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X Yang

Publications and source records attributed to X Yang.

At least 1,063 records · Page 59Linked to original sources
PubMed1993

A simple, sensitive, dual mAb based ELISA for murine gamma interferon determination: comparison with two common bioassays.

Three assays of murine IFN gamma are compared in terms of sensitivity, intra- and inter-assay variability, specificity and simplicity. The widely used viral inhibition assay requires 48 hours, necessitates continuous maintenance and optimization of fibroblast growth, and exhibits the lowest sensitivity. Inhibition of WEHI-279 B cell [3H]thymidine incorporation requires 48-60 hours to quantitate IFN gamma production, can be subject to non-specific inhibition, and is also labor intensive. In both bioassays, specificity must be determined by the analysis of duplicate samples in the presence of neutralizing, IFN gamma-specific mAb. In contrast, a 24 hour, dual mAb ELISA, in which IFN gamma is captured by immobilized, purified rat IgG1 XMG 1.2 mAb and identified with biotinylated mAb R4-6A2 and streptavidin-alkaline phosphatase detects IFN gamma production > 0.05 U/ml. The quantitative range in this assay is typically from 1-100 U/ml. In addition to providing the greatest specificity and shortest duration, this ELISA exhibits the lowest coefficient of variation of the three assays compared. Collectively, assay characteristics such as sensitivity, absence of interference by other proteins, reproducibility, speed and simplicity support the conclusion that this dual mAb based sandwich ELISA represents a substantial improvement over inhibition of viral cytopathic effect or inhibition of WEHI-279 bioassays for characterization of antigen- or mitogen-driven IFN gamma production.

Animals↗
PubMed1993

Male transmission of linear plasmids and mitochondrial DNA in the fungus Neurospora.

One of the general rules of heredity is that in anisogamous matings genetic elements in organelles are inherited maternally. Nevertheless, there are cases of paternal transmission, both as rare exceptions, and as regular modes of inheritance. We report two new cases of paternal transmission in crosses of the model fungus Neurospora. First, we show leakage of a linear plasmid from males, the first case in fungi and the second in eukaryotes. Transmission frequencies ranged from 1% to 15% in different crosses, but some crosses showed no detectable male transmission. Second, we show leakage of male mitochondrial DNA (mtDNA), the second case in fungi. Some of the resulting progeny have only the male mtDNA type, but some are heteroplasmons. Heteroplasmons show novel restriction fragments attributable to recombination or rearrangement. Heteroplasmy of mtDNA through male transmission has not been reported previously in any eukaryote. In addition we have shown paternal leakage of circular mitochondrial plasmids, supporting another reported case. In a male bearing a linear and a circular plasmid, these plasmids and the mtDNA are transmitted in different combinations. These results show a potential for mitochondrial segregation and assortment during the sexual cycle in anisogamous fungi, pointing to more potential avenues for novel associations between genomic compartments, and between genomic and extragenomic elements.

Crosses, Genetic↗
PubMed1993

Plasmid suppressors active in the sexual cycle of Neurospora intermedia.

We have discovered that, in certain crosses of natural isolates of Neurospora intermedia, linear and circular mitochondrial plasmids of the maternal parent are not transmitted to the progeny. This contrasts with the maternal transmission of organellar genetic elements generally observed in crosses between laboratory strains and between other natural isolates. Formally, failure of plasmid transmission is a type of plasmid suppression. The present cases represent the first report of plasmid suppressors in natural populations of fungi. Strains used as female parents can transmit or not transmit plasmids depending on the strain used as male parent. Males that act to suppress in one cross fail to suppress in others. Therefore, the suppression of plasmids depends on a strain-specific interaction and is not determined exclusively by the males. Since suppression is a specific interaction we inferred that it must be genetically based and tested this hypothesis by seeking segregation of suppressed and nonsuppressed phenotypes in octads. Segregation of the original full suppression of all plasmids was indeed observed in each of the three sets of testcrosses examined. The interaction type of suppression must be initiated in ascogenous tissue during the sexual cycle. It is a nonautonomous type of suppression, affecting all descendent cells. In any one case of suppression, either one, several, or all plasmids can be lost. Both linear and circular plasmids can be eliminated by the same suppressor genotype. In addition, several strains were found to contain suppressors that act after ascospore delineation. This autonomous type of suppression has been observed previously in laboratory strains, but not in natural isolates. All the cases of plasmid suppression identified in this study involved a range of apparently neutral circular and linear plasmids. Using one senescent Kalilo strain of N. intermedia, we did not detect any case of suppression of the senescence-determining linear plasmid kalDNA.

