Fibrinogen, Factor VII and PAI-1 Genotypes and the Risk of Coronary and Peripheral Atherosclerosis: Edinburgh Artery Study

There are now many epidemiological studies that have shown a relationship between haemostatic factors and subsequent risk of both coronary and peripheral arterial disease. However, there is less information on the association between genetic variation in these factors and the risks of coronary and peripheral arterial disease. As part of the five-year follow-up of the Edinburgh Artery Study, polymorphisms of the fibrinogen (-455G/A), factor VII (R/Q353) and PAI-1 (HindIII) genes were measured in men and women aged 60-79 years, together with their plasma levels. Using widely accepted criteria, 88 subjects were identified as having peripheral arterial disease (PAD), 195 having coronary artery disease (CAD) and 423 subjects comprised a “healthy” group. The -455AA genotype of the fibrinogen gene was found to be more frequent among those subjects with PAD. This genotype also showed the highest plasma fibrinogen levels in both disease groups and in the healthy group. Using logistic regression, after adjustment for age, sex, smoking and plasma level, the -455AA genotype was associated with over twice the risk of PAD compared with the -455GG genotype, the odds ratio reaching marginal significance (p″0.10). Combining those with genotype -455AA with the heterozygotes in order to increase the power of the study resulted in a more significant multiple-adjusted risk of PAD (p″0.05). These data provide evidence that a polymorphism of the β fibrinogen gene is associated with an increased risk of peripheral atherosclerosis.

Effects of supplementation and stocking rate on body condition and production parameters of multiparous beef cows

Fall-calving multiparous Angus × Hereford cows 3 to 10 years of age were stratified by age in a three by two factorial treatment arrangement to evaluate the efficacy of modifying stocking rate and supplementation strategy to manage cow body condition and production parameters over a 5-year study. Efficacy was evaluated quarterly in association with calving, breeding, weaning, and mid way between weaning and calving (i.e. in August). Three protein supplementation strategies (none, standard, strategic) were imposed across both a moderate (0·3 cows per ha) and a high (0·4 cows per ha) stocking rate. In the strategically supplemented group, protein supplement was provided to cows with a body condition score <5·5 at the quarterly evaluations. There was an effect of supplementation on pregnancy rate, which in combination with previously established culling practices resulted in different age profiles amongst supplementation strategies in years 2 to 5 (P < 0·01). Two statistical analyses were therefore conducted to dissociate the confounding effects of supplementation strategy and age. One model included the effect of stocking rate, supplementation strategy, production year, and all interactions; the second included the addition of age and its interactive effects. Stocking rate and supplementation strategy affected pregnancy rate in each of the models (P = 0·003 and P = 0·10, respectively). Standard, non-supplemented and strategically supplemented animals had estimated pregnancy rates of 0·83, 0·76, and 0·79, respectively (P = 0·10). The effects of nutrition on both calving interval and birth weight were independent of the model employed. Animals that were not supplemented had extended calving intervals (P = 0·06), but there was no effect of stocking rate (P > 0·10). Birth weight was not affected by supplementation strategy or stocking rate (P > 0·10). The lower 205-day weights of calves on a heavy compared with moderate stocking rate was independent of age (P = 0·02). However, the increased 205-day weight of calves born to strategically supplemented cows compared with those born to unsupplemented cows was only evident when data were not corrected for differences in age among groups (P = 0·03). Likewise, analyses of cow condition parameters using models without and with age resulted in different interpretations. These results suggest that strategic and standard supplementation result in similar animal performance and that the improvement in herd productivity associated with altering stocking rate and supplementation may partially be due to altered herd age dynamics.

Confirmation of CHD7 as a cause of CHARGE association identified by mapping a balanced chromosome translocation in affected monozygotic twins

BACKGROUND

CHARGE syndrome has an estimated prevalence of 1/10,000. Most cases are sporadic which led to hypotheses of a non-genetic aetiology. However, there was also evidence for a genetic cause with reports of multiplex families with presumed autosomal dominant, possible autosomal recessive inheritance and concordant twin pairs. We identified a monozygotic twin pair with CHARGE syndrome and a de novo balanced chromosome rearrangement t(8;13)(q11.2;q22).

METHODS

Fluorescence in situ hybridisation was performed with BAC and PAC probes to characterise the translocation breakpoints. The breakpoint on chromosome 8 was further refined using 10 kb probes we designed and produced using sequence data for clone RP11 33I11, the Primer3 website, and a long range PCR kit.

RESULTS

BAC and PAC probe hybridisation redefined the breakpoints to 8q12.2 and 13q31.1. Probe RP11 33I11 spanned the breakpoint on chromosome 8. Using our 10 kb probes we demonstrated that the chromodomain gene CHD7 was disrupted by the translocation between exons 3 and 8.

DISCUSSION

Identifying that the translocation breakpoint in our patients occurred between exons 3 and 8 of CHD7 suggests that disruption of this gene is the cause of CHARGE syndrome in the twins and independently confirms the role of CHD7 in CHARGE syndrome.

Demystification of Chester porphyria: A nonsense mutation in the porphobilinogen deaminase gene

The porphyrias arise from predominantly inherited catalytic deficiencies of specific enzymes in heme biosynthesis. All genes encoding these enzymes have been cloned and several mutations underlying the different types of porphyrias have been reported. Traditionally, the diagnosis of porphyria is made on the basis of clinical symptoms, characteristic biochemical findings, and specific enzyme assays. In some cases however, these diagnostic tools reveal overlapping findings, indicating the existence of dual porphyrias with two enzymes of heme biosynthesis being deficient simultaneously. Recently, it was reported that the so-called Chester porphyria shows features of both variegate porphyria and acute intermittent porphyria. Linkage analysis revealed a novel chromosomal locus on chromosome 11 for the underlying genetic defect in this disease, suggesting that a gene that does not encode one of the enzymes of heme biosynthesis might be involved in the pathogenesis of the porphyrias. After excluding candidate genes within the linkage interval, we identified a nonsense mutation in the porphobilinogen deaminase gene on chromosome 11q23.3, which harbors the mutations causing acute intermittent porphyria, as the underlying genetic defect in Chester porphyria. However, we could not detect a mutation in the coding or the promotor region of the protoporphyrinogen oxidase gene that is mutated in variegate porphyria. Our results indicate that Chester porphyria is neither a dual porphyria, nor a separate type of porphyria, but rather a variant of acute intermittent porphyria. Further, our findings largely exclude the possibility that a hitherto unknown gene is involved in the pathogenesis of the porphyrias.

First-trimester combined ultrasound and biochemical screening for Down syndrome in routine clinical practice

OBJECTIVES

To assess the effectiveness of combined ultrasound and biochemical (CUB) screening for chromosome abnormalities in singleton pregnancies in a routine antenatal clinic and laboratory setting.

