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PubMed2003

Host range of poliovirus is restricted to simians because of a rapid sequence change of the poliovirus receptor gene during evolution.

The host range of most poliovirus (PV) strains is restricted to simians. This host range specificity is believed to be determined by the interaction between PV and its receptor molecule. To elucidate the molecular basis of this species-specific infection of PV, we cloned orthologs of the PV receptor (PVR) gene ( pvr) as well as those of PV receptor-related genes 1 and 2 ( prr1 and prr2) from various mammalian species. These three genes are widely present in mammalian genomes including those of non-susceptible species. Comparison of the deduced amino acid sequences of PVR orthologs revealed that the NH(2)-terminal immunoglobulin-like domain (domain 1), which is the virus binding site in the human PVR, is highly variable among species, whereas that of PRR1 is highly conserved. Domain 1 of the PVR orthologs for the ring-tailed lemur and rabbit, which are not susceptible to PV, show only 51 and 61% amino acid sequence identity to that of human PVR, respectively. Chimeric PVR proteins that have the domain 1 of the ring-tailed lemur and rabbit PVRs failed to serve as receptors for PV. These results suggest that rapid changes in the domain 1 sequence during mammalian evolution determined the host range restriction of PV.

Amino Acid Sequence↗
PubMed2006

Transient and stable expression of the HCV envelope glycoproteins in cell lines and primary hepatocytes transduced with a recombinant baculovirus.

A recombinant baculovirus, RecBV-E, encoding the hepatitis C virus (HCV) envelope proteins, E1 and E2, controlled by the cytomegalovirus promoter was constructed. RecBVs can infect mammalian cells, but fail to express proteins or replicate because the viral DNA promoters are not recognised. The RecBV-E transduced 86% of Huh7 cells and 22% of primary marmoset hepatocytes compared with 35% and 0.4%, respectively, after DNA transfection. Several stable cell lines were generated that constitutively expressed E1/E2 in every cell. No evidence of E1/E2-related apoptosis was noted, and the doubling times of cells were similar to that of the parental cells. A proportion of the E1/E2 was expressed on the surface of the stable cells as determined by flow cytometry and was detected by a conformation-dependent monoclonal antibody. It is likely that the continued expression of E1/E2 in the stable cells resulted from integration of the RecBV DNA. Infection of Huh7 cells, in the absence of G418 selection, failed to result in expression of the foreign gene (in this case, eGFP) beyond 14-18 days. RecBVs that express HCV genes from a CMV promoter represent an effective means by which to transduce primary hepatocytes for expression and replication studies.

Animals↗
PubMed1998

The hemagglutinin of recent measles virus isolates induces cell fusion in a marmoset cell line, but not in other CD46-positive human and monkey cell lines, when expressed together with the F protein.

Measles virus (MV) is efficiently isolated from patients with measles by using B95a cells, a marmoset B cell line. Recent wild-type MV strains isolated using B95a cells did not produce cytopathic effects in any of CD46+ primate cell lines examined (except B95a cells), nor did they induce downregulation of CD46. Transfection of the hemagglutinin (H) and fusion (F) genes of the Edmonston strain of MV produced syncytia in HeLa, Cos and B95a cells. By contrast, the expression of the H gene from the two wild-type strains, together with the F gene of the Edmonston strain, resulted in syncytium production in B95a cells, but not in HeLa and Cos cells. Cocultivation of Cos cells expressing the wild-type H protein and the Edmonston strain F protein with B95a cells, but not with HeLa, Jurkat or BJAB cells, generated large syncytia. The results suggest that these recent MV isolates may use a molecule other than CD46 as the cellular receptor or require another coreceptor to infect cells.

Animals↗
PubMed2001

Adaptation of wild-type measles virus to CD46 receptor usage.

Vaccine strains of measles virus (MV) use CD46 as receptor and downregulate CD46 from the surface of infected cells. MVs isolated and passaged on B-lymphoid cells (wild-type MVs) seem to use another receptor and do not downregulate CD46. In the present study, we found that isolation of MV on human or marmoset B-lymphoid cells did not alter the MV haemagglutinin (H) protein relative to that in the patient. The wild-type isolates were adapted to the human epithelial HEp-2 cell line or the monkey fibroblast Vero cell line. All HEp-2 cell adapted viruses and 1 out of 4 Vero cell adapted viruses acquired the capacity to use CD46 as receptor, as measured by their ability to infect murine cells expressing human CD46. Adaptation to CD46 receptor usage was coupled to substitution of amino acid 481 of the MV H protein from asparagine to tyrosine but not to CD46 downregulation. The present study demonstrates that CD46 receptor usage can be induced by adaptation of wild-type MV to cells that do not express a wild-type receptor and suggests that a similar mechanism acted on the progenitor viruses of the present MV vaccine strains during their isolation and attenuation.

