Sonographic imaging of the bovine fetus

Transrectal sonography documenting the anatomical features of 71 bovine fetuses was performed between Day 30 and 10 mo of gestation. Sector scanners, which have a wider field of view into the depth of the uterus, were used, and it was found that most macroscopic organs were visible with B-scan ultrasound. The first organ detected around the end of the first month of pregnancy was the heart. The orbit, the stomach and the braincase were identified at Day 40. Most bones of the skeleton and the scrotum appeared around Month 3. Characteristic sonographic images of the head, neck, vertebral column, thorax, stomach, liver, kidneys, urinary bladder, limbs, scrotum-respectively teats, as well as the umbilical cord, amnion and allantois are described in this study.     

Early pregnancy diagnosis and embryonic and fetal development using real time B mode ultrasound in goats

Real time B mode ultrasound scanning was used for the diagnosis of early pregnancy and monitoring of embryonic and fetal development in goats. Estrus in 8 cyclic cross-bred does was synchronized using a single injection of PGF2α followed by mating with a buck. All the does were subjected to weekly transrectal (from day 14 of mating) and transabdominal ultrasonography (from day 28) up to the 4th month of gestation and once during the 5th month of gestation. Of the 8 animals, 6 does were confirmed pregnant. The embryonic vesicle was detected on day 21 and day 28 and the embryo proper on day 28, day 35 using the transrectal and transabdominal methods, respectively. Heart beat was observed as early as day 21 of gestation and it was recordable by day 28 using the transrectal approach. However, via transabdominal scanning the detection and recording of the heart beat was possible only on day 35 of gestation. Singles and twins were differentiated on day 35 and day 42 by the transrectal and transabdominal approaches, respectively. Placentomes as a circular ‘C’ shape structure was detectable on day 42 with an average diameter of 0.97 cm, using the rectal probe. Using the abdominal probe, placentomes were detectable on day 50 (average diameter of 1 cm of gestation). Skeletal structures such as the skull, rib cage and vertebral column were first viewed on day 56 in both approaches. A significant (P < 0.001) high correlation (r = 0.99) was recorded between the gestational age and head, thoracic and placentome parameters. It may concluded that the earliest identification of an embryonic vesicle (day 21) by transrectal scanning and confirmation of its viability by fetal heart beat (day 28) were the most reliable ultrasonographic features for early pregnancy diagnosis in goats. Transabdominal ultrasonographic measurements of placentome, head and thoracic diameter may be of use in the assessment of fetal age.     

Early pregnancy diagnosis and embryonic and fetal development using real time B mode ultrasound in goats

Real time B mode ultrasound scanning was used for the diagnosis of early pregnancy and monitoring of embryonic and fetal development in goats. Estrus in 8 cyclic cross-bred does was synchronized using a single injection of PGF2α followed by mating with a buck. All the does were subjected to weekly transrectal (from day 14 of mating) and transabdominal ultrasonography (from day 28) up to the 4th month of gestation and once during the 5th month of gestation. Of the 8 animals, 6 does were confirmed pregnant. The embryonic vesicle was detected on day 21 and day 28 and the embryo proper on day 28, day 35 using the transrectal and transabdominal methods, respectively. Heart beat was observed as early as day 21 of gestation and it was recordable by day 28 using the transrectal approach. However, via transabdominal scanning the detection and recording of the heart beat was possible only on day 35 of gestation. Singles and twins were differentiated on day 35 and day 42 by the transrectal and transabdominal approaches, respectively. Placentomes as a circular ‘C’ shape structure was detectable on day 42 with an average diameter of 0.97 cm, using the rectal probe. Using the abdominal probe, placentomes were detectable on day 50 (average diameter of 1 cm of gestation). Skeletal structures such as the skull, rib cage and vertebral column were first viewed on day 56 in both approaches. A significant (P < 0.001) high correlation (r = 0.99) was recorded between the gestational age and head, thoracic and placentome parameters. It may concluded that the earliest identification of an embryonic vesicle (day 21) by transrectal scanning and confirmation of its viability by fetal heart beat (day 28) were the most reliable ultrasonographic features for early pregnancy diagnosis in goats. Transabdominal ultrasonographic measurements of placentome, head and thoracic diameter may be of use in the assessment of fetal age.     

