United States       Prevention, Pesticides     EPA712-C-96-220
          Environmental Protection    and Toxic Substances     June 1996
          Agency         (7101)
&EPA    Health Effects Test
          Guidelines
          OPPTS 870.5275
          Sex-Linked Recessive
          Lethal Test in Drosophila
          melanogaster
                'Public Draft"

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                           INTRODUCTION
     This guideline is one of a series of test guidelines that have been
developed by the Office of Prevention, Pesticides and Toxic Substances,
United States Environmental Protection Agency for use in the testing of
pesticides and toxic substances, and the development of test data that must
be submitted to the Agency for review under Federal regulations.

     The Office of Prevention,  Pesticides and Toxic Substances (OPPTS)
has  developed this guideline through  a  process of harmonization that
blended the testing  guidance and requirements that existed in the Office
of Pollution Prevention and Toxics  (OPPT) and appeared in Title 40,
Chapter I,  Subchapter R of the Code of Federal Regulations  (CFR), the
Office of Pesticide Programs (OPP) which appeared in publications of the
National Technical  Information Service (NTIS) and the guidelines pub-
lished by the Organization for Economic Cooperation and Development
(OECD).

     The purpose of harmonizing these guidelines into a single set of
OPPTS  guidelines is to minimize variations among the testing procedures
that must be performed to meet the data requirements of the U. S. Environ-
mental Protection Agency under the Toxic  Substances Control Act (15
U.S.C. 2601) and the Federal Insecticide,  Fungicide and Rodenticide Act
(7U.S.C. I36,etseq.).

     Public Draft Access Information: This draft guideline is part of a
series of related harmonized guidelines that  need to  be considered as a
unit. For copies: These guidelines are available electronically from the
EPA Public Access  Gopher (gopher.epa.gov) under the heading "Environ-
mental Test Methods and Guidelines" or in paper by contacting the OPP
Public    Docket    at    (703)    305-5805    or     by    e-mail:
guidelines@epamail.epa.gov.

     To Submit Comments: Interested persons are invited to submit com-
ments. By mail: Public Docket and Freedom of Information Section, Office
of Pesticide Programs, Field Operations Division (7506C), Environmental
Protection Agency,  401  M  St.  SW.,  Washington, DC 20460. In  person:
bring to: Rm. 1132, Crystal Mall #2, 1921 Jefferson Davis Highway, Ar-
lington, VA. Comments may also be submitted  electronically by  sending
electronic mail (e-mail) to: guidelines@epamail.epa.gov.

     Final  Guideline Release: This guideline is available  from the U.S.
Government Printing Office, Washington, DC 20402 on The Federal Bul-
letin  Board.   By  modem   dial   202-512-1387,   telnet   and  ftp:
fedbbs.access.gpo.gov (IP 162.140.64.19),  or  call 202-512-0132 for disks
or paper copies.  This  guideline is also available electronically in ASCII
and PDF (portable document format) from the EPA Public Access  Gopher
(gopher.epa.gov) under the heading  "Environmental Test Methods and
Guidelines."

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OPPTS 870.5275  Sex-linked  recessive lethal  test in  Drosophila
melanogaster.
     (a) Scope—(1) Applicability. This guideline is intended to meet test-
ing  requirements  of  both  the  Federal  Insecticide,  Fungicide,  and
Rodenticide Act (FIFRA) (7 U.S.C. 136, et seq.) and the Toxic Substances
Control Act (TSCA) (15 U.S.C. 2601).

     (2) Background. The  source materials used in developing this har-
monized OPPTS test guideline are OPPT  40  CFR 798.5275 Sex-Linked
Recessive  Lethal Test in Drosophila melanogaster and OECD 477 Genetic
Toxicology:   Sex-Linked  Recessive   Lethal  Test   in   Drosophila
melanogaster.

     (b) Purpose. The sex-linked  recessive  lethal  (SLRL) test  using
Drosophila melanogaster detects the occurrence of mutations, both point
mutations  and small deletions, in the  germ line of the  insect. This test
is  a  forward mutation assay capable of screening for mutations  at  about
800  loci on the X-chromosome.  This  represents about 80 percent  of all
X-chromosome loci. The X-chromosome  represents  approximately one-
fifth of the entire haploid genome.

     (c) Definitions. The definitions in section 3 of TSCA and in 40 CFR
Part  792—Good Laboratory Practice Standards (GLP) apply to  this test
guideline.  The following definitions also apply to this test guideline.

     Lethal mutation is a change in the genome which, when expressed,
causes death to the carrier.

     Recessive mutation is  a  change in the genome  which is expressed
in the homozygous or hemizygous condition.

     Sex-linked genes are present on the sex (X or Y) chromosomes. Sex-
linked genes in the context of this guideline refer  only  to those located
on the X-chromosome.

     (d) Reference substances. These  may include, but need not be lim-
ited to, ethyl methanesulfonate or jV-nitrosodimethylamine.

     (e) Test method—(1) Principle. Mutations in  the X-chromosome of
D. melanogaster are phenotypically expressed in males carrying the mutant
gene. When the mutation is lethal in the hemizygous condition,  its pres-
ence is inferred from  the absence of one  class  of male  offspring  out of
the two that are normally produced by a heterozygous female. The SLRL
test takes  advantage of these facts by means of specially marked and ar-
ranged chromosomes.

     (2) Description. Wild-type males are treated and mated to appropriate
females. Female offspring are mated  individually to their brothers, and
in the next generation the  progeny  from  each  separate  dose are  scored
for phenotypically wild-type males. Absence of these  males indicates that

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a sex-linked recessive lethal mutation has occurred in a germ cell of the
PI male.

