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Biomedical subjects

M J Harrison

Publications and source records attributed to M J Harrison.

At least 109 records · Page 6Linked to original sources
PubMed1996

A sugar transporter from Medicago truncatula: altered expression pattern in roots during vesicular-arbuscular (VA) mycorrhizal associations.

A cDNA clone encoding a hexose transporter has been isolated from a library prepared from Medicago truncatula roots colonized by the mycorrhizal fungus Glomus versiforme. The clone (Mtst1) represents a M. truncatula gene and expression studies in yeast indicate that the encoded protein transports glucose and fructose but not sucrose. Transcripts corresponding to Mtst1 are expressed in leaves, stems and roots of M. truncatula, with the highest levels of expression in roots. In the roots, Mtst1 transcripts were detected in two distinct locations; the phloem fiber cells of the vascular tissue, and the cells of the root tip. Mtst1 expression in the roots is regulated in response to colonization by G. versiforme; transcript levels increased two- to fourfold in both M. truncatula and M. sativa following colonization by G. versiforme but did not increase during the unsuccessful interaction between G. versiforme and a M. sativa myc- mutant, suggesting that the increase in Mtst1 transcripts in the successful mycorrhizal interaction is correlated with internal growth of the fungus and potentially with a functioning symbiosis. Mtst1 transcripts were also detected in the cortical cells of the mycorrhizal root, specifically in areas of the root that were highly colonized by the mycorrhizal fungus. Thus, the formation of a symbiotic association with a VA mycorrhizal fungus is accompanied by a change in the cell type-specific expression of a transporter that potentially functions to supply sugars to root cells critically involved in the symbiotic association.

Amino Acid Sequence↗
PubMed1996

Malignant hyperthermia--a large kindred linked to the RYR1 gene.

Malignant hyperthermia susceptibility is genetically heterogeneous. The ryanodine receptor gene on the long arm of chromosome 19 represents an important candidate gene but not all families with malignant hyperthermia demonstrate ryanodine receptor mutations or linkage to this region of 19q. Linkage to chromosome 17 in the region of the adult muscle sodium channel alpha subunit gene has been suggested in some families; others are not linked to either of these loci. For most families the in vitro muscle contracture test remains the only reliable method of predicting susceptibility to malignant hyperthermia. We have performed linkage analysis in a large family group with malignant hyperthermia in which the in vitro muscle contracture test had been carried out using the procedure standardised by the European Malignant Hyperthermia Group. None of the published ryanodine receptor gene mutations associated with malignant hyperthermia susceptibility were detected in affected individuals but linkage to intragenic ryanodine receptor markers strongly suggest that this gene is involved in malignant hyperthermia susceptibility in this family. This enabled accurate predictive testing by DNA analysis in 11 untested subjects at 50% risk.

Calcium Channels↗
PubMed1996

Acute lumbosacral polyradiculopathy due to cytomegalovirus in advanced HIV disease: CSF findings in 17 patients.

OBJECTIVES: To describe the abnormalities in CSF from HIV infected patients with acute lumbosacral polyradiculopathy (ALP) caused by cytomegalovirus (CMV) infection. METHODS: Retrospective case notes and laboratory records were reviewed for 17 consecutive patients with CMV associated ALP admitted to specialist HIV/AIDS units at UCL Hospitals and Chelsea and Westminster Hospital. RESULTS: Infection with CMV was confirmed by detection of CMV DNA by polymerase chain reaction amplification in 15 patients (all of whom were negative by culture), by culture in one patient, and by objective clinical response to anti-CMV treatment in one patient. Only nine patients had a CSF pleocytosis 28-1142 (median 150) cells/mm3; in seven there was a polymorphonuclear (PMN) leucocyte preponderance. Protein concentrations in CSF were moderately or considerably raised in 13 patients; CSF: plasma glucose ratios were < or = 50% in five patients. Two patients had no pleocytosis, normal CSF: plasma glucose, and normal or near normal protein values. CONCLUSIONS: Abnormalities in CSF in CMV associated ALP are varied: only 50% of patients have a "typical" PMN preponderant pleocytosis. The diagnosis of this condition should not rely on demonstration of a PMN preponderant pleocytosis, but on identification of CMV DNA in CSF and the exclusion of other opportunistic infections and lymphoma in order that specific anti-CMV treatment may be instituted.

