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Biomedical subjects

B X Chen

Publications and source records attributed to B X Chen.

At least 19 recordsLinked to original sources
PubMed2001

Preliminary observations on the concentrations of serum luteinizing hormone and follicle-stimulating hormone during gestation in bactrian camels (Camelus bactrianus).

The concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the serum of the Bactrian camel (Camelus bactrianus) throughout pregnancy were analysed by radioimmunoassay. The samples were withdrawn at intervals of half a month. The serum LH concentrations varied significantly between 2.2+/-0.9 and 20.3+/-18.8 ng/ml during the pregnancy, with the highest value on the day of artificial insemination, which indicated that a preovulatory LH peak appeared. Thereafter, the LH concentration tended to fall, reaching a fairly constant low level by the eighth month of pregnancy. The serum FSH concentrations varied between 7.0+/-0.2 and 28.9+/-0.4 ng/ml during gestation, with the peak value being reached at 4.5 months, followed by a marked drop to 7.0+/-0.2 ng/ml at 7.5 months.

Animals↗
PubMed2001

Isolation of ovulation-inducing factors in the seminal plasma of Bactrian camel (Camelus bactrianus) by DEAE-cellulose chromatography.

Ovulation in the Bactrian camel (Camelus bactrianus) depends upon the ovulation-inducing factor in the seminal plasma; however, little research has been conducted to isolate and identify the factor. The current study attempts to isolate and identify the bioactive fractions from the seminal plasma of Bactrian camel. The seminal plasma was fractionated by diethylamino-ethylcellulose (DEAE)-cellulose chromatography and five protein fractions were obtained. The bioactive of each fraction was estimated by rat pituitary tissue culture in vitro and by the intramuscular injection of the bioactive fraction to the female camels in vivo. The concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary culture media before and 6 h after the addition of each fraction and in the peripheral blood plasma collected from the camel immediately before and hourly after the injection of the active fraction were measured by radioimmunoassay. The results demonstrated that the third fraction (L3) had the bioactive potential to stimulate the release of LH in vitro from 11.82 +/- 1.77 to 25.63 +/- 3.84 mIU/ml after the addition of L3 to the culture media. The in vivo concentrations of LH in the blood plasma of the camel increased from 6.43 +/- 0.14 before to 15.50 +/- 2.64 ng/ml 6 h after injection of L3. However, the concentrations of FSH did not show any significant changes either in vitro or in vivo. The results clearly demonstrated the existence of LH-releasing associated fractions in the seminal plasma that appears to be separated by DEAE-cellulose matrix and the isolated L3 fraction might be the ovulation-inducing factor or one of its components.

Animals↗
PubMed2001

[Linkage analysis and mutation detection of GRIA3 in Smith--Fineman--Myers syndrome].

To determine the role of GRIA3 in the etiology of Smith--Fineman--Myers syndrome (SFMS), polymorphic short tandem repeats within GRIA3 gene were genotyped by PCR and denaturing polyacrylamide gel electrophoresis to test linkage between GRIA3 and the gene responsible for SFMS. The open reading frame of GRIA3 was detected for mutation by PCR amplification and direct sequencing in affected and normal males from SFMS family. One of the two short tandem repeats was informative in SFMS family. Tight linkage between SFMS locus and GRIA3 gene was established by STR3 within GRIA3 gene. No disease--causing mutation was found within the open reading frame of GRIA3 gene. The disease in SFMS family from Shandong (China) is not caused by the mutation within open reading frame of GRIA3 gene.

Abnormalities, Multiple↗
PubMed2000

X-ray crystal structure of an anti-Buckminsterfullerene antibody fab fragment: biomolecular recognition of C(60).