METHODS

Women whose pregnancies fell within the gestational age range of 11 to 14 weeks by ultrasound assessment were offered CUB screening on the basis of measurement of nuchal translucency (NT), maternal serum free beta-human chorionic gonadotrophin (FbetahCG) and pregnancy-associated plasma protein A (PAPP-A). NT measurements were obtained using a standardised method defined by the Fetal Medicine Foundation and FbetahCG, and PAPP-A were measured using the DELFIA immunoassay system. Each screening marker measurement was converted to a multiple of the appropriate gestational median and a risk was derived using previously published parameters for each marker in chromosomally abnormal and unaffected pregnancies. A combined risk of Down syndrome and of trisomy 18/13, incorporating the maternal age risk, was calculated for all women. Invasive diagnostic testing was offered to women whose combined risk exceeded the cut-off risk of 1 in 250 (term).

RESULTS

Five thousand and eighty-four women accepted a first-trimester screening test for Down syndrome, representing 75% of the eligible booking population. Out of the population eligible for CUB screening at the time of booking, NT measurements were obtained from 93% at the first clinic visit and 7% had to return for a second attempt. After excluding women who defaulted on a return visit, satisfactory NT measurements were obtained in 99.5% of pregnancies. Fifteen cases of Down syndrome and eleven pregnancies with other chromosome abnormalities were ascertained. The detection rate for Down syndrome was 93% (14/15) at a false-positive rate of 5.9% and for all chromosome abnormalities it was 96% (25/26) at an overall false-positive rate of 6.3%.

CONCLUSIONS

CUB screening offers a significant improvement in sensitivity over second-trimester biochemical screening and is deliverable within a routine prenatal clinical setting.

Fenceline contact of beef calves with their dams at weaning reduces the negative effects of separation on behavior and growth rate

The purpose of this study was to examine the hypothesis that fenceline contact between beef calves and cows at weaning reduces indices of behavioral distress and associated temporary reductions in weight gain. One hundred Angus/Hereford-cross calves were randomly assigned to five treatments for 7 d in each of 3 yr to determine the effect of different weaning techniques on their behavior and subsequent growth. Treatments were 1) fenceline separation from dams on pasture (F-P), 2) total separation from dams on pasture (S-P), 3) total separation from dams in a drylot (corral) preconditioned to hay (S-D-P), 4) total separation from dams in a drylot not preconditioned to hay (S-D-NP), and 5) nonweaned controls on pasture (C-P). At the end of the 7-d postweaning period, all calves were placed on pasture in large groups. Calves were weighed weekly for 10 wk. In the days following weaning, F-P and C-P calves spent more time eating (grazing or eating hay) than S-P and S-D-NP calves (P < 0.05). The S-P calves spent more time walking (pacing) than calves in the other four treatments (P < 0.05), which did not differ. The S-P calves also spent less time lying down than C-P, F-P, and S-D-P calves (P < 0.05); S-P and S-D-NP calves did not differ in lying time. The F-P calves vocalized less than S-P and S-D-NP calves (P < 0.05). In general, treatment differences were greatest during the first 3 d following weaning with d 2 (20 to 30 h after weaning) showing the greatest disparity. The F-P calves spent approximately 60% of their time within 3 m of the fence separating them from their dams during the first 2 d following weaning, whereas F-P cows spent about 40% of their time within 3 m of the fence during this period. Postweaning cumulative body weight gains of the F-P calves were greater than the gains recorded for the calves in the three totally separated treatments (which did not differ). The F-P calves gained 95% more weight than the average calf in the three totally separated treatments in the first 2 wk and were still heavier at 10 wk (21.4 vs 11.0 kg, respectively, at 2 wk and 50.0 vs 38.2 kg, respectively, at 10 wk; P < 0.05). It was concluded that providing fenceline contact between beef calves and cows for 7 d following weaning reduces behavioral indices of distress seen in the totally separated calves. In addition, fenceline contact with dams at weaning minimizes losses in weight gain in the days following separation. Totally separated calves did not compensate for these early losses in weight gain even after 10 wk.

Maternal smoking: age distribution, levels of alpha-fetoprotein and human chorionic gonadotrophin, and effect on detection of Down syndrome pregnancies in second-trimester screening

OBJECTIVES

To study the levels of maternal serum alpha-fetoprotein (AFP) and human chorionic gonadotrophin (hCG) in the second trimester in smokers and non-smokers with unaffected and Down syndrome pregnancies; to examine the rate of smoking in different maternal age groups in a population having routine prenatal screening; and to assess the effect of smoking on the detection rates for Down syndrome and corresponding false-positive rates, both overall and in different maternal age groups.

METHODS

Information on maternal smoking status, maternal age and serum marker levels was collected from case note searches and the screening programme database on 2272 unaffected singleton pregnancies, 36 unaffected twin pregnancies and 103 singleton Down syndrome pregnancies.

RESULTS

In unaffected pregnancies the smokers had a median age 3.3 years less than the non-smokers, while in the Down syndrome cases the corresponding age difference was 2.0 years. Median analyte levels in multiples of the median (MoM) in the unaffected singleton pregnancies were, for non-smokers: AFP=0.97, hCG=1.04; and for smokers, AFP=1.04, hCG=0.80. In the Down syndrome pregnancies the medians were, for non-smokers: AFP=0.69, hCG=2.49; and for smokers, AFP=0.70, hCG=1.53. Correction for smoking status gave median MoMs of 1.0 for both AFP and hCG in the unaffected pregnancies in both smokers and non-smokers. In the Down syndrome cases the corrected medians were, for non-smokers: AFP=0.67, hCG=2.29; and for smokers, AFP=0.73, hCG=1.99. Before correction for maternal smoking the overall detection rate for Down syndrome was 66.7% with a false-positive rate of 6.2%. After correction the detection rate was 67.7% with a false-positive rate of 4.9%. Between the smoking and non-smoking groups there was a significant difference in the detection rate (37.5% versus 76.0%) and the false-positive rate (1.8% versus 8.1%), which disappeared after correction for smoking status (detection rate 62.5% versus 69.3%, false-positive rate 3.9% versus 5.4%). No evidence of a lower incidence of Down syndrome in smokers was found.

CONCLUSIONS

While correcting AFP and hCG results for maternal smoking status will have little impact on the overall detection rate for Down syndrome, it may reduce the false-positive rate and will improve the accuracy of the risks given to individual women.

