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Biomedical subjects

A Roberts

Publications and source records attributed to A Roberts.

At least 37 records · Page 2Linked to original sources
PubMed2002

Nephrotoxicity in survivors of Wilms' tumours in the North of England.

One aspect of concern for survivors of Wilms' tumour has been the late outcome in terms of renal function. Previous studies have documented low glomerular filtration rate and high blood pressure in some patients. Furthermore, disorders in tubular function (especially urinary concentration defects) have been suggested but not confirmed in small studies. The aim of this study was to determine the prevalence and nature of subclinical and overt glomerular, proximal and distal renal tubular toxicity in a population based cohort of survivors of Wilms' tumour. Forty patients (24 female) with a median age of 4.3 years (3 months-11.8 years) at diagnosis were studied. Median follow-up was 8.8 (range 0.06-27.5) years. Glomerular filtration rate was measured by (51)Cr-EDTA plasma clearance, proximal tubular function by electrolyte fractional excretions, urine excretion of low molecular weight proteins (retinol-binding protein) and renal tubular enzymes (alanine aminopeptidase; N-acetylglucosaminidase) and distal tubular function by the osmolality of the first two urines of the day on 3 consecutive days. Renal size (ultrasound) and blood pressure were also measured. Mean (range) glomerular filtration rate was 100 (61-150) ml min(-1) 1.73 m(-2). Nine were below the reference range for healthy individuals with two kidneys. Most serum electrolyte concentrations (sodium, potassium, chloride, calcium, magnesium and phosphate) fell within the normal range for age, as did the fractional excretions. The values that fell outside the normal range were only marginally abnormal. Subclinical measures of tubular toxicity (retinal-binding protein, alanine aminopeptidase, N-acetylglucosaminidase) were abnormal in only four patients. Thirty-seven patients achieved maximal urine osmolalities > or =800 mOsm kg(-1), but three failed to achieve this value even after DDAVP administration. Two patients had evidence of increased urinary albumin excretion. Compensatory renal hypertrophy was seen in all but two patients, but blood pressure was within normal limits in all patients. Current and past treatment for Wilms' tumour does not have any clinically important nephrotoxic effect in the majority of patients. This finding will enable paediatric oncologists to reassure patients and parents that treatment for Wilms' tumour rarely causes long-term renal impairment.

Age Factors↗
PubMed2002

A critical review of vascular endothelial growth factor (VEGF) analysis in peripheral blood: is the current literature meaningful?

Vascular endothelial growth factor (VEGF) is a potent angiogenic growth factor with a key role in many physiological and pathological processes. Investigation into the implications of circulating levels of this cytokine is progressing at an exponential rate. However, there are important inconsistencies between reports ranging from method of sample collection, processing, software manipulation and data interpretation and controversy as to whether plasma, serum or whole blood will provide the best prognostic information. Different techniques of centrifugation and temperature on sample handling and the impact of in vitro collection of blood on subsequent VEGF results have not been fully appreciated. We provide a critical review of the literature, report the results of our further investigations, suggest a uniform protocol for handling blood samples and highlight previously unsuspected problems in data interpretation.

Blood Specimen Collection↗
PubMed2002

Stress and the periodontal diseases: effects of catecholamines on the growth of periodontal bacteria in vitro.

Microorganisms possess the ability to recognize hormones within the host and utilize them to adapt to their surroundings. Noradrenaline and adrenaline, which are released during human stress responses, may act as environmental cues to alter the growth of individual organisms within subgingival biofilms. The aims of this study were to modify, for anaerobic culture, existing methodology used in determining microorganism catecholamine responses and to investigate the growth responses to noradrenaline and adrenaline of 43 microorganisms found within subgingival microbial complexes. We established initial inocula for each strain using anaerobic culture, re-inoculated into a minimal serum-based medium and grown anaerobically at 35 degrees C. We assessed organism growth by optical density (OD(600nm)) readings, with test and control cultures performed in triplicate. Test cultures were supplemented with 50 microm noradrenaline or 100 microm adrenaline. We observed significant growth effects for supplementation with noradrenaline (20 species responding positively) and adrenaline (27 species responding positively), with differences in growth response observed within bacterial species and within and between microbial complexes. The most pronounced positive growth effects of noradrenaline were demonstrated in Actinomyces naeslundii (+ 49.4%), Actinomyces gerenscseriae (+ 57.2%), Eikenella corrodens (+ 143.3%) and Campylobacter gracilis (+ 79.9%). We also observed inhibitory effects of noradrenaline supplementation for Porphyromonas gingivalis (- 11.9%) and Bacteroides forsythus (- 22.2%). Responses to adrenaline tended to mirror the responses seen with noradrenaline. Individual organisms from different microbial complexes vary in their in vitro growth responses to noradrenaline and adrenaline. Such variation may influence the in vivo composition of the subgingival biofilm in response to stress-induced changes in local catecholamine levels and play a significant role in the aetiology and pathogenesis of the periodontal diseases.

