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Biomedical subjects

M Hunter

Publications and source records attributed to M Hunter.

At least 37 records · Page 2Linked to original sources
PubMed2001

Structural ( n, m) determination of isolated single-wall carbon nanotubes by resonant Raman scattering.

We show that the Raman scattering technique can give complete structural information for one-dimensional systems, such as carbon nanotubes. Resonant confocal micro-Raman spectroscopy of an (n,m) individual single-wall nanotube makes it possible to assign its chirality uniquely by measuring one radial breathing mode frequency omega(RBM) and using the theory of resonant transitions. A unique chirality assignment can be made for both metallic and semiconducting nanotubes of diameter d(t), using the parameters gamma(0) = 2.9 eV and omega(RBM) = 248/d(t). For example, the strong RBM intensity observed at 156 cm(-1) for 785 nm laser excitation is assigned to the (13,10) metallic chiral nanotube on a Si/SiO2 surface.

Journal Article↗
PubMed2001

Novel mutations in the GALK1 gene in patients with galactokinase deficiency.

Galactokinase deficiency is an inborn error of galactose metabolism whose major clinical manifestation is the development of cataracts during the first months of life. Only 20 mutations have been reported to date and understanding of the functionally important domains of the galactokinase protein is still limited. Here we report four novel mutations in GALK1 that were identified in two unrelated patients with galactokinase deficiency. Three of these were amino acid substitutions: 1569C-->T in exon 2 (R68C); 7093C-->T in exon 6 (T288M) and 7538G-->C in exon 8 (A384P). In addition, a single base-pair deletion was found in exon 5 (2833delC), predicted to result in a shift of the reading frame and a premature termination codon at position 263. Some differences with the GALK1 sequence deposited in Genbank are also reported.

Adolescent↗
PubMed2001

Visual signal detection measured by event-related potentials.

Signal Detection tasks typically involve within-subject signal changes. Such a procedure does not lend itself to event-related potential (ERP) experiments where the need for averaging necessitates the maintenance of consistent stimulus parameters. In the present ERP study we adopt a novel approach to thresholding that allows within-subject signal manipulation. The Signal Detection task required the identification of letter targets, formed from dots, in a random dot field. ERP waveforms were segmented into three windows corresponding to N1, N2, and P300 components. Analysis shows that ERP variations are dependent on both task demands and response characteristics for N1, N2, and P300 components.

Adolescent↗
PubMed2001

Membrane cross-talk in the early distal tubule segment of frog kidney: role of calcium stores and chloride.

The activities of transport mechanisms in epithelial cells are generally coordinated in order to minimise disturbances in cellular ion content and volume. Furosemide, a potent inhibitor of transport in the renal diluting segment, up-regulates apical K+ channel activity following the release of calcium from intracellular stores. The signal pathway between furosemide application and this calcium release is not known. Single early distal tubule segments from frog kidney were permeabilised with saponin in order to monitor calcium levels within cytoplasmic stores using the calcium-sensitive dye, mag-fura. The uptake (or release) of calcium to (or from) stores was initiated by adding agents to the bath solution, which is in direct contact with the intracellular organelles. ATP promoted calcium uptake into stores, whereas ATP removal led to a slower, spontaneous calcium release. Following loading, calcium stores could be rapidly depleted by inositol 1,4,5-trisphosphate (IP3), but not ryanodine. Calcium release was evident upon lowering the "intracellular" chloride concentration from 12 to 4 mM, equivalent to the fall in chloride induced by furosemide in intact cells. These results suggest that intracellular chloride may function as a second messenger, mediating cross-talk between the apical membrane and intracellular calcium stores.

Adenosine Triphosphate↗
PubMed2001

Pain management program follow-ups. a national survey of current practice in the United Kingdom.

In the United Kingdom (UK), the number of multidisciplinary pain management programs (PMP) has sharply increased in the last decade. Treatment aims to effect long-term changes, yet arrangements for evaluating long-term treatment outcome in routine practice remain unknown. All PMPs identified in the UK were invited to provide information by mailed questionnaire on aspects of follow-up evaluation. Sixty-six of 70 PMPs identified were successfully contacted (94% response rate). Ten of 48 PMPs (21%) provided complete data and met suggested criteria for adequate length and rates of follow-up, and outcome measurement. Levels of staffing and content explained only a proportion of the variability seen. A general commitment to follow-up outcome evaluation by PMPs was identified but there was substantial variability among programs in length of follow-up, attendance rates, and outcome measurement. These findings raise issues about the consistency of follow-up evaluation across the UK and the ability of current arrangements in some PMPs to accurately determine the longer-term outcome of chronic pain patients. Incorporating follow-ups into existing desirable criteria and agreeing on core outcome measures are two options available to service providers.

Chronic Disease↗
PubMed2001

Influences of the N- and C-termini of the distal nephron inward rectifier, ROMK.