Animals↗
PubMed2005

Vascular morphogenesis in the primate ovary.

Ovarian function is dependent on intense cyclical vascular morphogenesis and regression. The molecular and cellular pathways involved in the generation of new capillary networks in the ovary are now being elucidated. Focussing on the marmoset, the course of angiogenesis at different stages of follicular maturation and in the corpus luteum throughout the cycle and in early pregnancy have been quantified and major progress has been made in the evaluation of the role of vascular endothelial growth factor (VEGF). To study the physiological role of VEGF in follicular and luteal angiogenesis in detail, VEGF was inhibited during defined stages of the cycle in vivo. VEGF antagonist administered throughout the follicular phase of the cycle resulted in a marked decrease in endothelial cell proliferation in developing antral follicles, accompanied by a decline in granulosa cell proliferation, restriction of follicular growth and inhibition of ovulation. An outstanding feature in the ovary is the intense angiogenesis that occurs during the early luteal phase. VEGF inhibitors markedly suppressed this angiogenesis, resulting in a marked restriction in the development of the microvascular tree and suppression of plasma progesterone. These studies showed that VEGF is essential for normal follicular and luteal angiogenesis and function, and demonstrated how luteal angiogenesis in particular could serve as a sensitive bioassay for putative angiogenic antagonists. Antagonists of VEGF are potent tools for investigating the role of angiogenic factors within the ovary and may have applications to the treatment of reproductive disorders characterised by alterations in normal vascular structure or function.

Angiogenesis Inducing Agents↗
PubMed1988

The influence of dietary lipid supplementation on cardiac beta-adrenergic receptor adenylate cyclase activity in the marmoset monkey.

Dietary lipid supplements high in either saturated fat derived from sheep kidney fat or unsaturated fat derived from sunflower seed oil, and a low mixed fat reference diet were fed to marmoset monkeys for 20 months and the effects on cardiac membrane lipid composition, and myocardial catecholamine-stimulated adenylate cyclase and beta-adrenergic receptor binding activity were investigated. For cardiac membranes enriched for beta-adrenergic binding activity, the dietary lipid treatment resulted in small changes in the proportion of saturated to unsaturated fatty acids and substantial changes in the (n - 6) to (n - 3) series of unsaturated fatty acids in the membrane phospholipids. The sheep kidney fat diet increased the cholesterol-to-phospholipid ratio in cardiac membranes in comparison to the other diets. This diet also significantly elevated basal and isoproterenol-, epinephrine- and norepinephrine-stimulated adenylate cyclase activity. The value of the dissociation constant (Kd) and the receptor number (Bmax) for the binding of [125I]ICYP to the beta-adrenergic receptor was significantly reduced in marmosets fed the sheep kidney fat diet. These results suggest that dietary lipids can influence the activity of the beta-adrenergic/adenylate cyclase system of the heart. Modulation of this transmembrane signalling system may be induced by changes in the properties of the associated membrane lipids, particularly by alteration in the membrane cholesterol-to-phospholipid ratio. This effect may be limited to those animal species in which the nature of the dietary fatty acid intake may be influencing cardiac membrane cholesterol homeostasis, which is in agreement with previous results in rats following dietary cholesterol supplementation (McMurchie et al. (1987) Biochim. Biophys. Acta 898, 137-153). ICYP, (-)-iodocyanopindolol.

Adenylyl Cyclases↗
PubMed1990

Incorporation and effects of dietary eicosapentaenoate (20:5(n-3)) on plasma and erythrocyte lipids of the marmoset following dietary supplementation with differing levels of linoleic acid.

