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Biomedical subjects

M Barrett

Publications and source records attributed to M Barrett.

At least 19 recordsLinked to original sources
PubMed2003

Quantum information processing with trapped ions.

Experiments directed towards the development of a quantum computer based on trapped atomic ions are described briefly. We discuss the implementation of single-qubit operations and gates between qubits. A geometric phase gate between two ion qubits is described. Limitations of the trapped-ion method such as those caused by Stark shifts and spontaneous emission are addressed. Finally, we describe a strategy to realize a large-scale device.

Journal Article↗
PubMed2003

Experimental demonstration of a robust, high-fidelity geometric two ion-qubit phase gate.

Universal logic gates for two quantum bits (qubits) form an essential ingredient of quantum computation. Dynamical gates have been proposed in the context of trapped ions; however, geometric phase gates (which change only the phase of the physical qubits) offer potential practical advantages because they have higher intrinsic resistance to certain small errors and might enable faster gate implementation. Here we demonstrate a universal geometric pi-phase gate between two beryllium ion-qubits, based on coherent displacements induced by an optical dipole force. The displacements depend on the internal atomic states; the motional state of the ions is unimportant provided that they remain in the regime in which the force can be considered constant over the extent of each ion's wave packet. By combining the gate with single-qubit rotations, we have prepared ions in an entangled Bell state with 97% fidelity-about six times better than in a previous experiment demonstrating a universal gate between two ion-qubits. The particular properties of the gate make it attractive for a multiplexed trap architecture that would enable scaling to large numbers of ion-qubits.

Journal Article↗
PubMed2001

Variation in the promoter region of the myeloperoxidase gene is not directly related to lung cancer risk among male smokers in Finland.

In order to examine whether a polymorphism in the promoter region of the myeloperoxidase (MPO) gene is associated with lung cancer among male smokers, we conducted a case-control study nested within a Finnish clinical trial cohort. Although we found no evidence of an overall association between lung cancer risk and MPO genotype, the variant MPO genotype was associated with an increased risk of lung cancer among a subset of older men. These findings contrast with those from previous studies that report decreased lung cancer risk among MPO variant individuals.

Age Factors↗
PubMed2001

The kyphoscoliosis (ky) mouse is deficient in hypertrophic responses and is caused by a mutation in a novel muscle-specific protein.

The ky mouse mutant exhibits a primary degenerative myopathy preceding chronic thoraco-lumbar kyphoscoliosis. The histopathology of the ky mutant suggests that Ky protein activity is crucial for normal muscle growth and function as well as the maturation and stabilization of the neuromuscular junction. Muscle hypertrophy in response to increasing demand is deficient in the ky mutant, whereas adaptive fibre type shifts take place. The ky locus has previously been localized to a small region of mouse chromosome 9 and we have now identified the gene and the mutation underlying the kyphoscoliotic mouse. The ky transcript encodes a novel protein that is detected only in skeletal muscle and heart. The identification of the ky gene will allow detailed analysis of the impact of primary myopathy on idiopathic scoliosis in mice and man.

Amino Acid Sequence↗
PubMed2000

The association of RBC sodium-lithium countertransport (Vmax) with left ventricular mass in African American women.

