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Biomedical subjects

M Harvey

Publications and source records attributed to M Harvey.

At least 19 recordsLinked to original sources
PubMed2000

Effects of visible and invisible cueing procedures on perceptual judgments in young and elderly subjects.

Healthy subjects were tested in two experiments to examine the effects of lateralized cues on line bisection and landmark judgments. The studies were designed to investigate whether bisection and landmark biases induced by cueing are simply a result of a direct perceptual lengthening of the cued part of the line caused by the fact that the cue is visible, thus creating a composite 'line plus cue' or whether cueing induces an attentional bias operating on judgments of spatial extent by either reducing the magnitude of the parts of the stimulus receiving 'less' attention or magnifying those parts receiving 'more'. Lateralized cues were either visible letter cues or invisible marks drawn with a leadless pencil either by the subject him/herself (Experiment 1) or the experimenter (Experiment 2). Comparable to a previous study (Mattingley, Pierson, Bradshaw, Phillips and Bradshaw, 1993, Neuropsychologia, 31, 1201-1215), the first experiment showed that only visible cues affected line bisection and landmark judgments thus favouring the perceptual explanation. The second study, however, revealed bisection and judgment biases for invisible as well as visible cues with the attended part of the line appearing subjectively longer. These results indicate that attentional modulations can increase the salience of a line in a similar vein to physical changes. It seems likely that the requirement of a motor response in Experiment 1 cancelled out all attentional properties supposedly induced by placing that invisible cue.

Adult↗
PubMed2000

Reaching movements may reveal the distorted topography of spatial representations after neglect.

It has been proposed that patients with spatial neglect fail to respond appropriately toward stimuli opposite their brain lesion because they have an impairment of directing attention. However, a disorder of 'intention' - or movement initiation - has also been demonstrated in this condition. Recently, the paths of neglect patients' reaches have been shown to be abnormally curved, but it is unclear whether this impairment is visual or motor. Here, we show for the first time that reaches to and from identical positions executed by three patients recovering from neglect are significantly more curved to visually defined targets compared to when the same targets are defined proprioceptively. These findings indicate that abnormal hand paths in neglect result from an impairment in the visual representation of space used to guide reaches but without any general failure of spatial representation of target position. Furthermore, the curved hand paths reveal how the topography of that representation is distorted in spatial neglect.

Aged↗
PubMed2000

Heritability of elevated factor VIII antigen levels in factor V Leiden families with thrombophilia.

Factor VIII activity (factor VIII:C) and factor VIII antigen (factor VIII:Ag) levels above 150 IU/dl are associated with a five- to sixfold increased risk of venous thrombosis compared with levels < 100 IU/dl. These high levels are present in 25% of patients with a first episode of deep-vein thrombosis and in 11% of healthy controls. von Willebrand factor (VWF) and blood group are important determinants of the factor VIII level in plasma and therefore contribute to thrombotic risk, while factor VIII appears to be the final effector. Previously, we found familial clustering of factor VIII:C levels in women, which remained after adjustment for VWF and blood group. In the present study, we analysed the familial influence on factor VIII:Ag levels exceeding 150 IU/dl in 12 large families with thrombophilia in which high factor VIII:Ag levels contribute to thrombotic risk. As expected, blood group was a main determinant of the plasma factor VIII level: 58 relatives (32%) had factor VIII levels above 150 IU/dl and 50 (86%) of these had blood group non-O. After adjustment for blood group and age, we found an association between factor VIII:Ag levels in sister pairs (0.35, P = 0.003), brother pairs (0.35, P = 0.003), brother-sister pairs (0.35, P < 0.001) and in mother-son pairs (0.45, P = 0.02), but not in father-daughter or father-son pairs. The familial aggregation test was strongly positive for factor VIII:Ag levels (P < 0.001) and remained so after adjustment for the influence of blood group. We conclude that high factor VIII:Ag levels are a highly prevalent risk factor for venous thrombosis and contribute to risk in families with thrombophilia, and that these high levels are likely to be genetically determined by factors other than just blood group.