The effect of dietary eicosapentaenoic acid (EPA, 20:5(n-3), as the ethyl ester) on plasma lipid levels and the incorporation of EPA into erythrocyte and plasma lipids were investigated in the marmoset monkey. Marmosets were fed high mixed-fat diets (14.5% total fat) supplemented with or without 0.8% EPA for 30 weeks. Markedly elevated plasma cholesterol (16.4 mmol/l) was induced by an atherogenic-type diet but with EPA supplementation, plasma cholesterol increased to only 6.6 mmol/l. Plasma triacylglycerol levels were not elevated with an atherogenic type diet. Substantial EPA incorporation was evident for plasma phospholipid, triacylglycerol and cholesterol ester fractions. The proportion of docosapentaenoic acid (22:5(n-3)) but not docosahexaenoic acid (22:6(n-3)) was also elevated in these plasma lipid fractions. Greatest incorporation of EPA occurred when it was administered with an atherogenic type diet having a P:M:S (polyunsaturated:monounsaturated:saturated) fatty acid ratio of about 0.2:0.6:1.0 in comparison to the control diet of 1.0:1.0:1.0. Incorporation of EPA and 22:5(n-3)) into erythrocyte phospholipids was also apparent and this was at the expense of linoleic acid (18:2(n-6)). These results in the marmoset highlight both the cholesterol-lowering properties of EPA and the extent of its incorporation into plasma lipids and erythrocyte membrane phospholipids with far greater incorporation occurring when the level of dietary linoleic acid was reduced.

Animals↗
PubMed1989

Effects of dietary eicosapentaenoate (20:5 n-3) on cardiac beta-adrenergic receptor activity in the marmoset monkey.

Eicosapentaenoic acid (EPA; 20:5 n-3; ethyl ester) in combination with atherogenic or non-atherogenic high fat diets was fed to young adult male marmoset monkeys for a period of 30 weeks. EPA markedly reduced the raised plasma cholesterol level evident when feeding an atherogenic diet but did not influence the cardiac membrane cholesterol-to-phospholipid ratio. EPA and its elongation product 22:5 n-3 was incorporated into cardiac membrane phospholipids at the expense of linoleic and arachidonic acids. Dietary EPA increased cardiac beta-AR affinity and reversed the decreased beta-AR affinity evident when feeding an atherogenic diet.

Animals↗
PubMed1988

Hydrolysis of the four stereoisomers of soman catalyzed by liver homogenate and plasma from rat, guinea pig and marmoset, and by human plasma.

Stereoselective hydrolysis at pH 7.5 and 37 degrees of C(+/-)P(+/-)-soman by liver homogenate and plasma from rat, guinea pig and marmoset, and by human plasma is studied by using the four single stereoisomers. The fast hydrolysis of the C(+/-)P(+)-isomers is monitored titrimetrically, whereas the decay of the much slower reacting C(+/-)P(-)-isomers is followed by gas chromatographic determination of the residual concentration. Values of Km and Vmax are evaluated for the enzymatic hydrolysis of the two relatively nontoxic C(+/-)P(+)-isomers. The plasma enzymes have a high affinity for these isomers (Km: 0.01-0.04 mM); the Km values of the liver enzymes vary between 0.04 and 0.7 mM. Except for rat liver homogenate, only first-order rate constants can be obtained for catalyzed hydrolysis (kc) of the highly toxic C(+/-)P(-)-isomers: most measurements with C(+/-)P(-)-isomer concentrations greater than 0.3 mM are complicated by epimerization to C(+/-)P(+)-isomers, which may conceal enzyme saturation with the C(+/-)P(-)-isomers. The first-order rate constants of catalyzed hydrolysis (Vmax/Km or kc) by all liver homogenates and plasmata decrease in the order: C(+)P(+)- greater than C(-)P(+)- much greater than C(-)P(-)- greater than C(+)P(-)-soman. The highest P(+)-/P(-)-stereoselectivity is found for rat plasma. Rat liver homogenate is more potent than the other liver homogenates in catalyzing the hydrolysis of both the C(+/-)P(+)- and the C(+/-)P(-)-isomers. Rat plasma shows the highest activity for degradation of the C(+/-)P(+)-isomers, but is approximately as active as marmoset and human plasma for degradation of the C(+/-)P(-)-isomers.

Animals↗
PubMed1989

Transient depletion of nucleus accumbens dopamine content may contribute to initial akinesia induced by MPTP in common marmosets.

