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Biomedical subjects

G Bray

Publications and source records attributed to G Bray.

At least 19 recordsLinked to original sources
PubMed2001

Low factor VIII recovery in haemophilia A patients without inhibitor titre is not due to the presence of anti-factor VIII antibodies undetectable by the Bethesda assay.

Measurements of factor VIII (FVIII) recovery in previously untreated patients with haemophilia A were done as part of the clinical trial of safety and efficacy of the recombinant FVIII, Recombinate. In 22 of 72 assessable patients, positive inhibitor titres > or = 0.6 Bethesda units mL-1 were detected by the Bethesda assay in one or more plasma samples, and the remaining 50 patients were negative at all timepoints. Of the latter group, 16 individuals without inhibitors unexpectedly had both normal (111) and low (52) recoveries during the study. We investigated the possibility that other antibodies not detectable in the Bethesda assay were responsible for the low recovery, by using a highly sensitive immunopreciptation (IP) assay for detection of all antiFVIII antibodies. Eight of the 16 patients with low and normal recoveries did indeed have antibodies detected by the IP assay, and the remaining eight were negative. Four antibody-positive individuals had insignificantly low titres, and the other four had modest to high titres. In the latter group, antibodies were found with similar frequencies and titre in plasmas from patients with low or normal recovery. Low recovery in haemophilia A patients without inhibitor titres must therefore be attributed to factors other than antiFVIII.

Antibodies↗
PubMed2000

A long-term, multicenter, open-label study of risperidone in elderly patients with psychosis. On behalf of the Risperidone Working Group.

RATIONALE: Studies have shown that risperidone is safe and efficacious in young and middle-aged adults with chronic schizophrenia, but considerably fewer data are available on the treatment of elderly patients with schizophrenia or other psychotic disorders, particularly long-term outcomes. OBJECTIVE: A 12-month, open-label study was conducted to assess the effects of risperidone in elderly, chronically ill, psychotic patients. METHODS: This study enrolled 180 elderly, chronically ill, psychotic patients (median age, 72 years [range 54-89]), 97 of whom completed the 12-month study. At endpoint, the mean dose of risperidone was 3.7 mg/day. RESULTS: Clinical improvement (> or =20% reduction in Positive and Negative Syndrome Score [PANSS] total score) was achieved by 54% of patients at endpoint. There were significant reductions in PANSS total, subscale (positive, negative, and general psychopathology), and cognition cluster scores at endpoint (p<0.001). Clinical Global Impressions severity of illness scores showed continued improvement through month 12 (p<0.001). In contrast, PANSS data from a historical comparable control group of patients receiving conventional antipsychotic agents showed no symptom improvement over a 12-month treatment period. The severity of preexisting extrapyramidal symptoms (EPS) in patients treated with risperidone decreased significantly from baseline to endpoint (p<0.001), and the use of antiparkinsonian medication decreased from 41.1% of patients before the trial to 25.6% during the trial. There were no spontaneous reports of tardive dyskinesia (TD) and the incidence of assessed TD was 4.3% in contrast to the expected 26% reported in middle-aged and elderly patients receiving conventional antipsychotic agents for 1 year. CONCLUSIONS: Long-term treatment with risperidone was associated with continued symptom improvement, a decrease in the severity of preexising EPS, and a low incidence of TD in elderly psychotic patients.

Adult↗
PubMed2000

Enterostatin suppresses food intake in rats after near-celiac and intracarotid arterial injection.

