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Biomedical subjects

G Jackson

Publications and source records attributed to G Jackson.

At least 91 records · Page 5Linked to original sources
PubMed2000

Impurity-induced suppression of core turbulence and transport in the DIII-D tokamak

Turbulence is significantly reduced in a tokamak plasma as a result of neon seeding of an L-mode discharge. Correspondingly, confinement is improved and cross-field ion thermal transport reduced. Fully saturated turbulence in the range 0.1</=k( perpendicular)rho(s)</=0. 6 is measured at rho = 0.7 and exhibits a factor of 5 reduction in total power after neon injection, with almost complete suppression for k( perpendicular)rho(s)>0.35. These observations are consistent with a reduction in the calculated linear growth rate for k( perpendicular)rho(s)>0.5 and an increase in the measured ExB flow shearing rate.

Journal Article↗
PubMed2000

Molecular biology of leukemia.

Identification and characterization of leukemia-related chromosomal translocations have had significant impact on all aspects of the management of acute leukemia, including its diagnosis, assignment of prognosis, and development of an appropriate treatment plan. Several genes are recurrent targets of chromosomal abnormalities, suggesting that they play a key role in leukemogenesis. Significant progress has been made to define potentially unifying molecular mechanisms of leukemic transformation. Hopefully, these findings will provide the basis for molecularly targeted therapies for leukemia.

Female↗
PubMed2000

Neurobiological findings in early phase schizophrenia.

This paper summarises the available information on MRI-determined hippocampal morphometry in first-episode patients as an illustration of the value and interpretation of findings in the neurobiology of early phase schizophrenia. We report a thin slice (1.5 mm) study of 32 first episode and 39 high risk patients which demonstrated significantly smaller hippocampi (right -9%, left -11%) in first episode patients that were of a similar magnitude to those found in chronic patients (right -10%, left -11%) but non-significant volume reductions in high risk individuals, including the 15 subjects who subsequently developed psychoses. Consideration is given to the implications of these findings, including the possible role of early and later neurodevelopmental influences. We present animal data showing that chronic placental insufficiency, as elicited by uterine artery ligation can give rise to substantial reduction (31%) in hippocampal volumes and reflect on other potentially relevant pathophysiological mechanisms, including those that may occur during the early phases of psychotic illnesses, including their prodromes. Greater attention needs to be paid to the study of early phase psychosis in order to obtain a clearer understanding of the nature and time course of neurobiological changes associated with it. Although there is a growing literature on first episode psychosis, there is a striking dearth of information on the neurobiology of the prodrome.

Animals↗
PubMed2000

A randomised placebo controlled trial of the effects of tibolone on blood pressure and lipids in hypertensive women.

The effects of hormone replacement therapy in hypertensive women are controversial. This randomised placebo controlled trial assessed the effect of tibolone 2.5 mg on blood pressure and fasting plasma lipids in 29 hypertensive postmenopausal women over 6 months using a 2:1 randomisation to tibolone. The primary clinical end-point was mean office blood pressure. At 6 months systolic blood pressure declined by 5.30 +/- 2.87% vs 4.94 +/- 3.37% whilst diastolic blood pressure declined 5.38 +/- 2.65% vs 0.85 +/- 3.69% on tibolone and placebo respectively. These differences were not statistically significant. Triglycerides decreased by 33.3 +/- 6.1% vs 7.6 +/- 7.9% (P < 0.01) and high-density lipoprotein (HDL)-cholesterol by 21.7 +/- 3.8% vs 2.4 +/- 2.6% (P < 0.01) with tibolone as opposed to placebo. No significant differences were observed in total cholesterol, low-density lipoprotein (LDL)-cholesterol and lipoprotein (a). Fibrinogen levels were reduced by 13.6 +/- 6.8% on tibolone compared to a 19.3 +/- 15.4% rise (P < 0.05) on placebo. This study suggests that tibolone has no deleterious effect on blood pressure in women with hypertension but has contrasting effects on biochemical risk factors. Large-scale studies are required to determine the overall effect of tibolone on cardiovascular morbidity and mortality.

Antihypertensive Agents↗
PubMed2000

The incidence of acute promyelocytic leukemia appears constant over most of a human lifespan, implying only one rate limiting mutation.

It is believed that most malignancies become more common with increasing age due to the requirement for several mutations to accumulate and subsequently interact. The age specific incidence of acute promyelocytic leukemia (APL) was investigated using population-based data from 77 million subject years of observation, yielding 149 consecutive cases. The incidence appears approximately constant with respect to age, an observation not previously reported with any other malignancy. These findings are most easily explained by there being only one rate limiting genetic event required to initiate the disease, although other, non-rate limiting mutations may also be necessary for disease development. It is also argued that this mutation is probably restricted to cells committed to differentiation, which may explain why APL is curable by chemotherapy.