We have prepared a monoclonal Buckminsterfullerene specific antibody and report the sequences of its light and heavy chains. We also show, by x-ray crystallographic analysis of the Fab fragment and by model building, that the fullerene binding site is formed by the interface of the antibody light and heavy chains. Shape-complementary clustering of hydrophobic amino acids, several of which participate in putative stacking interactions with fullerene, form the binding site. Moreover, an induced fit mechanism appears to participate in the fullerene binding process. Affinity of the antibody-fullerene complex is 22 nM as measured by competitive binding. These findings should be applicable not only to the use of antibodies to assay and direct potential fullerene-based drug design but could also lead to new methodologies for the production of fullerene derivatives and nanotubes as well.

Amino Acid Sequence↗
PubMed1998

Antigenicity of fullerenes: antibodies specific for fullerenes and their characteristics.

The recent interest in using Buckminsterfullerene (fullerene) derivatives in biological systems raises the possibility of their assay by immunological procedures. This, in turn, leads to the question of the ability of these unprecedented polygonal structures, made up solely of carbon atoms, to induce the production of specific antibodies. Immunization of mice with a C60 fullerene derivative conjugated to bovine thyroglobulin yielded a population of fullerene-specific antibodies of the IgG isotype, showing that the immune repertoire was diverse enough to recognize and process fullerenes as protein conjugates. The population of antibodies included a subpopulation that crossreacted with a C70 fullerene as determined by immune precipitation and ELISA procedures. These assays were made possible by the synthesis of water-soluble fullerene derivatives, including bovine and rabbit serum albumin conjugates and derivatives of trilysine and pentalysine, all of which were characterized as to the extent of substitution and their UV-Vis spectra. Possible interactions of fullerenes with the combining sites of IgG are discussed based on the physical chemistry of fullerenes and previously described protein-fullerene interactions. They remain to be confirmed by the isolation of mAbs for x-ray crystallographic studies.

Animals↗
PubMed1998

Serum progesterone and 17 beta-estradiol concentrations during pregnancy of Bactrian camel (Camelus bactrianus).

Serum progesterone and 17 beta-estradiol during pregnancy in the Bactrian camel were measured by radioimmunoassay. Serum progesterone concentrations increased by 15 d after artificial insemination (AI) and remained elevated throughout most of gestation, the mean concentrations (3.06 +/- 0.49 to 8.51 +/- 4.80 ng/mL) were similar to those reported for many species during the same stage of pregnancy. Serum 17 beta-estradiol increased significantly from 11 m.o. of pregnancy with peak mean concentrations of 617.47 +/- 32.56 pg/mL at the 11.5 m.o.

Animals↗
PubMed1997

Antibodies to oxidative DNA damage: characterization of antibodies to 8-oxopurines.

The 8-oxo-7,8-dihydropurines (8-oxopurines) are important cellular premutagenic lesions produced in DNA by free radicals. Specific antibodies were prepared to detect these lesions. For antigens, 8-oxo-7,8-dihydroadenosine (8-oxoAdo) and 8-oxo-7,8-dihydroguanosine (8-oxoGuo) were synthesized from the bromonucleosides, and the immunogens were produced by conjugating these to either bovine serum albumin or rabbit serum albumin by the periodate method. Polyclonal antibodies specific for the haptens were elicited from rabbits immunized with the BSA conjugates. The antibodies to 8-oxoAdo (anti-8-oxoAdo) and 8-oxoGuo (anti-8-oxoGuo) precipitated the homologous antigens in an Ouchterlony gel diffusion assay and no cross-reactivity was observed toward the normal nucleosides or to the heterologous 8-oxopurine. Specificity was also examined by hapten inhibition of antibody reactivity with the homologous conjugates using ELISA. For anti-8-oxoAdo, the IC50 for 8-oxoAdo was 8 mumol/L and 8-bromoadenosine, guanosine, and inosine did not inhibit, even at concentrations of 1.25 mmol/L. Similarly, the IC50 for anti-8-oxoGuo for 8-oxoGuo was 0.1 mumol/L. 8-Methoxyguanosine also inhibited the reaction but was about 500-fold less effective than the eliciting hapten. Other nucleosides tested did not inhibit at concentrations up to 100 mumol/L. Both antibodies could easily detect the corresponding damage in x-irradiated f1 DNA at a dose of 7.5 Gy and both antibodies recognized the corresponding lesion in duplex DNA; however, with anti-8-oxoGuo the signal was reduced about 50% compared to single-stranded DNA. In order to determine the exact amount of each lesion produced in irradiated DNA, and to standardize the ELISA signal, both products were measured after alkaline phosphatase digestion of x-irradiated calf thymus DNA using high-pressure liquid chromatography (HPLC) coupled to an electrochemical detector. Anti-8-oxoGuo could detect ten 8-oxoG residues and anti-8-oxoAdo could detect two 8-oxoA residues per 10,000 nucleotides. Thus, these antibodies should be useful for the detection and measurement of 8-oxopurines in cellular DNA.

