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Biomedical subjects

A Smith

Publications and source records attributed to A Smith.

At least 523 records · Page 29Linked to original sources
PubMed1997

Cytoplasmic domains of the common beta-chain of the GM-CSF/IL-3/IL-5 receptors that are required for inducing differentiation or clonal suppression in myeloid leukaemic cell lines.

Granulocyte-macrophage colony stimulating factor (GM-CSF) is a cytokine that controls the production and function of myeloid cells by interaction with a cell surface receptor composed of a specific ligand-binding alpha-chain (hGMRalpha) and a shared signal-transducing beta-chain (beta c). Co-expression of human GMR alpha-chain and wild-type human beta c in two murine leukaemic cell lines (M1 and WEHI-3B D+) conferred the ability to terminally differentiate into macrophages when stimulated with human GM-CSF. Analysis of cytoplasmic truncation mutants of beta c showed that residues to amino acid 783 (numbering from the first amino acid of the leader sequence) were sufficient for the GM-CSF-dependent induction of all aspects of differentiation in both cell types. However, shorter truncations selectively lost, in a cell-specific manner, first the capacity to induce macrophage migration in agar and then cell surface differentiation antigens and clonal suppression of proliferative potential. The data suggest that different aspects of the differentiated phenotype can be dissociated with the required signalling pathways originating from distinct regions of the receptor cytoplasmic domain and cooperating to produce a fully differentiated macrophage. The cooperativity of these pathways and limiting cell signalling intermediate pool sizes could explain the observed cell line differences and may have implications for normal haemopoiesis.

Animals↗
PubMed1997

Construction and characterization of a 10-genome equivalent yeast artificial chromosome library for the laboratory rat, Rattus norvegicus.

Increasing attention has been focused in recent years on the rat as a model organism for genetic studies, in particular for the investigation of complex traits, but progress has been limited by the lack of availability of large-insert genomic libraries. Here, we report the construction and characterization of an arrayed yeast artificial chromosome (YAC) library for the rat genome containing approximately 40,000 clones in the AB1380 host using the pCGS966 vector. An average size of 736 kb was estimated from 166 randomly chosen clones; thus the library provides 10-fold coverage of the genome, with a 99.99% probability of containing a unique sequence. Eight of 39 YACs analyzed by fluorescence in situ hybridization were found to be chimeric, indicating a proportion of about 20-30% of chimeric clones. The library was spotted on high-density filters to allow the identification of YAC clones by hybridization and was pooled using a 3-dimensional scheme for screening by PCR. Among 48 probes used to screen the library, an average of 9.3 positive clones were found, consistent with the calculated 10-fold genomic coverage of the library. This YAC library represents the first large-insert genomic library for the rat. It will be made available to the research community at large as an important new resource for complex genome analysis in this species.

Animals↗
PubMed1997

Childhood-onset schizophrenia. Progressive ventricular change during adolescence.

BACKGROUND: There is controversy about progression in brain abnormalities in later-onset schizophrenia. This study looked for more striking progression in brain abnormalities during adolescence in a chronically ill, treatment-refractory sample of patients with childhood-onset schizophrenia who had had more prepsychotic developmental disturbance, but clinical and neurobiological characteristics similar to those of patients with treatment-refractory adult-onset schizophrenia who have poor outcome. METHODS: Anatomic brain magnetic resonance images were obtained for 16 children and adolescents with onset of schizophrenia by 12 years of age and 24 temporally yoked, age- and sex-matched healthy controls. Subjects were scanned on initial admission and rescanned after 2 years with the identical equipment and measurement methods. RESULTS: Childhood schizophrenics showed a significantly greater increase in ventricular volume than did controls, for whom ventricles did not increase significantly (analysis of variance, diagnosis x time, F = 16.1, P < .001). A significant decrease in midsagittal thalamic area was also seen for the schizophrenics (P = .03), which was unchanged at rescan for controls. These differential brain changes correlated significantly with each other and tended to be predicted by both prepsychotic developmental abnormality (Premorbid Assessment Scale, P = .06) and Brief Psychiatric Rating Scale at follow-up (P = .07). CONCLUSIONS: More consistent progressive ventricular enlargement was seen during adolescence for this childhood-onset sample than has been reported for adult-onset populations. The brain imaging results support other clinical data showing both early and late deviations in brain development for at least this rare subgroup of treatment-refractory, very-early-onset schizophrenic patients.