Acute treatment of common marmosets with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) caused an initial profound akinesia and other motor deficits. However, over the following months akinesia gradually disappeared although the animals remained clumsy and poorly coordinated. At 10 days following MPTP treatment there was a profound decrease in the dopamine, HVA and DOPAC content of the caudate nucleus, putamen and nucleus accumbens. By 3-4 months following MPTP treatment the animals had largely recovered from their akinesia, but the caudate nucleus and putamen dopamine, HVA and DOPAC content remained low. In contrast, the dopamine content of the nucleus accumbens had returned towards normal and the metabolite levels were higher than at 10 days. No overall alterations in 5HT or 5HIAA levels were observed at either time point. The transient and reversible nature of dopamine loss in the nucleus accumbens may contribute to the initial profound akinesia exhibited by common marmosets treated with MPTP. The restoration of dopamine levels in the nucleus accumbens may be partially responsible for the subsequent recovery of motor function that occurs in MPTP-treated marmosets.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine↗
PubMed1992

Identification of the proximate peroxisome proliferator(s) derived from di (2-ethylhexyl) adipate and species differences in response.

Identification of the proximate peroxisome proliferator(s) derived from di (2-ethylhexyl) adipate (DEHA) has been achieved using primary hepatocyte cultures derived from different species and cyanide-insensitive fatty acyl CoA oxidase (PCO) as a marker enzyme for peroxisome proliferation. In rat and mouse hepatocytes, the parent compound (DEHA) had no effect on peroxisomal beta-oxidation, but primary metabolites of DEHA, mono (2-ethylhexyl) adipate (MEHA) and 2-ethylhexanol (EH), were approximately equipotent in PCO induction (5-fold at 0.5 mM final concentration). The secondary metabolite of DEHA, 2-ethylhexanoic acid (EHA), was in both species the most potent peroxisome proliferator (25- and 9-fold induction in mice and rats, respectively, at 1 mM final concentration). At 2 mM final concentration a tertiary metabolite of DEHA, 2-ethyl-5-hydroxyhexan-1-oic acid, was less effective in mouse and rat hepatocytes at inducing PCO (15- and 5-fold, respectively). 2-Ethyl-5-oxohexan-1-oic acid and 2-ethylhexan-1,6-dioic acid had little effect (2-3-fold in both rat and mouse hepatocytes). Thus, EHA was identified as the proximate peroxisome proliferator of DEHA and mouse hepatocytes were approximately twice as sensitive as rat hepatocytes to peroxisome proliferation due to MEHA, EH and EHA. We investigated further species differences in response to peroxisome proliferators by using guinea pig and marmoset primary hepatocyte culture. None of the chemicals studied stimulated peroxisomal beta-oxidation in these species up to a final concentration of 2 mM. Higher concentrations lead to cytotoxicity. This lack of sensitivity of guinea pig and marmoset hepatocytes is in agreement with previous studies with di (2-ethylhexyl) phthalate metabolites, suggesting the absence of a threat of hepatocarcinogenic damage to these species and confirming that primary hepatocytes cultures are useful models for investigating the phenomenon of peroxisome proliferation.

Adipates↗
PubMed1993

Hydrolysis and binding of a toxic stereoisomer of soman in plasma and tissue homogenates from rat, guinea pig and marmoset, and in human plasma.

The fallen concentration of one of the two isomers of soman (1,2,2-trimethylpropyl methylphosphonofluoridate), i.e., C(+)P(-)-soman, was investigated in plasma and in homogenates of brain, lung, liver, kidney, diaphragm, skeletal muscle and mucosa of small intestines from rat, guinea pig and marmoset, and in human plasma (pH 7.5, 37 degrees). The decrease of the isomer concentration was followed by gas chromatographic determination of the residual concentration and proceeded in two phases due to a very rapid saturation of covalent binding sites for the isomer followed by catalysed hydrolysis. Estimates for the concentrations of covalent binding sites were obtained, which were relatively high in liver and kidney. Time periods for the hydrolysis of the isomer from a concentration of 40 ng/mL to 20 ng/mL were evaluated from the second reaction phase. It is concluded that the spontaneous and enzyme-catalyzed hydrolytic activities found for degradation of C(+)P(-)-soman in organs participating in central elimination are sufficiently high to account for the terminal half-life times of the isomer found in our toxicokinetic studies for the blood concentration after intoxication with 2-6 LD50 C(+/-)P(+/-)-soman. The hydrolytic activities are lower in the target organs for toxic action of soman, e.g., diaphragm and brain, especially for guinea pigs and marmosets.

Animals↗
PubMed1993

Identification of the epitope of an anti-peptide antibody which binds to CYP1A2 in many species including man.

