Demystified ... microsatellites

Microsatellite DNA sequences consist of relatively short repeats of one to five base pair units; together with satellites and minisatellites they comprise a larger family known as tandemly repetitive sequences. Microsatellites are found both in prokaryotes and eukaryotes, including humans, wherein they appear scattered almost at random throughout the genome. Although in prokaryotes distinct biological functions have been demonstrated, the role of microsatellites in eukaryotes is less clear. Nevertheless, several interesting hypotheses exist suggesting that certain microsatellites may exert subtle influences on the regulation of gene expression. Although the presence of these subtle mechanisms may be beneficial to a whole population, when they go wrong, as is thought to happen in the case of human trinucleotide repeat associated diseases, such as Huntington's disease, the consequences for the individual can be fatal. Most human microsatellites probably have no biological use at all; however, they are extremely useful in such fields as forensic DNA profiling and genetic linkage analysis, which can be used to search for genes involved in a wide range of disorders. With a primary focus on humans, it is the aim of this review to present an up to date discussion, both of the biological aspects and scientific uses of microsatellite sequences. In the latter case, basic theoretical and technical points will be considered, and as such it may be of use both to laboratory and non-laboratory based readers.

pUB2380: characterization of a ColD-like resistance plasmid

A detailed analysis of the mobilizable, ColE1-like resistance plasmid, pUB2380, is reported. The 8.5-kb genome encodes six (possibly seven) major functions: (1) a ColD-like origin of replication, oriV, with associated replication functions, RNAI and RNAII; (2) a set of active mobilization functions highly homologous to that of ColE1, including the origin of transfer, oriT; (3) a ColE1-like multimer resolution site (cer); (4) a kanamycin-resistance determinant, aph, encoding an aminoglycoside-3'-phosphotransferase type 1; (5) an insertion sequence, IS1294; and (6) two genes, probably cotranscribed, of unknown function(s). The GC content of the various parts of the genome indicates that the plasmid is a hybrid structure assembled from DNA from at least three different sources, of which the replication region, the mobilization functions, and the resistance gene are likely to have originated in the enterobacteriaceae.

IS1294, a DNA element that transposes by RC transposition

IS1294, found on the ColD-like resistance plasmid pUB2380, is IS91-like. It is an active 1.7-kb insertion sequence that lacks terminal inverted repeats, displays insertion-site specificity, and does not generate direct repeats of the target site. The element has one large open reading frame, tnp(1294), encoding a transposase of 351 amino acids, related to members of the REP family of replication proteins used by RC-plasmids of gram-positive bacteria. IS1294 transposes using rolling-circle replication, initiated at one end of the element, oriIS, and terminated at the other, terIS. oriIS and terIS are highly conserved among like IS elements. oriIS resembles the leading strand replication origins of RC-plasmids; terIS resembles a rho-independent transcription terminator. IS1294 mediates not only its own transposition, but also sequences adjacent to terIS. A transposition model for IS1294 and related elements, involving rolling-circle replication and single-strand DNA intermediates, is presented.

Circulating hematopoietic progenitor cells in first trimester fetal blood

The yolk sac and aorto-gonad-mesonephros region are well recognized as the principal sites of hematopoiesis in the developing embryo, and the liver is the principal site of hematopoiesis in the fetus. However, little is known about circulating hematopoietic stem and progenitor cells in early fetal life. We investigated the number and characteristics of circulating progenitors in first trimester blood of 64 human fetuses (median gestational age, 10(+4) weeks; range, 7(+6)-13(+6) weeks). CD34+ cells accounted for 5.1 +/- 1.0% of CD45+ cells in first trimester blood, which is significantly more than in term cord blood (0.4 +/- 0.03%; P =.0015). However, the concentration of CD34+ cells (6.6 +/- 2.4 x 10(4)/mL) was similar to that in term cord blood (5.6 +/- 3.9 x 10(4)/mL). The total number of progenitors cultured from unsorted mononuclear cells (MNCs) in first trimester blood was 19.2 +/- 2.1 x 10(3)/mL, which is similar to that in term cord blood (26.4 +/- 5.6 x 10(3)/mL). All lineages were seen: colony-forming unit-GEMM (CFU-GEMM), CFU-GM, BFU-e, BFU-MK, and CFU-MK. Clonogenic assays of CD34+ cells purified from first trimester samples produced mainly two lineages: BFU-e (39.0 +/- 9.6 x 10(3)/mL CD34+ cells) and CFU-GEMM (22.6 +/- 4.7 x 10(3)/mL CD34+ cells). Short-term liquid culture of first trimester blood MNCs in SCF + IL-3 + Flt-3 (stem cell factor + interleukin-3 + Flt-3) increased, by 7-fold, the numbers of CFU-GEMM and induced a dramatic increase in BFU-e (65.6 +/- 12.1-fold). These data show that significant numbers of committed and multipotent progenitors with capacity for expansion circulate in first trimester fetal blood and can be CD34 selected. These cells should be suitable targets for gene transfer and stem cell transplantation and, because fetal hematopoietic progenitors have been demonstrated in the maternal circulation from early gestation, may also be manipulated for noninvasive prenatal diagnosis of major genetic disorders. (Blood. 2000;95:1967-1972)