AIDS-Related Opportunistic Infections↗
PubMed1996

Comparison of magnetic and electrical phrenic nerve stimulation in assessment of diaphragmatic contractility.

Unlike the standard electrical approach, cervical magnetic stimulation of the phrenic nerves is less painful and achieves a constant degree of diaphragmatic recruitment, features that should enhance its applicability in a clinical setting. An unexplained phenomenon is the greater transdiaphragmatic twitch pressure (Pditw) with magnetic vs. electrical stimulation. We hypothesized that this greater Pditw is due to coactivation of extradiaphragmatic muscles. Because impedance to rib cage expansion is increased at high lung volumes and efficiency of extradiaphragmatic muscles is less than that of the diaphragm, we reasoned that the difference between electrical Pditw and magnetic Pditw would be less evident at high volumes than at end-expiratory lung volume. In human volunteers, magnetic Pditw and electrical Pditw were 37.7 +/- 1.9 (SE) and 32.3 +/- 2.2 cmH2O, respectively, at end-expiratory lung volume (P < 0.005) and 24.0 +/- 2.9 and 27.2 +/- 2.8 cmH2O, respectively, at one-half inspiratory capacity (not significant); at total lung capacity, magnetic Pditw was less than electrical Pditw (10.6 +/- 0.8 and 16.2 +/- 2.9 cmH2O, respectively; P < 0.05). Magnetic stimulation caused significant extradiaphragmatic muscle depolarization and rib cage expansion, whereas electrical stimulation caused virtually no extradiaphragmatic muscle depolarization and rib cage deflation. Despite these differences, the induction of respiratory muscle fatigue produced reductions in both electrical and magnetic Pditw values (P < 0.01), which were of similar magnitude and closely correlated (r = 0.96). In conclusion, magnetic stimulation recruits both extradiaphragmatic and diaphragmatic muscles, and it is equally as effective as electrical stimulation in detecting diaphragmatic fatigue.

Adult↗
PubMed1996

Blood-Brain Barrier Integrity in HIV Infection:Evaluation by Contrast-Enhanced Magnetic Resonance Imaging.

This study assesses the integrity of the blood-brain barrier (BBB) in human immunodeficiency virus (HIV) seropositive individuals to magnetic resonance imaging (MRI) contrast agent Gd-DTPA. Twelve HIV seropositive patients and six control subjects had T2-weighted and serial pre- and post-contrast TI-weighted MRI. Ten of the twelve seropositive patients demonstrated white matter hyperintensity with or without atrophy on T2-weighted MRI and 8/10 who underwent neurological examination demonstrated neurological abnormalities. No statistically significant differences of trends in white matter pixel values were observed between pre- and post-contrast scans in any of the patients or controls. Serial T1-weighted MRI does not demonstrate any change in the integrity of the BBB to Gd-DTPA in HIV seropositive patients, regardless of the presence or absence of white matter hyperintensity with or without atrophy on T2-weighted MRI or clinical signs of HIV-I associated with cognitive/motor complex.

Blood-Brain Barrier↗
PubMed1996

A new method for inserting the atrial end of a ventriculoatrial shunt. Technical note.

This technical note describes a simple percutaneous mechanism for placement of the atrial end of ventriculoatrial shunts. The method is fast, efficient, and involves no neck dissection. No special equipment is required. Placement involves the technique of central line insertion familiar to all surgeons. This new method has been used successfully in one adult and one pediatric patient.

Aged↗
PubMed1996

Gender differences in the support networks of caregivers.

Nurses in home care and long-term care settings play an important role in assisting family caregivers of elders who are cognitively impaired to sustain personal support while caregiving. Research has shown that such support is associated with positive health status. The characteristics of the caregiver's social network provide information about the potential for support. The purpose of this study was to describe and compare the social networks of men and women caregivers in terms of the composition of the social network and the size of the available, utilized and conflicted social networks. The possible relationship between the demographic characteristics of caregivers and the size and composition of their social networks was also examined. In comparison to men, the conflicted social networks of women were larger and comprised of more family members. For women, age, years of caregiving and socioeconomic status were not significantly related to the size of their social network. However, younger men and men of higher socioeconomic status reported significantly larger available social networks than other men. Knowledge of the gender differences in network size and composition that were identified in this study contributes to nurses' ability to identify caregivers who may be at risk for inadequate social support. In conjunction with the findings from related studies these results have implications for nursing assessment and intervention in home care and long-term care settings.

