Biomedical subjects

C R Wolf

Publications and source records attributed to C R Wolf.

At least 91 records · Page 5Linked to original sources

PubMed1997

Oxidative DNA damage in CD34+ myelodysplastic cells is associated with intracellular redox changes and elevated plasma tumour necrosis factor-alpha concentration.

Ineffective haemopoiesis in the myelodysplastic syndromes (MDS) is mediated, at least in part, by apoptosis, though the mechanisms of apoptotic induction are unclear. Tumour necrosis factor-alpha (TNF-alpha) promotes apoptosis via intracellular oxygen free radical production, oxidation of DNA and proteins, and is increasingly implicated in the pathogenesis of MDS. Using single-cell gel electrophoresis, we have identified oxidized pyrimidine nucleotides in the progenitor-enriched bone marrow CD34+ compartment from MDS patients (P=0.039), which are absent in both CD34- MDS cells (P=0.53) and also CD34+ cells from normal subjects (P=0.55). MDS CD34+ blood cells also showed oxidized pyrimidine nucleotides compared with CD34- cells (P=0.029). Within normal subjects no differences were seen between CD34+ and CD34- bone marrow cell compartments. CD34+ bone marrow cell oxidized pyrimidines were strongly associated with elevated plasma TNF-alpha and low bone marrow mononuclear cell glutathione concentrations (5/6 patients) and the inverse relationship was also found (3/4 patients). This data implies a role for intracellular oxygen free radical production, perhaps mediated by TNF-alpha, in the pathogenesis of ineffective haemopoiesis in MDS and provides a rationale for the bone marrow stimulatory effects of antioxidants such as Amifostine in MDS.

Aged↗

PubMed1997

Metabolism of MPTP by cytochrome P4502D6 and the demonstration of 2D6 mRNA in human foetal and adult brain by in situ hybridization.

1. 1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a thermal breakdown product of synthetic 'street' heroin, is known to cause Parkinson's Disease-like symptoms in man. 2. The mechanism of action of this neurotoxin is thought to involve activation by the monoamine oxidase B system and subsequent toxicity by inhibition of neuronal mitochondrial respiration. The manifestation of toxicity will be a balance between the rate of activation of this compound versus its rate of inactivation through metabolism by enzymes such as the cytochrome P450-dependent monooxygenases. 3. In this report we demonstrate that MPTP N-demethylation, a detoxification pathway, is catalysed by cytochrome P450 CYP2D6 and up to 40% of the hepatic metabolism is mediated by this enzyme. 4. Perhaps more importantly we also demonstrate by in situ hybridization that CYP2D6 is localized in the pigmented neurons of the substantia nigra indicating that 2D6-mediated detoxification will occur in target cells. 5. These data present evidence that CYP2D6 will be a factor in susceptibility to MPTP neuronal toxicity and provide a biochemical rationale for the genetic observations linking a polymorphism at the CYP2D6 locus with susceptibility to Parkinson's.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗

PubMed1997

Metabolic competence and susceptibility of intestinal epithelium to genotoxic injury during regeneration.

The carcinogenic potency of many mutagens is increased in conditions of tissue regeneration. This involves fundamental changes of cellular division and differentiation, in intestinal epithelium. However, effects on epithelial capacity for carcinogen metabolism and susceptibility to genotoxic injury are unknown. Using a novel rat model, this study assessed expression of cytochrome P450 mono-oxygenases (Cyps), glutathione S-transferases (GSTs) and uridine diphosphoglucuronosyl transferase (UGT) in intestinal epithelium during sequential stages of regeneration. Enzyme induction and DNA adduct formation were also assessed after benzo[a]pyrene (BaP) exposure. Control assays were carried out in normal intestinal epithelium. Fewer phase I and II xenobiotic metabolizing enzymes were expressed in regenerating intestinal epithelium than in normal control intestinal epithelium (GSTA3, UGT in regeneration vs Cyp2B, GSTA1/2, GSTA4, GSTP1, UGT in control). Benzo[a]pyrene induced GSTA3 and UGT in regeneration vs Cyp1A, Cyp2B, GSTA1/2, GSTA3, GSTA4, GSTP1 and UGT in control normal intestinal epithelium. Benzo[a]pyrene induced low levels of GSTA3 in early regenerating intestinal epithelium but induction increased by >2-fold at late stage regeneration. Higher levels of benzo[a]pyrene 7,8-diol-9,10-epoxide (BPDE) DNA adducts were formed at early stages of regeneration, than at later stages. Intestinal epithelium displayed reduced metabolic competence and differential susceptibility to genotoxic injury from BaP, during regeneration.

