Exclusion of linkage of Shwachman-Diamond syndrome to chromosome regions 6q and 12q implicated by a de novo translocation

Shwachman-Diamond syndrome is a rare genetic disorder of unknown pathogenesis involving exocrine pancreatic insufficiency and hematological and skeletal abnormalities. There is broad clinical variability; the extent of heterogeneity is unknown but comparisons within a large cohort of patients show no striking differences between patients of families with single or multiple affected offspring. Segregation analysis of a cohort of 69 families has suggested an autosomal recessive mode of inheritance. A single constitutional de novo chromosome rearrangement was reported in a Japanese patient involving a balanced translocation, t(6;12)(q16.2;q21.2), thereby suggesting possible loci for a genetic defect. Evenly spaced microsatellite markers spanning 26-32 cM intervals from D6S1056 to D6S304 and D12S375 to D12S346 were analyzed for linkage in members of 13 Shwachman-Diamond syndrome families with two or three affected children. Two-point lod scores were calculated for each marker under assumptions of recessive inheritance and complete penetrance. Negative lod scores indicated exclusion of both chromosome regions. Further, affected sibs were discordant for inheritance of chromosomes in most families based on constructed haplotypes. The cytogenetic abnormality is not associated with most cases of Shwachman-Diamond syndrome.

A PC12 variant lacking regulated secretory organelles: aberrant protein targeting and evidence for a factor inhibiting neuroendocrine gene expression

A variant of the PC12 pheochromocytoma cell line (termed A35C) has been isolated that lacks regulated secretory organelles and several constituent proteins. Northern and Southern blot analyses suggested a block at the transcriptional level. The proprotein-converting enzyme carboxypeptidase H was synthesised in the A35C cell line but was secreted by the constitutive pathway. Transient transfection of A35C cells with cDNAs encoding the regulated secretory proteins dopamine beta-hydroxylase and synaptotagmin I resulted in distinct patterns of mistargeting of these proteins. It is surprising that hybrid cells created by fusing normal PC12 cells with A35C cells exhibited the variant phenotype, suggesting that A35C cells express an inhibitory factor that represses neuroendocrine-specific gene expression.

Sweat production and localisation of carbonic anhydrase in the equine sweat gland during exercise at two ambient temperatures

The aim of this investigation was to study sweat production during exercise at 2 ambient temperatures (20 degrees C and 35 degrees C) and the concurrent localisation of carbonic anhydrase (CA) in the sweat gland. Horses develop alkalosis during prolonged exercise and the sweat contains HCO3-. Carbonic anhydrase is therefore of interest since it catalyses the reaction CO2 + H2O<-->HCO3- + H+. Four standardbred trotters performed an exercise test. Skin biopsies were taken from the neck, and sweat rate, blood and skin temperatures were measured. There was a close relationship between sweat rate, temperatures and work intensity at 20 degrees C. Temperatures and sweat rate were higher at 35 degrees C and did not fall when the work intensity dropped. A significant decrease in the sweat gland cell area was found after exercise at 35 degrees C with an accompanying decrease of vesicles. Strong CA activity was present at the luminal cell membrane and weaker basolaterally. The staining intensity increased after exercise. We suggest that CA might be of importance for counteracting the alkalosis developed after exercise by delivering HCO3- for generation of the alkaline pH in sweat.

The maternal DDK syndrome phenotype is determined by modifier genes that are not linked to Om

The DDK syndrome is a polar, early embryonic lethal phenotype caused by incompatibility between a maternal factor of DDK origin and a paternal gene of non-DDK origin. Both maternal factor and paternal gene have been mapped to the Om locus on mouse Chromosome (Chr) 11. The paternal contribution to the syndrome has been shown to segregate as a single locus. Although the inheritance of the maternal contribution has not been characterized in depth, it as been assumed to segregate as a single locus. We have now characterized the segregation of the DDK fertility phenotype in over 240 females. Our results demonstrate that females require at least one DDK allele at Om to manifest the syndrome. However, the DDK syndrome inter-strain cross-fertility phenotype of heterozygous females is highly variable and spans the gamut from completely infertile to completely fertile. Our results indicate that this phenotypic variability has a genetic basis and that the modifiers of the DDK syndrome segregate independently of Om.

