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Biomedical subjects

J McGuire

Publications and source records attributed to J McGuire.

At least 19 recordsLinked to original sources
PubMed1997

Investigation into the concanavalin A reactivity, fucosylation and oligosaccharide microheterogeneity of alpha 1-acid glycoprotein expressed in the sera of patients with rheumatoid arthritis.

alpha 1-Acid glycoprotein (AGP) exists as an heterogeneous population of glycosylated variants (glycoforms) in plasma. The concentration of AGP increases some 2-5 fold in certain pathophysiological states exemplified by the chronic inflammatory disease, rheumatoid arthritis (RA). Moreover, the expressed glycosylation pattern alters in such conditions, indicating functional significance that is likely to be related to the oligosaccharide heterogeneity. We have investigated the heterogeneity of AGP glycosylation using the technique of high pH anion-exchange chromatography (HPAEC). AGP was isolated from the blood of RA sufferers, partially separated by Concanavalin A (Con A) affinity chromatography into bound and non-bound fractions and was enzymatically deglycosylated. Chromatography on the pellicular HPAE resin at pH 13 separated the released oligosaccharides and allowed a comparison of profiles in terms of branching and fucosylation. Results demonstrate an abnormal RA AGP glycosylation, with a tendency towards tri- and tetra-antennary oligosaccharides and enhanced fucosylation, in addition to the possible existence of penta-sialylated RA AGP glycoforms.

Arthritis, Rheumatoid↗
PubMed1997

Surface Tension Kinetics of the Wild Type and Four Synthetic Stability Mutants of T4 Phage Lysozyme at the Air-Water Interface

Surface tension kinetics exhibited by the wild type and selected stability mutants of T4 lysozyme at the air-water interface were monitored with DuNouy tensiometry. Mutant lysozymes were produced by substitution of the isoleucine at position 3 with cysteine, leucine, glycine, and tryptophan. Each substitution resulted in an altered structural stability quantified by a change in the free energy of unfolding. Surface pressure kinetics were compared to the kinetic model evolving from a simple model for protein adsorption. This model allowed for parallel, irreversible adsorption into two states directly from solution, where state 2 molecules were more tightly bound to the surface and occupied greater interfacial area than state 1 molecules. Moreover, the model allowed state 2 molecules to increase spreading pressure more than state 1 molecules occupying the same interfacial area. The model indicated that less stable variants of T4 lysozyme have a greater tendency to adsorb in state 2, and state 2 molecules increase spreading pressure more than state 1 molecules occupying the same interfacial area. While agreement between the model and experimental data was very good at low concentration, these results suggest that a more comprehensive two-state model should account for the influence of surface coverage on the adsorption rate constants.

Journal Article↗
PubMed1997

Surgical staplers: a review.

For almost two centuries, surgeons have been using mechanical devices to join tissue. One of the most successful methods is that of stapling, which has become very common in more recent times. The range of staplers consists of five established stapler categories (circular, linear, linear cutting, ligating and skin staplers), along with recent variations which lend themselves to minimally invasive surgery. Within each category, several commercial models are available, many of which have their own unique features. The procedures which are enhanced by these instruments are many and varied. Applications have been further expanded and improved by the instrument design developments seen in recent years. This review attempts to present a rationalized overview of the array of stapling instruments, with relevant procedures. The authors believe that surgical stapling may be greatly enhanced by further research and development, taking the instrument designs and procedures further into the realm of minimally invasive surgery.

Anastomosis, Surgical↗
PubMed1996

Disruption of the acyl-CoA:cholesterol acyltransferase gene in mice: evidence suggesting multiple cholesterol esterification enzymes in mammals.

The microsomal enzyme acyl-CoA:cholesterol acyltransferase (ACAT; EC 2.3.1.26) catalyzes the esterification of cellular cholesterol with fatty acids to form cholesterol esters. ACAT activity is found in many tissues, including macrophages, the adrenal glands, and the liver. In macrophages, ACAT is thought to participate in foam cell formation and thereby to contribute to atherosclerotic lesion development. Disruption of the gene for ACAT (Acact) in mice resulted in decreased cholesterol esterification in ACAT-deficient fibroblasts and adrenal membranes, and markedly reduced cholesterol ester levels in adrenal glands and peritoneal macrophages; the latter finding will be useful in testing the role of ACAT and macrophage foam cell formation in atherosclerosis. In contrast, the livers of ACAT-deficient mice contained substantial amounts of cholesterol esters and exhibited no reduction in cholesterol esterification activity. These tissue-specific reductions in cholesterol esterification provide evidence that in mammals this process involves more than one form of esterification enzyme.

