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M Lloyd

Publications and source records attributed to M Lloyd.

At least 55 records · Page 3Linked to original sources
PubMed1994

Differential effects of mutations in substrate recognition site 1 of cytochrome P450 2C2 on lauric acid and progesterone hydroxylation.

Mutations at amino acid positions 107-120, which are part of a predicted substrate recognition site [Gotoh, O. (1992) J. Biol. Chem. 267, 83-90], were analyzed in C2MstC1, a chimera of P450 2C2 and P450 2C1. This hybrid protein has a new activity for progesterone C21-hydroxylation in addition to the lauric acid (omega-1)hydroxylase activity present in both parent proteins. Various substitutions for highly conserved glycines at positions 111 and 117 and tryptophan at position 120 strongly decreased the lauric acid hydroxylase activity of P450 2C2 and C2MstC1 and the progesterone hydroxylase activity of C2MstC1. Activities of mutant proteins with substitutions at 107, 108, and 112-115 were also strongly reduced. Modest or no decreases in activity were observed for substitutions at 109, 110, 116, 118, and 119. Lauric acid hydroxylase activity decreased more in most C2MstC1 mutants than in those of P450 2C2, particularly at positions 107 and 108. A substitution of phenylalanine for valine-112 reduced progesterone hydroxylation by 30-fold while only moderately reducing lauric acid hydroxylase by 40%. This differential effect on two dissimilar substrates demonstrates the importance of residue 112 for substrate interactions. The results are consistent with a model in which residues 107-110 align with the B'-helix of the bacterial proteins P450cam and P450BM-3. This helix is followed by a substrate-contacting loop from 111 to 116, and residues 117-120 align with the C-helices of the bacterial proteins In this alignment, Trp-120 is positioned behind the heme such that it could participate in electron transfer from reductase.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Dr Know.

Explore the source record for details and available documents.

Communication↗
PubMed1994

Allergic disorders in systemic vasculitis: a case-controlled study.

A number of the systemic vasculitides (SV) may have an allergic component although specific allergens remain unknown. We evaluated the prevalence of several types of allergy in 60 consecutive patients with SV and their families. Two control groups were studied. One included 60 healthy people and the other 60 unselected patients attending a general rheumatology clinic who did not have SV. Forty-four of the 60 patients (73%) had a history of at least one type of allergy. This was significantly higher than in either control group (P = 0.0001 and P = 0.0002). There was also a significantly higher prevalence of allergies among the families of the SV patients compared to the controls. This data supports the idea that an allergic response to an external allergen may play an important part in the aetiology of these diseases.

Adult↗
PubMed1994

Prescribing and referral in general practice: a study of patients' expectations and doctors' actions.

BACKGROUND: What decisions do patients expect the general practitioner to take within the consultation and to what extent are these expectations fulfilled? What factors influence patients' expectations and general practitioners' actions? AIM: This study aimed to examine these questions with reference to prescribing and hospital referral. METHOD: The study covered 1080 consultations with 12 general practitioners in two north London practices. Information was collected by self-administered questionnaires from patients before the consultation and from the general practitioners after the consultation. RESULTS: Fifty one per cent of patients expected and 55% received a prescription; 13% expected hospital referral and 10% were referred. Factors related to their presenting problem were most strongly associated with patients' expectation of receiving a prescription. The actions which the general practitioners took were most strongly associated with patients' expectations. Patients' anxiety about their health problem also appeared to influence their expectations of referral and the doctor's prescribing decision. CONCLUSION: This study suggests that patients' expectation of management and their anxiety associated with the presenting problem may be two of the factors which influence general practitioners' prescribing and referral behaviour and may explain some of the observed variations in behaviour.

Adolescent↗
PubMed1994

Controlled trials in the evaluation of counselling in general practice.

