Predominance of a 6 bp deletion in exon 2 of the LDL receptor gene in Africans with familial hypercholesterolaemia

In South Africa, the high prevalence of familial hypercholesterolaemia (FH) among Afrikaners, Jews, and Indians as a result of founder genes is in striking contrast to its reported virtual absence in the black population in general. In this study, the molecular basis of primary hypercholesterolaemia was studied in 16 Africans diagnosed with FH. DNA analysis using three screening methods resulted in the identification of seven different mutations in the coding region of the low density lipoprotein (LDLR) gene in 10 of the patients analysed. These included a 6 bp deletion (GCGATG) accounting for 28% of defective alleles, and six point mutations (D151H, R232W, R385Q, E387K, P678L, and R793Q) detected in single families. The Sotho patient with missense mutation R232W was also heterozygous for a de novo splicing defect 313+1G-->A. Several silent mutations/polymorphisms were detected in the LDLR and apolipoprotein B genes, including a base change (g-->t) at nucleotide position -175 in the FP2 LDLR regulatory element. This promoter variant was detected at a significantly higher (p<0.05) frequency in FH patients compared to controls and occurred in cis with mutation E387K in one family. Analysis of four intragenic LDLR gene polymorphisms showed that the same chromosomal background was identified at this locus in the four FH patients with the 6 bp deletion. Detection of the 6 bp deletion in Xhosa, Pedi, and Tswana FH patients suggests that it is an ancient mutation predating tribal separation approximately 3000 years ago.

The apolipoprotein B R3531C mutation. Characteristics of 24 subjects from 9 kindreds

Familial ligand-defective apolipoprotein B (apoB) is a group of disorders caused by mutations in the apoB gene. In this report the R3531C mutation is characterized further using a monoclonal antibody MB19/dynamic laser light scattering technique to measure ratios of Cys(3531) to normal low density lipoprotein (LDL) particles. All six subjects studied showed a preferential accumulation of particles carrying the defective apoB allotype. We determined binding properties of LDL from R3531C heterozygotes by measurement of high-affinity binding to LDL receptors on fibroblasts and its ability promote growth of U937 cells. LDL from R3531C heterozygotes, compared to normal LDL, had 49.3% of the binding affinity and was 74% as effective in a U937 cell proliferation assay. To identify new probands, we screened 2570 subjects for the R3531C mutation. Nine probands were found with 15 affected relatives. Of the seven haplotypes we uncovered, two were novel, while five were identical to one initially reported as associated with Cys3531. Three silent mutations were detected also: T3540T, N3542N and T3552T. Analysis of lipid profiles of R3531C families showed, as with the R3500Q mutation, variable expression of the phenotype, modulated by environmental and other genetic factors. Both mutations tend to produce lower plasma levels of LDL in affected subjects than do defects of the LDL receptor (familial hypercholesterolemia, FH). This study shows that the Cys(3531) LDL particles are not only defective at binding to the LDL receptor, as determined by two separate methods, but that in all cases they accumulate preferentially compared to the normal allotype.-Pullinger, C. R., D. Gaffney, M. M. Gutierrez, M. J. Malloy, V. N. Schumaker, C. J. Packard, and J. P. Kane. Apolipoprotein B R3531C mutation: characteristics of 24 subjects from 9 kindreds. .

Hematologic and serum biochemical variables and plasma corticotropin concentration in healthy aged horses

OBJECTIVES

To compare hematologic and serum biochemical variables and plasma ACTH concentration between healthy horses 5 to 12 years old and those more than 20 years old.

ANIMALS

30 healthy horses 5 to 12 years old and 30 healthy horses more than 20 years old.

PROCEDURES

Venous blood was collected from all horses, and CBC and serum biochemical analysis were performed for each horse. Plasma ACTH concentration was determined by radioimmunoassay. Student's paired t-test or the Mann-Whitney rank sum test was used to compare values between control and aged horse groups.

RESULTS

Compared with values for control horses, aged horses had significantly higher erythrocyte mean cell volume and mean cell hemoglobin. Aged horses also had significantly decreased total lymphocyte count. Five aged horses had lymphocyte count that was lower than the low reference limit as established for horses in our laboratory. Differences between control and aged horses for serum biochemical or plasma ACTH values were not significant.

CONCLUSION

Compared with younger adult horses, those more than 20 years old have some hematologic differences, but there is no apparent effect of aging on baseline plasma ACTH concentration.

CLINICAL RELEVANCE

It is important to establish age-matched control values for optimal interpretation of clinicopathologic variables.

Myosin conformational states determined by single fluorophore polarization

Muscle contraction is powered by the interaction of the molecular motor myosin with actin. With new techniques for single molecule manipulation and fluorescence detection, it is now possible to correlate, within the same molecule and in real time, conformational states and mechanical function of myosin. A spot-confocal microscope, capable of detecting single fluorophore polarization, was developed to measure orientational states in the smooth muscle myosin light chain domain during the process of motion generation. Fluorescently labeled turkey gizzard smooth muscle myosin was prepared by removal of endogenous regulatory light chain and re-addition of the light chain labeled at cysteine-108 with the 6-isomer of iodoacetamidotetramethylrhodamine (6-IATR). Single myosin molecule fluorescence polarization data, obtained in a motility assay, provide direct evidence that the myosin light chain domain adopts at least two orientational states during the cyclic interaction of myosin with actin, a randomly disordered state, most likely associated with myosin whereas weakly bound to actin, and an ordered state in which the light chain domain adopts a finite angular orientation whereas strongly bound after the powerstroke.