A pilot study of melphalan, tumor necrosis factor-alpha and 41.8 degrees C whole-body hyperthermia

PURPOSE

To evaluate the feasibilitv of sequencing (based on preclinical modeling) tumor necrosis factor-a (TNF) at two dose levels with melphalan (L-PAM) and 41.8 C whole-body hyperthermia (WBH) for 60 min.

PATIENTS AND METHODS

Nine patients with refractory cancer were treated from October 1995 to June 1997. The study encompassed a total of 20 trimodality treatment courses. Three patients were treated at TNF dose level I (50 microg/m2) and six patients were treated at TNF dose level II (100 microg/m2). TNF was delivered as a 24-h intravenous infusion, 48 h prior to the combination of L-PAM and WBH; L-PAM was given over 10 min at target temperature at a dose of 17.5 mg/ m2 based on a previous phase I WBH/L-PAM trial. WBH was administered with an Aquatherm radiant heat device.

RESULTS

Myelosuppression was the major toxicity associated with therapy, but there were no instances of bleeding or neutropenic fevers. Grade 3 thrombocytopenia was seen with 15% of treatments. Regarding absolute neutrophil count, 15% of treatments were associated with grade 3 toxicity, and 45% with grade 4 toxicity, and regarding white blood cell count, 50% of treatments were associated with grade 3 toxicity and 10% with grade 4 toxicity. The myelosuppression observed was equivalent to that seen in our earlier phase I study of WBH and L-PAM (without TNF). Only mild toxicities (grade 1 or 2) were associated with TNF; these were seen with <25% of treatments and included nausea, vomiting, diarrhea, fevers, and headache. There were no instances of hypotension. There was no relationship between toxicities observed and the two TNF dose levels. Mild WBH toxicities were seen with less than 15% of treatments; these included nausea, vomiting, and herpes simplex I. Responses included two complete remissions (malignant melanoma, TNF dose level I; breast cancer, TNF dose level II), and two disease stabilizations (both malignant melanoma, TNF dose level I).

CONCLUSION

We conclude that the combination of TNF, L-PAM, and WBH is well tolerated at the dose levels studied. The clinical results justify further clinical investigation for this trimodality treatment approach.

Location score and haplotype analyses of the locus for autosomal recessive spastic ataxia of Charlevoix-Saguenay, in chromosome region 13q11

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a clinically homogeneous form of early-onset familial spastic ataxia with prominent myelinated retinal nerve fibers. More than 300 patients have been identified, and most of their families originated in the Charlevoix-Saguenay region of northeastern Quebec, where the carrier prevalence has been estimated to be 1/22. Consistent with the hypothesis of a founder effect, we observed excess shared homozygosity at 13q11, among patients in a genomewide scan of 12 families. Analysis of 19 pedigrees demonstrated very tight linkage between the ARSACS locus and an intragenic polymorphism of the gamma-sarcoglycan (SGCG) gene, but genomic DNA sequence analysis of all eight exons of SGCG revealed no disease-causing mutation. On the basis of haplotypes composed of seven marker loci that spanned 11.1 cM, the most likely position of the ARSACS locus was 0.42 cM distal to the SGCG polymorphism. Two groups of ARSACS-associated haplotypes were identified: a large group that carries a common SGCG allele and a small group that carries a rare SGCG allele. The haplotype groups do not appear to be closely related. Therefore, although chromosomes within each haplotype group may harbor a single ARSACS mutation identical by descent, the two mutations could have independent origins.

Differential risk factor profiles for indoor and outdoor falls in older people living at home in Nottingham, UK

The objectives of this work were: to estimate the incidence of falls within an at-risk group of community-dwelling elderly people; to assess the risk factors associated with incident falls; to examine the effects of incident falls on survival. A random sample of 1042 community-dwelling older people in Nottingham (UK) were interviewed in 1985 and survivors re-interviewed at 4-year follow-up. The at-risk group was defined as survivors who had not fallen in the year prior to the baseline interview (n = 444). One-year fall recall was assessed using a questionnaire and included physical health, mobility, prescribed drugs and time spent walking. Body-weight and handgrip strength were measured. Eight-year post-fall mortality was recorded. In 1989 117 new fallers were identified. These people fell a total of 233 times in the year prior to re-interview (incidence rate: 524.8 per 1000 person-years at risk; 95% confidence intervals (CI): 473.3-576.3). People aged less than 75 were more likely to fall outdoors than people aged 75 and over (chi2 = 5.715, df = 1, p = 0.017). Risk factors associated with falling were: being less healthy (odds ratio (OR): 0.55; p = 0.052); having a walking speed in the range stroll/very slow/nonambulant compared with normal/brisk/fast (OR: 1.99; p<0.01); and number of prescribed drugs (OR: 1.30; p = 0.01). When analysed separately, indoor and outdoor falls presented differential risk profiles, with evidence that indoor falls were associated with frailty, while outdoor falls were associated with compromised health status in more active people. In 8-year post-fall monitoring, multiple (3+) fallers and indoor fallers showed a significant excess mortality. The differences in risk factors for, and prognoses following, indoor and outdoor falls, emphasise the complex interactions between intrinsic and extrinsic factors associated with falling among older people.

