Biomedical subjects

R J Wilson

Publications and source records attributed to R J Wilson.

At least 19 recordsLinked to original sources

PubMed2006

KCNMB1 regulates surface expression of a voltage and Ca2+-activated K+ channel via endocytic trafficking signals.

Voltage-dependent and calcium-activated K(+) (MaxiK, BK) channels are ubiquitously expressed and have various physiological roles including regulation of neurotransmitter release and smooth muscle tone. Coexpression of the pore-forming alpha (hSlo) subunit of MaxiK channels with a regulatory beta1 subunit (KCNMB1) produces noninactivating currents that are distinguished by high voltage/Ca(2+) sensitivities and altered pharmacology [McManus OB, Helms LM, Pallanck L, Ganetzky B, Swanson R, Leonard RJ (1995) Functional role of the beta subunit of high conductance calcium-activated potassium channels. Neuron 14:645-650; Wallner M, Meera P, Ottolia M, Kaczorowski G, Latorre R, Garcia ML, Stefani E, Toro L (1995) Characterization of and modulation by a beta-subunit of a human maxi K(Ca) channel cloned from myometrium. Receptors Channels 3:185-199]. We now show that beta1 can regulate hSlo traffic as well, resulting in decreased hSlo surface expression. beta1 subunit expressed alone is able to reach the plasma membrane; in addition, it exhibits a distinct intracellular punctated pattern that colocalizes with an endosomal marker. Coexpressing beta1 subunit with hSlo, switches hSlo's rather diffuse intracellular expression to a punctate cytoplasmic localization that overlaps beta1 expression. Furthermore, coexpressed beta1 subunit reduces steady-state hSlo surface expression. Site-directed mutagenesis underscores a role of a putative endocytic signal at the beta1 C-terminus in the control of hSlo surface expression. We propose that aside from its well-established role as regulator of hSlo electrical activity, beta1 can regulate hSlo expression levels by means of an endocytic mechanism. This highlights a new beta1 subunit feature that regulates hSlo channels by a trafficking mechanism.

Cell Line↗

PubMed2005

Narrowing of the inferior dental canal in relation to the lower third molars.

OBJECTIVES: To assess narrowing of the inferior dental canal in the lower third molar regions using computed tomography (CT) and to determine the value of radiographic markers on rotational panoramic radiographs in assessing the true relationships of the inferior dental canal. METHODS: Patients referred for CT assessment of impacted lower third molars were used in this study. The lower third molars were assessed using CT to determine the position and morphology of the inferior dental canal relative to the roots and the cortical plates. The radiographic markers on rotational panoramic radiographs were correlated with the CT findings when rotational panoramic radiographs were available. RESULTS: The patients referred had 202 lower third molars. Inferior positioning of the inferior dental canal was the most common location on CT. Narrowing of the inferior dental canal was found in relation to the lower third molars in 66.8% of cases. The chance of narrowing of the inferior dental canal as shown using CT increased when at least one of the radiographic markers, superimposition, narrowing, deviation or reduction in density was present on the rotational panoramic radiograph. Deviation of the inferior dental canal on rotational panoramic radiographs was found to be the most significant predictor of narrowing of the inferior dental canal and a close relationship to the roots, as shown in CT. CONCLUSIONS: Narrowing of the inferior dental canal is a common finding when impacted lower third molars are assessed using CT. On rotational panoramic radiographs deviation of the inferior dental canal is the best predictor of narrowing of the inferior dental canal and a close relationship to the roots.

Adolescent↗

PubMed2002

A comparison of 13 guinea pig and human anti-tissue transglutaminase antibody ELISA kits.

AIMS: Tissue transglutaminase (tTG) is a major autoantigen recognised by IgA anti-endomysial antibodies (IgA EMA). Enzyme linked immunosorbent assays (ELISA) for IgA anti-tissue transglutaminase antibodies (IgA tTG) have therefore been developed as an alternative serological screening test to IgA EMA for coeliac disease (CD). The use of human tTG (h-tTG), as opposed to guinea pig liver tTG (gpl-tTG), in these assays has been reported to produce superior results. This study compared 13 commercial IgA tTG ELISA kits to ascertain their performance characteristics in the diagnosis of CD in patients with biopsy confirmed disease compared with controls. All patients and controls were adults aged 21 years or older. METHODS: Sera from the following groups of patients were tested in each kit: (1) 49 patients with CD confirmed on small bowel biopsies (all IgA EMA positive); (2) 34 patients with small bowel biopsies that were not consistent with CD; and (3) 30 patients with biopsy confirmed inflammatory bowel disease. All controls were negative for IgA EMA and were not IgA deficient. Sensitivities and specificities were determined using both the manufacturers' recommended cut off points and receiver operating characteristic (ROC) analysis derived decision thresholds. The area under the curve (AUC) for each ROC plot was also calculated and compared between kits. RESULTS: In general, the h-tTG based IgA tTG ELISA kits demonstrated superior performance (especially specificity) compared with the gpl-tTG based kits, although 100% sensitivity and specificity (comparable to the IgA EMA assay) was obtained in only one recombinant h-tTG based kit. CONCLUSIONS: The use of h-tTG in IgA tTG ELISA kits is generally, but not universally, associated with superior performance. Factors other than antigen source are important in determining kit performance.