Identification of a common low density lipoprotein receptor mutation (C163Y) in the west of Scotland

Familial hypercholesterolaemia (FH) is an autosomal codominant disorder characterised by high levels of LDL cholesterol and a high incidence of coronary artery disease. Our aims were to track the low density lipoprotein receptor (LDLR) gene in individual families with phenotypic FH and to identify and characterise any mutations of the LDLR gene that may be common in the west of Scotland FH population using single strand conformational polymorphism analysis (SSCP). Patient samples consisted of 80 heterozygous probands with FH, 200 subjects who were related to the probands, and a further 50 normal, unrelated control subjects. Tracking of the LDLR gene was accomplished by amplification of a 19 allele tetranucleotide microsatellite that is tightly linked to the LDLR gene locus. Primers specific for exon 4 of the LDLR gene were used to amplify genomic DNA and used for SSCP analysis. Any PCR products with different migration patterns as assessed by SSCP were then sequenced directly. In addition to identifying probands with a common mutation, family members were screened using a forced restriction site assay and analysed using microplate array diagonal gel electrophoresis (MADGE). Microsatellite D19S394 analysis was informative in 20 of 23 families studied. In these families there was no inconsistency with segregation of the FH phenotype with the LDLR locus. Of the FH probands, 15/80 had a mutant allele as assessed by SSCP using three pairs of primers covering the whole of exon 4 of the LDLR gene. Direct DNA sequencing showed that 7/15 of the probands had a C163Y mutation. Using a PCR induced restriction site assay for the enzyme RsaI and MADGE, it was determined that the C163Y mutation cosegregated with the FH phenotype in family members of the FH probands. This mutant allele was not present in any of the control subjects. Microsatellite analysis has proven useful in tracking the LDLR gene and could be used in conjunction with LDL cholesterol levels to diagnose FH, especially in children and young adults where phenotypic diagnosis can be difficult.

Influence of polymorphism Q3405E and mutation A3371V in the apolipoprotein B gene on LDL receptor binding

Familial defective apolipoprotein B (FDB) is due to mutations in the apolipoprotein B (apo B) gene at codon 3500 or 3531 that affect low density lipoprotein (LDL) receptor binding. From sequence analysis the putative receptor binding site was believed originally to be upstream from this at residues 3147-3157 and 3357-3367. Using denaturing gradient gel electrophoresis, mutations were sought in codons 3350-3466. This includes the important positively charged residues 3357-3367. DNA from 928 hyperlipidaemic individuals was studied and two hitherto unknown DNA changes were discovered, one of which resulted in an altered amino acid in the apo B. A known polymorphism Q3405E was also detected at a carrier frequency of 1.4%. Using growth of U937 cells as a measure of binding affinity of LDL to its receptor the newly discovered mutant A3371V permitted the same growth as LDL from normolipidaemic individuals of the U937 cells, however, the LDL from Q3405E individuals permitted only 77% of the normal growth (P=0.009).

Acute services. Time to strip the beds?

The health authority and trust proposals for Birmingham's health services, currently the subject of consultation, are radical, untested and uncosted. They assume that once emergency assessment and ambulatory care centres are operational, under half the current caseload will need inpatient stays. University Hospital Birmingham trust's proposal for a new hospital built and operated by the private sector assumes no growth in activity and a 17 per cent reduction in the present bed complement, at a time when emergency admissions in Birmingham are increasing by 5 per cent a year. Analysis of the proposals suggests they will destabilise an already precarious acute service in Birmingham.

Independent mutations at codon 3500 of the apolipoprotein B gene are associated with hyperlipidemia

The apoB arginine-to glutamine change at codon 3500 has become established as a cause of failure of binding of the LDL particle to its receptor and the consequent hypercholesterolemia of familial defective apoB 100. A search for further similar mutations was undertaken by systematic screening of a candidate region of the apoB gene from individuals with hypercholesterolemia. Polymerase chain reaction and denaturing gradient gel electrophoresis were used. We describe two families in which a different mutation in the codon 3500 causes an arginine-to-tryptophan substitution. Most adults in these families who have this mutation have hypercholesterolemia. LDL derived from all who have inherited the mutation is dysfunctional in that it allows only poor growth of an LDL cholesterol-dependent cell line. We conclude that this arginine 3500 is essential to the function of apoB and that its loss and replacement by glutamine or tryptophan is responsible for the hypercholesterolemia of familial defective apoB 100.

