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Biomedical subjects

G Hughes

Publications and source records attributed to G Hughes.

At least 127 records · Page 7Linked to original sources
PubMed1996

Interethnic differences in the association of tumor necrosis factor promoter polymorphisms with systemic lupus erythematosus.

OBJECTIVE: To assess the role of polymorphisms in the promoter region of the tumor necrosis factor-alpha (TNF-alpha) gene in susceptibility to systemic lupus erythematosus (SLE). METHODS: Two ethnically different populations of patients with SLE (49 white from the UK and 49 black from South Africa) were genotyped for TNF-238 and TNF-308 polymorphisms using amplification refractory mutation system-polymerase chain reaction (PCR). HLA-DR genotypes were assigned to the patients and controls either serologically or by PCR and sequence specific oligonucleotides. The frequencies of the respective variants were compared between patients and ethnically matched controls. RESULTS: No significant differences were found in the frequency of the TNF-238 variants in either ethnic group. At TNF-308, the TNF2 variant was significantly increased (p = 0.04) in white patients with SLE compared to controls. However, TNF2 was strongly associated with HLA-DR3 (p = 0.00002), which also showed a strong trend of increase in the white patients (p = 0.06). In contrast, in the black patients with SLE in whom DR2 but not DR3 was increased, the frequency of TNF2 was actually reduced rather than increased. CONCLUSIONS: The increase of TNF2 in Caucasians with SLE is most likely due to linkage disequilibrium between TNF2 and DR3. Furthermore, the observation that TNF2 seems to be reduced in blacks with SLE strongly suggests this polymorphism is not an independent risk factor for SLE. Overall, our data indicate that the TNF-238 and TNF-308 promoter polymorphisms do not confer susceptibility to SLE.

Base Sequence↗
PubMed1995

The hydrophilic domain of phospholamban inhibits the Ca(2+)-ATPase--the importance of the method of assay.

The peptide MEKVQYLTRSAIRRASTIEMPQQAR-Cys representing residues 1-25 of phospholamban (PLN) decreases by 40% the maximal state rate of ATP hydrolysis by the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum (SR), measured at saturating concentrations of Ca2+. The pattern of Ca2+ uptake by SR vesicles in the presence of oxalate is complex, with an initial fast phase being followed by a lag phase and a second, slower phase of Ca2+ accumulation. PLN(1-25) reduces the rate of the slower phase of Ca2+ accumulation by 30%. However, if the level of accumulation of Ca2+ is measured after 2 min., the effect of PLN(1-25) is much less marked. It is concluded that PLN(1-25) inhibits the ATPase, but that the effects of this inhibition are not apparent under some assay conditions.

Amino Acid Sequence↗
PubMed1995

Epitope specificity of monoclonal anti-beta 2-glycoprotein I antibodies derived from patients with the antiphospholipid syndrome.

beta 2-Glycoprotein I (beta 2GPI) has been identified as a cofactor in the recognition of the phospholipid Ag cardiolipin (CL) by anticardiolipin Ab (aCL) purified from patients with autoimmune diseases. However, there is considerable controversy as to the exact nature of the epitopes to which these Abs are directed. mAb derived from patients with the antiphospholipid syndrome bound to CL only in the presence of beta 2GPI. Synthetic peptides that span the fifth C-terminal domain of beta 2GPI supported the binding of one of the mAbs to CL in a beta 2GPI-free system. These peptides possessed the phospholipid binding sequence Cys281-Lys-Asn-Lys-Glu-Lys-Lys-Cys288. Three of the mAbs bound to beta 2GPI that had been adsorbed on gamma-irradiated microtiter plates. Binding to beta 2GPI was inhibited in a dose-dependent manner by the peptides from the carboxyl-terminal end of beta 2GPI and soluble beta 2GPI, indicating that the mAb bound to peptides and beta 2GPI in free solution. Thus, mAbs derived from patients with the antiphospholipid syndrome have specificity for epitopes on the fifth domain of beta 2GPI. Our results support the idea that beta 2GPI acts as a primary Ag for these Abs.

Adult↗
PubMed1995

Effects of polycations on Ca2+ binding to the Ca(2+)-ATPase.