Natural outcome and ultrasonic identification of equine fetal twins

The natural outcome of bilateral twins (one in each uterine horn) that were viable on Day 40 was studied in 15 pony mares. Fetuses were monitored by transrectal ultrasonography until the outcome was determinable. One fetus (2 mares) or both fetuses (8 mares) died (cessation of heartbeats) during Months 2 and 3. Loss of fetuses was externally observed in 4 additional mares during the late fetal stage (Months 8 to 11); 2 mares lost 1 fetus and 2 lost both fetuses. Birth of 2 live foals occurred in only 1 of 15 mares (7%) First day of detected apposition between portions of the 2 allantochorions was studied daily on Days 40 to 51 in 7 of the 15 mares. Apposition was first detected on mean Day 46.3 (standard deviation: +/-3.1). In these 7 mares, death of 1 fetus (2 mares) or both fetuses (2 mares) occurred 1 or 2 days after the first day of apposition of allantochorions; no deaths occurred before the day of apposition. Each mare with loss of one fetus during this time gave birth to a living foal. The only structure indicative of twins that was consistently detected ultrasonically during all examinations was the common membrane resulting from the area of apposition between the 2 allantochorions. The common membrane is herein designated as the twin membrane because of its apparent diagnostic potential even in late pregnancy when the presence of the 2 fetuses may not be detected directly. Thickness of the twin membrane reached approximately 3 mm at Month 7 and thereafter gradually increased to 15 mm near the end of pregnancy. Two layers of the membrane (1 for each allantochorion) became distinct at Month 6 and Month 8 with 5.0 MHz and 3.5 MHz transducers, respectively; the 2 layers were separated by a hypoechogenic layer.     

Malformations in rat fetuses induced by trypan blue

Malformations of fetuses obtained from Wistar rat dams treated with trypan blue during gestation were studied. Fetuses were examined on day 20 of gestation. One hundred and twenty-seven fetuses showed abnormalities of the external features, skeleton and internal organs, separately or in combination. External malformations were found in 108 fetuses. The most frequent external malformation was anomaly of tail. Spina bifida, club foot, exencephaly and anal atresia were also observed frequently. Skeletal malformations were detected in 48 fetuses. Deformity of vertebrae in the lumbar, sacral and/or caudal regions was found in 46 fetuses. Internal malformations were observed in 27 fetuses. Anomaly of heart and/or great vessels, hydrocephaly and micro- or anophthalmia were observed frequently. About 90% of the fetuses with skeletal malformations also showed some external malformations. In contrast, about 48% of the fetuses with internal malformations also had some external malformations. These results suggest that, for teratological study, internal examination is more important in detecting malformations of fetuses than skeletal examination.     

Teratologic studies on rat perinates and offspring from dams treated with ethylnitrosourea (ENU).

Ethylnitrosourea (ENU), a well known DNA alkylating agent, induces anomalies in the central nervous system (CNS), craniofacial tissues, limbs and male reproductive organs. Recently we clarified that excess cell death caused by apoptosis occurred in these organs and tissues of rat fetuses from dams treated with ENU at day 13 of gestation (GD13). In this study, we examined fetuses at GD21 and offspring at 10 weeks of age after ENU administration to pregnant rats at GD13 in order to clarify the relationship between ENU-induced apoptosis in the fetal tissues and teratogenicity of ENU. Severe intrauterine growth retardation was observed in the ENU group, and the body weight of the offspring in the ENU group was significantly lower than that of the control group throughout the experiment. In addition, a high incidence of microencephaly, ectrodactyly and curved caudal vertebrae was observed in the offspring from dams treated with ENU at GD13. Judging from the results of our previous and present studies, it was strongly suggested that ENU-induced apoptosis in rat fetal tissues may play an important role in the induction of anomalies in the corresponding tissues.     