Animals↗

PubMed1997

Identification of genetic polymorphisms at the glutathione S-transferase Pi locus and association with susceptibility to bladder, testicular and prostate cancer.

Two variant glutathione S-transferase cDNAs have been described at the GSTP1 locus, which differ by a single base pair (A-G) substitution at nucleotide 313 of the GSTP1 cDNA. This results in an amino acid substitution which alters the function of the enzyme. In this study, a novel PCR assay has been developed which demonstrates that these two variant cDNAs represent distinct GSTP1 alleles (GSTP1a and GSTP1b). In a study of individuals with different forms of cancer, the GSTP1b allele is found to be strongly associated with bladder cancer and testicular cancer. In controls 6.5% of individuals were homozygous for the GSTP1b allele. In bladder cancer cases, this rose to 19.7% [n = 71, odds ratio 3.6 (1.4-9.2), P = 0.006] and in testicular cancer to 18.7% [n = 155, odds ratio 3.3 (1.5-7.7), P = 0.002]. In addition, in prostate cancer a highly significant decrease in the frequency of the GSTP1a homozygotes was observed [control 51.0% versus 27.8% cancer cases, n = 36, odds ratio 0.4 (0.02-3.3), P = 0.008]. Increases in the frequency of GSTP1b homozygotes was also observed in lung cancer and chronic obstructive pulmonary disease. However, these were not statistically significant. No change in breast or colon cancer allele frequencies was observed.

Aged↗

PubMed1997

Genotypes of glutathione transferase M1 and P1 and their significance for lung DNA adduct levels and cancer risk.

The A-G polymorphism at codon 104 in the glutathione S-transferase P1 (GSTP1) gene was examined in 138 male lung cancer patients and 297 healthy controls. The patients had significantly higher frequency of the GG genotype (15.9%) and a lower frequency of AA (38.4%) than the controls (9.1% and 51.5%, respectively). The level of hydrophobic DNA-adducts were determined in lung tissue from 70 current smokers. Patients with the GG genotype had a significantly higher adduct level than patients with AA (15.5 +/- 10.2 vs 7.9 +/- 5.1 per 10(8) nucleotides, P = 0.006). We also analyzed the deletion polymorphism in the GSTM1 gene in 135 male patients and 342 controls. The patients were stratified according to histology, smoking dose, age, adduct level and mutational types found in the tumors (Ki-ras and p53 genes). The results consistently indicated that the GSTM1 null genotype was associated with a slightly increased lung cancer risk. When the combined GST M1 and P1 genotypes were examined, patients with the combination null and AG or GG had significantly higher adduct levels than all other genotype combinations (P = 0.011). The distribution of combined genotypes was also significantly different in cases and controls, mainly due to increased frequency of the combination GSTM1 null and GSTP1 AG or GG among patients.

Adult↗

PubMed1997

A simplified assay for the arylamine N-acetyltransferase 2 polymorphism validated by phenotyping with isoniazid.

