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Biomedical subjects

P A Elder

Publications and source records attributed to P A Elder.

At least 19 recordsLinked to original sources
PubMed2006

Plasma variation of corticosteroid-binding globulin and sex hormone-binding globulin.

Sex hormone-binding globulin (SHBG) and corticosteroid-binding globulin (CBG) circulate in plasma and bind their cognate ligands with high affinity, offering a steroid delivery system to target tissues by a variety of mechanisms. Analysis of these steroid-binding proteins is gaining importance in the clinical setting, although more information is warranted on their diurnal and biological variation. This study shows that plasma SHBG (in normal subjects) exhibits little diurnal or biological variation over the 30 day period studied, in contrast to CBG, where plasma levels peak in the early afternoon. This leads to attenuation of the diurnal free cortisol level rhythm compared to total cortisol. We also show that plasma CBG is significantly lower in male subjects with the metabolic syndrome compared to age-matched lean counterparts, and may therefore act as a surrogate marker of insulin resistance. The consequence of lower levels of CBG in these obese male subjects is reflected by higher levels of circulating free cortisol, potentially offering a more favourable environment for adipogenesis.

Adult↗
PubMed2005

Circulating levels of isoflavones and markers of 5alpha-reductase activity are higher in Japanese compared with New Zealand males: what is the role of circulating steroids in prostate disease?

Epidemiological evidence implicates dietary isoflavone intake as protective against prostate disease. A putative mechanism is attenuated circulating androgen levels in male populations consuming an isoflavone rich diet. We investigated this hypothesis by collecting plasma from 60 Japanese and 60 New Zealand males aged between 21 and 31 years each consuming their traditional diets. We measured plasma testosterone, dihydrotestosterone (DHT), androstenedione, dehydroepiandrosterone sulfate (DHEAS), the combined levels of androsterone sulfate and epiandrosterone sulfate (AoS/epiAoS), sex hormone-binding globulin, and cortisol and corticosteroid-binding globulin as well as the isoflavones genistein and equol. Plasma genistein and equol levels were several times higher in Japanese males as would be expected from an isoflavone rich diet. However, androstenedione, DHEAS, calculated free testosterone and paradoxically markers of 5alpha-reductase, DHT and AoS/epiAoS were all also significantly higher in Japanese rather than the New Zealand male counterparts. All other comparisons were not significant. Plasma DHT and DHEAS correlated positively with plasma equol and plasma AoS/epiAoS correlated positively with genistein levels. Taken together the results suggest that, rather than reduced levels of steroidogenesis, Japanese males may have increased 5alpha-reductase activity and possibly altered 17beta OH steroid dehydrogenase activity. Significantly the positive association between isoflavones levels and 5alpha-steroids is counter-intuitive to isoflavone intake offering prostate protection, unless this is postulated to occur through other mechanisms.

Adult↗
PubMed2004

Plasma sex hormone-binding globulin rather than corticosteroid-binding globulin is a marker of insulin resistance in obese adult males.

AIM: Plasma levels of corticosteroid-binding globulin (CBG) and sex hormone-binding globulin (SHBG) may be regulated by insulin. The aim of this study was to test the hypothesis that these steroid-binding proteins are markers of insulin resistance and obesity in adult patients with the metabolic syndrome. METHODS: Fasting blood samples were obtained from 108 male and 88 female overweight adult patients who had varying degrees of dyslipidaemia, adiposity and insulin resistance. We measured plasma levels of SHBG and CBG and investigated their correlation with insulin resistance [homeostasis model assessment (HOMA) % sensitivity] and anthropometric markers of adiposity. RESULTS: In male patients, plasma SHBG correlated positively with HOMA (% sensitivity) and negatively with anthropometric measurements, including body mass index, waist circumference (cm) and percentage body fat. There was no correlation with CBG and any other parameter in the male patients. The female patients were treated as two groups, those not using oral contraceptives or hormone replacement therapy (n = 67) and those taking steroid medications (n = 21). Female patients using steroid medications had significantly higher SHBG levels but neither group showed any correlation between SHBG, insulin resistance and adiposity. Correlation studies of CBG with other parameters in the female subgroups did not reach statistical significance. CONCLUSIONS: We conclude that plasma SHBG is another surrogate marker for insulin resistance in obese males but not in obese females. It also appears that plasma CBG is not a useful marker of insulin resistance in patients with the metabolic syndrome.

