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Biomedical subjects

A D Malcolm

Publications and source records attributed to A D Malcolm.

At least 55 records · Page 3Linked to original sources
PubMed1987

Cross-hybridisation of human papillomavirus DNA on filters.

Accurate type assignment of the different HPV types which infect the female genital tract, is essential in view of the differing pathological potential of the common virus types present in the cervix. We have developed hybridisation, washing and autoradiography conditions that minimise cross-hybridisation on filters and so allow clear-cut type assignment. We describe the conditions in this paper and have used this method to screen for HPV infection in clinical populations.

Autoradiography↗
PubMed1987

Use of hybridot assay to screen for BK and JC polyomaviruses in non-immunosuppressed patients.

Urine samples from 50 patients attending a genitourinary outpatient clinic and from 13 renal allograft recipients were investigated for evidence of infection with human BK and JC polyomaviruses using cytology and a new DNA hybridot assay. Forty four per cent of samples from the renal allograft recipients were positive by cytology and 75% by DNA hybridisation, indicating that hybridot assay is more sensitive than cytological screening. BK and JC viral DNA was found in 20% of the patients attending the genitourinary clinic, showing infection with BK virus and JC virus in a group of patients with clinical conditions not normally associated with immunological deficiency-a finding that has not been reported before.

Adult↗
PubMed1987

DNA hybridization of cervical tissues.

The increasing frequency of cervical neoplasia among younger women and the increased invasiveness of these tumors has led to a considerable growth in research into this disease. Conventional methods (epidemiology, cytology, and immunology), while being extremely useful, also have significant limitations. Recent advances in techniques for the manipulation of DNA now make it possible to analyze tissues for the presence of viral genomes. This review introduces these techniques and describes their application to the search for herpes simplex virus and human papillomavirus sequences in cervical tissue. The significance of the findings both for the mechanism of transmission of the disease, and also the consequences for early detection and hence more successful treatment, are also discussed.

Cloning, Molecular↗
PubMed1987

DNA probes in human disease.

Nucleic acid probes are able to detect the presence of particular sequences in a sample down to the level of a few hundred molecules. They can discriminate between similar sequences to a resolution of better than one part in 10(9). They are capable of detecting inherited defects in tissues where the phenotype is not being expressed, and in cases where the biochemical aberration is not understood. They can characterize acquired diseases in somatic cells (both tumours and infectious agents). Additionally, they can be used to characterize multifactorial (either polygenic or requiring an environmental stimulus to interact with a genetic predisposition) diseases. Nucleic acid 'fingerprints' provide an unequivocal identification of the origin of cells which may be applied in criminal law, civil law, and in the follow up to bone marrow transplants. In spite of this tremendous potential, there is still a large gap between their use in research laboratories and their widespread application in pathology laboratories. There are two basic reasons for this. The first is the number of labour-intensive steps involved in the various 'blotting' techniques which greatly reduces the rate at which assays may be performed. The second is the need to use probes labelled with isotopes which are short-lived and may require stringent safety measures to be employed. Recent work both in this laboratory and elsewhere is designed to circumvent both these problems.

Biotin↗
PubMed1986

Trial of early nifedipine in acute myocardial infarction: the Trent study.

Over 30 months 9292 consecutive patients admitted to nine coronary care units with suspected myocardial infarction were considered for admission to a randomised double blind study comparing the effect on mortality of nifedipine 10 mg four times a day with that of placebo. Among the 4801 patients excluded from the study the overall one month fatality rate was 18.2% and the one month fatality rate in those with definite myocardial infarction 26.8%. A total of 4491 patients fulfilled the entry criteria and were randomly allocated to nifedipine or placebo immediately after assessment in the coronary care unit. Roughly 64% of patients in both treatment groups sustained an acute myocardial infarction. The overall one month fatality rates were 6.3% in the placebo treated group and 6.7% in the nifedipine treated group. Most of the deaths occurred in patients with an in hospital diagnosis of myocardial infarction, and their one month fatality rates were 9.3% for the placebo group and 10.2% for the nifedipine group. These differences were not statistically significant. Subgroup analysis also did not suggest any particular group of patients with suspected acute myocardial infarction who might benefit from early nifedipine treatment in the dose studied.

Adolescent↗
PubMed1986

Association of human papillomavirus with squamous carcinoma of the uterine cervix.

The frequent association of human papillomavirus infection with preinvasive and invasive cancers of the cervix has led to speculation that the viruses may be involved in the neoplastic process. We have carried out some epidemiological studies of the prevalence of human papillomavirus infection in the female genital tract to evaluate more fully the oncogenic potential of these viruses in the cervix. A non-invasive method of detecting the virus has been developed for this purpose using DNA hybridization of cervical scrapings. The technique has been used to carry out prospective studies of patients with cervical intraepithelial neoplasia (CIN) and to investigate infection in women treated by laser therapy for CIN. We have also studied women with normal cervices to determine the prevalence of human papillomaviruses in the normal population. Further studies have involved the investigation of the effect of interferon on virus replication and epithelial proliferation in women with CIN III.