In this paper the difficulties of conducting a controlled evaluation of counselling (brief psychotherapy) in general practice are discussed. Results of a pilot study indicate that patients referred by family doctors to counsellors are often seriously emotionally distressed and recovery is slow. Counsellors come from different backgrounds and use a variety of therapies. Although the results show that controlled research is feasible, in a definitive trial patients should be randomized in a stratified manner, according to severity, by the researcher after initial assessments have been made. Counsellors should have a recognized accreditation and preferably be employed for the trial to ensure uniformity of approach and avoid long waiting lists. Blind assessments of outcome are desirable but are not always feasible and reliance on patient self-report is important. Within the limitations of current knowledge, only controlled evaluations will provide a greater understanding of the efficacy of counselling in general practice.

Adult↗
PubMed1993

Cassette mutagenesis of a potential substrate recognition region of cytochrome P450 2C2.

Cassette mutagenesis was used to analyze the effects of mutations at amino acid positions 107-120 in cytochrome P450 2C2 which are part of a predicted substrate recognition site, SRS-1 (Gotoh, O. (1992) J. Biol. Chem. 267, 83-90), and terminate with a highly conserved tryptophan. All the mutant enzymes were expressed in COS1 cells at approximately the same level as wild type as determined by immunoprecipitation of radiolabeled products. Substitutions of amino acids from 107 to 110 and from 116 to 119 resulted in mutant enzymes that retained substantial lauric acid hydroxylase activity suggesting that these residues are not critical determinants of substrate specificity. In contrast, amino acids 112-115 were characterized by strong decreases in activity in at least one mutation tested. A substitution of phenylalanine for valine 112 reduced activity about 3-fold. At position 113, substitution of leucine for isoleucine had little effect, but activity was reduced 15-fold by substitution with cysteine. A conservative mutation at position 114 reduced activity 5-fold, a nonconservative mutation at position 115 resulted in a 30-fold reduction of lauric acid hydroxylation. Substitution of glutamic acid for glycine at position 109 had little effect on activity, while more conservative substitutions of valine for glycines at positions 111 and 117 resulted in about 50- and 7-fold reductions of activity, respectively. Substitution of leucine for tryptophan 120 resulted in a 7-fold reduction of activity indicating that tryptophan at this position contributes to, but is not essential for, enzymatic activity in spite of its presence in nearly all eukaryotic cytochromes P450. The results are consistent with a model in which amino acids 112-114, and possibly 115, align with a loop of bacterial P450cam sequence containing substrate contacting amino acids, tyrosine 96 and phenylalanine 98. Glycines at either end of the loop in cytochrome P450 2C2 appear to be critical for activity.

Amino Acid Sequence↗
PubMed1993

Immunocytochemical heterogeneity of lactase-phlorizin hydrolase in adult lactase deficiency.

BACKGROUND: Adult lactase deficiency may result either from diminished synthesis of precursor lactase-phlorizin hydrolase (phenotype I deficiency) or from altered posttranslational processing of the precursor protein (phenotype II). The aim of this study was to compare the location of lactase-phlorizin hydrolase along the crypt-villus axis in control with adult lactase-deficient subjects. METHODS: The immunocytochemical distribution of lactase-phlorizin hydrolase was studied in subjects with adult hypolactasia and in controls with persistent high lactase expression. RESULTS: Duodenal biopsy samples from controls showed increasing intensity of brush border staining from upper crypt to midvillus. Subjects with phenotype I deficiency showed reduced and more patchy reaction product over brush borders. In some, maximal staining was localized over the upper half of the villi. The subject with phenotype II deficiency showed patchy staining but also intracellular accumulations of immunoreactivity within the apex of enterocytes mainly on the upper half of villi. Subsequent immunoelectronmicroscopy showed nearly a fourfold increase in label over the endoplasmic reticulum. CONCLUSIONS: These findings support prior observations of diminished enzyme synthesis in phenotype I lactase deficiency and suggest that the alterations in posttranslational processing in phenotype II deficiency involve a partial block in transport from endoplasmic reticulum to Golgi apparatus.