An anti-peptide antibody was raised against the sequence Thr-Gly-Ala-Leu-Phe-Lys-His-Ser-Glu-Asn-Tyr-Lys which occurs at positions 283-294 in the rat cytochrome P450 enzyme CYP1A2. Compared with its binding to the peptide used for immunization, the antibody bound with only slightly reduced affinity to the truncated peptides Thr-Gly-Ala-Leu-Phe-Lys-His-Ser and Leu-Phe-Lys-His-Ser. However, binding to the peptide Ser-Glu-Asn-Tyr-Lys-Asp-Asn, which overlaps with the C-terminal region of the immunizing peptide, was very low. Thus, a major epitope for the anti-peptide antibody is Leu-Phe-Lys-His-Ser, which corresponds to a region of CYP1A2 that is conserved in many species. The antibody was tested by immunoblotting for its ability to bind to hepatic microsomal fractions from a number of species. Where possible animals were treated with compounds which induce CYP1A2 and the results compared with those with untreated animals. It was found that the antibody bound to rat, mouse, rabbit, hamster, guinea pig, pig, marmoset monkey and human CYP1A2. No evidence was found for binding to dog CYP1A2. The region corresponding to the major epitope at residues 286-290 of rat CYP1A2 was identical in mouse, hamster, rabbit and human CYP1A2. The sequence of marmoset and guinea pig CYP1A2 are not known but are predicted to be very similar to the sequence in the rat. The lack of binding of the antibody to dog CYP1A2 may be explained by two differences in this region compared with rat CYP1A2. Maximum inhibition of CYP1A2 activity by this antibody, as measured by high-affinity phenacetin O-deethylase activity, was 20%. This is in contrast to a previously described anti-peptide antibody directed to an adjacent region which caused 65% inhibition of this activity. Thus, the edge of an inhibitory region on the surface of cytochrome P450 has been identified. The ability of the antibody to bind to CYP1A2 from a number of animals should make this antibody of use for studying the levels of CYP1A2 apoprotein in many species.

Amino Acid Sequence↗
PubMed1996

RP 64477: a potent inhibitor of acyl-coenzyme A:cholesterol O-acyltransferase with low systemic bioavailability.

RP 64477 (N-butyl-3-(p-decyloxybenzamido)-4-(methylthio)benzamide) has been shown to be a potent inhibitor of the cholesterol esterifying enzyme Acyl-coenzyme A:cholesterol O-acyltransferase (EC 2.3.1.26; ACAT) in intestinal, hepatic, adrenal, and arterial tissue preparations obtained from a range of animal species. Drug concentrations producing 50% inhibition of enzyme activity (IC50 values) ranged from 14-283 nM. Inhibition by RP 64477 in a rabbit intestinal enzyme preparation was shown to be non-competitive with respect to the substrate oleoyl-CoA. In whole cell assays using human intestinal (CaCo-2), hepatic HepG2) and monocytic (THP-1) cell lines, RP 64477 inhibited ACAT activity with IC50s of 113, 503, and 180 nM, respectively. RP 64477 (0.03% w/w by diet) reduced significantly cholesterol absorption in cholesterol/cholic acid-fed rats from 94+/- 8% to 65 +/- 4%. In cholesterol-fed rabbits, cholesterol absorption was reduced from 72 +/- 5% to 50 +/-5% and 44 +/- 5% at dose levels of 10 and 30 mg kg-1 b.i.d., respectively. Plasma cholesterol levels were reduced dose-dependently in both cholesterol/cholic-acid-fed rats and cholesterol-fed rabbits. Neither cholesterol absorption nor plasma cholesterol levels were reduced significantly in animals maintained on standard laboratory diets. Pharmacokinetic studies indicated that RP 64477 were very poorly absorbed following oral administration to rats. Plasma levels of drug were < 2 ng mL-1 following a dose of 2000 mg kg-1 p.o.. When radiolabelled RP 64477 was administered orally, limited absorption was indicated by the overwhelming elimination of radioactivity in the faces (96.4% of administered material) coupled with low renal clearance (0.6% of dose) and biliary excretion (0.05% of dose). In conclusion, this work shows that RP 64477 is a potent inhibitor of ACAT obtained from a range of animal species and man. Inhibition of cholesterol absorption and hypocholesterolaemic activity has been demonstrated in rats and rabbits maintained on diets supplemented with cholesterol. Pharmacokinetic studies indicate low systemic exposure to RP 64477 as a result of limited absorption of this drug.

Acyl Coenzyme A↗