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Biomedical subjects

K Fraser

Publications and source records attributed to K Fraser.

At least 19 recordsLinked to original sources
PubMed2005

Cerebral vasospasm in patients with unruptured intracranial aneurysms.

Intracranial arterial vasospasm is a typical sequela of subarachnoid haemorrhage. The association between symptomatic vasospasm and unruptured aneurysms has been sporadically presented in the literature. The pathogenesis of this unusual entity is unclear. The published cases were collected in this review and analysed with regard to timing, clinical presentation and possible relationship with surgical factors. We also added an illustrative case which was recently observed in our department.

Cerebral Angiography↗
PubMed2005

Thrombosed giant intracavernous aneurysm with subsequent spontaneous ipsilateral carotid artery occlusion.

We report a case of a 47-year-old man with a giant thrombosed aneurysm of the right cavernous internal carotid artery who initially presented with headache, double vision and trigeminal numbness. He experienced subsequent asymtomatic proximal occlusion of the parent vessel, revealed by follow-up angiography. This case illustrates the possibility that a giant thrombosed aneurysm may exert enough compression upon the parent vessel to induce flow stasis with resultant intraluminal thrombosis progressing to occlude the entire parent artery.

Anticoagulants↗
PubMed2005

Atypical anti-psychotics in the real world--a naturalistic comparative outcome study.

BACKGROUND: There are few real life independent comparative studies of atypical antipsychotics. We prospectively examined five commonly used atypical antipychotics in the UK, without support from the pharmaceutical industry. METHOD: Prospective naturalistic systematic clinical evaluation. Patients being newly prescribed atypical anti-psychotics over a one year period were assessed by psychiatrists at initiation and after six months treatment using five outcome measures: clinical global impression; positive and negative psychotic symptoms; drug related side effects; and quality of life. RESULTS: 373 patients participated in total. Olanzapine and risperidone produced statistically significant reductions in all ratings at six months. Amisulpride, clozapine, and quetiapine were also studied. There was limited variance between the different drugs, although some sample sizes were small. CONCLUSION: Atypical anti-psychotics were found to be clinically effective, and produced similar outcomes. Routine monitoring of outcomes in psychiatry is feasible.

Adolescent↗
PubMed2004

Copasetic analysis: a framework for the blind analysis of microarray imagery.

From its conception, bioinformatics has been a multidisciplinary field which blends domain expert knowledge with new and existing processing techniques, all of which are focused on a common goal. Typically, these techniques have focused on the direct analysis of raw microarray image data. Unfortunately, this fails to utilise the image's full potential and in practice, this results in the lab technician having to guide the analysis algorithms. This paper presents a dynamic framework that aims to automate the process of microarray image analysis using a variety of techniques. An overview of the entire framework process is presented, the robustness of which is challenged throughout with a selection of real examples containing varying degrees of noise. The results show the potential of the proposed framework in its ability to determine slide layout accurately and perform analysis without prior structural knowledge. The algorithm achieves approximately, a 1 to 3 dB improved peak signal-to-noise ratio compared to conventional processing techniques like those implemented in GenePix when used by a trained operator. As far as the authors are aware, this is the first time such a comprehensive framework concept has been directly applied to the area of microarray image analysis.

Artificial Intelligence↗
PubMed2000

In vitro monitoring of rabbit anterior cruciate ligament damage by acoustic emission.

Anterior cruciate ligament (ACL) rupture is a major clinical problem leading to instability and degeneration of the knee joint. The problem is compounded by the limited ability of the ACL to heal when ruptured. The existing knowledge regarding the way the ACL ruptures is limited, and this investigation is an attempt to understand the nature of the ruptures using the rabbit as a model. A total of 16 rabbit tibia-ACL-femur complexes were stretched in tension to complete rupture. Four specimens were stretched to failure at a displacement rate of 0.5 mm/min and 12 specimens at 10 mm/min. Acoustic emission (AE) transducers were placed on both the tibia and the femur, and stress wave signals generated during the tensile test were recorded. Fibre fractures produced the highest amplitude signals with a relatively longer rise time. Other failure modes such as matrix failure and debonding produced lower amplitude signals with shorter rise times. We also noted that few events were recorded during the initial period of tensile loading (the elastic phase). The activity then increased significantly after maximum load was reached. The location information provided by the acoustic emission system was consistent with the final site of rupture. We have shown that AE can be used to characterise ligament damage, with fibre pull-outs and fibre fracture producing the highest signal amplitudes.

Acoustics↗
PubMed2000

Escape behaviour in the stomatopod crustacean Squilla mantis, and the evolution of the caridoid escape reaction.