Adult↗
PubMed1995

A phosphate transporter from the mycorrhizal fungus Glomus versiforme.

Vesicular-arbuscular (VA) mycorrhizal fungi form symbiotic associations with the roots of most terrestrial plants, including many agriculturally important crop species. The fungi colonize the cortex of the root to obtain carbon from their plant host, while assisting the plant with the uptake of phosphate and other mineral nutrients from the soil. This association is beneficial to the plant, because phosphate is essential for plant growth and development, especially during growth under nutrient-limiting conditions. Molecular genetic studies of these fungi and their interaction with plants have been limited owing to the obligate symbiotic nature of the VA fungi, so the molecular mechanisms underlying fungal-mediated uptake and translocation of phosphate from the soil to the plant remain unknown. Here we begin to investigate this process by identifying a complementary DNA that encodes a transmembrane phosphate transporter (GvPT) from Glomus versiforme, a VA mycorrhizal fungus. The function of the protein encoded by GvPT was confirmed by complementation of a yeast phosphate transport mutant. Expression of GvPT was localized to the external hyphae of G. versiforme during mycorrhizal associations, these being the initial site of phosphate uptake from the soil.

Amino Acid Sequence↗
PubMed1995

Cis elements and potential trans-acting factors for the developmental regulation of the Phaseolus vulgaris CHS15 promoter.

A nuclear factor (SBF-1) has previously been identified in Phaseolus vulgaris L. (bean) suspension cell nuclear extracts that binds in vitro to three DNase I-footprinted elements (SBF-1 boxes I, II, and III, 5' to 3') in the 5' region of the bean CHS15 (chalcone synthase) gene promoter. To define the functional role of the three SBF-1 boxes in development, we examined transgenic tobacco plants carrying a series of nested CHS15 promoter-beta-glucuronidase (GUS) fusions for GUS activity by histochemical staining. We show that the CHS15 promoter deleted to position -173 and lacking all three SBF-1 boxes directs the same qualitative pattern of expression in initiating lateral roots and in developing seeds as the full length promoter (-326). Thus, activation of expression in these organs is mediated by sequence elements located downstream of the three SBF-1 boxes. However, specific deletions within the -326 to -173 region modulate expression. Thus, deletion of box II abolishes GUS activity in initiating lateral roots. Further deletion of box III fails to restore expression but subsequent deletion of an additional 43 bp to position -173 re-establishes expression. We show that sequence-specific DNA-binding activities consistent with these results are present in nuclear extracts of bean roots and seeds. These studies reveal cis elements within the CHS15 promoter, and potential trans factors, that permit organ- and tissue-specific developmental patterns of regulation to be combined with a flexible response to environmental cues.

Acyltransferases↗
PubMed1995

Neurologic complications of coronary artery bypass grafting: diffuse or focal ischemia?

The central nervous system complications arising during or shortly after coronary artery bypass grafting are due to cerebral ischemia associated with hypotension and to embolism. Hemodynamic compromise produces a spectrum of disturbance of consciousness and mentation ranging from brain death and coma through the chronic vegetative state to mild confusion. Watershed infarction may add to this picture focal deficits such as visual disorientation and cortical field defects or bibrachial weakness (the "man in a barrel" syndrome). Macroembolism accounts for most perioperative strokes and is related to cardiac arrhythmias, to intracardiac thrombus, and particularly to the severity and friable nature of any aortic atheroma. Microembolism can cause focal problems in the watershed territory but is normally responsible for diffuse changes as seen in the neuropsychologic sequelae of coronary artery bypass grafting. Coexistent carotid artery disease rarely contributes to the postoperative neurologic changes.