Smoking habits in multiple system atrophy and progressive supranuclear palsy. European Study Group on Atypical Parkinsonisms

OBJECTIVE

To evaluate smoking habits in patients with multiple system atrophy (MSA) and progressive supranuclear palsy (PSP) in a multicenter case-control study to determine whether these two forms of atypical parkinsonism share the inverse association with smoking previously found in PD.

BACKGROUND

No epidemiologic studies have been performed on smoking habits in MSA. A previous investigation in PSP revealed no differences in smoking habits between patients and hospital control subjects.

METHODS

Seventy-six MSA patients, 55 PSP patients, 140 PD patients, and 134 healthy control subjects were enrolled consecutively at seven neurologic clinics from January 1, 1994, to July 31, 1998. Detailed information on smoking habits was obtained using a structured questionnaire.

RESULTS

The comparison between frequencies of never-smokers versus ever-smokers (ex-smokers/current smokers; adjusted odds ratio [ORadj], 0.56; 95% CI, 0.29 to 1.06) and a dose-response analysis for never-smokers, moderate smokers (ORadj, 0.64; 95% CI, 0.31 to 1.32), and heavy smokers (ORadj, 0.47; 95% CI, 0.21 to 1.05) suggest that MSA patients smoke less than population control subjects. By contrast, the comparison of frequencies of never-smokers versus ever-smokers (ORadj, 0.91; 95% CI, 0.42 to 1.98) and a dose-response analysis for never-smokers, moderate smokers (ORadj, 0.68; 95% CI, 0.27 to 1.69), and heavy smokers (ORadj, 1.24; CI 95%, 0.51 to 3.06) revealed no differences in smoking habits between PSP patients and population control subjects.

CONCLUSIONS

The fact that the inverse association with smoking found previously in PD is shared by multiple system atrophy but not by progressive supranuclear palsy lends epidemiologic support to the notion that different smoking habits are associated with different groups of neurodegenerative disease.

Intrusive memories, post-traumatic stress disorder and myocardial infarction

OBJECTIVES

To identify the associations between two personality variables (alexithymia, negative affect), social support, awareness of myocardial infarction, and the severity of post-traumatic stress symptoms.

DESIGN

A cross sectional design was adopted with simultaneous measures of both dependent and independent variables.

METHOD

A random sample of 69 patients who had an MI between 6 and 12 months previously were sent postal questionnaires measuring alexithymia, negative affect, social support, awareness of myocardial infarction, the severity of post-traumatic stress symptoms and a number of demographic details.

RESULTS

Forty-four individuals completed and returned all the questionnaires. A 10% prevalence of post-traumatic stress symptoms was found. Regression analyses were conducted to identify independent associates of the dependent variables with and without the inclusion of the measure of negative affect. Alexithymia, age, social support and awareness at the time of having a myocardial infarction, were each strongly predictive of one or all measures of symptoms.

CONCLUSIONS

Evidence supporting the impact of each of the variables on the course of post-traumatic stress disorder was supported in a population of myocardial infarction patients. If these variables were found predictive in a longitudinal study, they would indicate possible risk factors for post-traumatic stress disorder in this population.