Biomarkers↗
PubMed2003

Plasma adiponectin in overweight, nondiabetic individuals with or without insulin resistance.

AIM: Adiponectin is a protein produced exclusively by adipocytes with putative insulin-sensitizing and anti-atherogenic properties. This cross-sectional study investigated the relationship between plasma adiponectin and a range of anthropometric, glycaemic, lipid and inflammatory parameters in overweight and obese subjects expressing characteristics of the metabolic syndrome. METHODS: Subjects were selected for the study from a clinical database, if they were non-diabetic, overweight [body mass index (BMI) > 25] and had features of the metabolic syndrome. The subjects were grouped according to BMI (25-30, 31-35 and >35 kg/m2) and then stratified for insulin resistance [homeostasis model assessment (HOMA) %S]. One hundred and ninety-seven patients (109 males and 88 females) were selected for the study by taking an equal number with the highest and lowest HOMA indices from each of the three BMI groups. Plasma adiponectin concentration was measured in duplicate by radioimmunoassay, and the relationship between these levels and the other parameters was investigated using correlation and multiple linear regression analyses. RESULTS: Plasma adiponectin concentration was higher in females than males (median 10.3 vs. 7.1 micro g/ml, p < 0.001) despite being matched for BMI. In both genders, adiponectin levels were inversely related to BMI, waist circumference, percentage body fat, insulin resistance and the fasting plasma concentration of leptin. A direct correlation in both sexes was found between adiponectin levels and high-density lipoprotein (HDL)-cholesterol, apolipoprotein A1 and age. Multiple linear regression analyses showed that the independent determinants of low plasma adiponectin concentrations were gender, age, BMI, insulin resistance and HDL-cholesterol. An association between reduced adiponectin and increased high-sensitivity plasma C-reactive protein concentration was observed only in female subjects and was independent of anthropometric variables. Our observation that adiponectin levels increase with age differs from the majority of other studies and may simply reflect the demographics of the population studied. CONCLUSIONS: This study shows that adiponectin is an important molecular link between obesity, insulin resistance and atherogenic lipoproteins. It is possible that plasma adiponectin concentration may be a convenient marker for identifying subjects with the metabolic syndrome who may progress to impaired glucose tolerance. Longitudinal studies are required in order to verify this clinical application of adiponectin.

Adiponectin↗
PubMed1999

Partial allelotype of schistosomiasis-associated bladder cancer.

In Egypt and other regions of the Middle East where the trematode Schistosoma haematobium is endemic, bladder cancer is the most common adult cancer. Unlike bladder cancers in Western countries, which are predominantly transitional-cell carcinoma (TCC), these schistosomiasis-associated bladder cancers are predominantly squamous-cell carcinoma (SCC). Our aim was to assess a large series of schistosomiasis-associated bladder tumours for genetic alterations commonly found in TCC in the United Kingdom and the United States. We have carried out a partial allelotype of 70 tumours from patients with schistosomiasis. LOH was found on all chromosome arms studied (3p, 4p, 4q, 8p, 9p, 9q, 11p, 11q, 13q, 14q, 17p, 18q). The most frequent regions of LOH were 9p (65%), 17p (58%), 3p (40%), 9q (39%) and 8p (37%). LOH on 17p, where the TP53 gene is located, was more common in Egyptian TCC than in SCC. Similarly, 8p LOH was more common in TCC than SCC. The most striking difference between this group of tumours and TCCs from the United Kingdom and the United States was the high frequency of 9p LOH in the region of the CDKN2 gene (65%) and the relatively low frequency of 9q LOH (39%); 15 of 43 tumours with LOH of at least one marker on chromosome 9 showed LOH of 9p only. This suggests that a 9p gene, possibly CDKN2, may contribute to the development of the majority of schistosomiasis-associated bladder tumours but that genes on 9q play a much less important role.