Placental and maternal serum inhibin-A and activin-A levels in Down's syndrome pregnancies

The objective of this study was to analyse the levels of inhibin-A and activin-A in maternal serum and placental tissue from Down's syndrome (DS) pregnancies. Inhibin-A and activin-A levels were determined by specific immunoassays and individual results were expressed as multiples of the control median (MoM) at the appropriate gestation. Immunohistochemistry was used to localize inhibin alpha and beta(A)-subunits in a selection of placental sections. In DS pregnancies, median inhibin-A levels were found to be significantly elevated to 1.46 MoM (P< 0.05) in placental extracts, and 2.06 MoM (P< 0.0001) in maternal serum, when compared with uncomplicated pregnancies. Median activin-A MoMs were also elevated in placental extracts and maternal serum to 1.62 MoM (P< 0.01), and 1.26 MoM (P< 0.05), respectively. Immunohistochemistry revealed that the alpha subunit of inhibin-A and the beta(A)subunit of inhibin-A and activin-A were mainly localized to the trophoblastic layer of placental villi. Semiquantitative studies of staining intensity revealed a trend towards stronger staining of placental trophoblasts and stroma of DS tissues, although this was statistically significant only for beta(A)subunit staining of trophoblasts (P< 0.05). These results support the hypothesis that maternal serum levels of inhibin-A and activin-A are elevated due to increased production in the placenta, and increased immunostaining of trophoblasts suggests that this may be due to increased production in the trophoblasts.

Linkage exclusion and mutational analysis of the noggin gene in patients with fibrodysplasia ossificans progressiva (FOP)

Fibrodysplasia ossificans progressiva (FOP) is an extremely rare and disabling genetic disorder characterized by congenital malformation of the great toes and by progressive heterotopic endochondral ossification in predictable anatomical patterns. Although elevated levels of bone morphogenetic protein 4 (BMP4) occur in lymphoblastoid cells and in lesional cells of patients with FOP, mutations have not been identified in the BMP4 gene, suggesting that the mutation in FOP may reside in a BMP4-interacting factor or in another component of the BMP4 pathway. A powerful antagonist of BMP4 is the secreted polypeptide noggin. A recent case report described a heterozygous 42-bp deletion in the protein-coding region of the noggin gene in a patient with FOP. In order to determine if noggin mutations are a widespread finding in FOP, we examined 31 families with 1 or more FOP patients. Linkage analysis with an array of highly polymorphic microsatellite markers closely linked to the noggin gene was performed in four classically-affected multigenerational FOP families and excluded linkage of the noggin locus to FOP (the multipoint lod score was -2 or less throughout the entire range of markers). We sequenced the noggin gene in affected members of all four families, as well as in 18 patients with sporadic FOP, and failed to detect any mutations. Single-strand conformation polymorphism (SSCP) analysis of 4 of these patients plus an additional 9 patients also failed to reveal any mutations. Among the samples analyzed by SSCP and DNA sequencing was an independently obtained DNA sample from the identical FOP patient previously described with the 42-bp noggin deletion; no mutation was detected. Examination of the DNA sequences of 20 cloned noggin PCR products, undertaken to evaluate the possibility of a somatic mutation in the noggin gene which could be carried by a small subset of white blood cells, also failed to detect the presence of the reported 42-bp deletion. We conclude that mutations in the coding region of noggin are not associated with FOP.

Methylene tetrahydrofolate reductase (MTHFR) and nitric oxide synthase (ecNOS) genes and risks of peripheral arterial disease and coronary heart disease: Edinburgh Artery Study

Hyperhomocysteinaemia and reduced nitric oxide synthesis may each result in endothelial dysfunction predisposing to atherogenesis. Genetic variants of methylene tetrahydrofolate reductase (MTHFR) and endothelial nitric oxide synthase (ecNOS) influence homocysteine metabolism and nitric oxide synthesis, respectively and might thus be determinants of the risk of atherosclerotic disease. The aim of our study was to identify, in a general population sample, the risks of peripheral arterial disease and of coronary heart disease related to MTHFR (175;198) and ecNOS (4;5) polymorphisms. In the Edinburgh Artery Study, which is a population based cohort study, 940 men and women aged 60-79 years, who had previously been selected at random from the general population, had DNA extracted from a venous blood sample. Based on a clinical examination at baseline and follow up investigations, three groups of subjects were identified: those with peripheral arterial disease (n=80), those with coronary heart disease (n=137), and healthy controls who had no evidence of cardiovascular disease (n=300). The distributions of the ecNOS and MTHFR genotypes did not differ significantly between the groups with and without cardiovascular disease. However, the ecNOS-4 allele (frequency 0.13) was related to the occurrence of coronary heart disease in non smokers, OR=2.47 (95% CI [1.42, 4.34], P=0.02). No association was found with peripheral arterial disease. The MTHFR-175 allele (frequency 0.31) was not related to coronary heart disease, but was associated with a reduced risk of peripheral arterial disease, OR=0.54 (95% CI [0.32, 0.90], P=0.02). Neither the ecNOS-4 allele or MTHFR-175 allele was related to the ankle brachial pressure index in the whole study population. In conclusion, the ecNOS-4 allele was associated with a slightly increased risk of coronary heart disease in non-smokers, but otherwise the MTHFR and ecNOS genotypes appeared to have little influence on the risks of peripheral arterial disease and coronary heart disease in this older population.

Glomerular hyperfiltration, high renin, and low- extracellular volume in high blood pressure

Abnormal renovascular resistance and glomerular filtration rate are characteristic of established hypertension and may also be involved in its pathogenesis. To determine renal and body fluid correlates of the predisposition to high blood pressure, we examined 100 healthy young adults with high or low blood pressure. Within each group, half had parents with high blood pressures, and half had parents with low blood pressures. Renal function and hemodynamics, body fluid volumes, and relevant hormones and genotypes were measured. Subjects with high personal and parental blood pressures had the highest levels of glomerular filtration rate (P<0.02) and plasma active renin concentration and low levels of exchangeable sodium and plasma volume (P<0.02). High glomerular filtration rate was not associated with differences in urinary kallikrein or prostaglandins. Polymorphisms of the renin, angiotensin-converting enzyme, and angiotensinogen genes were not associated with differences in glomerular filtration rate or renin. Subjects with high personal, but low parental, blood pressures had low exchangeable sodium and plasma volumes (P<0.02) but normal glomerular filtration rates. In this population, extracellular volume depletion and high renin are correlates of high blood pressure in early adulthood, and glomerular hyperfiltration is a feature of those who also have familial predisposition to high blood pressure.