Expression of functional angiotensin-converting enzyme and AT1 receptors in cultured human cardiac fibroblasts

BACKGROUND

Angiotensin II (Ang II) has been implicated in the development of cardiac fibrosis. The aims of the present study were to examine expression and activity of ACE and of angiotensin receptors in human cardiac fibroblasts cultured from dilated cardiomyopathic and ischemic hearts. The effects of Ang II on fibroblasts were also investigated.

METHODS AND RESULTS

Human cardiac fibroblasts were cultured from ventricular and atrial myocardium and characterized immunohistochemically. Expression of ACE and the angiotensin AT1 receptor was demonstrated in cardiac fibroblasts by reverse transcriptase-polymerase chain reaction and radioligand binding. Functional ACE activity, measured by radiolabeled substrate conversion assay, was detected in both ventricular (Vmax. Km-1. mg-1, 0.031+/-0.010; n=13) and atrial (0. 034+/-0.012; n=6) fibroblasts. Fibroblast ACE activity was increased after 48 hours of treatment with basic fibroblast growth factor, dexamethasone, and phorbol ester. Ang II did not affect DNA synthesis but stimulated [3H]proline incorporation in cardiac fibroblasts (20.0+/-4.0% increase above control by 10 micromol/L; P<0.05, n=7), which was abolished by losartan 10 micromol/L but not PD123319 1 micromol/L. Ang II also stimulated a rise in intracellular calcium (basal, 56+/-1 nmol/L; Ang II, 355+/-24 nmol/L) via the AT1 receptor, as shown by complete inhibition with losartan.

CONCLUSIONS

We have demonstrated expression and activity of ACE and AT1 receptor in cultured human cardiac fibroblasts. In addition, cardiac fibroblasts respond to Ang II with AT1 receptor-mediated collagen synthesis. The presence of local ACE and AT1 receptors in human fibroblasts suggests their involvement in the development of cardiac fibrosis.

Genetic risk factors in Alzheimer's disease

Following a brief introduction and discussion of the pathological features of Alzheimer's disease, the main emphasis of this review article will be the genetic factors that have been implicated in this disease. These can be divided into two main categories. First, the three genes in which mutations are known to result in early onset autosomal dominant familial Alzheimer's disease will be discussed. These are well characterised but account for only a small proportion of Alzheimer's disease cases. Late onset, sporadic Alzheimer's disease is more common and evidence suggests that there is a genetic component to this type of disease. A number of genetic risk factors have been implicated that might increase the risk of developing sporadic disease. Many of these are controversial and studies have shown conflicting results, which are discussed in this section. Finally, a brief discussion of some of the mechanisms suggested to play a role in the pathogenesis of Alzheimer's disease is included. It is hoped that this will show why particular genes have been implicated in Alzheimer's disease and how they might be able to influence the development of the disease.

Stability and change in levels of habitual physical activity in later life

OBJECTIVES

to describe stability and change in levels of customary physical activity assessed in recall-based questionnaire surveys of older people conducted in 1985, 1989 and 1993.

DESIGN

longitudinal study.

SUBJECTS

1042 people originally aged 65 and over randomly sampled from general practitioner lists in Nottingham, UK.

METHODS

logistic and multiple regression analyses, intraclass correlation coefficients.

MAIN OUTCOME MEASURES

self-reported time spent per day walking and shopping; self-reported time spent per week in other indoor, outdoor and leisure activities; frequency of performance of strength and flexibility activities.

RESULTS

among survivors, activity levels at baseline tended to be higher than those of their non-surviving peers. Overall, 8-year change between 1985 and 1993 was characterized by progressively declining activity levels. Nevertheless, in both trajectories and stability profiles, differences did emerge among the seven activity categories studied. At least one in four respondents increased the time they spent walking, and approximately one in three respondents increased the time they spent shopping between 1985 and 1993.