Adrenal Glands↗
PubMed1996

Functional interference between hypoxia and dioxin signal transduction pathways: competition for recruitment of the Arnt transcription factor.

Hypoxia-inducible factor 1 alpha (HIF-1 alpha) and the intracellular dioxin receptor mediate hypoxia and dioxin signalling, respectively. Both proteins are conditionally regulated basic helix-loop-helix (bHLH) transcription factors that, in addition to the bHLH motif, share a Per-Arnt-Sim (PAS) region of homology and form heterodimeric complexes with the common bHLH/PAS partner factor Arnt. Here we demonstrate that HIF-1 alpha required Arnt for DNA binding in vitro and functional activity in vivo. Both the bHLH and PAS motifs of Arnt were critical for dimerization with HIF-1 alpha. Strikingly, HIF-1 alpha exhibited very high affinity for Arnt in coimmunoprecipitation assays in vitro, resulting in competition with the ligand-activated dioxin receptor for recruitment of Arnt. Consistent with these observations, activation of HIF-1 alpha function in vivo or overexpression of HIF-1 alpha inhibited ligand-dependent induction of DNA binding activity by the dioxin receptor and dioxin receptor function on minimal reporter gene constructs. However, HIF-1 alpha- and dioxin receptor-mediated signalling pathways were not mutually exclusive, since activation of dioxin receptor function did not impair HIF-1 alpha-dependent induction of target gene expression. Both HIF-1 alpha and Arnt mRNAs were expressed constitutively in a large number of human tissues and cell lines, and these steady-state expression levels were not affected by exposure to hypoxia. Thus, HIF-1 alpha may be conditionally regulated by a mechanism that is distinct from induced expression levels, the prevalent model of activation of HIF-1 alpha function. Interestingly, we observed that HIF-1 alpha was associated with the molecular chaperone hsp90. Given the critical role of hsp90 for ligand binding activity and activation of the dioxin receptor, it is therefore possible that HIF-1 alpha is regulated by a similar mechanism, possibly by binding an as yet unknown class of ligands.

Aryl Hydrocarbon Receptor Nuclear Translocator↗
PubMed1996

Prenatal diagnosis for recessive dystrophic epidermolysis bullosa in 10 families by mutation and haplotype analysis in the type VII collagen gene (COL7A1).

BACKGROUND: Epidermolysis bullosa (EB) is a group of heritable diseases that manifest as blistering and erosions of the skin and mucous membranes. In the dystrophic forms of EB (DEB), the diagnostic hallmark is abnormalities in the anchoring fibrils, attachment structures beneath the cutaneous basement membrane zone. The major component of anchoring fibrils is type VII collagen, and DEB has been linked to the type VII collagen gene (COL7A1) at 3p21, with no evidence for locus heterogeneity. Due to life-threatening complications and significant long-term morbidity associated with the severe, mutilating form of recessive dystrophic EB (RDEB), there has been a demand for prenatal diagnosis from families with affected offspring. MATERIALS AND METHODS: Intragenic polymorphisms in COL7A1 and flanking microsatellite markers on chromosome 3p21, as well as detection of pathogenetic mutations in families, were used to perform PCR-based prenatal diagnosis from DNA obtained by chorionic villus sampling at 10-15 weeks or amniocentesis at 12-15 weeks gestation in 10 families at risk for recurrence of RDEB. RESULTS: In nine cases, the fetus was predicted to be normal or a clinically unaffected carrier of a mutation in one allele. These predictions have been validated in nine cases by the birth of a healthy child. In one case, an affected fetus was predicted, and the diagnosis was confirmed by fetal skin biopsy. CONCLUSIONS: DNA-based prenatal diagnosis of RDEB offers an early, expedient method of testing which will largely replace the previously available invasive fetal skin biopsy at 18-20 weeks gestation.

Amniocentesis↗
PubMed1995

The basic helix-loop-helix/PAS factor Sim is associated with hsp90. Implications for regulation by interaction with partner factors.

