Search PubMed⌕ Search

Biomedical subjects

A Wang

Publications and source records attributed to A Wang.

At least 289 records · Page 16Linked to original sources
PubMed1991

[Purification and antimicrobial activity of human neutrophil defensins].

Neutrophils are one of the weapons of host defenses against microbial infection. Their ability to kill the invading microorganisms depends on two principle mechanisms. One depends on production of reactive oxygen intermediates (ROI) by stimulated neutrophils, and the other depends on the delivery of antimicrobial contents of the neutrophils' cytoplasmic granules, oxygen-independent. The defensins have the highest concentration in the neutrophils, and the broadest antimicrobial spectrum, being capable of killing gram-positive and gram-negative bacteria, fungi and some envelope viruses. We purified human defensins from the neutrophils' granules by gel permeation chromatography and SDS-preparative acrylamide gel electrophoresis. The molecular weight of human defensins is between 3,000-4,000 daltons. After testing, C. neoformans was susceptible to these defensins. Under condition of 37 degrees C, pH 7.4 and low ionic strength, antifungal activity by human defensins was related to its concentration and incubating time. All of these illustrate that nonoxidative killing mechanism of neutrophils, especially the function of defensins is very important in host defenses.

Antifungal Agents↗
PubMed1991

Studies on monoclonal antibody against recombinant human granulocyte colony-stimulating factor.

Three hybridoma cell lines producing monoclonal antibodies (McAb) against recombinant human granulocyte colony-stimulating factor (rhG-CSF) have been established by fusing mouse myeloma cell line SP2/0 cells with spleen cells from a BALB/c mouse immunized with rhG-CSF. Ascites was obtained from BALB/c mice by injecting the hybridoma cells intraperitoneally. Three McAbs were purified by the caprylic acid-ammonium sulfate method. For each, the IgG subclass, valence and activity, molecular weight, specificity and affinity were determined. The applications of McAbs against rhG-CSF in the clinic and laboratory are discussed.

Animals↗
PubMed1990

Ordered multisite protein phosphorylation. Analysis of glycogen synthase kinase 3 action using model peptide substrates.

Recognition of substrates by the protein kinase glycogen synthase kinase 3 (GSK-3) usually requires prior phosphorylation of the substrate. Using a peptide based on the glycogen synthase sequence PRPAS(3a)VPPS (3b)PSLS(3c)RHSS(4)PHQS(5)EDEEEP (where the numbers in parentheses denote sites of phosphorylation), we showed previously that phosphorylation of site 5 by casein kinase II was necessary for GSK-3 to phosphorylate the peptide at sites 3a, 3b, 3c, and 4 (Fiol, C. J., Mahrenholz, A. M., Wang, Y., Roeske, R. W., and Roach, P. J. (1987) J. Biol. Chem. 262, 14042-14048). In the present study, variant peptides were synthesized in which sites 3a, 3b, 3c, and 4 were individually replaced by Ala residues (denoted Ala-3c, etc.). All of the variant peptides were substrates for casein kinase II. The peptide Ala-4,Ser(P)-5 was not a substrate for GSK-3 confirming the minimal recognition sequence for the protein kinase as -SXXXS(P)-. The peptides Ala-3c,Ser(P)-5, Ala-3b,Ser(P)-5, and Ala-3a,Ser(P)-5, however, were all good substrates for GSK-3 with apparent Km values in the range 3-6 microns, comparable with that of the parent peptide. GSK-3 could introduce 1, 2, and 3 phosphates, respectively, into these substrates, always COOH-terminal to the substituted Ala residue. Ala-4,Ser(P)-5 and Ala-3c,Ser(P)-4,Ser(P)-5 were competitive inhibitors for phosphorylation of the parent peptide, with Ki values of 2 and 5 microns, respectively. The data suggest (i) that GSK-3 recognizes serines in the motif -SXXXS(P)-, and (ii) that multiple phosphorylation of the peptide substrate has an obligate order, with the sequential formation of new recognition sequences.

Amino Acid Sequence↗
PubMed1990

The effects of vasoactive intestinal polypeptide on cholinergic neurotransmission in an isolated innervated guinea pig tracheal preparation.