Adenocarcinoma↗
PubMed1999

Monoclonal antibodies to human sex hormone-binding globulin (SHBG): characterization and use in a simple enzyme-linked immunosorbent assay (ELISA) of SHBG in plasma.

Four monoclonal antibodies to human sex hormone-binding globulin were raised and characterized. Three of the four antibodies recognised different antigenic determinants on SHBG. Two of the distinct antibodies were useful for Western blotting and recognized a major 48 kDa band in human plasma as well as a 46 kDa minor component. Carbohydrate residues do not form part of the antigenic determinants of these two antibodies, although one of these showed increased signal following removal of N-linked oligosaccharides. Some of the antibodies were selected to form a basis of a same-day, non-competitive, enzyme-linked immunosorbent assay (ELISA) for SHBG in plasma. The assay employs a purified IgG2a SHBG monoclonal antibody adsorbed to the wells of a microtitre plate. After blocking any further adsorption to the plate, standards or diluted patient samples were added for a 5-h incubation at room temperature, after which the plate was washed and antibody-bound SHBG was detected with an anti-SHBG IgG1 monoclonal antibody followed by peroxidase-labeled antimouse-IgG1 and o-phenylenediamine substrate. The assay correlated well with an existing 2-day ELISA for SHBG in plasma using polyclonal antibodies and also correlated with a dihydrosterone (DHT) ligand-binding assay. The monoclonal antibody-based ELISA shows excellent performance characteristics and is unaffected by added testosterone or estradiol.

Adult↗
PubMed1998

Structure and methylation-based silencing of a gene (DBCCR1) within a candidate bladder cancer tumor suppressor region at 9q32-q33.

Loss of heterozygosity (LOH) on chromosome 9q is the most frequent genetic alteration in transitional cell carcinoma (TCC) of the bladder, indicating the presence of one or more relevant tumor suppressor genes. We previously mapped one of these putative tumor suppressor loci to 9q32-q33 and localized the candidate region within a single YAC 840 kb in size. This locus has been designated DBC1 (for deleted in bladder cancer gene 1). We have identified a novel gene, DBCCR1, in this candidate region by searching for expressed sequence tags (ESTs) that map to YACs spanning the region. Database searching using the entire DBCCR1 cDNA sequence identified several human ESTs and a few homologous mouse. ESTs. However, the predicted 761-amino-acid sequence had no significant homology to known protein sequences. Mutation analysis of the coding region and Southern blot analysis detected neither somatic mutations nor gross genetic alterations in primary TCCs. Although DBCCR1 was expressed in multiple normal human tissues including urothelium, mRNA expression was absent in 5 of 10 (50%) bladder cancer cell lines. Methylation analysis of the CpG island at the 5' region of the gene and the induction of de novo expression by a demethylating agent indicated that this island might be a frequent target for hypermethylation and that hypermethylation-based silencing of the gene occurs in TCC. These findings make DBCCR1 a good candidate for DBC1.

Amino Acid Sequence↗
PubMed1996

Production and characterization of monoclonal antibodies to dehydroepiandrosterone sulfate: application to direct enzyme-linked immunosorbent assays of dehydroepiandrosterone sulfate and androsterone/epiandrosterone sulfates in plasma.