Adolescent↗
PubMed2000

The coordination of bimanual prehension movements in a centrally deafferented patient.

Many everyday tasks require that we use our hands co-operatively, for example, when unscrewing a jar. For tasks where both hands are required to perform the same action, a common motor programme can be used. However, where each hand needs to perform a different action, some degree of independent control of each hand is required. We examined the coordination of bimanual movement kinematics in a female patient recovering from a cerebrovascular accident involving anterior regions of the parietal lobe of the right hemisphere, which resulted in a dense hemianaesthesia of her left arm. Our results indicate that unimanual movements executed by our patient using her non-sensate hand are relatively unimpaired. In contrast, during bimanual movements, reaches executed by our patient using her non-sensate hand show gross directional errors and spatiotemporal irregularities, including the inappropriate coupling of movement velocities. These data are discussed with reference to the role played by limb proprioception in the planning and control of prehension movements.

Aged↗
PubMed2000

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Explore the source record for details and available documents.

Journal Article↗
PubMed1999

Antitransferrin receptor antibody-RNase fusion protein expressed in the mammary gland of transgenic mice.

Antibodies fused to human enzymes offer an alternative to specifically targeting tumors with antibodies linked to plant or bacterial toxins. Since large amounts of these reagents can be administered without eliciting non-specific toxicities, efficient methods of production are needed. The goal of this work was to express a complex immunoenzyme fusion protein (immunotoxin) in the mammary gland of transgenic mice. A chimeric mouse/human antibody directed against the human transferrin receptor (E6) was fused at its CH2 domain to the gene for a human angiogenic ribonuclease, angiogenin (Ang). It was expressed in the mammary gland of mice and secreted into mouse milk. Expression levels in milk were approximately 0.8 g/l. The chimeric protein retained antibody binding activity and protein synthesis inhibitory activity equivalent to that of free Ang. It was specifically cytotoxic to human tumor cells in vitro.

Animals↗
PubMed1999

Effects of dopamine and aminophylline on contrast-induced acute renal failure after coronary angioplasty in patients with preexisting renal insufficiency.

In phase 1 of this study, 60 patients undergoing coronary angioplasty were randomized to receive saline, dopamine, or aminophylline; the overall incidence of contrast-induced renal failure was 38%, without difference among the 3 groups. In phase 2 of this study, 72 patients with established contrast-induced renal failure were randomized to receive saline or dopamine; dopamine had a deleterious effect on the severity of renal failure, prolonging the course.

Acute Kidney Injury↗
PubMed1999

Residual perceptual distortion in 'recovered' hemispatial neglect.

In most neglect patients, line bisection errors become smaller on repeated tests over the months following the lesion. We have tried to determine in two typical patients whether this is because of a real reduction in the perceptual distortions that appear to underlie line bisection errors in neglect, or whether it reflects a learned behavioural strategy to counteract those perceptual biases. We tested the patients on two occasions (2 and 12 months post-stroke), on line bisection and also on the 'Landmark' task. The data indicated that at the first testing session both patients showed strong 'perceptual' neglect, making large rightward errors in the standard bisection task and uniformly leftward pointing in the Landmark task. On the second occasion, as expected, both patients showed a marked recovery when tested with the line bisection task, making only very small errors. In contrast, their landmark performance was still markedly biased in the same direction as before. These findings suggest that despite their apparent recovery on the bisection task, both patients still experience some form of perceptual distortion of horizontal lines. It is suggested that the Landmark task may provide a sensitive means for identifying real recovery of the underlying perceptual deficit.

Adaptation, Psychological↗
PubMed1999

Factor-based prototypes of the Millon Adolescent Clinical Inventory in adolescents referred for residential treatment.

