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M Yang

Publications and source records attributed to M Yang.

At least 433 records · Page 24Linked to original sources
PubMed1994

Clinically relevant concentrations of bupivacaine inhibit rat aortic baroreceptors.

Bupivacaine is clinically associated with cardiovascular toxicity. To examine the possible role of drug actions at arterial baroreceptors, we studied discharge properties of baroreceptors in an in vitro aortic nerve-aortic arch preparation from rats. We measured single fiber discharge, pressure, and aortic diameter simultaneously during perfusion of the aortic arch with bupivacaine. Perfusion mean arterial pressure was held at 80 mm Hg. Only regularly discharging, presumably myelinated, baroreceptors were studied. To assess pressure threshold, threshold frequency, and maximum discharge rate, nerve activity was evoked by slow ramps of increasing pressure (< 2 mm Hg/s) beginning at 20 mm Hg and ranging up to 150-170 mm Hg. Following replicate control measurements, test ramps were repeated in the presence of sodium nitroprusside (1 microM) and phentolamine (1 microM) to eliminate potential smooth muscle and alpha 1-adrenoceptor effects, respectively. Bupivacaine was then added to the perfusate in increasing concentrations from 0.1 to 50 microM for 15 min to construct a full concentration-response curve at each level. Individual baroreceptors showed substantial depression of maximum discharge frequency and/or increases in pressure threshold at 1-5 microM bupivacaine. In overall population averages (n = 7), 5-10 microM bupivacaine clearly reduced maximum discharge and shifted the pressure threshold to higher values (P < 0.01). The net result was a general depression of discharge. Concentrations as low as 10 microM bupivacaine completely blocked discharge in some baroreceptors. Inasmuch as the pressure-diameter relations were not changed, discharge relations plotted against diameter showed equivalent changes. Bupivacaine-free solution reversed the block in all cases.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Immunoreactivity of apolipoprotein B-100 in oxidatively modified low density lipoprotein.

Thirteen monoclonal antibodies (MAbs) against apolipoprotein B-100 (apo B) were used to analyze changes in immunoreactivity of human LDL resulting from oxidation mediated by cupric ions and oxygen. Decrease in immunoreactivity of oxidized LDL was demonstrated by competitive ELISA with MAbs 5F8, BL3, Mb43, 2G8, B3, B5, and BL7 for which the epitopes are located within residues 1-1297, 4235-4355, 4027-4081, 3728-4306, 2239-2331, 1854-1878, and in the vicinity of residue 2331, respectively. Immunoreactivity of the epitope B6 (2239-2331) increased during first 4 hours of oxidation and then diminished gradually. Epitope B1 (405-539) had slightly reduced immunoreactivity during first 8 h of LDL oxidation and then its minor increase was observed. MAb 12G10, specific to the epitope within apo B thrombin-digest fragment T4 (1-1297), displayed either weak or strong binding to LDL. LDL with weak binding pattern demonstrated significant increase in immunoreactivity upon oxidation. In contrast, LDL with strong binding pattern showed little to no change. Epitopes Mb47 (3441-3569) and 8G4 (1-1297) remained unchanged in oxidized LDL. Immunoreactivity of apo B-100 epitope recognized by MAb 4C11 (residues 2377-2658) was shown to be a function of oxidation time: it increased progressively up to 16 h and was stabilized for another 24 h of LDL oxidation. This epitope may be unmasked by LDL oxidation and may provide a useful immunochemical marker to monitor the extent of LDL oxidation.

Antibodies, Monoclonal↗
PubMed1994

Molecular basis of cross-reactivity among allergen-specific human T cells: T-cell receptor V alpha gene usage and epitope structure.

