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Biomedical subjects

M Lawton

Publications and source records attributed to M Lawton.

13 recordsLinked to original sources
PubMed2005

A comparison of airborne ergosterol, glucan and Air-O-Cell data in relation to physical assessments of mold damage and some other parameters.

UNLABELLED: We report here a comparison of long duration air samples in 110 homes where the material collected on open faced filter cassettes was analyzed for beta 1,3-d glucan, ergosterol, cholesterol and endotoxin. These data were then compared to careful estimates of visible mold and Air-O-Cell data. All the values found except cholesterol were of a similar magnitude to values reported in the limited number of studies available. Glucan was measured with a factor G based assay of the Limulus Amebocyte Lysate followed by size exclusion chromatography. This showed that the majority of airborne glucan found in these houses was fungal in origin arising from both yeasts and intact spores, as well as hyphal and spore fragments. Hyphal and spore fragments together represented 16% of the intact spore counts but over a broad range. Correlations between airborne glucan were strong for ergosterol and visible mold. However, airborne ergosterol was more highly correlated to visible mold than glucan. Endotoxin and Air-O-Cell measurements were poorly or not related to the other measures in the study. This study provides confidence that long duration air samples of the toxin glucan and ergosterol are related to building damage. PRACTICAL IMPLICATIONS: Some studies of damp buildings have shown a relationship between extent of water/mold damage and symptoms. This study compared long duration air samples for glucan and ergosterol to extent of visible mold in houses measuring also the nature of the glucans present. Both measures were highly correlated to extent of visible mold damage in the houses; ergosterol was somewhat superior. Spore counts or prevalence of Asp/Pen in Air-O-Cell samples was not related to extent of visible mold damage but the observation of hyphal fragments was more likely when mold damage was present. This indicates that rigorous assessment of mold damage is a useful measure.

Air Pollution, Indoor↗
PubMed2002

Plateau potentials in hindlimb motoneurones of female cats under anaesthesia.

Central respiratory drive potentials (CRDPs) were observed in intracellular recordings from hindlimb motoneurones of anaesthetized, paralysed, ovariohysterectomized female cats, artificially ventilated so as to have a strong respiratory drive under hyperoxic hypercapnea. The animals comprised two groups: three animals treated for 7 days with oestradiol benzoate (oestrous), and three untreated (non-oestrous). Several features of the CRDPs suggested the involvement of voltage-sensitive channels, including variability in the CRDP amplitude and potentiation of the CRDP by depolarizing currents. Clear plateau potentials, related to or triggered by depolarizing phases of the CRDPs, occurred in six motoneurones, three in response to depolarizing currents, three spontaneously. This is the first report of plateau potentials in mammalian motoneurones under anaesthesia. The mechanisms accessed here by the respiratory inputs are deduced to be particularly potent, perhaps because of a distal dendritic location. Plateau-like effects were more common in the oestrous animals, which suggests a specific role for the plateau potentials in the production of the stereotyped movements of female receptive behaviour.

Action Potentials↗
PubMed2001

Programmed cell death, mitochondria and the plant hypersensitive response.

The plant response to attempted infection by microbial pathogens is often accompanied by rapid cell death in and around the initial infection site, a reaction known as the hypersensitive response. This response is associated with restricted pathogen growth and represents a form of programmed cell death (PCD). Recent pharmacological and molecular studies have provided functional evidence for the conservation of some of the basic regulatory mechanisms underlying the response to pathogens and the activation of PCD in animal and plant systems. In animals, the mitochondrion integrates diverse cellular stress signals and initiates the death execution pathway, and studies indicate a similar involvement for mitochondria in regulating PCD in plants. But many of the cell-death regulators that have been characterized in humans, worms and flies are absent from the Arabidopsis genome, indicating that plants probably use other regulators to control this process.

Animals↗
PubMed2000

Co-expression of calcium-dependent protein kinase with the inward rectified guard cell K+ channel KAT1 alters current parameters in Xenopus laevis oocytes.

Increased guard cell cytosolic [Ca2+] is known to be involved in signal transduction pathways leading to stomatal closure, and inhibit the inward rectifying guard cell K+ channel KAT1. Guard cell calcium-dependent protein kinase (CDPK) has been shown to phosphorylate KAT1; such phosphorylation is known to modulate other K+ channels involved in signal transduction cascades. The work reported here focused on demonstrating CDPK-dependent inhibition of KAT1 currents. A cDNA encoding soybean CDPK was generated and it's translation product was shown to be functional; demonstrating Ca2+-dependent autophosphorylation and phosphorylation of a target protein. Ion currents were monitored using voltage clamp techniques upon expression of KAT1 in Xenopus laevis oocytes. Coexpression of recombinant CDPK with KAT1 in oocytes altered the kinetics and magnitude of induced K+ currents; at a given hyperpolarizing command voltage, the magnitude of KAT1 currents was reduced and the half-time for channel activation was increased. This finding supports a model of Ca2+-dependent ABA inhibition of inward K+ currents in guard cells as being mediated by CDPK phosphorylation of KAT1.

Animals↗
PubMed1998

The story of the internal carotid artery of mammals: from Galen to sudden infant death syndrome.