Crosses, Genetic↗
PubMed1993

The role of a Drosophila POU homeo domain gene in the specification of neural precursor cell identity in the developing embryonic central nervous system.

The Drosophila embryonic central nervous system (CNS) is derived from a stereotypic array of progenitor stem cells called neuroblasts (NBs). Each of the approximately 25 NBs per hemisegment undergoes repeated asymmetric divisions to produce, on average, 5-10 smaller ganglion mother cells (GMCs); each GMC, in turn, divides to produce two neurons. We demonstrate that the protein product encoded by a POU homeo domain gene (dPOU28/pdm-2) is expressed in the cell nuclei of a subset of NBs and GMCs. In the wild-type animal, GMC-1 is the only identified cell in the NB4-2 lineage that expresses dPOU28 protein to a high level, and it divides to produce the RP2 neuron and a second cell of unknown fate. Our results suggest that the presence of ectopically induced dPOU28/pdm-2 protein in the progeny of GMC-1 is sufficient to cause both of these cells to adopt their parental GMC-1 cell fate, leading to duplication of the RP2 neuron (and its sister cell) on the basis of both immunological and morphological criteria. These observations clearly implicate a role for dPOU28/pdm-2 in the specification of GMC-1 cell identity in the NB4-2 lineage and possibly in the specification of cell fate in other NB lineages in the developing embryonic CNS.

Animals↗
PubMed1993

A small plasmid, pCA2.4, from the cyanobacterium Synechocystis sp. strain PCC 6803 encodes a rep protein and replicates by a rolling circle mechanism.

Different cryptic plasmids are widely distributed in many strains of cyanobacteria. A small cryptic plasmid, pCA2.4, from Synechocystis strain PCC 6803 was completely sequenced, and its replication mode was determined. pCA2.4 contained 2,378 bp and encoded a replication (Rep) protein, designated RepA. An analysis of the deduced amino acid sequence revealed that RepA of pCA2.4 has significant homology with Rep proteins of pKYM from Shigella sonnei, a pUB110 plasmid family from gram-positive bacteria, and with a protein corresponding to an open reading frame in a Nostoc plasmid and open reading frame C of Plectonema plasmid pRF1. pKYM and pUB110 family plasmids replicate by a rolling circle mechanism in which a Rep protein nicks the origin of replication to allow the generation of a single-stranded plasmid as a replication intermediate. RepA encoded by pC2.4 was expressed in Escherichia coli cells harboring a vector, pCRP336, containing the entire repA gene. The observed molecular weight of RepA was consistent with the value of 39,200 calculated from its deduced amino acid sequence, as was the N-terminal sequence analysis done through the 12th residue. Single-stranded plasmid DNA of pCA2.4 that was specifically degraded by S1 nuclease was detected in Synechocystis cells by Southern hybridization. These observations suggest that pCA2.4 replicates by a rolling circle mechanism in Synechocystis cells.

Amino Acid Sequence↗
PubMed1993

Mutations in the type II 3 beta-hydroxysteroid dehydrogenase gene in a patient with classic salt-wasting 3 beta-hydroxysteroid dehydrogenase deficiency congenital adrenal hyperplasia.

Inherited adrenal and gonadal 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD) deficiency is most likely caused by a mutation of the type II 3 beta-HSD gene. Cloning and sequencing of exons I-II, III, and IV and portions of the adjacent introns, amplified by polymerase chain reaction using primers specific for the type II gene, in one male pseudohermaphrodite with salt-wasting classic 3 beta-HSD deficiency congenital adrenal hyperplasia revealed the same mutation in all nine clones of exon IV consisting of a missense mutation at codon 248 [GTC(Val)-->AAC(Asn)] followed by a frameshift mutation at codon 249 [CGA (Arg)-->TA], resulting in a stop codon TAG, and normal sequences of exon I-II and III and the adjacent portions of introns. The same codon 248 and 249 mutations were found on one clone of his mother's DNA, but two other clones revealed normal sequences. These data indicate a homozygous combined missense/frameshift mutation in exon IV of the type II 3 beta-HSD gene resulting in severe salt-wasting adrenal and gonadal 3 beta-HSD deficiency in the patient.