Adult↗

PubMed2001

Ecological and evolutionary processes at expanding range margins.

Many animals are regarded as relatively sedentary and specialized in marginal parts of their geographical distributions. They are expected to be slow at colonizing new habitats. Despite this, the cool margins of many species' distributions have expanded rapidly in association with recent climate warming. We examined four insect species that have expanded their geographical ranges in Britain over the past 20 years. Here we report that two butterfly species have increased the variety of habitat types that they can colonize, and that two bush cricket species show increased fractions of longer-winged (dispersive) individuals in recently founded populations. Both ecological and evolutionary processes are probably responsible for these changes. Increased habitat breadth and dispersal tendencies have resulted in about 3- to 15-fold increases in expansion rates, allowing these insects to cross habitat disjunctions that would have represented major or complete barriers to dispersal before the expansions started. The emergence of dispersive phenotypes will increase the speed at which species invade new environments, and probably underlies the responses of many species to both past and future climate change.

Animals↗

PubMed2001

The in vivo conformation of the plastid DNA of Toxoplasma gondii: implications for replication.

The Phylum Apicomplexa comprises thousands of obligate intracellular parasites, some of which cause serious disease in man and other animals. Though not photosynthetic, some of them, including the malaria parasites (Plasmodium spp.) and the causative organism of Toxoplasmosis, Toxoplasma gondii, possess a remnant plastid partially determined by a highly derived residual genome encoded in 35 kb DNA. The genetic maps of the plastid genomes of these two organisms are extremely similar in nucleotide sequence, gene function and gene order. However, a study using pulsed field gel electrophoresis and electron microscopy has shown that in contrast to the malarial version, only a minority of the plastid DNA of Toxoplasma occurs as circular 35 kb molecules. The majority consists of a precise oligomeric series of linear tandem arrays of the genome, each oligomer terminating at the same site in the genetic map, i.e. in the centre of a large inverted repeat (IR) which encodes duplicated tRNA and rRNA genes. This overall topology strongly suggests that replication occurs by a rolling circle mechanism initiating at the centre of the IR, which is also the site at which the linear tails of the rolling circles are processed to yield the oligomers. A model is proposed which accounts for the quantitative structure of the molecular population. It is relevant that a somewhat similar structure has been reported for at least three land plant chloroplast genomes.

Animals↗

PubMed2001

Evolution of central respiratory chemoreception: a new twist on an old story.

Evolution of central respiratory chemosensitivity has been linked traditionally to the need for carbon dioxide regulation that accompanied the evolution of air breathing in terresterial animals. We examined the validity of this linkage by investigating the possibility of central chemoreception in air breathing fish that diverged from the amphibian lineage long before the appearance of terrestriality. We showed that the isolated brainstem preparation of the long nose gar (Lepisosteus osseus) produces a putative motor pattern for lung ventilation, which is responsive to CO(2). These findings, together with more inferential evidence, suggest an association between air breathing and central chemosensitivity in aquatic animals that spans the major branches in vertebrate phylogeny. Furthermore, developmental observations in tadpoles suggest that the neural substrates for central chemoreception exist in proximity to that for rhythm generation. We postulate that a primitive ancestral CPG, sensitive to CO(2) is conserved and is evidenced in the intrinsic coupling of respiratory CPG and central chemoreception in modern tetrapods.

Animals↗

PubMed2001

Which came first, the lung or the breath?