Biopsy↗
PubMed1993

Non-attendance at outpatient clinics: is it related to the referral process?

Non-attendance at outpatient clinics is a complex problem and previous studies have concentrated on hospital-related factors. It has been suggested that non-attendance might be related to the referral process, including the selection of patients for referral and the quality of communication between GP and patient. These issues are examined in a study of 1492 patients given first-time appointments at ENT and gastroenterology clinics. Non-attendance rates were 26 and 20% respectively. Non-attendance was not related to the nature, severity or duration of the patients' presenting problems at the time of referral or to their perception of the need for referral. Resolution of symptoms did not appear to be a major reason for non-attendance. Patients were significantly less likely to attend if they had been unable or only partly able to discuss their health problem with their general practitioner. Those who had requested referral were equally likely to default.

Adult↗
PubMed1993

Important deficits of lung function in three modern colliery populations. Relations with dust exposure.

To determine whether dust-related "clinically important" deficits of lung function still occur in British coal miners we have analyzed the relationship between lifetime cumulative exposure to respirable dust and risk of defined functional deficits in a population of miners who were examined between 1981 and 1986. The study group consisted of a sample of men who had worked at any one of three collieries (South Wales, Yorkshire, and North East England) between 1970, when new dust standards were introduced, and date of medical survey. There were 1,671 men studied, including men who had left the collieries. "Clinically important" deficits of FEV1 from predicted values derived in this population were defined by comparisons with questionnaire data on exercise tolerance limited by breathlessness. The mean FEV1 of men in the South Wales colliery, for example, who said they had to stop for breath when walking at their own pace on level ground was 942 ml less than the predicted value for nonsmokers after taking age and stature into account. Individual cumulative exposures to respirable dust were calculated from a long-term program of measurements of dust concentrations and occupational records commencing in 1953. In the three colliery populations, 24, 24, and 12% in South Wales, Yorkshire, and the North East, respectively, had FEV1 deficits that were at least as severe as the average deficit associated with the severe grade of exertional dyspnea described above. In all collieries deficits were more common in smokers than in nonsmokers, and more common in men who had left the industry than in men still within it.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

The use of carbon dioxide as an insufflation agent in barium enema--does it have a role?

A double blind prospective study was undertaken to evaluate the benefit of using carbon dioxide in double contrast barium enema (DCBE). 142 consecutive patients referred for DCBE were randomly allocated to receive either air or carbon dioxide (CO2) as the insufflation agent. The use of CO2 reduced the incidence of immediate and delayed severe pain from 31% to 12.5% and from 12.9% to 4.2% respectively. There was a statistically significant higher incidence of delayed severe pain in the younger age group as found in previous studies. Post-evacuation films showed that there was less residual gas after CO2. The quality of the DCBE was unchanged. We urge the more widespread use of CO2 as insufflation agent in DCBE.

Adult↗
PubMed1992

Complete rescue of photoreceptor dysplasia and degeneration in transgenic retinal degeneration slow (rds) mice.

retinal degeneration slow (rds) is a semidominant mutation of mice with the phenotype of abnormal development of rod and cone photoreceptors, followed by their slow degeneration. The rds gene has been putatively cloned and its novel protein product initially characterized biochemically. In the present study we undertook to correct in vivo the retinal phenotype of mice with the rds mutation. We assembled a transgene containing a regulatory segment of the opsin gene positioned upstream of the wild-type rds coding region. Mice from three transgenic lines, homozygous for the rds mutation, were analyzed for expression of the transgene and for their retinal phenotypes. In two high expressing lines, we observed complete reversion to wild-type retinal morphology. In a third, low expressing line, we observed a retinal phenotype intermediate between wild type and rds/rds, suggesting partial rescue of the mutation. These results constitute formal proof that we have cloned the rds gene.

Animals↗
PubMed1992

Characterization and comparison of Australian human spotted fever group rickettsiae.