Enterostatin (Ent) selectively suppresses the intake of dietary fat after peripheral and central administration. To further investigate the site of action of Ent, we compared the feeding responses to Ent injected intra-arterially near the celiac artery, into the carotid artery, or intravenously in rats adapted to a high-fat diet. After near-celiac arterial injection there was an immediate dose-dependent (0.05-13.5 nmol) inhibition of food intake occurring within 5 min in overnight-fasted rats that lasted up to 20 min. Carotid arterial Ent had a similar, immediate dose-related response, and the inhibitory effect was long lasting. The response to intravenous Ent was only evident at the highest dose (13.5 nmol) and was delayed for at least 120 min. Pretreatment with capsaicin, which causes degeneration of vagal sensory neurons, abolished the inhibitory responses to near-celiac Ent but not to intravenous or intracarotid Ent. These results provide further evidence for both a gastrointestinal site of action for peripheral Ent and a central site of action for intracarotid Ent and suggest that the delayed response to intravenous Ent may reflect either binding or slow uptake of this peptide into the central nervous system.

Animals↗
PubMed1999

Pharmacokinetics of recombinant factor VIII (recombinate) using one-stage clotting and chromogenic factor VIII assay.

In a study designed to demonstrate the safety and pharmacokinetics of a recombinant factor VIII (Recombinate) manufactured in Andover, MA and Thousand Oaks, CA, two different methods of factor VIII assay (one-stage clotting and Chromogenic substrate) were compared in vivo. The study was performed in four centres in the UK: London, Oxford, Cardiff and Manchester. Two pharmacokinetic studies, at least one week apart, were performed in 30 patients with severe haemophilia A (VIII:C < 2 IU/dl). A dose of 50 IU/kg was administered with sampling pre-infusion, and +0.25, 0.5, 1, 3, 6, 9, 12 and 24 h post-infusion. The aggregate 60 pharmacokinetic study showed a half-life of 12.7 and 13.0 h (p = 0.28) and recovery of 127 and 161 IU/dl (p = 0.0001) using one-stage clotting or chromogenic substrate respectively. In a supplementary experiment, 20 post-infusion samples were re-assayed by 1-stage and chromogenic assay using two plasma (20th British plasma standard and an "in-house" pooled normal plasma) and two concentrate standards, derived from the same type, but different batch of infused concentrate (Recombinate) and pre-diluted in either individual pre-infusion sample or in pooled commercial haemophilic plasma. The use of the Recombinate concentrate standard overcame the significant difference in FVIII levels between 1-stage and chromogenic assay methods when a plasma standard was used (p <0.0001). It is concluded that where potency dosing designation is carried out by an assay system different to that used in the clinical situation, the use of the recombinant concentrate as a standard in post-infusion plasma samples is likely to give more reliable and reproducible results.

Biological Assay↗
PubMed1998

Measurement of active coagulation factors in Autoplex-T with colorimetric active site-specific assay technology.

Autoplex-T is a partially activated prothrombin complex concentrate used primarily for the treatment of patients expressing factor VIII inhibitors. While Autoplex-T has a demonstrated record of clinical effectiveness, the procoagulant composition of this material has not been reported. This absence of composition data is a reflection of the lack of techniques appropriate for accurately measuring an individual protease such as factor IXa in complex mixtures of similar proteases. The development of Colorimetric Active Site-Specific ImmunoAssay technology (CASSIA) has permitted the accurate analysis of the coagulant enzymes present in Autoplex-T. Ten lots of Autoplex-T were reacted with both biotinylated phenylalanylprolylarginine chloromethylketone and biotinylated glutamylglycylarginine chloromethylketone. Only activated forms of the clotting factors present in Autoplex-T react with the peptide chloromethylketones and were thus separated from the other proteins present in Autoplex-T by adsorption onto streptavidin. The individual proteins bound to streptavidin were then detected with specific antibodies. Mean results from the analysis of ten lots of Autoplex-T (mean values) are as follows: factor Xla, 5.9 nM or 0.8 microg/ml; factor Xa, 46.5 nM or 2.1 microg/ml; factor IXa, 177.8 nM or 11.7 microg/ml; factor VIIa, 68.6 nM or 3.3 microg/ml and factor IIa, 5.3 nM or 0.2 microg/ml. These results are discussed with respect to the mechanism of action of Autoplex-T in the treatment of factor VIII inhibitor patients.

