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Biomedical subjects

G M Roberts

Publications and source records attributed to G M Roberts.

At least 19 recordsLinked to original sources
PubMed1998

The reactivity of monoclonal antibodies against orf virus with other parapoxviruses and the identification of a 39 kDa immunodominant protein.

A panel of 27 mouse monoclonal antibodies (Mabs) was raised against orf virus. Sixteen of these Mabs reacted with a protein with a molecular mass of 65 kDa, 8 reacted with a protein with a molecular mass of 39 kDa and three remain uncharacterised. Reactivity of the Mabs with a library of recombinant vaccinia viruses expressing various regions of the NZ-2 orf virus genome identified the approximate positions of the genes encoding these 2 immunodominant orf virus proteins. The gene encoding the 39 kDa protein was identified and sequenced. The protein was detected in an envelope fraction of orf virus and was shown to be homologous to the envelope protein encoded by the H3L gene of vaccinia virus. The 65 kDa protein has not been fully chracterised, but the gene encoding it has been localised to a 10 kbp region of the orf virus genome. The Mabs were used to discriminate 4 parapoxviruses derived from sheep, 2 from cattle and 1 each from a seal and squirrel. Eighteen Mabs reacted with all 4 sheep viruses, 19 Mabs reacted with both cattle viruses, 6 recognised seal parapoxvirus and 2 recognised the squirrel parapoxvirus. Only one of the 27 Mabs reacted with all 8 parapoxviruses suggesting it recognises a conserved epitope within the genus.

Amino Acid Sequence↗
PubMed1997

The timing and magnitude of Ca2+ signaling by CD32 depends on its redistribution on the cell surface.

Ca2+ signaling was correlated with microaggregation and capping of CD32 molecules on the myeloid cell line, U937. The cytosolic free Ca2+ signal was related to the extent of CD32 cross-linking and arose asymmetrically within individual cells. Both the magnitude and the delay before Ca2+ signaling via CD32 on U937 cells was dependent on the extent of CD32 cross-linking. The delay time was extended in cells in which lateral diffusion in the membrane was reduced by covalently cross-linking of surface proteins. Under these conditions, capping but not surface microaggregation of CD32 molecules was prevented. The delay time before Ca2+ signaling but not the magnitude was also affected. At a higher density of covalent cross-linking of surface proteins, the magnitude of the Ca2+ signal by CD32 was also reduced and could be completely inhibited. This evidence therefore shows that the formation of a CD32 "cap" was not required for Ca2+ signaling by this route. However, the signaling delay time was a consequence of lateral diffusion of CD32 molecules in the membrane to form signaling-competent microaggregates, and the redistribution of CD32 molecules on the cell surface was required for Ca2+ signal generation.

Calcium↗
PubMed1997

Spatial and temporal separation of calcium signals in myeloid cells stimulated by immune complexes.

Stimulation of large (100 microns) human myeloid cells with immune complexes resulted in Ca2+ spiking. Both global and regional changes in the intracellular cytosolic free Ca2+ concentration were detected in response to immune complex stimulation. The regional changes were mediated by release of Ca2+ from stores, whereas global changes were mediated by Ca2+ influx. They occurred independently of each other, with release of Ca2+ from intracellular Ca2+ stores being separated from transmembrane influx of Ca2+. Bromophenacyl bromide, an 1-plastin binding agent, inhibited store release without preventing transmembrane influx of Ca2+. The large size of the myeloid cells used here allowed the visualisation of the spatial and temporal separation of store release from transmembrane influx of Ca2+, providing further evidence for the existence of independent Ca2+ store release and Ca2+ influx mechanisms in these cells.

Antigen-Antibody Complex↗
PubMed1996

Human cord blood-derived large myeloid cells: spontaneous shape change and chemotactic movement.

We have demonstrated two aspects of the movement of large myeloid cells derived from cord blood mononuclear cells after culture in RPMI 1640 and 10% fetal calf serum for eight days. At this time cells assume various shapes including round, oval, veiled, elongated and dendritic. Interestingly, these shapes were not static. Time-lapse recording demonstrated that individual cells change shape quite dramatically over four hours. Some of the veils showed a great deal of activity, some elongated cells shrank into rounded forms, and rounded cells stretched out into dendritic cells or elongated forms. We have previously shown that the number of N-formyl-methionine-leucyl-phenylalanine receptors on the cell surface increase with culture time up to eight days. Furthermore, a rise in Ca2+ was observed in response to 1 mumol/L N-formyl-methionine-leucyl- phenylalanine (chemotactic peptide) at the single cell level. In this paper we show the motility of cord blood-derived myeloid cells towards a chemotactic peptide concentration gradient leaking from a micropipette.