Placental synthesis of oestriol in Down's syndrome pregnancies

In the second trimester, oestriol is synthesized in the placenta and secreted into the maternal circulation. 16alpha-hydroxy dehydroepiandrosterone sulphate (16alpha-OH-DHEAS) is formed in the fetal liver by hydroxylation of dehydroepiandrosterone sulphate (DHEAS) and transported to the placenta where it undergoes desulphation by steroid sulphatase (STS) and aromatization to oestriol. Maternal serum levels of unconjugated oestriol (UE3) are lower in Down's syndrome pregnancies than in unaffected pregnancies in the second trimester. The underlying cause of this variation was investigated in placenta, fetal liver, maternal serum and amniotic fluid from Down's syndrome pregnancies by measuring the levels of UE3, DHEAS and STS in appropriate tissues and in corresponding samples from unaffected pregnancies. UE3 levels, expressed as multiples of the control median at the appropriate gestation (MOM), were lower in placental tissue (0.52 MOM), maternal serum (0.65 MOM) and amniotic fluid (0.61 MOM) than in unaffected pregnancies. There was a significant correlation between placental and maternal serum levels of UE3 in the Down's syndrome cases. The median STS activity in placental tissue from Down's syndrome pregnancies (1.14 MOM) was not significantly different from that of the control pregnancies (1. 01 MOM), suggesting that placental turnover of the fetal precursor DHEAS is not reduced. However, levels of DHEAS were reduced in maternal serum (0.69 MOM), placental tissue (0.54 MOM) and fetal liver (0.65 MOM) from Down's syndrome pregnancies. Thus, a diminished supply of the fetal precursor DHEAS may be the cause of the decreased placental production of UE3 in Down's syndrome pregnancies in the second trimester.

Phenotypic and molecular heterogeneity in fibrodysplasia ossificans progressiva

Fibrodysplasia (myositis) ossificans progressiva (FOP) is an extremely rare inherited disorder in which progressive ossification of major striated muscles, often following injury, is associated with abnormal skeletal patterning. Altered expression of bone morphogenetic proteins may be a contributory cause. To examine this hypothesis, we compared the patterns of expression of bone morphogenetic proteins (BMPs) mRNAs from lymphoblastoid cell lines from two small multigenerational families with autosomal dominant transmission of FOP. Although affected members of both families showed the characteristic phenotype of FOP, one family was more severely affected than the other. Expression of mRNAs for BMP-1, 2, 3, 5, and 6 mRNAs were not detected within the more severely affected family, but BMP-4 mRNA was expressed in affected but not unaffected members of this family. The results of linkage exclusion analysis using a highly polymorphic microsatellite marker near the BMP-4 gene were consistent with linkage of FOP and BMP-4 in this family. Within the less severely affected family, affected and unaffected members showed similar levels of mRNA expression of BMPs 1, 2, 4, and 5, and linkage of FOP to the BMP-4 gene was excluded. It is concluded that clinical, radiographic, and biochemical data in these two families with FOP establish clinical and molecular heterogeneity and also suggest the possibility of genetic heterogeneity.

Second-trimester pregnancy associated plasma protein-A levels are reduced in Cornelia de Lange syndrome pregnancies

Maternal serum samples were collected from 19 pregnancies which resulted in the birth of a child with the classical Cornelia de Lange syndrome phenotype ascertained by careful clinical review. Using specific immunoassays, the serum levels of pregnancy associated plasma protein-A, free-beta human chorionic gonadotrophin and inhibin A were investigated. Pregnancy associated plasma protein-A was detectable in all cases but the levels were significantly reduced in second-trimester maternal serum from 18 affected pregnancies. Expressed as multiples of the median (MOM), the results ranged from 0.03 MOM to 0.71 MOM with an overall median value of 0.21 MOM (Mann-Whitney p<0.001). From these data it is possible to estimate a probability that any given level of this serum marker is associated with an affected pregnancy. One further sample taken in the first trimester from an affected pregnancy at 11 weeks' gestation had a normal pregnancy associated plasma protein-A level (1.22 MOM). Less markedly reduced levels were found for free beta human chorionic gonadotrophin and inhibin A. We conclude that second-trimester maternal serum pregnancy associated plasma protein-A measurements may be of value as an adjunct to ultrasonography in the prenatal diagnosis of Cornelia de Lange syndrome. A table of likelihood ratios is presented.

Two years' prospective experience using fluorescence in situ hybridization on uncultured amniotic fluid cells for rapid prenatal diagnosis of common chromosomal aneuploidies

A probe was generated from the YAC clone 831B9 that was suitable for the prenatal detection of trisomy 21 using fluorescence in situ hybridization (FISH). This probe was initially tested on a series of 650 unselected amniotic fluid samples prior to the karyotype being available. 630 were correctly identified as having two copies and 13 samples were correctly scored as having three copies of chromosome 21. Seven samples failed to produce a result. A trial was then initiated, reporting to clinicians the interphase FISH results before cytogenetic analysis had been performed. During the first 18 months of this trial 1504 samples were tested: 1467 were correctly identified as disomic and 35 samples were correctly scored as trisomic for chromosome 21. Two samples failed to produce a result. A chromosome 18 specific probe (LI.84) was employed where there was a relevant clinical indication (181 samples) and 10 samples were correctly scored as having three copies of chromosome 18. Thus, this approach appears to be reliable and is popular with both clinicians and patients due to the speed of the result. However, it does not replace chromosomal analysis on cultured cells, which detected a range of abnormalities besides the trisomies and triploidies detected by FISH.

Neuroticism and polymorphisms in the serotonin transporter gene

BACKGROUND

There is evidence for an association between two different polymorphisms of the human serotonin transporter gene (5-HTT) and the personality trait of neuroticism and affective disorder.

METHODS

We studied the association between neuroticism and polymorphisms in the 5HTT-linked promoter region and in a variable number tandem repeat region (VNTR) of the 5-HTT gene in 204 people aged over 60 derived from a random sample of men and women in the general population. Approximately half of the subjects were in the top 20% of neuroticism scorers and half in the bottom 20%.

RESULTS

There were no significant differences in allelic or genotypic frequencies between the high and low neuroticism scorers. There was highly significant linkage disequilibrium between the two 5-HTT gene polymorphisms, and haplotype analysis showed no association between neuroticism level and haplotype.

CONCLUSIONS

Reports of an association between two 5-HTT gene polymorphisms and the personality trait of neuroticism are not supported by these results.

Fibrinogen, factor VII and PAI-1 genotypes and the risk of coronary and peripheral atherosclerosis: Edinburgh Artery Study

There are now many epidemiological studies that have shown a relationship between haemostatic factors and subsequent risk of both coronary and peripheral arterial disease. However, there is less information on the association between genetic variation in these factors and the risks of coronary and peripheral arterial disease. As part of the five-year follow-up of the Edinburgh Artery Study, polymorphisms of the fibrinogen (-455G/A), factor VII (R/Q353) and PAI-1 (HindIII) genes were measured in men and women aged 60-79 years, together with their plasma levels. Using widely accepted criteria, 88 subjects were identified as having peripheral arterial disease (PAD), 195 having coronary artery disease (CAD) and 423 subjects comprised a "healthy" group. The -455AA genotype of the fibrinogen gene was found to be more frequent among those subjects with PAD. This genotype also showed the highest plasma fibrinogen levels in both disease groups and in the healthy group. Using logistic regression, after adjustment for age, sex, smoking and plasma level, the -455AA genotype was associated with over twice the risk of PAD compared with the -455GG genotype, the odds ratio reaching marginal significance (p < or = 0.10). Combining those with genotype -455AA with the heterozygotes in order to increase the power of the study resulted in a more significant multiple-adjusted risk of PAD (p < or = 0.05). These data provide evidence that a polymorphism of the P fibrinogen gene is associated with an increased risk of peripheral atherosclerosis.