The inward rectifying potassium channels of the ROMK family are present in the distal nephron of the kidney. These channels have two membrane spanning portions, between which lies a hydrophobic domain thought to confer the majority of the conductive properties of the channel. The N- and C-termini are both intracellular. In this paper we have examined the contribution of the N- and C-termini to the pore by examining the interaction of Cs+ with the channels. ROMK1 has an additional 19 amino acids on its N-terminus in comparison to ROMK2. The C-terminus of ROMK2 was extended by addition of a streptavidin tag (sfROMK2). Currents were measured following expression in Xenopus oocytes using two-electrode voltage clamp. ROMK1, ROMK2 and sfROMK2 exhibited concentration- and voltage-dependent block of inward currents by extracellular Cs+. The Hill coefficients were not significantly different from one. The mean Kd values at 0 mV were 100.6 +/- 10.6, 63.1 +/- 3.9 and 40.6 +/- 9.4, respectively (p < 0.05). The electric distances (delta) were 0.94 +/- 0.06, 1.0 +/- 0.05 and 1.37 +/- 0.06 respectively. The delta of sfROMK2 was greater than either ROMK1 or ROMK2 (p < 0.001). ROMK1, ROMK2 and sfROMK2 are sensitive to extracellular Cs+. Block was both concentration- and voltage-dependent. sfROMK2 is most Cs+-sensitive. ROMK1 contains an additional N-terminal 19 amino acids. Thus the pore properties of these two isoforms are subtly different, and influenced by the N-terminus. The lower Kd in sfROMK2 suggests that the streptavidin tag, and perhaps the C-terminus, also affect the pore.

Animals↗
PubMed2001

Nursing staff's attitudes toward seclusion & restraint.

1. Staff preferred to treat patients as they themselves wanted to be treated. 2. More than one third of respondents did not view seclusion and restraint use as a time for a therapeutic intervention. 3. If staff are practicing from their belief patterns, they will choose interventions to avoid use of seclusion and restraint. 4. The majority of respondents preferred using medication to treat out-of-control behavior because they considered it less restrictive.

Attitude of Health Personnel↗
PubMed2001

Biophysical effects of pore mutations of ROMK1.

Potassium channels are ubiquitous, being present in all living organisms. These proteins share common structural elements, which confer common functional features. In general, all K+ channels have a high selectivity for K+, and are blocked by cations of similar dimensions, such as Cs+ and Ba2+. Mutations in the pore region tend to lead to either the total loss of function or K+ selectivity. We have made mutations to one of the most highly conserved residues of the pore, glycine-143, of the inward rectifier ROMK1 (Kir1.1), and examined the resulting channel properties in the Xenopus oocyte expression system with a two-electrode voltage clamp. Mutations G143A and G143R resulted in failure to express functional channels. Co-injection of wild-type ROMK1 cRNA with these mutants led to rescue of channel function, which was different from wild-type ROMK1. In both mutants, the sensitivity to Ba2+ and Cs+ was increased, the rate of onset of block by Ba2+ was enhanced, and the selectivity to potassium was reduced. Whereas the crystallographic evidence shows that cations bind to the carbonyl backbone of the pore-lining residues, the present results indicate that the side chains of these amino acids, which face away from the pore lining, also affect permeation.

Animals↗
PubMed2001

WMS-III performance in patients with temporal lobe epilepsy: group differences and individual classification.

The utility of the WMS-III in detecting lateralized impairment was examined in a large sample of patients with temporal lobe epilepsy. Methods of analysis included evaluation of group means on the various indexes and subtest scores, the use of ROC curves, and an examination of Auditory-Visual Index discrepancy scores. In addition, performance on immediate and delayed indexes in the auditory and the visual modality was compared within each group. Of the WMS-III scores, the Auditory-Visual Delayed Index difference score appeared most sensitive to side of temporal dysfunction, although patient classification rates were not within an acceptable range to have clinical utility. The ability to predict laterality based on statistically significant index score differences was particularly weak for those with left temporal dysfunction. The use of unusually large discrepancies led to improved prediction, however, the rarity of such scores in this population limits their usefulness. Although the utility of the WMS-III in detecting laterality may be limited in preoperative cases, the WMS-III may still hold considerable promise as a measure of memory in documenting baseline performance and in detecting those that may be at risk following surgery.

Adult↗
PubMed2000

An intracellular ATP-activated, calcium-permeable conductance on the basolateral membrane of single renal proximal tubule cells isolated from Rana temporaria.

