No description available.

No description available.

Thesis (Ph. D.)--University of Washington, 1996. / Vita. Includes bibliographical references (leaves 145-176).

Thesis (Ph. D.)--University of Wisconsin--Madison, 1982. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 267-288).

There were two aims in this thesis. Firstly, to investigate cholinesterase and its isoenzymes in the fetal mouse brain, and secondly to study drug-induced fetal damage with the following objectives in mind: (i) to examine new markers for the evaluation and prediction of the teratogenic potential of drugs, and (ii) to try and throw more light on pathogenic mechanisms of drug injury with particular reference to the developing fetal central nervous system. Acetylcholinesterase activity in brain homogenates was determined colorimetrically and the isoenzymes were separated by polyacrylamide gel electrophoresis. A cyanmethaemoglobin method was used to measure the contribution of acetylcholinesterase activity in blood to total brain esterase activity. Cholinesterase activity was estimated colorimetrically, and with the aid of enzyme inhibitors and polyacrylamide gel electrophoresis. The effects of three central nervous system teratogens, vitamin A, cyclophosphamide and sodium valproate when administered during embryonic development, on gross fetal parameters in C3H mice including embryolethality, gross morphological abnormalities, fetal weight, brain weight, brain acetylcholinesterase and its isoenzymes, and in some instances brain total protein content and choline acetyltransferase activity, were assessed. Preliminary studies were also performed with a view to future areas of research on (i) the effects of vitamin A when administered during the pre-implantation period on viability/esterase enzyme activity, cell number, mitotic index and chromosome structure in the 81h blastocyst; (ii) the influence of vitamin A on C3H fetal mouse brain proteins using high resolution two-dimensional electrophoresis; and (iii) the effects of cyclophosphamide and vitamin A on cephalic DNA damage utilising a DNA unwinding assay to detect DNA strand breaks. Substantial acetylcholinesterase activity of ± 3nmol/min/mg was present in 17-day to 19-day fetal mouse brains and 5 isoenzymes were present on electrophoresis. The contribution of acetylcholinesterase activity in blood was low at approximately 3%. Similarly, fetal mouse brain cholinesterase activity was found to be very low and the effect of teratogens on this enzyme was not assessed. A rise in the incidence of malformations and embryolethality with increase in dose, and after administration earlier in gestation occurred with all three teratogens. A growth-inhibitory effect was another feature although this was most pronounced after cyclophosphamide administration. Acetylcholinesterase activity was affected by the teratogen used and its time of administration as well as other factors such as growth inhibition, haemorrhage and repair processes. Vitamin A administration on day 10 of gestation was associated with a greater acetylcholinesterase activity compared with controls, which was not accompanied by a change in brain total protein content or choline acetyltransferase activity. Cyclophosphamide and sodium valproate administration during the embryonic period were associated with a lower acetylcholinesterase activity in near-term fetuses. However, in fetuses examined two days after cyclophosphamide administration there was a greater acetylcholinesterase activity associated with an increase in haemoglobin and a decrease in choline acetyltransferase. A higher acetylcholinesterase activity was also observed in exencephalic brains. Vitamin A administration was associated with a higher activity of isoenzyme 5 whereas cyclophosphamide and sodium valproate administration resulted in a lower peak height for band 4. When vitamin A was administered during the pre-implantation period 60h after copulation no effect on viability/esterase enzyme activity, cell number, mitotic index or chromosome structure was observed in 81h embryos. However, a striking incidence of abnormalities was noted in fetuses examined near term. This study suggested that teratogenic doses of vitamin A modified the brain protein pattern of the fetal mouse with a possible broad spectrum deletion of protein spots and the appearance of a limited number of new spots. There was no evidence of DNA strand breaks induced by vitamin A, which contrasted with obvious cephalic DNA damage after cyclophosphamide administration. The potential of these techniques in the prediction of the embryotoxicity of drugs, and progress in the understanding of underlying mechanisms are discussed.

No description available.

