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Biomedical subjects

L Guo

Publications and source records attributed to L Guo.

At least 289 records · Page 16Linked to original sources
PubMed1994

Binding of serum amyloid P component to heparin in human serum.

It has been proposed that the function of serum amyloid P component (SAP) may closely relate with its binding to polysaccharides, especially glycosaminoglycans. We employed a quantitative immunoelectrophoresis (QIE) method and a native polyacrylamide gel electrophoresis (PAGE) method to characterize the SAP-heparin binding in soluble state. The SAP-heparin binding showed positive cooperativity. The apparent numbers of heparin molecules bound to SAP varied with the calcium concentration with a ratio of 1:1 (SAP/heparin), a Kd of 2.06 x 10(-7) M at 0.1 mM CaCl2 and a ratio of 1:1.6 (SAP/heparin), a Kd of 3.91 x 10(-7) M at 2 mM CaCl2, when estimated by the QIE method. No binding between SAP and heparin was observed in the absence of calcium. Magnesium and barium failed to induce the formation of SAP-heparin complex. Furthermore, they showed inhibitory effects on the calcium-mediated complex formation. We propose that heparin might be a regulator to modulate the anticoagulant activity of SAP and a useful drug to prevent SAP deposition on amyloid deposits.

Barium↗
PubMed1994

Internal lysine palmitoylation in adenylate cyclase toxin from Bordetella pertussis.

A number of bacterial protein toxins, including adenylate cyclase (AC) toxin from Bordetella pertussis, require the product of an accessory gene in order to express their biological activities. In this study, mass spectrometry was used to demonstrate that activated, wild-type AC toxin was modified by amide-linked palmitoylation on the epsilon-amino group of lysine 983. This modification was absent from a mutant in which the accessory gene had been disrupted. A synthetic palmitoylated peptide corresponding to the tryptic fragment (glutamine 972 to arginine 984) that contained the acylation blocked AC toxin-induced accumulation of adenosine 3',5'-monophosphate, whereas the non-acylated peptide had no effect.

Acylation↗
PubMed1994

Conversion of vestitone to medicarpin in alfalfa (Medicago sativa L.) is catalyzed by two independent enzymes. Identification, purification, and characterization of vestitone reductase and 7,2'-dihydroxy-4'-methoxyisoflavanol dehydratase.

Pterocarpan phytoalexins are antimicrobial compounds in leguminous plants. The final step of pterocarpan biosynthesis, conversion of vestitone to medicarpin, was thought to be catalyzed by a single enzyme "pterocarpan synthase." We have shown that the pterocarpan synthase activity observed in crude extracts of alfalfa suspension cell cultures is the sum of two independent enzymatic activities: vestitone reductase, which catalyzes the NADPH-dependent reduction of vestitone to 7,2'-dihydroxy-4'-methoxyisoflavanol (DMI), and DMI dehydratase, which catalyzes loss of water and closure of an ether ring to form medicarpin. The first enzyme, vestitone reductase, was purified 1,840-fold to homogeneity by a 5-step procedure. Purified vestitone reductase showed a single band on SDS-polyacrylamide gel electrophoresis with an estimated molecular mass of 38 kDa. The native molecular mass measured by gel filtration was shown to be 34 kDa, indicating that vestitone reductase is a monomer. Vestitone reductase has strict substrate stereo specificity for (3R)-vestitone with a Km value of 45 microM. The second enzyme, DMI dehydratase, was partially purified 962-fold. DMI dehydratase had a native molecular mass of 38 kDa as estimated by gel filtration and a Km value of 5 microM for DMI. Both enzymes have a temperature optimum of 30 degrees C and a pH optimum of 6.0. The discovery of vestitone reductase and DMI dehydratase will facilitate future genetic manipulation of pterocarpan biosynthesis.

Benzopyrans↗
PubMed1994

A case report of deficiency in an inhibitor of calcium-dependent association of protein S with C4B-binding protein suggested by a modified crossed immunoelectrophoresis.

We have experienced a coagulation factor VIII-deficient patient whose plasma has normal protein S (PS) activity and masses of free PS and its bound form in complex with C4b-binding protein (C4BP). Although the patient's plasma showed a normal ratio of free PS to PS-C4BP complex in the presence of 5 mM EDTA, the plasma gave an abnormally retarding major C4BP peak together with a major PS peak in the crossed immunoelectrophoresis (CIE) in the presence of 2 mM CaCl2. It was revealed that the major peak was formed by a mixture of PS-C4BP complex and free form. The addition of normal human plasma (NHP) to the patient's plasma inhibited the retardation of the major PS-C4BP complex. These suggest that the patient's plasma lacks some component(s) to inhibit Ca(2+)-dependent association of PS with C4BP.

