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Biomedical subjects

N Spence

Publications and source records attributed to N Spence.

12 recordsLinked to original sources
PubMed2002

The detection of Tomato spotted wilt virus (TSWV) in individual thrips using real time fluorescent RT-PCR (TaqMan).

Tomato spotted wilt virus (TSWV) is an important virus, economically in the UK, causing damaging disease in ornamental and vegetable crops. The virus is vectored by several species of thrips, most importantly the western flower thrips (Frankliniella occidentalis Pergande [Thysanoptera: Thripidae]). The vector thrips themselves constitute a damaging pest and are difficult to control completely. Monitoring thrips numbers is an important part of the control of virus, but does not give information on how many of the thrips are viruliferous. Monitoring the presence of viruliferous thrips at an early stage of an epidemic may lead to improved disease control, since virus can be spread effectively whilst vector pressure is low and symptoms may take several weeks to appear on some hosts. This paper describes the development of a sensitive and robust, high-throughput method for the detection of TSWV in individual insects based on TaqMan chemistry. The method incorporates a novel RNA specific internal control to increase the reliability of the results. Results are also presented on comparisons of different extraction methods, including insects taken from sticky traps, for high-throughout testing. Implementation of a method such as this for the reliable detection of TSWV in individual thrips would aid the understanding of the progress of TSWV epidemics, and offer an early disease warning system for growers.

Animals↗
PubMed2002

Electrical impedance measurement as an endpoint detection method for routine coagulation tests.

A whole-blood platelet aggregometer is adapted to measure electrical impedance changes in plasma during prothrombin time (PT) estimations. The impedance curve shows an acceleration phase, which is comparable to the absorbance curve acceleration phase associated with the onset of coagulation. The amplitude of the impedance change correlates with the fibrinogen concentration of the plasma. Statistical analysis of PT derived by absorbance and impedance changes shows a significant difference between the two methods but a good correlation. The method is reproducible but laborious and requires attention to technique. Further investigation of the method utilising a more sensitive instrument and redesigned electrodes is indicated. It may also be possible to modify reagent systems to optimise impedance changes.

Blood Coagulation Tests↗
PubMed1997

Modelling regional population growth in China.

"This paper develops a forward demographic rates-based multiregional population model on the basis of a set of multiregional population accounts. Forward emigration rates and immigration flows are adopted to describe the external migrations. The model is used to make consistent multiregional population projections of China at a provincial level.... Three sets of multiregional population projections of China at provincial level are made for the period 1987-2087. It is found that the national population trend is a combination of various regional population trends. Some regions, such as Zhejiang, will reach their population peak as early as the beginning of the next century while other regions, such as Xinjiang, will face continuous population growth in the first half of the next century."

Asia↗
PubMed1995

Somatic mosaicism in sperm is associated with intergenerational (CAG)n changes in Huntington disease.

We have analysed the CAG repeat in the Huntington disease (HD) gene in sperm and blood from 20 unrelated HD patients. Although the CAG repeat displayed significant mosaicism in sperm from all individuals, there were marked differences in the degree of repeat instability. Individuals who had either inherited or transmitted an expanded CAG repeat displayed the highest levels of repeat mosaicism, whereas individuals who had inherited or transmitted a contracted repeat had very limited CAG mosaicism in sperm. A strong association between intergenerational change in CAG allele size and the level of sperm repeat mosaicism was determined (P = 0.019). In contrast, neither blood CAG size nor repeat mosaicism in blood, were significantly associated with intergenerational CAG changes. These data suggest the presence of a cis-acting factor, separate from CAG size, that strongly influences the intergenerational behaviour of the CAG repeat. Additional studies are needed to determine whether analysis of CAG mosaicism in sperm is useful for assessing an individual's risk for transmitting large expansions or contractions to his offspring.

Adolescent↗
PubMed1995

Ancestral differences in the distribution of the delta 2642 glutamic acid polymorphism is associated with varying CAG repeat lengths on normal chromosomes: insights into the genetic evolution of Huntington disease.

This study addresses genetic factors associated with normal variation of the CAG repeat in the Huntington disease (HD) gene. To achieve this, we have studied patterns of variation of three trinucleotide repeats in the HD gene including the CAG and adjacent CCG repeats as well as a GAG polymorphism at residue 2642 (delta 2642). We have previously demonstrated that variation in the CCG repeat is associated with variation of the CAG repeat length on normal chromosomes. Here we show that differences in the GAG trinucleotide polymorphism at residue 2642 is also significantly correlated with CAG size on normal chromosomes. The B allele which is associated with higher CAG repeat lengths on normal chromosomes is markedly enriched on affected chromosomes. Furthermore, this glutamic acid polymorphism shows significant variation in different ancestries and is absent in chromosomes of Japanese, Black and Chinese descent. Haplotype analysis of both the CCG and delta 2642 polymorphisms have indicated that both are independently associated with differences in CAG length on normal chromosomes. These findings lead to a model for the genetic evolution of new mutations for HD preferentially occurring on normal chromosomes with higher CAG repeat lengths and a CCG repeat length of seven and/or a deletion of the glutamic acid residue at delta 2642. This study also provides additional evidence for genetic contributions to demographic differences in prevalence rates for HD.

Alleles↗
PubMed1995

Sex-dependent mechanisms for expansions and contractions of the CAG repeat on affected Huntington disease chromosomes.