Cross-reactivities between the major grass pollen allergens, at the level of T-cell recognition was examined employing several Lolium perenne I (Lol p I)-specific human T-cell clones. Nine of these Lol p I-specific T-cell clones exhibited cross-recognition of the recombinant Poa pratensis IX (Poa p IX) allergen, rKBG7.2, indicating that these two major antigens of a grass pollen share T-cell epitopes. Furthermore, proliferative responses of two other T-cell clones demonstrated that individual allergens of diverse grass pollens also possess common T-cell epitopes. Examination of the T-cell receptor (TcR) V alpha genes of these T-cell clones indicated that these cloned cells utilized distinct J alpha genes and that nine out of 10 clones possessed V alpha 13 gene. Furthermore, sequence comparisons of several allergenic molecules indicated that this cross-reactivity may be due to the presence of epitope(s) with structure(s) similar to the major T-cell epitope of Poa p IX allergens. Taken together, these results suggest for the first time that the major grass pollen allergens share cross-reacting T-cell epitope(s), and that this cross-reactivity is due to the structural homologies among allergens and restricted usage of TcR V alpha genes.

Allergens↗
PubMed1994

[Multiple analysis of the factors influencing the result of tilt table test].

Ninety two patients with unexplained syncope and 52 normal controls without history of syncope were divided into three groups respectively. Baseline tilt table test (BTTT), multistage isoproterenol tilt table test (MITTT), and single stage isoproterenol tilt table test (SITTT) were performed in all of them. Logistics regression was used with the result of TTT as independent variable; dependent variables included sex, age, basal heart rate, basal blood pressure, the index of syncope (i) and the difference between basal heart rate and the rate before tilting (h12). The results were as follows: (1) According to the regression for the total population tested, the main factors influencing the result of TTT were i and h12 (P = 0.012 and P = 0.001). Similar result was found in the patient group (P = 0.052 and P = 0.032). (2) In the control group, sex and h12 were the predictors of the result (P = 0.090 and P = 0.016). It is concluded that: (1) The result of TTT is mainly affected by the frequency and degree of syncope, as well as by the use of isoproterenol; (2) Isoproterenol increases the sensitivity of TTT, but decreases the specificity; (3) Sex is probably an important factor affecting the result of TTT.

Adolescent↗
PubMed1994

[The study of mechanisms and effects of prophylaxis and cure of electroacupuncture against ischemia injury in brain].

In order to observe the influence of electroacupuncturing (EA) "Ren Zhong" point on acute ischemia injury in brain, an experimental model of acute ischemia injury in brain was produced by antidromically blocking double common carotid arteries in 18 rabbits. The basic arteries' pressure will be increased by EA, RA and the contents of AI, A II increased and the content of LA reduced obviously in brain. An experimental evidence was given for the safety of EA anesthesia and the curative effect of EA on ischemia in brain.

Angiotensin II↗
PubMed1993

Pedigree analysis of alpha-L-fucosidase gene mutations in a fucosidosis family.

Fucosidosis is an autosomal recessive lysosomal storage disease resulting from absence of alpha-L-fucosidase activity. Lymphoid cell lines from two siblings with fucosidosis and a healthy individual (control) had alpha-L-fucosidase mRNA of normal size (2.3 kb) but the level of alpha-L-fucosidase mRNA in the patients' cells was reduced. cDNA was prepared and amplified from alpha-L-fucosidase mRNA of lymphoid cells of the patients, their carrier parents, and the control. Direct DNA sequencing demonstrated three mutations in the fucosidosis family. One mutation, C1282-->T, changed the codon (CAA) for Gln-422 to a stop codon (UAA). This mutation was heterozygous (C and T) in the patients and their father and independently confirms an earlier report (J. Mol. Neurosci. (1989) 1, 177). Another mutation, C247-->T, changed the codon (CAG) for Gln-77 to a stop codon (UAG) and was heterozygous (C and T) in the patients and their mother. The third mutation, A860-->G, changed the codon CAG for Gln-281 to the codon (CGG) for Arg and was heterozygous (A and G) in the patients but homozygous in their father. alpha-L-Fucosidase activity in cells of the father was 37% of controls indicating that homozygosity of the A860-->G mutation did not cause an absence of alpha-L-fucosidase activity and fucosidosis. This mutation probably results in a normal polymorphic variant of alpha-L-fucosidase. It is proposed that the combination of the C247-->T mutation on the maternal allele of the alpha-L-fucosidase gene and the C1282-->T mutation on the paternal allele caused fucosidosis in the patients.