     (3) Drosophila stocks. Males of a well-defined wild type stock and
females of the  Muller-5  stock may be used. Other appropriately marked
female stocks with multiple inverted X-chromosomes  may also be used.

     (4) Control groups—(i) Concurrent controls. Concurrent positive
and negative (vehicle) controls should be included in each experiment.

     (ii) Positive controls. Examples  of positive controls include ethyl
methane sulfonate and jV-nitrosodimethylamine.

     (iii) Other positive controls. Other positive control reference sub-
stances may be  used.

     (iv) Negative  controls. Negative  (vehicle) controls  should be in-
cluded. The size  of the negative (vehicle) control group should be  deter-
mined by the availability of appropriate laboratory historical control data.

     (5) Test chemicals—(i)  Vehicle. Test chemicals  should be dissolved
in water. Compounds which  are insoluble in water may be dissolved or
suspended in appropriate vehicles (e.g., a mixture of ethanol and Tween-
60 or 80)  and then diluted  in water or saline prior to administration. The
use of dimethylsulfoxide as a vehicle  should be avoided.

     (ii) Dose levels. For the initial assessment of mutagenicity, it is suffi-
cient to test  a  single dose of the  test substance for  screening  purposes.
This dose  should be the maximum tolerated dose, or that which produces
some indication of toxicity, or should be the highest dose attainable. For
dose-response purposes,  at least three additional dose levels  should  be
used.

     (iii) Route of administration.  Exposure may be oral, by injection
or by exposure to  gases or vapors.  Feeding of the test compound may
be done in sugar solution.  When necessary, substances may be  dissolved
in 0.7 percent NaCl solution and injected into the thorax or abdomen.

     (f) Test  performance—(1) Treatment and mating. Wild-type males
(3 to 5 days old)  should  be treated with the  test substance and mated
individually to  an appropriate number of virgin  females from the Muller-
5 stock or  females  from  another appropriately marked (with multiply-in-
verted X-chromosomes) stock. The females should be replaced with fresh
virgins every 2  to 3 days  to cover the entire germ cell cycle. The offspring
of these females are scored for lethal effects corresponding to the effects
on mature sperm, mid or late  stage spermatids, early spermatids, spermato-
cytes and spermatogonia at  the time of treatment.

     (2) Fl matings. Heterozygous  FI females from the  above crosses
should be allowed  to mate individually (i.e., one female per vial) with

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their brothers. In the F2 generation, each culture should be scored for the
absence of wild-type males. If a culture appears to have arisen from an
FI female carrying a lethal in the parental X-chromosome (i.e., no males
with the treated chromosome are observed), daughters of that female with
the same genotype should be tested to ascertain if the lethality is repeated
in the next generation.

     (3) Number of matings. (i) The test should be designed with a pre-
determined  sensitivity and power. The number  of flies in each group
should reflect these defined parameters.  The spontaneous mutant frequency
observed in the appropriate control group will strongly influence the num-
ber of treated chromosomes that must be  analysed to  detect substances
which show mutation rates  close to those of the controls.

     (ii) Test results should be confirmed in a separate experiment.

     (g) Data and report—(1) Treatment of results. Data should be tab-
ulated to show  the number  of chromosomes  tested,  the number  of
nonfertile males and the number of lethal chromosomes at each exposure
concentration and for each mating period for  each male treated. Numbers
of clusters of different size  per male should be reported.

     (2) Statistical evaluation.  Data should be evaluated by appropriate
statistical techniques.

     (3) Interpretation of results, (i) There are  several criteria for deter-
mining a positive result, one of which is  a statistically significant  dose-
related increase  in the number of sex-lined recessive lethals.  Another cri-
terion may be based upon detection of a reproducible and statistically sig-
nificant positive response for at least one of the test points.

     (ii) A test  substance which  does not produce either a statistically sig-
nificant dose-related increase in the number of sex-linked recessive lethals
or a statistically significant and reproducible positive response at any one
of the test points is considered non-mutagenic in this system.

     (iii) Both biological and statistical significance  should be considered
together in the evaluation.

     (4) Test evaluation,  (i) Positive  results in the  SLRL test in  D.
melanogaster indicate that under the test conditions the test agent causes
mutations in germ cells of this insect.

     (ii) Negative results indicate that  under the test conditions the  test
substance is not mutagenic  in D.  melanogaster.

     (5) Test report.  In addition to  the  reporting recommendations as
specified under 40 CFR part 792, subpart J the following specific informa-
tion should be reported.

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     (i) Drosophila stock used in the assay,  age of insects, number of
males treated, number of sterile males, number of F2 cultures established,
number of F2 cultures without progeny.

     (ii) Test chemical vehicle, treatment and sampling  schedule, exposure
levels, toxicity data, negative (vehicle) and positive controls, if appropriate.

     (iii) Criteria for scoring lethals.

     (iv) Number of chromosomes tested, number of chromosomes scored,
number of chromosomes carrying  a lethal mutation.

     (v) Historical control data, if available.

     (vi) Dose-response relationship, if applicable.

     (h) References. The following references  should be consulted for ad-
ditional background material on this test guideline.

     (1) Sobels, F.H. and Vogel, E. The capacity of Drosophila for detect-
ing relevant genetic damage. Mutation Research 41:95-106 (1976).

     (2) Wurgler  F.E. et al. Drosophila as assay system for detecting ge-
netic  changes. Handbook of mutagenicity test procedures.  Eds. Kilbey,
B.J., Legator, M., Nichols, W.,  Ramel, C.  Elsevier/North  Holland Bio-
medical, Amsterdam (1977) pp. 335-373.

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