Adolescent↗
PubMed2000

A comparison of molecular and enzyme-based assays for the detection of thiopurine methyltransferase mutations.

S-Methylation by thiopurine methyltransferase (TPMT) is an important route of metabolism for the thiopurine drugs. About one in 300 individuals are homozygous for a TPMT mutation associated with very low enzyme activity and severe myelosuppression if treated with standard doses of drug. To validate the use of molecular genetic techniques for the detection of TPMT deficiency, we have determined red blood cell TPMT activity in 240 adult blood donors and 55 normal children. Genotype was determined by restriction fragment length analysis of polymerase chain reaction products in a cohort of 79 of the blood donors and five cases of azathioprine-induced myelosupression, and this confirmed a close relationship between genotype and phenotype. In 17 of the 24 cases in which mutations were found, DNA was also available from remission bone marrow. In one of these cases, DNA from the remission marrow sample indicated the presence of a non-mutated allele that had not been seen in the blast DNA sample obtained at presentation. These results indicate that polymerase chain reaction-based assays give reliable and robust results for the detection of TPMT deficiency, but that caution should be exercised in relying exclusively on DNA obtained from lymphoblasts in childhood leukaemia.

Adolescent↗
PubMed2000

Congenital caudal vertebral malformations in the alpaca (Lama pacos).

OBJECTIVE: To assess radiologically the caudal vertebrae of a male alpaca with an abnormal tail, and nine of his offspring. PROCEDURE: Right lateral and ventrodorsal radiographs were taken of the caudal vertebrae. RESULTS: The caudal vertebral abnormalities in these alpacas included vertebral subluxation, hemivertebrae, wedge hemivertebrae and block vertebrae. CONCLUSION: These malformations in offspring of one sire suggest a hereditary basis for congenital caudal vertebral malformations in the alpaca.

Animals↗
PubMed2000

Does angina vary with the menstrual cycle in women with premenopausal coronary artery disease?

OBJECTIVE: To determine whether angina in women with established coronary heart disease varies with changes in hormone concentrations during the menstrual cycle. DESIGN: Subjects were prospectively studied once a week for four weeks. SETTING: Cardiology outpatient department of tertiary referral centre. SUBJECTS: Nine premenopausal women, mean (SEM) age 38.89 (2.18) years, with established coronary heart disease, symptomatic angina, and a positive exercise test. MAIN OUTCOME MEASURE: Myocardial ischaemia as determined by time to 1 mm ST depression during symptom limited exercise testing. Position in the menstrual cycle was established from hormone concentrations. RESULTS: The early follicular phase, when oestradiol and progesterone concentrations were both low, was associated with the worst exercise performance in terms of time to onset of myocardial ischaemia, at 290 (79) seconds; the best performance (418 (71) seconds) was when oestrogen concentrations were highest in the mid-cycle (p < 0.05). Similar trends were observed in other measured variables. Progesterone concentrations did not influence exercise performance. CONCLUSIONS: During the menstrual cycle myocardial ischaemia was more easily induced when oestrogen concentrations were low. This may be important for timing the assessment and evaluating treatment in women with coronary heart disease.

Adult↗
PubMed2000

Are women discriminated against for lipid lowering therapy? Results from a prospective cohort of women with coronary artery disease.

The objective of the study was to compare the lipid management of men and women with documented coronary artery disease in 587 patients (433 men and 154 women) undergoing coronary angiography between 1991 and 1995. A fasting total cholesterol (TC) was measured in all patients on the morning of angiography. A postal/telephone follow-up was carried out one year after angiography in a subpopulation of 278 patients (194 men and 84 women) who were not taking lipid-lowering therapy (LLT) or whose TC was > 5.2 mmol/l at the time of angiography. At baseline, mean TC was 5.89 mmol/l (SE 0.06) in the men and 6.47 mmol/l (SE 0.09) in the women (p = < 0.0001). Action or recommendation to institute LLT was taken in 141 (32.7%) men and 62 (40.3%) women (p = 0.09). In the follow-up population, comparing men with women, 74 (38.3%) vs 39 (46.4%) were taking LLT (p = 0.21); 56 (28.9%) vs 26 (31.0%) had not undergone repeat TC testing (p = 0.73); when performed, repeat TC was 5.75 (0.09) mmol/l vs 5.64 (0.16) mmol/l (p = 0.53); mean decrease in TC between baseline and follow-up was 0.86 (0.10) mmol/l vs 1.01 (0.21) mmol/l (p = 0.51). There was no significant gender difference in lipid management either at the time of coronary angiography or subsequent follow-up, although the level of lipid-lowering drug use remained inadequate in both sexes.

Cholesterol↗