Bone Marrow Cells↗
PubMed1995

The production of large 'signalling competent' myeloid cells from circulating CD34+ cells in neonatal blood.

A method is described for the production of large myeloid cells, expressing functional formylated peptide receptors. CD34+ cells were isolated from neonatal cord blood by a two stage cell sorting method. Inclusion of SCF, together with IL-3, GM-CSF or both cytokines stimulated growth of these cells over 14 day period. The resultant cells, which ranged from 30 microns to 100 microns in size, were maintained in culture for up to 5 weeks, during which time the cell population increasingly displayed myeloid characteristics, including expression of formylated peptide receptors, phagocytosis and oxidase activation. These large cells had a functioning Ca2+ signalling system in response to the chemotactic peptide, f-Met-Leu-Phe. The large size of the cells enabled the rise in cytosolic free Ca2+ which resulted from either transmembrane influx of extracellular Ca2+ and release of Ca2+ from intracellular stores to be visualised. These large myeloid cells thus provide a model system for investigating the spatial characteristics of Ca2+ signalling by formylated peptide receptors on human myeloid cells.

Antigens, CD↗
PubMed1995

Slow Ca2+ waves in large myeloid cells as a result of a diffusible cytosolic factor.

In the work reported here evidence is provided that shows the slow wave of Ca2+ large neonatal myeloid cells provoked by formyl-Met-Leu-Phe was generated by spatially delayed Ca2+ influx. Evidence is provided that the delay in Ca2+ influx was the result of diffusion of a factor from the Ca2+ storage site, which is responsible for Ca2+ channel opening. The location of the Ca2+ release site was correlated with a region near the nucleus, probably a specialized region of endoplasmic reticulum. It is proposed that similar mechanisms of Ca2+ signaling occur in mature myeloid cells, such as neutrophils, but on a shorter time scale as a consequence of their smaller size.

Calcium↗
PubMed1995

Radiological assessment of constipation.

A scoring system for faecal loading was constructed by two experienced observers using the abdominal radiographs of 20 children. Four other observers independently graded the radiographs using this system and there was a high degree of agreement between all six observers (p < 0.001), suggesting that radiological assessment of constipation can be standardised.

Adolescent↗
PubMed1995

Incidence of Crohn's disease in Cardiff over 60 years: 1986-1990 an update.

OBJECTIVE: To report the incidence of Crohn's disease in the city of Cardiff between 1986 and 1990 and relate it to our previous incidence figures which extend over 60 years. METHODS: The incidence of Crohn's disease was examined using hospital diagnostic indices supplemented by records from clinicians and from the Department of Pathology, University Hospital of Wales, Cardiff, UK. In addition, a questionnaire was sent to all family practitioners in Cardiff asking them to identify patients in their practice. RESULTS: Eighty-six new patients were confirmed after reviewing the notes of patients in whom a diagnosis of Crohn's disease was considered. The mean incidence for this quinquennium was 5.9 cases per 10(5) of the population per year (95% confidence interval 4.7-7.3), with the highest age-specific incidence between those aged 15 and 34 years. Colorectal disease was the most common site of disease at the time of diagnosis and this was particularly striking in those aged over 50 years. CONCLUSIONS: The findings are related to our previous studies. The incidence of Crohn's disease has not continued to increase at the rate reported in early 1980s, but remains one of the highest reported in the literature. The colon has become the most commonly affected site, which may reflect an increase in diagnostic awareness.

Adolescent↗
PubMed1994

Slow calcium waves imaged in myeloid cells derived from neonatal cord blood.

Myeloid cells were derived from neonatal cord blood by culture with granulocyte-macrophage colony-stimulating factor for approximately 8 days. The resultant cell population contained large adherent cells (diameter > or = microns), expressing formylated peptide receptors that were functionally coupled to cytosolic free Ca2+ signaling. Imaging of the cytosolic free Ca2+ changes in these cells revealed initial focal release of Ca2+ from a site from within the cell, with elevated Ca2+ also near the cell edge. Increased cytosolic free Ca2+ moved as a slow oscillating wave across the cell (velocity 1 microns/s). As similar events may occur in mature neutrophils and monocytes but be difficult to resolve because of the small size of these cells, it was concluded that neonatal myeloid cells may provide a useful model system for the investigation of Ca2+ signaling in myeloid cells.