Lungs are the characteristic air-filled organs (AO) of the Polypteriformes, lungfish and tetrapods, whereas the swimbladder is ancestral in all other bony fish. Lungs are paired ventral derivatives of the pharynx posterior to the gills. Their respiratory blood supply is the sixth branchial artery and the venous outflow enters the heart separately from systemic and portal blood at the sinus venosus (Polypteriformes) or the atrium (lungfish), or is delivered to a separate left atrium (tetrapods). The swimbladder, on the other hand, is unpaired, and arises dorsally from the posterior pharynx. It is employed in breathing in Ginglymodi (gars), Halecomorphi (bowfin) and in basal teleosts. In most cases, its respiratory blood supply is homologous to that of the lung, but the vein drains to the cardinal veins. Separate intercardiac channels for oxygenated and deoxygenated blood are lacking. The question of the homology of lungs and swimbladders and of breathing mechanisms remains open. On the whole, air ventilatory mechanisms in the actinopterygian lineage are similar among different groups, including Polypteriformes, but are distinct from those of lungfish and tetrapods. However, there is extreme variation within this apparent dichotomy. Furthermore, the possible separate origin of air breathing in actinopterygian and 'sarcopterygian' lines is in conflict with the postulated much more ancient origin of vertebrate air-breathing organs. New studies on the isolated brainstem preparation of the gar (Lepisosteus osseus) show a pattern of efferent activity associated with a glottal opening that is remarkably similar to that seen in the in-vitro brainstem preparation of frogs and tadpoles. Given the complete lack of evidence for AO in chondrichthyans, and the isolated position of placoderms for which buoyancy organs of uncertain homology have been demonstrated, it is likely that homologous pharyngeal AO arose in the ancestors of early bony fish, and was pre-dated by behavioral mechanisms for surface (water) breathing. The primitive AO may have been the posterior gill pouches or even the modified gills themselves, served by the sixth branchial artery. Further development of the dorsal part may have led to the respiratory swimbladder, whereas the paired ventral parts evolved into lungs.

Animals↗

PubMed2001

Nifs and Sufs in malaria.

This review assembles data from three bodies of literature (bacterial genetics, plastid biogenesis and parasitology) that seldom have much direct cross-talk. After overcoming terminological complications to sort out microbial nifS from sufS genes, we connect a bacterial operon, recently found to be involved in iron metabolism, the formation of [Fe-S] clusters and oxidative stress to a potentially important gene (sufB) carried on the degenerate plastid genome of malaria and related parasites.

Amino Acid Sequence↗

PubMed2001

Cardiovascular optimization for high-risk surgery.

Controversy still exists concerning the strategy of targeting so-called supranormal levels of oxygen delivery as a means of improving outcome from high-risk surgery. The pathogenesis of postoperative morbidity is not fully defined; however, it seems likely that the gastrointestinal tract plays a pivotal role, particularly as a source of endotoxin, which is a potent stimulator of the inflammatory response. Delayed recovery of gastrointestinal function also is a major contributor to postoperative morbidity. Demonstration of a significant reduction in gut ischemia, endotoxemia, postoperative inflammatory response, and morbidity in a high-risk general surgical population as a result of perioperative hemodynamic optimization would be a highly worthwhile study.

Cardiotonic Agents↗

PubMed2001

Spontaneous contractions of myometrium from humans, non-human primate and rodents are sensitive to selective oxytocin receptor antagonism in vitro.

OBJECTIVES: To determine whether: 1. oxytocin receptor antagonists influence spontaneous contractions of myometrium from humans, non-human primates and rodents (in vitro), and 2. vasopressin V1a receptor antagonism is important for inhibition of spontaneous contractions in human myometrium. DESIGN: In vitro pharmacology of spontaneous contractions of myometrium from humans and animals. SETTING: The research laboratories of a university department of obstetrics and gynaecology and a pharmaceutical industry research centre. INTERVENTIONS: Samples of human myometrium were obtained at caesarean section. Tissue strips were suspended in organ baths for isometric force recording. Cumulative concentration effect curves to a selective oxytocin receptor antagonist (L-371,257) and a mixed oxytocin/vasopressin V1a receptor antagonist (atosiban) were obtained. The effect of L-371,257 was also determined in myometrium from non-pregnant rats and marmosets. MAIN OUTCOME MEASURES: The inhibition of spontaneous myometrial contractions in vitro. RESULTS: L-371,257 and atosiban significantly inhibited spontaneous activity of human myometrium in a concentration-related manner (P < 0.05), although the effect was more pronounced with L-371,257. Spontaneous contractions of myometrium from non-pregnant rats and marmosets were also inhibited by L-371,257 (atosiban was not tested). CONCLUSIONS: Spontaneous contractions of myometrium from humans, marmosets and rats are, at least in part, dependent on oxytocin receptor activity, in vitro. L-371,257 and atosiban may be inverse agonists. Selective non-peptide oxytocin receptor antagonists may be effective tocolytics.