Human arylamine N-acetyltransferase (NAT) activity is determined by two distinct genes, NAT1 and NAT2, and the classical acetylation polymorphism in NAT2 has been associated with a variety of disorders, including lupus erythematosus and arylamine induced cancers. Over 50% of the white population exhibit a slow acetylator phenotype. The genetic basis of the defect has been identified and several DNA based assays are available for genotyping studies. We present here a simplified, rapid PCR based assay for the identification of the major slow acetylator genotypes and validate it using isoniazid as probe drug. This assay was 100% predictive of phenotype. The three genotypes (homozygous mutated, heterozygous, and homozygous rapid) corresponded to a trimodal distribution of Ac-INH/INH metabolic ratios (slow, intermediate, and rapid) without overlapping.

Arylamine N-Acetyltransferase↗

PubMed1996

Coexpression of a human P450 (CYP3A4) and P450 reductase generates a highly functional monooxygenase system in Escherichia coli.

The catalytic activities of recombinant cytochrome P450s expressed in E. coli have been impeded by the absence of endogenous P450 reductase. To solve this problem, we coexpressed P450 reductase with CYP3A4. Membranes from this strain contained 215 pmol P450/mg protein and a reductase activity of 1315 nmol cytochrome c reduced/min per mg. We detected 6beta-hydroxylation of testosterone and oxidation of nifedipine in vivo with turnover numbers of 15.2 and 17.3 min(-1), respectively. These values compare favourably with those obtained using an optimally reconstituted system. Our data demonstrate that a catalytically efficient human P450 system can be generated in E. coli.

Base Sequence↗

PubMed1996

Characterization of the human cytochrome P4502D6 promoter. A potential role for antagonistic interactions between members of the nuclear receptor family.

The functional mapping of the human cytochrome P4502D6 (CYP2D6) promoter in HepG2 cells revealed the presence of both positive and negative regulatory elements. One of these regulatory elements overlapped a sequence that is highly conserved in most members of the CYP2 family. This element, which consists of a degenerate AGGTCA direct repeat spaced by 1 base pair (DR1) and is known to be a target for members of the steroid receptor superfamily, was found to bind in vitro translated hepatocyte nuclear factor 4 (HNF4) in gel retardation analysis. Using HepG2 nuclear extracts, three protein-DNA complexes were formed on the DR1 element, one of which was confirmed to be dependent on the binding of HNF4. The other DR1 complexes were shown to be due to the interaction of the orphan receptor chicken ovalbumin upstream promoter transcription factor I (COUP-TFI). Experiments in COS-7 cells showed that HNF4 could activate the CYP2D6 promoter 30-fold. Surprisingly, mutation of the DR1 element produced a relatively minor 23% decrease in activity in HepG2 cells. Additionally, COUP-TFI was shown to inhibit HNF4 stimulation of the CYP2D6 promoter in COS-7 cells, suggesting that COUP-TFI could attenuate the effect of HNF4 in HepG2 cells. However, when HNF4 levels were increased in HepG2 cells by co-transfection, it resulted in the enhancement of CYP2D6 promoter activity, indicating that HNF4 could overcome the repressive effect of COUP-TFI. Therefore, the contribution of the DR1 element in controlling the transcription of the CYP2D6 gene depends on the balance between positively and negatively acting transcription factors.

Animals↗

PubMed1996

Observation of structural variation and spin state conversion of cytochrome P450 CYP2B4 on binding of sterically different substrates.

Addition of sterically different substrates to CYP2B4 suggests perturbation of the environment of the haem ring and differing degrees of 6cls-5chs conversion. Strain on the ring, by implication induced by changes in the surrounding protein environment, is demonstrated by the emergence of the v29 band upon laurate binding. Furthermore, intensity differences and frequency shifts for non-Raman active (Eu) modes appear to be substrate dependent and are sensitive to haem/substrate interactions. The likelihood is that substrate induced distortion of the haem will have an effect on catalytic activities and attention needs to be directed towards substrate pocket interactions. SERRS (Surface enhanced resonance Raman scattering) provides a unique and sensitive spectroscopic probe of these interactions.

Animals↗

PubMed1996

Differential effects of neuroleptic agents on hepatic cytochrome P-450 isozymes in the male rat.