Adult↗
PubMed1994

Synaptology of cultured olfactory bulb cells.

Cultured embryonic mouse olfactory bulb cells formed asymmetric, symmetric, axodendritic, and dendrodendritic synapses. These neurons contained electron lucent, dense core, and coated vesicles. Dense core and coated vesicles had an average diameter of 71 and 80 nm, respectively. Two statistically different populations of electron lucent vesicles were found, based on synaptic symmetry: electron lucent vesicles from asymmetric synapses had an average diameter of 46 nm with an estimated volume of 49,000 nm3, whereas those from symmetric synapses had an average diameter of 44 nm and an estimated volume of 42,000 nm3. Because these values are similar to those found for intact olfactory bulb, the synapses of these cultured cells have some of the same morphological characteristics as those in the intact olfactory bulb.

Animals↗
PubMed1994

Risk factors for oesophageal cancer in northeast China.

A hospital-based case-control study of oesophageal cancer was carried out in the Heilongjiang Province, a low-risk area for oesophageal cancer in China. From May 1985 to May 1989, 196 histologically confirmed cases and 392 controls with other (non-neoplastic) diseases were personally interviewed in the wards of 5 major hospitals. Information was obtained about usual consumption in the early 1980s of 32 major contributors to the diet in the province, socio-demographic status, smoking and alcohol consumption. Odds ratios (OR) were obtained from logistic regression models, and confounding was controlled by means of multivariate models. Smoking and alcohol consumption were major risk factors for oesophageal cancer in this population. Smokers of handmade cigarettes exhibited a particularly high risk. A near multiplicative synergism was found between smoking and alcohol consumption. There was a significant inverse dose-risk trend for combined consumption of vegetables and fruits; a 300-g increase per day lowered risk by 35%. Vitamin C intake was negatively associated with risk; a 100-mg increase per day lowered risk by 39%. Our data suggest a modifying effect of vitamin C and beta-carotene on risk associated with smoking, but the power of analyses was low. Salt, salt-preserved foods and pickled vegetables were not associated with increased risk. High temperature of meals and drinks was a strong risk indicator in this population. The strength of tea and overall tea consumption were independent determinants of the risk.

Adult↗
PubMed1994

Selective responsiveness of human breast cancer cells to indole-3-carbinol, a chemopreventive agent.

BACKGROUND: Indole-3-carbinol (I3C), a compound found in cabbage, broccoli, and brussels sprouts, inhibits the growth of mammary tumors when fed to certain strains of mice. The chemopreventive and antitumor effects of I3C depend on the species and tissue type. The mechanism of action and specific human cell types that respond to I3C are not known. PURPOSE: Our purpose was to study the mechanism of action of I3C in estrogen-responsive (MCF-7) and estrogen-nonresponsive (MDA-MB-231) human breast cancer cell lines. METHODS: Estrogen responsiveness was determined by the ability of estradiol to stimulate the growth of breast cancer cells deprived of estrogen. The effect of I3C was measured on cell growth, estradiol metabolism, and level of cytochrome P-4501A1. Growth was measured by cell counts and soft-agar assay, estrogen metabolism was examined by a radiometric assay, and the level of cytochrome P-4501A1 was measured by Western blots with a polyclonal antibody. RESULTS: I3C inhibits the growth of estrogen-responsive cell line MCF-7 but has little effect on estrogen-nonresponsive cell line MDA-MB-231. Specific C-2 hydroxylation of estrogen and induction of cytochrome P-4501A1 was enhanced by I3C in the MCF-7 but not in the MDA-MB-231 cells. CONCLUSION: I3C has specific antigrowth effects in human breast cancer cells. The inhibitory effects of I3C may involve selective induction of estradiol metabolism and the related cytochrome P-450 system that may be limited to estrogen-sensitive cells.

Anticarcinogenic Agents↗
PubMed1994

Morphological characteristics of cultured olfactory bulb cells.