Craniosynostosis and altered patterns of fetal TGF-beta expression induced by intrauterine constraint

Recent work has demonstrated that fusion of the calvarial sutures is mediated by locally elaborated soluble growth factors, including the transforming growth factor-betas (TGF-betas), leading some to speculate that external biomechanical forces play little role in suture development. Clinical evidence has long suggested, however, that fetal head constraint may play a critical role in the pathogenesis of many cases of nonsyndromic craniosynostosis. The purpose of these experiments was to test the hypothesis that intrauterine constraint leads to an alteration in normal patterns of TGF-beta expression and that these alterations are associated with craniosynostosis. Fetal constraint was induced by allowing C57Bl/6 murine fetuses to grow for 2.5 days beyond the normal 20-day gestation by performing uterine cerclage on the eighteenth day. Cranial suture morphology was examined in hematoxylin and eosin-stained sections and in cleared whole-mount specimens, double stained with alizarin red S and Alcian blue. Expression patterns of TGF-beta1 and TGF-beta3 were examined by immunohistochemical techniques. Gross and microscopic examination of the cranial sutures of 17 constrained fetuses revealed changes that ranged from narrowing to complete osseous obliteration of the coronal and squamosal sutures. All sutures of 14 nonconstrained control pups remained patent. Fetal head constraint was associated with increased TGF-beta1 immunoreactivity within the new bone and the underlying dura when compared with nonconstrained age-matched controls. TGF-beta3 immunoreactivity was associated with the dura underlying patent, nonconstrained sutures, whereas constraint-induced synostosis was characterized by down-regulation of dural TGF-beta3 expression. These experiments confirm the ability of intrauterine constraint to induce premature fusion of the cranial sutures and provide evidence that intrauterine head constraint induces the expression of osteogenic growth factors in fetal calvarial bone and the underlying dura.     

Immunohistochemical study on the fetal rat pituitary in hyperthermia-induced exencephaly

Hyperthermia of fetal rats is known to cause malformations of various organs including brain. The present study was carried out to investigate the effect of the hyperthermia-induced brain damages on the development of the adenohypophysis. Mother rats of day 9.5 of pregnancy were anesthetized and immersed in hot water (43 degrees C) for 15 min. At day 21.5 of gestation, fetuses were removed by caesarian section and examined for exencephaly. Hyperthermal stress induced varying degrees of exencephaly in 36% of surviving fetal rats. In extreme cases a considerable part of head was lost. Even in those fetuses with severe brain deformities, the hypophysial stalk and neural lobe were present though they were markedly underdeveloped. In exencephalic fetuses, no immunoreactive vasopressin was detected in the neural lobe of the hypophysis. Immunohistochemical examination of the adenohypophysis showed that exencephaly caused a marked decrease in the number of growth hormone (GH)-producing cells. Other types of hormone-producing cells appeared to be unaffected by brain anomaly. The reason for a decreased population of GH cells in exencephalic fetuses is discussed in relation to their adrenocortical hypotrophy.     

Developmental anomalies induced by all-trans retinoic acid in fetal mice: I. Macroscopic findings

The administration of a single dose of all-trans retinoic acid on day 8 of gestation to pregnant mice, ICR strain, led to malformed fetuses in all of the litters. All-trans retinoic acid (RA) was dissolved in olive oil and given in doses of 60 or 40 mg/kg of body weight. The control mice were given vehicle alone. Examination on day 18 of gestation of the fetuses exposed to 60 mg/kg showed various malformations, such as exencephaly, exophthalmus, micrognathia, agnathia, cleft palate, cleft lower lip, spina bifida, atresia ani, tail anomalies, agenesis of the kidneys, or hydronephrosis. In the fetuses exposed to 40 mg/kg, isolated cleft palate was much more common than in those exposed to 60 mg/kg. Double-stained preparations of bone and cartilage showed cranio-facial anomalies and axial skeletal anomalies: a- or hypogenesis of palatine or maxillary bones, tympanic ring, squamosal temporal bone or otic ossicles in cartilage, and fusion of basioccipital to basisphenoid and maxilla, zygomatic and mandibular bones; a- or hypogenesis of caudal vertebrae and supernumerary thoracic and lumbar vertebrae. These results indicate that anomalies comparable to those seen in the infants of mothers treated with isotretinoin, 13-cis retinoic acid, during pregnancy can also be induced in mice and suggest that the site affected by RA may be neural crest cells, including those in the cephalic and caudal regions, and cells committed to somitic mesoderm in the trunk region.     

