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Biomedical subjects

R Bull

Publications and source records attributed to R Bull.

At least 19 recordsLinked to original sources
PubMed2000

The Judd illusion: evidence for two visual streams or two experimental conditions?

In the Judd illusion, observers inaccurately bisect the shaft located between two arrowheads pointing in the same direction. The magnitude of error is greater when verbal judgements are compared to action based responses (reaching out and grasping the centre of the bar). This difference has been attributed to the presence of two visual streams within cortical processing. In contrast, we provide evidence that the improved accuracy in the reaching condition may be due to occlusion of the illusory background during the transport phase of the movement. We suggest that caution is required when interpreting performance differences between two conditions that are not strictly equivalent.

Adult↗
PubMed1999

Dichloroacetate (DCA) dosimetry: interpreting DCA-induced liver cancer dose response and the potential for DCA to contribute to trichloroethylene-induced liver cancer.

Pharmacokinetic studies with dichloroacetate (DCA) provide insights into the likelihood that trichloroethylene-induced liver cancers arise from formation of DCA as a metabolite and the mode of action by which DCA induces liver cancer. A simple physiologically based pharmacokinetic model was developed to analyze DCA blood concentration data from mice unexposed to or pre-treated with DCA. The large first pass metabolism of DCA in the liver is significantly reduced by DCA pretreatment. Because DCA inhibits its own metabolism, large increases in area under the blood concentration curve occur at lower doses than would be predicted from single-dose pharmacokinetic studies with naive mice. The dose metrics associated with the incidence of liver tumors in contrast to the multiplicity of tumors per animal may be different, suggesting potentially different roles in the cancer process for DCA versus its metabolites. By linking a model for trichloroethylene (TCE) pharmacokinetics with the DCA model, maximum levels of DCA potentially produced from TCE were estimated to be at or below the analytical chemistry detection limits. In addition, the predicted levels of DCA would be too small to produce the observed liver cancers following corn oil gavage exposure of mice to TCE.

Animals↗
PubMed1999

This little piggy went to market: using a health education market as a learning strategy for preregistration Bachelor of Nursing students.

In the academic year 1997/98 at the University of Tasmania, students undertaking the research unit in their second year of the Bachelor of Nursing (BN) took part in producing a health education market for the staff and students on the Launceston campus of the University. The cafeteria and outside grassed areas were transformed into a network of information stalls, displays and activities. The students reported a constant flow of interested and enthusiastic people to their stalls. Integrating research findings, technical and interpersonal skills and creative ability, students were encouraged to synthesize many areas of theory in the nursing programme in order to present high quality, informative and engaging stalls. Formal evaluation of both group and individual work was integrated into the process in such a way as to provide prompt feedback and encouragement, ongoing quality control and to generate a final grade for each student.

Education, Nursing, Baccalaureate↗
PubMed1998

Viral ion channels: molecular modeling and simulation.

In a number of membrane-bound viruses, ion channels are formed by integral membrane proteins. These channel proteins include M2 from influenza A, NB from influenza B, and, possibly, Vpu from HIV-1. M2 is important in facilitating uncoating of the influenza A viral genome and is the target of amantadine, an anti-influenza drug. The biological roles of NB and Vpu are less certain. In all cases, the protein contains a single transmembrane alpha-helix close to its N-terminus. Channels can be formed by homo-oligomerization of these proteins, yielding bundles of transmembrane helices that span the membrane and surround a central ion-permeable pore. Molecular modeling may be used to integrate and interpret available experimental data concerning the structure of such transmembrane pores. This has proved successful for the M2 channel domain, where two independently derived models are in agreement with one another, and with solid-state nuclear magnetic resonance (NMR) data. Simulations based on channel models may yield insights into possible ion conduction and selectivity mechanisms.

Amino Acid Sequence↗
PubMed1998

Sulfhydryl oxidation modifies the calcium dependence of ryanodine-sensitive calcium channels of excitable cells.