In Caucasian hypertensives and diabetics, increased RBC sodium-lithium countertransporter activity (SLC) is a marker for end-organ complications of vascular disease. A subgroup of African Americans with high Vmax for SLC show strong correlations with dyslipidaemia, insulin resistance, microalbuminuria and higher blood pressure. The purpose of our study was to determine if Vmax in premenopausal African American women correlates with left ventricular mass (LVM) before the onset of clinically diagnosed hypertension. Non-diabetic African American women (n = 35, mean age 31 years) were evaluated for cardiovascular disease risk factors, including anthropometric and blood pressure measurements, oral glucose tolerance test (OGTT), and euglycaemic hyperinsulinaemic clamp for insulin sensitivity. Fasting blood specimens were assayed for SLC activity (Vmax) and lipids. Cardiac structure was determined by 2-D echocardiography. LVM was calculated by the cube root formula and adjusted for height (LVM index). Vmax correlated significantly with average systolic blood pressure (r = 0.45, P = 0.007), diastolic blood pressure (r = 0.48, P = 0.004), mean blood pressure (r = 0.48, P = 0.003) and LVM index (r = 0.40, P = 0.02). Vmax was also associated with fasting insulin (r = 0.39, P = 0.01), the sum of insulin (r = 0.52, P = 0.002), and insulin sensitivity adjusted for fat-free mass (r = -0.55, P = 0.001). There was no statistically significant relationship between Vmax and body mass or lipids. Vmax for SLC correlates with cardiac structure in premenopausal African American women. Vmax is also associated with insulin sensitivity and insulin resistance in this non-diabetic sample. SLC activity may be useful in identifying a subgroup of young African American women with left ventricular hypertrophy and insulin resistance before the onset of clinically diagnosed hypertension and diabetes. Journal of Human Hypertension (2000) 14, 213-219.

Adult↗
PubMed2000

The association of left ventricular mass with cardiovascular risk factors in African American women.

BACKGROUND: African American women have disproportionately high rates of myocardial infarction and stroke. Left ventricular hypertrophy is an independent risk factor for cardiovascular disease. Increases in left ventricular mass (LVM) may precede the expression of hypertension. The purpose of this study was to determine whether LVM is related to cardiovascular risk variables in healthy, premenopausal African American women. METHODS: Normotensive or borderline hypertensive nondiabetic African American women (N = 52; mean age, 31 years) underwent anthropometric and blood pressure measurements, oral glucose tolerance test, euglycemic clamp, fasting lipid profile, and two-dimensional echocardiography. LVM was calculated by the cube root formula and adjusted for height [LVM index (LVMI)]. RESULTS: LVMI correlated with body mass index (r = .36, P = 0.009), systolic blood pressure (r = .44, P = 0.001), diastolic blood pressure (r = .43, P = 0.002), and central body fat (r = .42, P = 0.002). LVMI also directly correlated with lipoprotein (a) (r = .34, P = 0.02). Significant independent relationships of other metabolic variables with LVMI were not detected. DISCUSSION: These data show that increased LVMI is associated with body mass index and central obesity, but not with lipids, insulin resistance, or insulin sensitivity. LVMI is also associated with blood pressure before the expression of severe hypertension in healthy, premenopausal African American women.

Adult↗
PubMed2000

A comparison of the extent and impacts of sewage contamination on urban groundwater in developed and developing countries.

In much of the world urban groundwater is an important resource for domestic and industrial use. In many developing countries, groundwater taken directly (untreated) from individual springs and wells is the only option available to communities where comprehensive, reliable reticulated supply systems are absent. A common feature of urban groundwater in both developing and developed countries is contamination by sewage. Current and recent research is presented that shows sewer leakage impacts groundwater in developed countries whilst on-site sanitation contaminates groundwater in developing countries. In the latter case, the competing demands of sanitation and groundwater protection must be addressed. Limitations on the usefulness of accepted standard sewage indicator species in groundwater are also highlighted. As sewage contamination of groundwater is usually addressed only if an actual health risk is posed, it is vital both to developed and developing countries to understand the movement of actual pathogens in groundwater in the context of groundwater management. Further research is required on microbial survival and health risks posed by sewage contamination.

Cross-Cultural Comparison↗
PubMed1999

Effect of temperature on stability of marker constituents in Echinacea purpurea root formulations.