Brain Ischemia↗
PubMed1995

Short echo time proton spectroscopy of the brain in HIV infection/AIDS.

Short echo time proton spectra have been acquired from the brains of 30 male homosexual Acquired Immunodeficiency Syndrome (AIDS) patients and 12 age-matched control subjects on a 1.5 T MR system. The acquisition protocol used stimulated acquisition voxel localisation with a voxel size of 8 ml and repeat, echo, and mixing times of 5000, 20, and 30 ms, respectively. A single 25.6-ms Gaussian water suppression pulse was used with 128 spectral acquisitions and the data were eddy current corrected using a water reference. Baseline-corrected spectra were nonlinearly least squares fitted to a model function consisting of Gaussian functions representing the major metabolites reported in short echo proton spectra. Results indicate that the N-acetyl/creatine (NA/Cr) ratio is significantly reduced by 20% in AIDS patients [NA/Cr = 1.91 (0.51)] compared to control subjects [NA/Cr = 2.37 (0.25)] at short echo times.

AIDS Dementia Complex↗
PubMed1995

Women in transition: access and barriers to social support.

As little is known about how support assists individuals during a normative life transition, this qualitative, prospective study explored how women chose sources of informal support. Women having their first child, returning to work after an extended absence or recently retired from full-time employment were interviewed. Support during a life transition was described as having someone who would listen while the woman problem-solved. Women preferred to get their support from close family members or others experiencing a similar life transition. A number of barriers to the use of support were identified: perception that the use of support would be a burden on others, lack of reciprocity, reluctance to ask for support, and nonsupportive messages included within supportive actions. The transition often took more than 2 years to complete and, for a subgroup of women, involved major changes in their self-expectations and ability to access support. The findings identify areas that nurses should consider in health promotion activities with women who are experiencing these life transitions.

Adult↗
PubMed1995

Using critical feminist principles to analyze programs for low-income urban women.

Public health nurses are committed to promoting the health of vulnerable populations, including the economically disadvantaged. One of the perspectives that can be used to work with low-income women is feminist theory. In this paper, we analyze program descriptions from 45 community agencies whose services are accessed by urban low-income women. The purpose of the analysis is to identify congruence between agency programs and selected feminist principles. As a result of the content analysis, empirical referents and examples were identified for each principle. Public health nursing programs can incorporate feminist principles by responding to the perspectives of the vulnerable and facilitating their efforts to change the conditions that led to their vulnerability. Questions are presented that could guide public health nurses in stimulating reflection and in facilitating dialogue in the process of developing programs for low-income women.

Alberta↗
PubMed1995

Changes in cerebral blood flow as monitored by transcranial Doppler during voluntary hyperventilation and their effect on the electroencephalogram.

Hyperventilation results in a fall in carbon dioxide concentration, a fall in cerebral blood flow, and slowing of activity on the electroencephalogram. The temporal relationship and duration of these responses are uncertain, and were investigated using simultaneous monitoring of cerebral blood flow velocity and of the electroencephalograph, with end-tidal carbon dioxide monitoring. Sixteen patients and 9 normal volunteers were studied. Cerebral blood flow velocity in the middle cerebral artery was measured using transcranial Doppler sonography during 3 minutes of hyperventilation and during a 3-minute recovery period. Electroencephalographic recordings were rated by both visual score and measurement of the dominant posterior frequency. End-tidal expired carbon dioxide tension was monitored during the same hyperventilation protocol in the volunteers. Flow velocity fell rapidly during active hyperventilation. Electroencephalographic slowing closely correlated with the decrease in flow velocity (r = 0.86), but lagged behind it. In healthy volunteers capnographic records showed a very tight coupling between end-tidal carbon dioxide concentration and flow velocity (r = 0.94). Three minutes after hyperventilation, carbon dioxide concentration, cerebral blood flow velocity, and electroencephalographic activity were still not back to the resting state. The fall in both cerebral blood flow velocity and carbon dioxide concentration are related to but precede electroencephalographic slowing. The abnormalities persist for at least 3 minutes after hyperventilation and this must be taken into account in clinical electroencephalography. Transcranial Doppler sonography is well suited to monitoring short-term changes in the cerebral circulation.

Adult↗