Experimental study of umbilical cord length as a marker of fetal alcohol syndrome

Umbilical cord length has long been investigated as a potential marker of intrauterine events that may place the neonate at risk for future adverse developmental sequelae. Experimentally, significantly shortened cords have been reported in association with prenatal exposure to common drugs of abuse. This study in rats reports the time course of effects on umbilical cord length of a daily maternal ethanol gavage (3,200 mg/kg) from gestational day 6 through termination of pregnancy at either day 17, 18, 19, or 20. A total of 786 fetuses derived from 60 litters were examined. Control fetuses demonstrated a linear increase in umbilical cord length and body weight gain during late gestation, findings that support previous studies. The body weights of the ethanol-exposed fetuses were reduced significantly on all gestational days examined, indicating intrauterine growth retardation, a characteristic of fetal alcohol syndrome. Similarly, acute fetal akinesia as well as long-term sequelae stemming from impaired neurological development would result from the elevated blood ethanol levels achieved in this study. The umbilical cords of ethanol-exposed fetuses were significantly shorter on gestational days 19 and 20 in comparison to their controls, while cord lengths on days 17 and 18 were not shortened significantly. A stretch hypothesis has been proposed suggesting that the degree of fetal activity is the main determinant of umbilical cord length. In rats, there is a physiologic diminution of the volume of amniotic fluid (oligohydramnios) in late gestation (day 19 to term), which restricts fetal movements but does not appear to alter the linear relationships between gestational age and cord length in controls, thus arguing against the stretch hypothesis. However, cord lengths in the ethanol-exposed fetuses plateaued in late gestation, suggesting possible adherence to a stretch hypothesis. This dichotomy is discussed emphasizing fetal growth and activity as well as intrauterine space.     

Clinical,ultrasonographic, and endocrinological studies on donkey pregnancy

Although donkey breeding has gained new interest in the past two decades, knowledge about donkey reproduction is still scarce, particularly on jenny pregnancy. The aim of this study was to describe the ultrasonographic and endocrine profiles of the physiological pregnancy in the jenny. The study was performed on 12 pregnancies of 7 Amiata donkeys from Day 10 after ovulation to delivery. Because three pregnancies, respectively at weeks 42, 44, and 45, were considered pathologic and treated pharmacologically, data collected from 2 weeks before diagnosis to the end of pregnancy were removed from the analysis. Average length of the normal pregnancies was 353.4 ± 13.0 days (range, 339–370 days). Timing, dimensions, and development during the first phases of embryonic growth, evaluated using transrectal ultrasound, were similar to that previously described in jennies and mares: first detection of embryonic vesicle was at 11.8 ± 1.3 days of gestation and diameter was 6.5 ± 1.9 mm, loss of spherical shape occurred at 18.5 ± 1.4 days, and embryo and heart beat were first seen at 22.0 ± 1.1 and 25 ± 1.1 days, respectively. The intrauterine growth in the second half of pregnancy, evaluated using the transrectal and transabdominal approach, also showed strong positive correlations, similar to that reported for the mare. The trends of the combined thickness of the utero-placental unit and the echogenicity of the amniotic and allantoic fluids are examples. The diameters (mm) of fetal chest, eye orbit, and aorta increased throughout pregnancy and were 40.6 ± 2.9, 8.7 ± 1.5, and 3.5 ± 0.7, respectively, at week 13, and 190.9 ± 12.0, 21.4 ± 1.5, and 30.6 ± 1.8 at the last evaluation before parturition. In contrast, heart rate decreased as pregnancy progressed. Regression analyses between these parameters and day of gestation were statistically significant (P < 0.001). All fetuses consistently showed some intrauterine activity. Maternal plasma progestagens and estrone sulfate concentrations followed a pattern similar to that seen in mares, although the prepartal progestagen peak was lower in jennies. This study provides a range of ultrasonographic and endocrine values for normal pregnancy in jennies.     

