Biomedical subjects
H Roberts
Publications and source records attributed to H Roberts.
Detection of peptidases in Trypanosoma cruzi epimastigotes using chromogenic and fluorogenic substrates.
Detergent extracts of Trypanosoma cruzi epimastigotes catalysed the hydrolysis of a range of amino-acyl and peptidyl p-nitro-anilides and aminomethylcoumarins. At least three enzymes were detected that cleave Z-Phe-Arg-MCA. Two of these were optimally active at alkaline pH, the other at pH 4.0. Of the two enzymes with alkaline pH optima, one was a cysteine peptidase and was unable to cleave Bz-Arg-MCA readily, whilst the other cleaved Bz-Arg-MCA and was inhibited by diisopropyl fluorophosphate. The acidic enzyme was similar to cathespin L of other eukaryotes with respect to its pH profile, substrate-specificity and inhibitor-sensitivity. Evidence was presented that epimastigotes contain a cysteine-type dipeptidyl aminopeptidase, one or more aminopeptidases, and a serine peptidase that cleaves Boc-Ala-Ala-pNA. Digitonin solubilization of the activities from cells supports the hypothesis that the cathespin L-like enzyme and the dipeptidyl aminopeptidase are lysosomal, whilst the Bz-Arg-MCA hydrolase, the aminopeptidases and the Boc-Ala-Ala-pNA serine peptidase are cytosolic.
Evaluation of a recombinant antigen ELISA for the diagnosis of acute toxoplasmosis and comparison with traditional antigen ELISAs.
An evaluation of five ELISA methods for the diagnosis of acute toxoplasmosis was undertaken by comparing a laboratory-produced ELISA employing two recombinant Toxoplasma gondii polypeptides as antigen with a laboratory-produced ELISA and three commercially available ELISAs employing traditional parasite antigen preparations derived from whole tachyzoites. With a panel of 75 sera from patients who showed either serological and clinical evidence of acute toxoplasmosis, or of diseases caused by other infectious agents, or from patients who showed no evidence of infectious disease, the ELISAs gave overall positive predictive values of 81.6-100%, negative predictive values of 87.8-100%, sensitivities of 81.3-100%, and specificities of 83.7-100%. No two ELISAs gave identical results with all sera tested. In total, the ELISA based on the two recombinant T. gondii polypeptides appeared to be the most specific ELISA in this comparison, showing positive predictive values and specificities of 100% for all groups of patients tested. The overall negative predictive value for this ELISA was 87.8% and the sensitivity was 81.3%. Therefore, the ELISA based on recombinant antigen appears to be a promising advance in the serological diagnosis of acute toxoplasmosis.
How many people think they have hay fever, and what they do about it.
Little is known about the number of people who perceive themselves to be sufferers of hay fever. This study investigated how many people between the ages of 15 and 59 years perceived themselves to be hay fever sufferers and how they treated themselves. The study was carried out in a general practice in Arnold, Nottingham, using a postal questionnaire, to which the response rate was 77% from a sample size of 1062. Of the 813 respondents, 232 (29%) claimed to have had hay fever within the last two years. The prevalence of hay fever decreased significantly with age, and was associated with a history of asthma. One hundred and twenty five sufferers (54%) used over the counter treatments for their hay fever, and one third of these said that they felt drowsy after using them. These findings point to the need for general practitioners to be aware that a number of people, more than has been indicated by previous surveys, perceive themselves to be hay fever sufferers and are prepared to treat themselves using over the counter preparations.
Bone density in women receiving depot medroxyprogesterone acetate for contraception.
OBJECTIVE: To determine if the use of the injectable contraceptive depot medroxyprogesterone (DMPA), which reduces ovarian oestrogen production, is associated with changes in bone density. DESIGN: Population study. DMPA users were compared with two control groups selected from larger population studies and individually matched for several putative determinants of bone density (age, race, body mass index, and years of oestrogen deficiency). Controls and DMPA users were matched without prior knowledge of their bone density measurements. SETTING: Teaching hospital and community family planning clinics. SUBJECTS: 30 current users of DMPA with a minimum five years' previous use, 30 premenopausal controls, and 30 postmenopausal controls. MAIN OUTCOME MEASURE: Lumbar spine and femoral neck bone mineral density assessed by dual energy x ray absorptiometry. RESULTS: Compared with premenopausal controls matched for age, race, and body mass index, DMPA users had significantly reduced bone density in the lumbar spine (mean difference 7.5% (95% confidence interval 1.9% to 13.1%), p = 0.002) and in the femoral neck (6.6%, (0.8% to 12.3%), p = 0.007). Compared with postmenopausal controls matched for body mass index and duration of oestrogen deficiency, DMPA users had greater bone density in the lumbar spine (8.9% (4.3% to 13.5%), p = 0.001), but in the femoral neck the difference in bone density was less (4.0% (-0.4% to 8.5%), p = 0.04). CONCLUSIONS: Women using DMPA have bone density values intermediate between those of normal premenopausal and postmenopausal controls; thus, the degree of oestrogen deficiency induced by DMPA may have an adverse effect on bone density.
Managing miscarriage: the management of the emotional sequelae of miscarriage in training practices in the West of Scotland.
