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Biomedical subjects

G Yang

Publications and source records attributed to G Yang.

At least 451 records · Page 25Linked to original sources
PubMed1992

Identification of an essential region for growth signal transduction in the cytoplasmic domain of the human interleukin-4 receptor.

Interleukin-4 (IL-4) is a pleiotropic lymphokine which plays an important role in the immune system by regulating proliferation and differentiation of a wide variety of lymphoid and myeloid cells. These biological effects are manifested via binding of IL-4 to specific membrane-associated high affinity receptors. While the IL-4 receptor (IL-4R) cDNA expresses high affinity binding sites when transfected in COS7 cells, its intracellular domain lacks consensus motifs for known signal transducing molecules such as a tyrosine kinase. In this study, we use a DNA deletion approach to explore the mechanism of signal transduction utilized by the human IL-4R cDNA expressed in a murine pro-B cell line, Ba/F3 cells. Using this system, we have identified the critical region of the cytoplasmic domain of human IL-4R for human IL-4-induced transduction of a growth signal in these cells. Our data indicate that the critical region for signal transduction is located between amino acid residues 433-473 numbering from the carboxyl terminus. This region is highly conserved between mouse and human IL-4R but lacks homology with other cytokine receptors. Our studies additionally demonstrate that the cytoplasmic domain is not essential for forming high affinity IL-4-binding sites nor for ligand internalization.

Amino Acid Sequence↗
PubMed1992

Nonintegrin laminin receptors in the nervous system: evidence for lack of a relationship to P40.

Laminins are extracellular matrix proteins that mediate their effects on cells through integrin and nonintegrin receptors. Two receptors of 67 and 110 kD that bind laminin with a high affinity (Kd approximately nM) have been reported in neural cells. Here, we discuss these and other nonintegrin laminin receptors that have been implicated in neural function. In addition, we report studies characterizing a 43 kD protein, (P40), immunologically related to the 67 kD laminin receptor, which may be involved in retinal development. In our studies, polyclonal antisera (anti-P-20-A) to a synthetic peptide derived from the sequence of a cDNA for a putative high-affinity laminin receptor (67 kD) detected a protein of 43 kD in immunoblots of adult rat retinas. Immunohistochemistry with this antiserum showed that the retinal immunoreactivity was predominantly localized in the ganglion cell layer of both adult chicken and rat retinas where it appeared to be intracellular. Retinal ganglion cells were shown to be immunoreactive by retrogradely labeling them from the superior colliculus with a lipophilic dye and subsequently with anti-P-20-A antisera. Consistent with the preferential localization of the P-20-A immunoreactivity in ganglion cells, there was a substantial decrease in the amounts of P40 on Western blots following optic nerve section and resulting retinal ganglion cell death. Screening of a rat (PC12 cell) cDNA library with the anti-P-20-A antiserum further confirmed the specificity of the antiserum for the rat homologue of P40. Rat P40 is 97% identical to the mouse and 87% identical to human P40 at the nucleic acid level and 98% at the protein level. Restriction mapping of the rather abundant positive clones in the library that cross-hybridized with a human cDNA probe for P40 indicated that the full-length cDNA of 1.2 kb was the major and perhaps the only cDNA in the library. In Northern blots of adult rat retina, these clones hybridized to a single 1.2-kb transcript. Electroblots of retinal homogenates probed with radioiodinated laminin demonstrated binding to a broad band at 110 kD, but none at 43 kD. Taken together these findings suggest that P40 may not be a laminin receptor and are in keeping with the hydrophilic composition of the protein, its intracellular localization, as well as other features predicted by its nucleic acid sequence.(ABSTRACT TRUNCATED AT 400 WORDS)

Amino Acid Sequence↗
PubMed1992

Corneal cell-matrix interactions: type VI collagen promotes adhesion and spreading of corneal fibroblasts.