Mice were immunized with 5-androstene-3 beta-ol-7,17-dione-7-CMO:bovine serum albumin (DHEA-7-O-CMO-BSA) or 5-androstene-3 beta-ol-17-one hemisuccinate-bovine serum albumin (DHEA-3HS-BSA) conjugates and monoclonal antibodies were produced, characterized, and selected for maximum DHEAS binding. Of these hybridomas, four clones from DHEA-3HS-BSA-immunized mice had acceptable criteria for the development of a competitive enzyme-linked immunosorbent assay (ELISA) for DHEAS in plasma. One hybridoma supernatant from DHEA-7-O-CMO-BSA-immunized mice showed 360% cross-reactivity to both androsterone sulfate and epiandrosterone sulfate. This allows the possibility of the direct determination of androsterone sulfate and epiandrosterone sulfate in plasma after correction for the DHEAS contribution. Both ELISAs employ a DHEA-3HS-thyroglobulin conjugate adsorbed to the wells of a standard 96-well microtiter plate. DHEAS in the standards or diluted plasma sample competes with immobilized DHEA-3HS-thyroglobulin for antibody-binding sites. Antibody is detected with anti-mouse-lg peroxidase by further washing, adding o-phenylenediamine substrate, and reading the absorbance at 492 nm. The ELISAs are simple, reproducible, and reliable and, to our knowledge, they are the first tests employing monoclonal antibodies to DHEAS.

Adult↗
PubMed1996

High frequency of chromosome 9 deletion in ovarian cancer: evidence for three tumour-suppressor loci.

We have screened 33 ovarian tumours of various grades and stages for the loss of heterozygosity (LOH) of markers on chromosome 9. LOH was detected in 26 cases (79%). Eleven tumours (33%) showed LOH of all informative markers. The remaining 15 cases had partial deletions. Of these, six (18%) had losses on 9p only, three (9%) had LOH confined to 9q and six (18%) had losses on both chromosome arms, four of which had a retention of hetereozygosity in between. There was no association between tumour grade stage or histopathology and any losses. High-density deletion mapping was carried out in 12 selected cases that had partial deletions of 9p and/or 9q. The deleted region on 9p included the cyclin-dependent kinase inhibitor 2 (CDKN2) locus and one tumour was found to have a homozygous deletion of CDKN2. LOH on 9q extended over a larger region. We found evidence for two regions of deletion on 9q, one at 9q34 and the other encompassing the nevoid basal cell carcinoma (Gorlin) syndrome locus on proximal 9q.

Adenocarcinoma↗
PubMed1995

Detailed deletion mapping of chromosome 9q in bladder cancer: evidence for two tumour suppressor loci.

Loss of heterozygosity (LOH) at loci on chromosome 9p and/or 9q is the most frequent genetic alteration in transitional cell carcinoma (TCC) of the bladder. However, localisation of the tumour suppressor locus or loci on 9q has been hampered by the relative infrequency of tumours with subchromosomal deletions. We have used 24 microsatellite markers to examine LOH in 70 new cases of TCC of the bladder and upper urinary tract. Forty tumours (57%) showed LOH at one or more loci on 9q and partial deletions were detected in five tumours (7%). Combined data from the five cases with partial deletions place one tumour suppressor locus at 9q34 between D9S61 and D9S66 (an estimated distance of 13-14 cM). This region is frequently deleted in other sporadic tumours and encompasses one of the loci for tuberous sclerosis (TSC1). One tumour contained a distinct deletion between D9S153 and D9S109 (9q13-q31), which encompasses the locus for the familial nevoid basal cell carcinoma syndrome (Gorlin syndrome). This may indicate the presence of another tumour suppressor locus on 9q for TCC. Our findings significantly reduce the regions of 9q within which suppressor genes for TCC may reside. The possible involvement of two deletion targets on 9q in addition to the locus at 9p21 implicated in TCC may explain why LOH at all loci on chromosome 9 is frequent in TCC.

Chromosome Mapping↗
PubMed1995

p16 (CDKN2) is a major deletion target at 9p21 in bladder cancer.

The p16 gene has been identified as a candidate tumour suppressor gene at 9p21, a region commonly deleted in bladder cancer. We screened 140 bladder tumours and 16 cell lines for deletions and sequence variants of p16. Eight cell lines showed homozygous deletion of p16 and two had small sequence variations. All 13 tumours with small defined deletions of 9p21, 18/31 (58%) of tumours with monosomy 9 and 9/91 (10%) of tumours with no chromosome 9 loss of heterozygosity had homozygous deletion of p16. No tumour-specific sequence variants were identified. Deletion mapping revealed a nested set of deletions focused on p16. Six deletions involved p16 but not the related and adjacent gene p15 and one tumour had an intragenic deletion of p16. All other deletions involved both p16 and p15. We conclude that p16 represents the major target for deletion at 9p21 in bladder cancer.