Sim is a Drosophila developmental basic helix-loop-helix (bHLH) transcription factor containing a Per-Arnt-Sim (PAS) region of homology. Here we demonstrate that Sim, in analogy to the structurally related bHLH/PAS dioxin receptor, was stably associated with the molecular chaperone hsp90. In the case of the dioxin receptor, release of hsp90 and derepression of receptor function appear to be regulated by ligand binding and dimerization with Arnt, a non-hsp90-associated bHLH/PAS factor. Dimerization with Arnt very efficiently disrupted Sim-hsp90 interaction, a process that required both the bHLH and PAS dimerization motifs of Arnt. Moreover, hsp90 was also released upon dimerization of Sim with the Drosophila PAS factor Per, whereas the hsp90-associated dioxin receptor failed to interact with Sim. These results indicate that hsp90 may play a role in conditional regulation of Sim function, and that Per and possibly bHLH/PAS partner factors may activate Sim by inducing release of hsp90 during the dimerization process.

Amino Acid Sequence↗
PubMed1995

Age, substance abuse, and survival of patients with cervical carcinoma.

BACKGROUND: The poor survival of young patients with cervical cancer in a low income, disadvantaged community stimulated an investigation of pathologic and behavioral risk factors. METHODS: The records of 1173 patients with cervical cancer diagnosed in 1967-1988 were evaluated with respect to age, stage, histology, and presenting symptoms. Histopathologic risk factors were evaluated in 196 patients with Stage IB disease treated by initial hysterectomy. Substance abuse behaviors were evaluated for 332 symptomatic patients with Stages IB-III disease diagnosed from 1976 to 1988. RESULTS: There were no significant age-related differences in survival for patients without squamous cell carcinoma or those with Stage IA and asymptomatic Stage IB squamous cell carcinoma. Women age 70 years and older had a poorer survival rate than did younger women with Stages IB-III disease. Symptomatic patients with squamous cell carcinoma younger than age 50 years had a poorer survival than did patients age 50-69 years with Stages IB/IIA, IIB, and III disease. For patients with symptomatic Stage IB tumors, poor prognostic histopathologic factors were distributed equally among women younger than age 50 and those aged 50-69 years. Substance abuse was significantly more prevalent among younger patients, and patients who smoked or abused alcohol or drugs had significantly poorer survival than did nonsubstance abusers. However, in a multivariate analysis of age, stage, and substance abuse, young age remained a significantly poor prognostic factor. CONCLUSIONS: Substance abuse may contribute to poor outcome of young patients with symptomatic squamous cell carcinoma but does not explain adequately their poor survival.

Adult↗
PubMed1995

Heat shock protein hsp90 regulates dioxin receptor function in vivo.

The dioxin (aryl hydrocarbon) receptor is a ligand-dependent basic helix-loop-helix (bHLH) factor that binds to xenobiotic response elements of target promoters upon heterodimerization with the bHLH partner factor Arnt. Here we have replaced the bHLH motif of the dioxin receptor with a heterologous DNA-binding domain to create fusion proteins that mediate ligand-dependent transcriptional enhancement in yeast (Saccharomyces cerevisiae). Previously, our experiments indicated that the ligand-free dioxin receptor is stably associated with the 90-kDa heat shock protein, hsp90. To investigate the role of hsp90 in dioxin signaling we have studied receptor function in a yeast strain where hsp90 expression can be down-regulated to about 5% relative to wild-type levels. At low levels of hsp90, ligand-dependent activation of the chimeric dioxin receptor construct was almost completely inhibited, whereas the activity of a similar chimeric construct containing the structurally related Arnt factor was not affected. Moreover, a chimeric dioxin receptor construct lacking the central ligand- and hsp90-binding region of the receptor showed constitutive transcriptional activity in yeast that was not impaired upon down-regulation of hsp90 expression levels. Thus, these data suggest that hsp90 is a critical determinant of conditional regulation of dioxin receptor function in vivo via the ligand-binding domain.

Animals↗
PubMed1995

Gonadal steroids modulate interleukin-1 receptor antagonist mRNA expression in cultured human monocytes.