The calcium dependence of ryanodine-sensitive single calcium channels was studied after fusing with planar lipid bilayers sarcoendoplasmic reticulum vesicles isolated from excitable tissues. Native channels from mammalian or amphibian skeletal muscle displayed three different calcium dependencies, cardiac (C), mammalian skeletal (MS), and low fractional open times (low Po), as reported for channels from brain cortex. Native channels from cardiac muscle presented only the MS and C dependencies. Channels with the MS or low Po behaviors showed bell-shaped calcium dependencies, but the latter had fractional open times of <0.1 at all [Ca2+]. Channels with C calcium dependence were activated by [Ca2+] < 10 microM and were not inhibited by increasing cis [Ca2+] up to 0.5 mM. After oxidation with 2,2'-dithiodipyridine or thimerosal, channels with low Po or MS dependencies increased their activity. These channels modified their calcium dependencies sequentially, from low Po to MS and C, or from MS to C. Reduction with glutathione of channels with C dependence (native or oxidized) decreased their fractional open times in 0.5 mM cis [Ca2+], from near unity to 0.1-0.3. These results show that all native channels displayed at least two calcium dependencies regardless of their origin, and that these changed after treatment with redox reagents.

Animals↗
PubMed1998

Cyclic ADP-ribose activates caffeine-sensitive calcium channels from sea urchin egg microsomes.

Adenosine 5'-cyclic diphosphoribose [cyclic ADP-ribose (cADPR)], a metabolite of NAD+ that promotes Ca2+ release from sea urchin egg homogenates and microsomal fractions, has been proposed to act as an endogenous agonist of Ca2+ release in sea urchin eggs. We describe experiments showing that a microsomal fraction isolated from Tetrapigus nyger sea urchin eggs displayed Ca(2+)-selective single channels with conductances of 155.0 +/- 8.0 pS in asymmetric Cs+ solutions and 47.5 +/- 1.1 pS in asymmetric Ca2+ solutions. These channels were sensitive to stimulation by Ca2+, ATP, and caffeine, but not inositol 1,4,5-trisphosphate, and were inhibited by ruthenium red. The channels were also activated by cADP-ribose in a Ca(2+)-dependent fashion. Calmodulin and Mg2+, but not heparin, modulated channel activity in the presence of cADP-ribose. We propose that these Ca2+ channels constitute the intracellular Ca(2+)-induced Ca2+ release pathway that is activated by cADP-ribose in sea urchin eggs.

Adenosine Diphosphate Ribose↗
PubMed1998

Common causes of leg ulceration.

Good treatment of any leg ulcer depends upon an accurate diagnosis of the underlying cause. Most leg ulcers occur secondary to venous or arterial disease but other rarer causes sometimes need to be considered. The treatment of the underlying condition is far more important than the choice of dressing.

Chronic Disease↗
PubMed1997

Children's arithmetical difficulties: contributions from processing speed, item identification, and short-term memory.

Children's arithmetical difficulties are often explained in terms of a short-term memory deficit. However, the underlying cause of this memory deficit is unclear, with some researchers suggesting a slow articulation rate and hence increased decay of information during recall, while others offer an explanation in terms of slow speed of item identification, indicating difficulty in retrieving information stored in long-term memory. General processing speed is also related to measures of short-term memory but has rarely been assessed in studies of children's arithmetic. Measures of short-term memory, processing speed, sequencing ability, and retrieval of information from long-term memory were therefore given to 7-year-old children. When reading ability was controlled for, arithmetic ability was best predicted by processing speed, with short-term memory accounting for no further unique variance. It was concluded that children with arithmetic difficulties have problems specifically in automating basic arithmetic facts which may stem from a general speed of processing deficit.

Analysis of Variance↗
PubMed1997

Eyewitness performance in cognitive and structured interviews.

This paper addresses two methodological and theoretical questions relating to the Cognitive Interview (CI), which previous research has found to increase witness recall in interviews. (1) What are the effects of the CI mnemonic techniques when communication techniques are held constant? (2) How do trained interviewers compare with untrained interviewers? In this study, witnesses (college students) viewed a short film clip of a shooting and were questioned by interviewers (research assistants) trained in conducting the CI or a Structured Interview (SI)--similar to the CI except for the "cognitive" components--or by untrained interviewers (UI). The CI and SI groups recalled significantly more correct information compared to the UI group. However they also reported more errors and confabulated details. Theoretical and practical implications of the results are discussed in terms of precisely identifying the CI facilitatory effects and consequent good practice in the forensic setting.

Adolescent↗
PubMed1997

[Ethics code of the Chilean Biological Society].

