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Y Ma

Publications and source records attributed to Y Ma.

At least 559 records · Page 31Linked to original sources
PubMed1992

Characteristics of toxin-neutralization by anti-tetanus human monoclonal antibodies directed against the three functional domains [A], [B] and [C] of the tetanus toxin molecule and a reliable method for evaluating the protective effects of monoclonal antibodies.

Five anti-tetanus human monoclonal antibodies (MAbs) produced by hybrid cell lines we established previously were characterized. Their abilities to neutralize tetanus toxin in vitro and to protect mice against challenge with toxin were studied by observing the changes in the progress of symptoms in mice. Immunostaining showed that MAbs MAb-G4 and G2 recognized the N-terminal domain, [A] and the C-terminal domain, [C] of the tetanus toxin molecule, respectively, while MAbs MAb-G1, G3 and G6 recognized its middle domain, [B]. Enzyme-linked immunosorbent assay showed that the binding affinity of MAb-G3 was 2.9 x 10(10) M-1 and those of the other MAbs were as high as approximately 10(11) M-1. In in vitro neutralization experiments, at sufficient doses all the MAbs as single reagents protected mice completely against the effect of tetanus toxin. However, at lower doses than those sufficient to rescue mice, the kinetic patterns of progress of symptoms with the individual MAbs differed with each other and, except for MAb-G4, were different from that of anti-tetanus human polyclonal antibody. They suppressed the development and/or slowed the rate of progress of symptoms for over 96 h and delayed death of the mice. We propose that the comparison of the minimum survival dose with that of human polyclonal antibody of known international units is a reliable method for estimating the actual protective activity of a MAb. Intravenous (IV) injection of doses of individual MAbs or their mixtures at over 0.03 IU per mouse protected mice from subsequent challenge with 20 MLD of tetanus toxin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

A missense mutation (Asp250----Asn) in exon 6 of the human lipoprotein lipase gene causes chylomicronemia in patients of different ancestries.

We have previously reported two common lipoprotein lipase (LPL) gene mutations underlying LPL deficiency in the majority of 37 French Canadians (Monsalve et al., 1990. J. Clin. Invest. 86: 728-734; Ma et al., 1991. N. Engl. J. Med. 324: 1761-1766). By examining the 10 coding exons of the LPL gene in another French Canadian patient, we have identified a third missense mutation that is found in two of the three remaining patients for whom mutations are undefined. This is a G to A transition in exon 6 that results in a substitution of asparagine for aspartic acid at residue 250. Using in vitro site-directed mutagenesis, we have confirmed that this mutation causes a catalytically defective LPL protein. In addition, the Asp250----Asn mutation was also found on the same haplotype in an LPL-deficient patient of Dutch ancestry, suggesting a common origin. This mutation alters a TaqI restriction site in exon 6 and will allow for rapid screening in patients with LPL deficiency.

Amino Acid Sequence↗
PubMed1992

Concentration-dependent regulation of neuronal gene expression by nerve growth factor.

NGF is a neurotrophic protein that promotes the survival, growth, and differentiation of developing sympathetic neurons. To directly determine the effects of different concentrations of NGF on neuronal gene expression, we examined mRNAs encoding the p75 low-affinity NGF (LNGF) receptor, T alpha 1 alpha-tubulin (T alpha 1), and tyrosine hydroxylase (TH) in pure cultures of rat sympathetic neurons from postnatal day 1 superior cervical ganglia. Studies of the timecourse of gene expression during 2 wk in culture indicated that a 5-d incubation period would be optimal for the concentration-effect studies. Analysis of RNA isolated from neurons cultured in 2-200 ng/ml 2.5S NGF for 5 d revealed that, as the NGF concentration increased, neurons expressed correspondingly increased levels of all three mRNAs. Both LNGF receptor and TH mRNAs increased seven-fold, and T alpha 1 mRNA increased four-fold in neurons cultured in 200 versus 10 ng/ml NGF. In contrast, T26 alpha-tubulin mRNA, which is constitutively expressed, did not alter as a function of NGF concentration. When neurons were initially cultured in 10 ng/ml NGF for 5 d, and then 200 ng/ml NGF was added, LNGF receptor, T alpha 1, and TH mRNAs all increased within 48 h. The timecourse of induction differed: T alpha 1 mRNA was maximal by 5 h, whereas LNGF receptor and TH mRNAs first began to increase at 12 h after the NGF increase. These experiments show that NGF regulates expression of a subset of mRNAs important to neuronal growth and differentiation over a broad concentration range, suggesting that the effects of NGF may be mediated by more than just a single receptor operating at one fixed affinity. These results also suggest a mechanism for coupling neuronal synthesis of axonal proteins to increases in size of the innervated target territory during growth of the organism.

Animals↗
PubMed1992

Demonstration of a B-lymphocyte mitogen produced by the Lyme disease pathogen, Borrelia burgdorferi.