A study of five candidate genes in Parkinson's disease and related neurodegenerative disorders. European Study Group on Atypical Parkinsonism

OBJECTIVE

To determine whether reported genetic association of polymorphisms in the CYP2D6, CYP1A1, N-acetyltransferase 2 (NAT2), DAT1, and glutathione s-transferase M1 (GSTM1) genes with PD were evident in a population of 176 unrelated patients with sporadic PD and to extend these findings to other disease groups (familial PD [n = 30], ALS [n = 50], multiple system atrophy [n = 38], progressive supranuclear palsy [n = 35], and AD [n = 23]).

METHODS

A combination of allele-specific PCR and analysis of restriction fragment length polymorphisms were performed.

RESULTS

We genotyped 1,131 individuals. After matching each patient with a control subject by age, sex, ethnicity, and geographic origin, there was no association of any allele/genotype with any of the six disease groups. There was an increased frequency of NAT2 slow acetylators in the ALS group compared with controls (70% versus 50%; OR 2.33 [95% CI, 1.03 to 5.30]), but this was not significant after adjusting for multiple testing.

CONCLUSIONS

This is one of the most extensive candidate gene studies performed in PD and the first time that some of these loci have been studied in multiple system atrophy and progressive supranuclear palsy. In contrast with previous studies, we found no role for these polymorphisms in the etiology of PD, ALS, multiple system atrophy, progressive supranuclear palsy, or AD.

Linkage of a composite inhibitory phenotype to a chromosome 22q locus in eight Utah families

Eight Utah multigenerational families, each with three to six cases of schizophrenia, were phenotyped with two specific measures of inhibitory neurophysiological functioning, P50 auditory sensory gating (P50), and antisaccade ocular motor performance (AS). A genomewide linkage analysis was performed to screen for loci underlying a qualitative phenotype combining the P50 and AS measures. For this composite inhibitory phenotype, the strongest evidence for linkage was to the D22s315 marker on chromosome 22q (lod score = 3.55, theta = 0) under an autosomal dominant model. Simulation analyses indicate that this 3.55 lod score is unlikely to represent a false positive result. Lod scores were 2.0 or greater for markers flanking D22s315. A nonparametric linkage (NPL) analysis of the chromosome 22 data showed evidence for allele sharing over the broad region surrounding D22s315 with a maximum NPL score of 3.83 (p = .002) for all pedigrees combined.

The tau gene in progressive supranuclear palsy: exclusion of mutations in coding exons and exon 10 splice sites, and identification of a new intronic variant of the disease-associated H1 haplotype in Italian cases

Mutations in coding exons or exon 10 5'-splice-site of the gene for microtubule-associated protein tau can cause chromosome 17-linked frontotemporal dementia and parkinsonism (FTDP-17). We sequenced the 11 coding exons plus exon-intron boundaries of the tau gene in 15 cases of progressive supranuclear palsy (PSP), and found no mutations in coding exons or exon ten 5'-splice sites. These data indicate that typical PSP is not associated with tau gene mutations similar to those causing FTDP-17. We also observed a +39deltaG base change in the intron following exon 4 in three out of 69 PSP cases (all three Italians), whereas it was not found in 150 Dutch controls and once in 112 Italian controls. The +39deltaG variant arose in the context of the PSP-associated tau H1 haplotype. Although a pathogenic role cannot be entirely excluded, +39deltaG is likely to be a rare polymorphism that may be in linkage disequilibrium with a biologically relevant locus inside or near to the tau gene.

Written disclosure: a way of coping with traumatic stress

Verbal debriefing after a traumatic incident may interrupt the natural adaptive processes that help people to deal with such incidents. This article examines the effectiveness of written interventions to help people experiencing distress after trauma experienced at work. As an alternative to critical incident debriefing, the authors recommend a staff education programme in tandem with written disclosure.

Reduced androgen levels in adult turner syndrome: influence of female sex steroids and growth hormone status

BACKGROUND AND OBJECTIVES

In girls with Turner syndrome androgen levels are reduced. In order to assess androgen status in women with Turner syndrome, we compared untreated adult women with Turner syndrome with a group of normal women. In addition, the effects of female sex hormone replacement therapy and GH status on the levels of circulating androgens in Turner syndrome was examined.

DESIGN

All patients were receiving female hormone replacement therapy (HRT), which was discontinued four months prior to the initial examination. Patients were studied before and during HRT. Following the initial evaluation, patients were given cyclical HRT for six months consisting of either oral substitution (17beta-oestradiol with norethisterone from day 13-22), or transdermal oestrogen substitution (17beta-oestradiol) with 1 mg norethisterone administered orally from day 13-22. Control subjects were studied once in the early follicular stage of the menstrual cycle.

