PubMed Health⌕ Search

Biomedical subjects

Michael Peters

Publications and source records attributed to Michael Peters.

18 recordsLinked to original sources
PubMed2006

Hand preference for writing and associations with selected demographic and behavioral variables in 255,100 subjects: the BBC internet study.

In an Internet study unrelated to handedness, 134,317 female and 120,783 male participants answered a graded question as to which hand they preferred for writing. This allowed determination of hand preference patterns across 7 ethnic groups. Sex differences in left-handedness were found in 4 ethnic groups, favoring males, while no significant sex differences were found in three of the groups. Prevalence of left-handedness in the largest of the ethnic groups (self-labelled as "White") was comparable to contemporary hand preference data for this group [Gilbert, A. N., & Wysocki, C. J. (1992). Hand preference and age in the United states. Neuropsychologia, 30, 601-608] but the prevalence of left-handedness in individuals >70 years of age was considerably higher in the present study. Individuals who indicated "either" hand for writing preference had significantly lower spatial performance (mental rotation task) and significantly higher prevalence of hyperactivity, dyslexia, asthma than individuals who had clear left or right hand preferences, in support of Crow et al. [Crow, T., Crow, L., Done, D., & Leask, S. (1998). Relative hand skill predicts academic ability: global deficits at the point of hemispheric indecision. Neuropsychologia, 36, 1275-1282]. Similarly, an association of writing hand preference and non-heterosexual orientation was clearest for individuals with "either" writing hand responses. We conclude that contradictions in the literature as to whether or not these variables are linked to handedness stem largely from different definitions of hand preference. Due to a lack of statistical power in most studies in the literature, the "either" hand writing preference group that yielded the most salient results in this study is not normally available for analysis.

Adolescent↗
PubMed2006

Neural control of playing a reversed piano: empirical evidence for an unusual cortical organization of musical functions.

Using functional magnetic imaging techniques and neuropsychological tests, we studied a young male musician (C.S.) who performs at a professional level both on a regular piano keyboard and on a reverse keyboard (reversed right to left). The participant was left-handed, had left dominance for language but, remarkably, right dominance for the control of piano playing on both keyboards. With respect to music perception, C.S. showed left-sided activation dominance within the left superior temporal sulcus, which is normally associated with higher order auditory processing and right-sided activations in the secondary sensory cortex extending into the supramarginal gyrus. We suggest that C.S.'s pattern of functional asymmetry, characterized by audio-motor control using a right-sided network, could be a factor in his exceptional piano-playing ability on both the standard and reversed keyboard.

Adult↗
PubMed2006

Mental rotation test performance in four cross-cultural samples (n = 3367): overall sex differences and the role of academic program in performance.

Two meta-analyses (Linn and Petersen, 1985; Voyer et al., 1995) discuss variables that affect mental rotation performance but they do not mention a potentially important variable, the Academic Program in which students are enrolled. Sex differences in brain size have been related to sex differences in spatial performance (e.g., Falk et al., 1999) and thus it is important to know whether mental rotation performance shows a significant interaction between Sex and Academic Program. To put our understanding of the Academic Program effect on a firmer empirical footing, we conducted a large scale multicultural study, with samples from Canada, Germany and Japan, using identical test procedures in all studies. Significant main effects for Sex and Academic Program were found in all four studies, with large effect sizes for Sex and medium to large effect sizes for Academic Program (based on Cohen's d). No significant interactions between these variables were found in the four samples. Our demonstration of a reliable Academic Program effect has clear and important pragmatic implications for a broad range of work on spatial ability and its interpretation.

Adolescent↗
PubMed2006

Sex differences in left/right confusion.