Spermine and polyarginine have been shown to increase the rate of dissociation of Ca2+ from the Ca(2+)-ATPase of skeletal-muscle sarcoplasmic reticulum. They also decrease the affinity of the ATPase for Mg2+ as detected by changes in the fluorescence intensity of the ATPase labelled with 4-(bromomethyl)-6,7-dimethoxycoumarin (DMC). Polyarginine itself also decreases the fluorescence intensity of DMC-labelled ATPase. These results are consistent with binding of spermine and polyarginine to a gating site controlling the rate of access of Ca2+ to its binding sites on the ATPase. A basic peptide PLN-(1-25) corresponding to residues 1-25 of phospholamban had no effect on the rate of dissociation of Ca2+ or on the fluorescence of DMC-labelled ATPase. Spermine, polyarginine and PLN-(1-25) all increased the equilibrium constant E1/E2, and spermine and polyarginine increased the rate of Ca2+ binding to the ATPase, consistent with an increase in the rate of the E2-->E1 transition. Spermine displaced Tb3+ and Ruthenium Red from the ATPase, consistent with binding in the stalk region of the ATPase. Polyarginine and PLN-(1-25), however, had no effect on Tb3+ or Ruthenium Red binding, suggesting a greater specificity in binding basic peptides to the ATPase than spermine.

Amino Acid Sequence↗
PubMed1995

Phylogenetic relationships among transposon-like elements in human and primate DNA.

A THE-1 sequence in intron 7 of the human dystrophin gene has been found to represent a new subfamily of THE-1 elements. The sequence is closely related to the MstII family of repetitive sequences and is more like single-copy sequences found in the galago genome than any other THE-1 sequence previously reported. This new THE-1 sequence has been compared with two other complete THE-1 sequences and three related long-terminal repeat elements that we have previously found in intron 7 of the dystrophin gene, and with members of the same family from elsewhere in the primate genome. Parsimony and deletion analysis show that the cluster of THE-1 sequences in intron 7 of the dystrophin gene has arisen from at least three individual insertion events, rather than from the insertion and duplication of a single progenitor sequence.

Animals↗
PubMed1995

Cholecystokinin-8 induces edematous pancreatitis in dogs associated with short burst of trypsinogen activation.

To study the early pathogenesis of acute edematous pancreatitis in dogs, we examined the relationship of pancreatic hyperstimulation with cholecystokinin-8 (10 micrograms/kg/hr intravenously for 6 hr) to alterations in circulating pancreatic enzymes and pancreatic morphology with special reference to trypsinogen activation. Cholecystokinin-8 infusion was associated with increases in plasma amylase, lipase, trypsin-like immunoreactivity, and plasma and urine trypsinogen activation peptide. Pancreatic parenchymal swelling and interlobular and subcapsular fluid accumulations were detected ultrasonographically within 2 hr of cholecystokinin-8. Circulating trypsin-like immunoreactivity and trypsinogen activation peptide in urine reached a peak at 2 and 4 hr, respectively, then declined despite progressive increases in circulating amylase and lipase and intrapancreatic fluid. No significant changes were observed in dogs receiving a saline infusion. This study illustrates that cholecystokinin-8 induces edematous pancreatitis in dogs that is associated with a short-lived burst of trypsinogen activation.

Acute Disease↗
PubMed1995

Sequence of a transposon identified as Tn1000 (gamma delta).

We report the complete sequence of a transposon found in a cosmid clone of a human DNA sequence. The transposon is identified as the Escherichia coli transposon Tn1000 (also known as gamma delta) on the basis of the identity of the restriction map of the new sequence with that previously recorded for Tn1000 and homology between parts of the new sequence and that of published fragments of Tn1000 sequence. The transposon, which comprises 5,981 nucleotides including two 35 bp inverted terminal repeat sequences (ITRs), contains three open reading frames. The sequence of the resolvase coding region (tnpR) is identical to that published by others. A second reading frame can be identified as the tnpA gene, coding for the transposase, on the grounds of its strong homology with the corresponding gene from transposon Tn3. The third reading frame has the potential to code for a protein of unknown function containing 698 amino acids.

Amino Acid Sequence↗
PubMed1994

The hydrophilic domain of phospholamban inhibits the Ca2+ transport step of the Ca(2+)-ATPase.

The peptide MEKVQYLTRSAIRRASTIEMPQQAR-Cys corresponding to residues 1-25 of phospholamban was found to inhibit the ATPase activity of skeletal muscle Ca(2+)-ATPase, but to have no effect on the Ca(2+)-dependence of its activity. The peptide was found to decrease the rate of the Ca2+ transport step (E1PCa2-->E2P) by a factor of 2.4. The rate of this same step was decreased by poly(L-Arg) by a factor of 2.2. The peptide shifted the E2-E1 equilibrium of the ATPase towards E1 by a factor of 4 due to stronger binding to the E1 than to the E2 conformation of the ATPase; dissociation constants for binding to E1 and E2 were estimated as 3 and 10 microM respectively. The peptide had no effect on the level of phosphorylation by Pi in the absence of Ca2+ or on the rate of phosphorylation by ATP in the presence of Ca2+.