The hypothesis of this study was that dietary n-3 fatty acids protect against phenytoin (P) teratogenicity by inhibiting embryonic prostaglandin H synthase bioactivation of P and/or by delaying embryonic development. Female caesarian-derived (CD-1) mice were fed a safflower (SAFF)- or a cod liver/linseed oil (CLO/LO)-based diet for three weeks prior to impregnation and throughout pregnancy. The CLO/LO diet, compared to the SAFF diet, reduced malformations and fetal growth retardation due to P. Open eye defect was the only anomaly induced by P in CLO/LO fetuses while P produced cleft palates only in SAFF fetuses. Since the period of maximal susceptibility to open eye defect occurs before palatal closure, this result suggests that the CLO/LO diet delayed development relative to the SAFF diet. In Exp 2, dietary n-6/n-3 fatty acid ratios were reflected in maternal hepatic phospholipids. Lipid peroxidation (LPO) was induced in maternal hepatic tissues by the SAFF diet while LPO was induced by P only in CLO/LO embryos.

Thalidomide was discovered to be teratogenic over 50 years ago, but is far from being a historical problem. A new generation of thalidomide survivors have been reported in Brazil, where the drug is used to treat leprosy complications and multiple myeloma. The mechanisms underlying thalidomide teratogenesis are not fully understood. Cereblon (CRBN) protein has been identified as a target of thalidomide. Cereblon is part of an E3 ubiquitin ligase complex with Damaged DNA Binding protein 1 and Cullin-4A. I have analysed the expression patterns of CRBN and its binding partners in wildtype and thalidomide-treated chicken and zebrafish embryos. My results show that CRBN complex genes are weakly expressed in multiple tissues, including those not affected by thalidomide, and do not change following thalidomide exposure. I have also investigated the teratogenic potential of Primodos, a drug claimed to be “the forgotten thalidomide”. This drug was used as a pregnancy test between 1950's and 1970's. Primodos is alleged to be teratogenic but still is not recognised as one. Several epidemiological studies have been conducted, with conflicting results. I have been analysing the teratogenic properties of Primodos in chicken and zebrafish embryos and found that Primodos causes a range of malformations in zebrafish embryos. I have also carried out molecular analyses that show Primodos causes gene expression changes, changes in blood vessel patterning and neurite outgrowth in vivo and in vitro and increase in cell death. Finally, I have investigated the role of blood vessels in limb development and patterning. Using an antiangiogenic analogue of thalidomide, I found that inducing blood vessel loss in different regions of the forelimb bud of developing chicken results in different phenotypes. My results suggest that blood vessels might be involved in limb patterning and progress the understanding of limb defects observed in thalidomide survivors.

No description available.

This investigation evaluated the potential protective role of Zn, through modulation of MT, against the teratogenic effects of isotretinoin (ITR), a dermatological drug which causes oxidative damage, in CD-1 mouse embryos. Significant induction of MT by Zn supplementation was observed in mouse embryos both in vivo and in vitro. On gestational day (GD) 6.5, pregnant mice received a subcutaneous Zn injection of 0 (saline), 20 and 40 mg/kg, resulting in embryonic MT concentrations of 12.5, 54.5 and 93.4 $ mu$g/g protein, respectively, after 48h. Embryos were extracted at GD 8.5 and incubated with 0 (saline) and 15 $ mu$M Zn for 48h. There was a six-fold increase in MT expression in the Zn treatment group, resulting in MT concentration of 688 $ mu$g/g protein. Pre-induction of MT by Zn exposure was found to offer protection against subsequent exposure to ITR in vivo and in vitro. Zn injections of 40 and 20 mg/kg to pregnant mice on GD 8.5 and 9.5, respectively, alleviated fetal damage caused by three intragastric intubations of 100 mg ITR/kg on GD 10.5. Zn pre-treatment significantly increased fetal and placental masses, totally eliminated the incidence of cleft palate and lessened the frequency of post-partum mortality by 74%. Pre-treatment of GD 8.5 embryos with a 24h culture period with 15 $ mu$M Zn improved growth and totally restored normal embryonic development altered by a 24h culture with 17 $ mu$M ITR. Zn decreased the frequencies of unfused mid brain and fore brain by 100%, and the incidence of abnormal flexion by 74%. A reduction in MT concentrations was observed in groups exposed to ITR, indicating that MT may have been oxidized by ITR-derived toxic FR. (Abstract shortened by UMI.)