The Chilean Biological Society has approved an ethics code for researchers, elaborated by its Ethic Committee. The text, with 16 articles, undertakes the main ethical problems that researchers must solve, such as institutional, professional or societal ethics, scientific fraud, breaches in collaborative work, relationships between researchers, participation in juries and committees, ethical breaches in scientific publications, scientific responsibility and punishments. This code declares its respect and valorization of all life forms and adheres to international biomedical ethical codes. It declares that all knowledge, created or obtained by researchers is mankind's heritage.

Biology↗
PubMed1996

Calcium dependence of ryanodine-sensitive calcium channels from brain cortex endoplasmic reticulum.

Endoplasmic reticulum vesicles isolated from rat brain cortex and fused with lipid bilayers displayed ryanodine-sensitive calcium channels, with three cytoplasmic calcium dependences. A: Channels (n=5) stimulated by Ca2+ (K0.5=1.2 microM and nHill=1.9) and not inhibited up to 0.5 mM Ca2+. B: Channels (n=14) cooperatively activated (K0.5=6.9 microM and nHill=1.8), and inhibited by Ca2+ (K0.5=152 microM and nHill=1.8). C: Low Po (<0.1) channels (n=22), non-cooperatively activated and inhibited with the same K0.5=26.3 microM Ca2+. These three types of responses to cytoplasmic [Ca2+] may underlie separate calcium release pathways in neurons of rat brain cortex.

Animals↗
PubMed1996

Ca(2+)- and pH-dependent halothane stimulation of Ca2+ release in sarcoplasmic reticulum from frog muscle.

The effect of halothane on calcium release kinetics was studied in triad-enriched sarcoplasmic reticulum vesicles from frog skeletal muscle. Release from vesicles passively equilibrated with 3 mM 45CaCl2 was measured in the millisecond time range by use of a fast-filtration system. Halothane (400 microM) increased release rate constants at pH 7.1 and 7.4 as a function of extravesicular pCa. In contrast, halothane at pH 6.8 produced the same stimulation of release from pCa 7.0 to 3.0; no release took place in these conditions in the absence of halothane. Halothane shifted the calcium activation curve at pH 7.1, but not at pH 7.4, to the left and increased channel open probability at pH 7.1 in the cis pCa range of 7.0 to 5.0. These results indicate that cytosolic pCa and pH modulate the stimulatory effects of halothane on calcium release. Furthermore, halothane stimulated release in frog skeletal muscle at low pH and resting calcium concentration, indicating that in frog muscle halothane can override the closing of the release channels produced by these conditions, as it does in malignant hyperthermia-susceptible porcine muscle.

Animals↗
PubMed1995

Psychotherapy and the recovery of memories of childhood sexual abuse: U.S. and British practitioners' opinions, practices, and experiences.

Licensed U.S. doctoral-level psychotherapists randomly sampled from the National Register of Health Service Providers in Psychology (Surveys 1 and 2, n = 145; Council for the National Register of Health Service Providers in Psychology, 1992) and British psychologists sampled from the Register of Chartered Clinical Psychologists (Survey 2, n = 57; British Psychological Society, 1993) were surveyed regarding clients' memories of childhood sexual abuse (CSA). The 3 samples were highly similar on the vast majority of measures. Respondents listed a wide variety of behavioral symptoms as potential indicators of CSA, and 71% indicated that they had used various techniques (e.g., hypnosis, interpretation of dreams) to help clients recover suspected memories of CSA. Across samples, 25% of the respondents reported a constellation of beliefs and practices suggestive of a focus on memory recovery, and these psychologists reported relatively high rates of memory recovery in their clients.

Adult↗
PubMed1995

Clinical nurse specialist: walking the wire.

Considered by many to be the panacea for all nursing's problems, the clinical nurse specialist (CNS) has only recently gained widespread recognition as a legitimate role in Australia. The CNS is the equivalent in other states and territories of the clinical nurse consultant, the charge nurse or the nurse unit manager. Implementation of the role has been complicated by inadequately delineated role functions, unrealistic expectations and limited recognition of clinical expertise. Using both quantitative and qualitative exploratory techniques it was found that three critical themes impinged in a negative way on the effectiveness of the CNS. These were role ambiguity, role overload and the 'paradox of power'. Maintaining clinical expertise in the practice setting is essential for high quality cost effective and autonomous nursing care and this can be provided through the effective implementation of the CNS role.

Attitude of Health Personnel↗