This study investigated whether gonadal steroids modulate the expression of the cytokine Interleukin-1 receptor antagonist in monocytes. Human male peripheral monocytes were isolated and cultured in serum free media with serially diluted concentrations of estradiol and progesterone. mRNA expressions with increasing steroid concentrations were compared by reverse transcription-polymerase chain reaction for intracellular and secretory interleukin-1 receptor antagonist specific primers and glyceraldehyde 3-phosphate dehydrogenase primers. Monocyte expression of secretory Interleukin-1 receptor antagonist mRNA was significantly elevated in the presence of normal physiological levels of estradiol (10(-11) M) and progesterone (10(-8) M), while expression was suppressed by higher concentrations of steroids. Intracellular receptor antagonist was also detected. This study is the first to describe the dose related response of cytokine interleukin-1 receptor antagonist to gonadal steroids.

Base Sequence↗
PubMed1995

Influences on the antimicrobial activity of surface-adsorbed nisin.

The efficacy of the antimicrobial peptide nisin was examined after adsorption to silica surfaces. Three protocols were used to evaluate nisin's activity against adhered cells of Listeria monocytogenes: bioassay using Pediococcus pentosaceous FBB 61-2 as the sensitive indicator strain; visualization and enumeration of cells by microscopic image analysis; and viability of adhered cells as determined by lodonitrotetrazolium violet uptake and crystallization. The activity of adsorbed nisin was highly dependent upon conditions of adsorption. The highest antimicrobial activity of adsorbed nisin occurred with high concentrations of nisin (1.0 mg ml-1) and brief contact times (1 h) on surfaces of low hydrophobicity. Sequential adsorption of a second protein (beta-lactoglobulin or bovine serum albumin) onto surfaces consistently resulted in decreased nisin activity. These data provide direction for the development of applications to limit microbial attachment on food contact surfaces through the use of adsorbed antimicrobial peptides.

Adsorption↗
PubMed1995

Expression of hsp90 beta messenger ribonucleic acid in patients with familial glucocorticoid resistance--correlation to receptor status.

We have previously shown an increased specific DNA-binding of liganded unactivated glucocorticoid receptor (GR) to the LTR-region of MMTV DNA in a patient with primary cortisol resistance and receptor thermolability indicating a defective interaction of GR with hsp90. In some patients, however, no apparent receptor abnormality was found in spite of a characteristic phenotype. mRNA expression levels of hsp90 beta were analysed in cultured fibroblasts from patients with known receptor defects, such as thermolability, decreased ligand binding affinity and low receptor expression levels, and from patients with a cortisol resistant phenotype but no detected receptor alteration. Fibroblasts from patients with GR defects expressed higher hsp90 beta mRNA levels as compared to patients with no receptor defects or to healthy controls. These data indicate that GR defects are associated with increased hsp90 beta mRNA levels.

Adrenocortical Hyperfunction↗
PubMed1995

Suppression of Listeria monocytogenes colonization following adsorption of nisin onto silica surfaces.

Nisin is an antimicrobial peptide proven to be an effective inhibitor of gram-positive bacteria. It is known that nisin can adsorb to various surfaces and still retain much of its original activity (M. A. Daeschel, J. McGuire, and H. Al-Makhlafi, J. Food Prot. 55:731-735, 1992). In this study, nisin films were allowed to form on silanized silica surfaces and then exposed to medium containing Listeria monocytogenes. Representative areas were selected from each surface, and images of resident listeriae were obtained at 4-h intervals for 12 h. During this time, cells on surfaces that had been in contact with a high concentration of nisin (1.0 mg/ml) exhibited no signs of growth and many displayed evidence of cellular deterioration. Surfaces treated with a lower concentration of nisin (0.1 mg/ml) had a smaller degree of inhibition. In contrast, both protein-free surfaces and those with films of heat-inactivated nisin allowed attached L. monocytogenes cells to grow and reproduce. These studies, when repeated with a nisin-resistant strain of L. monocytogenes, resulted in no inhibition of growth on surfaces with adsorbed nisin. The bactericidal effect of adsorbed nisin was also studied with iodonitrotetrazolium violet, a tetrazolium salt, which is reduced to a red formazan crystal by viable bacteria. Crystals were visible in 95% of the cells adhered to control surfaces but were present in less than 20% of the cells on surfaces with adsorbed nisin. These data indicate that adsorbed nisin may have potential for use as a food grade antimicrobial agent on food contact surfaces.

Adsorption↗
PubMed1995

Adhesion of Listeria monocytogenes to silica surfaces after sequential and competitive adsorption of bovine serum albumin and beta-lactoglobulin.