Detection of t(12;21) in childhood acute lymphoblastic leukemia by fluorescence in situ hybridization

Metaphase preparations from 36 patients with acute lymphoblastic leukemia (ALL) have been retrospectively screened by fluorescence in situ hybridization (FISH) to determine the incidence of translocation (12;21) and the potential usefulness of FISH as an adjunct to conventional cytogenetic analysis. With the use of specific chromosome paints, 4 of 31 patients with B-lineage childhood ALL (13%) demonstrated rearrangements of chromosomes 12 and 21, and therefore, were considered to harbor the translocation, which had not previously been detected by conventional karyotyping. However, none of these positive cases revealed the standard reciprocal t(12;21)(p12;q22) as the sole abnormality involving chromosomes 12 and 21. The study confirms the feasibility and advantages of introducing FISH screening for t(12;21) in pediatric ALL cases and demonstrates the usefulness of FISH screening as a backup to concurrent cytogenetic analysis to resolve variant translocations and aberrant results. The presence of t(12;21) has also been correlated to clinical data to assess the prognostic significance of this translocation on its own or in association with other prognostic features.

Genetic and environmental influences in the development of multiple primary melanoma

OBJECTIVES

To identify risk factors and the prognosis associated with the development of multiple primary melanoma (MPM).

DESIGN

Case-comparison studies of subjects with MPM and single primary melanoma. Sequencing of CDKN2A in germline DNA.

SETTING

Population-based study of patients with invasive melanoma in Scotland between 1979 and 1996.

PATIENTS

For mortality studies, 108 patients with MPM and 216 single melanoma controls matched for age, sex, site, and tumor thickness. For risk factor studies, 48 patients with MPM and 48 single melanoma controls matched as above. For CDKN2A analysis, a sample of 23 subjects with MPM.

RESULTS

The development of MPM was found not to be an independent prognostic factor. The risk of MPM was greatest in those with a family history of melanoma, with large numbers of benign nevi, and the presence of clinically or histologically atypical nevi. Germline mutations of CDKN2A were present in 6 of 23 patients with MPM and in 5 cases consisted of the base pair substitution Met53Ile.

CONCLUSIONS

The importance of MPM should be addressed in melanoma follow-up protocols. Those patients at greatest risk can be identified by a family history of melanoma and their mole pattern. Germline mutations in CDKN2A occur in both familial and sporadic MPM and further studies are required to determine the value of analysis of this gene in melanoma surveillance. Patients should be informed that the development of MPM does not adversely affect their prognosis.

1.4 Mb candidate gene region for X linked dyskeratosis congenita defined by combined haplotype and X chromosome inactivation analysis

Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the early onset of reticulate skin pigmentation, nail dystrophy, and mucosal leucoplakia. In over 80% of cases bone marrow failure develops and this is the main cause of early mortality. The DC1 gene responsible for the X linked form (MIM 305000) of dyskeratosis congenita has been mapped to Xq28. In order to narrow the candidate gene region, genetic linkage analysis was performed in eight X linked pedigrees using a set of markers spanning Xq28. A maximum lod score of 5.31 with no recombinations was achieved with marker DXS1073. Two recombination events were identified; one of these uses X chromosome inactivation pattern analysis to determine carrier status and haplotype analysis to fine map the recombination breakpoint. The fine mapping of these recombination events has enabled the candidate gene region for X linked dyskeratosis congenita to be defined as the 1.4 Mb interval between Xq3274 and DXS1108.

Mosaic supernumerary ring chromosome 19 identified by comparative genomic hybridisation

We report the use of comparative genomic hybridisation (CGH) to define the origin of a supernumerary ring chromosome which conventional cytogenetic banding and fluorescence in situ hybridisation (FISH) methods had failed to identify. Targeted FISH using whole chromosome 19 library arm and site specific probes then confirmed the CGH results. This study shows the feasibility of using CGH for the identification of supernumerary marker chromosomes, even in fewer than 50% of cells, where no clinical or cytogenetic clues are present.

CDKN2A germline mutations in U.K. patients with familial melanoma and multiple primary melanomas

We report six of 16 U.K. melanoma families and two of 17 patients with multiple primary melanomas and a negative family history who have between them four different functionally damaging mutations of the CDKN2A (p16) gene: an Arg 24 Pro substitution in exon 1 in one family, a stop codon at codon 44 of exon 1 in one family, and a Met 53 Ile substitution in exon 2 in four families. One multiple primary melanoma patient also has the Met 53 Ile mutation and a second has a G-T substitution at the IVS2 + 1 splice donor site. Our data together with other recent publications from France and the U.S.A. indicate that screening melanoma kindreds with only two affected family members for CDKN2A mutations is justified.

Human alpha-adducin gene, blood pressure, and sodium metabolism

The adducin genes contribute significantly to population variation in rat blood pressure and cell membrane sodium transport. The 460Trp mutation of the human alpha-adducin gene has been associated with hypertension, in particular hypertension sensitive to sodium restriction. We studied the relationship between the 460Trp mutation and population variation in blood pressure and sodium metabolism. From 603 Scottish families, we selected 151 offspring and 224 parents with blood pressures in either the upper (high) or bottom (low) 30% of the population distribution and measured the 460Trp mutation using allele-specific hybridization. In offspring, we also measured exchangeable sodium, plasma volume, and total body water. Plasma levels of components of the renin-angiotensin system, atrial natriuretic peptide, and cellular sodium and transmembrane sodium efflux were also estimated. The overall frequency of the 460Trp mutation was 27.1%. In offspring and parent groups, we found no difference in the genotype or allele frequencies of the 460Trp mutation between subjects with high or low blood pressure. There was no overall association between the alpha-adducin genotypes and blood pressure variation. In offspring, the 460Trp mutation was not associated with any significant differences in body fluid volumes or exchangeable sodium; levels of plasma renin, angiotensin II, aldosterone, or atrial natriuretic peptide; intracellular sodium; or ouabain-sensitive transmembrane sodium efflux. These findings suggest that in our Scottish population, the alpha-adducin 460Trp polymorphism is not related to blood pressure and does not affect whole body or cellular sodium metabolism.

Prediction of liability to orofacial clefting using genetic and craniofacial data from parents

BACKGROUND

Cleft lip with or without cleft palate (CL(P)) and isolated cleft palate (CP) are separate clinical entities and for both polygenic multifactorial aetiology has been proposed. Parents of children with orofacial clefting have been shown to have distinctive differences in their facial shape when compared to matched controls.