Adenosine↗
PubMed1996

A strategy for immunohistochemical signal enhancement by end-product amplification.

We report a novel strategy, called end-product (EP) amplification, capable of enhancing the sensitivity of immunohistochemical procedures by about an order of magnitude or more. The strategy employs an antibody (anti-EP) to the product generated by the action of horseradish peroxidase on 3,3'-diaminobenzidine (DAB), and can be extended to the products of other enzymes as well, e.g., alkaline phosphatase. Amplification is the consequence of the ability of anti-EP to detect the multiplicity of product moelcules resulting from the turnover of substrate by a single enzyme molecule. The subsequent detection of anti-EP was by biotinylated goat anti-rabbit antibody, followed by avidin-peroxidase and DAB or by avidin-alkaline phosphatase and Vector Red. Further amplification can be accomplished by repeated cycles of the protocol. Anti-EP was produced by immunization with a bovine serum albumin (BSA) conjugate of a soluble polymer of DAB, prepared by a carefully controlled reaction of DAB with horseradish peroxidase and hydrogen peroxide. Coupling to BSA (and to RSA) was accomplished with glutaraldehyde. The titer of anti-EP was established by ELISA. Formalin-fixed, paraffin-embedded sections of five cases of Hodgkin's disease and five tonsils with follicular hyperplasia were immunolabeled for the following lymphoid markers: CD3, CD20, CD30, CD45RA, and CD68. EP amplification with anti-EP was also applied to cases of CMV pneumonia and cerebral toxoplasmosis to determine whether this procedure could improve detection of the infectious agents. Immunolabeling of the primary antibody was performed by the avidin-biotin-peroxidase technique with DAB as the reaction substrate. The specificity of EP amplification was tested by demonstrating binding of anti-EP with Vector Red with the generation of a fluorescence end-point. There was complete congruence in the distribution of the DAB signal and the red immunofluorescence representing EP amplification. The intensity of the DAB signal was increased as much as 16-fold by EP amplification, making possible a reduction in the amount of the primary antibody by as much as 85-90%. Sensitivity also increased with respect to weakly expressed antigens and low concentrations of infectious agents.

3,3'-Diaminobenzidine↗
PubMed1995

Role of the sympathoadrenal axis in the cardiovascular response to cocaine in conscious unrestrained rats.

We investigated the role of peripheral sympathetic neurons and the adrenal medulla in the cardiovascular responses to cocaine in conscious, unrestrained Sprague-Dawley rats. Surgical adrenal demedullation (ADM) and/or chemical peripheral sympathectomy was used to eliminate one or both components of the sympathoadrenal axis. Phentolamine (5 mg/kg i.v.) was used to evaluate whether cocaine elicited epinephrine (EPI) release from the adrenal medulla. Significant EPI release by cocaine would result in "epinephrine reversal" after phentolamine pretreatment. Cocaine (2.5 mg/kg i.v.) was used in all experiments except the dose-response relationship study. In normal rats, cocaine caused a transient increase in mean blood pressure (MBP). Pretreatment with phentolamine reversed this BP response and this depressor effect was blocked by propranolol (2 mg/kg i.v.) suggesting that the pressor effect of cocaine was mediated by EPI. Chemical sympathectomy alone partially inhibited the pressor effect of cocaine, but pretreatment with phentolamine still reversed the residual action of cocaine on MBP at this time. Two weeks after ADM, the effect of cocaine on MBP was not significantly different from that of the sham-operated rats. However, pretreatment with phentolamine inhibited but did not reverse the effect of cocaine on MBP at that time. In rats with both ADM and chemical sympathectomy, cocaine caused only a decrease in MBP that was not blocked by propranolol or atropine methylnitrate, presumably because of its direct depressive actions. Results of this study suggest that both peripheral sympathetic neurons and the adrenal medulla play important roles in the cardiovascular actions of cocaine.