Stability of an alkamide and a phenolic phytochemical marker in a hydro-alcoholic extract of Echinacea purpurea root and a dried powder prepared by evaporation of the extract was assessed in storage for 7 months at three temperature regimes: -20, 25 and 40 degrees Celsius. In the extract, the major alkamide, dodeca-2E, 4E, 8Z, 10E/Z-tetraenoic acid isobutyl amide, was not significantly affected by storage at any of the temperatures, but cichoric acid content declined as significantly (P = 0.05) at both 25 degrees C and 40 degrees C as compared to low-temperature storage. In the powder, the major alkamide showed a significantly reduced level at 25 degrees C and 40 degrees C while cichoric acid did not decline significantly. These results suggest that more attention should be given to the effect of formulation and temperature on storage of Echinacea products.

Caffeic Acids↗
PubMed1999

Relative validity of a food frequency questionnaire among tin miners in China: 1992/93 and 1995/96 diet validation studies.

OBJECTIVE: Diet validation research was conducted to compare the respondents' reporting of dietary intake in a food frequency questionnaire (FFQ) with intake reported in food recalls. Because the population received annual salary increments that could modify food intake, diet validation studies (DVSs) were conducted during two time intervals. DESIGN: A 99-item FFQ was administered by an interviewer twice in a 1-year interval, and responses to each FFQ item were compared with 28 days of interviewer-administered food recalls that were collected in four 1-week intervals during each season of 1992/93. The second validation study in 1995/96 had a similar design to the earlier one. SETTING: A prospective cohort study of lung cancer among tin miners in China was initiated in 1992, with dietary and other risk factors updated annually. SUBJECTS: Among a cohort of high risk tin miners for lung cancer, two different samples (n = 141 in 1992/93, and n = 113 in 1995/96) for each diet validation study were randomly selected from four mine units, that were representative of all worker units. RESULTS: Miners reported a significantly higher average frequency of intake of foods in the food recalls than the FFQ, with few exceptions. Deattenuated Pearson correlation coefficients of the frequency of food intake between the FFQ and food recalls were in the range of -0.40 to 0.72 in both studies, with higher positive correlations for beverages and cereal staples than for animal protein sources, vegetables, fruits and legumes. The percentage of individuals with exact agreement in the extreme quartiles of intake in the food recalls and FFQ ranged from 0 to 100% in both studies. CONCLUSIONS: Among Chinese miners, the range in correlations between the food recalls and the FFQ were due to: (i) market availability of foods during the food recall weeks compared to their annual reported intake in the FFQ; (ii) cultural perception of time; and (iii) differences in how the intake of mixed dishes and their multi-ingredient foods were reported in the recalls vs. the FFQ. The range in the percentage of agreement in the same quartiles and the changes in food intake over time may have implications for the analysis of the diet-disease relationship in this cohort.

Analysis of Variance↗
PubMed1999

Depletion of cutaneous peptidergic innervation in HIV-associated xerosis.

Severe xerosis occurs in approximately 20% of human immunodeficiency virus seropositive patients. Changes in cutaneous innervation have been found in various inflammatory skin diseases and in xerotic skin in familial amyloid. We have therefore carried out a quantitative examination of the cutaneous peptidergic innervation in human immunodeficiency virus-associated xerosis. Immunohistochemistry and image analysis quantitation were used to compare total cutaneous innervation (protein gene product 9.5), calcitonin gene-related peptide, substance P, and vasoactive intestinal peptide peptidergic fibers, at two sites in the skin of human immunodeficiency virus-associated xerosis patients (upper arm, n = 12; upper leg, n = 11) and site-matched seronegative controls (upper arm, n = 10; upper leg, n = 10). Measurement of lengths of fibers of each type was carried out for each subject in the epidermis and papillary dermis, and around the sweat glands. Immunostained mast cells in these areas were counted. Epidermal integrity and maturation were assessed by immunostaining for involucrin. There were significant (Mann-Whitney U test; p < 0.02) decreases in total lengths of protein gene product 9.5 fibers in both epidermis/papillary dermis and sweat gland fields; of calcitonin gene-related peptide innervation in the epidermis/papillary dermis; and of substance P innervation of the sweat glands. There were no differences in the distribution of mast cells, or in the epidermal expression of involucrin. Depletion of the calcitonin gene-related peptide innervation may affect the nutrient blood supply of the upper dermis, and the integrity and function of basal epidermis and Langerhans cells. Diminished substance P innervation of the sweat glands may affect their secretory activity. Both of these changes may be implicated in the development of xerosis.