Radiation-induced developmental abnormalities of the brain ventricles in the golden hamster

The dysontogenesis of the brain ventricle system of golden hamster fetuses was studied after X-ray irradiation of the mother at different stages of pregnancy. Groups of gravid hamsters were irradiated with a single dose (200 R) on either the 6th, 8th, 10th or 12th day of gestation. The fetuses were removed 1 day before birth. The most prominent finding in all stages of development was the dilatation of the brain ventricles. In addition to hydrocephalus, hematocephaly was also found in some cases. Furthermore, a widening of the central canal of the spinal cord with hemorrhagic content could sometimes be observed. Ependymal ectopies and subependymal rosettes occurred more frequently when irradiation was given in the late fetal period. The experimental findings demonstrate that after irradiation of the mother animal, malformation of the brain may be produced during the whole intrauterine period of development. The pattern and extent of malformation depend not only upon the dose of irradiation but also upon the stage of development at which irradiation was given.     

Three-dimensional ultrasound imaging of the equine fetus

The objective was to assess the optimal procedure for real-time, three-dimensional (3D) ultrasound (US) imaging for assessing the equine fetus during the first half of gestation and the possibility of using 3D US imaging of the equine fetus in clinical applications. Seventeen pregnant mares were examined by 3D US between Days 35 and 180 of gestation. Abdominal and endo-vaginal real-time 3D transducers used in human medicine were used for transrectal and transvaginal examinations, respectively. Images were recorded by both 3D stationary and real-time movies. In a comparison of four methods, transrectal examination with a bulb-shaped abdominal 3D transducer enabled the equine fetus to be clearly visualized, and did not require sedation of the mare. Therefore, this approach was the most suitable procedure for examining equine fetuses during the first half of gestation. Each scan required only a few seconds and an entire examination took <10 min in total. The 3D volume image was easy to restore after the examination and could be rotated to any angle the examiner desired. Fetal surface structures, including the head, body, limbs, and genital tubercle, were observed as 3D images which enabled fetal development to be characterized. For early (Days 60-70), but not later (Days 90-150) periods, 3D ultrasonography was not able to evaluate fetal structure in detail as well as conventional 2D ultrasonography. In conclusion, 3D ultrasonography of the equine fetus was a valuable adjunct to 2D ultrasonography and a convenient modality for more detailed assessment of fetal structures.     

Umbilical artery doppler sonography in Saanen goat fetuses during singleton and multiple pregnancies

The objective of this study was to evaluate the blood flow from the umbilical artery (UA) in healthy pregnant goats. Doppler sonography examinations were performed every two weeks in Saanen goats with a singleton (n = 5) or multiple (n = 4) pregnancy from 40 to 145 days of gestation. Fetal heart rates (FHR), pulsatility index (PI), and resistance index (RI) were recorded from the mid-cord site of the free-floating umbilical cord. FHR decreased gradually as the pregnancy progressed and significantly decreased during the last two examinations of all fetuses (P < 0.05). The mean PI level was dramatically different (P < 0.05) until 85 days of gestation, after which it reached a plateau level until parturition. Similar to PI, RI decreased by 85 days of gestation (P < 0.05), and decreased again by 130s gestation. No reverse or absent end-diastolic flow were observed in fetuses during any examinations. When comparing singleton and multiple pregnancies, there were no significant differences in UA pulsatility or resistance in fetuses seen. The middle of the second trimester was observed to be a threshold stage for indices in the pattern of caprine pregnancy.In conclusion, this work provides additional values that might be useful when evaluating singleton and multiple pregnancies, and may be evaluated in further studies regarding fetal monitoring.     

Ultrasonographic evaluation of the equine placenta by transrectal and transabdominal approach in the normal pregnant mare