Adolescent↗
PubMed1997

Effect of nebulizer type and antibiotic concentration on device performance.

We compared the performance of selected ultrasonic and jet nebulizers when aerosolizing several antibiotic formulations to determine optimum combinations for delivery of a respirable antibiotic aerosol. Three ultrasonic devices were tested: the UltraNeb 99/100, the UltraAIR and the Aerosonic. The reusable jet nebulizers were the Dura ProNeb, Pari-LL and the Sidestream. The six disposable jet nebulizers were Marquest Acorn II, Hudson T Updraft II, Baxter MistyNeb, Pari-LC, Pari IS-2, and a disposable Sidestream. Each jet was tested with four compressors: a DeVilbiss AP-50, a Pulmo-Aide, a DuraNeb and a PariMaster. All nebulizing systems were initially tested with normal saline. From the initial data, six jet nebulizers and one ultrasonic device were tested with varying concentrations of tobramycin, gentamicin, ceftazidime, ciprofloxacin and colistin. Output was assessed by measuring volume (milliliters per minute), and amount of drug (milligrams per minute) nebulized. We then measured mean particle size of the antibiotic aerosol with seven jet nebulizers and two different compressors, Pulmo-Aide and PariMaster, and two ultrasonic devices. The rate of nebulization of saline and antibiotic solutions (milliliters per minute) was greater with the ultrasonic device(s) than all jet nebulizer systems tested. Increasing the reservoir antibiotic concentration increased the drug output (milligrams per minute) with the jet nebulizers to a maximum, followed by decreasing output. When antibiotic concentrations were increased the output decreased more precipitously with the ultrasonic devices than with the jet nebulizers. At the highest antibiotic concentrations tested, the ultrasonic devices had the lowest output. Particle size distribution was most dependent on the specific jet device, with particle size distribution less affected by a specific antibiotic or its concentration. Higher reservoir concentrations can be utilized for increasing output of respirable antibiotic aerosols by jet nebulizers. We conclude that antibiotic output is dependent upon both the nebulizing system and the reservoir concentration of antibiotic.

Aminoglycosides↗
PubMed1997

The structural basis of the biological actions of the GM-CSF receptor.

The receptor for granulocyte/macrophage colony-stimulating factor (GM-CSF) consists of a ligand-specific low-affinity binding chain (GM-CSFR alpha) and a second chain that is required for high-affinity binding and signal transduction. This second chain is shared by the ligand-specific alpha-chains for the interleukin 3 (IL-3) and IL-5 receptors and is therefore called beta common (beta c). In mice but not humans the IL-3 receptor can also use a closely related but IL-3-specific beta-chain (beta IL-3). In order to define the contributions of each chain to receptor signalling we generated mice in which either beta c or beta IL-3 expression was deleted. beta IL-3 null mice were phenotypically normal but displayed a decreased responsiveness to IL-3 in vitro. beta c null mice, on the other hand, were unresponsive to GM-CSF or IL-5 but still responded to IL-3. These data demonstrated that GM-CSF and IL-5 receptors can use only one beta-chain for signalling (beta c) while IL-3 can effectively use either beta-chain. The hierarchical basis of receptor transmodulation was shown to result from this differential usage of beta-chains. To define the regions required for different types of cell signalling, we constructed human beta c mutants with successive cytoplasmic truncation. By the use of appropriate biological read-out systems we found that the cytoplasmic region of the receptor has a modular design with distinct domains required for cell proliferation, cell survival, differentiation and growth suppression. Appropriate targeting of these domains and the signalling pathways they initiate may provide highly specific cell therapies in the future.