SUBJECTS

The study group consisted of 27 (33.2 +/- 7.9 years) patients with Turner syndrome and an age matched control group of 24 (32.7 +/- 7.6 years) normal women.

MEASUREMENTS

Body composition measures, SHBG, testosterone (T), free testosterone (FT), dihydrotestosterone (DHT), alpha-4-androstendione (A), dehydroepiandrosterone sulphate (DHEAS), 17beta-oestradiol (E2), oestrone (E1), oestrone sulphate (ES), 24 h integrated GH concentration (ICGH), insulin-like growth factor I (IGF-I), insulin-like growth factor binding protein (IGFBP-3) were determined at baseline and after six months in women with Turner syndrome, and at baseline in control women.

RESULTS

Circulating levels of A, T, FT, DHT, and SHBG were reduced by 25-40% in comparison with age matched normal women. The level of DHEAS was normal. The level of E2 was undetectable and levels of E1 and ES were very low in untreated Turner women. Treatment with 17beta-oestradiol and norethisterone increased oestrogen to levels comparable to those of normal women, while further decreasing FT (P = 0.02), DHT (P = 0.04), and T (P = 0.1). In untreated women with Turner syndrome IGF-I correlated significantly with DHEAS (R = 0.503, P < 0.01), while in normal women IGF-I correlated with A (R = 0.637, P < 0.01), T (R = 0.536, P < 0.01), and FT (R = 0.700, P < 0.01). During hormonal replacement in women with Turner syndrome IGF-I correlated significantly with DHEAS (R = 0.547, P < 0.01). Employing multiple regression analysis IGFBP-3, ICGH, DHEAS and fat free mass explained 85% (adjusted R = 0.92, P < 0.0005) of the variation in the level of IGF-I in untreated Turner syndrome. In treated Turners IGFBP-3, ICGH, SHBG, T, and FT explained 78% (adjusted R = 0.88, P < 0.0005). In controls IGFBP-3, SHBG, BMI and age explained 74% (adjusted R = 0.86, P < 0.0005) of the variation in IGF-I, while GH status did not contribute at all.

CONCLUSION

The present study shows that many adults with Turner syndrome have reduced levels of circulating androgens, compared with an age-matched group of normal women. Conditions associated with Turner syndrome such as increased prevalence of sexual problems, reduced bone mineral content, osteoporosis, and an increased incidence of fractures and alterations in body composition could perhaps be alleviated or abolished by substitution with a low dose of androgens. Treatment with female hormonal replacement therapy is associated with a decrease in testosterone, free testosterone and dihydrotestosterone, possibly mediated by the androgenic effect of norethisterone. Furthermore significant differences in sex steroid levels, GH status and indices of body composition can be compatible with comparable levels of IGF-I in two very different groups of individuals.

Opinion of New Zealand physicians on management of acute ischaemic stroke: results of a national survey

BACKGROUND

Randomised trials have evaluated various treatments for acute ischaemic stroke, but it is unclear how the results of these studies are used in everyday practice.

AIMS

To obtain the opinions of physicians on the management of acute ischaemic stroke.

METHODS

A questionnaire was sent to 368 New Zealand Fellows of the Royal Australasian College of Physicians. The survey included questions about the availability of hospital services for stroke patients, management of acute ischaemic stroke and opinion on the efficacy of treatments used in acute ischaemic stroke.

RESULTS

Of the 293 physicians who responded to the questionnaire, 171 managed patients in the first week after stroke. Forty-seven per cent of these physicians were general physicians. Ninety-five per cent usually managed these patients in a general medical ward. Only five physicians admitted patients to an acute stroke unit and only 57% considered acute stroke units were beneficial. Aspirin was usually or sometimes used for patients with acute ischaemic stroke by 92% of physicians, intravenous heparin by 43%, low-dose subcutaneous heparin by 41%, low-molecular-weight heparin by 25% and tissue-plasminogen activator (t-PA) by 3%. Two thirds considered that aspirin was definitely beneficial, but most were uncertain about the efficacy of intravenous heparin, low-dose subcutaneous heparin, low-molecular-weight heparin and t-PA. Sixty-two per cent were prepared to begin aspirin and 21% subcutaneous heparin before computerised tomography (CT). Twenty-three per cent used anti-hypertensive treatment in the first few hours after an ischaemic stroke.