We report the effects of various dopamine receptor-blocking drugs on gene and protein expression, as well as the activity of several hepatic cytochrome P-450 (CYP) enzymes in the male Sprague-Dawley rat. At equipotent doses (with respect to receptor blockade and behavioural tests), the dopamine D2-receptor selective sulpiride and remoxipride gave a conspicuous down-regulation of CYP2C11 and its associated androstenedione 16 alpha-hydroxylation activity as well as of the CYP2C11-specific mRNA. The average immunoidentified CYP2C11 levels correlated with the CYP2C11-specific mRNA levels in all treatment groups (r = 0.994), indicating a transcriptional mechanism. The CYP3A protein was also selectively down-regulated. In contrast, androstenedione 5 alpha-reduction was significantly increased. Clozapine, a non-selective neuroleptic, gave the same effects on the steroid metabolism as sulpiride and remoxipride. In contrast, diverging effects were observed for clozapine, compared to sulpiride and remoxipride, on the immunoidentified CYP1A2, CYP2B1, and CYP3A. These proteins were elevated by clozapine, and down-regulated by sulpiride and remoxipride. Our results are of interest for the interpretation of preclinical dose ranging toxicity tests of neuroleptic agents in rats. They may also be relevant in relation to certain interactions and adverse reactions observed in the clinical use of these drugs. The down-regulation of certain CYP enzymes is most likely mediated by an interaction with the growth hormone secretion.

Androstenedione↗

PubMed1996

Functional characterization of the transcription silencer element located within the human Pi class glutathione S-transferase promoter.

We have previously demonstrated enhanced transcriptional activity of the human Pi class glutathione S-transferase (GSTP1) promoter in a multidrug-resistant derivative (VCREMS) of the human mammary carcinoma cell line, MCF7 (Moffat, G. J., McLaren, A. W., and Wolf, C. R. (1994) J. Biol. Chem. 269, 16397-16402). Furthermore, we have identified an essential sequence (C1; -70 to -59) within the GSTP1 promoter that bound a Jun-Fos heterodimer in VCREMS but not in MCF7 cells. These present studies have examined the negative regulatory element (-105 to -86), which acted to suppress GSTP1 transcription in MCF7 cells. Mutational analysis of this silencer element further defined the repressor binding site to be located between nucleotides -97 and -90. In vitro DNA binding assays suggested that the repressor exerted its action by causing displacement of the essential non-AP-1-like MCF7 C1 complex. However, the addition of MCF7 nuclear extract did not disrupt binding of the VCREMS Jun-Fos C1 complex to the GSTP1 promoter. Furthermore, upstream insertion of the GSTP1 silencer element failed to inhibit activity of a heterologous promoter in MCF7 cells. These results highlighted the cell and promoter specificity of the GSTP1 transcriptional repressor and implicated a functional requirement for contact between the repressor and C1 complex. In this regard, the introduction of half-helical turns between the silencer and the C1 element abrogated repressor activity, thus leading to the hypothesis that a direct interaction between the repressor and C1 complex was required to suppress GSTP1 transcription. Moreover, these findings suggest that cell-specific differences in the composition of the C1 nuclear complex may dictate repressor activity.

Base Sequence↗

PubMed1996

Active-site topologies of human CYP2D6 and its aspartate-301 --> glutamate, asparagine, and glycine mutants.

