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Biomedical subjects

X J Chen

Publications and source records attributed to X J Chen.

At least 73 records · Page 4Linked to original sources
PubMed1996

Vitamin A deficiency increases inflammatory responses.

The authors studied the influence of vitamin A deficiency on immediate and delayed type hypersensitivity as well as granulocyte-mediated inflammatory reactions in vitamin A depleted and control rats. The number of circulating leucocytes was 43% higher in the vitamin A deficient than in the control animals. The leucocytosis was a result of a general increase of white blood cells and was not due to an increase in one particular type. The ratio between CD4+ and CD8+ T cells was unchanged. The vitamin A deficient rats had a four times higher T-cell proliferative response and a two times higher interferon-gamma production in vitro than the control animals. In accordance, the DTH reaction was consistently higher in the vitamin A deficient rats. The granulocyte dependent inflammation, induced by olive oil injection, was also strongly enhanced in the vitamin A deficient rats compared with the controls. In addition, the spontaneous release of nitric oxide from the peritoneal phagocytes was five times higher in the vitamin A deficient animals. The number of peritoneal mast cells was about one and a half times higher in the vitamin A deficient than in the control animals. The density of IgE-receptors on the mast cells, the IgE receptor occupancy and the histamine release from the mast cells did not differ between the groups, however. The vitamin A deficient immunized rats displayed a consistently stronger immediate skin reaction after intracutaneous antigen injection than the immunized control rats, despite lower IgE antibody levels. The skin reaction after intracutaneous injection of histamine was also significantly greater in the deficient animals. Despite the stronger reaction to antigen and histamine, the passive cutaneous anaphylaxis reaction was lower in the vitamin A deficient rats. In conclusion the study shows that vitamin A deficiency aggravates the clinical manifestations of inflammatory reactions. Thus, vitamin A deficiency might lead to a higher risk of acquiring irreversible tissue damage and disabling destruction.

Animals↗
PubMed1996

The mitochondrial genome integrity gene, MGI1, of Kluyveromyces lactis encodes the beta-subunit of F1-ATPase.

In a previous report, we found that mutations at the mitochondrial genome integrity locus, MGI1, can convert Kluyveromyces lactis into a petite-positive yeast. In this report, we describe the isolation of the MGI1 gene and show that it encodes the beta-subunit of the mitochondrial F1-ATPase. The site of mutation in four independently isolated mgi1 alleles is at Arg435, which has changed to Gly in three cases and Ile in the fourth isolate. Disruption of MGI1 does not lead to the production of mitochondrial genome deletion mutants, indicating that an assembled F1 complex is needed for the "gain-of-function" phenotype found in mgi1 point mutants. The location of Arg435 in the beta-subunit, as deduced from the three-dimensional structure of the bovine F1-ATPase, together with mutational sites in the previously identified mgi2 and mgi5 alleles, suggests that interaction of the beta- and alpha- (MGI2) subunits with the gamma-subunit (MGI5) is likely to be affected by the mutations.

Amino Acid Sequence↗
PubMed1996

Site-directed mutations in the third domain of Bacillus thuringiensis delta-endotoxin CryIAa affect its ability to increase the permeability of Bombyx mori midgut brush border membrane vesicles.

A series of mutant Bacillus thuringiensis CryIAa delta-endotoxin proteins was prepared by replacing the first, second, and last arginine residues of the conserved third-domain sequence, R-521 YRVRIR-527, with other amino acids. The stable mutant proteins were bioassayed against Bombyx mori larvae and found to all be approximately half as active as wild-type CryIAa. The toxins were also tested by means of a light-scattering assay for their ability to increase permeability of larval B. mori midgut brush border membrane vesicles. Three of the mutant toxins were as active as the wild-type toxin in the vesicle permeability assay.

Animals↗
PubMed1996

Immune responses to a Nippostrongylus brasiliensis infection in athymic and euthymic rats: surface expression of IgE receptors, IgE occupancy and secretory ability of mast cells.