Adenosine Triphosphatases↗
PubMed1994

Mechanism of inhibition of the Ca(2+)-ATPase by spermine and other polycationic compounds.

The ATPase activity of the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum is inhibited by a variety of polyamines, including spermine, spermidine, and poly(arginine). The effects of spermine on the ATPase are highly specific. It has no effect on the affinity of the ATPase for Ca2+ or ATP, and no effect on the rate of phosphorylation by ATP. When the ATPase is phosphorylated with Pi in the presence of dimethyl sulfoxide at pH 6.0, and then dephosphorylation is induced by dilution in buffer at pH 7.5 in the absence of dimethyl sulfoxide, spermine is found to have no effect on the rate of dephosphorylation. If the ATPase is phosphorylated with [gamma-32P]ATP and the rate of loss of radiolabeled phosphoenzyme is measured following the addition of unlabeled ATP, spermine is found to decrease the rate of loss of radiolabel, consistent with an effect of spermine on the rate of the Ca2E1P-->E2P step. Direct measurement confirms that spermine decreases the rate of dissociation of Ca2+ from the phosphorylated ATPase (Ca2E1P-->E2P), with the decrease in the rate of this step explaining the inhibition of ATPase activity. Spermine also increases the equilibrium constant E1/E2 and inhibits phosphorylation of the ATPase by Pi by competition with the Mg2+ essential for the reaction. It is suggested that spermine could bind to the site on the Ca(2+)-ATPase that interacts with phospholamban.

Amino Acid Sequence↗
PubMed1994

Mechanism of stimulation of the calcium adenosinetriphosphatase by jasmone.

The ATPase activity of the Ca(2+)-ATPase of skeletal muscle sarcoplasmic reticulum is increased ca. 3-fold at 25 degrees C and pH 7.2 by jasmone at a concentration of 100 microM, concentrations above 10 mM resulting in reduced stimulation. Stimulation by methyl jasmonate, menthol, or menthone requires much higher concentrations. Effects of jasmone are much less marked at 37 degrees C than at 25 degrees C, and much higher concentrations of jasmone are required to stimulate ATPase activity at pH 6.0 than at pH 7.2. The effects of jasmone on the ATPase are highly specific. Jasmone has no effect on the E1<-->E2 equilibrium constant for the ATPase or on Ca2+ binding. The rate of phosphorylation by ATP is unaffected by jasmone, and only small effects are seen on the reaction of the phosphorylated ATPase with ADP. Jasmone does, however, increase the rate of dephosphorylation by a factor of 2 and the rate of dissociation of Ca2+ from the phosphorylated ATPase by a factor of 3. Jasmone decreases the level of phosphorylation of the ATPase by P(i) in the absence of Ca2+ consistent with a decrease in the equilibrium constant E2P(i)Mg<-->E2PMg. Reconstitution of the ATPase with dimyristoleoylphosphatidylcholine decreases the stoichiometry of Ca2+ binding from the usual 2:1 to 1:1. Unlike other hydrophobic molecules, jasmone failed to reverse this effect. Further, jasmone had very similar effects on the activity of the ATPase reconstituted with either dimyristoleoylphosphatidylcholine or dioleoylphosphatidylcholine, whereas other hydrophobic molecules caused a much greater stimulation of activity for the ATPase reconstituted with the short-chain lipid.

Adenosine Diphosphate↗
PubMed1993

A comparison of subcutaneous low-molecular-weight heparin with warfarin sodium for prophylaxis against deep-vein thrombosis after hip or knee implantation.