Adrenal Medulla↗
PubMed1995

Cyclophilin binding to the human immunodeficiency virus type 1 Gag polyprotein is mimicked by an anti-cyclosporine antibody.

Human immunodeficiency virus type 1 is unique among retroviruses in that infectivity requires specific incorporation into virions of the cellular protein cyclophilin A through interactions with the Gag polyprotein. Here we show that monoclonal antibody B11 1.4, which recognizes a cyclophilin-binding epitope on cyclosporine, detects denatured or native human immunodeficiency virus type 1 capsid. B11 1.4 does not recognize the capsids of other retroviruses, and binding is inhibited by cyclosporine or by cyclophilin A.

Amino Acid Isomerases↗
PubMed1994

Idiotypic mimicry and the assembly of a supramolecular structure: an anti-idiotypic antibody that mimics taxol in its tubulin-microtubule interactions.

Taxol, originally extracted from the bark of the western yew, Taxus brevifolia, is reportedly the first of a new class of anti-cancer agents. It acts by promoting and irreversibly stabilizing microtubule assembly, thus interfering with the dynamic processes required for cell viability and multiplication. With the aim of using immunological techniques to study the mechanism of action of taxol, a monoclonal anti-idiotypic antibody that mimics taxol was prepared, using an auto-anti-idiotypic strategy. It and its Fab fragment inhibited the binding of [3H]taxol to microtubules. Moreover, like taxol, both promoted the assembly of tubulin into microtubules. These findings provide an example of an anti-idiotypic antibody capable of assembling an organized supramolecular structure from soluble cellular components. In addition, it further establishes the ability of anti-idiotypic antibodies to be functional mimics of ligand molecules bearing no structural similarity to immunoglobulins. The variable regions of the antibody have been sequenced. With the exception of the complementarity-determining region 3, the sequence of the heavy chain variable region is strikingly similar to that of an anti-idiotypic antibody raised to anti-insulin. The finding that a polypeptide can mimic taxol raises the possibility that taxol acts as a peptidomimetic compound that interferes with the function of an endogenous polypeptide.

Amino Acid Sequence↗
PubMed1994

[Experimental study on the processed drug of castor seeds in the therapy of pulmonary carcinoma].

In this study, castor seeds were processed by one of the traditional Chinese methods, LD50 was measured and tumor inhition tests in nude mice bearing human pulmonary carcinoma were conducted. The results showed that the processing method was able to lower the toxicity of castor seeds and maintain their antitumor effect, thus providing an experimental basis for oral administration of castor seeds in the therapy of pulmonary carcinoma.

Adenocarcinoma↗
PubMed1994

Percutaneous transluminal excimer laser coronary angioplasty. Clinical report of six cases.

Six patients with 95% to 100% occluded atherosclerotic lesions underwent percutaneous transluminal excimer laser coronary angioplasty (PTELCA). Among them, 5 were male and 1 was female; their age ranged from 28 to 66 years. Four patients had LAD stenosis and 2 LCX lesions. Acute angiographic and clinical success was achieved in all patients but one, with a success rate of 83.3%. It was demonstrated that PTELCA is a safe and effective therapy for selected patients with coronary artery disease.

Adult↗
PubMed1993

Human mononuclear phagocytes express adenosine A1 receptors. A novel mechanism for differential regulation of Fc gamma receptor function.