Amino Acid Chloromethyl Ketones↗
PubMed1997

The inhibitor antibody response is more complex in hemophilia A patients than in most nonhemophiliacs with factor VIII autoantibodies. Recombinate and Kogenate Study Groups.

Approximately 25% of hemophilia A patients infused with factor VIII (fVIII) mount an immune response, which leads to its inactivation. Anti-fVIII autoantibodies are also seen rarely in individuals with normal fVIII. We have previously demonstrated that some anti-A2 and anti-C2 domain antibodies are fVIII inhibitors and that many patients have additional inhibitors with a fVIII light chain (LCh) epitope outside C2. Because the contribution of the different antibodies to the plasma inhibitor titer had been examined in a limited number of patients (14), we report in this study a more extensive analysis of 55 plasmas. The dominant inhibitors in 62% (13 of 21) of autoantibody plasmas were directed only against C2 or A2, but not both, whereas this pattern was found in only 15% (5 of 34) of hemophilic plasmas. In addition, anti-A2 inhibitors were present in 71% (24 of 34) of hemophilic plasmas, but only 33% (7 of 21) of autoantibody plasmas. These results demonstrated that the inhibitor response in hemophiliacs was more complex and the epitope specificity was somewhat different. A comparison of hemophiliacs treated only with plasma fVIII or recombinant fVIII showed no significant differences in the complexity of the inhibitor response, as > or = 2 different inhibitor antibodies were present in 78% (18 of 23) of the former and 82% (9 of 11) of the latter. In contrast, the major inhibitors in 35% (8 of 23) of hemophiliacs treated with plasma fVIII were directed against C2 and another LCh epitope within residues 1649-2137, but not A2, while none (0 of 11) treated with recombinant fVIII had this pattern.

Antibody Specificity↗
PubMed1997

Genetics of human obesity: research directions.

Rapid strides in understanding the physiology controlling energy or nutrient intake and energy expenditure have complemented the search for the genetic basis of obesity. Several single gene defects are known that produce obesity in animals. All of these have been cloned within the past 4 years, providing a rich new base for understanding obesity. Since obesity is likely to be "multifactorial," a number of laboratories have used the quantitative trait locus (QTL) technique of genome scanning to identify candidate genomic regions and, eventually, genes that may influence body weight and body fat. So far, 18 QTLs have been identified in association with crossbreeding strains of mice or rats with variable susceptibility to obesity. A number of mendelian disorders are known to exist in humans, but no specific genes have yet been identified for them. The potential for inserting new genetic material into mammals has produced numerous transgenic mice with increased or decreased quantities of body fat. These models will provide a continuing source of new insights into obesity. Several areas in the human genome have been linked to the development of obesity. Among the candidate genes with evidence of linkage to body fat are TNF-alpha, adenosine deaminase, and melanocortin-3 receptor. The new insights described above have invigorated the pharmaceutical industry to increase their efforts for new drug development aimed at the growing problem of obesity.

Adipose Tissue↗
PubMed1996

Anaphylaxis after treatment with recombinant factor VIII.

BACKGROUND: Treatment of hemophilia patients with recombinant factor VIII concentrates has not previously been associated with anaphylaxis. STUDY DESIGN AND METHODS: A 5-week-old boy with severe hemophilia A developed dyspnea, cyanosis, hypotension, and a diffuse urticarial rash following treatment with a recombinant factor VIII (Recombinate). To identify the cause of anaphylaxis in this patient, the vial lot was examined for the presence of endotoxin, and a checkerboard immunoblotting technique was used to test serum and/or plasma samples from the patient and mother for the presence of antibodies (IgA, IgG, IgE, and IgM) to Recombinate-related antigens (recombinant factor VIII, von Willebrand factor, human serum albumin, Chinese hamster ovary proteins, bovine serum albumin, mouse monoclonal anti-human factor VIII, polyethylene glycol 3350), and to ethylene oxide, the agent used to sterilize the infusion equipment. RESULTS: No immune response directed against the Recombinate-related antigens or ethylene oxide that could be associated with the anaphylactic reaction was identified. Endotoxin was not present upon rabbit pyrogen testing of the therapeutic product. CONCLUSION: These studies failed to show any association between Recombinate and the onset of the allergic reaction. This seems to be the first reported case of anaphylaxis following the infusion of a recombinant form of factor VIII concentrate.

