Biomedical Engineering Reference
In-Depth Information
An increase in plasma volume compared with red cell
mass occurs in nonhuman primates throughout gestation.
This hydremia of pregnancy is important in maintaining the
health of the fetus by ensuring adequate uterine perfusion.
An approximate 30% increase in blood volume has been
reported for M. mulatta (
Allen and Ahlgren, 1968
), with
increases in total volumes of red and white blood cells
(WBCs), hemoglobin, total plasma protein, and albumin;
all values decrease substantially at parturition. Other
studies have indicated a shift in the albumin:globulin ratio
and an increase in sedimentation rate and plasma fibrinogen
(
Allen and Siegfried, 1966; Knapp et al., 1974
). Neutro-
philia has also been observed beginning ~GD 50 (
Allen and
Siegfried, 1966
). Studies by
Spicer and Oxnard (1967)
also
showed a decrease in hemoglobin late in pregnancy that
was well correlated with reductions in mean corpuscular
hemoglobin, mean corpuscular hemoglobin concentration,
and iron and with an increase in mean corpuscular volume.
A further demonstration of changes both pre- and post-
partum was provided by
Switzer et al. (1970)
; packed cell
volumes decreased during the first trimester (attributed to
implantation bleeding) and again 72
e
96 hours post-
delivery. Sedimentation rates also increased during the
third trimester, with a peak 72 hours postpartum. Interest-
ingly, WBCs decreased mid gestation, with a reversed ratio
of lymphocytes: neutrophils during the second trimester;
eosinophils also decreased during the third trimester, with
lowest values detected at parturition.
Reference values for hematological parameters and
clinical chemistry screens from the CPRC rhesus (GD 45,
90, 135, 165; n
abortion (
Schiller et al., 1983
). It was hypothesized that this
lack of a decrease may be attributed to fetal
e
placental
dysfunction (i.e. decreased HDL-cholesterol utilization for
steroid biosynthesis).
The average total weight gain during pregnancy for
M. nemestrina has been reported to be 19% above the
preconception weight (
Goodlin and Sackett, 1983
). It was
also observed that individual animals lost from 5 to 10% of
their mean preconception weight during the first 45 days of
pregnancy. By GD 60, a body weight gain was initiated that
peaked at roughly GD 160. Maternal body weight changes
during pregnancy from the CPRC rhesus and long-tailed
macaque colonies are shown in
Figure 8.5
. Rhesus data
were collected periodically during gestation (GD 60, 90,
120, 150, and postpartum) from females participating in
chair-restrained blood pressure monitoring beginning on
GD 90. Long-tailed macaque body weights were collected
from sham controls (GD 20 to
150) hand-caught for oral
gavage during GD 20
e
50. Similar to observations in
M. nemestrina, a decline in body weight was observed prior
to GD 50 in the longtailed macaques.
Lunn (1983)
reported
on body weight changes throughout pregnancy in common
marmosets. Generally, females did not display reliable
gains over their pre-pregnant weights until approximately
GD 80.
>
Prenatal Mortality
Information on pregnancy loss in nonhuman primates is
largely provided by studies in the more commonly used Old
World species, particularly macaques and baboons.
Prenatal mortality occurs throughout gestation in these
species, but the level is particularly high during the very
early embryonic stages, when pregnancy confirmation may
be uncertain and/or unreliable. Assessment of the magni-
tude of early embryonic mortality is additionally compli-
cated by the occurrence of “placental sign” (implantation
bleeding), which is normally seen in macaques during early
pregnancy. Morphological examinations of normal and
abnormal embryos in the rhesus monkey (
Heuser and
Streeter, 1941
) and baboon (
Hendrickx and Binkerd, 1980
)
as well as the chimpanzee (
Heuser, 1940
) have provided
information on embryonic death during the peri-implanta-
tion period. These studies indicate preimplantation losses
of 26.3 and 25.0% for rhesus monkeys and baboons,
respectively. Corresponding values during the post-
implantation period (approximately GD 10
e
22) have been
estimated at 14.3% in baboons, 28% in rhesus monkeys,
and 50% in chimpanzees.
During the subsequent period of organogenesis
(approximately days 20
e
50), the incidence of embryonic
loss for several nonhuman primates is significantly lower
than in the peri-implantation period. Microscopic exami-
nation of embryos of five Old World species (green
¼
13) and long-tailed (GD 25, 50, 75, 100;
n
10) macaque colonies are presented in
Tables
8.11
e
8.14
. For both species, samples were collected from
unanesthetized females in their cages (from an arm or leg
extended out of a partially opened door). In contrast to
finding in the previously cited studies, the samples indi-
cated only marginal changes in all parameters. These
differences may be attributed to the methods used for
collection and to the frequency of sampling. For clinical
chemistry screens, rhesus showed a minor increase in
blood urea nitrogen (BUN), glucose, and alkaline phos-
phatase (ALP) and a decrease in albumin and total
proteins at term. Marginal decreases were also observed
for carbon dioxide, potassium, and
g
-glutamyltransferase.
On GD 100, the long-tailed macaques showed reductions
in BUN, total proteins, and alkaline phosphatase (ALP).
Of interest are studies performed in M. nemestrina that
specifically addressed the effects of pregnancy on high-
density lipoprotein (HDL) concentrations. Although HDL
decreased (
Schiller et al., 1983
), increases in low density
lipoproteins (LDL) were noted in late pregnancy (
Rudel
et al., 1981
). In addition, HDL levels were predictive of
pregnancy outcome since no changes in HDL were
observed in pregnancies that
¼
resulted in spontaneous