The significance of T cells in an allergy-related immune response was investigated. Athymic, nude (Lewis rnu/rnu) rats lacking T lymphocytes and euthymic (Lewis+/+) rats were infected with the nematode Nippostrongylus brasiliensis. The density and occupancy of IgE receptors on peritoneal mast cells were quantified using a cytofluorometric method. The secretory ability of the mast cells as a function of anti-IgE challenge was evaluated in terms of histamine releasability in vitro. It was found that the IgE receptors were markedly up-regulated and the IgE occupancy increased on the mast cells of both athymic and euthymic rats during the parasite infection. However, at its peak, IgE occupancy was significantly higher in euthymic rats than in athymic ones. To our knowledge, this is the first proof of the possibility of a T-cell-independent IgE response in vivo. The IgE-mediated histamine releasability of mast cells was significantly enhanced 1 week after the infection in euthymic rats but not in athymic ones. These results thus indicate that the IgE immune response can occur in the absence of, but is augmented by, T cells. They also suggest that the concept of the IgE response should be widened to comprise not only increased IgE production but also an up-regulation of Ig receptors and an increase in IgE occupancy on mast cells, as well as an increase in the secretory ability of these cells. The latter is T cell dependent, although it is not directly related to the density of IgE-receptor complexes on the mast cells but is more likely due to a stimulation of the post-receptor signal transduction mechanism.

Animals↗
PubMed1996

[Mechanism of intracellular calcium homeostasis in heat-exposed cardiomyocytes of rats].

The activity of Ca(2+)-ATPase and calcium content were measured in sarcoplasmic reticulum (SR) and mitochrondria of myocardium from 40 adult female Wistar rats after exposure to 37 degrees C, 39 degrees C, 41 degrees C and 43 degrees C for 40 min respectively in vitro. The 45Ca uptake, intracellular free Ca2+ concentration ([Ca2+]i) and the relatively active calmodulin content were also observed in cultured cardiomyocytes from 120 neonatal Wistar rats under the same condition of heat exposure. The results showed that (1) the activity of Ca(2+)-ATPase of SR and mitochrondria of myocardium decreased after heat exposure, (2) the calcium content of SR and mitochrondria also showed a tendency of decrease with increase of exposure temperature, (3) the 45Ca uptake and mean [Ca2+]i increased, whereas the calmodulin content decreased. It is suggested that disturbances of intracellular calcium homeostasis may be responsible for cardiac functional disorder after heat exposure.

Animals↗
PubMed1996

Analgesic activity and selectivity for opioid receptors of enantiomers of ohmefentanyl.

AIM: To study analgesic activity and selectivity for opioid receptor subtypes of 8 enantomers of ohmefentanyl (Ohm). METHODS: Analgesic activity was evaluated using the hot plate test in mice. Selectivity for opioid receptors was determined in binding assay and bioassay. RESULTS: Among the 8 enantiomers of Ohm, the most potent isomer was F-9204, (+)-cis-(3R, 4S, 2'S)-Ohm, with an analgesic ED50 (i.p.) value of 1.1 (0.8-1.3) micrograms.kg-1. These enantiomers selectively acted on mu opioid receptors. Ki values (mu) of enantiomers F-9204 and F-9202, (-)-cis-(3R, 4S, 2'R)-Ohm were 4.0 +/- 2.0 and 5 +/- 4 pmol.L-1, respectively. Their Ki(delta)/Ki(mu) ratios were 22,500 and 22,800, respectively. On guinea pig ileum and mouse vas deferens F-9202, F-9204, F-9205, F-9206, F-9207, and F-9208 exhibited very potent inhibitons, which were antagonized by naloxone. In rabbit vas deferens these enantiomers had no effect. CONCLUSION: Eight enantiomers of Ohm selectively acted on mu opioid receptors. F-9204 showed the strongest analgesic activity and the highest selectivity for mu opioid receptors.

Analgesics↗
PubMed1995

Stereoisomers of N-[1-hydroxy-(2-phenylethyl)-3-methyl-4-piperidyl]- N-phenylpropanamide: synthesis, stereochemistry, analgesic activity, and opioid receptor binding characteristics.