3-Hydroxysteroid Dehydrogenases↗
PubMed1993

Inherited congenital adrenal hyperplasia in the rabbit is caused by a deletion in the gene encoding cytochrome P450 cholesterol side-chain cleavage enzyme.

Congenital adrenal hyperplasia (CAH) comprises a family of inherited human disorders caused by a defect in cortisol biosynthesis. We previously reported absent cholesterol side-chain cleavage enzyme cytochrome P450 (P450scc) expression in rabbits affected with CAH. Further molecular studies via Southern blotting analyses, using a full-length human P450scc cDNA probe and a cloned rabbit P450scc cDNA probe, demonstrated the absence of P450scc DNA fragments in CAH animals. Reverse transcriptase-based polymerase chain reactions revealed that P450scc mRNA was not detectable in the adrenals of CAH rabbits, confirming the previous findings of absent P450scc gene expression by Northern and Western blotting. Cloning and sequencing of a 1336-basepair fragment of rabbit P450scc cDNA (85% of the coding sequence) revealed an approximately 80% identical nucleotide sequence and a 76% identical amino acid sequence compared to the human P450scc cDNA. We conclude that a large deletion mutation in the P450scc gene is most likely responsible for the absent P450scc gene expression resulting in the lethal and feminizing form of CAH in the rabbit. Further investigation of adrenal and gonadal steroidogenic enzyme gene expression in this CAH animal model will provide a greater understanding of the molecular genetics of CAH, while wild-type P450scc gene transfer experiments using CAH adrenals in vitro or in vivo will ultimately characterize the molecular basis of CAH and provide a foundation for CAH gene therapy modality.

Adrenal Hyperplasia, Congenital↗
PubMed1993

Binding of stallion spermatozoa to the equine zona pellucida after coculture with oviductal epithelial cells.

The objective of this study was to determine whether coculture of stallion spermatozoa and mare oviductal (uterine tubal) epithelial cells induced sperm cell capacitation in vitro. Capacitation as determined by zona binding and chlortetracycline staining of the sperm cells was compared for stallion spermatozoa: (1) incubated with medium alone (negative control), (2) treated with calcium ionophore A23187 (positive control) or (3) cultured with mare oviductal epithelial cells (OEC) for 4 h. Chlortetracycline staining patterns of sperm cells bound to the zonae were used to group spermatozoa as uncapacitated, capacitated or acrosome reacted. The zonae and attached spermatozoa were stained for evaluation after initial binding (pulse) and after 1 h of co-incubation (chase). More sperm cells in the ionophore and OEC treatments bound to the zonae at both the pulse and chase than in control medium (P < 0.001). More bound sperm cells were capacitated at the pulse, and acrosome reacted at the chase, for the ionophore and co-culture groups than for the controls (P < 0.001). Staining patterns for sperm cells not bound to the zona pellucida in each of the treatments differed (P < 0.05) from the population of sperm cells that bound to the zona pellucida. There was a higher percentage of capacitated spermatozoa and a lower percentage of acrosome-reacted spermatozoa bound to the zonae at the pulse than were represented in the treatment suspensions of sperm cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of Astragalus membranaceus on electrophysiological activities of acute experimental Coxsackie B-3 viral myocarditis in mice.

A murine model for observing the effect of Astragalus membranaceus (AM) on electrophysiological action of the right ventricular myocardium was developed in 4-week-old male BALB/c mice infected with coxsackie B-3 virus (CB3V). The conventional microelectrode technique and a real-time data processor system were used. The survival rate in AM-treated mice was much higher and the percentage of abnormal action potential was much lower than those in infected control mice (P < 0.05, P < 0.01, respectively). Some abnormal electrophysiological parameters, such as APA, OS and Vmax, in infected myocardium were found to be improved by AM treatment. The results suggest that AM may be valuable in the prevention and treatment of acute viral myocarditis involving coxsackie B viruses.

Action Potentials↗
PubMed1993

Allergen-dependent induction of interleukin-4 synthesis in vivo.