CONCLUSIONS

these findings suggest that, while some activity variables show levels of stability consistent with trait-like constructs, others are clearly more labile. While the present data cannot offer a definitive explanation for these differences, it seems reasonable that within each activity the influence of ability, opportunity and need interact to determine levels of participation.

Customary physical activity and physical health outcomes in later life

OBJECTIVES

to explore associations between customary physical activity and three longitudinal outcomes: 12-year all-cause mortality, 12-year disease-specific mortality and 8-year change in general practitioner and personal social service use.

DESIGN

longitudinal study.

SUBJECTS

1042 people originally aged 65 and over randomly sampled from general practitioner lists in Nottingham, UK.

METHODS

Cox regression survival and logistic regression analyses.

MAIN OUTCOME MEASURES

questionnaire-assessed levels of physical activity; 12-year mortality; reported health and personal social service contacts in month prior to interview.

RESULTS

on the basis of factor scores derived from the interview questionnaire, activity levels were graded as high, intermediate or low, with respondents grouped accordingly. Relative to the high activity group, 12-year mortality was significantly increased in both the intermediate [adjusted hazard ratio (HR) = 1.53; 95% confidence interval (CI) = 1.10-2.14; P < 0.05] and low (HR = 1.75; 95% CI = 1.24-2.48; P < 0.005) activity groups for men, and in the low activity group (HR= 1.73; 95% CI = 1.28-2.33; P < 0.001) for women. Lower levels of activity were also associated with an increased likelihood of using health and personal social services 8 years after the initial interview, and an increased risk among men of having respiratory disease recorded as the primary cause of death. All models were adjusted for age, health and smoking status and weight category as measured at baseline.

CONCLUSIONS

the results are consistent with the conclusion that, among elderly people, health gain resulting from higher customary physical activity levels can promote a longer and more independent later life.

Customary physical activity and psychological wellbeing: a longitudinal study

OBJECTIVES

to assess longitudinal relationships between habitual levels of physical activity and indices of psychological wellbeing in older people.

DESIGN

baseline assessment with 4- and 8-year follow-ups.

SUBJECTS

1042 people originally aged 65 and over randomly sampled from general practitioner lists in Nottingham, UK.

METHODS

logistic regression analysis of selected T1 (1985) and T2 (1989) variables, with depression at T2 as dependent; multiple regression analyses of selected T1, T2 and T3 (1993) variables, with life satisfaction at T2 (model 1) or T3 (model 2) as dependent.

MAIN OUTCOME MEASURES

questionnaire-assessed levels of physical activity; 14-item Symptoms of Anxiety and Depression scale; 13-item Life Satisfaction Index; health, demographic and social activity variables.

RESULTS

in the logistic regression model, depression at T2 was most strongly associated with depression [odds ratio (OR) = 7.13; 95% confidence interval (CI) = 3.25-15.64; P < 0.001] and lower physical health status (OR = 1.26 per unit change in score; 95% CI = 1.17-1.42; P < 0.001) at T1. Lower levels of outdoor/leisure activities at T1 were also associated with some increased risk of depression 4 years later (OR = 0.92 per hour of activity; 95% CI = 0.85-0.99; P < 0.05). Similar predictive patterns emerged from the multiple regression analyses where, in both models, earlier levels of life satisfaction, social engagement and health accounted for most of the explained variance in life satisfaction (R2 = 0.42 for model 1; R2 = 0.35 for model 2). Again, however, earlier levels of physical activity (as walking and housework) did contribute significantly, although modestly, to longitudinal changes in morale.

CONCLUSIONS

while the results provide some support for the conclusion that physical activity contributes independently to the promotion and maintenance of psychological wellbeing in later life, this contribution is, at best, extremely modest.

Characterization of two corneal epithelium-derived antigens associated with vasculitis

PURPOSE

In a previous investigation into corneal autoimmunity, it was demonstrated that a putative autoantigen, a protein of 66 kDa, present in bovine corneal epithelium, binds circulating autoantibodies in approximately 60% of patients with Wegener's granulomatosis (WG). The aim of the present study was to characterize and identify the 66-kDa protein.