1. The following study describes the properties of a non-selective cation channel, which has a unit conductance below the resolving power of the single channel technique, located on the basolateral membrane of single proximal tubule cells isolated from frog kidney. The conductance was examined using cell-attached, inside-out and outside-out patches. Due to the small single channel magnitude, macroscopic patch currents were measured. 2. Addition of 2 mM ATP to the intracellular surface of excised patches activated an outwardly rectifying conductance (MCANS): outward (Gout) and inward (Gin) conductances increased by 46.8 +/- 6.7 and 11.6 +/- 2.1 pS, respectively (n = 29). MCANS was more selective for cations than anions, with a cation:anion selectivity ratio of 10.1 +/- 1.7 (n = 7), but did not discriminate between Na+ and K+. It was more selective for Ca2+ over Na+, with a Ca2+:Na+ selectivity ratio of 4. 49 +/- 0.69 (n = 7). 3. In cell-attached patches addition of 100 microM strophanthidin to the bath increased both Gout and Gin. However this increase in conductance was absent in the presence of Gd3+, which inhibits MCANS. 4. These data suggest that single proximal tubule cells isolated from frog kidney contain an ATP-activated, non-selective cation conductance. The conductance does not discriminate between Na+ and K+, but is more selective for Ca2+ over Na+. Considering the prevailing electrochemical gradients for these ions, functional activation of the conductance would be expected to lead to a rise in intracellular Ca2+. MCANS is linked to the activity of the Na+, K+-ATPase and may therefore provide a link between the ATPase and K+ channel activity in the basolateral membrane and form an integral part of the pump-leak mechanism in transporting epithelia.

Adenosine Triphosphate↗
PubMed2000

EEG as a measure of developmental changes in the chicken brain.

Scalp-applied recording electrodes were used to monitor changes in basal EEG patterns in chickens during posthatch development. Frequency spectra produced by Fast Fourier Transform show a biphasic morphology in all chickens with one peak at about 6 Hz and another at 26 Hz. Changes in the lower frequency band show progressive development and provide a possible index of brain development. Both amplitude and dominant frequency of the spectra decrease between Weeks 3 and 8 posthatch, reaching adult levels between Weeks 5 and 7. These results suggest that modifications of basal EEG reflect the widespread functional changes in neuronal circuits occurring in chicken during the "synapse maturation" period between 3 and 8 weeks' posthatch.

Age Factors↗
PubMed2000

An evaluation of the Faces Pain Scale with young children.

The psychometric characteristics of the Faces Pain Scale (FPS) were evaluated in three groups of preschool and school-aged children (3. 5-4.5; 4.5-5.5 and 5.5-6.5 years, respectively). The FPS was adequately comprehended by even young children. It was easily administered and was valid and discriminating. It did not, however, possess the linear scalability claimed by its authors.

Child↗
PubMed2000

Theory of mind and executive functions in normal human aging and Parkinson's disease.

Although the majority of research in theory of mind (TOM) has focused on young children or individuals with autism, recent investigations have begun to look at TOM throughout the lifespan and in other neurological and psychiatric populations. Some have suggested that TOM may represent a dissociable, modular brain system that is related to, but separable, from other brain functions including executive functions (EF). Recently, studies have shown that TOM performance can be compromised following an acquired brain insult (e.g., damage to the right hemisphere). However, the relationship of such impaired TOM performance to other brain functions in these cases has not been explored. This study investigated the effects of both normal human aging and Parkinson's disease on TOM. The relationship of TOM performance and EF in these groups was also examined. The results suggested that although TOM performance appeared compromised in the group of individuals with Parkinson's disease, the elderly control participants were relatively unimpaired relative to younger individuals. Significant relationships between several measures of TOM and EF were also found. The implications of these findings, and also the finding that failure on one measure of TOM did not necessarily predict failure on all measures of TOM, are discussed.

Aged↗
PubMed2000

Implications of test revisions for research.

Test revisions are increasingly common in psychology and neuropsychology in particular. However, such revisions may alter in complex ways the kind of information obtained, and they may assess traits, abilities, and conditions in ways different from earlier versions. This article outlines some of the problems associated with the revision of tests facing clinicians and researchers. Three broad classes of revision are considered. Part 1 considers the aging of tests, part 2 concerns the aging of participants, and part 3 considers changes in test format. Although the article focuses largely on measures of intelligence and personality, the issues addressed in the article apply to other tests and assessment domains as well.

Aging↗
PubMed2000

A study of three cases of familial related agenesis of the corpus callosum.

This paper provides data on a family in which three members, all female, have been diagnosed as having agenesis of the corpus callosum. That all three acallosal individuals came from the same family and showed relatively uniform neuropsychological impairment and could be compared in similar terms with their "callosal" siblings, also female, provides a unique sample. Inter-hemispheric transfer, psychometric measures, and motor and cognitive function were examined in the acallosal individuals, all of whom had borderline to low-average intelligence, with results compared to their non-acallosal siblings. The data indicated that all acallosal individuals exhibited deficits with the cognitive tests indicating difficulties of inter-hemispheric transfer of tactile information, difficulties in some areas of memory and, at least as far as the children are concerned, a marked difference in Verbal IQ and Performance IQ.

Adolescent↗