N-[1-(2-Hydroxy-2-phenylethyl)-3-methyl-4-piperidyl]-N-phenylpropanamide (ohmefentanyl,1) is an extremely potent analgesic agent with high affinity and selectivity for opioid mu receptors. There are three chiral carbons in 1, so eight optically active isomers are possible. Respective reaction of optically active 3-methyl-N-phenyl-4 -piperidinamines (5a-d) with (R)- or (S)-styrene oxide produced eight optically active intermediates which were subsequently converted to eight optically active isomers of 1 (1a-h). The absolute configurations of 1a-h were determined by X-ray analysis of (3R,4S,2'R)-(-)-cis-1a and (3R,4R,2'S)-(-)-trans-1g. The analgesic activity (mice, ip, hot plate) revealed their extreme stereodifferences; the ED50 values of (3R,4S,2'R)-(-)-cis-1a and (3R,4S,2'S)-(+)-cis-1b, which are the most potent isomers among eight isomers, were 0.004 65 (2990 times that of morphine) and 0.001 06 mg/kg (13 100 times that of morphine), respectively, while the corresponding antipodes 1d,c were the least potent compounds among the eight isomers. In agreement with pharmacological results, both 1a,b also had the highest receptor affinity and selectivity for the opioid mu receptor. The ratio of K(i)(DPDPE)&K(i)(DAMGO) was 22 800 for 1a and 22 500 for 1b. All isomers except 1c,d strongly inhibited the electrically evoked smooth muscle contraction of GPI and MVD but not that of RVD, and the inhibitory effects could be reversed by naloxone, which indicated that these compounds were potent mu agonists in GPI and MVD. There was a good linear correlation between the analgesic potencies (ED50) and the receptor affinities (K(i)(DAMGO)) or inhibitory effects (IC50) to GPI and MVD. These results suggested that the analgesic effects of ohmefentanyl are mediated by interaction between the agents and opioid mu receptors in the central nervous system and the 3R,4S configuration at the piperidine 3- and 4-carbon atoms and the S configuration at the phenylethyl 2-carbon atom are beneficial for analgesic potency and inhibitory effects in GPI and MVD and the same for an S or R configuration at the phenylethyl 2-carbon atom besides the 3R,4S configuration for receptor mu affinity and selectivity.

Analgesics↗
PubMed1995

Specific mutations in alpha- and gamma-subunits of F1-ATPase affect mitochondrial genome integrity in the petite-negative yeast Kluyveromyces lactis.

We have shown previously that mutations in nuclear genes, termed MGI, for mitochondrial genome integrity, can convert the petite-negative yeast Kluyveromyces lactis into a petite-positive form with the ability to produce mitochondrial genome deletion mutants (Chen and Clark-Walker, Genetics, 133, 517-525, 1993). Here we describe that two genes, MGI2 and MGI5, encode the alpha- and gamma-subunits of mitochondrial F1-ATPase. Specific mutations, Phe443-->Ser and Ala333-->Val in MGI2, and Thr275-->Ala in MGI5, confer on cells the ability to produce petite mutants spontaneously with deletions in mitochondrial (mt) DNA and the capacity to lose their mitochondrial genomes upon treatment with ethidium bromide. Structural integrity of the F1 complex seems to be needed for expression of the Mgi- phenotype as null mutations in MGI2 and MGI5 remove the ability to form mtDNA deletions. It is suggested that mgi mutations allow petites to survive because an aberrant F1 complex prevents collapse of the mitochondrial inner membrane potential that normally occurs on loss of mtDNA-encoded F0 subunits.

Amino Acid Sequence↗
PubMed1995

Mutations in domain I of Bacillus thuringiensis delta-endotoxin CryIAb reduce the irreversible binding of toxin to manduca sexta brush border membrane vesicles.

Site-directed mutagenesis was used to generate CryIAb mutants at the selected N-terminal positions to study the function of domain I. Structurally stable mutant proteins were tested for toxicity, receptor binding kinetics, and pore function. Substitutions of tyrosine at position 153 with arginine (Y153R) or alanine (Y153A) did not affect toxicity appreciably, whereas replacing this tyrosine with aspartic acid (Y153D) resulted in a great loss of toxicity. Mutation of alanine at position 92 to glutamic acid (A92E) almost completely abolished toxicity. The initial receptor binding was unchanged as measured by competition binding assays among all mutant proteins. Reduced pore function, however, was observed for mutants A92E and Y153D as tested by voltage clamping. Further studies with specially designed association and dissociation binding assays showed that irreversible binding of these two mutant toxins to Manduca sexta brush border membrane vesicles was significantly reduced. The decrease in irreversible binding was correlated with the changes in toxicity and may reflect a severely disturbed membrane insertion process in these two mutant toxins, leading to reduced pore function and toxicity. The results support the model that domain I is involved in membrane integration and pore formation.

Amino Acid Sequence↗
PubMed1995

Single amino acid changes in domain II of Bacillus thuringiensis CryIAb delta-endotoxin affect irreversible binding to Manduca sexta midgut membrane vesicles.