Blood Cells↗
PubMed1994

Corticosteroid prophylaxis for patients with increased risk of adverse reactions to intravascular contrast agents: a survey of current practice in the UK.

There is no definite experimental evidence that prophylactic corticosteroids reduce the frequency or severity of adverse effects from low-osmolar contrast agents in patients at increased risk of reaction. There is no consensus in terms of how prophylaxis should be conducted. We have studied current radiologists' practice in the UK by sending postal questionnaires to 212 radiologists randomly selected from a list of current consultants who are Fellows of the Royal College of Radiologists. One hundred and seventy (80.2%) of the 212 questionnaires were completed. The majority of radiologists routinely use non-ionic low osmolar contrast media for intravenous administration, only 30 (17.6%) routinely using conventional ionic agents and six (3.5%) ionic low osmolar agents. All 170 use low osmolar contrast media for those patients perceived to be at increased risk of adverse reactions. Seventy-six radiologists (44.7%) never use steroid cover. There is no consistent practice amongst the 94 consultants (55.3%) who do use steroid cover. The indications for prophylaxis vary, as do the corticosteroid used and the dose regime employed. The total dose used varied from the equivalent of 7.5 mg to 400 mg of prednisolone, and the duration of prophylaxis varied from a single dose to a 4 day course. One hundred and forty-two radiologists (83.5%) would welcome nationally agreed guidelines for the use of steroid cover. The great variation in the use of steroid cover in the UK reflects the lack of clear evidence of its benefit in combination with low osmolar contrast media.

Adrenal Cortex Hormones↗
PubMed1994

Compliance with guidelines for choice of radiographic projections: a multicentre study.

A study of compliance with guidelines for choice of radiographic projections was carried out in each of six centres. The study concerned 5851 examinations undertaken by 116 radiographers under the supervision of 29 consultant radiologists. The results showed good compliance between centres for examination of the chest (range 81-93%), abdomen (range 73-100%), thoracic spine (range 82-96%), pelvis/hip (range 78-99%) but not for examination of cervical spine (range 0-85%), paranasal sinus (range 0-100%) and lumbar spine (range 52-84%). The reasons given for these wide variations are discussed and estimates are given for the potential reductions in exposure to the UK population consequent upon national implementation of guidelines such as these.

Decision Making↗
PubMed1992

Incidence of ulcerative colitis in Cardiff over 20 years: 1968-87.

The annual incidence of ulcerative colitis in the city of Cardiff was examined over a 20 year period. In the decade 1968-77, the mean annual incidence was 6.4 per 10(5) of the population compared with 6.3 for the period 1978-87. There was no difference in the distribution or extent of the disease between decades or between sexes. This contrasts with the increased incidence of Crohn's disease during the same period. The study included a survey of family practitioners which identified a further 19 patients (11% of the total).

Adolescent↗
PubMed1990

How good are case notes in the audit of radiological investigations?

Audit based on the use of case notes completed in the ordinary course of patient care has not been widely used because of concern about the completeness and adequacy of such records. This paper describes the results of a study carried out to assess whether information contained in case notes was sufficiently reliable to enable clinical effectiveness to be measured. The study examines the extent to which a radiologist and an epidemiologist agree with two experienced clinicians in making retrospective judgements on whether out-of-hours radiological investigations are worthwhile. There was a high measure of agreement; only a relatively small amount of information in the case notes is needed to make valid judgements on clinical performance. The method described here may be applicable to other diagnostic investigations and the results of the study have wide implications for more effective and efficient management of resources within the NHS.

Clinical Competence↗
PubMed1989

IR vibrational CD in alanyl tripeptide: indication of a stable solution conformer.

Infrared vibrational CD (VCD) of a small peptide, L-alanyl-L-alanyl-L-alanine (Ala3), and a peptide model, N-acetyl-L-alanine-N'-methyl-amide (AAMA), in the 1550-1750-cm-1 region has been observed. The "coupled oscillator" VCD feature observed for Ala3 in the amide I region is interpreted in terms of a solution structure stabilized by the electrostatic interaction of the zwitterionic groups. No such interactions are possible in basic aqueous solution of Ala3 nor in AAMA in neutral solution. Thus, the coupled oscillator features are lost in the latter two cases, indicating the absence of a simple stabilized conformation.

Alanine↗