A total of 254 affected parent-child pairs with Huntington disease (HD) and 440 parent-child pairs with CAG size in the normal range were assessed to determine the nature and frequency of intergenerational CAG changes in the HD gene. Intergenerational CAG changes are extremely rare (3/440 [0.68%]) on normal chromosomes. In contrast, on HD chromosomes, changes in CAG size occur in approximately 70% of meioses on HD chromosomes, with expansions accounting for 73% of these changes. These intergenerational CAG changes make a significant but minor contribution to changes in age at onset (r2 = .19). The size of the CAG repeat influenced larger intergenerational expansions (> 7 CAG repeats), but the likelihood of smaller expansions or contractions was not influenced by CAG size. Large expansions (> 7 CAG repeats) occur almost exclusively through paternal transmission (0.96%; P < 10(-7)), while offspring of affected mothers are more likely to show no change (P = .01) or contractions in CAG size (P = .002). This study demonstrates that sex of the transmitting parent is the major determinant for CAG intergenerational changes in the HD gene. Similar paternal sex effects are seen in the evolution of new mutations for HD from intermediate alleles and for large expansions on affected chromosomes. Affected mothers almost never transmit a significantly expanded CAG repeat, despite the fact that many have similar large-sized alleles, compared with affected fathers. The sex-dependent effects of major expansion and contractions of the CAG repeat in the HD gene implicate different effects of gametogenesis, in males versus females, on intergenerational CAG repeat stability.

Adolescent↗
PubMed1994

DNA haplotype analysis of Huntington disease reveals clues to the origins and mechanisms of CAG expansion and reasons for geographic variations of prevalence.

This study of allelic association using three intra- and two extragenic markers within 150 kb of the Huntington disease (HD) mutation has provided evidence for linkage disequilibrium for four of five markers. Haplotype analysis of 67 HD families using markers in strong linkage disequilibrium with HD identified two haplotypes underlying 77.6% of HD chromosomes. Normal chromosomes with these two haplotypes had a mean number of CAG repeats significantly larger than and an altered distribution of CAG repeats compared with other normal chromosomes. Furthermore, haplotype analysis of five new mutation families reveals that HD has arisen on these same two chromosomal haplotypes. These findings suggest that HD arises more frequently on chromosomes with specific DNA haplotypes and higher CAG repeat lengths. We then studied CAG and CCG repeat lengths in the HD gene on 896 control chromosomes from different ancestries to determine whether the markedly reduced frequency of HD in Finland, Japan, China and African Blacks is associated with an altered frequency of DNA haplotypes and subsequently lower CAG lengths on control chromosomes compared to populations of Western European descent. The results show a highly significant inverse relationship between CAG and CCG repeat lengths. In populations with lowered prevalence rates of HD, CAG repeat lengths are smaller and the distribution of CCG alleles is markedly different from Western European populations. These findings suggest that, in addition to European emigration, new mutations make a contribution to geographical variation of prevalence rates and is consistent with a multistep model of HD developing from normal chromosomes with higher CAG repeat lengths.

Africa↗
PubMed1993

Molecular analysis of late onset Huntington's disease.

Late onset Huntington's disease is characterised by onset of symptoms after the age of 50 and is usually associated with a milder course. We have analysed the CAG trinucleotide repeat within the HD gene in 133 late onset patients from 107 extended families. The median upper allele size for the CAG repeat was 42 with a range of 38 to 48 repeats. A significant negative correlation (r = -0.29, p = 0.001) was found between the length of repeat and age of onset for the total cohort. However, for persons with age of onset greater than 60, no significant correlation was found. In addition, no significant correlation was found between age of onset and size of the lower allele and the sex of the affected parent or grandparent. There was no preponderance of maternal descent for late onset cases in this series. This study shows that variation in repeat length only accounts for approximately 7% of the variation in age of onset for persons beyond the age of 50 and clearly shows how with increasing onset age the effect of the repeat length on this onset age seems to diminish.

Age of Onset↗
PubMed1993

Differential leucocyte analysis of samples up to 48 hours old: improved results with citrate pyridoxal phosphate anticoagulant.

Routine haematology screening, including differential leucocyte counts, were performed using a Coulter STKS analyser on blood samples taken into several commonly available anticoagulants at time intervals up to 48 h after venepuncture. An anticoagulant based on citrate phosphate dextrose adenine, with a platelet anti-aggregant/dis-aggregant pyridoxal-5-phosphate (CPP), was found to be superior to tri-potassium ethylene diamine tetra-acetic acid (K3EDTA) in its ability to preserve leucocytes for differential counting in the STKS analyser and preserving leucocyte (particularly neutrophil) morphology for light microscopy. CPP performed as well as K3EDTA for other routine haematology measurements and was found to be stable at room temperature for at least one year. The increased cost of CPP will prevent its widespread use, but compatibility with K3EDTA will allow it to be used along with K3EDTA in situations where transit times to the laboratory regularly exceed 24 h.

Anticoagulants↗
PubMed1985

The psychiatric intensive care unit.

The first three and a half years' operation of a psychiatric intensive care unit, based on the general hospital model, is described. This eight-bedded ward focusses on the treatment of the most acutely psychiatrically ill patients, and not on the forensic or custodial aspects of such units previously described. It has gained general acceptance within the setting of a state psychiatric hospital, and has received 1132 admissions since its inception. Demographic, clinical, and treatment data are presented and the advantages and disadvantages of the unit are discussed.

Adult↗
PubMed1984

The Illness Behavior Questionnaire as an aid to clinical assessment.

The Illness Behavior Questionnaire (IBQ) is a 62-item self-report instrument that provides information relevant to the delineation of a patient's attitudes, ideas, affects, and attributions in relation to illness. The scores generated are described, and nine clinical vignettes are presented, together with IBQ score profiles and interpretations to illustrate the manner in which the latter may complement other clinical data. The ways in which individuals react to their own health status is becoming of greater importance as the taking of responsibility for one's own health is increasingly emphasized. The IBQ provides information that should be relevant to the management of patients, regardless of the specific nature of their illness.

Adult↗