Base Sequence↗
PubMed1994

Allelotype of human bladder cancer.

To identify common regions of deletion in human bladder tumors, we have screened 83 cases of transitional cell carcinoma for loss of heterozygosity (LOH) on all autosomal chromosome arms. Seventy-two restriction fragment length polymorphism, variable number of tandem repeats, and minisatellite markers and 18 microsatellite markers were used to obtain a minimum of 50% informative results for each chromosome arm. A mean of 29.6 informative results per patient was obtained from 39 chromosome arms studied, representing information for 76% of chromosome arms. The most frequent losses were apparent monosomies of chromosome 9 (9p, 51%; 9q, 57%). Other frequent losses were on chromosomes 11p (32%), 17p (32%), 8p (23%), 4p (22%), and 13q (15%). LOH of 4p has not been reported previously in bladder carcinoma. The frequency of LOH on all other chromosome arms was < 12%. LOH on chromosome 8p showed a significant association with both high tumor grade and stage, and LOH on 13q showed a significant association with high tumor grade. Fractional allelic loss was calculated for all tumors and had a mean of 0.125 and a median of 0.110. A significant association was found between increased fractional allelic loss and higher tumor grade. An association was also found between LOH of chromosomes 8p and 9q and values for fractional allelic loss > or = the median value. No associations were found between LOH on different pairs of chromosome arms.

Alleles↗
PubMed1994

The spectrum of TP53 mutations in bladder carcinoma.

The mutational spectrum for the TP53 gene was investigated in a large series of bladder tumors and bladder tumor cell lines. Tumors and cell lines were screened for the presence of TP53 point mutations by single-strand conformational polymorphism analysis followed by direct sequencing. Mutations were detected in 16 of 88 (18%) tumors and 4 of 14 cell lines (28%). In total, twelve missense mutations, one nonsense mutation, three deletions, and two insertions were identified by direct sequencing. Of the thirteen point mutations sequenced, only one was a transition at a CpG site, whereas five G:C-->T:A transversions were found, suggesting a major role for exogenous mutagens in bladder tumorigenesis. Tumors were also examined for loss of heterozygosity (LOH) on chromosome arm 17p. LOH of one or more markers on 17p was detected in 31% of tumors. All eight tumors with a TP53 mutation from patients informative at TP53 had LOH, whereas nine tumors with LOH at TP53 did not have an identified mutation. Three tumors had LOH on 17p at sites distal to the TP53 locus but retained both TP53 alleles, suggesting the involvement of another tumor suppressor gene on 17p in bladder tumorigenesis in some tumors.

Alleles↗
PubMed1994

Re-examining steroid hormone metabolites as ovulation markers using monoclonal antibodies.

Plasma progesterone and plasma estradiol levels are commonly used to monitor ovulation in women although for the adequate documentation of ovulation the expense and discomfort of multiple venipuncture sampling may be required. Accurate and definitive information on ovulation in women can be obtained by the simple measurement of metabolites of progesterone and estradiol in early morning urine samples. These analyses have been made possible by the use of our own highly specific monoclonal antibodies to both pregnanediol-3-glucuronide (P-3-G) and estrone-3-glucuronide (E-3-G) and the development of simple, direct, automated enzyme-linked immunosorbent assays. Sequential sampling and the generation of ovulation profiles allows detection of ovulation and identification of the infertile/fertile phases of the cycle for either planned pregnancies or natural family planning. Aberrations in ovulation are easily detected as is documentation of the transition to menopause. The use of sequential, spaced, early morning urine samples for P-3-G and E-3-G allows accurate assessment of ovulatory function rather than relying on the usual single plasma sampling. The data presented also show that the direct determination of plasma pregnanediol-3-glucuronide in plasma is as informative as plasma progesterone measurement.

Adult↗