Use of a stable copper isotope (65Cu) in the differential diagnosis of Wilson's disease

1. 65Cu/63Cu stable-isotope ratios have been measured in blood serum after oral administration of the stable isotope 65Cu. The incorporation of the isotope into the plasma protein pool was followed at various times for up to 3 days. The resulting patterns of enrichment in healthy control subjects, in Wilson's disease patients and in heterozygotes for the Wilson's disease gene, were similar in appearance to those found by others using copper radioactive isotopes. After an initially high enrichment at 2 h after dosage, the Wilson's disease cases, in contrast to the control subjects, did not show a secondary rise in isotope enrichment of the plasma pool after 72 h, demonstrating a failure to incorporate copper into caeruloplasmin. The Wilson's disease heterozygotes had variable degrees of impairment of isotope incorporation, not always distinguished from those of control subjects. 2. The stability of the isotope also permits the copper tracer to be followed for a longer period. Ten healthy subjects were studied for over 40 days, allowing the biological half-time of an oral dose of copper to be determined (median 18.5 days, 95% confidence interval 14-26 days). Known heterozygotes for the Wilson's disease gene were found to have a significantly increased biological half-time for removal of copper from the plasma pool (median 43 days, 95% confidence interval 32-77 days). 3. The incorporation of 65 Cu in patients with diseases of the liver (other than Wilson's disease) was found to be similar to that in control subjects, aiding differential diagnosis.

Homozygous MHC genotypes and longevity

To investigate the relevance of the major histocompatibility complex (MHC) in longevity, we carried out a molecular analysis of the MHC in 432 unrelated healthy individuals. The comparison of individuals < or = 25 years and > 25 years showed that the 5.8-kb DQA1 allele, which corresponds to HLA-DR53, was negatively associated with longevity (p = 0.0035) resulting mainly from decreased homozygosity with age for that allele (p = 0.008), and restricted to males (p = 0.008). The difference was more striking for the 5.8 kb DQA1: 9.0 kb HSP70 haplotype again only in males (26.3 vs. 6.2%; p = 0.017, OR = 5.4, 95% CI = 1.5 - 19.5). The oldest male subject homozygous for this DQA1: HSP70 haplotype was 54 years (p = 0.005). Comparing leukemic patients and healthy individuals with the same ethnic and geographical origin, homozygosity for these genotypes was more frequent in the young leukemic group. The results suggested the existence of recessive deleterious genes in a segment of HLA-DR53 haplotypes.

Regulation of plasma HDL cholesterol and subfraction distribution by genetic and environmental factors. Associations between the TaqI B RFLP in the CETP gene and smoking and obesity

This study investigated in a healthy population (n = 220) the association of the TaqI B restriction fragment length polymorphism (RFLP) in the cholesteryl ester transfer protein (CETP) gene with plasma high-density lipoprotein (HDL) cholesterol concentration and subfraction distribution. A raised HDL cholesterol level was found in B2B2 homozygotes (B2 cutting site absent) and was associated specifically with a 45% increase in HDL2 compared with B1B1 homozygotes (B1B1, 77 +/- 39 mg/100 mL, mean +/- SD; B2B2, 112 +/- 59 mg/100 mL; P < 0.01). Total plasma, very-low-density lipoprotein, and HDL triglyceride levels did not differ among the genotype groups, nor did plasma apolipoprotein AI levels (B1B1, 1.45 +/- 0.35 mg/mL, mean +/- SD; B2B2, 1.56 +/- 0.33 mg/mL). Thus, the genetic variation appeared to be independent of metabolic factors that are known to regulate HDL levels. Plasma CETP exchange activity was unlikely to be the cause of the association, since it did not differ between genotype groups and was not correlated with HDL2 concentration. Multivariate analysis demonstrated that the TaqI B polymorphism had an effect on HDL cholesterol and HDL2 that was independent of age, sex, body mass index, oral contraceptive use, exercise, alcohol consumption, and plasma triglycerides. In smokers, the presence of the B2B2 genotype did not result in increased HDL cholesterol or HDL2, whereas in obese subjects, the difference between B1B1 and B2B2 individuals was diminished. We conclude that the TaqI B RFLP is associated with a quantitatively significant effect on plasma HDL2 levels that is independent of plasma triglycerides and interacts with lifestyle factors.

Children's lives or garden aesthetics? A case study in public health advocacy

Following a decade of accumulating clinical reports on child drowning in domestic swimming pools, paediatricians began advocating legislation that would require all pools to be 'isolation' fenced. In 1990, the New South Wales Government introduced and then repeated such legislation following intense lobbying and media advocacy from a group of pool owners. This paper reviews the ways in which isolation fence advocates and opponents framed their public arguments. Five main areas of competing public discourse are identified: why pool drownings occur; the effects of fencing; expert views and community support; the role of the state in prevention; and personalised references to the value systems of those involved in the debate. Two factors seem likely to have contributed most to the overthrow of the legislation: fence opponents inhabiting the same noninterventionist ideological frame of reference as the government; and fence advocates' refusal to compromise on retrospective fencing seems likely to have inspired a commitment in opposition which would have been absent if an incrementalist, prospective fencing policy had been adopted.