Animals↗

PubMed2001

Brain stem PO(2) and pH of the working heart-brain stem preparation during vascular perfusion with aqueous medium.

The rat working heart-brain stem preparation (WHBP) is an in situ preparation having many of the advantages associated with in vitro preparations while retaining cardiovascular response functionality and an eupnoeic respiratory motor pattern. The preparation is perfused arterially with an aqueous medium having a much lower oxygen-carrying capacity than blood. To evaluate the efficacy of the artificial perfusion in providing adequate gas exchange within the brain stem, we used polarographic PO(2) and pH microelectrodes to determine the tissue PO(2) and pH of the medulla oblongata at various depths. When the perfusate was equilibrated with 5% CO(2) and 95% O(2), average tissue PO(2) was 294 Torr and no hypoxic areas were encountered. Tissue pH was remarkably uniform throughout the tissue, and on average was only 0.04 +/- 0.02 pH units more acidic than that of the perfusate. Increasing the PCO(2) of the perfusate increased tissue PO(2) and decreased arterial resistance. Decreasing perfusate PCO(2) (while keeping pH constant) decreased tissue PO(2) and reduced the respiratory activity. These results suggest that arterial PCO(2), independent of arterial pH, is an essential variable in determining both respiratory drive and cerebrovascular perfusion. We conclude that the medulla of the WHBP is oxygenated and within a physiological pH, which accounts for the eupneic pattern of respiratory motor activity it generates. Furthermore, this preparation may be a useful model for exploring mechanisms of central chemoreception as well as the dynamics of the cerebral vasculature responses following changes in blood gases.

Animals↗

PubMed2001

Goal attainment scaling with sexual offenders: a measure of clinical impact at posttreatment and at community follow-up.

The impact of cognitive-behavioral interventions was assessed for 28 low-moderate risk and 20 high-risk sexual offenders on conditional release to the Greater Toronto Area. Goal Attainment Scaling (GAS--T. Hogue, 1994) for sexual offenders was used to rate clinical and motivational elements of treatment taken from reports written at pretreatment, posttreatment, and after 3 months of community follow-up. Results indicated that both groups of offenders benefited from treatment, although low-moderate risk offenders showed consistently better results on all measures. Performance along nonrelapse prevention related dimensions increased from pretreatment to posttreatment and remained relatively steady in the community. Relapse prevention related treatment components showed a steady increase from pretreatment throughout follow-up in the community for low-moderate risk offenders, but not for high-risk offenders. Both groups improved substantially in level of motivation from pretreatment to posttreatment; however, only those in the low-moderate risk group maintained their motivation levels once released to the community. These results are discussed with respect to the effectiveness of cognitive-behavioral treatment of sexual offenders.

Cognitive Behavioral Therapy↗

PubMed2001

Oxygen sensitive chemoreceptors in the first gill arch of the tadpole, Rana catesbeiana.

Spike frequency was recorded in the nerve of the isolated superfused first gill arch of the bullfrog larva, Rana catesbeiana and the response to different superfusate PO2 was evaluated. In the metamorphic tadpole, spike frequency increased significantly when the superfusate PO2 was decreased (mean +/- SEM): 8.5 +/- 1.6 Hz at 650 Torr, 11.7 +/- 1.9 Hz at 140 Torr, 13.3 +/- 1.8 Hz at 65 Torr, 14.8 +/- 2.4 Hz at 0 Torr (ANOVA, p = 0.0002). The O2 sensitive chemoreceptor stimulants NaCN and almitrine also increased the spike frequency. This study demonstrates the presence of O2 sensitive chemoreceptors in the first gill arch of the tadpole.

Animals↗

PubMed2000

Developmental disinhibition: turning off inhibition turns on breathing in vertebrates.

Development requires age-dependent changes in essential behaviors. While the mechanisms determining the developmental expression of such behavior in vertebrates remain largely unknown, a few studies have identified permissive mechanisms in which the appearance of promoting signals activates pre-established networks. Here we report a different developmental process. Specifically, we show that the neuronal substrate that produces putative lung breathing in tadpoles is formed early in development, but remains more or less inactive until metamorphosis because of suppression mediated by a GABA(B) receptor-dependent mechanism. Blocking this suppression using 2-hydroxy-saclofen, a GABA(B) receptor antagonist, results in the precocious production of the putative lung breathing motor pattern. This blocker failed to augment putative lung breaths after metamorphosis. Thus, our results suggest that loss of an inhibitory signal during development (i.e., developmental disinhibition) is responsible for the developmental expression of air breathing.