Cultured olfactory bulb cells from embryonic mice had ultrastructural characteristics similar to those of many cell types in the intact adult mouse olfactory bulb. Identified cultured cells included mitral/tufted cells, granule cells, short-axon cells, and fibrous and protoplasmic astrocytes. Cultured neurons were found as individual cells, clusters or aggregates. Clusters consisted of a loose array of neurons that appeared to be densely interconnected by neurites. However, few neurites or fascicles emanated from clusters to adjoining areas. Aggregates consisted of many small, usually rounded, neurons piled on top of one larger neuron, or on more than one, with typically many neurites and fascicles projecting to adjacent aggregates, clusters or individual neurons. Neurites of cultured olfactory bulb cells were well developed, and some were several millimeters long. Synapses were very prominent in these cultures, especially in aggregates, clusters, and fascicles. Electron-lucent, dense-core, and coated vesicles were present. Polarity, shape, and length of the long axis (size) of 815 cultured neurons, identified by positive anti-microtubule-associated protein 2 staining, were documented. Cultured neurons varied in size from 9 to 27 microns, with an average size of 16 microns. Elliptical bipolar (35%), triangular multipolar (21%), and round unipolar (15%) were the most common polarity/shape combinations found in culture. Multipolar, triangular, triangular multipolar, and elliptical bipolar cells increased in size with increasing age of culture. The relative proportions of triangular, multipolar, elliptical multipolar, and triangular multipolar cells decreased, whereas the relative proportions of round, unipolar, and round unipolar cells increased with increasing age of culture. These changes in population subtypes and cell size may indicate continued differentiation and maturation of cultured neurons.

Animals↗
PubMed1994

Inhibition of gp120-CD4 interaction and human immunodeficiency virus type 1 infection in vitro by pyridoxal 5'-phosphate.

Pyridoxal 5'-phosphate and related compounds were tested for their ability to inhibit gp120-CD4 interaction and human immunodeficiency virus infection in vitro. The results show that pyridoxal 5'-phosphate is a unique CD4 antagonist whose antiviral potency derives from the presence of both lysine-reactive and anionic substituents.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1994

[Studies on MDA and MDA/MDAa in patients with retinitis pigmentosa].

With fluorimetry, the concentration of malondialdehyde (MDA) and the ratio of MDA before and after the blood platelets activated (MDA/MDAa) were determined in patients with retinitis pigmentosa (RP). The results showed the above two parameters were statistically higher than those of the normal controls, which indicated the superoxidation metabolism increased and the blood was in a state of hypercoagulation in RP patients. The reasons for the results and their roles in RP disease were discussed. Treatments with anti-lipid, and anti-coagulation drugs combined with Chinese medicines were suggested.

Adolescent↗
PubMed1994

[Promotion of wound healing with fibroblast growth factor in combined burn radiation injury].

Rats were subjected to 15% burn and severe radiation injury. Recombinant bFGF and simple support treatment were used to treat local wound and total body injury. The results indicated that wound healing was improved by 28.5%, and the time required for 50% area of healing was 9 days earlier in the treated group than control group 60 days after injury. Pathological observation showed that bFGF stimulated proliferation of fibroblast and collagen synthesis. It improved regeneration of capillary and formation of granulation tissue. In the early phase, bFGF enhanced reactive inflammation in the wound and phagocytosis of leucocytes in the body, and enhanced recovery of natural killing activity of spleen cells. These reactions would be beneficial to local wound healing.

Administration, Topical↗
PubMed1994

[Enlarged and prolongated cochlear microphonics and its clinical significance].

Bilateral cochlear microphonics (CM) were evoked by tone burst simultaneously. A speaker was put in head-foot axis 2m from the mid-point of a given line connecting the bilateral external meatus. Seven normal persons and 106 cases of unilateral sensory hearing loss and recruitment were examined. When recruitment was present, CM at corresponding frequencies were enlarged and prolongated. In 62 cases CM delayed slowly, while other 27 cases quickly. In addition to 2 cases of bilateral Ménière disease with sensory hearing loss and recruitment, CM were enlarged and prolongated at some frequencies in left ears and at other frequencies in right ears in accordance with predominant recruitment. Meanwhile CM of the opposite normal ear decreased obviously. CM could not be evoked from profound and totally deaf ears.

Acoustic Stimulation↗
PubMed1994

[Site-directed mutagenesis at Ser177 of penicillin G acylase gene].