Type VI collagen is a nonfibrillar collagen present as a network throughout the chick secondary stroma. Immunolocalization of type VI collagen both in the chick corneal stroma and in other systems demonstrates that type VI collagen is present associated with cells and between striated fibrils. We hypothesize that type VI collagen may function in cell-matrix interactions important in corneal development. To examine this possibility, we have isolated and characterized bovine corneal type VI collagen and determined that the chain composition and morphology of type VI collagen isolated from cornea is similar to that isolated from other sources. The tissue form of type VI collagen was localized to filaments forming a network around fibrils and close to corneal fibroblasts. We then analyzed relative attachment and spreading on type VI collagen as compared to the other collagens present in the secondary stroma, and found that although corneal fibroblasts attach equally well to type VI and type I collagen, cells spread to a much greater extent on type VI collagen. Although corneal fibroblasts do have an RGD-dependent receptor which functions during adhesion to fibronectin, attachment to type VI collagen is RGD-independent unless the molecule is denatured. Blocking of the RGD-dependent receptor with soluble RGD peptides results in no change in attachment or spreading. These data imply a role for type VI collagen in cell-matrix interactions during corneal stroma development.

Amino Acid Sequence↗
PubMed1992

The influence of spatial polarization distribution on spot poled PVDF membrane hydrophone performance.

The influence of spatial polarization distribution on spot poled PVDF membrane hydrophone performance was calculated and then experimentally verified using a one-dimensional model based on acoustic wave propagation through a layered medium. It is shown that the sensitivity of the hydrophone is markedly dependent on the spatial polarization distribution. It is also shown that there can be a significant difference between the voltage sensitivities measured in the same hydrophone probe depending on which electrode is actually facing the acoustic source. The measurements carried out in the frequency range 1-20 MHz indicate that this difference, while negligible below 2 MHz, may exceed 1.6 dB at higher frequencies. The model developed can also be used to determine the "effective" piezoelectric constant d33 of the PVDF material as a continuous function of frequency. Moreover, the model predicts the existence of a negative slope in the frequency response of the spot poled membrane hydrophone. The experimental confirmation of this prediction underscores the importance of using swept frequency methods during calibration measurements.

Electricity↗
PubMed1992

Free radical yields from the homolysis of peroxynitrous acid.

A recent study reports discordant results for maximal free-radical yields from the decomposition of peroxynitrous acid using different assay reagents and a puzzling decrease (to zero) of the radical yields with increasing pH. An assay method using 2,2,'azino-bis(3-ethyl-benzthiazoline sulphonate) (ABTS) has been tested using stopped-flow kinetic studies, and the results imply that the assay is satisfactory when [HOONO] much greater than [-OONO] but that reactions involving peroxynitrite anion interfere at higher pH. Evidence is presented that peroxynitrite was an interfering species in the earlier studies.

Benzothiazoles↗
PubMed1992

Mutagenesis of the Glu-89 residue in human immunodeficiency virus type 1 (HIV-1) and HIV-2 reverse transcriptases: effects on nucleoside analog resistance.

A Glu-89-->Gly alteration in the human immunodeficiency virus type 1 reverse transcriptase (RT) was previously shown to result in resistance to several dideoxynucleoside analogs and to phosphonoformic acid (PFA; foscarnet). This residue was altered to Ala, Val, Ser, Thr, Gln, Asp, Asn, or Lys, and the ddGTP and PFA sensitivities of the mutant RTs were measured. Replacements with Ala, Gly, Val, and Thr led to resistance to inhibition by ddGTP, while mutants with amino acid Ser, Gln, Asn, Asp, or Lys displayed only moderate or no resistance. A similar result was obtained with inhibition by PFA, except that the Asp-89 mutant also displayed resistance. Furthermore, the introduction of Glu-89-->Gly alteration into the RT of human immunodeficiency virus type 2 likewise rendered it resistant to both ddGTP and PFA.

Amino Acid Sequence↗
PubMed1992

Microcarrier culture of fish cells and viruses in cell culture bioreactor.

This article deals with the culture of grass carp (Ctenopharyngodon idellus) lip and embryo cells on Cytodex 3 and GT-2 microcarriers in a 1.5-L cell culture bioreactor to propagate grass carp hemorrhage virus. The cells and viruses were successfully cultivated at 26 degrees C, pH 7.0, and dissolved oxygen 40% of air saturation. The cell density achieved was as high as 7.4 x 10(6) cells/mL, and the virus titre reached 6.75 log LD50/0.5 mL from an initial 3.00 log LD50/0.5 mL. The results present broad prospects for fish virus vaccine production.

Animals↗
PubMed1992

Studies on avian spinal cord chimeras. I. Neurological and histological manifestations.