Action Potentials↗

PubMed2000

Respiratory activity in neonatal rats.

In neonatal animals in vitro preparations have been employed widely to study the central control of respiration. These preparations have limitations in that reflex afferent inputs and kinesiological studies cannot be performed. Here, we describe an alternative in situ experimental model for studying both peripheral and central control of the respiratory system in neonatal rats. Using technology based on adult mammals, we introduce an intra-arterially perfused working heart-brainstem preparation (WHBP) that permits studies on eupnoeic respiration in neonatal rats from within a few hours of birth. Using this preparation we demonstrate a three-phase respiratory rhythm as revealed by the activity in phrenic and recurrent laryngeal motor nerves, the respiratory modulation of laryngeal resistance and the firing patterns of respiratory neurones recorded from the ventrolateral medulla. We conclude that the neonatal rat WHBP is an in situ preparation because it produces a respiratory rhythm similar to that of adult in vivo mammal preparations but distinct from in vitro preparations.

Animals↗

PubMed2000

Baclofen eliminates cluster lung breathing of the tadpole brainstem, in vitro.

Intermittent lung ventilation is a respiratory pattern wherein breaths occur in clusters. Intermittent lung ventilation is common in amphibians and can occur in mammals. Isolated brainstems from postmetamorphic tadpoles exhibiting episodic lung ventilatory bursts were superfused with baclofen, a potent gamma-aminobutyric acid (GABA)(B) receptor agonist. At moderate concentrations (0.125 to 0.5 microM), the number of lung bursts per episode decreased but their overall frequency was unchanged. At 0.5 microM, only 1.22+/-0.24 lung bursts occurred per episode, indicating virtually no clustering. Only at higher concentrations was overall breathing frequency decreased. Therefore, at moderate concentrations of baclofen continuous ventilation replaced episodic ventilation, suggesting that a GABA(B) receptor-dependent pathway may regulate the clustering of lung breaths.

Animals↗

PubMed2000

Chemical and thermal stimuli have short-lived effects on the retzius cell in the medicinal leech.

During the appetitive phase of feeding, hungry leeches detect a prey by the integration of signals perceived by different sensory systems. Earlier reports suggested that chemical or thermal sensory stimulation of the lip was associated with increased afferent activity in cephalic nerves connecting the lip to the central nervous system. These authors further suggested that this activity was relayed to Retzius cells in segmental ganglia, which then released serotonin to initiate and control all aspects of feeding behavior. In this study, we show that chemosensory or thermal activation of the lip lasting for at least 5 min produces a distinct signal in the cephalic nerves consisting of action potentials of low amplitude. These small amplitude signals are clearly distinguishable from the large action potentials evoked by mechanosensory stimuli applied to the same area of the lip. Both types of sensory stimuli also evoke an increase in the firing frequency of the Retzius cells in segmental ganglia. However, the response recorded in the nerves and the Retzius cells during a maintained stimulus is not constant but decreases with an exponential time course. These results agree with our earlier observations on a semi-intact feeding preparation in which we showed that the firing frequency of the Retzius cell decreased as soon as the leech began to ingest its meal. Therefore, our data provide further evidence suggesting that it is unlikely that heat or chemical cues maintain the Retzius cell in an active state throughout the consummatory phase of feeding.

Action Potentials↗

PubMed2000

Impact of a plastid-bearing endocytobiont on apicomplexan genomes.

Both the chromosomal and extrachromosomal components of the apicomplexan genome have been supplemented by genes from a plastid-bearing endocytobiont: probably an algal cell. The sequence of the apicomplexan plastid's vestigial genome indicates that a large number (>100) of genes of endocytobiotic origin must have transferred laterally to the host cell nucleus where they control maintenance of the plastid organelle and supply its functional components by means of post-translational protein trafficking. Should the nuclear genes prove to be less divergent phylogenetically than those left on the plastid genome, they might give better clues than we have at present to the origin of the plastid-bearing endocytobiont. Most of these nuclear genes still await discovery, but the on-going genome sequencing project will reveal the function of the organelle, as well as many "housekeeping" processes of interest on a wider front. The plastid's own protein synthetic machinery, being cyanobacterial in origin, offers conventional targets for antibiotic intervention, and this is discussed here using a structural model of elongation factor Tu. Uncovering the vital function(s) of the plastid organelle will provide new drug targets.

Amino Acid Sequence↗