Cytochrome P450 2D6 (CYP2D6) catalyzes the oxidation of substrates with a positively charged nitrogen atom 5-7 angstroms from the site of the oxidation. The active-site topology of CYP2D6 is examined here with phenyl-, 2-naphthyl-, and p-biphenyldiazene, which react with P450 enzymes to form sigma-bonded aryl-iron (Fe-Ar) complexes. Ferricyanide-mediated migration of the aryl group from the iron to the porphyrin nitrogens produces the N-arylprotoporphyrin IX regioisomers (NB:NA:NC:ND, in which the aryl group is bound to the nitrogen of pyrrole rings B, A, C, and D, respectively) in the following ratios (zero means <5%): phenyl, 10:90:00:00; 2-naphthyl, 09:91:00:00; and p-biphenyl, 16:84:00:00. These results suggest that the CYP2D6 active site is open above pyrrole ring A and to a small extent above pyrrole ring B but is closed above pyrrole rings C and D. This geometry differs from those determined by the same method for P450s for which crystal structures are available. Replacement of Asp-301 by a Glu, which preserves the carboxylate side chain, causes no detectable change in the N-aryl porphyrin regioisomer patterns and only minor changes in the catalytic activity. Replacement of Asp-301 by an Asn or Gly, which eliminates the negatively charged side chain, suppresses migration of the aryl groups to pyrrole ring B without impairing migration to pyrrole ring A and virtually abolishes catalytic activity. These results provide a refined model of the active site of CYP2D6. They confirm, furthermore, that the loss of activity observed when Asp-301 is replaced by a neutral residue is due to loss of the charge-pairing interaction with the substrate positive charge and/or subtle structural effects in the vicinity of pyrrole ring B, but not to major structural reorganization of the active site.

Asparagine↗

PubMed1996

Influence of amino acid residue 374 of cytochrome P-450 2D6 (CYP2D6) on the regio- and enantio-selective metabolism of metoprolol.

Cytochrome P-450 2D6 (CYP2D6) is an important human drug-metabolizing enzyme responsible for the oxidation of more than 30 widely used therapeutic agents. The enzymes encoded by the published genomic [Kimura, Umeno, Skoda, Meyer and Gonzalez (1989) Am. J. Hum. Genet. 45, 889-904] and cDNA [Gonzalez, Skoda, Kimura, Umeno, Zanger, Nebert, Gelboin, Hardwick and Meyer (1988) Nature 331, 442-446] sequences of CYP2D6, and presumed to represent wild-type sequences, differ at residue 374 and encode valine (CYP2D6-Val) and methionine (CYP2D6-Met) respectively. The influence of this amino acid difference on cytochrome P-450 expression, ligand binding, catalysis and stereoselective oxidation of metoprolol was investigated by the heterologous expression of the corresponding cDNAs in the yeast Saccharomyces cerevisiae. The level of expression of apo- and holo-protein was similar with each form of CYP2D6 cDNA, and the binding affinities of a series of ligands to CYP2D6-Val and CYP2D6-Met were identical. The enantioselective O-demethylation and alpha-hydroxylation of metoprolol were also similar with each form of CYP2D6, O-demethylation being R-(+)- enantioselective (CYP2D6-Val: R/S, 1.6; CYP2D6-Met: R/S, 1.4), whereas alpha-hydroxylation showed a preference for S-(-)-metoprolol (CYP2D6-Val: R/S, 0.7; CYP2D6-Met: R/S, 0.8). However, although the favoured regiomer overall was O-demethylmetoprolol (ODM), the regioselectivity for O-demethylation of each metoprolol enantiomer was significantly greater for CYP2D6-Val [R-(+)-: ODM/alpha-hydroxymetoprolol (alpha OH), 5.9; S-(-)-: ODM/alpha OH, 2.5) than that observed for CYP2D6-Met [R-(+)-: ODM/alpha OH, 2.2; S-(-)-: ODM/alpha OH, 1.4]. The stereoselective properties of CYP2D6-Val were consistent with those observed for CYP2D6 in human liver microsomes. The difference in the stereoselective properties of CYP2D6-Val and CYP2D6-Met were rationalized with respect to a homology model of the active site of CYP2D6 based on an alignment with the crystal structure of the bacterial cytochrome P-450BM-3' CYP102.

Amino Acid Sequence↗

PubMed1996

Induction of cytochrome P-450 BM-3 (CYP 102) by non-steroidal anti-inflammatory drugs in Bacillus megaterium.