Lyme disease refers to the multisymptomatic illness in humans which results from infection with the tick-borne spirochete Borrelia burgdorferi. The white-footed mouse is the major reservoir for B. burgdorferi and, upon infection, certain inbred mice develop symptoms similar to those reported in human disease. Sonicated preparations of washed spirochetes were found to have potent mitogenic activity when cultured with lymphocytes from naive C57BL/6, C3H/HeJ, or BALB/c mice. The activity of the B. burgdorferi sonicate was approximately fourfold greater than that of a similarly prepared Escherichia coli sonicate. Polymyxin B efficiently inhibited the mitogenic activity of the E. coli sonicate but only slightly inhibited that of the B. burgdorferi sonicate, suggesting that a lipid A-containing lipopolysaccharide was not responsible for the B. burgdorferi activity. Kinetic analysis indicated peak proliferation at 2 to 3 days of culturing, suggesting polyclonal activation. B- and T-lymphocyte depletion experiments indicated that the major cell type responding to the B. burgdorferi mitogen was the B lymphocyte. This mitogen stimulated murine B cells not only to proliferate but also to differentiate into antibody-secreting cells, as demonstrated by the production of immunoglobulin by stimulated splenocytes. Furthermore, the sonicated preparation stimulated the B-cell tumor line CH12.LX to secrete immunoglobulin in the absence of accessory cells. B. burgdorferi also stimulated interleukin-6 production in splenocyte cultures. The observation that B. burgdorferi can stimulate activation of and immunoglobulin production by normal B lymphocytes may directly reflect on the development of arthritis associated with persistent infection by this organism.

Animals↗
PubMed1992

Evidence for B-lymphocyte mitogen activity in Borrelia burgdorferi-infected mice.

Borrelia burgdorferi produces a mitogen for murine B lymphocytes which can be measured in vitro by polyclonal stimulation of proliferation and immunoglobulin production (R. Schoenfeld, B. Araneo, Y. Ma, L. Yang, and J. J. Weis, Infect. Immun. 60:455-464, 1992). Sonicated B. burgdorferi cells also stimulated IL-6 production by splenocyte cultures. We have used the murine model for Lyme disease described by Barthold et al. (S. W. Barthold, D. S. Beck, G. M. Hansen, G. A. Terwilliger, and K. D. Moody, J. Infect. Dis. 162:133-138, 1990) to determine whether the B. burgdorferi B-cell mitogen is expressed during active infection. To correlate arthritic changes with immune events, we have studied two strains of mice injected with B. burgdorferi; one of them, C3H/HeJ, developed severe disease, and the other, BALB/c, developed only mild disease. C3H/HeJ mice displayed a persistent 10-fold increase in circulating immunoglobulin G (IgG) levels, a 2-fold increase in IgM levels, and a 15-fold increase in peripheral lymph node B-cell numbers, providing evidence of mitogenic activity. Infected BALB/c mice also had evidence for mitogen activity, since the IgG level in serum increased three- to fourfold. The bulk of the increase in circulating IgG levels was not directed against B. burgdorferi antigens, supporting the occurrence of polyclonal B-cell activation. Analysis of IgG isotypes pointed out a contrast between C3H/HeJ and BALB/c mice in that levels of all isotypes were elevated somewhat in both strains of infected mice but IgG2a levels were much more dramatically increased in the C3H/HeJ mice (28-fold) than in the BALB/c mice (4-fold). In this study, interleukin-6 levels were found to be persistently elevated in the serum of infected C3H/HeJ mice. Interestingly, interleukin-6 levels in serum were much lower in the infected BALB/c mice. These findings indicate that the B. burgdorferi mitogen is active in infected animals and may contribute to the inflammatory and immune response to infection.

Animals↗
PubMed1992

[Observation on the effectiveness of repellent coating against mosquitoes].

The present paper reports on the effectiveness of a repellent coating for the first time. The repellent coating was made by combining DETA (N,N-diethyl-meta-toluamide) with slow-releasing reagent. With this coating employed in the laboratory against Aedes aegypti, the rate of blood-sucking was 3.9-9.5% and the rate of protection was 88.9-95.3% for 1-720 days. During 1-77 days' field trial, the RPI (Relative Population Index) was 0-8.98% in the day-time and 0.74-17.15 during the night-time against Anopheles sinensis, Culex pipiens pallens and Culex tritaeniorhynchus. It is concluded that the repellent coating is effective against mosquitoes, safe and prolongs the protection time following exposure to mosquitoes.

Aedes↗
PubMed1992

[Balloon pulmonary valvuloplasty after initial pulmonary valvotomy for pulmonary atresia with intact ventricular septum].