The objective of this study was to determine normal variations in the utero placental thickness during mid- and late gestation in the mare. Normal, healthy pregnant mares (n = 9) were examined monthly from 4 mo of gestation until parturition by transrectal and transabdominal ultrasonography. At each examination, the combined thickness of the uterus and the placenta (CTUP) was measured at the placento-cervical junction (transrectally) and at the uterine body or the uterine horns (transabdominally). In addition, the echogenicity of the amniotic and allantoic fluids was evaluated by transrectal ultrasonography. Following parturition and expulsion of the fetal membranes, the allantochorion was measured and visually examined for abnormalities. At all examinations, both transrectal and transabdominal, the chorioallantois and the uterus were indistinguishable from each other on the ultrasound image. The CTUP, measured by transrectal ultrasonography did not change between 4 and 8 mo of gestation, but increased significantly for each month between 10 and 12 mo of gestation (P < 0.001). A change in the CTUP was detected between months when measured by transabdominal ultrasonography, but no distinct pattern in these changes was observed. No correlation was found between transabdominal and transrectal measurements of the CTUP. The echogenicity of the amniotic and allantoic fluids did not consistently change over time during mid- and late gestation. The amniotic fluid was more echogenic than the allantoic fluid at most examinations from 6 mo of pregnancy and throughout gestation (P < 0.05). It was concluded that transrectal ultrasonographic examination to assess the CTUP and the echogenicity of the fetal fluids is superior to the transabdominal approach. We suggest that transrectal ultrasonographic examination should be added to current diagnostic tools during late gestation and that it be part of the biophysical profile of high risk equine pregnancies.     

Evidence for placental abnormality as the major cause of mortality in first-trimester somatic cell cloned bovine fetuses

The production of cloned animals is, at present, an inefficient process. This study focused on the fetal losses that occur between Days 30-90 of gestation. Fetal and placental characteristics were studied from Days 30-90 of gestation using transrectal ultrasonography, maternal pregnancy specific protein b (PSPb) levels, and postslaughter collection of fetal tissue. Pregnancy rates at Day 30 were similar for recipient cows carrying nuclear transfer (NT) and control embryos (45% [54/120] vs. 58% [11/19]), although multiple NT embryos were often transferred into recipients. From Days 30-90, 82% of NT fetuses died, whereas all control pregnancies remained viable. Crown-rump (CR) length was less in those fetuses that were destined to die before Day 90, but no significant difference was found between the CR lengths of NT and control fetuses that survived to Day 90. Maternal PSPb levels at Days 30 and 50 of gestation were not predictive of fetal survival to Day 90. The placentas of six cloned and four control (in vivo or in vitro fertilized) bovine pregnancies were compared between Days 35 and 60 of gestation. Two cloned placentas showed rudimentary development, as indicated by flat, cuboidal trophoblastic epithelium and reduced vascularization, whereas two others possessed a reduced number of barely discernable cotyledonary areas. The remaining two cloned placentas were similar to the controls, although one contained hemorrhagic cotyledons. Poor viability of cloned fetuses during Days 35-60 was associated with either rudimentary or marginal chorioallantoic development. Our findings suggest that future research should focus on factors that promote placental and vascular growth and on fetomaternal interactions that promote placental attachment and villous formation.     

Evaluation of false transrectal ultrasonographic pregnancy diagnoses in sheep by measuring the plasma level of pregnancy-associated glycoproteins

The present study was undertaken to investigate to what extent pregnancy diagnoses made by transrectal ultrasonography could be confirmed by measurements of plasma concentration of ovine pregnancy-associated glycoproteins (ovPAG). A total of 424 Awassi x Merino ewes were synchronized for estrus and examined by transrectal ultrasonography. In Experiment 1, the ewes (n = 156) were repeatedly scanned in a standing position on d 29, 36 and 50 of gestation. Similarly, the ewes (n = 268) in Experiment 2 were scanned on d 24, 29 and 34 of gestation, but these ewes were fasted for 12 h prior to the examination and the abdominal wall of each animal was lifted up by the hands of the assistant during the scanning. Blood samples were withdrawn after each transrectal ultrasonographic examination in both experiments. Ovine PAG concentrations were measured in plasma by a heterologous radioimmunoassay and the cut-off value for pregnancy was > or = 1 ng.mL-1. Based on the lambing performance, in Experiment 1, altogether 47 false negative and 38 false positive diagnoses were made by transrectal ultrasonography in 24 and 33 ewes, respectively between d 29 and 50 of gestation. In Experiment 2, altogether 8 false negative and 13 false positive diagnoses both were made in 7 ewes between d 24 and 34 of gestation. In both experiments, all ewes with false negative diagnoses had ovPAG concentrations higher than the threshold level for pregnancy diagnosis and all ewes with false positive diagnoses had ovPAG concentrations lower than the threshold of pregnancy. Furthermore, by the PAG-RIA test all lambed or aborted ewes (n = 63) were correctly diagnosed as pregnant and with three exceptions, all non-lambed ewes (n = 361) were correctly diagnosed as non-pregnant during the examined periods of both experiments.     