In agreement with the literature, females (n=269) gave themselves significantly poorer ratings than males (n=164) in evaluating their ability to make fast and accurate left/right judgments. In order to evaluate the ecological validity of the self-ratings, subjects were tested on a task that required fast and accurate left/right judgments, on a mental rotation task, and on a task that required navigation of a virtual maze. The correlations between the performances and self-ratings were computed. Both males and females who gave themselves very poor LRC (left/right confusion) ratings had significantly lower accuracy scores on the left/right judgement task than males and females with average ratings, but there was no sex-specific relation between LRC ratings and left/right judgements that would explain why females give themselves lower LRC ratings. For females only, a weak correlation between LRC scores and the learning of the virtual maze was observed, but no significant correlations were observed between LRC scores and mental rotation performance. We conclude that self-ratings on left/right confusion questions, although they yield reliable sex differences, are poor predictors of actual performance on spatial tasks that involve left/right judgements. Thus, and in support of earlier speculations (Sholl and Egeth, 1981; Teng and Lee, 1982; Williams et al., 1993), the principal cause of the marked sex differences in LRC self-ratings likely lies in a greater willingness of females to rate themselves more poorly on questions of this type than is the case for men.

Analysis of Variance↗
PubMed2005

Sex differences and the factor of time in solving Vandenberg and Kuse mental rotation problems.

In accounting for the well-established sex differences on mental rotation tasks that involve cube stimuli of the Shepard and Metzler (Shepard & Metzler, 1971) kind, performance factors are frequently invoked. Three studies are presented that examine performance factors. In Study 1, analyses of the performance of a large number of subjects (n=1765) that performed the Vandenberg and Kuse (1976) mental rotation test (MRT) under standard conditions showed that the magnitude of the sex differences increases as subjects proceed through the sequence of problems, and that fewer females than males reach the last problems in a problem set. This supports the role of time constraints in sex differences on the MRT. Study 2 compared the magnitude of sex differences for subjects (n=212) who did the MRT under standard conditions (T1), and with double the time (T2) allowed for the test. No significant reduction in the magnitude of sex differences was observed-even though the overall scores under T2 increased markedly for both sexes. Study 3 examined the suggestion by that mental rotation differences arise because females spend more time than males in assuring that stimuli that do not match do indeed not match, with no sex differences for matching stimuli. This hypothesis was not supported for a sample of 20 males and 26 females. We conclude that performance factors may play a role in sex difference on mental rotation tasks, but do not account for all of the differences.

Adult↗
PubMed2005

Hand preference, magical thinking and left-right confusion.

Several reports suggest a significant correlation between hand preference quotients and Magical Ideation Scale (MIS) scores, such that individuals with mixed preferences have higher MIS scores. In a sample of 156 male and 257 female undergraduate university students no significant correlation was found between MIS scores and hand preference; hand preference being defined in numerous ways, and using short and long hand preference questionnaires to assess handedness. An index of left-right confusion was significantly related to MIS score, but only in females. We suggest that the role of subjects' response style and general approach to filling out questionnaires should be fully explored before "neurological" causes of links between hand preference and other questionnaire-assessed behavioural variables are invoked.

Adolescent↗
PubMed2004

Activin A stimulates vascular endothelial growth factor gene transcription in human hepatocellular carcinoma cells.

BACKGROUND & AIMS: Up-regulation of vascular endothelial growth factor is known to play a critical role in hepatocellular tumor biology. In an attempt to identify factors responsible for vascular endothelial growth factor induction in human hepatocellular carcinoma, we evaluated the effects of activin A, a member of the transforming growth factor-beta cytokine superfamily, on vascular endothelial growth factor gene expression. METHODS: Expression of vascular endothelial growth factor, activin A, and its receptors was analyzed by immunohistochemistry, polymerase chain reaction, and enzyme-linked immunosorbent assay. Functional vascular endothelial growth factor promoter analysis and gel shift assays were performed to define minimal promoter requirements and potential transcription factors. Nuclear expression and biochemical modifications of Sp1, as well as subcellular distribution, expression, and physical interaction of Smad proteins with Sp1, were assessed with immunoprecipitation and Western blot analysis. RESULTS: Hepatocellular carcinoma tumors and cell lines expressed activin A and its receptors. Activin A stimulated vascular endothelial growth factor gene transcription through Sp1-dependent induction of vascular endothelial growth factor promoter activity. Furthermore, activin A stimulated the DNA-binding and transactivation potential of Sp1. Immunoprecipitation showed activin A-dependent nuclear translocation of Smad2 and induction of Sp1/Smad2 interaction. The functional relevance of Sp1/Smad2 interaction was confirmed by transient transfection experiments, which showed that overexpression of Smad2 increased vascular endothelial growth factor promoter activity and endogenous vascular endothelial growth factor protein expression, whereas dominant negative Smad2 blocked activin A responsiveness. CONCLUSIONS: This study identifies activin A as a novel stimulus of vascular endothelial growth factor gene expression in hepatocellular carcinoma and delineates physical and functional cooperation of Sp1 and Smad2 as the underlying mechanism.