Anaphylaxis↗
PubMed1996

Pharmacokinetic in vivo comparison using 1-stage and chromogenic substrate assays with two formulations of Hemofil-M.

In a study to demonstrate the safety and pharmacokinetics (half-life and recovery) of two different method M purified AHF (Hemofil-M) concentrates processed in the USA and Spain, two different methods of factor VIII assay (one-stage clotting and chromogenic) have been compared in vivo. The study was a single centre blinded, randomised, crossover study. Twelve patients with severe haemophilia A (VIII:C < 2 u/dl) were divided into two subgroups of six. None had received factor VIII concentrate within 48 h preceding the study. Twenty-four pharmacokinetic studies were performed in the 12 patients. Each subgroup received two different lots of study material (US and Spanish) at a dose of 50 u/kg seven days apart. A second randomisation was nominal potency, high: 1000 u or mid: 500 u per vial. The potency label was a one-stage clotting assay using the mega I standard. A standard pharmacokinetic study was performed over 24 h and each blinded sample was analysed in duplicate by a one-stage clotting (aPTT) and a chromogenic (Chromogenix AB; CS) assay at the Royal Free and NIBSC. Pharmacokinetic modelling was performed. The mean label for Hemofil-M using the chromogenic substrate assay was 79% that using the one stage assay (Mega I standard). The recovery was 17-28% higher measured by chromogenic compared to the clotting assay. Since most clinicians use the clotting assay, potency labelling using the chromogenic assay, will overestimate predicted Hemofil-M recovery by as much as 25%.

Biological Assay↗
PubMed1994

Comparison of oxygenation measurements in pediatric patients during sickle cell crises.

Measurements of the saturation of arterial blood with oxygen (SaO2) were compared in 24 children during sickle cell crises. Simultaneous pulse oximetry (Nellcor N-100 pulse oximeter) and arterial blood analysis showed that SaO2 measured by pulse oximetry overestimated cooximeter-measured SaO2 (mean bias, 6.9%; p < 0.001). The blood gas machine-calculated SaO2 also overestimated cooximeter-measured SaO2 (p < 0.001). The bias increased with increasing age (p = 0.002) and carboxyhemoglobin level (p = 0.005) but was not related to methemoglobin, total hemoglobin, percentage of hemoglobin S, or percentage of hemoglobin F.

Adolescent↗
PubMed1993

Comparison of serum procollagen III peptide concentrations and PGA index for assessment of hepatic fibrosis.

In early hepatic fibrosis, increased amounts of type III collagen are deposited. Persistently high serum concentrations of aminoterminal type III procollagen propeptide (PIIIP) correlate with the activity of the fibrogenic process. Another index for the detection of fibrosis, the PGA index, combines the prothrombin time, gamma-glutamyl transpeptidase activity, and serum apolipoprotein A1 concentration (the latter falls with progressive fibrosis). We compared PIIIP measurements and PGA index in patients with various histological forms of alcoholic liver disease (104), primary biliary cirrhosis (38), and chronic B virus hepatitis (27), and in healthy age-matched controls (30). The ability of each test to identify correctly patients with fibrosis or cirrhosis was assessed with receiver operating curves. The PGA index was much higher in all groups of patients with alcoholic liver disease than in controls (p < 0.0001). PIIIP concentrations were also substantially higher than in controls (p < 0.05 for fatty liver, p < 0.0001 for all other groups), especially in the group with alcoholic hepatitis and cirrhosis. For the detection of cirrhosis the PGA was 91% sensitive and 81% specific and the PIIIP concentration was 94% sensitive and 81% specific. The two tests combined had 85% sensitivity, but 93% specificity. Among patients with primary biliary cirrhosis, both PGA index and PIIIP concentration correlated well with the severity of the disease, determined by the Mayo score (r = 0.72 and 0.66 respectively). The combined tests were 96% sensitive for the detection of fibrosis. All patients with chronic B virus hepatitis had raised PGA and PIIIP values in comparison with controls (p < 0.0001) but there were no differences between subgroups. Substantially raised PIIIP concentrations thus identify the subgroup of alcoholic patients with both hepatitis and cirrhosis. The combination of PGA index and PIIIP concentration may be useful for targeting treatment with antifibrotic drugs and to reduce the need for liver biopsy.