Bacillus megaterium contains a cytochrome P-450 fatty acid mono-oxygenase which is inducible with barbiturate drugs. We have demonstrated that this enzyme system is inducible with peroxisome proliferators. In mammals, peroxisome proliferators also induce mono-oxygenases in the CYP4A gene family. In this paper we demonstrate that the non-steroidal anti-inflammatory drugs ibuprofen, ketoprofen and indomethacin are potent inducers of fatty acid mono-oxygenase activity as well as of P-450BM-3 protein in B. megaterium. The levels of induction of P-450 protein were 11.8-, 3.9- and 3.0-fold respectively. In addition, we demonstrate that these inducing agents interact with a transcriptional repressor, Bm3R1, which leads to its dissociation from its operator sequence. This provides a rational mechanism for the induction process. This is the first report which demonstrates that non-steroidal anti-inflammatory drugs can interact directly with a transcription factor to initiate gene expression, and further substantiates the structure-activity relationships that identify inducers of cytochrome P-450BM-3 and compounds that have the potential to act as peroxisome proliferators and induce CYP4A expression in mammals.

Animals↗

PubMed1996

A model for human cytochrome P450 2D6 based on homology modeling and NMR studies of substrate binding.

The cytochrome P450 responsible for the debrisoquine/sparteine polymorphism (P450 2D6) has been produced in large quantities by expression of a modified cDNA in baculovirus. A polyhistidine extension was incorporated at the C-terminus of the expressed protein, which, after purification of the protein on a nickel-agarose column, could be removed proteolytically by treatment with thrombin. Purified yields of P450 2D6 were 2.4 mg from 700 mL of cell culture. The protein had a greater than 90% heme content and was fully active, having no residual absorbance at 420 nm in the reduced CO complex. The quantities produced allowed direct study of the interaction of the substrate codeine with the enzyme by paramagnetic relaxation effects on the NMR spectrum of the substrate. Distances between the heme iron atom and substrate protons were calculated from these experiments, and the orientation of the substrate in the binding pocket was determined. This showed that codeine was bound with the methoxy group of the molecule closest to the heme iron (iron-methyl proton distance of 3.1 +/- 0.1 A), consistent with the observed O-demethylation to morphine. A model of the complex Of P450 2D6 with codeine was built from a multiple sequence and structure alignment of the known crystal structures for P450s, incorporating the experimental constraints derived from the NMR studies. This showed that the overall fold Of P450 2D6 is more similar to that of P450 BM3 than to either P450 cam or P450 terp. Codeine binds to P450 2D6 so that the methoxy group is directly above the A ring of the heme, while the basic nitrogen interacts with the carboxylate of aspartate 301.

Amino Acid Sequence↗

PubMed1996

Functional high level expression of cytochrome P450 CYP2D6 using baculoviral expression systems.

Cytochrome P-450 CYP2D6 plays a central role in the metabolism of many widely used therapeutic drugs including beta-adrenergic antagonists, antiarrhythmics, and tricyclic antidepressants. Recombinant baculoviruses have been constructed containing the full-length human CYP2D6 cDNA and used to express CYP2D6 in Spodoptera frugiperda (Sf9) cells. High levels of recombinant protein have been produced using either polyhedrin or basic protein promoters (0.05-0.20 nmol/mg cell protein; 0.05-0.15 nmol/liter). The enzyme is catalytically active toward CYP2D6 substrates such as bufuralol and metoprolol. In order to optimize catalytic activity human reductase was coexpressed with CYP2D6 in Sf9 cells; reductase activity was in the region of 1000-1500 units per mg cell protein, while spectrally active CY2D6 was in the range 10-20 pmol/mg cell protein. The K(m) and K(cat) values for bufuralol metabolism were estimated as 4.7 microM and 12.23 min-1, respectively. The use of the conventional very late promoters such as the polyhedrin promoter generate a large proportion of inactive CYP2D6. The problem was to a degree circumvented using the "late" basic promoter which is active earlier in the baculovirus infection cycle. The yield of functional CYP2D6 was at least as high as with very late promoters, but the proportion of inactive protein was reduced. Bufuralol hydroxylase activity could be measured directly by HPLC analysis of cell culture media supplemented with bufuralol, and we have developed a plate assay system which provides a simple method for the analysis of drug metabolism reactions using Sf9 cells. Expression using baculovirus provides a valuable source of functional CYP2D6 for work aimed at elucidating the structure and function of the enzyme.