Adult↗
PubMed1999

Enhancing safety in a pediatric unit.

This descriptive study demonstrates how a group of nurses in the clinical setting can identify and implement a safe sharps disposal strategy to enhance safety. The aim of this small study was to determine a safer method of disposing used sharp items. The findings indicated that many factors can contribute to inappropriate disposal of used sharp items. Changes in practice were implemented following the findings of this study and resulted in enhanced safety in this paediatric unit. In addition, results of the study were utilised to contribute to evidence based nursing practice.

Adolescent↗
PubMed1999

Effect of vitamin intervention on the relationship between GSTM1, smoking, and lung cancer risk among male smokers.

The GSTM1 (glutathione S-transferase mu-1) null genotype is suspected of increasing an individual's susceptibility to tobacco smoke carcinogens because of impaired carcinogen detoxification. We were interested in whether there were differences in lung cancer susceptibility to smoking within the GSTM1 genotypes and the impact of antioxidant supplementation on this. For this purpose, we conducted a nested lung cancer case-control study and evaluated the role of GSTM1 within the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study. GSTM1 genotype status was determined for 319 cases and 333 controls using a PCR-based approach. GSTM1 was evaluated as an independent risk factor and as an effect modifier of smoking using logistic regression analyses. The GSTM1 null genotype itself was unrelated to risk of lung cancer, odds ratio (OR) = 1.09 and 95% confidence interval (CI), 0.79-1.50, but it may have modified the effect of smoking. There was a suggestion for a stronger association between years of smoking and lung cancer among the GSTM1 null genotype, but the differences between GSTM1 null and present genotypes were not statistically significant (P = 0.12). Furthermore, the smoking association was strongest among those with the GSTM1 null genotype not receiving alpha-tocopherol supplementation, whereas among those receiving alpha-tocopherol, there was no modification by GSTM1 on the association between smoking duration and lung cancer risk. Beta-carotene supplementation did not modify the relationship between GSTM1, smoking years, and lung cancer risk. In conclusion, GSTM1 is not associated with lung cancer risk in male smokers but may confer a higher susceptibility to cumulative tobacco exposure. This association may be attenuated by alpha-tocopherol but not by beta-carotene supplementation.

Adult↗
PubMed1998

Pathogenicity and immunogenicity of different isolates of Teladorsagia circumcincta.

The effects on liveweight gain and development of immunity were studied in lambs trickle infected for 8 weeks with either a benzimidazole-resistant isolate (Moredun ovine resistant isolate, MORI), a multiple benzimidazole + ivermectin-resistant isolate (Moredun caprine resistant isolate, MCRI) or an unselected susceptible isolate (Moredun ovine susceptible isolate, MOSI) of Teladorsagia circumcincta. Plasma pepsinogen concentrations of infected groups were significantly elevated compared to an uninfected control group (P < 0.001) by day 14. The liveweight gains varied markedly but there were no statistical differences between the infected and uninfected control groups at any point in time during the study. Lambs infected with the MORI had significantly lower faecal consistency scores than the other challenged groups on days 7 and 14 (P < 0.05) but from day 21 onwards, faecal consistencies were similar in all of the groups. There was a notable difference in the pre-patent periods of the different isolates with the MOSI producing positive faecal egg counts (FECs) by day 14 of the study. The FECs remained reasonably low once infections had reached patency and there were no further differences between the groups. Following administration of anthelmintic to remove residual worms from the trickle infection, no differences between the infected groups in terms of worm burden or mucosal mast cell numbers were evident as a consequence of a single challenge infection. The changes in genetic code associated with enhanced resistance against anthelmintics do not appear to have resulted in any fundamental alteration of the pathogenicity and immunogenicity of these three isolates of Teladorsagia.