Although well received by the clinical community, there have been few published reports on the use of the Millon Adolescent Clinical Inventory (MACI). There have been no published studies describing use of the MACI with a residential treatment population. In addition, there have been no published reports investigating the factor structure of the MACI. A principal components factor analysis was performed for all MACI scales and sex for 251 adolescents referred to a residential treatment facility. Five factors were found accounting for 77.4% of the variance. Factor-based prototypes were generated from these results: Factor 1 defines a prototype for Defiant Externalizers, Factor 2 for Intrapunitive Ambivalent Types, Factor 3 for Inadequate Avoidants, Factor 4 for Self-Deprecating Depressives, and Factor 5 for Reactive Abused Types. Prototype descriptions and clinical vignettes are included for each of the 5 factor-based prototypes. These results are consistent with our clinical experience with this population. Prototype analysis may offer a powerful way of enhancing the utility of the MACI in clinical settings.

Adolescent↗
PubMed1998

A "pre-satiety sequence" in rats drinking sucrose solutions.

Food-deprived rats were given intermittent access or, in a replication, continuous access to a 20% sucrose solution. Both drinking and nondrinking behaviors were recorded. During the ensuing drinking bout, latency of lapping after snout apposition, and duration of lapping bouts, did not change. Approaches to the sipper tube usually eventuated in lapping, though aborted approaches increased in frequency late in the session. Drinking was interrupted by nondrinking behaviors which appeared in a characteristic rostro-caudal sequence: partial head withdrawal from the drinking aperture, then full head withdrawal, then movements of the front paws, then movement of the hind paws with full-body locomotion. All these behavioral changes occurred before there was any appreciable reduction in rate of lapping.

Animals↗
PubMed1998

Visual size processing in spatial neglect.

Evidence from the use of the landmark task and from two size-matching tasks shows that many patients with left-sided neglect systematically under-perceive visual extent in leftward parts of space. This perceptual distortion of size serves to explain the occurrence of rightward line-bisection errors in most neglect patients. One possibility is that attentional biases of a chronic nature might underlie these perceptual changes seen in neglect patients. But contrary to this idea, we have found that attentional cueing in the landmark task causes changes in neglect patients exactly opposite to those seen in healthy subjects. The distortions of size perception seen in neglect could instead be caused by a high-level alteration of visual processing rather than by an attentional bias. In order to explore which visual stream of cortical processing might be compromised in such a disorder, we have begun to examine neglect patients on visuomotor as well as perceptual tasks. We have found clear evidence in one patient for intact grip scaling for object size in the neglected half of space, despite gross perceptual underestimations of the same objects. This result suggests that neglect can occur without major disruption of the dorsal stream, and may result instead from damage to a cortical system whose predominant visual input comes from the ventral stream.

Attention↗
PubMed1998

Influence of right ventricular site of stimulation and infarct location on the inducibility of ventricular tachycardia in patients with coronary artery disease.

No prior studies have evaluated the relationship between the site of right ventricular stimulation, the site of prior infarction, and the inducibility of ventricular tachycardia (VT). This study was performed to determine if the location of pathologic Q waves influences the inducibility of VT at various right ventricular sites in patients with coronary artery disease (CAD) and a history of myocardial infarction (MI). In 30 patients with a history of sustained, monomorphic VT, CAD, prior MI, and pathologic Q waves, programmed ventricular stimulation was performed at the right ventricular apex, septum, and outflow tract, in random order. There was electrocardiographic evidence of an MI that was inferior in 11 patients, anterior in 10 patients, and both inferior and anterior in 9 patients. Sustained, monomorphic VT was induced in 27 of 30 patients (90%). There were no significant differences among the three sites in the rate of inducibility of VT. The rate of inducible VT at each of the three right ventricular sites was not affected by the location of prior infarction. In conclusion, among patients with sustained, monomorphic VT, CAD, and a history of MI, the incidence of inducible sustained, monomorphic VT is not influenced by the location of prior infarction, regardless of whether programmed ventricular stimulation is performed at the right ventricular apex, septum, or outflow tract.

Cardiac Pacing, Artificial↗
PubMed1998

A comparative study on the efficacy of CD8-positive cells in enhancing allogeneic bone marrow engraftment: cell sorting vs microbead selection.