OBJECTIVE

To test the hypothesis that genetic and morphometric factors predispose to orofacial clefting and that these markers differ for CL(P) and CP. Methods-Polymorphisms at the transforming growth factor alpha (TGFalpha) locus in 83 parents of children with nonsyndromic orofacial clefts were analysed, and their craniofacial morphology was assessed using lateral cephalometry.

RESULTS

Parents of children with CL(P) and CP showed an increased frequency of the TGFalpha/TaqI C2 allele (RR=4.10, p=0.009) relative to the comparison group. Also the TGFalpha/BamHI A1 allele was more prevalent in the CP parents. MULTIVARIATE STATISTICAL ANALYSIS: Using stepwise logistic regression analysis the TGFalpha/TaqI C2 polymorphism provides the best model for liability to orofacial clefting. To determine the type of clefting a model involving interaction between the parental TGFalpha/BamHI and TGFalpha/RsaI genotypes showed the best fit. Using genotype only to predict the clefting defect in the children according to parental genotype, 68.3% could be correctly classified. By adding information on craniofacial measurements in the parents, 76% of CP and 94% of CL(P) parents could be correctly classified.

CONCLUSIONS

This study provides a model for prediction of liability to orofacial clefting. These findings suggest that different molecular aberrations at the TGFalpha locus may modify the risk for CP and CL(P).

Acute intermittent porphyria: alternative splicing of hydroxymethylbilane synthase mRNA excludes exons 3 and 12

The hydroxymethylbilane synthase (HMBS) mRNAs from 44 control individuals and 30 patients suffering from acute intermittent porphyria (AIP), were screened for length differences by reverse transcriptase polymerase chain reaction (RT-PCR) and any abnormalities were characterized by direct sequencing. Examination of the mRNAs extracted from the peripheral blood lymphocytes of the samples revealed varying degrees of alternative splicing, involving the removal of exons 3 and 12. Approximately 10-50% of the mRNA molecules were affected, despite the absence of genomic splice site mutations or any major deviance from consensus splice sequence values. The preliminary data obtained from this study suggest that this event is a normal occurrence in peripheral blood lymphocytes, and may not be associated with the molecular pathology responsible for AIP.

A new strategy for cryptic telomeric translocation screening in patients with idiopathic mental retardation

Cryptic unbalanced chromosome rearrangements in the telomeric bands of human chromosomes constitute a significant cause of "idiopathic" mental retardation. Here, we have described a new strategy based upon comparative genomic hybridisation (CGH) to screen for these abnormalities. A modified CGH analysis showed three unbalanced cryptic rearrangements in five patients from three families. These chromosome abnormalities and their balanced forms in the relatives were then confirmed by fluorescence in situ hybridisation (FISH). This study describes a new approach to the diagnosis of cryptic translocations between the G band negative ends of chromosomes and confirms the significant contribution of cryptic telomeric rearrangements to idiopathic mental retardation.

Identification of two novel mutations in the hydroxymethylbilane synthase gene in three patients from two unrelated families with acute intermittent porphyria

We have screened the hydroxymethylbilane synthase cDNAs of 3 patients from 2 families suffering from acute intermittent porphyria (AIP) from Scotland and South Africa using heteroduplex and chemical cleavage of mismatch analyses. Direct sequencing was used to characterise the mutations. The two novel mutations identified were a missense mutation at nucleotide position 64 in exon 3 (R22C) and a single base-pair deletion in exon 15. These mutations are predicted to affect the normal function of the enzyme and, therefore, are expected to be the primary cause of disease in these patients.

Biochemical markers of trisomy 21 and the pathophysiology of Down's syndrome pregnancies

Using biochemical and immunocytochemical methods, we have investigated endogenous levels of various markers in tissues obtained from 67 Down's syndrome pregnancies after therapeutic abortion in the second trimester and in corresponding tissues from unaffected abortuses. Alpha-fetoprotein (AFP), intact and free beta human chorionic gonadotrophin (hCG), pregnancy-specific beta-1 glycoprotein (SP-1), placental alkaline phosphatase (PALP), pregnancy-associated plasma protein A (PAPP-A), and gamma glutamyl transferase (GGT) were investigated in placental tissue; AFP and GGT in fetal liver; and GGT in fetal intestine. The results indicate that maternal serum levels of placental products reflect those found in the placenta: intact hCG, free beta hCG, and SP-1 levels were elevated in Down's syndrome pregnancies, while PAPP-A and PALP levels were little changed. This suggests that membrane passage of these markers is not affected but there is altered synthesis of hCG and SP-1. AFP levels were strikingly elevated in placental homogenates and unchanged in liver homogenates from Down's syndrome pregnancies, while the levels in maternal serum were reduced, pointing to a possible transport defect specific to AFP. GGT levels were high in placenta and liver from Down's syndrome pregnancies but low in fetal intestine.

Evidence for a familial pregnancy-induced hypertension locus in the eNOS-gene region

Pregnancy-induced hypertension may be regarded as a manifestation of endothelial-cell dysfunction. The role of the eNOS gene in the development of a familial pregnancy-induced hypertension was evaluated by analysis of linkage among affected sisters and in multiplex families (n = 50). Markers from a 4-cM region encoding the eNOS gene showed distortion from the expected allele sharing among affected sisters (P = .001-.05), and the statistic obtained from the multilocus application of the affected-pedigree-member method also showed distortion (T[f(P)=sqrt(P)] = 3.53; P < .001). A LOD score of 3.36 was obtained for D7S505 when a best-fitting model derived from genetic epidemiological data was used, and LOD scores of 2.54-4.03 were obtained when various other genetic models were used. Estimates of recombination rate, rather than maximum LOD-score values, were affected by changes in the genetic parameters. The transmission-disequilibrium test, a model-free estimate of linkage, showed strongest association and linkage with a microsatellite within intron 13 of the eNOS gene (P = .005). These results support the localization of a familial pregnancy-induced hypertension-susceptibility locus in the region of chromosome 7q36 encoding the eNOS gene.

Acute intermittent porphyria: the in vitro expression of mutant hydroxymethylbilane synthase

Acute intermittent porphyria (AIP) is an inborn error of haem biosynthesis caused by a variety of mutations in the gene coding for hydroxymethylbilane synthase (HMB-S). The entire coding sequence of this gene, from each of three South African AIP patients, was therefore screened for mutations using chemical cleavage mismatch (CCM) analysis and any changes detected characterized by DNA sequencing. Three single base changes were identified; a G77 to A in exon 3, a C346 to T in exon 8 and a G518 to A in exon 10. These missense mutations, previously reported to be present in other populations, are known to be responsible for the structurally deleterious amino acid replacements R26H, R116W and R173Q, respectively. The in vitro expression of the enzymes containing these mutations and the subsequent measurement of their specific activities revealed a reduction to approximately 4% of normal activity.