To explore the possibility that VIP modulates cholinergic neurotransmission in the airways, we studied the effects of exogenous VIP on contractile responses of an isolated innervated guinea pig tracheal preparation to vagal nerve stimulation (NS), electrical field stimulation (EFS) and exogenous acetylcholine (ACh). VIP (2.5 x 10(-8), 2.5 x 10(-7) M) caused concentration-dependent reductions in responses to NS and EFS. Low frequency stimulations (1 Hz) were significantly more inhibited than higher frequencies (5 and 20 Hz). VIP inhibited NS significantly more than EFS at 1 and 5 but not 20 Hz. In contrast, VIP (2.5 x 10(-7) M) did not significantly reduce responses to ACh (3 x 10(-7), 10(-6), and 3 x 10(-6) M). The neutral endopeptidase inhibitor phosphoramidon (5 x 10(-6) M) enhanced responses of NS to VIP but did not affect responses to NS in the absence of VIP. We conclude that in the isolated guinea pig tracheal preparation, VIP can modulate cholinergic neurotransmission by actions that are predominantly on post-ganglionic nerves but it has also a small additional effect on ganglionic transmission.

Acetylcholine↗
PubMed1990

MRI and diabetic foot infections.

The role of magnetic resonance imaging and plain radiographs in evaluating osteomyelitis in the diabetic foot was studied. Fifty patients were prospectively examined by magnetic resonance imaging and plain radiographs to determine the extent of infection. Thirty-seven patients had positive MRI for osteomyelitis and 19 were positive with conventional radiography. Thirteen patients had negative MRI healed with short course of antibiotics. Five patients with positive MRI received four weeks' course of intravenous antibiotics with two still having persistent infection in the six weeks follow-up. Thirty-two patients underwent surgery with favorable results. Sixty-two bone specimens were obtained for histologic evaluation of osteomyelitis. In cases with histologic proof of diagnosis, magnetic resonance sensitivity was 99%, specificity was 81%, and accuracy was 94%. Thus magnetic resonance imaging was shown to have a high sensitivity, specificity, and accuracy in detecting osteomyelitis.

Adult↗
PubMed1990

The equivalence of anesthetic regimens with respect to plasma glucose elevation during cerebrovascular surgery.

Hyperglycemia, even if mild, is known to aggravate neuronal damage from cerebral ischemia. In order better to define the influence of currently used anesthetic techniques on plasma glucose levels during cerebrovascular surgery, we examined serial plasma glucose values during 43 carotid endarterectomies (CEA) and 19 intracranial arteriovenous malformation (AVM) resections. CEA patients (aged 67.6 +/- 1.4 years and weighing 76.4 +/- 2.3 kg, mean +/- SEM) received N2O in O2 and either isoflurane (ISO) (n = 14), halothane (n = 8), fentanyl (n = 10), or sufentanil (n = 11). Plasma glucose was compared at 1.12 +/- 0.05 h (stage 1), 2.08 +/- 0.07 h (stage 2), and 3.12 +/- 0.1 h (stage 3) after induction of anesthesia. AVM patients received ISO and N2O in O2. Plasma glucose was compared 2.32 +/- 0.14 h (stage 1) and 6.25 +/- 0.34 h (stage 2) after induction of anesthesia (surgical stage). Glucose was determined by the hexokinase method. In the CEA cases, progressively elevated plasma glucose levels were associated with successive surgical stage (114 +/- 6, 122 +/- 6, and 138 +/- 6 mg/dl). The seven CEA patients that carried the diagnosis of diabetes mellitus tended to have higher glucose levels but they did not differ significantly from nondiabetic patients. The AVM patients (aged 35.7 +/- 2.3 years and weighing 71.1 +/- 2.9 kg) were all nondiabetic. They were significantly younger than the CEA patients and each received dexamethasone intraoperatively. In these patients, there was a significant effect (p <0.04) of surgical stage to increase plasma glucose (115 +/- 10 vs. 126 +/- 10 mg/dl). For CEA, the anesthetic techniques examined do not differ significantly in their influence on plasma glucose levels, but all techniques were associated with a gradual increase in plasma glucose levels intraoperatively, even in nondiabetic patients. Compared to the group of younger AVM patients, glucose elevation was more pronounced in the elderly CEA patients. We conclude that intraoperative monitoring of plasma glucose may be useful in elderly patients during prolonged neurovascular procedures.

Journal Article↗
PubMed1990

Hemispherectomy--a radical solution.