The ability of freshly derived T cells to produce interleukin-4 (IL-4) remains controversial. Many groups report that freshly derived antigen-, allogen- or mitogen-activated CD4 T cells produce almost exclusively IL-2, acquiring the capacity to produce a spectrum of cytokines following culture, rest and restimulation. In contrast, it is demonstrated here that in vivo exposure to protein allergens induces rapid, co-ordinate activation of IL-4 and interferon-gamma (IFN-gamma) gene expression. Overnight culture of spleen cells obtained from mice immunized with ovalbumin (OVA) or ragweed extract (RAG) in alum adjuvant elicits strong IL-2 and IL-4 responses within 14 hr of culture. T cells from mice immunized with allergen in complete Freund's adjuvant (CFA) generate strong IL-2 and IFN-gamma production, but virtually no IL-4, while unimmunized mice do not respond detectably to allergen in vitro (< 1 U). Unlike the differential pattern of cytokine synthesis observed following antigen-specific in vitro restimulation, cultures derived from naive and allergen-primed animals yield virtually equivalent IL-4, IL-2 and IFN-gamma synthesis upon polyclonal restimulation with anti-CD3 mAb 145-2C11 or concanavalin A (Con A), a finding which underlines the importance of the experimental conditions selected for in vitro analysis of in vivo cytokine gene expression. Collectively, the results indicate that the mode of immunization is critical to the pattern of cytokine response elicited and consequently to the type of antibody response which develops.(ABSTRACT TRUNCATED AT 250 WORDS)

Allergens↗
PubMed1993

[Monitoring of microcirculation of pedicle skin flaps and early division of their pedicles].

In experimental study, microcirculation in 7 human pedicle skin flaps was monitored continuously by laser Doppler flowmetry (LDF), skin thermometer, and clinical tests. The changes of the microcirculation in flap were divided into three phases: rapid rising (1-4 days after operation); plateau (4-7 days after operation); and slow rising (7 days after operation). The plateau stage was considered as the "critical" period. Early division of the flap within the plateau and the slow rising causes flap survival (100%). In clinical application, we put forward the following objective criteria of early division of pedicle skin flap. The value (PU) of LDF monitoring the flap returned to the preoperative level. The value (PU) returned to or exceeded 50% of that (PU) determined before application of the tourniquet. The skin temperature value between before and after application of the tourniquet was less than 1 degree C. The targets of clinical test showed no significant changes beyond 1 hour with the tourniquet. The time of division was decreased to 6-8 postoperative days in our clinical application.

Adolescent↗
PubMed1993

[Study on determination of polyactin A by ELISA].

Sandwich ELISA and two-step competition ELISA were utilized to determine polyactin A. After optimization of the experimental conditions, microtiter plates were coated with the rabbit antibody solution and evaporated to dryness at 37 degrees C. The coated microtiter plates were incubated first with the analyte, then with the HRP-labelled antibody (sandwich procedures), or with the HRP-labelled polyactin A (competition procedures), and absorbance was measured after coloration. The whole determination took less than 4 hours, excluding the coating procedure, which is faster than the routine complement fixation method. The coated microtiter plates can be well after over three months of storage at 4 degrees C. The sensitivity obtained was 0.64-7.4 ng/well for the sandwich method or 0.6-1.2 micrograms/well for the competition method.

Adjuvants, Immunologic↗
PubMed1993

[Fast identification of Salmonella by chemiluminescent photographic detection].

Salmonella anatis was identified by the chemiluminescent photographic detection technique established in this lab. The horseradish peroxidase labelled antibody was incubated with the bacteria immobilized on nitrocellulose film; after washing, the film was contacted with a filter paper with absorbed chemiluminescence substrate solution. Twenty minutes of exposure of the chemiluminescence produced to X-ray film gave the positive results. As few as one hundred bacteria could be detected in about 2h. The tests showed that the specificity of the method is good.

Luminescent Measurements↗
PubMed1993

[Hip prosthetic stem biological fixation by compound bone-cement].

Thirty rabbits were subjected to hemiarthroplasty for the right hip. The prosthetic stems were fixed by DBM + bone-cement in group I, BMG + bone-cement in group II, bone-cement only in group III, and uncemented inserting stem in group IV. They were periodically examined roentgenologically, histologically and biomechanically. Group I and II attained early mechanical fixation and new bone grew into the compound bone-cement (CBC), which was fused together with the host bed. Their shearing strength of the contact surface of CBC was increased with time. The differences between group I, II and group III, IV were obvious (P < 0.01). In later stage, group III showed bone absorption and destruction, and pseudo-membraneous tissue between the bone and cement. Group IV failed in fixation and had loosening and subsidence of the stems even in the early stage. The histology and biomechanics of compound bone-cement were also discussed.

Animals↗