Deletion of amino acid residues 370 to 375 (D2) and single alanine substitutions between residues 371 and 375 (FNIGI) of lepidopteran-active Bacillus thuringiensis CryIAb delta-endotoxin were constructed by site-directed mutagenesis techniques. All mutants, except that with the I-to-A change at position 373 (I373A), produced delta-endotoxin as CryIAb and were stable upon activation either by Manduca sexta gut enzymes or by trypsin. Mutants D2, F371A, and G374A lost most of the toxicity (400 times less) for M. sexta larvae, whereas N372A and I375A were only 2 times less toxic than CryIAb. The results of homologous and heterologous competition binding assays to M. sexta midgut brush border membrane vesicles (BBMV) revealed that the binding curves for all mutant toxins were similar to those for the wild-type toxin. However, a significant difference in irreversible binding was observed between the toxic (CryIAb, N372A, and I375A) and less-toxic (D2, F371A, and G374A) proteins. Only 20 to 25% of bound, radiolabeled CryIAb, N372A, and I375A toxins was dissociated from BBMV, whereas about 50 to 55% of the less-toxic mutants, D2, F371A, and G374A, was dissociated from their binding sites by the addition of excess nonlabeled ligand. Voltage clamping experiments provided further evidence that the insecticidal property (inhibition of short-circuit current across the M. sexta midgut) was directly correlated to irreversible interaction of the toxin with the BBMV. We have also shown that CryIAb and mutant toxins recognize 210- and 120-kDa peptides in ligand blotting. Our results imply that mutations in residues 370 to 375 of domain II of CrylAb do not affect overall binding but do affect the irreversible association of the toxin to the midgut columnar epithelial cells of M. sexta.

Amino Acid Sequence↗
PubMed1995

Influence of genetic and environmental factors on surface expression and occupancy of IgE receptors and on histamine releasability of mast cells.

The relationship between the IgE load on mast cells and their secretory capacity when challenged with anti-IgE was studied in peritoneal cells obtained from rats of three different strains, Hooded Lister (HL), Wistar Kyoto (WKY) and Sprague-Dawley (SD). IgE was determined cytofluorometrically after labelling with FITC-conjugated anti-IgE before and after the saturation of the IgE receptors to provide a measure of the surface expression of IgE receptors (number of receptors available for bindings) as well as the IgE occupancy of the receptors (native IgE content). The secretory capacity of the mast cells was examined in vitro in terms of histamine release as a function of anti-IgE concentration. Mast cells obtained from HL and WKY rats were found to carry significantly higher levels of IgE receptors and IgE than the mast cells of SD rats bred and raised under the same conventional laboratory conditions. The mast cells of SD rats kept under barrier-maintained conditions carried significantly less IgE than the mast cells obtained from SD rats kept under conventional conditions, but their IgE receptor levels were similar. The IgE-mediated histamine-releasing capacity of the mast cells, evaluated in terms of maximum release or of the slopes of regression lines (histamine release versus anti-IgE concentration), was positively correlated to the levels of native IgE and IgE receptors in the three strains of rat combined. The mast cells obtained from WKY rats showed the highest secretory capacity in the three strains of rat examined, significantly higher than the mast cells of HL rats, even though the latter displayed similar levels of IgE and IgE receptors.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

T-cell-independent and T-cell-dependent IgE responses to the nematode Nippostrongylus brasiliensis: comparison of serum IgE and mast-cell-bound IgE.

The IgE immune response was studied in female athymic, nude (Lewis rnu/rnu) and euthymic (Lewis +/+) rats infected with the nematode Nippostrongylus brasiliensis. During the course of the infection, serum IgE levels were followed using an enzyme-linked immunosorbent assay technique (ELISA), while the surface expression and occupancy of IgE receptors on peritoneal mast cells were quantified using flow cytometry after immunolabelling with anti-IgE. The results show that the up-regulation of IgE receptors, which takes place on the mast cells of both athymic and normal rats during the early phase of the immune response, is more pronounced and longer-lasting in normal rats than in athymic ones, thereby suggesting that T cells are necessary for a full response to the parasite infection. The increased IgE occupancy observed on the mast cells during the early phase of the parasite immune response was not reflected in the serum IgE levels, which remained low during the entire infection period in athymic rats. In euthymic rats, on the other hand, there was a pronounced increase in serum IgE, as well as an increase in IgE occupancy on the mast cells, all reaching a peak level after 2 weeks of infection. However, there was no significant correlation between the serum IgE concentration and IgE occupancy or the density of IgE receptors on the mast cells of the individual euthymic rats. This indicates that the quantification of IgE occupancy on the mast cells may be a better way of detecting low-level IgE responses than the measurement of serum IgE. These findings, which were obtained in female Lewis rats, when compared with our previous findings in male rats of the same strain, suggest that sex differences may exist in terms of the intensity and duration of the IgE immune response to the parasite infection.