Actinomyces↗
PubMed2002

Grass pollen sublingual immunotherapy for seasonal rhinoconjunctivitis: a randomized controlled trial.

BACKGROUND: Previous studies suggest that sublingual immunotherapy (SLIT) represents a safer alternative to injection immunotherapy but equivalent efficacy is yet to be confirmed. OBJECTIVE: To evaluate the efficacy and safety of SLIT in grass pollen-induced seasonal rhinoconjunctivitis. METHODS: A randomized, placebo-controlled trial in 56 adults over 18 months. Outcome measures included diary scores of seasonal symptoms and medication use, overall assessments, conjunctival and intradermal provocation tests and serum antibody measurements. To investigate possible mechanisms, sublingual biopsies were taken for measurement of local T cells, antigen-presenting cells and IL-12 mRNA expression. RESULTS: There were no significant differences between the immunotherapy (IT) and placebo groups for diary symptom scores (P = 0.48) or rescue medication (P = 0.19). The patients' overall assessment of hayfever severity compared with previous years showed a highly significant improvement in favour of the IT group (P < 0.02). After treatment the late skin response was smaller (P = 0.003) and the ratio of serum allergen-specific IgG4/IgE was higher (P = 0.05) in the IT group. Both of these variables correlated with the clinical response to SLIT. There were no differences between groups in either the sublingual epithelium or lamina propria for numbers of CD3+ cells (epithelium: P = 0.9, lamina propria: P = 0.2), CD1a+ cells (P = 0.3, P = 0.25), CD68+ cells (P = 0.9, P = 1.0) or IL-12 mRNA+ cells (P = 0.6, P = 0.4). Local side-effects were minor and there were no serious treatment-related adverse events. CONCLUSION: Grass pollen sublingual immunotherapy was well tolerated. Although there was no significant change in diary scores, the improvement in overall assessments, which correlated with inhibition of the late skin response and increases in serum IgG4 : IgE ratio, indicates the need for larger, dose-ranging studies.

Administration, Sublingual↗
PubMed2002

Precision measurement of the electromagnetic fields in the focal region of a high-numerical-aperture lens using a tapered fiber probe.

We present a measurement of the intensity around the focus of a N.A.-0.95 lens using a tapered optical fiber probe. An asymmetry introduced by the vector nature of the incident polarized light is evident, although it is inconsistent with that predicted theoretically by considering the magnitude squared of the electric field. The sensitivity of the probe to different components of the electromagnetic field is considered, and it is shown that the measurement is consistent with vector diffraction theory when the probe properties are taken into account.

Journal Article↗
PubMed2001

Defining classes of spinal interneuron and their axonal projections in hatchling Xenopus laevis tadpoles.

Neurobiotin was injected into individual spinal interneurons in the Xenopus tadpole to discern their anatomical features and complete axonal projection patterns. Four classes of interneuron are described, with names defining their primary axon projection: Dorsolateral ascending and commissural interneurons are predominantly multipolar cells with somata and dendrites exclusively in the dorsal half of the spinal cord. Ascending interneurons have unipolar somata located in the dorsal half, but their main dendrites are located in the ventral half of the spinal cord. Descending interneurons show bigger variance in their anatomy, but the majority are unipolar, and they all have a descending primary axon. Dorsolateral commissural interneurons are clearly defined using established criteria, but the others are not, so cluster analysis was used. Clear discriminations can be made, and criteria are established to characterize the three classes of interneuron with ipsilateral axonal projections. With identifying criteria established, the distribution and axonal projection patterns of the four classes of interneuron are described. By using data from gamma-aminobutyric acid immunocytochemistry, the distribution of the population of ascending interneurons is defined. Together with the results from the axonal projection data, this allows the ascending interneuron axon distribution along the spinal cord to be estimated. By making simple assumptions and using existing information about the soma distributions of the other interneurons, estimates of their axon distributions are made. The possible functional roles of the four interneuron classes are discussed.

Afferent Pathways↗
PubMed2001

Receptor crosstalk protein, calcyon, regulates affinity state of dopamine D1 receptors.

