Histomorphometric and scanning electron microscopic analyses were performed on 74 embryos and fetuses and 20 sheep (early postnatal to adult age). Histologic differentiation of the omasum took place at 33 days of fetal life, with the appearance of first-order laminae. Second-, third-, and fourth-order laminae appeared at 39, 50, and 59 days, respectively. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life, decreasing quantitatively until birth, before subsequently stabilizing in postnatal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Growth curves and formulas were constructed for each tissue layer. Initial tests involved multiplicative (y = axb), exponential (y = EXP [a + bx]), linear (y = a + bx), and polynomial models [y = a + bx + cx(2) + dx(3)].

Histomorphometric and scanning electron microscopic analyses were carried out on 74 embryos and fetuses and 20 sheep (early postnatal to adult age). Histodifferentiation of the rumen took place at 33 days of fetal fife. Ruminal pillars were observed at 42 days, and at 61 days, ruminal papillae appeared as evaginations of the epithelial stratum basale. Neutral mucopolysaccharides first appeared in epithelial cells at 46 days of fetal life; thereafter, numbers decreased gradually and subsequently stabilized in postnatal life. Acid mucopolysaccharides, mucins, and mucoid compounds were not detected. Age and diet were recognized as factors that determine the structure of the ruminal mucosa. Growth curves and formulas were set out for each tissue layer.

Selenium concentration was measured in paired maternal blood samples and fetal liver specimens collected at a San Joaquin County, Calif, slaughterhouse (beef = 19, dairy = 54) and from bovine aborted fetuses submitted to the California Veterinary Diagnostic Laboratory System (CVDLS; beef = 20, dairy = 20). Of the slaughterhouse samples and specimens, dairy maternal blood selenium concentration was significantly (P < 0.001) higher (mean +/- SD; 0.22 +/- 0.056 micrograms/ml) than that for beef breeds (0.137 +/- 0.082 micrograms/ml). The CVDLS mean maternal blood selenium concentration for the dairy-breed samples (0.192 +/- 0.028 micrograms/ml) was similar to that for the slaughterhouse dairy-breed samples, but was greater than that for the slaughterhouse beef-breed samples. Slaughterhouse mean fetal liver selenium content also was higher (P < 0.001) for the dairy breeds (0.777 +/- 0.408 micrograms/g), compared with the beef breeds (0.443 +/- 0.038 micrograms/g). Mean fetal liver selenium content for slaughterhouse specimens was higher (P < 0.002) than that for the CVDLS specimens (beef, 0.244 +/- 0.149 micrograms/g; dairy, 0.390 +/- 0.165 micrograms/g). At the CVDLS, dairy fetal liver content was greater (P < 0.001) than that for beef breeds. Mean ratio of fetal liver selenium content to maternal blood selenium concentration was 3.53 +/- 1.89 for dairy breeds at the slaughterhouse (liver-to-blood correlation [r] = 0.38), and was 2.11 +/- 1.00 for dairy breeds at the CVDLS (r = 0.31) and 3.43 +/- 1.50 for beef breeds (r = 0.58). Both slaughterhouse breed ratios were significantly (P < 0.002) greater than the CVDLS dairy-breed ratio. On the basis of these results, breed and source location should be taken into account when interpreting selenium values. Fetal liver selenium content should only be used as a screening test and combined with whole blood selenium concentration from clinically normal herdmates to evaluate herd selenium status.