Animals↗
PubMed1994

Cytofluorometric quantification of IgE and IgE receptors on individual mast cells.

Information about the IgE receptor and IgE content of mast cells under different conditions in vivo is essential for further understanding the functions of the mast cell-IgE system. A cytofluorometric method for measuring cell-bound IgE on individual mast cells was therefore explored using peritoneal mast cells of Sprague-Dawley rats infected with the nematode N. brasiliensis and rat basophilic leukaemia cells (RBL-1) as experimental models. We systematically studied the effects of variables such as fixation, incubation time, temperature and concentrations of antibody on the fluorescence emission of the mast cells. Optimum conditions were selected for the quantitative measurement of IgE at the single-cell level using direct labelling with FITC-conjugated goat anti-rat IgE(Fc). Polystyrene beads with a defined fluorophor content and a fluorescent uranyl glass were used to standardise the measurement procedure. A linear relationship between fluorescence intensity and IgE concentration was obtained by fluorescence measurements on RBL-1 cells incubated in rat IgE. In the case of rat peritoneal mast cells it was possible to saturate the IgE receptors by incubating the mast cells in rat IgE. By measuring the mast cells before and after IgE incubation, the relative content of IgE, the relative number of IgE receptors and the degree of receptor saturation could be estimated. In this way we measured the IgE content of peritoneal mast cells of Sprague-Dawley rats maintained under pathogen-free conditions. The distribution of IgE content in the mast-cell populations was extremely variable. Up to 30% of the mast cells in individual populations contained little or no IgE, but very few if any of the cells lacked IgE receptors. On average, 60-70% of the receptors available for binding were occupied by IgE in these normal rats.

Animals↗
PubMed1994

Application of an immunocolloid gold technique for the ultrastructural demonstration of IgE-receptor complexes on rat mast cells.

In previous works using cytofluorometry, we demonstrated a broad range of IgE and IgE-receptor levels within individual mast cell populations with a 60 to 80% occupancy of the IgE receptors on mast cells by native IgE. This study was performed in order to confirm our previous findings using an independent method and to visualize the distribution of IgE-receptor complexes on mast cells at an ultrastructural level. For this purpose an indirect immunocolloidal gold-labelling technique has been applied. By counting the number of labelled gold particles, a relative measure of IgE-receptor surface expression and IgE occupancy of the receptors could be obtained. With respect to mast cell morphology and anti-IgE binding specificity criteria, 1% glutaraldehyde + 4% paraformaldehyde (1:1, vol/vol) was found to be the best of the seven fixatives applied in this study. This technique revealed numerous gold particles on the surface of mast cells from barrier-maintained rats (26 +/- 11 per mast cell section, mean +/- SD). Increased numbers of gold particles were counted if the mast cells were incubated with rat myeloma IgE (20 micrograms/ml) (46 +/- 33 per mast cell section, mean +/- SD). There were significantly increased numbers of gold particles on the mast cells of rats infected with N. brasiliensis (126 +/- 30 per mast cell section, mean +/- SD). This indicates that some of the IgE receptors (about 50% of the total number of IgE receptors in this case) on mast cells were occupied by native IgE and that parasite infection significantly increased the number of IgE molecules on the surface of the mast cells. These results correspond with the findings we have made using the cytofluorometric technique and confirm the large individual variations in the density of IgE receptors and IgE among the mast cells of a given cell population. Macrophages, lymphocytes and eosinophils, carrying the low-affinity IgE receptors (Fc epsilon RII), contained less than 5 (normal rats after incubation in rat IgE) or 10 (nematode-infected rats) gold particles per cell section. We also observed some non-granulated lymphocyte-like cells which bound a large number of gold particles after incubation with rat myeloma IgE (20 micrograms/ml), indicating that they contained IgE receptors Fc epsilon RI). They were interpreted as mast cell precursors which have previously been shown to exist in the peritoneal cavity.