Site-directed mutagenesis was performed at Ser177 of Penicillin G Acylase (PGA) gene of E. coli by gap duplex method. Screened by 2-nitro-5-phenylacetaminobenzoic acid (NIPAB) test paper assay and confirmed by DNA sequencing, the mutants Cys177, Gly177, Arg177 and Asn177 were obtained. They have no activity of PGA. The mutant enzyme was expressed and detected by PAGE. It is suggested that Ser177 is at the substrate binding center of PGA and can not be replaced.

Base Sequence↗
PubMed1993

Amino acid N-malonyltransferases from mung beans. Action on 1-aminocyclopropane-1-carboxylic acid and D-phenylalanine.

1-Aminocyclopropane-1-carboxylate (ACC) N-malonyltransferase from etiolated mung bean hypocotyls was examined for its relationship to D-phenylalanine N-malonyltransferase and other enzymes which transfer malonyl groups from malonyl-CoA to D-amino acids. Throughout a 3600-fold purification the ratio of D-phenylalanine N-malonyltransferase activity to ACC N-malonyltransferase activity was unchanged. Antibodies raised against purified ACC N-malonyltransferase 55-kDa protein were also able to precipitate all D-phenylalanine-directed activity from partially purified mung bean extracts. The irreversible inhibitors phenylglyoxal and tetranitromethane reduced malonyltransferase activity towards D-phenylalanine to the same extent as that for ACC. In addition, several other D-amino acids, particularly D-tryptophan and D-tyrosine, were able to inhibit action towards both ACC and D-phenylalanine. These lines of evidence suggest that a single enzyme is capable of promoting malonylation of both ACC and D-phenylalanine. Km values for D-phenylalanine and malonyl-CoA were found to be 48 and 43 microM, respectively; these values are 10-fold lower than the corresponding values when ACC was substrate. Coenzyme A was a noncompetitive (mixed type) product inhibitor towards malonyl-CoA at both unsaturated and saturated ACC concentrations. The enzyme was also inhibited uncompetitively at high concentrations of malonyl-CoA. We propose that the enzyme follows an Ordered Bi-Bi reaction pathway, with the amino acid substrate being bound initially.

Acyltransferases↗
PubMed1993

A sensitive peroxidase staining immunoblotting method for measuring total protein S in human plasma.

In plasma, protein S is found in its free form and as a complex with C4b-binding protein. After 125I-protein S was added to normal human plasma and applied to SDS-8% polyacrylamide gel electrophoresis, the autoradiogram of the gel showed only one single band at free protein S position. Applying this evidence, we have developed a peroxidase staining Western Blotting method to quantitate total protein S in human plasma which consists of sodium dodecyl sulfate polyacrylamide gel electrophoresis followed by blotting to nitrocellulose membrane and a sensitive avidin-biotinylated peroxidase staining method (ABC technique). The measurement of protein S by the immunoblotting was reproducible and the coefficient of variation was 7%. As little as 1 ng of protein S could be detected. C4b-binding protein did not affect the measurement of protein S. Compared to other immunoassays, this peroxidase staining immunoblotting method has the advantage of directly estimating the apparent molecular weight of protein of interest, eliminating nonspecific stain and having high sensitivity without using radioisotope.

Avidin↗
PubMed1993

Targeting expression of keratinocyte growth factor to keratinocytes elicits striking changes in epithelial differentiation in transgenic mice.

Keratinocyte growth factor (KGF) is a member of the fibroblast growth factor (FGF) family. Synthesized by cells of the dermal component of skin, KGF's potent mitogenic activity is on the epidermal component, which harbors the receptors for this factor. To explore the possible role of KGF in mesenchymal-epithelial interactions in skin, we used a human keratin 14 promoter to target expression of human KGF cDNA to the stratified squamous epithelia of transgenic mice. Mice expressing KGF in their epidermis typically appeared frail and weak, and often had grossly wrinkled skin. These mice exhibited a gross increase in epidermal thickness accompanied by alterations in epidermal growth and differentiation. Most remarkably, animals displayed several striking and unexpected changes, including a marked suppression of hair follicle morphogenesis and suppression of adipogenesis. With age, some animals developed gross transformations in the tongue epithelium and in epidermis. In addition, they exhibited elevated salivation and their salivary glands showed signs of altered differentiation. Collectively, our findings provide new and important insights into the roles of KGF, implicating this potent growth factor in eliciting global effects not only on growth, but also on development and differentiation, of skin and other tissues. In particular, KGF seems to interfere with signalling of some mesenchymal-epithelial interactions.

Animals↗