Spinal cord chimeras were produced by replacing a small fragment of neural tube of a 2-day-old White Leghorn chicken embryo with a similar fragment from a Japanese quail embryo. The embryo mortality was 61%, and 72% of hatched birds were 'cripples' and had to be sacrificed within 5 days after hatching. Forty-nine chimeras, 10.9% of the total number of operated embryos, were alive for more than 3 weeks. For at least 17 days after hatching, all birds behaved like normal chicks, and the grey quail-like feathers were the only manifestations of their chimerism. Initial neurological symptoms of unsteady walking and drooping of the wings were noted in all birds except for 1 that died an accidental death before it became sick. Advanced symptoms characterized by paralysis of the legs forcing the bird to lie on its side were noted in 40 birds. The chimeras could be divided into two groups, each consisting of 24 birds. The short-survival (SS) chimeras of the first group became terminally ill and had to be sacrificed within 3 months. The long-survival (LS) chimeras of the second group showed more protracted disease, in that only 16 of them showed symptoms of the advanced disease, and the majority showed partial or complete recovery. Ten of the LS birds were kept alive for more than 8 months. Furthermore, many LS chimeras lost their grey feathers. The hallmarks of neurohistological manifestations were mononuclear cell infiltrates, demyelinization with preservation of axons and scar formation. These lesions were restricted to the quail fragment of the spinal cord except for 2 birds in which distant cellular infiltrates were observed. Direct immunofluorescence tests for chicken IgG were positive in spinal cords of most SS chimeras but only of some LS chimeras.

Animals↗
PubMed1992

Studies on avian spinal cord chimeras. II. Immune response of the chicken host to the graft of quail tissue.

A previous study described clinical and pathological manifestations observed in 49 chimeras produced by replacing a small fragment of the neural tube of a chicken embryo by a similar fragment from a Japanese quail embryo. Predominant antibodies in sera of these birds were directed against xenogeneic antigens which are devoid of organ specificity and which are present in quail tissues but absent from chicken tissues. Mixed agglutination test with quail cell monolayers detected such antibodies in sera of all chimeras tested. In most instances, positive reactions were observed already in the 4th week after hatching; they persisted in all birds throughout the observation period of up to 8 months. Some of the detected antibodies were directed against saline-nonextractable surface antigens of quail cells. Enzyme immunoassay with quail organ extracts, agglutination of quail tissue particles, and indirect immunofluorescence test with quail organ sections were positive with sera of many, but not all, chimeras. CNS-specific antibodies, apparently autoantibodies, were detected in serum samples of only one chimera, using enzyme immunoassay with extract of chicken brain and indirect immunofluorescence test with sections of chicken spinal cord. Eluates from lesional spinal cord contained antibodies to non-organ-specific quail antigens but not to CNS-specific antigens. Cerebrospinal fluids of many chimeras had antibodies to quail antigens, but no evidence for antibody formation within the CNS was obtained. Cell-mediated immunity could be demonstrated in all chimeras tested by means of lymphocyte proliferation test after stimulation by quail organ extract. It was concluded that pathological events in the studied chimeras have been most likely mediated primarily by humoral immune responses to non-organ-specific quail antigens.

Animals↗
PubMed1992

[Selection of DSP points in second stage and their presentation].

The principal of selecting DSP points is discussed. Because social and economic development is not balance, developing level of health business and health situation of population are obvious varies in different areas of China. In order to ensure that health information from surveillance population can be used to infer health situation of national population, the feature of geographic, administrative areas and various health situation in different areas are considered. The principals of selecting DSP are: 1. To assure well-balance of geographic distribution of DSP. 2. To assure well-balance of distribution of DSP in different kind of areas, according to above 9 index, GNP, illiterate rate, birth rate, infant death rate, rough death rate, ratio of 0-14 years people to total people, ratio of about 65 years people to total people, ratio of labor in industry to total people, and ratio of labor in agriculture to total people. The way of select DSP is: Multistage stratified random sampling (PPS). Meanwhile in order to avoid systematic error, about 15% points which are no qualified were changed. Therefore whether data from DSP can be represented health level of population of whole nation has been tested. The conclusion is that the data from DSP can indeed do so.

Birth Rate↗
PubMed1992

[Biochemical and immunological characterization of desmosomal proteins].