The recently cloned protein, calcyon, potentiates crosstalk between G(s)-coupled dopamine D1 receptors and heterologous G(q/11)-coupled receptors allowing dopamine D1 receptors to stimulate intracellular Ca(2+) release, in addition to cAMP production. This crosstalk also requires the participating G(q/11)-coupled receptors to be primed by their agonists. We examined the ability of calcyon and priming to regulate the affinity of dopamine D1 receptors for its ligands. Receptor binding assays were performed on HEK293 cell membrane preparations expressing dopamine D1 receptors either alone or in combination with calcyon. Co-expression of dopamine D1 receptor and calcyon affected neither the affinity of this receptor for antagonists nor the affinity of agonist binding to this receptor high and low-affinity states. However, the presence of calcyon dramatically decreased the proportion of the high-affinity dopamine D1 receptor agonist binding sites. This decrease was reversed by carbachol, which primes the receptor crosstalk by stimulating endogenous G(q/11)-coupled muscarinic receptors. Our findings suggest that calcyon regulates the ability of dopamine D1 receptors to achieve the high-affinity state for agonists, in a manner that depends on priming of receptor crosstalk.

Apomorphine↗
PubMed2001

Outcome of infants receiving in-utero transfusions for haemolytic disease.

AIMS: To review the outcome of infants who received in-utero transfusion (IUT) at National Women's Hospital (NWH). Specifically to determine postnatal exchange and top-up transfusion requirements, to examine perinatal factors useful for predicting this and review neurodevelopmental status of recipients. METHODS: A review was undertaken of infants delivered at NWH between 1991 and 2000, who had received one or more IUT for haemolytc disease. The mean gestational age at birth was 34 weeks and birth weight 2298 g. The median number of IUT was four (range 1-9). The mean gestational age at the first IUT was 25 weeks and at last IUT was 31 weeks. RESULTS: All 37 infants survived to discharge. Postnatal exchange transfusion was required in ten and top up transfusion in 27 infants. Late transfusion (>3 weeks) was required in 21 infants. Follow-up information on 36 infants revealed one born prematurely following death of a co-twin had cerebral palsy and developmental delay. No other infant had audiology or neurodevelopmental abnormality. CONCLUSIONS: This review helps to confirm the good outcome following IUT although some infants continue to require transfusions for up to four months after birth.

Birth Weight↗
PubMed2001

An effective AIDS vaccine based on live attenuated vesicular stomatitis virus recombinants.

We developed an AIDS vaccine based on attenuated VSV vectors expressing env and gag genes and tested it in rhesus monkeys. Boosting was accomplished using vectors with glycoproteins from different VSV serotypes. Animals were challenged with a pathogenic AIDS virus (SHIV89.6P). Control monkeys showed a severe loss of CD4+ T cells and high viral loads, and 7/8 progressed to AIDS with an average time of 148 days. All seven vaccinees were initially infected with SHIV89.6P but have remained healthy for up to 14 months after challenge with low or undetectable viral loads. Protection from AIDS was highly significant (p = 0.001). VSV vectors are promising candidates for human AIDS vaccine trials because they propagate to high titers and can be delivered without injection.

AIDS Vaccines↗
PubMed2001

Mass spectrometry screening of combinatorial mixtures, correlation of measured and predicted electrospray ionization spectra.

Methodology was developed to afford rapid characterization of multicomponent mixtures of small organic molecules prepared by split-and-mix combinatorial synthesis. This methodology involved the use of liquid chromatography mass spectrometry (LC/MS) combined with correlation analysis of measured versus predicted electrospray ionization mass spectra. Low-resolution mass spectra of complex mixtures revealed predictable patterns that confirm library products, assisted in identifying chemical synthesis errors, and assessed overall library integrity. In general, equal signal intensities were observed for most combinatorial mixture components, indicating that differences in electrospray ionization efficiency was not a major limitation to this approach. High-throughput data processing programs and informatics tools were used to speed data analysis and to simplify the presentation of the library characterization results. This approach has been used to characterize combinatorial libraries that were synthesized for a variety of drug-discovery programs. Examples are shown for library formats of 1, 40, 66, 280, and 400 component(s)/well. The applicability of this approach to large combinatorial mixtures should allow direct characterization of massive combinatorial libraries.

Journal Article↗
PubMed2001

Ribosome display and affinity maturation: from antibodies to single V-domains and steps towards cancer therapeutics.

Protein affinity maturation using molecular evolution techniques to produce high-affinity binding proteins is an important step in the generation of reagents for cancer diagnosis and treatment. Currently, the most commonly used molecular evolution processes involve mutation of a single gene into complex gene repertoires followed by selection from a display library. Fd-bacteriophage are the most popular display vectors, but are limited in their capacity for library presentation, speed of processing and mutation frequency. Recently, the potential of ribosome display for directed molecular evolution was recognised and developed into a rapid and simple affinity selection strategy using ribosome complexes to display antibody fragments (scFv). Ribosome display and selection has the potential to generate and display large libraries more representative of the theoretical optima for naïve repertoires (10(14)). Even more important is the application of ribosome display for the affinity maturation of individual proteins by rapid mutation and selection cycles. These display strategies can apply to other members of the immunoglobulin superfamily; for example single V-domains which have an important application in providing specific targeting to either novel or refractory cancer markers. We discuss the application of ribosome display and selection in conjunction with variable domain (CTLA-4) libraries as the first step towards this objective and review affinity maturation strategies for in vitro ribosome display systems.

