Doctoral Dissertations

Date of Award

8-1987

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

Hugo Eiler

Committee Members

Craig Cullen, Jim Godkin, Fred Hopkins, J. B. McLaren

Abstract

Retained fetal membranes (RFM) in cattle occur when there is a disturbance in the loosening mechanism of the placentome and all or parts of the placental attachments fail to separate and pass from the uterus within 12 hours. The cause of RFM is unknown. The working hypothesis of this research was that the etiology of primary RFM is a condition of collagen metabolism of the placentome. The objectives of this study were to (1) histologically quantitate placentome collagen using morphometric techniques, (2) visually evaluate the fetal-maternal junction and collagenous stroma of the placentome using electron microscopy; (3) chemically quantitate placentome collagen by measuring hydroxyproline (collagen is uniquely 10% hydroxyproline), alpha amino nitrogen and total protein content; and (4) electrophoretically identify collagen types present in placentomes. Collagen of four gestational groups (90, 150, 210 and 270 days of gestation), naturally calving (2 hours postpartum) and experimentally induced retained placentas (2 and 12 hours postpartum) was examined. Placentomes were obtained after slaughter for the gestational studies and transvaginally following natural calving and experimentally induced retention of membranes. There were eight cows per treatment group. Light microscopy morphometry showed that fetal collagen increased (P<.05) between 90, 150, 210 and 270 days of gestation (mean volume fraction [Vv]=0.03, 0.06, 0.13 and 0.19 respectively). Fetal collagen was lower (P<.05) 12 hours postpartum in experimentally induced retained membranes (Vv=0.12) than in naturally calving cotyledons (Vv=0.18) or at 270 days of gestation (Vv=0.20). Maternal collagen decreased (P<.05) between days 150 and 210 (Vv=0.52 and 0.48). Maternal collagen was lower (P<.05) 2 hours after parturition in experimentally retained membranes (Vv=0.42) than at day 270 of gestation (Vv=0.48). Electron microscopy studies of selected samples showed that collagen transformed from a wavy, tortuous appearance in the earlier gestational groups to a more linear appearance in the later groups. Collagen of the retained tissues appeared similar to that of the earlier gestational groups indicating the existence of an altered state of development of collagen in experimentally retained placental tissues. The microvilli at the fetal-maternal junction appeared to increase in relative number and size over the various gestational stages. Separation of the fetal-maternal junction was noted at day 270. Microvilli of the experimentally retained tissues were irregular in form and arrangement. Chemical studies showed collagen (hydroxyproline) of whole placentome tissue increased (P<.05) between 90, 150, 210 and 270 days of gestation (mean hydroxyproline=3.4, 5.1, 6.8 and 10.0 mg/g). Collagen increased (P<.05) between days 90, 150 and 210 in fetal tissues (3.1, 4.5 and 7.0 mg/g) and between days 210 and 270 in maternal tissues (4.4 and 6.0 mg/g). Interplacentome collagen did not differ (P<.05) over gestation but was about 2-3 times higher than in placentome tissue. While collagen decreased in experimentally retained whole placentomes between 2 and 12 hours postpartum (9.5 and 6.9 mg/g), no differences (P>.05) were found in fetal or maternal collagen content between days 270, naturally calving cotyledons or experimentally induced retained membranes. No difference (P>.05) in alpha amino nitrogen content of whole tissues was found between days 90 and 270 of gestation. Fetal nitrogen increased (P<.05) between days 90 and 150 (mean nitrogen=24.8 and 41.6 mg/g) while maternal nitrogen was higher at day 210 (59.7 mg/g) than at days 90, 150 or 270 of gestation (45.1, 45.0 and 51.8 mg/g). No difference (P<.05) in nitrogen content was seen in whole or fetal tissues between 270 days of gestation and experimentally retained tissues or naturally calving cotyledons. A decrease (P<.05) in nitrogen was observed between 2 and 12 hour postpartum experimentally retained maternal tissues (47.6 and 39.2 mg/g). Mean total protein in whole tissues was 568.2, 588.0, 620.7 and 668.9 mg/g at 90, 150, 210 and 270 days of gestation, respectively. Fetal protein increased (P<.05) between days 90, 150 and 210 (432.0, 479.9 and 585.4 mg/g) and maternal protein increased (P<.05) between days 150 and 210 (564.9 and 609.8 mg/g). No differences (P>.05) were found in protein between 270 days of gestation and 2 or 12 hours post-experimentally induced samples for whole, fetal or maternal tissues, however, less protein (P<.05) was found in fetal cotyledons following natural calving. Electrophoretic studies showed a higher (P<.05) ratio of type I/III collagens was found at day 150 in whole placentome (15.0) than at days 90, 210 or 270 of gestation (6.1, 5.8 and 8.2, respectively). In fetal tissues, the type I/III ratio increased (P<.05) between days 90 and 150 (3.3 and 6.4) while no difference (P>.05) was seen in the ratio of type I/III collagens in maternal tissues. No differences (P>.05) in the ratio of type I/III were found in the whole, fetal or maternal tissues between 270 days of gestation and 2 or 12 hour experimentally induced retained samples, however, an increase (P<.05) in the ratio of type I/III was found in naturally calving cotyledons. It was concluded that electron microscopy studies showed no evidence of the cause of placental membrane retention by examination of the fetal-maternal junction. Both morphometric and chemical analysis showed placentome collagen increased throughout gestation, however, abnormal amounts of total collagen were not found in experimentally retained tissues indicating that abnormal quantities of collagen may not be responsible for retention of fetal membranes. However, a variation in the ratio of type I/III collagens was found in fetal cotyledons of experimentally retained placentomes as compared to naturally calving cotyledons. Type I collagen was significantly lower in experimentally retained fetal cotyledons than in cotyledons following natural calving. Type III collagen of experimentally retained cotyledons was equal to earlier stages of gestation. These findings show abnormal collagen development both in stromal orientation and the ratio of type I/III collagens in experimentally retained fetal cotyledons as compared to naturally calving cotyledons.

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