1. Hemispherectomy, a procedure where half of the brain is removed, is one of the most radical surgeries performed. One of the few medical conditions to warrant such a procedure is intractable seizures in infantile hemiplegia. 2. Children on whom hemispherectomies are performed present with one or more of the following symptoms: hemiplegia, persistent focal seizures, mental deterioration, and hemianopia. Mental deterioration is usually present to some degree but can be exacerbated by the persistent seizures. 3. Nursing implications include extensive preoperative teaching as to pathology, surgical procedure, and expected outcomes. Postoperative instruction involves training parents to assist their child with passive range of motion exercises or ambulation and the action and side effects of medications.

Brain↗
PubMed1989

Novel method for studying mRNA phenotypes in single or small numbers of cells.

Biological processes, such as growth control, are often governed by biochemical steps involving mRNA transcripts that are short-lived and have a low copy number. Furthermore, the cells involved in these processes are often available in low numbers from in vivo sources. We now report a method that is superior to in situ hybridization, RNA blot analysis, and the nuclease protection assay for the study of short-lived, low-copy-number mRNA transcripts. The method consists of a microprocedure for isolating RNA from one to a few thousand cells and two coupled enzymatic steps: reverse transcription of whole cellular RNA, followed by amplification of the cDNA by a specifically primed polymerase chain reaction to give specific cDNA fragments that can be visualized on agarose gels by ethidium bromide staining. With this method we have detected actin mRNA from a single cell, or less than 100 cRNA molecules, and have quantified differences in RNA concentrations of less than threefold. The reverse transcription reaction products can be divided for the polymerase chain reaction, and several mRNA species can be assayed simultaneously. Therefore, we call the method single-cell mRNA phenotyping. This technique is applicable to the analysis of low-copy-number growth factor transcripts in cells in culture and in vivo.

Actins↗
PubMed1989

Histidine-15: an important role in the cytotoxic activity of human tumor necrosis factor.

The amino acids that are required for the cytotoxic activity of recombinant human tumor necrosis factor-alpha (TNF) were investigated by chemical modification and oligonucleotide-directed site-specific mutagenesis. TNF contains three histidine residues, located at positions 15, 73 and 78. The histidine-specific reagent diethylpyrocarbonate (DEP) was used to chemically modify TNF. The chemical inactivation of the in vitro cytotoxic activity of this lymphokine (using murine L929 target cells) was found to be time- and dose-dependent. Inactivated TNF failed to compete with fully bioactive [125I]TNF for human MCF-7 target cell receptors. Mutant polypeptides of TNF were genetically engineered by oligonucoleotide-directed site-specific mutagenesis. The cytotoxicity of a double histidine mutant, in which histidine-73 and histidine-78 were replaced with glutamine, was not altered and was chemically inactivated by DEP. Substituting glutamine for histidine-15 resulted in 10-15% of the wild-type bioactivity. Replacing histidine-15 with either asparagine, lysine or glycine resulted in a biologically inactive molecule. The data show that the histidine residue at position 15 is an amino acid that is required for the cytotoxic activity of TNF.

Amino Acid Sequence↗
PubMed1989

Developmentally regulated use of alternative promoters creates a novel platelet-derived growth factor receptor transcript in mouse teratocarcinoma and embryonic stem cells.

Embryonal carcinoma and embryonic stem cells expressed a novel form of platelet-derived growth factor receptor mRNA which was approximately 1,100 base pairs shorter than the 5.3-kilobase (kb) transcript expressed in fibroblasts and other cell types. The 4.2-kb stem cell transcript was initiated within the genomic region immediately upstream of exon 6 of the 5.3-kb transcript and therefore lacked the first five exons, which encode much of the extracellular domain of the receptor expressed in fibroblasts. In stem cells, the short form was predominant, although both forms were present at low levels. Following differentiation in vitro, expression levels of the long form increased dramatically. These findings suggest that during early embryogenesis, a stem cell-specific promoter is used in a stage- and cell type-specific manner to express a form of the platelet-derived growth factor receptor that lacks much of the extracellular domain and may function independently of ligand.

Animals↗
PubMed1988

Toxicity of L-proline toward rat hippocampal neurons.

Intrahippocampal injections of L-proline, a neutral amino acid excitant, non-selectively destroyed pyramidal and granule cells. Co-administration of equimolar kynurenate, an excitatory amino acid antagonist, markedly reduced the extent of neuronal cell death. L-Proline destroyed far more hippocampal neurons than D-proline, in keeping with its greater neuroexcitatory potency. L-Proline must therefore be added to the list of excitotoxins present in brain. Its excitotoxic action may be related to the neurological and cognitive deficits associated with hyperprolinemia.

Animals↗