Desmosmoes were dissolved by incubation at 100 degrees C for 30 minutes in lysis buffer containing 9.5 M urea. SDS-PAGE revealed seven high molecular weight (> 67 kd) bands and some keratins. Seven of these were considered to be major bands. Bands 1 and 2 with M(r) values of 250 kd and 215 kd, called desmoplakins I and II. Polypeptide bands 3, 4a 4b, 5 and 6 had M(r) values of 165kd, 130kd, 115kd, 83kd and 75kd, respectively. 2-2.5mg of Desmoplakin I was obtained by a preparative electrophoresis; the purity reached 93.1%. The isoelectric pH range was between 6.8 and 7.2, and the amino acid compositions displayed a relatively high content of glycine. It was found that McAb Desmoplakin I recognized specifically the 250kd antigenic band by immunoblotting.

Amino Acids↗
PubMed1992

[Restriction fragment length polymorphisms of chloroplast DNA and the intergenic spacer of rRNA gene in cultivated barley of China].

A sample of 80 accessions collected from several major barley growing areas in China was assayed for restriction fragment length polymorphisms at two regions of the chloroplast DNA and the intergenic spacer of the ribosomal RNA gene (rDNA). The results showed that the spacer length was highly polymorphic and 8 spacer length variants constituting 8 phenotypes were observed in this sample. It is also clear that the spacer length variants and the phenotypes were differentially distributed in different geographical regions, probably due to adaptation of the genotypes to the local environments. We did not detect variation in the two chloroplast fragments, indicating that the variability of chloroplast DNA is low in cultivated barley.

Chloroplasts↗
PubMed1992

[Cause analysis of measles incidence in National Diseases Surveillance System in 1990].

This paper described the time and areas distribution of 875 measles cases in DSP in 1990 and discussed relationship between vaccination and measles cases. Through studying cases in several points with high morbidity, the authors found that there was no high immunization coverage. It must have been the first chance of measles incidence. Further more the immunization technics and cold chain were found unqualified, which were thought to be the second chance.

Age Factors↗
PubMed1992

Anesthesia crisis resource management training: teaching anesthesiologists to handle critical incidents.

The authors have developed a course in Anesthesia Crisis Resource Management (ACRM) analogous to courses in Crew (Cock-pit) Resource Management (CRM) conducted in commercial and military aviation. Anesthesiologists do not typically receive formal training in crisis management although they are called upon to manage life-threatening crises at a moment's notice. Two model demonstration courses in ACRM were conducted using a realistic anesthesia simulation system to test the feasibility and acceptance of this kind of training. Anesthesiologists received didactic instruction in dynamic decision-making, human performance issues in anesthesia, and in the principles of anesthesia crisis resource management. After familiarization with the host institution's operating rooms and with the simulation environment, they underwent a 2-h simulation session followed by a debriefing session which used a videotape of their simulator performance. Participants rated the course as intense, helpful to their practice of anesthesiology, and highly enjoyable. Several aspects of the course were highly rated, including: videotapes of actual anesthetic mishaps, simulation sessions, and debriefing sessions. Scores on written tests of knowledge about anesthesia crisis management showed a significant improvement following the first course (residents) but not the second course (experienced anesthesiologists). Although the ultimate utility of this training for anesthesiologists cannot easily be determined, the course appeared to be a useful method for addressing important issues of anesthesiologist performance which have previously been dealt with haphazardly. The authors believe that ACRM training should become a regular part of the initial and continuing education of anesthesiologists.

Anesthesiology↗
PubMed1992

[Environmental and inheritive factors on large bowel cancer].

In order to clarify the influence of inherit and environmental factors on the large bowel cancer, a population-based case-control study involving 850 cases and 857 controls matched by age and sex, and a entailed family cancer history survey were carried out from September 1988 through August 1989. Multivariate analysis showed that less intake of crude fibre increased risk of the cancer whereas vegetables was negatively associated after controlling for some possible confounding factors. The intake of fat, protein and meat slightly raised the risk of the cancer. Univariate analysis showed that the history of large bowel cancer in first degree relatives had a remarkable risk (RR = 2.2, P less than 0.05), but adjusting environmental factors (especially dietary factors, e. g. fat, protein, crude fibre, calories ect.) the history had no close relationship with the cancer. The heritability of large bowel cancer was 16.78 +/- 6.20%.

China↗