The mantis shrimp Squilla mantis shows a graded series of avoidance/escape responses to visual and mechanical (vibration and touch) rostral stimuli. A low-threshold response is mediated by the simultaneous protraction of the thoracic walking legs and abdominal swimmerets and telson, producing a backwards 'lurch' or jump that can displace the animal by up to one-third of its body length, but leaves it facing in the same direction. A stronger response starts with similar limb protraction, but is followed by partial abdominal flexion. The maximal response also consists of limb protraction followed by abdominal flexion, but in this case the abdominal flexion is sufficiently vigorous to pull the animal into a tight vertical loop, which leaves it inverted and facing away from the stimulus. The animal then swims forward (away from the stimulus) and rights itself by executing a half-roll. A bilaterally paired, large-diameter, rapidly conducting axon in the dorsal region of the ventral nerve excites swimmeret protractor motoneurons in several ganglia and is likely to be the driver neuron for the limb-protraction response. The same neuron also excites unidentified abdominal trunk motoneurons, but less reliably. The escape response is a key feature of the malacostracan caridoid facies, and we provide the first detailed description of this response in a group that diverged early in malacostracan evolution. We show that the components of the escape response contrast strongly with those of the full caridoid reaction, and we provide physiological and behavioural evidence for the biological plausibility of a limb-before-tail thesis for the evolution of the escape response.

Animals↗
PubMed1999

Stochastic acquisition of Qa1 receptors during the development of fetal NK cells in vitro accounts in part but not in whole for the ability of these cells to distinguish between class I-sufficient and class I-deficient targets.

Fetal mouse NK cells are grossly deficient in the expression of Ly49 molecules yet show a limited ability to distinguish between wild-type and MHC class I-deficient target cells. In this paper we report that during their development in vitro from immature thymic progenitors, a proportion of C57BL/6 fetal NK cells acquires receptors for a soluble form of the nonclassical class I molecule Qa1b associated with the Qdm peptide, but not for soluble forms of the classical class I molecules Kb and Db. The acquisition of these Qa1 receptors occurs in a stochastic manner that is strictly controlled by cytokines, and in particular is strongly inhibited by IL-4. All fetal NK clones tested, including those that lack detectable Qa1 receptors, express mRNA for CD94 and for both inhibitory and noninhibitory members of the NKG2 family. Fetal NK cells lacking receptors for Qa1 (and also for classical class I molecules) cannot distinguish between wild-type and class I-deficient blasts but, surprisingly, distinguish efficiently between certain wild-type and class I-deficient tumor cells. A variant line that lacks several members of the NKG2 family kills both types of tumor cell equally well, suggesting the existence of NKG2-containing inhibitory receptors that recognize as yet undefined nonclassical class I molecules of restricted distribution.

Animals↗
PubMed1995

Sex differences in patients admitted to a regional secure unit.

The case notes of all admissions to a Regional Secure Unit over a 12-year period were examined. A higher proportion of females had a diagnosis of personality disorder. Women were less likely to have a prosecuted offence associated with admission but were more likely to be charged with fire-setting. Patients with personality disorder were more likely to be transferred to special hospitals. Women were nearly three times as likely as men to be transferred to maximum security and this was not accounted for by the excess of females with personality disorder. There was net movement of men out of special hospitals whereas the opposite was true for women. Possible explanations for this are discussed.

Adolescent↗
PubMed1994

Pharmacological characterization of multidrug resistant MRP-transfected human tumor cells.

We have previously identified and characterized a novel member of the ATP-binding cassette superfamily of transport proteins, multidrug resistance protein (MRP), and subsequently demonstrated that its overexpression is sufficient to confer multidrug resistance on previously sensitive cells (Cole et al., Science (Washington DC), 258: 1650-1654, 1992; Grant et al., Cancer Res. 54: 357-361, 1994). In the present study, we have transfected two different eukaryotic expression vectors containing MRP complementary DNA into HeLa cells to study the pharmacological phenotype produced exclusively by overexpression of human MRP. The drug resistance patterns of the two MRP-transfected cell populations were similar. They were characterized by a moderate (5- to 15-fold) level of resistance to doxorubicin, daunorubicin, epirubicin, vincristine, and etoposide, and a low (< or = 3-fold) level of resistance to taxol, vinblastine, and colchicine. The transfectants were not resistant to 9-alkyl anthracyclines, mitoxantrone, or cisplatin. The MRP-transfected cells were also resistant to some heavy metal anions including arsenite, arsenate, and trivalent and pentavalent antimonials but were not resistant to cadmium chloride. Accumulation of radiolabeled vincristine was reduced by 45% in the MRP-transfected cells and could be restored to the levels found in sensitive cells by depletion of ATP. Rates of vincristine efflux did not differ greatly in the sensitive and resistant cells. The cytotoxic effects of vincristine and doxorubicin could be enhanced in a dose-dependent fashion by coadministration of verapamil. Cyclosporin A also increased vincristine toxicity but had less effect on doxorubicin toxicity. The degree of chemosensitization by verapamil and cyclosporin A was similar in MRP-transfected cells and in cells transfected with the vector alone, suggesting that sensitization involved mechanisms independent of MRP expression. Verapamil and cyclosporin A caused a modest increase in vincristine accumulation in the resistant cells but did not restore levels to those of the sensitive cells. Taken together, these data indicate that drug-resistant cell lines generated by transfection with MRP complementary DNA display some but not all of the characteristics of MRP-overexpressing cell lines produced by drug selection in vitro. They further demonstrate that the multidrug resistance phenotype conferred by MRP is similar but not identical to that conferred by P-glycoprotein and includes resistance to arsenical and antimonial oxyanions.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Nurses' confirming/disconfirming responses to patients diagnosed with borderline personality disorder.