BACKGROUND: Deep-vein thrombosis is a potentially life-threatening complication of total hip or knee replacement. There are few data on the effectiveness and safety of warfarin as compared with low-molecular-weight heparin as prophylaxis against this problem. METHODS: We therefore performed a randomized, double-blind trial in 1436 patients to evaluate the effectiveness and safety of low-molecular-weight heparin (given subcutaneously once daily) as compared with adjusted-dose warfarin to prevent venous thrombosis after hip or knee replacement. Treatment with the drugs was started postoperatively. The primary end point was deep-vein thrombosis as detected by contrast venography (performed a mean of 9.4 days after surgery in each group). RESULTS: Among the 1207 patients with interpretable venograms, 231 of 617 patients (37.4 percent) in the warfarin group and 185 of 590 patients (31.4 percent) in the low-molecular-weight-heparin group had deep-vein thrombosis (P = 0.03). The reduction in risk with low-molecular-weight heparin as compared with warfarin was 16 percent, and the absolute difference in the incidence of venous thrombosis was 6 percent in favor of low-molecular-weight heparin (95 percent confidence interval, 0.8 to 11.4 percent). The incidence of major bleeding was 1.2 percent (9 of 721 patients) in the warfarin group and 2.8 percent (20 of 715 patients) in the low-molecular-weight-heparin group (P = 0.04), and the absolute difference was 1.5 percent in favor of warfarin (95 percent confidence interval, 0.1 to 3.0 percent). CONCLUSIONS: Our data demonstrate that the small reduction in the incidence of venous thrombosis with low-molecular-weight heparin, as compared with warfarin, was offset by an increase in bleeding complications. Although the use of low-molecular-weight heparin is simpler, because it is administered subcutaneously without the need for monitoring, it may be more costly than warfarin. Warfarin is inexpensive, but the overall cost of its use is increased by the need to monitor the intensity of anticoagulation. At this time it is unclear which of these approaches is the most cost effective.

Administration, Oral↗
PubMed1993

Seroepidemiological study of Taenia saginata cysticercosis in Swaziland.

A cross-sectional study of Taenia saginata cysticercosis in Swaziland using a serodiagnostic ELISA for parasite antigen is described. The seroprevalence and the levels of parasite antigen were compared in the sera of cattle from different geographical localities, and from areas of high or low population density. Cattle from the Lowveldt region, which has a hot and dry climate relative to the other areas investigated, exhibited significantly higher serum antigen levels. Seroprevalence was also higher in the Lowveldt but this difference was not found to be significant. Within the Lowveldt, antigen levels were found to be slightly elevated in cattle from more highly populated areas. It is suggested that either human behaviour and/or practices in animal husbandry, or increased susceptibility of cattle to reinfection at certain times of the year, may enhance transmission in the Lowveldt since climatic conditions in this region are not conducive to transmission.

Animals↗
PubMed1993

Environmental factors predicting nephritis in systemic lupus erythematosus.

OBJECTIVES: To evaluate social class, ethnic origin, and various endocrine variables as potential risk factors in the development of nephritis in patients with systemic lupus erythematosus (SLE). METHODS: A cross-sectional survey was carried out of all outpatients with SLE attending the lupus Clinic of St Thomas's Hospital from March to October 1992 using retrospective survival data. The main outcome measure was the duration of SLE before the onset of nephritis. RESULTS: Two hundred and ninety six women and 11 men were studied; the male patients were excluded from the analysis. Univariate analysis showed an increased risk of nephritis in patients with SLE of West Indian origin with 54 v 19% with nephritis at five years, in patients of lower social class, in patients who did not drink alcohol, and in those with a history of fetal loss after the onset of lupus. No significant effect of the age of onset of SLE, use of oral contraceptives, normal pregnancy, or smoking was seen. Multivariate analysis showed that ethnic origin did not influence the risk of nephritis independently of social class. CONCLUSIONS: Factors associated with socioeconomic deprivation may increase disease severity in patients with SLE.

Abortion, Spontaneous↗
PubMed1993

Laser welding of fascial grafts and its potential application in tympanoplasty: an animal model.

This study evaluates the welding effect of argon laser on fascial grafts and its potential application in tympanoplasty. An animal model was designed so that surgically induced perforations of the lumbar fascia of the animals were grafted in an underlay fashion. Each graft was "spot welded" around the circumference of the perforation using a hand-held argon laser. Various lasing parameters were used on different grafts. Control perforations were grafted but not welded. A total of 96 perforations was studied. Weld sites were evaluated both histologically and by tensile strength measurement at the end of surgery, and at 7, 14, and 21 days postoperatively. Comparison with controls showed a higher tensile strength for welded grafts, which was most significant in the early postoperative period (p < 0.001). Histologically, it seems that the basic mechanism of fascial welding involves liquification and denaturation of extravasated proteins at the weld sites. Correlation between the extent of thermal damage on the tissues and the various lasing parameters is described. Based on the well-documented safety of argon laser in otologic surgery, and the successful welding of fascial grafts in this study, argon laser may prove beneficial in welding temporalis fascia grafts in tympanoplasty.

Animals↗