Animals↗
PubMed1994

sir2 mutants of Kluyveromyces lactis are hypersensitive to DNA-targeting drugs.

A Kluyveromyces lactis mutant, hypersensitive to the DNA-targeting drugs ethidium bromide (EtBr), berenil, and HOE15030, can be complemented by a wild-type gene with homology to SIR2 of Saccharomyces cerevisiae (ScSIR2). The deduced amino acid sequence of the K. lactis Sir2 protein has 53% identity with ScSir2 protein but is 108 residues longer. K. lactis sir2 mutants show decreased mating efficiency, deficiency in sporulation, an increase in recombination at the ribosomal DNA locus, and EtBr-induced death. Some functional equivalence between the Sir2 proteins of K. lactis and S. cerevisiae has been demonstrated by introduction of ScSIR2 into a sir2 mutant of K. lactis. Expression of ScSIR2 on a multicopy plasmid restores resistance to EtBr and complements sporulation deficiency. Similarly, mating efficiency of a sir2 mutant of S. cerevisiae is partially restored by K. lactis SIR2 on a multicopy plasmid. Although these observations suggest that there has been some conservation of Sir2 protein function, a striking difference is that sir2 mutants of S. cerevisiae, unlike their K. lactis counterparts, are not hypersensitive to DNA-targeting drugs.

Amino Acid Sequence↗
PubMed1994

IgE receptors, IgE content and secretory response of mast cells in athymic rats.

Athymic, nude (Lewis rnu/rnu) and normal (Lewis +/+) rats were used to study the T-cell dependence of the regulation of IgE receptors and IgE content on mast cells in vivo. We estimated the number of IgE receptors and the IgE content on peritoneal mast cells using a cytofluorometric technique. The secretory capacity of the mast cells was measured in terms of histamine release as a function of anti-IgE concentration by incubation with antibodies in vitro. Two groups of rats, aged 6 and 13 weeks, were examined. The mast cells of the rats belonging to the older age group (both normal and athymic) had a higher total protein (equivalent to dry mass or size) and mediator content (heparin, histamine and 5-hydroxytryptamine) in accordance with previous findings. Mast cells of the athymic rats of both age groups contained similar levels of IgE receptors and IgE and did not differ in these respects from those of the normal rats. Of the IgE receptors available for binding, about 80% were occupied by IgE in mast cells of normal and of athymic rats in both age groups. The anti-IgE-induced histamine release of the mast cells was, however, significantly lower in athymic rats compared to the normal controls. A change in housing from barrier-maintained to conventional conditions for 2 weeks enhanced the IgE-receptor and IgE content, as well as the releasability of histamine of the mast cells of both athymic and normal rats. The basal level of IgE occupancy of the receptors on mast cells was therefore not impaired in the athymic rats, as might be inferred from previous findings of a T-cell dependence of the IgE immune response. The results further indicate that T-lymphocyte-derived cytokines appear not to be required for either the expression of IgE receptors or for their ability to acquire IgE on mast cells, but such factors seem to enhance the release of histamine following the cross-linkage of the IgE receptor on mast cells in normal conditions.

Aging↗
PubMed1994

Monoclonal antibodies specific for ohmefentanyl.

Ohmefentanyl (Ohm, N[1-(beta-hydroxy-beta-phenylethyl)-3-methyl-4- piperidyl]-N-phenylpro-pronamide), designed and synthesized by our laboratory, is a highly selective mu receptor agonist. After somatic cell fusion between splenocytes of BALB c mice, immunized by Ohm-BSA conjugate and NS-1 myeloma cells, 2 lines of hybridoma (D2 and F4) secreting monoclonal anti-Ohm antibodies (MAb) were obtained. Saturation and competition experiments showed that MAb-D2 and MAb-F4 bound to Ohm-BSA with high affinity and high specificity. Using radioligand binding assay and bioassay, we also found that MAb-D2 and MAb-F4 inhibited [3H] Ohm binding to rat brain opioid receptors in a dose-dependent manner and antagonized the effect of Ohm on the contraction of guinea pig ileum induced by electric field stimulation. These results suggested that MAb-D2 and MAb-F4 were 2 monoclonal antibodies specific for Ohm and could be useful as functional antagonists of Ohm.

Animals↗