Miscarriage is a very common event which is rarely a medical emergency, and which, from a biomedical perspective, may justifiably be viewed as a 'normal' complication of early pregnancy. From the mother's point of view however, the loss of a wanted pregnancy may be viewed quite differently. A number of studies have identified significant levels of dissatisfaction with the medical care which women have received at the time of a miscarriage. This paper describes a survey of the management of miscarriage by general practitioner trainees and trainers in the West of Scotland and on the basis of responses to a series of MEQ-type questions, indicates GPs views on the importance of counselling, sympathetic listening and good information in this area. The translation of these attitudes and beliefs into practice is, of course, a different issue, and one which may be affected by the task-oriented approach of the new contract.
The use of anti-D prophylaxis in the management of miscarriage in general practice.
Deaths from rhesus (Rh) haemolytic disease dropped steeply after anti-D immunoglobin became available for prophylaxis in Britain in 1969. Nevertheless, Rh incompatibility remains a cause of perinatal mortality and some unregistered fetal deaths before 28 weeks gestation. Some of these deaths are attributed to a failure to administer anti-D immunoglobin in the appropriate circumstances. The prophylactic administration of anti-D immunoglobin to Rh negative women or women whose Rh type was unknown was explored as part of a survey of the management of miscarriage in general practitioner training practices in the West of Scotland. Trainees were found to be the most likely, and general practitioners who had qualified before 1970 the least likely to offer anti-D prophylaxis. The advice of the Health Departments is currently unambiguous about the need to administer anti-D immunoglobin after miscarriage. The findings described here indicate the need to implement this advice more effectively until the question of first trimester sensitisation has been resolved.
History of the Medical Services in Weston-super-Mare.
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Child protection. Accident prevention: a community approach.
Child accidents are the main cause of death and a considerable cause of morbidity in children, as well as anxiety to adults. Attempts to tackle this major health problem have tended to rely on campaigns of education and exhortation; public health strategies remain underdeveloped. Health visitors are well placed to pursue child safety strategies which build on parents' own knowledge and experience. Helen Roberts describes an initiative based not on the question, why did that accident happen? but the more intriguing question of how is it that most parents manage to keep their children safe most of the time and what can we learn from them?
Substrate specificity and inhibitor sensitivity of a trypanosomatid alkaline peptidase.
An alkaline peptidase of Trypanosoma cruzi and Crithidia fasciculata, previously shown to cleave on the carboxyl side of arginine and lysine residues, was examined for its ability to cleave various fluorogenic substrates and for its sensitive to peptidase inhibitors. The enzyme of both T. cruzi and C. fasciculata has a preference for cleavage of substrates with basic amino acids at the P2 as well as the P1 position of the peptide chain. Arginine and lysine are equally acceptable at P2, whereas the enzyme prefers arginine to lysine at P1. An influence of the P3 amino acid residue on substrate cleavability was also apparent. The peptidase was highly susceptible to inactivation by peptidylfluoromethanes, peptidyldiazomethanes and peptidylsulphonium salts that contained arginine or lysine at P1. Additionally, diisopropylfluorophosphate inhibited the enzyme, whereas trans-epoxysuccinylleucylamido(4-guanidino)butane and iodoacetic acid were relatively weak inhibitors. Various reversible inhibitors of the enzyme were also examined. Inhibition by members of the primary aliphatic amine series, methylamine to n-heptylamine, showed a peak of inhibition at n-butylamine, which most closely resembles the lysine side chain. Agmatine, which resembles the arginine side chain, also strongly inhibited the peptidase. The kinetics of inhibition by these basic compounds were of the competitive type. Pentamidine and hirudonin, which resemble two arginine side chains joined together, were more effective inhibitors of the trypanosomatid peptidase than bases resembling only one arginine or lysine side chain.
Oral cancer and precancer: after-care and terminal care.
This paper looks at the social and psychological effects of cancer on patients and their families, and discusses the support and after-care required by a patient who has been treated for an oral cancer. The role of the dental practitioner in the maintenance of oral health and comfort is discussed, and the management of the side-effects of the different treatment modalities is described. The particular problems and needs of patients, and the relatives of patients, in the terminal stages of oral cancer are also discussed.
Substrate specificity and inhibitor sensitivity of a Trypanosoma cruzi alkaline peptidase.
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Acute bacterial meningitis. I: Diagnosis.
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Acute bacterial meningitis. II: Treatment.
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Privacy for a handicapped child.
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Hospital ethical committees.
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Serodiagnosis of acute toxoplasmosis in macropods.
The sera of 34 Australian macropods, the brains of which had been bioassayed for Toxoplasma gondii, were used to establish that a titre greater than 1/32 was significant for a direct agglutination test against toxoplasmosis. In addition, the concentration of 2-mercaptoethanol required to destroy the IgM fraction of macropod serum was confirmed in a modified direct agglutination test. To further validate the tests, the serological responses of three eastern grey kangaroos (Macropus giganteus) dosed orally with T. gondii oocysts and one M. giganteus injected with T. gondii cysts were studied. The tests were then used to investigate a diagnosis of acute toxoplasmosis in four Tasmanian pademelons (Thylogale billardierii) clinically suspected of acquiring toxoplasmosis naturally. One hundred and fifty-one Bennett's wallabies (Macropus rufogriseus rufogriseus) and 85 T. billardierii were also tested to determine the prevalence of acute toxoplasmosis of macropods in the wild. Four percent of M. r. rufogriseus and 1.2% of T. billardierii possessed T. gondii-specific IgM in their sera.