Objective--To evaluate the effects of diethylstilbestrol (DES) or alpha-zearalanol (zeranol) on fetal development, gestation duration, and number of offspring. Design-Study effects of prenatal administration of DES or zeranol on various pre- and perinatal variables in an experimental group of mice, compared with effects in a control group. Animal--Pregnant NMRI mice. Procedure--Diethylstilbestrol or zeranol (150 mg/kg of body weight) or vehicle (controls) was administered sc to pregnant mice on days 9 and 10 of gestation. Fetuses from pregnant mice of each group were counted and weighed, and their size and head length were recorded. Additional pregnant mice delivered their fetuses naturally, and pups from each group were counted and their sex was determined. At the end of gestation, abortions were evaluated. All data were statistically analyzed. Results--Mean number of fetuses was significantly lower (P < 0.0001) in DES-treated (4.59 +/- 0.48) than in control mice (8.33 +/- 0.49). Both estrogenic substances significantly reduced fetal size and weight (P < 0.0001), compared with control mice. Diethylstilbestrol significantly increased abortion frequency (P < 0.0001) and gestation duration (P < 0.0001), compared with values for control mice. A reduced number of live pups (P < 0.0001) from pregnant mice administered DES (5.48 +/- 0.38) or zeranol (5.97 +/- 0.49) was observed, compared with control mice (8.52 +/- 0.50), because of reduced number of male offspring (P < 0.0001). Conclusions--Diethylstilbestrol or zeranol administered during mid-pregnancy leads to decreased fetal weight and size and lower numbers of male offspring at birth. Likewise, DES induced a significant increase in abortions and gestation duration.

Immunoreactivity for 28 kd vitamin D-dependent calcium-binding protein (calbindin-D28k) has been localized in the germinal epithelium and cells surrounding oogonia and oocytes (future granulosa cells) of developing and growing ovaries of chicken embryos. The protein first appeared prominently in the germinal epithelium of the developing left ovary in 8-day embryos. At the twelfth day of incubation, cells surrounding oogonia and oocytes reacted intensely for calbindin-D28k. The number and intensity of calbindin-D28k-containing cells increased in both types of cells as the embryos further developed. Calbindin-D28k remained in the germinal epithelium throughout the study period observed (up to 10 weeks). However, the protein was present transiently in the future granulosa cells. It gradually decreased after hatching, and was virtually absent from granulosa cells in a 10-week old chicken. Compared with the known process of onset of sexual development, these results indicated possible involvement of calbindin-D28k in the early phases of oogenesis in chicken ovaries.

Both ovaries from 88 bovine fetuses in the fifth month or later of gestation were studied histologically to determine the prevalence, origin, and time of appearance of atretic corpora lutea (ACL). Ovaries from 36 (41%) fetuses had ACL; fetuses < 6 months of gestation did not have ACL. Six fetuses had more than 25 ACL, but there was no apparent relationship between fetal age and number of ACL. Formation of ACL involved disintegration of the stratum granulosum of secondary follicles, concomitant with proliferation and invasion by vascularized elements of the theca. Fully developed ACL consisted of a large primary oocyte surrounded by a prominent zona pellucida and encased in a well-vascularized, largely thecal, fibrocellular wall. They measured approximately 0.5 to 1.0 mm in diameter. Empty, collapsed zona pellucidas were seen in many of the degenerating ACL.

Fetal infectivity of Ehrlichia risticii was investigated in 19 ponies that were E risticii negative on the basis of results of an indirect fluorescent antibody (IFA) test. Thirteen pregnant ponies were infected by IV administration of E risticii between 90 and 180 days of gestation. Six pregnant ponies served as noninfected controls. Each infected pony had clinical signs of equine monocytic ehrlichiosis, was confirmed to be ehrlichemic, and developed an IFA titer to E risticii. Two infected ponies became recumbent, were unresponsive to supportive care, and were euthanatized. After recovery from clinical illness, the remaining ponies were observed throughout gestation for reproductive abnormalities. On abortion, each fetus was necropsied and tissue specimens from the liver, bone marrow, spleen, colon, and mesenteric lymph nodes were inoculated into canine monocyte cell cultures. Six infected ponies aborted at a mean 217 days of gestation, which was between postinoculation days 65 and 111. Five fetuses were recovered for evaluation, and E risticii was isolated from 4 of them. All 5 fetuses recovered had similar histologic findings, including enterocolitis, periportal hepatitis, and lymphoid hyperplasia with necrosis of the mesenteric lymph nodes and spleen. All fetuses tested negative for IgG to E risticii, although 3 had low IgM titer to E risticii. The remaining 5 infected ponies had normal parturition. Presuckle IFA titer to E risticii was measured in 4 of the term foals, and results for 3 were positive. Two foals from infected ponies were monitored for 6 months and daily gain in body weight was comparable to that of a control foal. None of the control ponies became ill or seroconverted during the clinical illness phase, and none aborted throughout gestation. Two control ponies seroconverted to E risticii 6 weeks before parturition. Results of this study indicate that E risticii is a primary abortifacient under experimental conditions.