Adrenergic beta-Antagonists↗

PubMed1996

Transfer of PCBs via lactation simultaneously induces the expression of P450 isoenzymes and the protooncogenes c-Ha-ras and c-raf in neonates.

At the first day of lactation, maternal rats were injected with a single i.p. dose of 100 or 250 mg/kg body weight of a mixture of polychlorinated biphenyls (Aroclor 1254). This treatment caused significant increases in both material and neonatal hepatic cytochrome P-450, cytochrome b5, and cytochrome-c-(P-450) reductase. Transfer of PCBs via lactation resulted in significant increases in hepatic enzyme activities catalysed by neonatal CYP1A1, CYP1A2, CYP2B1, CYP3A1, and CYP2E1 using a variety of substrates. In contrast, the metabolism of dimethylnitrosamine and aminopyrine was only marginally (up to 2-fold) increased in maternal animals four days post treatment. Further measurements showed significant increases in maternal and neonatal epoxide hydrolase, glutathione-S-transferase, and UDP-glucuronyl transferase activities, thus suggesting a coordinated response for an induction of CYP1A1, CYP1A2, CYP2A1, CYP2B1, CYP2E1, CYP3A1, and CYP4A1 in both maternal and neonatal CYP2C6, and at the higher dose the expression of neonatal CYP2E1 was significantly reduced. Northern blot analysis provided further evidence for significant increases in maternal and neonatal hepatic CYP1A1, CYP1A2, CYP2B1, and CYP2E1 mRNA, but reduced amounts of CYP2C7 and CYP4A1 mRNA. Additional Northern blot hybridization experiments may suggest an increased expression of the protooncogenes c-Ha-ras and c-raf in the mother and the neonate upon treatment of maternal rats with Aroclor 1254. Lactation itself may result in an increased expression of the latter protooncogenes, but the mRNA of the protooncogenes c-erb A and c-erb B was not detected in any of the tissues examined.

Animals↗

PubMed1996

The ontogeny of key endoplasmic reticulum proteins in human embryonic and fetal red blood cells.

Recently, using immunohistochemical methods, we surprisingly found that endoplasmic reticulum glucose-6-phosphatase is present in human embryonic and fetal red blood cells (RBCs) but not in adult RBCs. The fact that an endoplasmic reticulum enzyme, whose major site of expression in adults is the liver, is present in human embryonic and fetal RBCs, particularly nucleated cells, indicated that it would be sensible to determine whether these cells also contain other endoplasmic reticulum enzyme systems normally found in adult liver. Therefore, we have studied the expression of other endoplasmic reticulum proteins and found that human embryonic and fetal RBC precursors contain other protein components of the glucose-6-phosphatase system, ie, the phosphate and glucose transport proteins as well as other enzymes (eg, uridine diphosphate-glucuronosyltransferases, cytochrome P450 isozymes, nicotinamide adenine dinucleotide phosphate cytochrome P450 oxidoreductase, and prostaglandin H synthase). In addition, we also found the predominantly cytosolic markers 15-hydroxyprostaglandin dehydrogenase, prostaglandins PGE2 and 13,14-dihydro-15-keto-PGE2. The expression of key enzymes that control glucose production, detoxification of endobiotics and xenobiotics, and the regulation of prostaglandin levels in embryonic and early fetal RBCs means that these cells may have an important role in protecting the developing conceptus before it establishes an efficient circulation and before all tissues fully express their normal complement of these enzymes.

Adult↗