B-Lymphocytes↗
PubMed1993

Effect of sulfhydryl reagents on spectrin states on the erythrocyte membrane.

The unique properties of erythrocytes are largely determined by its fibrillar network under the plasma membrane. Spectrin, one major component of the membrane skeleton, has been suggested to play a central role in this process. To understand the mechanism underlying this process, the effect of the sulfhydryl groups of erythrocyte membrane on spectrin structure and function was studied. By using non-denaturing gel analysis, dithiothreitol was found to protect spectrin in its tetramer state. In contrast, iodoacetamide and N-ethylmaleimide enhanced conversion of the spectrin tetramer to dimer and decreased its binding to the membrane. Moreover, when the membrane was treated with cadmium, the tetramer was converted to the dimer on the membrane, while zinc had no effect. Hemolysis experiments showed that cadmium could lyse erythrocytes in vitro. These results indicated that preservation of the spectrin tetramer or even higher oligomer states, by the sulfhydryl groups may be important to the membrane integrity and the intact cell functions.

Cadmium↗
PubMed1993

Primary structure of Beijing duck apolipoprotein A-1.

The primary structure of Beijing duck apolipoprotein A-1 was determined by sequencing peptide fragments derived from tryptic and endoproteinase Asp-N digestion of the protein, and alignment with homologous chicken apo A-1. All of the peptide fragments were isolated by high-pressure liquid chromatography (HPLC) with a Vydac C18 column using a trifluoroacetic acid (TFA) buffer system. The N-terminus of the protein was determined to be aspartic acid by directly sequencing 52 residues of the intact protein. The C-terminus was alanine. The protein contains 240 amino acid residues. By analysis of the whole protein and its tryptic peptides, a six amino acid (Arg-Tyr-Phe-Trp-Gln-His) prosegment was determined. No cross-reactivity between duck and human apo A-1 with a goat antiserum against human apo A-1 was found. Sequence analysis of apo A-1 of other species indicates that amino acid substitutions in rat are more extensive than in other mammals. Isoleucine residues in apo A-1 are inversely correlated to the homology of human to other species, except dog.

Amino Acid Sequence↗
PubMed1993

Construction of multiple copy of alpha-domain gene fragment of human liver metallothionein IA in tandem arrays and its expression in transgenic tobacco plants.

Metallothioneins (MT) are low molecular weight, cysteine-rich, metal-binding proteins. An MT molecule contains two domains which appear to act independently--an alpha-domain, which is characterized by cadmium-binding, and a beta-domain, which binds preferentially to copper. Based on this conception, DNA duplex encoding the alpha-domain (106 bp) of human MT-IA was constructed from a chemically-synthesized oligomer by repair synthesis and enzymatic ligation and cloned into pUC19. The genes cloned were sequenced and found to be in the correct order as designed. Synthetic directional adapters were attached to the terminals of the alpha-domain gene fragment of human MT-IA to establish complete control over fragment orientation during ligation. The use of these directional adapters thereby ensured the production of multiple copies of the alpha-domain in tandem arrays. The successive alpha-domains were linked by a peptide linker consisting of 10 residues. A chimeric gene containing 12 cloned tandemly repeated copies of the 106 bp alpha-domain DNA was introduced into tobacco cells on a disarmed Ti-plasmid of Agrobacterium tumefaciens. A total of 10 different transgenic tobacco plants were generated, of which two showed root and shoot growth unaffected by up to 200 mg/l kanamycin and 100 microM cadmium, whereas root growth of control plants was severely inhibited and leaf chlorosis developed on media containing only 10 microM cadmium.

Agrobacterium tumefaciens↗
PubMed1993

An ionic current model for neurons in the rat medial nucleus tractus solitarii receiving sensory afferent input.