Using monoclonal anti-adenosine A1 receptor antibodies that bind the A1 receptor ligand binding site, we demonstrate that A1 receptors are expressed on cultured monocytes and rheumatoid synovial fluid mononuclear phagocytes. This finding is associated with the acquisition of reactivity with selective adenosine A1 receptor agonists and is temporally coordinated with the induction of adenosine A2 receptors on cultured monocytes. In a rapid, concentration-dependent fashion, these two distinct adenosine receptors modulate Fc gamma receptor-mediated phagocytosis, a response critical to the pathogenesis of immune complex diseases. Occupancy of A1 receptors by N6-cyclopentyladenosine (an A1-specific adenosine analogue) or mAb AA1 (an anti-A1 mAb) results in a potent stimulation that is blocked by adenosine receptor antagonists. This A1 receptor-induced enhancement of Fc gamma receptor-mediated phagocytosis is a consequence of preferential augmentation of Fc gamma RI function, suggesting distinct mechanisms for receptor-effector coupling of Fc gamma receptor families. In contrast, ligation of A2 receptors by A2-specific agonists decreases Fc gamma receptor-mediated phagocytosis in cultured monocytes. The opposing effects of adenosine A1 and A2 receptors allow for a concentration-dependent feed-back loop that responds more rapidly than effects elicited by other endogenous modulators. Low concentrations of adenosine are proinflammatory providing enhanced Fc gamma receptor function via A1 receptors, whereas higher concentrations that can occur with tissue damage are anti-inflammatory providing inhibition via A2 receptors. This rapid and potent modulation of Fc gamma receptor-mediated function suggests that adenosine is an important local regulator of the inflammatory response.

Adenosine↗
PubMed1993

Characterization of polyclonal and monoclonal anti-taxol antibodies and measurement of taxol in serum.

Anti-taxol antibodies were generated in the rabbit using a taxol-bovine serum albumin conjugate prepared from 2'-succinyltaxol using a mixed anhydride procedure. Immunization with 2'-succinyltaxol-bovine serum albumin gave rise to polyclonal anti-taxol antibodies. By a radioimmunoassay using [3H]taxol, a standard curve gave a 50% inhibitory concentration of 1.0 nM. Taxol levels in human serum could be measured, with the lower limit of detection and measurement being 0.1 nM or 0.085 ng/ml. Two mouse monoclonal anti-taxol antibodies were isolated by immunizing BALB/c mice with the same antigen. One was an immunoglobulin G1 (69E4A8E) and the other was immunoglobulin M (29B7B3C). The specificity of these antibodies was determined by a competitive enzyme-linked immunosorbent assay with taxol and 10 different related derivatives and analogues. 29B7B3C had higher binding affinities for biologically active derivatives and markedly lower affinities for inactive derivatives; i.e., the specificity was consistent with the results of tubulin disassembly and cytotoxicity studies using the same taxol derivatives, making it suitable for screening for taxol or taxol-like compounds in extracts of natural products. 69E4A8E recognized the benzamidocarbamyl group at the C-3' position of taxol and had a lower affinity for other active compounds with different substitutions. Taxol levels in human serum could be detected and measured by 69E4A8E using a competitive enzyme-linked immunosorbent assay. The lower limit of measurement was about 50 nM or approximately 42 ng/ml. Similar measurements could be made by radioimmunoassay.

Animals↗
PubMed1993

Immunoassay of taxol and taxol-like compounds in plant extracts.

A mouse monoclonal anti-taxol antibody (69E4A8E) and a rabbit polyclonal anti-taxol antiserum were used to measure taxol levels in plant extracts in a double-blind experiment in conjunction with assays by HPLC. 69E4A8E was previously shown by ELISA to be specific for taxol with only a slight cross reaction with another bioactive compound, cephalomannine; the antiserum, on the other hand, was, by radioimmunoassay (RIA), essentially equally reactive with taxol and cephalomannine. Immunoassays of the plant extracts gave results in agreement with that found by HPLC, suggesting that the antibodies can be used in simple routine procedures for the quantification of taxol or taxol-like compounds in extracts of plants or other potential natural sources.

Animals↗