Activin Receptors↗
PubMed2004

Time to complete mixing for the measurement of glomerular filtration rate from single bolus plasma 51Cr-EDTA clearance.

BACKGROUND AND METHOD: In the measurement of glomerular filtration rate from the plasma clearance of 51Cr ethylenediamine tetraacetic acid by using the slope-intercept method, the first sample is conventionally taken at 2 h, the time by which it is generally assumed that the clearance curve has reached a single exponential. We examined this assumption by comparing the slopes, alpha 12 and alpha 23, based, respectively, on samples at 2 and 3 h, and at 3 and 4 h. RESULTS: In 421 patient studies in whom the first sample was taken between 110 and 130 min after injection, the mean ratio, alpha 12/alpha 23, was 1.101 (SEM 0.011) which is significantly higher than unity (P<<0.001). The relationship between alpha 12/alpha 23 and the slope, alpha 13 (which is a measure of filtration function already indexed for body size) based on all three samples was negative. By modelling the relationship between mixing time and alpha 13 it was shown that this relationship suggests delayed mixing of the indicator throughout its distribution volume and is inconsistent with irreversible binding of indicator to plasma protein. A significant positive association was observed between alpha 12/alpha 23 and age, but this is largely explained by a generally poorer filtration function in the older age group since low levels of alpha 13 theoretically predict a longer mixing time. In 188 patient studies in whom the first sample was taken more than 130 min after injection, the mean ratio, alpha 12/alpha 23, was 1.055 (SEM 0.017) which is still significantly higher than unity (P<<0.005) but significantly less than the ratio based on studies in which the first sample was taken at 110-130 min (P<0.02). The ratio alpha 12/alpha 23 still showed a significant relation (positive) with age but not with filtration function. CONCLUSION: This error in the estimation of glomerular filtration rate to which delayed mixing leads will make its greatest impact when using the simplified slope-only technique, but can be minimized by delaying the first blood sample.

Adolescent↗
PubMed2003

Pharmacists on rounding teams reduce preventable adverse drug events in hospital general medicine units.

BACKGROUND: Previous studies found that medication errors result from lack of sufficient information during the prescribing step. Therefore, it is proposed that having a pharmacist available when patients are evaluated during the rounding process may reduce the likelihood of preventable adverse drug events (ADEs). The objectives of this study were to evaluate the impact of having a pharmacist participate with a physician rounding team on preventable ADEs in general medicine units and to document pharmacist interventions made during the rounding process. METHODS: A single-blind, standard care-controlled study design was used to compare patients receiving care from a rounding team including a pharmacist with patients receiving standard care (no pharmacist on rounding team). Patients admitted to and discharged from the same general medicine unit were included in the study. The main outcome measure of this study was preventable ADEs. Patient records were randomly selected and evaluated by a blinded process involving independent senior pharmacist specialists and a senior staff physician. Interventions made by the pharmacists in the treatment group were documented. RESULTS: The rate of preventable ADEs was reduced by 78%, from 26.5 per 1000 hospital days to 5.7 per 1000 hospital days. There were 150 documented interventions recommended during the rounding process, 147 of which were accepted by the team. The most common interventions were (1) dosing-related changes and (2) recommendations to add a drug to therapy. CONCLUSION: Pharmacist participation with the medical rounding team on a general medicine unit contributes to a significant reduction in preventable ADEs.