Screening for Down's syndrome: changes in marker levels and detection rates between first and second trimesters

OBJECTIVE

To monitor changes with gestation in levels of alpha-fetoprotein (AFP), free beta human chorionic gonadotrophin (F beta hCG) and pregnancy associated plasma protein-A (PAPP-A) in Down's syndrome pregnancies and to compare risks estimated in the first trimester with those obtained by routine screening in the second trimester for the same pregnancies.

DESIGN

In each of 47 Down's syndrome pregnancies two maternal serum samples were obtained, one in the first trimester and one in the second trimester. Comparison of marker levels with 10,600 first trimester controls and a smaller sample of second trimester controls allowed case identification criteria based on optimum marker combinations to be developed and compared directly between trimesters.

SETTING

Biochemical genetics laboratory.

RESULTS

F beta hCG was an effective marker of Down's syndrome in both the first and second trimesters. PAPP-A levels were significantly reduced in trisomy 21 pregnancies in the first trimester only. Using a population model, these two markers in combination with maternal age gave an overall detection rate of 55% for a 5% false positive rate in the first trimester. For the paired first and second trimester samples, three of six cases classified as low risk by routine second trimester screening were classified as high risk by the first trimester screening protocol of F beta hCG/PAPP-A/maternal age. However, fifteen cases identified as high risk by routine second trimester screening were classified as low risk in the first trimester, a net loss in detection of 12 cases by first trimester screening.

CONCLUSION

The data suggest that first trimester detection rates for Down's syndrome using a combination of F beta hCG and PAPP-A may vary with gestation and will be lower than those currently obtained by routine second trimester screening with AFP/hCG.

Insulin-dependent diabetes mellitus and prenatal screening results: current experience from a regional screening programme

From around 91,000 women having routine prenatal screening for Down's syndrome and neural tube defects between July 1992 and October 1995, 261 women were identified as having insulin-dependent diabetes mellitus (IDDM). Alpha-fetoprotein (AFP) and human chorionic gonadotrophin (hCG) levels were reduced in these women, with median levels of 0.89 and 0.91 multiples of the median (MOM), respectively. The IDDM patients had a median weight which was 6 kg heavier than that of non-IDDM women. After correction for maternal weight, the AFP and hCG levels in the IDDM patients were 0.98 and 0.92 MOM, respectively. In routine practice, using results which were not weight-corrected, the IDDM women were neither over- nor under-represented in the high-risk group for Down's syndrome, but showed a tendency to be under-represented in the high-risk group for neural tube defects.

Heat-stable and immunoreactive placental alkaline phosphatase in maternal serum from Down's syndrome and trisomy 18 pregnancies

Placental alkaline phosphatase (ALP) activity was investigated in second-trimester maternal sera from 37 pregnancies with Down's syndrome, 28 pregnancies with trisomy 18, and in a series of 497 controls using a fluorimetric heat inactivation assay and specific immunoassay. After conversion of individual analyte values to multiples of the normal gestational median (MOM), no significant differences in total or placental ALP activities were found in the trisomy 21 or trisomy 18 cases (P > 0.01). In the Down's syndrome pregnancies, total ALP activity was 0.93 MOM, heat-stable ALP activity was 1.09 MOM, and placental ALP (by immunoassay) 0.96 MOM. In the trisomy 18 cases, total ALP activity was 0.90 MOM, heat-stable ALP activity was 0.79 MOM, and placental ALP (by immunoassay) 0.94 MOM. We conclude that neither total nor placental ALP activity is a useful marker for Down's syndrome or trisomy 18 screening.

Genetic localisation of MRX27 to Xq24-26 defines another discrete gene for non-specific X-linked mental retardation

A large family with non-specific X-linked mental retardation (MRX) was first described in 1991 [Glass et al., 1991], with a suggestion of linkage to Xq26-27. The maximum lod score was 1.60 (theta = 0.10) with the F9 locus. The localisation of this MRX gene has now been established by linkage to microsatellite markers. Peak pairwise lod scores of 4.02 and 4.01 (theta = 0.00) were attained at the DXS1114 and DXS994 loci respectively. This MRX gene is now designated MRX27 and is localised to Xq24-26 by recombination events detected by DXS424 and DXS102. This regional localisation spans 26.2 cM on the genetic background map and defines another distinct MRX interval by linkage to a specific region of the X chromosome.

Prenatal diagnosis by enzyme analysis in 15 pregnancies at risk for the Lesch-Nyhan syndrome

Fifteen pregnancies at risk for Lesch-Nyhan syndrome were investigated between 8 and 17 weeks' gestation by measurement of hypoxanthine-guanine phosphoribosyl transferase (HGPRT) and adenine phosphoribosyl transferase (APRT) enzyme activities in chorionic villus samples (cultured and uncultured) or in cultured amniotic fluid cells. Ten pregnancies had normal enzyme levels and a normal outcome while a further two predicted to be normal miscarried later in the pregnancy. Three pregnancies had low levels of residual HGPRT activity in chorionic villi. Comparable levels of residual activity in the index case in two pregnancies and in cells from the abortus in the third case confirmed that the pregnancies were affected.

Dimeric inhibin A as a marker for Down's syndrome in early pregnancy

BACKGROUND

In screening for Down's syndrome in the second trimester of pregnancy, the concentrations of alpha-fetoprotein, the beta subunit of human chorionic gonadotropin, and intact human chorionic gonadotropin in material serum are widely used markers. We investigated a new marker, dimeric inhibin A, and compared its predictive value with that of the established markers.

METHODS

Serum samples were obtained at 7 to 18 weeks of gestation from 58 women whose fetuses were known to be affected by Down's syndrome, 32 whose fetuses were affected by trisomy 18, and 438 whose fetuses were normal, and the samples were analyzed for each marker. Individual serum concentrations of each marker were converted to multiples of the median value at the appropriate length of gestation in the women with normal pregnancies, and rates of detection of Down's syndrome by screening for inhibin A in various combinations with the other markers were estimated by multivariate analysis.

RESULTS

In the women with fetuses affected by Down's syndrome, the serum inhibin A concentrations were 2.06 times the median value in the women with normal pregnancies (P < 0.001). This compared with 2.00 times the median for the beta subunit of human chorionic gonadotropin, 1.82 times the median for intact human chorionic gonadotropin, and 0.72 for alpha-fetoprotein. The serum concentrations of inhibin A in the women with fetuses affected by Down's syndrome did not appear to be significantly elevated above normal until the end of the first trimester and were not significantly different from normal in the women with fetuses affected by trisomy 18 (P = 0.17). The rate of detection of Down's syndrome was 53 percent and the false positive rate was 5 percent when alpha-fetoprotein, the beta subunit of human chorionic gonadotropin, the maternal age were used together as predictors. The detection rate increased to 75 percent when inhibin A was added (P = 0.002).