CONCLUSIONS

Several common deficiencies in the management of acute ischaemic stroke were identified. The widespread lack of stroke units, use of aspirin and heparin before CT, and lowering of blood pressure after an acute ischaemic stroke differed from accepted guidelines. Many physicians used heparin despite lack of evidence from randomised trials that it is beneficial. The development of stroke units and the appointment of physicians with a special interest in the management of stroke may improve the management of patients with acute stroke.

Word learning in the context of referential and salience cues

Adult referential behavior (gaze direction) and salience (target activation) were independently manipulated in a study of novel word learning. Children (seventy-five 18-month-olds and seventy-two 24-month-olds) were trained in different conditions with a novel word in the context of 2 remote-controlled toys. In response to the novel word at test, 24-month-olds tended to pick out the toy to which the adult referred in all conditions. They also tended to use the novel word appropriately. Comprehension by 18-month-olds was good when the salience of the toy did not conflict with the adult's referential intent, but it was disrupted when referential and salience cues conflicted and when referential cues were not available. Results imply that, at 24 months, children use the referential intent of the speaker to learn new words, but when first learning words, children may have a less secure grasp on the meaning of speakers' referential cues.

Expression of cyclo-oxygenase types-1 and -2 in human fetal membranes throughout pregnancy

Human labour is associated with increased prostaglandin synthesis within the fetal membranes. We have studied the expression of the two isoforms of the central prostaglandin synthetic enzyme, cyclo-oxygenase (COX-1 and COX-2), in human fetal membranes throughout pregnancy, at mRNA, protein and activity levels. COX-1 mRNA expression was low in human amnion and chorion-decidua and did not change with gestational age. COX-2 mRNA expression in fetal membranes increased with gestational age, with significant up-regulation prior to the onset of labour and in association with labour. Protein concentrations of COX-1 did not change, whilst concentrations of COX-2 increased from the first to the third trimester. COX activity increased with gestational age and in association with labour, although prostaglandin production in fetal membranes collected after labour was reduced, suggesting reduced substrate supply. These data suggest that it is up-regulation of COX-2, rather than of COX-1, which mediates increased prostaglandin synthesis within the fetal membranes at term. Much of the increase in COX-2 expression precedes the onset of labour, suggesting that it is a cause, rather than a consequence, of labour.

Management of stroke in Auckland Hospital in 1996

AIMS

To review the management of stroke in Auckland Hospital; compare current management with practice in Auckland in 1991/92; and determine how many patients may be suitable for treatment with aspirin or tissue plasminogen activator (t-PA).

METHODS

Retrospective review of case notes for all patients over the age of 15 years presenting during four months in 1996 with symptoms and signs of an acute stroke. Subarachnoid haemorrhages were excluded.

RESULTS

There were 184 stroke events (135 ischaemic strokes, 26 intracerebral haemorrhages, 23 unspecified strokes) in 179 patients. The time between the onset of symptoms and arrival in hospital was available for 109 patients: the overall median time was three hours, two hours for intracerebral haemorrhages, three hours for ischaemic strokes, four hours for unspecified strokes. Most patients (78%) were admitted to a general medical ward. Only 10% of the patients managed on a non-neurological ward were referred to a neurologist. Computed tomography (CT) was obtained in 88% of the patients. The median time from the onset of symptoms to CT was 19 hours (11 hours for intracerebral haemorrhages, 21 hours for ischaemic strokes). Only 11 patients (10%) were scanned within three hours of the onset of symptoms. Of the 135 patients who had an ischaemic stroke, 36% were treated with aspirin and 6% with heparin in the first 48 hours. Thirty-two patients (17%) died in hospital, 87 (47%) returned home, 37 (20%) were transferred to a rest home or private hospital and 28 (15%) were transferred to other places.

CONCLUSIONS

Compared with 1991, the rate of CT scanning after a stroke increased from 42% to 88%. At present, no more than 5% of all patients presenting with a stroke are suitable for consideration of treatment with t-PA. Routine treatment with aspirin in the first 48 hours could be achieved without other major changes in management.