Biomedical Engineering Reference
In-Depth Information
beneficial, especially in young pubertal or oligomenorrheic
animals, to smear the swab on a glass microscope slide and
examine it for red blood cells.
In approximately 16% of the menstrual cycles of
baboons, overt menstruation does not occur in successive
cycles, making it difficult to utilize gross observation as an
end point without collecting vaginal smears (
Hendrickx,
1971
). Vaginal smears make it possible to detect menstru-
ation in approximately 95% of the cycles but is less
convenient to measure than are the changes that occur in the
perineum (sex skin).
The sex skin (perineal swelling) is a very reliable way of
accurately dating the pregnancy in several Old World
monkeys (baboon, pig-tailed macaques, and others) and the
chimpanzee. The visible cyclic changes in the sex skin or
perineum that correlate with the menstrual cycle have been
well described in the baboon (
Hendrickx, 1971
). The
turgescent phase encompasses an initial turgescent stage
(average 4 days) when the perineal area starts to swell with
a decrease in wrinkling of the skin, which changes color
from dull pink to a pinkish red. During the subsequent
maximum turgescent stage (average 13 days), the skin of
the perineum is fully distended with no wrinkles and attains
its deepest and most intense bright red color (
Figure 8.1
a).
The deturgescent phase is similarly divided into two stages.
Initial deturgescence (average 5 days) begins with a loss of
color, a decrease in size of the swelling, and a correspond-
ing increase in wrinkles (
Figure 8.1
b). During the following
quiescent stage (average 12 days), the perineum is of
minimal size and the labia and clitoris have many wrinkles
with an overall pinkish red color. The dull epithelial surface
of the perineum, which begins to slough during the detur-
gescent stage, is usually completely shed by the end of the
quiescent phase.
Timed matings in baboons have established that Day
3
deturgescence (the third day before the onset of deturges-
cence) is the optimal day for mating (
Hendrickx, 1971
).
Endocrinological data indicate that ovulation occurs most
often on Day
2 deturgescence (
Wildt et al., 1977;
Shaikh et al., 1982
), therefore Day
1or
2shouldbe
designated as Day 0 of pregnancy.
Bielert et al. (1976)
demonstrated a positive correlation among sex skin color,
circulating levels of estradiol, and increased sexual activity as
indicated by ejaculations in periovulatory rhesus monkeys.
Another common method for detecting ovulation is
endocrinological evaluation of urine or serum. During the
normal estrous cycle, an estrogen peak occurs 15
e
24 hours
prior to a peak in luteinizing hormone (LH). The latter
triggers ovulation and the formation of the corpus luteum
with a subsequent rise in progestins. Analysis of these
hormones (i.e. the estrogens, LH, or progesterone) provides
presumptive evidence that ovulation has occurred; the
pattern of change in circulating estradiol, progesterone, and
LH has been described for most nonhuman primates
commonly used in studies.
A considerable body of evidence has been gathered
about ovulation and its relationship to ovarian and pituitary
endocrine events in M. mulatta (
Hotchkiss et al., 1971;
Weick et al., 1973; Parkin and Hendrickx, 1975; Monfort
et al., 1987
), M. radiata (
Lasley et al., 1974; Parkin and
Hendrickx, 1975
), M. fascicularis (
Monfort et al., 1987;
Behboodi et al., 1991
), Papio spp. (
Wildt et al., 1977;
Shaikh et al., 1982
), Saimiri (
Aksel et al., 1985
), Callithrix
(
Harlow et al., 1984
), and P.
1or
(a)
(b)
troglodytes (
Gould and
Faulkner, 1981
).
Hotchkiss et al. (1971)
reported that estradiol will rise
over a 3-day period prior to ovulation in M. mulatta, indi-
cating that this parameter may be useful for predicting
ovulation.
Weick et al. (1973)
showed that plasma estradiol
levels peak 9
e
15 hours prior to the preovulatory LH surge
and approximately 30
e
40 hours before ovulation in the
same species. Of particular relevance to the use of either
ovarian hormone as a marker for ovulation are the obser-
vations by
Bielert et al. (1976)
, who noted that sexual
interaction increased between heterosexual pairs in daily
time-limited matings that coincided with the preovulatory
estradiol peak.
FIGURE 8.1
Perineum of an adult baboon at two different stages of
the menstrual cycle. (a) Maximum turgescent stage characterized by full
distention of the perineal skin which has a smooth, shiny appearance and is
a deep, intense red color. (b) Late turgescent stage identified by a loss of
turgidity and color and an increase in perineal wrinkles.