CONCLUSIONS

In the second trimester of pregnancy, measuring inhibin A in maternal serum, in combination with measurements of alpha-fetoprotein and beta subunit of human chorionic gonadotropin, significantly improved the rate of detection of Down's syndrome.

A practical strategy for detection of major chromosome aneuploidies using ratio-mixing fluorescence in situ hybridization

We describe the use of ratio-mixing FISH to visualize simultaneously probe sets specific for chromosomes 13, 18 and 21 as well as both sex chromosomes in uncultured lymphocytes and amniocytes. This method has the advantage of a smaller sample requirement than uni-colour FISH and potential for analysis of a larger number of chromosome aneuploidies using a minimum number of different probe haptenization and detection systems. An unselected series of uncultured lymphocytes and amniocytes was used to investigate the reliability of ratio-mixing FISH for diagnostic applications. The results indicate that the five-colour ratio-mixing FISH is a reliable technique and can be used for simultaneous detection of major aneuploidies. However, as a diagnostic approach, the strategy of using a three-colour ratio-mixing FISH and a dual colour to detect the five clinically important aneuploidies on two slides from the same sample, appears to be simpler and more practical.

Detection of four mutations in six unrelated South African patients with acute intermittent porphyria

We have screened the hydroxymethylbilane synthase cDNA from six South African patients with acute intermittent porphyria, using a combination of chemical cleavage mismatch analysis and direct sequencing of asymmetrically amplified PCR products. Four mutations were detected, a novel T insertion (771insT) and three missense mutations (R26H, R116W and R173Q). The 771insT mutation produces a stop codon, thirty-three codons downstream and a loss of approximately 20% of the protein is predicted. The R116W mutation, which was found to have a high prevalence in the Dutch population, was detected in three unrelated South African patients.

An increased incidence of thyroid antibodies in patients with Turner's syndrome and their first degree relatives

Previous studies have suggested that there may be a link between Turner's syndrome and autoimmunity. The numbers involved in these studies have tended to be small and few studies have included family members. This study has compared the incidence of thyroid antibodies in the serum of 60 patients with Turner' syndrome and 50 of their mothers with 127 controls. Total T4 and TSH levels were also measured. Of the 60 patients with Turner's syndrome 18 (30%) were positive for either thyroid peroxidase (TPO) and/or thyroglobulin antibodies. The peak incidence of thyroid antibodies occurred at 13 years of age. 11 (22%) of the mothers were also antibody positive. The incidence of thyroid antibodies was significantly higher in both the patients with Turner's Syndrome (30 vs 1.7% p < 0.001) and their mothers (22 vs 6.6% p < 0.05) than in the control groups. The increased incidence of thyroid antibodies found in these patients and their mothers confirms that there is an association between Turner's Syndrome and autoimmunity. However unlike previous studies we found more patients were positive for thyroglobulin than TPO antibodies.

Expression and loss of heterozygosity of c-met proto-oncogene in primary breast cancer

The c-met proto-oncogene encodes the receptor to hepatocyte growth factor-scatter factor (HGF-SF), a mesenchyme-derived cytokine with cell-dissociating, invasion, and angiogenic properties. The expression of c-met in breast cancer is the subject of controversy; 111 primary breast cancers were examined for LOH of c-met by Southern blot electrophoresis. c-met expression was measured in a further 40 patients with breast cancer and in 8 patients with benign breast disease by flow cytometry. LOH of c-met was detected in only 4% of informative breast cancers. Expression of c-met was significantly greater in patients with breast cancer than in those with benign breast disease (P < 0.01, Mann-Whitney). There was no correlation however between increased c-met expression and clinicopathological prognostic variables. These results do not support the role of c-met as a tumour suppressor gene in breast cancer but suggest increased receptor expression in malignant breast disease. The significance of this increased expression in breast cancer is the subject of further investigation.

The SA gene: predisposition to hypertension and renal function in man

1. The SA gene is expressed in the kidneys and is associated with hypertension in man and experimental animal models. Predisposition to hypertension is associated with renal haemodynamic abnormalities and increased renal SA gene expression. 2. We studied the distribution of the SA gene alleles (A1, A2), defined by the PstI polymorphism, in young adults with contrasting predisposition to hypertension to determine whether genetic variation at the SA gene locus is associated with variations in renal haemodynamics, electrolyte metabolism and the renin-angiotensin system. 3. The frequency of the A2 allele was not significantly different between subjects with high personal and parental blood pressures and subjects with low personal and parental blood pressures. We detected no overall relationship between blood pressures and SA genotype, even after taking sodium intake into account. 4. Glomerular filtration rate, renal blood flow, renal vascular resistance, plasma volume, exchangeable sodium and total body water did not differ according to SA genotypes. Moreover, we detected no significant effect of SA genotype on circulating components of the renin-angiotensin system or atrial natriuretic peptide. 5. In our population, genetic variation at the SA gene locus defined by PstI polymorphism does not influence the renal characteristics that contribute to the development of hypertension.

Analysis of maternal serum alpha-fetoprotein and free beta human chorionic gonadotrophin in the first trimester: implications for Down's syndrome screening

The aim of this study was to determine the maternal population, pregnancy, serum alpha-fetoprotein (AFP) and free beta subunit of human chorionic gonadotrophin (F beta hCG) parameters in a large series of women attending prenatal clinics before 15 weeks' gestation and to assess the practical problems of population screening for Down's syndrome in the first trimester using these markers. Serum samples were collected from 8600 women attending prenatal clinic booking visits. Maternal serum AFP and F beta hCG medians were calculated for each day of gestation (49-104 days), using both dates and ultrasound estimates of gestation. The effects of maternal weight, twin pregnancies, and threatened abortion on AFP and F beta hCG levels were analysed. The median age of the population was 27.1 years and the median weight 62.1 kg. Twenty-six per cent of samples were collected before 70 days and 50 per cent before 78 days' gestation. Eighty-nine per cent of all samples had gestational estimates by dates, 60 per cent by ultrasound and 52 per cent by both dates and ultrasound. The AFP median was 5 kU/l at 49 days, 5.9 kU/l at 70 days, and 17.9 kU/l at 100 days. The peak median F beta hCG level was 66.4 ng/ml at 64 days, falling to 20.6 ng/ml at 100 days' gestation. Both AFP and F beta hCG levels showed log Gaussian distributions but the standard deviation for AFP was 20 per cent greater than that found in the second trimester. AFP and F beta hCG levels showed an inverse relationship with maternal weight and were increased in twin pregnancies (1.68 and 1.97 multiples of the median, respectively). AFP and F beta hCG can be readily measured in a large screening population in the first trimester. Down's syndrome screening protocols based on these markers could be refined by the use of gestations in individual days but AFP is likely to be a less effective marker and detection rates are likely to be lower than in the second trimester. To realize the potential of first-trimester screening, more women should be encouraged to attend the prenatal clinic in early pregnancy and ultrasound dating should be carried out for all pregnancies at this stage.