1. Neurons from a horizontal slice of adult rat brainstem were examined using intracellular recording techniques. Investigations were restricted to a region within the nucleus tractus solitarii, medial to the solitary tract and centred on the obex (mNTS). Previous work has shown this restricted area of the NTS to contain the greatest concentration of aortic afferent baroreceptor terminal fields. Electrical stimulation of the tract elicited short-latency excitatory postsynaptic potentials in all neurons. 2. mNTS neurons were spontaneously active with firing frequencies ranging between 1 and 10 Hz, at resting potentials of -65 to -45 mV. These neurons did not exhibit spontaneous bursting activity. 3. Depolarizing current injection immediately evoked a finite, high-frequency spike discharge which rapidly declined to a lower steady-state level (i.e. spike frequency adaptation, SFA). Increasing depolarizations produced a marked increase in the peak instantaneous frequency but a much smaller increase in the steady-state firing level. 4. Conditioning with a hyperpolarizing prepulse resulted in a prolonged delay of up to 600 ms before the first action potential (i.e. delayed excitation, DE) with an attendant decrease in peak discharge rates. DE was modulated by both the magnitude and duration of the prestimulus hyperpolarization, as well as the magnitude of the depolarizing stimulus. Tetrodotoxin (TTX) eliminated spike discharge but had little effect on the ramp-like membrane depolarization characteristic of DE. 5. We have developed a mathematical model for mNTS neurons to facilitate our understanding of the interplay between the underlying ionic currents. It consists of a comprehensive membrane model of the Hodgkin-Huxley type coupled with a fluid compartment model describing cytoplasmic [Ca2+]i homeostasis. 6. The model suggests that (a) SFA is caused by an increase in [Ca2+]i which activates the outward K+ current, IK,Ca, and (b) DE results from the competitive interaction between the injected depolarizing current and the hyperpolarization-activated transient outward K+ currents, IA and ID. 7. We conclude that our ionic current model is capable of providing biophysical explanations for a number of phenomena associated with brainstem neurons, either during spontaneous activity or in response to patterned injections of current. This model is a potentially useful adjunct for on-going research into the central mechanisms involved in the regulation of both blood pressure and ventilation.

Action Potentials↗
PubMed1993

Isolation of a DNA probe for identification of Mycobacterium kansasii, including the genetic subgroup.

In order to develop a DNA-based assay to identify all Mycobacterium kansasii clinical isolates, a specific DNA probe was isolated in plasmid p6123. A total of 145 M. kansasii clinical isolates were collected from several countries and were examined with three probes by DNA hybridization. Of the 145 isolates, 115 (79%) were positive with the previously described probe pMK1-9 (Z. H. Huang, B. C. Ross, and B. Dwyer, J. Clin. Microbiol. 29:2125-2129, 1991), 129 (88%) were positive with the commercial Accu-probe assay (Gen-Probe), and 145 (100%) were positive with the p6123 probe. Southern blot analysis of EcoRI-digested M. kansasii chromosomal DNA with p6123 revealed that all Accu-probe-positive M. kansasii strains exhibited a 3-kb fragment, whereas all Accu-probe-negative M. kansasii strains displayed DNA fragments of variable molecular sizes. These results indicate that, unlike the previously described probes for M. kansasii, the fragment cloned into p6123 identified all 145 biochemically typical strains tested and provides an ideal target for future DNA-based speciation assays.

Base Sequence↗
PubMed1993

Identification of an insertion sequence-like element in a subspecies of Mycobacterium kansasii.

Analysis of a genomic DNA clone library of a strain from the genetic subspecies of Mycobacterium kansasii determined the existence of a repetitive insertion sequence-like element. The element is 947 bp long and is present in a minimum of 1 to 11 copies per genome. Similar to insertion sequences, it contains a 3-bp (TAG) direct repeat at its extremities and a transcription promoter-like sequence. In addition, for one of the clones sequenced, a potential cointegrate formation, a characteristic frequently observed with insertion sequences, was revealed. This insertion sequence does not contain short inverted repeats near the ends or a large open reading frame to code for a transposase enzyme. Its host range is restricted to a previously described genetic subspecies of M. kansasii and is not present in typical M. kansasii or other mycobacterial species. When used as a probe for Southern blot hybridization, significant heterogeneity between different isolates of the M. kansasii subspecies was observed. This repeated element will be useful in further studies on the characterization, diagnosis, and epidemiology of M. kansasii.