Drug Utilization Review↗
PubMed2003

Transforming growth factor beta 1 stimulates vascular endothelial growth factor gene transcription in human cholangiocellular carcinoma cells.

The expression pattern and functional interaction of proangiogenic factors in human cholangiocellular carcinoma (CCC) have not been fully defined. We therefore investigated the expression of vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-beta 1 as well as their respective receptors in human CCC tumor samples and further analyzed their functional interaction in vitro. Expression of VEGF, TGF-beta 1, and their receptors was examined by immunohistochemistry, in situ hybridization, quantitative competitive reverse transcription-PCR, and ELISA. VEGF promoter analysis and identification of transcription factors involved in promoter regulation were investigated using transient transfection and electrophoretic mobility shift assays. We observed strong expression of VEGF in CCC tumor cells and localization of VEGF receptors 1 and 2 in endothelial cells; in addition, coexpression of TGF-beta 1 and its receptors in tumor cells suggests a possible functional interaction between both cytokines. In vitro studies confirmed a paracrine/autocrine stimulation of VEGF by TGF-beta 1 at a transcriptional level. Additional molecular studies using 5' deletion and mutational analysis of the human VEGF promoter revealed that TGF-beta 1 stimulates VEGF through Sp1-dependent transcriptional activation. These data suggest that overexpression and functional interaction of TGF-beta 1 and VEGF might contribute to the "angiogenic switch" and the malignant phenotype in human CCC.

Bile Duct Neoplasms↗
PubMed2003

Activated signal transducer and activator of transcription 3 (STAT3) supports the malignant phenotype of human pancreatic cancer.

BACKGROUND & AIMS: Constitutive activation of signal transducer and activator of transcription 3 (STAT3) has been implicated in regulation of growth and malignant transformation. We therefore analyzed the expression and biologic significance of STAT3 in human pancreatic cancer cells. METHODS: Expression and activation of STAT3 were investigated by immunohistochemistry and immunoblotting. Functional inactivation of STAT3 was achieved by stable transfection of dominant-negative STAT3 constructs in 2 pancreatic cancer cell lines and confirmed by electrophoretic mobility shift assay and immunoblotting. Cell proliferation and tumorigenicity were evaluated by cell counting, colony formation in soft agar, and xenotransplantation in nude mice. STAT3-dependent cell cycle distribution was monitored by flow cytometry, immunoprecipitation, immunoblotting, and histone H1 and GST-Rb kinase assays. RESULTS: Compared with nontransformed human pancreas, activated STAT3 is overexpressed in ductal carcinoma cells but not in ducts from chronic pancreatitis. Constitutive activation was also observed in all human pancreatic cancer cell lines examined. Functional inactivation of STAT3 resulted in significant inhibition of anchorage-dependent and -independent proliferation in vitro and reduced tumor growth in vivo. Cell cycle analysis showed a delay of G(1)/S-phase progression due to inhibition of cyclin-dependent kinase 2 activity based on increased expression of p21(WAF1) in vitro and in vivo. Blocking of the STAT3 upstream activator Janus kinase 2 by tyrphostin also resulted in growth arrest because of delayed G(1)/S-phase progression and increased expression of p21(WAF1). CONCLUSIONS: On malignant transformation, activated STAT3 promotes cellular proliferation by acceleration of G(1)/S-phase progression and thereby contributes to the malignant phenotype of human pancreatic cancer.

Cyclin-Dependent Kinase Inhibitor p21↗
PubMed2003

HIV sexual risk behavior among Puerto Rican women.

