Biomedical subjects

G D Bennett

Publications and source records attributed to G D Bennett.

41 records · Page 3Linked to original sources

PubMedDate not supplied

Cocaine selectively alters neurotransmitter receptor mRNAs in mouse embryos.

Alterations in gene expression due to in utero cocaine exposure may adversely affect nervous system development. The present study examined whether or not cocaine administration to pregnant mice alters embryonic mRNA levels for several developmentally-regulated genes. Antisense RNA amplification was performed using RNA from LM/Bc embryos at gestational days 9.5 and 10.5 after three days of cocaine treatment. This technique highlights simultaneous changes that occur in the expression of many genes after a teratogenic insult. Significant changes occurred in the expression pattern on only four genes from a total of 42 candidate cDNAs. These included increases in the relative levels of the alpha and beta 1 subunits of the GABAA receptor without concurrent changes in the non-NMDA glutamate receptor subunits. The results support the hypothesis that in utero cocaine exposure leads to specific changes in gene expression that may ultimately contribute to developmental abnormalities.

Animals↗

PubMedDate not supplied

Arsenic-induced neural tube defects in mice: alterations in cell cycle gene expression.

The potential of arsenic to cause neural tube defects (NTD) in the human population remains a topic of controversy. While clearly toxic, the lack of well-defined human epidemiologic studies on this subject has made it difficult to fully understand the effects arsenic may have on the developing human neural tube. In the absence of good clinical data, we have tried to develop a murine model where hypotheses about the reproductive toxicity of arsenate can be tested. For these studies a murine strain (LM/Bc) that has proven to be susceptible to arsenic-induced NTD was use. Because cellular proliferation is vital for normal neural tube closure (NTC) to occur, in the present study we investigated whether an acute arsenate treatment could alter the expression of several cell cycle genes during murine neurulation. Pregnant LM/Bc dams were injected intraperitoneally on gestation day (GD) 7:12 (day:hour) and 8:12 with 40 mg/kg of arsenate, a treatment that causes exencephaly in 90 to 100% of the exposed fetuses. Neural tubes were then isolated from both control and arsenic treated embryos at GD 9:00, 9:12, 10:00, and 10:12, which encompasses all the stages of neurulation for this murine strain. Using the molecular techniques of in situ transcription and antisense RNA amplification (RT/aRNA) the expression pattern for bc1-2, p53, wee-1, and wnt-1 was analyzed at each of these time points. In the neural tubes isolated from control embryos, the expression of all four genes was significantly altered as neurulation progressed, demonstrating their developmental regulation. Following arsenate treatment, however, there was a significant upregulation in the expression of bc1-2 and p53 at gestational day 9:0, compared to their control values. The heightened expression of both of these genes suggests that arsenic inhibits cell proliferation, rather than inducing apoptosis, which delayed NTC and ultimately led to the neural tube defects observed in exposed embryos.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Effect of stiripentol dose on phenytoin-induced teratogenesis in a mouse model.

PURPOSE: Previous studies have suggested that polytherapy by design may aid in the management of human pregnancies complicated by epilepsy. However, mechanistic parallels must be drawn between the models of teratogenesis and human pregnancies, and doses of the second agent given to minimize side-effects must be justified. This study sought to determine the lowest dosage of stiripentol (STP) protective against phenytoin-induced teratogenesis in a mouse model, and to determine mechanistically if inhibition of oxidative metabolism by STP in vitro decreased production of reactive phenytoin (PHT) metabolites. METHODS: Pregnant SWV mice were assigned to control or treatment groups of STP alone, PHT alone, or PHT with ascending doses of STP coadministration. Treatments continued from Day 6 to Day 18 of gestation when fetuses were examined for developmental anomalies. [14C]PHT was incubated in mouse liver microsomes with and without NADPH and in the presence or absence of STP or piperonyl butoxide. Covalent binding of [14C] was measured. RESULTS: There were no dose-related differences in the frequency of fetal malformations per litter among groups treated with STP alone. However, STP (all doses) reduced the frequency of PHT-induced malformations. Covalent binding of [14C]PHT was NADPH-dependent and was inhibited by either piperonyl butoxide or STP. CONCLUSIONS: The beneficial effects of STP occurred at concentrations below the therapeutic range for its anticonvulsant effects. These results support the concept of polytherapy by design to reduce the risk of teratogenesis associated with PHT.

Abnormalities, Drug-Induced↗

PubMedDate not supplied

Valproic acid-induced alterations in growth and neurotrophic factor gene expression in murine embryos [corrected].

Although the teratogenicity of valproic acid (VPA) has been well established, the mechanism(s) by which this anticonvulsant drug induces malformations remains controversial. Using the combined molecular techniques of in situ-transcription (IST) and antisense RNA (aRNA) amplification we analyzed VPA-induced alterations in the gene expression for 10 genes within the neural tubes of embryos from two murine strains that have been shown to differ in their susceptibility to VPA-induce neural tube defects (NTD). Pregnant dams from both SWV (susceptible) and LM/Bc (resistant) strains were either treated with saline (control) or VPA (600 mg/kg) on gestational day (GD) 8:12 (day:hour). Neural tubes were isolated from control or VPA exposed embryos at three gestational time points, which represented the beginning (GD 8:18), middle (GD 9:00), and end (GD 9:12) of neural tube closure (NTC) in both of these murine strains. Using univariant statistics we demonstrated that in LM/Bc embryos with NTDs, the expression of bdnf, ngf, and trk, ngf-R were significantly elevated at all three time points, and the cytokine, cntf was significantly decreased at GD 9:00. In contrast, the major gene alterations observed in SWV embryos were a significant increase in tfgalpha and tgfbeta1-3 at GD 9:00. In an effort to better define the more intricate interactions between VPA exposure and the expression of these genes, we analyzed our data using Principal Component Analysis. The results from this analysis demonstrated that embryos from these two stains behaved differently, not only in response to a VPA exposure, but also under control conditions, which may explain the multifactorial nature of NTDs in these mice.

Analysis of Variance↗

PubMedDate not supplied

Altered gene expression in murine branchial arches following in utero exposure to retinoic acid.

Retinoic acid (RA) in the form of isotretinoin (Accutane) and tretinoin (Retin-A) is a clinically important compound in the treatment of dermatologic disorders. However, it is also a potent teratogen associated with a number of serious congenital malformations. Generally, these malformations involve the craniofacial structures derived from the first and second branchial arches. To determine how altered gene expression may contribute to the observed RA-induced defects, pregnant LM/Bc mice were administered (5 mg/kg) all-trans RA on gestational day (GD) 8:12. First and second branchial arches were removed from control and teratogen-treated embryos on GD 10:00 10:12, or 12:00, processed by in situ transcription/aRNA techniques, and analyzed for alterations in gene expression. In these studies, a panel of 40 candidate genes that are known to be important in mammalian craniofacial development were examined. This analysis revealed significant differences in the expression level of the nicotinic acetylcholine receptor subunit alpha (NAChR), transforming growth factor beta 2 (TGF beta 2), type 1 cellular retinoid binding protein (CRBP-1), retinoic acid receptor gamma (RAR gamma), and cAMP response element binding protein (CREB). The alterations observed in the expression of these genes following RA exposure may prohibit normal morphogenetic processes within the second branchial arch and lead to the observed malformations.

Animals↗