Base Sequence↗
PubMed1993

Expression of IGF-II/Man-6-P receptors on rat, rabbit, and human colon epithelial cells.

Previous experiments from this laboratory have established the presence of receptors for insulin and insulin-like growth factor I (IGF-I) on apical membranes prepared from rabbit colon epithelial cells; however, no receptors for multiplication-stimulating activity (MSA), the rat peptide hormone equivalent of human IGF-II, were found in this tissue. In the current studies, radioligand binding assays, covalent cross-linking experiments, and immunoblot analyses using a polyclonal rabbit antiserum that recognizes the IGF-II/mannose 6-phosphate (Man-6-P) receptor, all confirmed the presence of IGF-II/Man-6-P receptors on membranes prepared from rat and human colon epithelial cells. Exposure of rat colon epithelial cell membrane fractions to 5 mM Man-6-P before incubation with 125I-labeled IGF-II increased radioligand binding. Immunoblot analysis indicated that IGF-II/Man-6-P receptors were present in both unfractionated rat colon membranes and fractions enriched with apical membranes. Rabbit and human colon epithelial cells displayed a different pattern of receptor distribution than rat colon epithelial cells, with more insulin receptors but relatively few IGF-II/Man-6-P receptors. Immunohistochemical studies using a rabbit polyclonal antiserum confirmed that IGF-II/Man-6-P receptors were present on both the apical and the basolateral surfaces of colon epithelial cells.

Animals↗
PubMed1993

Cutaneous inflammatory pseudotumor: a case report with immunohistochemical and ultrastructural studies.

An unusual case of inflammatory pseudotumor of the subcutaneous tissue in a 44-yr old black male who presented with a 4 cm soft tissue mass on the dorsum of right hand is described. The mass was sharply circumscribed and composed of a polymorphous infiltrate of plasma cells, eosinophils, lymphocytes and some giant cells mimicking Reed-Sternberg cells. The giant cells, corresponding ultrastructurally to primitive mesenchymal cells, were immunoreactive for vimentin and were negative for actin, desmin and histiocytic markers. The patient remained well with no sign of recurrence 8 mths postoperatively. The present case is compared with the (4) previously reported cases in literature. The histologic differentiation from other neoplastic and non-neoplastic lesions is discussed.

Adult↗
PubMed1993

High field proton NMR investigations of the metabolic profiles of multidrug-sensitive and -resistant leukaemic cell lines: evidence for diminished taurine levels in multidrug-resistant cells.

High field proton (1H) nuclear magnetic resonance (NMR) spectroscopy has for the first time been employed to investigate and compare the metabolic profiles of vinblastine-sensitive and -resistant T-lymphoid leukaemic cell lines (CCRF-CEM and CEM/VLB100 respectively) and evidence is presented for a significantly lower taurine content in the CEM/VLB100 resistant subline when expressed relative to that of its drug-sensitive parental counterpart. These data suggest differences in the nature and relative involvements of taurine biosynthetic pathways between the two cell lines, a phenomenon that may be related to their differing sensitivities towards chemotherapeutic agents such as adriamycin which promote the generation of cytotoxic reactive oxygen species (ROS) in vivo. However, the 1H NMR data obtained provided no evidence for an increased metabolic consumption of hypotaurine (a metabolic precursor of taurine with powerful .OH radical scavenging properties) in CCRF-CEM cells since differences observed in the hypotaurine: taurine concentration ratio between the drug-sensitive and -resistant cell lines were not statistically significant. Furthermore, hypotaurine is unlikely to compete with alternative endogenous .OH radical scavengers present such as lactate since its level in either of the two cell lines investigated (ca. 6.0 x 10(-8) mol./10(8) cells) is insufficient for it to act as an antioxidant in this context. The biochemical and therapeutic significance of these results are discussed.

Antineoplastic Agents↗