Animals↗
PubMed1997

Preclinical evaluation of copper-67 labelled anti-MUC1 mucin antibody C595 for therapeutic use in bladder cancer.

Transitional cell carcinoma of the bladder is the fifth commonest cause of death from cancer in men in the United Kingdom. Most patients present early with superficial disease, though with current treatment up to 20% progress to invasive disease, which has a poor prognosis. Better local treatments are required to limit this tumour progression. The ease of access to the bladder via a catheter provides the ideal opportunity for antibody (Ab) targeted therapy. We have previously shown that indium-111 labelled anti-MUC1 mucin Ab C595 selectively localises to bladder tumours after intravesical administration. We have selected copper-67 as an alternative radiolabel with suitable physical characteristics for radioimmunotherapy. This communication demonstrates that C595 can be reproducibly labelled with 67Cu and that the radioimmunoconjugate is both stable and maintains high immunoreactivity. Pilot studies on cystectomy specimens in a novel ex vivo system and in one patient confirmed the ability of this conjugate to localise to tumour after intravesical administration. On the basis of these studies we are now in a position to study the intravesical administration of 67Cu-labelled C595 in patients with bladder cancer with a view to a therapeutic trial.

Administration, Intravesical↗
PubMed1997

A suicide vector for allelic recombination involving the gene for glutamate 1-semialdehyde aminotransferase in the cyanobacterium Synechococcus PCC 7942.

Gabaculine (2,3-dihydro 3-amino benzoic acid) is a potent inhibitor of tetrapyrrole biosynthesis in organisms that use the C5 pathway for the synthesis of delta-aminolaevulinic acid. Glutamate semialdehyde aminotransferase (GSA-AT), the enzyme catalysing the formation of this key precursor of tetrapyrroles, is normally inhibited by concentrations of gabaculine in the order of 5 microM. However, in Synechococcus 6301 strain GR6, a cyanobacterium that is resistant to 100 microM gabaculine, this enzyme has undergone two changes in structure: a deletion of three amino acids from positions 5 to 7 and the substitution of isoleucine for methionine at position 248. To establish the effect in vivo of these specific changes in the gene for GSA-AT (hemL), a suicide vector (pHS7) containing an antibiotic cassette was constructed to achieve the replacement, by homologous recombination, of the wild-type hemL gene in the chromosome by a modified form of the gene. Recombinant strains of Synechococcus 7942 obtained using pHS7-hemLGR6 were indistinguishable from Synechococcus 6301 GR6 in terms of the resistance of growth and of chlorophyll accumulation to high concentrations of gabaculine, while a wild-type recombinant produced using pHS7-hemLWT had retained its sensitivity. Southern hybridisation using gene probes for hemL, ampr and cmr confirmed that chromosomal integration of the plasmids had occurred in both WT and GR6 recombinants. Growth and chlorophyll accumulation in equivalent strains with the hemL gene containing either the deletion or the transition characteristic of Synechococcus 6301 GR6 were inhibited by 10 microM gabaculine. Consequently, resistance in vivo to high concentrations of this compound is dependent on both the changes in gene/enzyme structure. This investigation has established the effectiveness of the suicide vector pHS7 for studying the effect in vivo of specific changes in the hemL gene. It has also demonstrated that replacement of the wild-type gene by that from Synechococcus 6301 GR6 is sufficient to confer resistance in vivo to high concentrations of gabaculine.

Alleles↗
PubMed1997

Roles of Eph receptors and ephrins in neural crest pathfinding.

Neural crest cells migrate along specific pathways to their destinations and, like neuronal growth cones, must be guided by extracellular cues. One example of neural crest pathfinding is the segmental migration of branchial and trunk neural crest; this is associated with the patterning of the skeletal components of the branchial arches and of the peripheral nervous system. In this review, we discuss recent work that has implicated Eph receptors and their ephrin ligands in mediating repulsive interactions that restrict neural crest cell migration. We relate these findings to the roles of these receptors and ligands in growth cone guidance and the segmental restriction of cell movement in the hindbrain.