Amino Acid Sequence↗
PubMed2001

Multicenter evaluation of strategies for serodiagnosis of primary infection with Toxoplasma gondii.

The diagnostic performance of single-serum assays for toxoplasma-specific immunoglobulin (Ig)M. IgA. IgG, and IgE antibodies and of different combinations of such antibody assays in 20 European reference centers was assessed. A panel of 276 sera, of which 73 came from patients who seroconverted within 3 months (acute infection), 49 from patients who had seroconverted 3-12 months earlier (convalescence), and 154 from subjects who had two IgG-positive samples obtained 12 months apart (past infection), was tested with 20 toxoplasma-antibody assays and 195 combinations. In general, every assay with high diagnostic sensitivity showed low diagnostic specificity, i.e. no assay performed alone could reliably distinguish acute from past infection. Furthermore, no single assay (or combination) could separate convalescence from the other stages of toxoplasma infection. However, excellent diagnostic performances were reached by sequential use of highly sensitive IgM assays and methods examining IgG avidity or stage specificity. IgA or IgM assays were less suitable for confirmation of toxoplasma-IgM positivity. This study documents the strength of test combinations in assessing the stage of toxoplasma infection.

Acute Disease↗
PubMed2001

Optimization of cottontail rabbit papilloma virus challenge technique.

Disease induced by Cottontail Rabbit Papilloma Virus (CRPV) scarification in domestic rabbits shares many attributes with disease induced by human papilloma virus (HPV). CRPV induces squamous papillomas in domestic rabbits, of which approximately 70% transform into invasive carcinomas. In advanced tumors, virus is often undetectable, and occasionally, some rabbits undergo spontaneous regression of papillomas. Techniques utilized to scarify rabbit skin are diverse, often labor intensive and time consuming with the possibility for significant variability. Using four unique infection techniques, resultant papilloma incidence, time to onset, and total papilloma volumes were compared to determine an optimal challenge method. Five rabbits were each infected with CRPV via a tattoo gun with and without ink, an intradermal injection, manual use of a tattoo needle, or a sterile blade followed by manual use of a tattoo needle. Papilloma formation was monitored weekly after inoculation for 6 weeks. CRPV papillomas began as pinpoint foci at 3 weeks post challenge and grew exponentially throughout the course of measurement. Individual foci coalesced rapidly to form larger papilloma aggregates. Although intradermal injection was well tolerated and easily performed, it was the worst method of papilloma production (2.2 mm(3) at 6 weeks). The best method, a sterile blade followed by manual use of a tattoo needle, produced significantly larger papillomas over all time periods (>1100 mm(3) at 6 weeks, P<0.01). Inoculation of CRPV using this method produces highly repeatable papillomas beginning 3 weeks post-infection.

Animals↗
PubMed2001

Functional projection distances of spinal interneurons mediating reciprocal inhibition during swimming in Xenopus tadpoles.

The basis for longitudinal coordination among spinal neurons during locomotion is still poorly understood. We have now examined the functional projection distances for the longitudinal axons of reciprocal inhibitory 'commissural interneurons' in the spinal cord of young Xenopus tadpoles. In quiescent animals, glycinergic inhibitory postsynaptic potentials (IPSPs) were evoked in ventral spinal neurons by stimulating small rostral and caudal groups of commissural interneuron somata at different distances on the opposite side of the hindbrain and spinal cord. Unitary IPSPs, produced by single synaptic contacts, could be distinguished from background noise. Local cord stimulation at different distances revealed maximum functional projection distances up to approximately 0.5 mm for both descending and ascending axons, but with the probability of recording connections falling steeply over this distance. These maximum longitudinal projection distances are smaller than predicted by axonal anatomy (approximately 1.2 mm). We then measured functional projection distances during swimming by examining the synaptic output of a surgically isolated group of rostral commissural interneurons, mapping the occurrence of the mid-cycle, reciprocal IPSPs they produced in more caudal neurons. IPSPs occurred with high probability up to 0.9 mm away, nearly twice the projection distance found in quiescent tadpoles. These results show that synaptic contacts from commissural interneurons could influence longitudinal coupling during swimming at distances of up to 0.9 mm (approximately 4-5 myotome segments or approximately 25% of the spinal cord). They provide direct evidence for functional projection distances of a characterized class of interneurons belonging to a spinal locomotor pattern generator.

Animals↗