Viral contamination of bovine fetal lung cultures and bovine fetal serum

Commercial bovine fetal serum (BFS) and bovine fetal lung (BFL) cells were tested for viruses. The only virus detected in any samples was noncytopathogenic bovine viral diarrhea virus (BVDV). Of 37 BFL cultures initiated, 34 were negative for BVDV, 1 was positive, and 2 were suspicious in that the source of BVDV contamination was not certain. Of 9 lots of irradiated sera tested, 1 (10%) was positive for BVDV; of 21 lots of nonirradiated sera tested, 13 (62%) were positive for BVDV. As judged by intensity of fluorescence in infected cultures, some cell strains were much more susceptible to BVDV than other strains. Heat inactivation of serum at 56 C for 30 minutes was found to be an unreliable method of eliminating BVDV from sera.     

The concentration of bovine placental lactogen and the incidence of different forms in fetal cotyledons and in fetal serum

The concentration of bovine placental lactogen (bPL) was determined in fetal placentomes, allantoic fluid, amniotic fluid, maternal and fetal plasma throughout pregnancy. In addition, chromatofocusing chromatography was used to separate the different forms of bPL found both in fetal serum and in placental homogenates in order to determine whether the different forms that have been reported to exist in the cotyledon are also found in the fetal circulation. Reproductive tracts were collected from cows between 109 and 247 days of pregnancy. The concentration of bPL in the fetal cotyledonary tissue was measured by both radioreceptor assay and radioimmunoassay, both assays showed that the concentration of bPL in the fetal portion of the placentomes remained constant throughout the period of pregnancy tested. The mass of the placenta increased approximately 10-fold during the period of study but the concentration of bPL in the maternal plasma was low (0.9±0.1 ng/ml) at all stages of pregnancy tested. The mean concentration of bPL (Mean ± S.E.M.) in amniotic and allantoic fluid was 0.4±0.1 and 1.2±0.2 ng/ml respectively. Fetal blood contained the highest concentrations of bPL, from 11.6 to 18.4 ng/ml, and the concentration tended to decrease with advancing gestation (slope = 0.07, P = 0.001). Several forms of bPL were found in the fetal circulation; however, a higher percentage of forms with more acidic isoelectric points were found in the fetal serum than in placental homogenates. These results suggest that either some forms of bPL are more stable or that the hormone isolated from placental tissue is not representative of the final secreted product.     

Uterine and fetal monitoring in the bitch.

The use of uterine and fetal monitoring improves the outcome of canine obstetrics. Much of the guesswork of managing whelping can be eliminated. At normal term, absolute indications for cesarean section are detected with monitoring, before multiple fetal deaths or any serious maternal compromise occurs. Bitches with previous history of cesarean section may be able to whelp vaginally successfully, having medical intervention based on monitoring. The anxiety level of owners during whelping is diminished, and the level of participation of the veterinarian improves.     

Ventricular wall thickness in the fetal dog.

Ventricular wall thickness of 21 50-to 60-day canine fetuses was determined by direct measurement with calipers. Measurements were made of the left and right ventricular walls and of the interventricular septum, perpendicular to the apico-basilar axis at the location just below the aortic valve, and midway between the coronary sulcus and the apex. Mean determiniations were used to characterize the wall thickne-s at the various levels. The right wall was found to be thickpreciable thickness differences between the septal and left wall at this location. At the level of the midventricular wall, the septal wall thickness exceeded that of the left and right wall. Left and right wall thickness at this level were similar.     

An invasive procedure for in utero fetal electrocardiology: recording of fetal electrocardiograms by applying electrodes through the uterus.

An in utero technique was developed that allows direct access to the canine fetus for experimentation. This procedure reduces the need for fetal manipulation and umbilical blood flow compromise and reduces fetal fluid loss. In pregnant bitches, uterine horns could be delivered through a ventral midline incision. By manipulating the fetal membranes, and positioning the fetuses through them, electrodes could be inserted subcutaneously in the fetuses. Electrocardiograms satisfactory for interpretation were obtained from as many as 4 fetuses in a bitch for periods up to postoperative week 3.     

Cholinergic reactivity of the bovine fetal ruminal wall in vitro

Strips of rumen wall from bovine fetuses were incubated in an organ bath with acetylcholine only (0.16 to 5.12 g/ml) or in the presence of neostigmine (0.20 g/ml) or atropine (0.05g/ml). The highest reactivity was observed in the period of 4.0–5.9 months of fetal age. This reactivity could be associated with the starting point of rumen papillary development.     

Proliferation of myogenic cells in the diaphragm of the fetal rabbit.

Diaphragms obtained from 40 fetal rabbits at gestational ages of 20, 22, 25 and 30 days were examined by light and transmission electron microscopes. The percentage of myogenic cells undergoing mitosis was calculated by counting mitotic nuclei in 1 micron sections. At 20 and 22 days gestation, myogenic cells (myoblasts and satellite cells) were actively proliferating with 2.66 +/- 0.41% (n = 15) and 2.18 +/- 0.20% (n = 23), of the cells in division, respectively. The myogenic cells undergoing mitosis appeared to be of both myoblasts and satellite cells at these stages of the development. The myotubes on day 20 of gestation contained a large number of lipid droplets and an abundance of glycogen particles which were reduced by day 22 of gestation. The mitotic rate on day 25 of gestation was reduced to 1.16 +/- 0.11% (n = 28). The muscle fibers were well differentiated at this stage and the majority of the dividing cells were considered to be satellite cells. In diaphragms from the full term fetuses (day 30), the mitotic rate was reduced to 0.31 +/- 0.05% (n = 24). It was suggested that myoblasts of the fetal rabbit diaphragm proliferated for the myotube formation during the earliest stage of the development (day 20 of gestation) and then the number of satellite cells increased after day 22 of gestation. Growth of the organ after day 25 of gestation appeared to be mostly due primarily to the hypertrophy and differentiation of the muscle fibers rather than proliferation of myoblasts.