This study examines whether in group situations, patients with borderline personality disorder (BPD) received less empathic verbal responses from nurses than non-BPD patients. Nurses' feelings toward specific diagnoses were also examined. Twenty patient groups were observed involving 17 nurse leaders and 164 patients. Responses by the nurse leaders were rated using Heineken's Confirmation/Disconfirmation Rating Instrument. The staff response portion of Colson's Hospital Treatment Rating Scale was used to determine nurses's feelings toward specific diagnoses. The study provides some initial evidence that in actual practice situations nurses respond to BPD patients in a less empathic manner than to patients with other diagnoses.

Attitude of Health Personnel↗
PubMed1993

Transluminal angioplasty for atherosclerotic disease of the vertebral and basilar arteries.

Transluminal angioplasty for hemodynamically significant stenosis (> 70%) involving the posterior cerebral circulation is now being performed by the authors in selected cases. A total of 42 lesions affecting the vertebral or basilar artery have been successfully treated by percutaneous transluminal angioplasty techniques in 41 patients. The lesions involved the proximal vertebral artery in 34 cases, the distal vertebral artery in five, and the basilar artery in three. Patients were examined clinically at 1 to 3 and 6 to 12 months after angioplasty. Three (7.1%) permanent complications occurred, consisting of stroke in two cases and vessel rupture in one. There were four (9.5%) transient complications (< 30 minutes): two cases of vessel spasm and two of cerebral ischemia. Clinical follow-up examination demonstrated improvement of symptoms in 39 cases (92.9%). Radiographic follow-up studies demonstrated three cases (7.1%) of restenosis involving the proximal vertebral artery; two were treated by repeat angioplasty without complication, and the third is being followed clinically while the patient remains asymptomatic. In patients with significant atherosclerotic stenosis involving the vertebral or basilar artery territories, transluminal angioplasty may be of significant benefit in alleviating symptoms and improving blood flow to the posterior cerebral circulation.

Adult↗
PubMed1993

Plasma gamma-aminobutyric acid (GABA) is low in alcoholics.

Plasma levels of gamma-aminobutyric acid (GABA) were measured in male alcoholics on admission to inpatient treatment and at discharge after 3 to 4 weeks of abstinence. Free plasma GABA at discharge was significantly lower in alcoholics than in control subjects and specifically identified a subset of 35 percent of the alcoholic patients with levels below the normal range. However, levels of free plasma GABA in recently detoxified alcoholics on admission were not different from those of controls and had a significant positive correlation with liver enzymes and mean corpuscular volume. These data are compatible with a GABA deficit theory of alcoholism in a subset of alcoholics.

Adult↗
PubMed1991

Different types of rectification at electrical synapses made by a single crayfish neurone investigated experimentally and by computer simulation.

The rectification properties of electrical synapses made by the segmental giant (SG) neurone of crayfish (Pacifastacus leniusculus) were investigated. The SG acts as an interneurone, transmitting information from the giant command fibres (GFs) to the abdominal fast flexor (FF) motoneurones. The GF-SG (input) synapses are inwardly-rectifying electrical synapses, while the SG-FF (output) synapses are outwardly rectifying electrical synapses. This implies that a single neurone can make gap junction hemichannels with different rectification properties. The coupling coefficient of these synapses is dependent upon transjunctional potential. There is a standing gradient in resting potential between the GFs, SG and FFs, with the GFs the most hyperpolarized, and the FFs the most depolarized. The gradient thus biases each synapse into the low-conductance state under resting conditions. There is functional double rectification between the bilateral pairs of SGs within a single segment, such that depolarizing membrane potential changes of either SG pass to the other SG with less attenuation than do hyperpolarizing potential changes. Computer simulation suggests that this may result from coupling through the intermediary FF neurones.

Animals↗