We examined the association of primary or nonprimary sexual partner relationship status on sexual risk behaviors, including condom use, among Latina women who are at self-disclosed increased heterosexual risk for human immunodeficiency virus (HIV) infection. Data were collected via structured interviews of 187 Puerto Rican women, aged 18-35, who attended a health clinic in the Bronx, New York. Approximately 13% of participants reported sexual activities with both primary and nonprimary sexual partners during the 6 months prior to the interview. Primary or nonprimary sexual partner status was associated with significant differences in frequency of condom use during anal sex and oral-penile sex, with more frequent condom use reported during these sexual activities with nonprimary sexual partners. Thus, potential contextual differences associated with primary or nonprimary relationship status may represent important factors to consider when designing interventions to facilitate HIV-protective behaviors among populations of urban women identified at increased heterosexual risk for HIV infection.

Adult↗
PubMed2002

CD94/NKG2 expression does not inhibit cytotoxic function of lymphocytic choriomeningitis virus-specific CD8+ T cells.

Murine Ag-specific CD8(+) T cells express various NK markers and NK inhibitory receptors that have been proposed to modulate immune responses. Following acute infection of C57BL/6 and BALB/cJ mice with lymphocytic choriomeningitis virus (LCMV), we observed that Ag-specific CD8(+) T cells expressed CD94/NKG2. Only slight expression of Ly49A and Ly49C receptors was observed on NP396-specific T cells, while all NP396-specific T cells expressed the NKT cell marker U5A2-13 Ag. Expression of CD94/NKG2 was maintained for at least 1 year following LCMV infection, as was the NKT cell marker. By means of cell sorting and quantitative PCR, we found that NP118-specific CD8(+) T cells primarily express transcripts for inhibitory NKG2 receptor isoforms. CD94/NKG2 expression was also observed on Ag-specific CD8(+) T cells following infection with polyoma virus, influenza virus, and Listeria monocytogenes, suggesting that it may be a common characteristic of Ag-specific CD8(+) T cells following infection with viral or bacterial pathogens. Expression of CD94/NKG2 on memory-specific CD8(+) T cells did not change following secondary challenge with LCMV clone 13 and did not inhibit viral clearance. Furthermore, we found no evidence that CD94/NKG2 inhibits either the lytic function of LCMV-specific T cells or their capacity to produce effector cytokines upon peptide stimulation. Finally, down-regulation of CD94/NKG2 was found to occur only during chronic LCMV infection. Altogether, this study suggests that CD94/NKG2 expression is not necessarily correlated with inhibition of T cell function.

Animals↗
PubMed2002

Overexpression of pRB in human pancreatic carcinoma cells: function in chemotherapy-induced apoptosis.

BACKGROUND: Human pancreatic adenocarcinomas are highly resistant to chemotherapy. The p16 tumor-suppressor protein is inactivated in more than 90% of human pancreatic cancers. The p16 protein transcriptionally inhibits expression of retinoblastoma tumor-suppressor gene pRB. The pRB protein transcriptionally inhibits expression of the p16 gene. Because pRB normally prevents apoptosis, we investigated whether pRB is involved in resistance to chemotherapy-induced apoptosis in pancreatic cancer cells. METHODS: pRB expression was examined by immunohistochemistry in 106 human pancreatic tissue specimens. The human pancreatic tumor cell line Capan-1 (pRB+/p16-) was stably transfected with p16 to functionally inactivate pRB. pRB gene expression was examined by western and northern blot analyses, and pRB function was assessed by electrophoretic mobility shift assays and promoter transactivation studies for the transcription factor E2F. Changes in cell sensitivity to chemotherapy were measured by assays for cytotoxicity and apoptosis. RESULTS: pRB was overexpressed in pancreatic ductal adenocarcinomas but was hardly detectable in other pancreatic malignancies, chronic pancreatitis, or nontransformed human pancreatic tissue. Expression of p16 in Capan-1 cells resulted in the loss of pRB gene and protein expression concomitant with increased activity of the transcription factor E2F, which was not detected in wild-type or control-transfected Capan-1 cells. Wild-type and control-transfected Capan-1 cells were resistant to chemotherapy-induced apoptosis, but pRB-depleted (i.e., p16-transfected) Capan-1 cells were highly sensitive. The effect was specific to pRB depletion because two other human pancreatic cancer cell lines that retained high pRB expression after p16 transfection were resistant to chemotherapy-induced apoptosis. CONCLUSIONS: Overexpression of pRB is associated with human pancreatic duct-cell cancer and may allow pancreatic cancer cells to evade chemotherapy-induced apoptosis.