METHODS

A purification protocol was established for the 66-kDa protein using standard chromatography techniques. During the purification procedure it became clear that the 66-kDa protein detected in patients' sera was in fact two proteins, both running at 66 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, that eluted in different fractions on DE-52 chromatography columns. These two proteins have been labeled bovine corneal epithelial antigen-A and -B (BCEA-A and BCEA-B). Further investigations of antibody binding have demonstrated that patients' sera bind to either one or the other of these proteins with no cross-reactivity between them. Separated BCEA-A and BCEA-B protein extracts were immunoblotted with 27 WG patients' sera, 10 Churg-Strauss syndrome (CSS) patients' sera, 31 rheumatoid arthritis (RA) patients' sera, and 40 healthy control subjects' sera from the blood bank.

RESULTS

Forty-six percent of WG patients' sera had antibodies to one of the 66-kDa antigens, whereas none of the healthy control subjects' sera had 66-kDa antibodies (P < 10(-5)). In the WG group, 31% were positive to BCEA-A (versus controls, P = 0.0023), and 15% were positive to BCEA-B. WG patients with peripheral ulcerative keratitis (PUK) had a significant association with anti-BCEA-A antibodies when compared with healthy control subjects (50%, P < 10(-6)). However, in the RA group with no eye disease there was an association with BCEA-A (25%, P = 0.011) but not in the RA group with PUK. The frequency of anti-BCEA-B antibodies was significantly increased in patients with CSS (60%, P < 10(-7)).

CONCLUSIONS

In summary, it has been shown that vasculitis patients have antibodies to two 66-kDa corneal antigens and that autoantibodies to these antigens are mutually exclusive. It has also been shown that antibodies to BCEA-B are associated with CSS, whereas BCEA-A antibodies are associated with WG and RA.

The Nottingham Longitudinal Study of Activity and Ageing: a methodological overview

OBJECTIVES

first, to describe the background and methodological approach to the assessment of customary physical activity, health and psycho-social status used by the Nottingham Longitudinal Study of Activity and Ageing; second, to provide information on the sampling strategy and survey response rates for three waves of data collection; and, third, to provide information on the reliability and validity of the survey assessments.

DESIGN

longitudinal study.

SUBJECTS

1042 people originally aged 65 and over, randomly sampled from general practitioner lists in Nottingham, UK.

METHODS

a descriptive overview of response rates (%), instrument reliability (alpha coefficients) and intercorrelations among measured outcomes (correlation coefficients and principal components analysis).

MAIN OUTCOME MEASURES

questionnaire-assessed levels of physical activity; instrumental measurements of handgrip strength, weight, demi-span and shoulder flexibility; brief assessments of depression, social engagement, life-satisfaction and cognitive impairment.

RESULTS

the study achieved a baseline (TI) response rate of 80%, with re-interview rates of 88% and 73% for T2 (1989) and T3 (1993) surveys respectively. For both men and women, factor scores derived from first principal components extracted from T1 survey data showed significant (r > or = 0.4; P < 0.001) product moment correlations with instrumental measurements of handgrip strength and shoulder flexibility. All the brief assessment measures showed satisfactory levels of reliability (alpha > or = 0.7).

Founder BRCA1 and BRCA2 mutations in French Canadian breast and ovarian cancer families

We have identified four mutations in each of the breast cancer-susceptibility genes, BRCA1 and BRCA2, in French Canadian breast cancer and breast/ovarian cancer families from Quebec. To identify founder effects, we examined independently ascertained French Canadian cancer families for the distribution of these eight mutations. Mutations were found in 41 of 97 families. Six of eight mutations were observed at least twice. The BRCA1 C4446T mutation was the most common mutation found, followed by the BRCA2 8765delAG mutation. Together, these mutations were found in 28 of 41 families identified to have a mutation. The odds of detection of any of the four BRCA1 mutations was 18.7x greater if one or more cases of ovarian cancer were also present in the family. The odds of detection of any of the four BRCA2 mutations was 5.3x greater if there were at least five cases of breast cancer in the family. Interestingly, the presence of a breast cancer case <36 years of age was strongly predictive of the presence of any of the eight mutations screened. Carriers of the same mutation, from different families, shared similar haplotypes, indicating that the mutant alleles were likely to be identical by descent for a mutation in the founder population. The identification of common BRCA1 and BRCA2 mutations will facilitate carrier detection in French Canadian breast cancer and breast/ovarian cancer families.

