoulder in this curve
was correlated with the peak of completely altered
correlated with the peak of completely altered colonies,
mostly resulting from 01 cells (two-strsnd alteration or
pure-mutants). The second shoulder was located at the
same concentration with the peak of aectored colonies,
resulting from cells fixing their alterations through
replication (single-strand alteration-mosaics).
2- Results of the degree of sporulation and spore viability
indicated that higher frequencies o~ .eiotic abnormalities
than those in the untreated strain were
obtained.
3- A clear selective action of both chemicals was reflected
in the pattern of spontaneous and UV-induced
reversion isolates surviving their treatments. The
two insecticides selected a traction of the cell pop-
Ulation of the haploid strain a-ad
2
-l148 that was charaeterized
by higher frequencies than that of the untreated
sample. ’
4- Hostathion proved to b~ more efficient in its recombinogenic
activity than dimethioate. This aitference
was postulated to be due to the induction of more
active recombination competence system.
5- The last conclusion concerns significance ot these
results to the problem of environmental mutagenesis
and pollution. Hostath1on and dimethoate were genetically
active in the eucaryote. HostathioD was found
to be mutagenic and teratogenic in rats (El-Sherif,
personal CODIIDliDlca110n). .At 1he same t1.e, ,11 was recommended
tor wide use 1D Egypt.
,
--------