Seven patients with pulmonary atresia and intact ventricular septum have undergone closed pulmonary valvotomy on the early neonatal period (2-6 days) with satisfactory results. Follow-up catheterization showed significant residual pulmonary valve stenosis requiring a second operation. Percutaneous balloon dilatation of the pulmonary valve was successful in 6 cases with the mean right ventricular systolic pressure reduced from 6.8 to 4.9 kPa (50.8 to 37 mmHg) and the mean transvalvular gradient dropped from 5.7 to 2.1 kPa (4.28 to 15.8 mmHg). One case failed and required surgical treatment. The results showed that balloon valvuloplasty could be applied instead of surgery for treatment of selected cases of pulmonary atresia with intact ventricular septum after an initial pulmonary valvotomy.

Catheterization↗
PubMed1991

A mutation in the human lipoprotein lipase gene as the most common cause of familial chylomicronemia in French Canadians.

BACKGROUND: Lipoprotein lipase hydrolyzes the triglyceride core of chylomicrons and very-low-density lipoproteins and has a crucial role in regulating plasma lipoprotein levels. Deficiencies of lipoprotein lipase activity lead to aberrations in lipoprotein levels. Worldwide, the frequency of lipoprotein lipase deficiency is highest among French Canadians. We sought to determine the molecular basis of the disorder in this population. METHODS: The entire coding sequence of the lipoprotein lipase gene from one French Canadian patient was amplified by the polymerase chain reaction and sequenced. Exon 5 from 36 other French Canadian patients was amplified and analyzed by dot blot hybridization with allele-specific oligonucleotides. RESULTS: Sequence analysis revealed a missense substitution of leucine (CTG) for proline (CCG) at residue 207 in exon 5. This mutation was found on 54 of the 74 mutant alleles (73 percent) in the patients. Studies of site-directed in vitro mutagenesis have confirmed that this mutation generates inactive lipoprotein lipase and is the cause of lipoprotein lipase deficiency. CONCLUSIONS: We have identified a missense mutation at residue 207 of the lipoprotein lipase gene that is the most common cause of lipoprotein lipase deficiency in French Canadians. This mutation can be easily detected by dot blot analysis, providing opportunity for definitive DNA diagnosis of the disorder and identification of heterozygous carriers.

Base Sequence↗
PubMed1991

The effects of streptozotocin induced diabetes mellitus and fish oil compound on gene expression of atrial natriuretic peptide in rat.

1. Adult male Wistar rats were injected with streptozotocin (STZ: 55 mg/kg) for inducing diabetes. Then blood and atria for RNA extraction were withdrawn from rats treated 3 and 11 weeks previously with STZ respectively. Atrial total RNA were extracted with cold phenol method. The ANP mRNA contents were determined using Dot blot hybridization technique with alpha-32-P-labelled r-prepro ANP cDNA probe. 2. Plasma glucose was increased and plasma immunoreactive insulin was lowered in rats at 3 and 11 weeks after injection of STZ. ANP gene expression in diabetic rats was depressed. ANP mRNA contents in rats treated 3 and 11 weeks with STZ were 86.4% and 31.7% of that of control rats. 3. Three weeks after treatment of STZ, the rats were gastrically perfused with FOC (Fish Oil Compound) (0.355 ml/kg) once a day successively until 11 weeks. This treatment induces lower blood pressure in rats. ANP gene expression in FOC group was apparently recovered which had been decreased because of the effect of diabetes mellitus.

Animals↗
PubMed1991

Intracellular localization of Borrelia burgdorferi within human endothelial cells.

The later stages of infection by the Lyme disease pathogen, Borrelia burgdorferi, are characterized by the persistence of the organism in individuals possessing a strong anti-Borrelia immune response. This suggests that the organism is sequestered in a tissue protected from the immune system of the host or there is a reservoir of the organism residing within the cells of the host. In this report, the ability of B. burgdorferi to gain entrance into human umbilical vein endothelial cells was explored as a model for invasion. Incubation of B. burgdorferi with human umbilical vein endothelial cells at ratios ranging from 200:1 to 5,000:1 resulted in the intracellular localization of 10 to 25% of B. burgdorferi in 24 h. The intracellular location of the spirochetes was demonstrated by the incorporation of radiolabeled B. burgdorferi into a trypsin-resistant compartment and was confirmed by double-immunofluorescence staining which differentiated intracellular from extracellular organisms. Actin-containing microfilaments were required for the intracellular localization, indicating that the host cell participates in the internalization process. Activation of endothelial cells by agents known to increase the expression of several adhesion molecules had no effect on the interaction of B. burgdorferi with the endothelial monolayer. This indicates that the endothelial receptor for B. burgdorferi is constitutively expressed and that internalization is not dependent upon adhesion molecules whose expression is induced by inflammatory mediators. The demonstration of B. burgdorferi within endothelial cells suggest that intracellular localization may be a potential mechanism by which the organism escapes from the immune response of the host and may contribute to persistence of the organism during the later stages of Lyme disease.

Animals↗