Food safety knowledge and practice among elderly people living at home

OBJECTIVE

To assess the food storage knowledge and practice of elderly people living at home.

METHODS

Three phase survey data collection: face to face interviews; dietary diaries with a food frequency questionnaire; and follow up interviews.

SETTING

Urban Nottingham.

PARTICIPANTS

809 elderly people (aged 65+) randomly selected from general practitioner lists.

MAIN OUTCOME MEASURES

Respondent's refrigerator temperature; knowledge of freezer star rating; understanding of "use by" and "sell by" dates; reported ability to read food product safety labels.

RESULTS

From a weighted total of 645 refrigerators measured, 451 (70%) were too warm for the safe storage of food (> or = 6 degrees Celsius). Only 41% of respondents (n = 279) knew the star rating of their freezer. Within a smaller sub-sample knowledge of the "use by" and "sell by" dates was good, but 45% of these respondents reported difficulty reading food labels. The storage of foods at inappropriate temperatures was not independent of socioeconomic or demographic status, and tended to be more likely among the poorer and those not living alone.

CONCLUSIONS

Food storage practices among the majority of elderly people interviewed in this study do not meet recommended safety standards to minimise the risk of food poisoning.

Genetic mapping of X-linked loci involved in skewing of X chromosome inactivation in the human

We have analyzed X-chromosome inactivation patterns in lymphocytes of 264 females from 38 families not known to have any genetic disease. Quantitative measures of X-inactivation showed strong sister-sister correlation in the degree of departure from equal numbers of cells having each X chromosome active, suggesting heritability of this phenotype. Strong sister-sister correlation was also observed for the fraction of cells having the same parent's X chromosome active, consistent with the possibility that this trait might be controlled by a cis-acting, X-linked gene. We used a sib-pair approach to determine whether X-inactivation phenotype was linked to loci in any region of the X chromosome. Both quantitative and discrete measures of X-inactivation phenotype showed evidence of linkage to markers in the region of the X inactivation center (XIC). The quantitative measure of X-inactivation phenotype used in our study also showed linkage to loci at Xq25-q26. This study provides the first evidence for X-linked inheritance of X chromosome inactivation phenotype derived from linkage analysis in phenotypically normal human families.

Fruit and vegetable consumption in later life

OBJECTIVE

to assess levels of fruit and vegetable consumption in elderly people, and to examine the socio-economic, physical and psychological factors which influence this consumption.

METHODS

a three-phase survey: face to face interviews; self-completed dietary diaries with a food frequency questionnaire; and follow-up face-to-face interviews.

PARTICIPANTS

445 elderly people (aged 65+) randomly selected from general practitioner lists in urban Nottingham and rural Nottinghamshire, Lincolnshire and Leicestershire.

RESULTS

the recommended target of five portions of fruit and vegetables a day was achieved by less than half the respondents: 37% of those living in the urban area and 51% of those living in the rural area. Low fruit and vegetable consumption was particularly associated with being male, smoking and having low levels of social engagement.

CONCLUSIONS

most elderly people consume less than the recommended levels of fruit and vegetables. Health programmes promoting fruit and vegetable consumption may not be successfully reaching elderly people and need to target those particularly at risk of low consumption.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay

A form of autosomal recessive spastic ataxia unique to the Charlevoix-Saguenay area was clinically identified 20 years ago in patients from that region. This region of Québec, Canada, was once considered a genetic isolate. First noted at gait initiation, signs of ataxia slowly progress along with spasticity of the four limbs, slurred speech, and followed by distal amyotrophy. Early diagnosis relies on the presence of prominent myelinated fibers embedding retinal blood vessels at funduscopy and marked saccadic alteration of ocular smooth pursuit. Imaging of the posterior fossa shows cerebellar vermis atrophy and nerve conduction studies reveal loss of sensory and reduced motor conduction velocities. The clinical features are consistent with a developmental defect in myelination of both retinal and peripheral nerve fibers. The cause of this defect and the progressive axonal degeneration in the corticospinal and spinocerebellar tracts, as well as in the peripheral nerves is still unknown. Results of recent molecular genetic linkage analysis have located the gene locus to chromosome 13q12. Further research is needed to define where this hereditary spastic ataxia stands in the classification of the early onset spinocerebellar degenerations.