Some anatomical aspects of the blood supply of the brains of mammals have been examined to illuminate their functions. A fundamental explanation of sudden infant death syndrome (cot death) is suggested following experimental observations. Speculative contributions have been made to comparative physiological ideas concerning mammals of pronograde and erect habitus, their vascular pressure adaptations and temperature management. Neuro- and interventional radiologists may make some significant future applications of these ideas. Of immediate practical interest is the possibility of influencing the well-being of human embryos' neural tube development in utero by a comprehensive study of their temperature environment.

Adaptation, Physiological↗
PubMed1996

Exon 1 of the HD gene with an expanded CAG repeat is sufficient to cause a progressive neurological phenotype in transgenic mice.

Huntington's disease (HD) is one of an increasing number of neurodegenerative disorders caused by a CAG/polyglutamine repeat expansion. Mice have been generated that are transgenic for the 5' end of the human HD gene carrying (CAG)115-(CAG)150 repeat expansions. In three lines, the transgene is ubiquitously expressed at both mRNA and protein level. Transgenic mice exhibit a progressive neurological phenotype that exhibits many of the features of HD, including choreiform-like movements, involuntary stereotypic movements, tremor, and epileptic seizures, as well as nonmovement disorder components. This transgenic model will greatly assist in an eventual understanding of the molecular pathology of HD and may open the way to the testing of intervention strategies.

Animals↗
PubMed1996

The PR5K receptor protein kinase from Arabidopsis thaliana is structurally related to a family of plant defense proteins.

We have isolated an Arabidopsis thaliana gene that codes for a receptor related to antifungal pathogenesis-related (PR) proteins. The PR5K gene codes for a predicted 665-amino acid polypeptide that comprises an extracellular domain related to the PR5 proteins, a central transmembrane-spanning domain, and an intracellular protein-serine/threonine kinase. The extracellular domain of PR5K (PR5-like receptor kinase) is most highly related to acidic PR5 proteins that accumulate in the extracellular spaces of plants challenged with pathogenic microorganisms. The kinase domain of PR5K is related to a family of protein-serine/threonine kinases that are involved in the expression of self-incompatibility and disease resistance. PR5K transcripts accumulate at low levels in all tissues examined, although particularly high levels are present in roots and inflorescence stems. Treatments that induce authentic PR5 proteins had no effect on the level of PR5K transcripts, suggesting that the receptor forms part of a preexisting surveillance system. When the kinase domain of PR5K was expressed in Escherichia coli, the resulting polypeptide underwent autophosphorylation, consistent with its predicted enzyme activity. These results are consistent with PR5K encoding a functional receptor kinase. Moreover, the structural similarity between the extracellular domain of PR5K and the antimicrobial PR5- proteins suggests a possible interaction with common or related microbial targets.

Amino Acid Sequence↗
PubMed1991

Autonomic regulation of subsidiary atrial pacemakers during exercise.

Cardiac responses to graded treadmill exercise were compared in conscious dogs before and after excision of the sinoatrial node (SAN) and adjacent tissue along the sulcus terminalis. The chronotropic and dromotropic responses to dynamic exercise were compared with and without selective muscarinic (atropine) and/or beta-adrenergic (timolol) blockade. With the SAN intact, cardiac acceleration was prompt during onset of exercise and in proportion to work intensity. Immediately after SAN excision (1-7 days), pacemaker activity exhibited marked instability in rate and pacemaker location, with rapid shifts between atrial and junctional foci. Soon thereafter (1-2 wk), subsidiary atrial pacemakers (SAPs) assumed the primary pacemaker function. Although the SAP foci demonstrated stable heart rates and atrioventricular (AV) intervals at rest and during exercise, heart rates at rest and during steady-state exercise were reduced 34% from corresponding levels in the SAN-intact state, both with and without selective autonomic blockade. For control of dromotropic function, animals with SAP foci showed pronounced shortening in AV interval in conjunction with exercise that was further exacerbated by pretreatment with atropine. Eight weeks after excision of the primary SAN pacemakers, direct electrophysiological mapping localized the SAP foci to either the inferior right atrium along the sulcus terminalis or the dorsal cranial right atrium (in or near Bachmann's bundle). Animals with SAPs localized to the inferior right atrium had a more marked suppression in heart rate with a corresponding greater decrease in AV interval during exercise than dogs with SAP foci identified within the dorsal cranial right atrium.

Animals↗
PubMed1986

Stress and well-being in adolescence: the moderating role of physical exercise.

Adolescence is quite often a period of personal adjustment and stress, and previous research has found that adolescents are vulnerable to the negative effects of stressful life events. The present research sought to determine whether a subset of adolescent girls, those who routinely engage in physical exercise, escape stress-induced disturbances in physical and psychological well-being. Self-report measures of stressful life events, physical and emotional well-being, and exercise habits were obtained from 220 females of secondary school age. In accordance with experimental hypotheses, stress had a substantial debilitating effect on physical and emotional health among persons who reported exercising infrequently but not among those who reported exercising regularly. Potential mediating mechanisms are identified and implications of the findings for primary prevention programs targeted toward adolescents are discussed.

Adolescent↗