The left ovary of chicken embryos was removed and incubated in culture medium with a thymidine analogue, bromodeoxyuridine (BrdU), in vitro. In addition, fertile chicken eggs were injected with BrdU via the extraembryonic vessels and incubated for 24 hours. The ovaries were then processed for immunohistochemical localization of calbindin-D28K (a 28-kd vitamin D-dependent calcium-binding protein) and BrdU. Calbindin-D28K was detected in the germinal epithelium and in cells surrounding the oogonia and oocytes (future granulosa cells) of the embryonic chicken ovary. However, Brdu was observed in the nucleus of the oogonia and oocytes of the chicken embryonic ovaries. Comparison of the 2 adjacent sections, immunostained for calbindin-D28K and BrdU consecutively, indicated that BrdU, the marker for cell proliferation was not detected in calbindin-D28K-containing cells, namely, germinal epithelium and future granulosa cells, in the ovary of chicken embryos. These results suggested that calbindin-D28K-containing cells in the ovary were not in the process of cell division during the 24-hour incubation of chicken embryos.

Akabane virus (AKV) strain OBE-1 was inoculated IV into 17 pregnant sheep. Ten fetuses infected at 29 to 45 days of gestation and examined 29 to 30 days later had AKV antigen in the following groups of cells: neuroglial cells in the brain and spinal cord, ganglion cells in the cranial and abdominal ganglia, layer of ganglion cells in the retina, ganglion cells (Auerbach's plexus) in small intestine, hepatocytes, cells in the arterial wall of mesenteric membrane, and trophoblast cells in the placenta. Prior to detection of circulating virus-neutralizing antibody, immunoglobulin-containing cells were found initially at 59 days of gestation in the peripheral portion of white pulp tissue in the spleen. After that, numbers of immunoglobulin-containing cells gradually increased. These results indicated that AKV may have strong affinity for neuronal and ganglional cells in infected fetuses and immunoglobulin-containing cells might be considered the earliest immunologic response to AKV replication in the fetus.

Five cows in the last month of gestation, provided with uterine electrodes and in which catheters had been chronically installed in the fetal aorta, were used to study patterns of fetal heart rate (FHR) and the influence of periods of myometrial electrical activity during gestation (contractures) on FHR. The FHR was calculated by counting the number of blood pressure pulses on the tracings during alternate periods of 12 seconds. Three 1-hour recordings without contractures and 10 recordings during the time of a contracture were randomly selected for each cow. The calculated data points were plotted on a graph to display FHR patterns. In 41 periods associated with single contractures, FHR data points were taken every 72 seconds. Changes in absolute and relative FHR in these periods were determined to analyze a possible effect of contractures on FHR. Three types of variation in FHR patterns could be distinguished: a short-term, low-amplitude variation of basal FHR; a second type in which the duration was < 4 minutes and the amplitude was greater than or equal to 15 beats/min; and prolonged periods with increased or decreased FHR values (> 4 minutes and greater than or equal to 15 beats/min). The relationship between these types of variation and fetal activity states remains to be established for cows. During the 60 hours of recordings that were analyzed, a period of several minutes during which FHR values were extremely high (> 180 beats/min) was found 3 times. There were no significant differences in absolute or relative FHR before, during, or after a contracture.