Association and linkage of LDLR gene variation with variation in plasma low density lipoprotein cholesterol

The role of common variation in the low density lipoprotein (LDL) receptor gene (LDLR) as a determinant of variation in plasma LDL cholesterol in normolipidemic populations is not well established. To address this question, we used both association and linkage analysis to evaluate the relationship between plasma LDL cholesterol and genetic variation in LDLR and in three other candidate genes for lipoprotein metabolism, namely, APOE, PONI, and LPL. We studied a sample of 719 normolipidemic Alberta Hutterites, who comprised 1217 sib pairs. Variation in each of the four candidate genes was significantly associated with variation in plasma LDL cholesterol, but the average effects of the alleles were small. In contrast, sib pair analysis showed that only the LDLR gene variation was linked with variation in plasma LDL cholesterol (P = 0.026). Thus, the common LDLR gene variation was both associated with and linked to variation in plasma LDL cholesterol, suggesting that there is a functional impact of structural variation in LDLR on plasma LDL cholesterol in this study sample. However, the absence of linkage of variation in LDL cholesterol with the other three candidate genes, in particular APOE, is consistent with a lower sensitivity of linkage analysis compared with association analysis for detecting modest effects on quantitative traits. Attributes such as the genetic structure of the study sample, the amount of variance attributable to the locus, and the information content of the marker appear to affect the ability to detect genotype-phenotype relationships using linkage analysis.

Aging and lymphocyte subpopulations: whole-blood analysis of immune markers in a large population sample of healthy elderly individuals

Immune status was determined in a representative sample of elderly people by measuring lymphocyte subsets in whole-blood samples as part of an epidemiological study of the population aged 65 and over. Venepuncture was undertaken in more than 500 individuals who took part in an extensive interview that focused on the lifestyle and psychosocial determinants of healthy aging. The results show that median levels of all lymphocyte subsets tend to decline as the age of the sample increases. In the total sample there were significant age effects (p < 0.05) on total lymphocytes, CD3, CD4, and CD19 (B cells); age differences did not reach significance for CD8 and CD57. There were also significant sex differences (p < 0.05) on CD3, CD4, and CD19, and in all cases women had higher values than men. When we selected a particularly healthy subsample who did not report any illness and took no medication, the findings were unchanged. We conclude that the peripheral expression of lymphocytes appears little affected by aging-related illnesses in the general population, but is affected by aging itself. The study provides reference values for the lymphocyte measures, which can be regarded as having greater validity than the values usually cited.

Growth response of human coronary smooth muscle cells to angiotensin II and influence of angiotensin AT1 receptor blockade

BACKGROUND

The renin-angiotensin system has been implicated in the development of vascular wall thickening in cardiovascular disease, through the growth-promoting actions of the vasoconstrictive agent, angiotensin II, on vascular smooth muscle cells.

OBJECTIVE

To investigate the effect of angiotensin II on growth of human coronary artery smooth muscle cells (cSMCs) in culture, and to identify the angiotensin receptor(s) mediating such a response.

METHODS

Human cSMCs were isolated from coronary arteries of recipient hearts obtained during transplantation, and characterized by immunohistochemistry. The effect of angiotensin II on protein synthesis by cSMCs was measured by [3H]leucine incorporation and protein concentration assays. Human cSMC proliferation was assessed by [3H]thymidine incorporation assay and cell count. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect angiotensin receptor expression. Transient increases in intracellular calcium concentration in cSMCs in response to angiotensin II stimulation were visualized under fura-2 fluorescence microscopy.

RESULTS

Angiotensin II (1 nmol/l-10 mumol/l) stimulated protein synthesis in cSMCs (maximum 24 +/- 2% increase in incorporation of [3H]leucine over 48 h; n = 4, P < 0.01). An increase in cellular protein content was also measured. However, angiotensin II had no effect on proliferation of quiescent cSMCs. The increased protein synthesis was completely inhibited by pretreatment with the angiotensin AT1 receptor antagonist, losartan, but not the AT2 receptor antagonist, PD123319. Expression of the angiotensin AT1 receptor subtype was detected in cSMCs by RT-PCR. Angiotensin II stimulation of cells triggered transient increases in intracellular calcium concentration, which were abolished by losartan, but were insensitive to PD123319 and pertussis toxin.

CONCLUSIONS

The results of this study in human coronary VSMCs indicate that angiotensin II and the AT1 receptor may be involved in the development of coronary artery disease in man.