The microbiological and molecular characteristics of the rickettsiae isolated from humans with Queensland tick typhus (QTT) caused by Rickettsia australis and the recently described Flinders Island spotted fever (FISF) were compared. Clinically and serologically, the diseases are similar. Cell culture reveals differences in the plaque-forming abilities of the isolates. Characterization of the gene encoding the genus-specific 17-kDa antigen of R. australis revealed a unique nucleotide sequence unlike those of the FISF isolate and Rickettsia rickettsii. Southern blot analysis of rickettsial DNA from the isolates with a 17-kDa-antigen gene probe revealed the presence of this gene in all isolates but no difference in banding patterns. When a probe for the rRNA genes was used, clear differences in banding patterns of isolates from patients with QTT and FISF were revealed. Thus, the rickettsiae isolated from patients with FISF differ from those from patients with QTT and may represent a new rickettsial species.

Antigens, Bacterial↗
PubMed1992

Regulation of intestinal lactase in adult hypolactasia.

Relative deficiency of intestinal lactase activity during adulthood, adult hypolactasia, is a common condition worldwide. We studied the regulation of lactase-phlorizin hydrolase in normal and adult hypolactasic subjects by correlating transcript abundance in intestinal biopsies with relative synthetic rates for the protein in cultured intestinal explants. After metabolic labelling studies in six subjects, precursor lactase-phlorizin hydrolase was identified in amounts directly proportional to the enzyme-specific activity suggesting that levels of intestinal lactase are regulated by synthetic rate. Total intestinal RNA was extracted from biopsies of these subjects and three hypolactasic adults who had participated in previous biosynthesis studies. Transcript levels were markedly reduced in deficient subjects who demonstrated diminished lactase-phlorizin hydrolase synthesis. The sequence of 1 kb of 5'-flanking region of the lactase-phlorizin hydrolase gene was determined in two hypolactasic subjects and two controls. No sequence variability was identified to account for differences in mRNA levels or biosynthetic rates between the two groups. A single hypolactasic subject previously characterized as demonstrating delayed posttranslational processing, showed message levels intermediate between other deficients and controls. These results suggest that in the majority of our subjects, pretranslational mechanisms account for the predominate regulatory control of lactase-phlorizin hydrolase expression in the proximal intestine.

Adult↗
PubMed1991

Computer analysis of the shape of spread of epidemics on a grid.

Models concerned with the spatial features of epidemic spread are often defined in terms of a nearest-neighbor grid network. It has been strongly conjectured, and can be proved in certain cases, that the infected area has an asymptotically well-defined shape. The present work concerns computer analysis of the shape of spread of a discrete-time single-parameter infection process on an eight-neighbor lattice. Results of extensive simulation are displayed using up-to-date exploratory data analysis software, and various attempts at fitting functions to the probability surfaces are considered.

Computer Simulation↗
PubMed1991

Factors influencing the communication skills of first-year clinical medical students.

The aim of this study was to examine the factors influencing medical students' communication skills. The sample comprised all first-year clinical students. Thirty-two received teaching in communication skills during the year; the remaining 56 did not. Students' career preferences, attitudes towards communication skills and confidence in their ability to communicate with patients were assessed by questionnaire at the beginning and end of the year. At the end of the year each student was videotaped interviewing a simulated patient. Students' communication skills were assessed on the basis of this interview by raters using a standardized rating scale, and by patient questionnaires. While there was some evidence that brief communication skills training improved skills, sex of student was a more significant predictor of level of skill. Students who perceived communication skills as less relevant to medicine and those who were more confident about their own communication skills were more likely to prefer a career in hospital medicine. Students' judgements of their ability to communicate effectively were poor. In the main there was no relationship between confidence and level of skill: where they were related, the association was negative. The benefits from communication skills training might be enhanced by involving hospital doctors in the teaching, and providing students with detailed video feedback on their skills at the outset.

Attitude of Health Personnel↗