We have used a superparamagnetic microbead selection system to positively select a murine bone marrow CD8+ cell population. The functional ability of these cells to enhance allogeneic bone marrow engraftment was compared with that of fluorescence activated cell sorter purified CD8+ cells. The CD8+ cell population prepared by the microbead selection procedure was as effective as cell sorter purified CD8+ cells in enhancing T cell-depleted allogeneic bone marrow engraftment in lethally irradiated mice. Phenotypic characterization of these cells shows that most of these CD8+ cells express CD3 and the T cell antigen receptor complex.

Animals↗
PubMed1998

Characterization of the ABO blood group genes in macaques: evidence for convergent evolution.

The ABO blood group system is known to act as a major transplantation barrier in primates. Different primate species share the presence of A and B antigens. The polymorphism of the macaque ABO blood group genes was analyzed by cloning and sequencing the exon 7 region. In the case of the rhesus macaque (Macaca mulatta) and cynomolgus monkey (Macaca fascicularis) we were able to identify ABO blood group gene segments which cluster into two lineages, namely: *A/*O1 and *B. In addition allelic variation was observed. The 2 amino acid replacements at positions 266 and 268, which are thought to be crucial for A or B transferase activity, could be confirmed for both macaque species. Comparison of primate sequences shows that A and B reactivity was generated independently from each other in the hominoids and Old World monkey lineages. Hence, the primate A and B blood group genes are subject to convergent evolution.

ABO Blood-Group System↗
PubMed1998

Making changes to improve the intensive care unit experience for patients and their families.

With the technology explosion and scientific advances in the field of critical care in the past three decades came an era in which ICUs were referred to as an arena for punitive survivalists. Although clinicians have developed an increased ability to improve the quality and quantity of life for patients in the long term post discharge, patients and their families often suffered more than is necessary in the short term, during the critical care phase of the illness. It is well documented that physiologic and psychologic stress impacts negatively on both short-term and long-term patient outcomes. In the last 10 yrs, the attention of individual caregivers, units, organizations, and researchers has turned to improving the ICU experience for patients and families. This article reviews the relevant literature and also reports the experience of those who have created and applied unique strategies that address the patient and family needs, thus promoting their comfort and relieving their distress. Although more outcome studies are needed in this area of care, applying some of the lessons already learned can significantly improve the ICU experience for most patients and families.

Communication↗
PubMed1997

Grip force scaling after hemispatial neglect.

Spatial neglect has been explained as an impairment in the representation of extrapersonal space. One account suggests that representations of extrapersonal space are spatially compressed following neglect. In support of this view it has been demonstrated that neglect patients systematically underestimate the size of stimuli presented in their left hemifield. In the current study we investigated this phenomena by obtaining an indirect measure of perceived object size - the scaling of grip force during prehension. We demonstrate for the first time that neglect patients show increased levels of grip force for objects presented in their left hemifield. This finding is discussed with reference to a proposed distinction between visual processing used for object recognition, and visual processing used to guide action.

Aged↗
PubMed1997

Isolation, cloning and characterisation of the abiI gene from Lactococcus lactis subsp. lactis M138 encoding abortive phage infection.

Plasmid pND852 (56 kb) encodes nisin resistance and was isolated from Lactococcus lactis ssp lactis (L. lactis) M138 by conjugation to L. lactis LM0230. It conferred strong resistance to the isometric-headed phage phi 712 and partial resistance to the prolate-headed phage phi c2. A 2.6 kb HpaII fragment encoding phage resistance was cloned into the streptococcal/Bacillus hybrid vector pGB301 to generate pND817. The mechanism of phage resistance encoded by pND817 involved abortive infection and this was illustrated by a reduction in burst size from 166 to 6 at 30 degrees C and from 160 to 90 at 37 degrees C. Partial resistance was therefore retained at 37 degrees C. DNA sequencing revealed that the abortive infection was encoded by a single open reading frame (ORF), designated abiI, encoding a 332 amino acid protein. Neither abiI nor the predicted product showed significant homology to any existing sequence in the GenBank database. Frame shift mutation at the unique EcoRI site within the ORF resulted in loss of the Abi+ phenotype, confirming that the ORF is responsible for the encoded phage resistance.

Amino Acid Sequence↗