Animals↗
PubMed1998

Antiviral phenylpropanoid glycosides from the medicinal plant Markhamia lutea.

Three new phenylpropanoid glycosides, named luteoside A (3), luteoside B (4), and luteoside C (5), were isolated together with the known compounds verbascoside (1) and isoverbascoside (2) from the roots of the medicinal plant Markhamia lutea. The structures of the new compounds were determined to be 1-O-(3, 4-dihydroxyphenyl)ethyl beta-D-apiofuranosyl(1-->2)-alpha-l-rhamnopyranosyl(1-->3)-4-O- caffeo yl-6-acetyl-beta-d-glucopyranoside, 1-O-(3,4-dihydroxyphenyl)ethyl beta-d-apiofuranosyl(1-->2)-alpha-l-rhamnopyranosyl(1-->3)-6-O- caffeo yl-beta-d-glucopyranoside, and 1-O-(3,4-dihydroxyphenyl)ethyl beta-D-apiofuranosyl(1-->2)-alpha-l-rhamnopyranosyl(1-->3)-6-O- ferulo yl-beta-d-glucopyranoside, respectively, on the basis of chemical and spectroscopic data. All five phenylpropanoid glycosides exhibited potent in vitro activity against respiratory syncytial virus.

Antiviral Agents↗
PubMed1998

Children's subjective identification with the group and in-group favoritism.

Recent developments in social psychology have explained children's preference for members of the in-group in terms of processes of self-categorization and identification with the in-group. In contrast, this study, addressing nationality self-conceptions, examines the possibility that even before subjective identification with the group has occurred, as de facto group members, children will have been exposed to a great deal of positive information about their own national group, which is likely to encourage group-serving judgments. Children who had failed to identify themselves as members of their national group were required in this study to make evaluative judgments about 5 national groups, including their own. Significant preference for the in-group emerged on 2 of 3 measures. It is concluded that subjective identification with the in-group is not a necessary precondition for in-group favoritism.

Adolescent↗
PubMed1997

Thalidomide: a novel therapy for microsporidiosis.

BACKGROUND & AIMS: Microsporidiosis is a common cause of chronic diarrhea in human immunodeficiency virus (HIV)-seropositive individuals and often does not respond to treatment. Fecal tumor necrosis factor alpha (TNF-alpha) is elevated in microsporidiosis; therefore, thalidomide, an anti-TNF-alpha agent, was used as therapy. METHODS: Eighteen subjects with chronic diarrhea caused by Enterocytozoon bieneusi that had not responded symptomatically to albendazole and 1 untreated subject with Encephalitozoon intestinalis received 1 month of thalidomide, 100 mg nocte. Clinical response was assessed by stool frequency and body weight, histological response by light microscopy with villus height/crypt depth ratios and electron microscopy, and immunologic response by fecal TNF-alpha level. RESULTS: Seven subjects with chronic diarrhea due to E. bieneusi had a complete clinical response, and 3 had a partial response to thalidomide. There was a significant decrease in stool frequency from 5.3 to 3.1 per day (P = 0.001), and weight increased significantly by 1.2 kg (P < 0.02). Thalidomide significantly increased the villus height/crypt depth ratio (1.95 to 2.07; P = 0.045) and number of abnormal forms of microsporidia (P < 0.01). Fecal TNF-alpha level nonsignificantly decreased from 17.9 to 8.9 U/mL. There was apparent disruption of all stages of the life cycle of E. intestinalis. CONCLUSIONS: Thalidomide may be an effective therapy for diarrhea and weight loss from E. bieneusi.

Acquired Immunodeficiency Syndrome↗