Antibody repertoire development in fetal and neonatal piglets. IV. Switch recombination, primarily in fetal thymus, occurs independent of environmental antigen and is only weakly associated with repertoire diversification.

The epitheliochorial placenta of swine is considered a barrier to Ag and selective transport of IgG, so this species should be an excellent model with which to determine whether switch recombination is Ag dependent. Analysis of Ig levels and Ig isotype profiles in >150 normal and virus-infected fetuses from 38-110 days of gestation (DG) suggested that IgG, IgA, and IgM were most likely the result of de novo fetal synthesis. Although transcripts for IgM could be recovered at DG 50 (114 DG is full gestation) in all major fetal lymphoid tissues, those for IgG and IgA first became prominent at 60 DG in thymus, and transcription and spontaneous secretion became especially pronounced in this organ in older fetuses. Data on transcription, secretion, and serum isotype profiles suggest that although all fetal IgA and IgM may result from de novo synthesis, some IgG may result from low-level selective transport. The complementarity-determining region 3 spectratypes of thymic IgA and IgG transcripts at 70 and 90 days, respectively, were as polyclonal as that of IgM, indicating a broad repertoire of switched B cells although the VDJs transcribed with these switched isotypes in normal fetuses were not diversified in comparison to those from animals exposed to environmental Ags such as age-matched, virus-infected fetuses, colonized isolator piglets, and conventional adults. However, VDJs expressed with switched isotypes were more diversified than those expressed with IgM. Thus, switch recombination in fetal life does not appear to be driven by environmental Ag and is only weakly coupled to VDJ diversification. These findings, and the fact that the oligoclonal IgA and IgM repertoires in a noninductive site of the mucosal immune system (parotid gland) become polyclonal in piglets reared germfree, suggest that initial expansion of the switched cells in the B cell compartment of fetal and neonatal piglets is not driven by environmental Ag.

Abortifacient effects of a unique class of vasoactive lipids from Pinus ponderosa needles.

Pinus ponderosa needle (PN) ingestion by late pregnant cows results in decreased uterine blood flow, premature parturition, and retained placentae. Further, plasma from PN-fed cows increases caruncular arterial tone (i.e., induces prolonged contraction) in an isolated perfused bovine placentome. A novel class of vasoactive lipids was isolated and identified using a bovine placentome assay-guided fractionation of CH2Cl2 extracts of PN. Placentome perfusion tests indicated that 1-12-dodecanedioyl-dimyristate (14-12-14) was the most potent of the PN lipids for increasing caruncular arterial tone. Late pregnant guinea pigs (GP) were used to evaluate the abortifacient activity of these vasoactive lipids. In Study 1, on d 50 of gestation, part of the control diet was replaced with chopped PN (Diet A) or chopped PN subjected to sequential extraction with diethyl ether (Et2O; Diet B); Et2O and CH2Cl2 (Diet C); and Et2O, CH2Cl2, and methanol (Diet D). The GP on Diets A and B exhibited shorter (P<.01) gestation lengths and reduced (P<.01) pig birth weights than GP on the control diet or Diets C and D. Further, only GP on Diets A and B exhibited retained placentae. In Study 2, on d 50 of gestation, part of the control diet was replaced with chopped PN that had been subjected to exhaustive CH2Cl2 extraction and then infiltrated with either CH2Cl2 alone (Diet E), CH2Cl2 containing 14-12-14 (Diet F), or CH2Cl2 containing isocupressic acid (Diet G); then solvents were evaporated. The GP consuming Diet F had shorter (P<.05) gestation lengths and reduced (P<.05) pig birth weights than did GP consuming Diets E or G. The GP consuming Diet F also exhibited a high incidence of retained placentae. These data provide evidence that a unique class of vasoactive lipids in PN exhibit abortifacient activity in guinea pigs.

Pine needle abortion in cattle: effects of diet variables on consumption of pine needles and parturition response.

Cows that consume needles from Pinus ponderosa (PN) abort, but little is known about variables that affect consumption or response. These experiments were conducted to test the effects of several variables on pine needle-induced abortion. Cows were placed on experiment at 250 d of pregnancy and were either given ad libitum (AL) access to PN separate from other feed sources or the PN were ground and fed (2 kg.cow-1.d-1) mixed with the diet. In Exp. 1, cows were assigned to a 2 x 2 factorial experiment with adequate (AP) vs high-protein (HP) diets and no straw vs AL straw (S). All cows ate PN and aborted, and there were no effects (P > .5) on interval to parturition (IP). Consumption of PN (kg/d) was increased by HP (P < .1). In Exp. 2, cows were assigned to five treatments to test the effects on response to PN of magnesium supplementation, weathering the PN, and using silage rather than hay as the basal diet. Consumption of PN shortened IP (P < .01), but magnesium, weathering PN, and silage-based diets did not decrease the response to PN (P > .5). In Exp. 3, cows were assigned to five treatments to test the effects of aging needles after they were ground, feeding bentonite, and feeding a complete mineral supplement. Pine needles decreased IP (P < .01), and the effects of PN were greater when PN were aged or bentonite or minerals were added (all P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)