Role of primary and secondary maternal viremia in transplacental guinea pig cytomegalovirus transfer.

The modulation of the outcome of intrauterine guinea pig cytomegalovirus (GPCMV) infection by maternal viremia was investigated in the guinea pig model. Virus assay and in situ hybridization were used to study GPCMV infection of maternal blood, placentas, and fetuses following inoculation of pregnant guinea pigs by the subcutaneous, intracardiac, or intranasal route. Animals were inoculated in early gestation and were evaluated every 7 to 10 days throughout pregnancy. Although placental and fetal infections occurred in all groups examined, transfer of GPCMV to placentas and fetuses was most efficient in mothers inoculated subcutaneously. Primary viremia was followed by virus clearance from blood and by an episode of secondary viremia in the three groups of mothers examined. Placental and fetal infections in animals infected subcutaneously or intracardially were first detected at the time of primary viremia, persisted throughout gestation, and increased during secondary viremia. In contrast, placental and fetal infections in animals inoculated intranasally were demonstrated primarily during secondary viremia. Fetal infection was detected in all mothers with detectable primary and secondary viremia but in only 33% of mothers that experienced only primary viremia. These results suggest that secondary maternal viremia is associated with increased placental and fetal GPCMV infections.     

Morphology and morphometry of in vivo- and in vitro-produced bovine concepti from early pregnancy to term and association with high birth weights

This study was designed to characterize conceptus development based on pre- and postnatal measurements of in vivo- and in vitro-derived bovine pregnancies. In vivo-produced embryos were obtained after superovulation, whereas in vitro-produced embryos were derived from established procedures for bovine IVM, IVF and IVC. Blastocysts were transferred to recipients to obtain pregnancies of single (in vivo/singleton or in vitro/singleton groups) or twin fetuses (in vitro/twins group). Ultrasonographic examinations were performed weekly, from Day 30 of gestation through term. Videotaped images were digitized, and still-frames were used for the measurement of conceptus traits. Calves and fetal membranes (FM) were examined and measured upon delivery. In vitro-produced fetuses were smaller than in vivo controls (P < 0.05) during early pregnancy (Day 37 to Day 58), but in vitro/singletons presented significantly higher weights at birth than in vivo/control and in vitro/twin calves (P < 0.05). From late first trimester of pregnancy (Day 72 to Day 93), placentomes surrounding in vitro-derived singleton fetuses were longer and thinner than controls (P < 0.05). At term, the presence of giant cotyledons in the fetal membranes in the in vitro group was associated with a larger cotyledonary surface area in the fetal horn (P < 0.05). The biphasic growth pattern seen in in vitro-produced pregnancies was characterized by conceptus growth retardation during early pregnancy, followed by changes in the development of the placental tissue. Resulting high birth weights may be a consequence of aberrant placental development due to the disruption of the placental restraint on fetal growth toward the end of pregnancy.     

The effect of methylmercury on prenatal development and trace metal distribution in pregnant and fetal rats

Methylmercuric chloride (MetHg) at the dose of 2.5 mgHg/kg was administered by gavage every other day to pregnant rats from the sixth to the twentieth day of gestation. On the 21st day of gestation, females were sacrificed to allow the evaluation of embryotoxicity and the taking of analytical material. Copper, zinc, iron, and calcium were determined4 by AAS in brain, liver, kidneys, intestine, whole blood, and spleen of pregnant MetHg-exposed, nonpregnant and pregnant control females, and in fetuses as well as in placenta. Exposure of pregnant rats to MetHg brought about a decrease in the concentration of intestinal iron and calcium compared with control pregnant animals. In whole fetuses where the mother had been exposed to MetHg, the concentrations of calcium and iron were significantly decreased. The skeletal examination showed developmental retardation of fetuses in the MetHg group, which was reflected in enhanced frequency of delayed ossification of the sternebrae, os occipitale, and vertebrae. The copper level in the brains of fetuses from intoxicated mothers was significantly lower and the absolute brain weights were higher than in controls.