Animals↗
PubMed1997

Differences in bimanual coordination associated with stuttering.

The motor coordination of adults who stutter was examined in the performance of a bimanual movement task. Fifteen subjects who stutter and 15 matched subjects who do not stutter performed three trials of a bimanual finger movement task. Subjects were required to produce a flexion and extension movement of the metacarpophalangeal joint of each index finger in rhythm to a metronome. The rate of movement increased during the 70 s trial. Stutterers could maintain movements at the prescribed rate as well as nonstutterers; however, stutterers moved with less amplitude and peak velocity. In addition, dynamical analysis revealed that subjects who stutter exhibited greater relative phase variability than subjects who do not stutter. These results shed new light on the mixed results of earlier studies on nonspeech motor performance of individuals who stutter and suggest that there are strategic differences as well as coordination differences that should be observable across a variety on motor tasks requiring coordination of multiple effectors.

Adult↗
PubMed1997

The bigger the burn, the greater the stress.

Data characterizing the endocrine stress response to burn injury in children are sparse. We have measured the levels of the stress hormones arginine vasopressin, catecholamines-adrenaline, noradrenaline and dopamine-atrial natriuretic peptide and hormones of the renin-angiotensin-aldosterone system in admission blood samples taken from 35 children admitted to the burns unit of the regional children's hospital. Hormone levels were compared with the size of burn injury. With the exception of adrenaline, there were significant positive correlations between vasopressin (r = 0.707, p < 0.0001), plasma renin activity (r = 0.721, P < 0.0001), angiotensin II (r = 0.512, P = 0.002), aldosterone (r = 0.620, P < 0.0001), noradrenaline (r = 0.430, P = 0.0189), dopamine (r = 0.627, P = 0.0024) and percentage burn surface area, and a negative correlation between atrial natriuretic peptide (r = 0.548, P = 0.0008) and burn surface area. It is concluded that the hormones which react to stress are very sensitive to burn injury in children, and that the magnitude of their response is closely related to the size of the burn surface area.

Arginine Vasopressin↗
PubMed1997

Lack of effect of nitric oxide inhibition on bronchial tone and methacholine-induced bronchoconstriction in man.

The role of nitric oxide (NO) as a bronchodilator has been studied in humans with controversial results. The aim of the present study was to investigate the role of endogenous NO on bronchial tone by studying whether nitric oxide synthase (NOS) inhibition with NGnitro-L-arginine-methyl-ester (L-NAME) influences basal bronchial tone, or potentiates methacholine-induced bronchoconstriction. In a preliminary experiment in five subjects, a significant reduction in exhaled NO was found after delivering L-NAME (15 mg in saline) (from 3.9 +/- 1.2 to 2.4 +/- 1.1 nmol min-1, P < 0.05). In nine healthy non-smokers, specific airway conductance (SGAW), as a measure of airway calibre, was recorded after delivering, in a double-blind, controlled vs. placebo fashion, both nebulized L-NAME and saline, at baseline and after methacholine-induced bronchoconstriction. There was no significant difference between the baseline SGAW values before and after delivering L-NAME (0.264 +/- 0.04 and 0.267 +/- 0.05 cm H2O-1 s-1, respectively). After pre-treatment with L-NAME, SGAW values during methacholine-induced bronchoconstriction were not different in comparison to values obtained after saline inhalation. It is concluded that decreased endogenous NO does not influence bronchial tone in healthy people, nor does it modify methacholine-induced bronchoconstriction.

Adult↗
PubMed1997

An investigation into the melting behavior of binary mixes and solid dispersions of paracetamol and PEG 4000.

