Biomedical Engineering Reference
In-Depth Information
the long-tailed macaque (
VandeVoort and Tarantal, 1991
),
and the marmoset (
Oerke et al., 1996
). Because of its
reliability for documenting the response to ovarian stimu-
lation and aspiration of follicles, ultrasonography can be
used to recover oocytes for
Determination of CG concentration has also become
a standard means for diagnosing pregnancy in many New
World species. In the squirrel monkey, the concentrations
of hormone gradually increases during early pregnancy and
reaches maximum values at midgestation (
Diamond et al.,
1987
). Analysis of CG is most accurate between 40 and 60
days of pregnancy; however, single determinations have an
inherent 10% risk of false-negative responses due to low
CG levels (
Hodgen et al., 1978
). CG in the marmoset is
excreted throughout pregnancy, and maximum levels can
be detected between the 8th and 9th week of gestation
(
Hearn et al., 1988; Hobson et al., 1977
). Gestational levels
of CG are first noted about 20 days after the LH peak in
tamarins and continue to be elevated for another 80 days
(
Kleiman et al., 1978; Heistermann et al., 1987; Ziegler
et al., 1987
). In the owl monkey, CG can be detected about
16 weeks prepartum until birth.
Shaikh et al. (1976)
found that pregnancy confirmation
in baboons is more reliably detected by a plasma CG RIA
than by the urine hemagglutination inhibition assay
(
Hodgen and Ross, 1974
). Although plasma CG RIA is
more time-consuming (results obtained 18 hours after
sample collection), pregnancy is identified on GD 16 with
96.6% reliability. Plasma estradiol and progesterone RIA
determinations, which can be obtained more quickly, have
the same level of accuracy (96.6%) on GD 16 when eval-
uated according to a computer-derived formula.
A quantitative radioreceptor assay (RRA) was
employed for early diagnosis of pregnancy in M. fas-
cicularis by determining serum CG levels 3
e
4 weeks after
conception (
Yoshida et al., 1987
). Serum CG levels
increased to 50
m
g/ml in the majority of animals evaluated.
Three weeks after conception, 86% of all pregnant animals
showed a positive response, and by 4 weeks after concep-
tion, a 95% positive response was reported. Five percent of
the tested animals yielded false-negative responses at
4 weeks due to low CG levels; no false-positive responses
were reported.
Monitoring steroid hormone metabolites in urine has
also been used as a means of detecting pregnancy in some
NewWorld species. Measurement of hydroxypregnenolone
excretion has been used for this purpose in marmosets
(
Hodges et al., 1983; Heger and Neubert, 1987
), tamarins,
and owl monkeys (
Kleiman et al., 1978; Heistermann et al.,
1987; Ziegler et al., 1987
). In a study by
Czekala et al.
(1981)
, pregnancy was monitored via small urine volumes
and measurements of immunoreactive E
t
and LH/CG
bioactivity in four diverse species: the orangutan, pygmy
chimpanzee, Douc langur, and capuchin (
Czekala et al.,
1981
). Measurement of E
t
alone was sufficient to detect and
monitor pregnancy in most species. However, in some
species it may be necessary to assess individual estrogens if
a more precise evaluation is necessary. Measurement of
LH/CG bioactivity usually allows for earlier detection of
in vitro fertilization in
macaques.
Detection and Monitoring of Pregnancy
Pregnancy is diagnosed at the earliest point by using assays
that measure the presence of chorionic gonadotropin (CG).
CG is produced by the trophoblast and functions to prevent
luteolysis; detection of CG is the basis for over-the-counter
pregnancy tests in women. In the 1970s and 1980s,
hemagglutination inhibition tests for urinary CG were
developed for use in Old World monkeys. These tests
include the Subhuman Primate Pregnancy Test Kit (SHPT)
and the Nonhuman Primate Pregnancy Test (NHPPT)
developed by
Hodgen and Ross (1974)
using an antiserum
to the
b
subunit of ovine LH, which is common to the CG of
humans, gorillas, orangutans, chimpanzees, baboons, and
macaques. This antiserum is, however, dissimilar to FSH
and LH of baboons and macaques. Only 0.2 ml of neat
urine (or an equivalent amount of urine extract) is required
for testing, and results are obtained within 3 hours after the
samples are collected. This method is reliable for con-
firming pregnancy on gestation day (GD) 16 (fivefold
concentration of urine required) or by GD 18 (neat urine
tested). Collecting aliquots of freshly voided urine gives the
most satisfactory result because it minimizes the time and
collection of samples in addition to urine debris. This test
became the method of choice for routine breeding
management situations and has been used successfully in
rhesus (
Hodgen and Ross, 1974
) and long-tailed macaques
(
Boot and Huisin't Veld, 1981
), baboons (
Hodgen and
Niemann, 1975
), and chimpanzees (
Hodgen et al., 1976
).
Both false-positive and false-negative tests are reported,
due in part to the variability in urinary macaque CG
excretion from animal to animal.
ELISA, which may now be used for accurate
measurement of CG in serum or urine in macaques (
Munro
et al., 1991
), is a particularly valuable method for studies in
which changes in CG concentrations may be relevant. In
2001,
Shimizu et al. (2001)
reported on a noninstrumented
ELISA for pregnancy detection in macaques that used
a color change visible to the naked eye, similar to a human
pregnancy test. The false-positive rate for this test was zero,
but the false-negative rate was relatively high, such that
these investigators reported an accuracy of 70%. Recently,
Lohstroh et al. (2007)
reported on the validation of
a chemiluminescent immunoassay measurement of CG in
macaque urine, adapted to the platform of the Bayer ACS-
180 autoanalyzer. Using this method, CG was on average
first detectable at GD 12
e
13.