Antineoplastic Agents↗
PubMed2002

Finger length and distal finger extent patterns in humans.

The fingers in the adult human hand differ in length and in distal extent. The literature agrees that in the clear majority of males, the distal extent of the ring finger tends to be relatively greater (using the middle finger as standard) than the index finger. However, the results for females vary considerably, with some studies reporting that females show a similar pattern to that of males, while others suggest that the prevalence of a longer index finger is relatively or absolutely more common in females. We provide a review of the literature, and a set of data for both finger length and distal fingertip extent of the finger for a contemporary cohort of young adult females and males (n = 502). Finger length measures favor the ring finger of both sexes, with smaller between-finger differences for females than for males. However, while the distal fingertip extent favors the ring finger of both hands in males, in females the left hand shows no significant differences, and the right hand shows a small index finger advantage. Thus, the sexual dimorphism in finger measures is more strongly expressed in the distal extent of fingertips than in the length of fingers. The sex differences in distal fingertip extent derive from the index finger only, with a lesser distal extent of the index finger, relative to the middle finger, in males than in females.

Adolescent↗
PubMed2002

Women and men exhibit different cortical activation patterns during mental rotation tasks.

The strongest sex differences on any cognitive task, favoring men, are found for tasks that require the mental rotation of three-dimensional objects. A number of studies have explored functional brain activation during mental rotation tasks, and sex differences have been noted in some. However, in these studies there was a substantial confounding factor because male and female subjects differed in overall performance levels. In contrast, our functional brain activation study examined cortical activation patterns for males and females who did not differ in overall level of performance on three mental rotation tasks. This allowed us to eliminate any confounding influences of overall performance levels. Women exhibited significant bilateral activations in the intraparietal sulcus (IPS) and the superior and inferior parietal lobule, as well as in the inferior temporal gyrus (ITG) and the premotor areas. Men showed significant activation in the right parieto-occitpital sulcus (POS), the left intraparietal sulcus and the left superior parietal lobule (SPL). Both men and women showed activation of the premotor areas but men also showed an additional significant activation of the left motor cortex. No significant activation was found in the inferior temporal gyrus. Our results suggest that there are genuine between-sex differences in cerebral activation patterns during mental rotation activities even when performances are similar. Such differences suggest that the sexes use different strategies in solving mental rotation tasks.

Adult↗
PubMed1999

Performance Asymmetries in Computer Mouse Control of Right-Handers, and Left-Handers with Left- and Right-Handed Mouse Experience.

Precision and general computer mouse aiming performance by right-handers (RH-RM) and left-handers with right-handed mouse experience (LH-RM) and by left-handers with left-handed mouse experience (LH-LM) were compared. A number of performance measures, such as reaction time, time to reach a target, time to click on target, and cursor trajectory, were analyzed. Superficially, specific hand experience seemed to dictate performance asymmetries, but a closer look revealed interactions between hand preference and hand performance. That finding has implications for theories of handedness. In addition, precision and general directional aiming with the mouse cursor showed a clear right hand superiority in reaction time in both RH-RM and LH-RM subjects, whereas LH-LM subjects showed no lateral asymmetries. Finally, the overall time taken for the task, averaged across groups and conditions, favored the experienced hand by some 180 ms. In practical terms, that is not a large difference, especially because the difference will be reduced with practice. Thus, the use of the inexperienced hand can be advocated when there is a need to forestall or ameliorate repetitive stress in the experienced hand.

Journal Article↗