Apolipoprotein A-I↗
PubMed1993

Three-year randomised study of high-purity or intermediate-purity factor VIII concentrates in symptom-free HIV-seropositive haemophiliacs: effects on immune status.

The availability of monoclonal-antibody-purified factor VIII (FVIII) concentrates allows us to test the hypothesis, based on in vitro observations, that their use in HIV seropositive haemophiliacs would result in a difference in the rate of deterioration of immune function. We designed a multicentre, prospective, randomised, controlled study of symptom-free HIV-infected patients with haemophilia A who were assigned to receive either an intermediate-purity or monoclonal-antibody-purified product. All had CD4 lymphocyte counts of 100-600/microL, were negative for hepatitis B surface antigen, had not received any antiretroviral or immunomodulating drugs before study entry, and had previously received replacement therapy with intermediate purity FVIII concentrates. Use of antiretroviral therapy was permitted. 60 patients were recruited and 30 were assigned to each group. 35 completed the 3 year study, 20 in the monoclonal arm and 15 in the intermediate-purity arm. Among those completing the study, there were no differences between the two groups in the occurrence of AIDS-defining diagnoses (1 in each group). There were, however, striking and significant differences in terms of changes in absolute CD4 counts. The group receiving monoclonal-antibody-purified concentrates had essentially stable counts while a significant drop was observed in the group receiving intermediate-purity FVIII. These differences were independent of the use of antiretroviral therapy. These observations support the use of high-purity concentrates in the treatment of symptom-free HIV-positive patients with haemophilia A, and they should be taken into account along with cost, by doctors making therapeutic decisions.

Adolescent↗
PubMed1992

Susceptibility to primary biliary cirrhosis is associated with the HLA-DR8-DQB1*0402 haplotype.

In studies to date seeking associations between human leukocyte antigens (HLA) and primary biliary cirrhosis, no class I association but several different class II associations have been described. The aims of this study were to reassess the DR associations in primary biliary cirrhosis and to examine for the first time the role of DQB. DRB genotypes were determined on standard Taq1 restriction-fragment-length polymorphism analysis in 159 white northern European patients with the disease and 162 racially matched local controls. Polymerase chain reaction gene amplification and sequence-specific oligonucleotide analysis were used to determine DQB genotypes in 89 patients and 181 controls. An increased frequency of human leukocyte antigen DR8 was observed in the patient group (11% vs 4%; relative risk = 3.3; p < 0.01). Although we saw an increased frequency of the DQB1*0402 allele (11% vs. 3%; relative risk = 3.5; p < 0.025), this was not significant after correction for multiple testing. The strongest association was with the two-locus haplotype DR8-DQB1*0402 (11% vs. 2.2%; relative risk 5.5; p < 0.001). The DRB data reported here confirm the findings of previous studies, although the described association with DR8 is considerably weaker. The weak genetic contribution of human leukocyte antigen in the susceptibility to primary biliary cirrhosis is in contrast to its role in other autoimmune liver diseases.

Adult↗