The melting behavior of paracetamol and polyethylene glycol (PEG) 4000, both individually and as binary systems, has been studied using differential scanning calorimetry. The appearance of the PEG peaks was shown to be highly dependent on scanning rate, with evidence for the existence of once-folded and extended chain forms being noted at slower scanning speeds. The melting peak of paracetamol was found to be profoundly influenced by the presence of the PEG 4000; when observed at all, the endotherm became broader and occurred at a lower temperature on mixing with the polymer. The thermal behavior of the binary mixes was again highly dependent on scanning rate, with faster rates leading to the appearance of the paracetamol peak at lower concentrations. The mixes were then thermally cycled to mimic production of solid dispersions, showing that the temperature cycling of the PEG 4000 could result in binary melting with the paracetamol peak disappearing. The interpretation of these results in terms of the characterization of PEG solid dispersions is discussed.

Acetaminophen↗
PubMed1997

Variables related to differences in standardized test outcomes for children with autism.

The purpose of this experiment was to assess whether manipulation of variables related to motivation and attention in children with autism would influence performance on standardized tests. Two different testing conditions were compared: One consisted of the usual standardized testing procedures; during the other, specific variables that were hypothesized to relate to each child's responsiveness to task stimuli were manipulated. Data were collected in the context of a repeated reversals experimental design with condition order varied within and across children. Six children participated in a total of 44 separate testing sessions, controlled for order of conditions, number of sessions, and type of test. Results showed consistent differences between the two conditions, suggesting that improving motivation and attention in children with autism may considerably influence test performance and interpretation. Findings are discussed in relation to the difficulty in administering and interpreting changes in performance on standardized tests with this population.

Attention↗
PubMed1997

Pro-haemorrhagic effects of calcium antagonists: a comparison of isradipine and atenolol on ex vivo platelet function in hypertensive subjects.

It has been suggested that long term treatment with calcium antagonist drugs might inhibit platelet function and lead to an anti-atheromatous effect. However recent data have also suggested that such an effect might increase mortality due to an increased incidence of gastrointestinal bleeding. We identified 43 subjects from general practice with uncomplicated mild to moderate hypertension to compare the effects of the calcium antagonist isradipine with that of the beta-blocker atenolol on platelet function, plasma beta-thromboglobulin levels, fibrinolysis, and serum lipids in a randomised double-blind parallel group study. After careful evaluation to exclude concomitant aspirin use, only 24 subjects were eligible to enter the study. While isradipine and atenolol produced comparable and clinically significant falls in blood pressure (167 +/- 2/102 +/- 1 to 153 +/- 3/91 +/- 2 mm Hg, and 165 +/- 2/101 +/- 1 to 156 +/- 4/91 +/- 2 mm Hg, respectively), neither drug produced a detectable effect on ex vivo platelet aggregation, platelet retention, or thromboxane generation with adrenaline, collagen, adenosine-di-phosphate, or platelet activating factor. However a decrease in plasma beta-thromboglobulin levels was observed which reached statistical significance (P < 0.05) after 12 weeks treatment in the isradipine but not the atenolol group. A 39% reduction with isradipine compared with 34% following atenolol treatment. Euglobulin clot lysis time was not altered by either drug. Serum cholesterol concentrations were also unaltered by drug treatment. Therapeutic doses of the calcium antagonist isradipine may produce a minor indirect effect on platelet function after several weeks of treatment. However, this is of doubtful clinical importance and may simply reflect an effect of lowered blood pressure on platelet function.

Adrenergic beta-Antagonists↗
PubMed1997

Pulmonary hypertension, family and environment.

The focus of interest on pulmonary hypertension (PH) has come through recent therapeutic advances which prolong and improve quality of life. From this interest, recent observations form family studies indicate that a gene located on chromosome 2 is associated with PH. Environmental factors, the use of an anorectic agent, dexfenfluramine, has been associated with a risk of developing primary PH. A link with hypoxic induced PH has emerged in that a strain of rat, the fawn-hooded rat (FHR) which has a susceptibility to developing PH with mild hypoxia has an inherited storage defect to serotonin. Dexfenfluramine, by inhibiting the serotonin transporter, produces a similar pattern of disturbance of biogenic amine metabolism. This observation provides some insight into potential mechanisms for this complex disorder.

Animals↗