Adsorbed bovine serum albumin was resistant to exchange with beta-lactoglobulin, and when albumin was adsorbed from a mixture, its surface concentration increased with time. The passivating character of adsorbed albumin and its resistance to desorption were consistent with the level of Listeria monocytogenes adhesion evoked by albumin-containing protein films.

Adsorption↗
PubMed1995

Distinct roles of the molecular chaperone hsp90 in modulating dioxin receptor function via the basic helix-loop-helix and PAS domains.

The intracellular dioxin receptor mediates signal transduction by dioxin and functions as a ligand-activated transcription factor. It contains a basic helix-loop-helix (bHLH) motif contiguous with a Per-Arnt-Sim (PAS) homology region. In extracts from nonstimulated cells the receptor is recovered in an inducible cytoplasmic form associated with the 90-kDa heat shock protein (hsp90), a molecular chaperone. We have reconstituted ligand-dependent activation of the receptor to a DNA-binding form by using the dioxin receptor and its bHLH-PAS partner factor Arnt expressed by in vitro translation in reticulocyte lysate. Deletion of the PAS domain of the receptor resulted in constitutive dimerization with Arnt. In contrast, this receptor mutant showed low levels of xenobiotic response element-binding activity, indicating that the PAS domain may be important for DNA-binding affinity and/or specificity of the receptor. It was not possible to reconstitute dioxin receptor function with proteins expressed in wheat germ lysate. In line with these observations, reticulocyte lysate but not wheat germ lysate promoted the association of de novo synthesized dioxin receptor with hsp90. At least two distinct domains of the receptor mediated interaction with hsp90: the ligand-binding domain located within the PAS region and, surprisingly, the bHLH domain. Whereas ligand-binding activity correlated with association with hsp90, bHLH-hsp90 interaction appeared to be important for DNA-binding activity but not for dimerization of the receptor. Several distinct roles for hsp90 in modulating dioxin receptor function are therefore likely: correct folding of the ligand-binding domain, interference with Arnt heterodimerization, and folding of a DNA-binding conformation of the bHLH domain. Thus, the dioxin receptor system provides a complex and interesting model of the regulation of transcription factors by hsp90.

Animals↗
PubMed1994

Purification of the DNA binding form of dioxin receptor. Role of the Arnt cofactor in regulation of dioxin receptor function.

The basic region/helix-loop-helix dioxin receptor mediates signal transduction by dioxin (2,3,7,8-tetrachlorodibenzo-p-dioxin). Upon ligand binding the dioxin receptor is converted from a latent, non-DNA binding form to a form that directly interacts with target genes by binding to dioxin-responsive transcriptional control elements. We have purified by conventional and DNA affinity chromatographic procedures the ligand-activated, DNA binding form of dioxin receptor to examine its architecture and functional properties. We observed that the DNA binding activity of the receptor was labile. Most notably, this activity was lost following DNA affinity purification. In complementation experiments we have identified an auxiliary factor(s) that exhibited very poor, if any, intrinsic affinity for the DNA target sequence in vitro but strongly increased the DNA binding activity of the purified receptor-containing material identified by immunoblot analysis. In a similar fashion the in vitro expressed basic region/helix-loop-helix factor Arnt (that has been postulated to modulate the nuclear translocation function of the receptor) reconstituted the DNA binding function of the purified receptor, and the purified auxiliary factor reconstituted receptor activity upon addition to an extract from mutant, Arnt-deficient hepatoma cells. Conversely, purified dioxin receptor reconstituted DNA binding activity in extracts from receptor-deficient hepatoma cells which express bona fide levels of Arnt. Interestingly, UV cross-linking studies using a BrdU-substituted DNA target sequence indicated that primarily the receptor protein was bound to DNA. Moreover, we demonstrate that purified receptor or Arnt exhibited virtually no detectable affinity for the target sequence individually but, in the presence of one another, showed a strong synergy in DNA binding activity in vitro. Importantly, simultaneous expression of the receptor and Arnt resulted in synergistic induction of gene expression in vivo. These data demonstrate that Arnt plays a central role in control of dioxin receptor function by cooperatively modulating the DNA binding activity of the receptor in vitro and dioxin-dependent transactivation in vivo.

Animals↗