Carcinoma in Situ↗
PubMed1986

The effect of interferon on human papillomaviruses associated with cervical intraepithelial neoplasia.

A double-blind, placebo-controlled, trial of leucocyte interferon showed that, contrary to previous reports, interferon had no significant effect on cervical intraepithelial neoplasia (CIN) when applied topically in a gel. DNA hybridization of cervical scrapes was used to monitor the effect of interferon on the human papillomaviruses (HPV) associated with CIN. There was, however, no significant difference in the expression of HPV 6 or 16 in the cervical epithelium of patients treated with interferon compared with those given a placebo. By using superficial cells scraped from the surface of the cervical epithelium as a source of DNA for viral studies, we were able to investigate the relation between HPV and CIN without interfering with the natural history of the disease. HPV 16 was detected in lesions which persisted while HPV 6 only was detected in one lesion that regressed. Regression was clearly associated with reduction in the number of copies of viral DNA per cell in this case. Dual infection with HPV types 6 and 16 were recorded in two patients with persistent lesions. In one patient, hybridization studies indicated that infection with HPV 16 could have occurred after infection with type 6 was established, and it is postulated that this may have changed the nature of the cervical lesion.

Adolescent↗
PubMed1986

Seizures associated with oxamniquine therapy.

Three patients who were treated for schistosomiasis mansoni with oxamniquine suffered generalized seizures. We suggest that this side effect may be more common than previously reported. Specific ethnic groups may be particularly at risk.

Adult↗
PubMed1986

Digitalis and diuretics: still the standard therapy?

Although digitalis preparations are effective in controlling the ventricular rate in atrial fibrillation and certain other supraventricular tachyarrhythmias, with consequent haemodynamic benefit, there is increasing controversy about significant sustained inotropic efficacy in patients in sinus rhythm. Digoxin toxicity is a serious hazard and subtherapeutic dosing a deception and waste of resources; blood levels are the key to optimum dosing. A considered withdrawal of the drug and reintroduction if haemodynamic deterioration ensues is probably the only way of proving in an individual patient if the drug is really worth using long-term. Diuretics have had a major place in management of cardiac failure, correcting the fluid overload. However there are a number of troublesome metabolic and other consequences, and excessive diuresis can be dangerous. Vasodilator therapy has recently had a major impact on management of more severe forms of cardiac failure, usually with coadministration of diuretics, but the predominant pattern of drug use in milder heart failure is to rely primarily or even exclusively on diuretics. Rational use of drugs in cardiac failure would be greatly facilitated by availability of simple non-invasive techniques to measure cardiac function and filling pressures. Until this becomes possible it will be difficult to alter the traditional pattern of long-term use of digoxin and diuretics whenever there have been symptoms attributable to heart failure.

Digitalis Glycosides↗
PubMed1985

Specific transcription of orthopox virus DNA by HeLa cell RNA polymerase II.

A HeLa cell extract was used to transcribe DNA isolated from cowpox virus. Truncated templates generate accurately initiated run-off transcripts of discrete sizes and whose sensitivity to inhibition by alpha-amanitin indicates synthesis by cell RNA polymerase II. A mapped restriction fragment of wild-type cowpox DNA contains specific sites of initiation which are not detected in the geographically equivalent fragment from a cowpox mutant having a defined sequence rearrangement in this region.

Amanitins↗
PubMed1985

Screening for wart virus infection in normal and abnormal cervices by DNA hybridisation of cervical scrapes.

Cervical scrapings from 78 women attending a sexually transmitted diseases (STD) clinic, family planning clinic, and colposcopy clinic were assayed for human papillomavirus type 6 (HPV-6) by DNA hybridisation. Results of hybridisation were compared with clinical, colposcopic, and cytological findings. Scrapings from 2 of the 4 women with genital warts gave positive results with the HPV probe. No HPV-6 DNA was detected in scrapings from 18 women attending an FPC whereas scrapings from 2 of 19 STD clinic patients with normal colposcopic and cytological examination were positive-this means that DNA hybridisation detected wart virus infection where previously none was suspected. HPV-6 DNA was detected in about 10% of cervical scrapings from women with cervical intraepithelial neoplasia (CIN) both before and after treatment. Indeed in 2 patients in whom viral DNA persisted after laser therapy, it was associated with local recurrence of neoplasia. This non-invasive technique is suitable for use as a screening test for HPV infection. In this study it identified women who have a high risk of developing CIN and in whom close cytological and colposcopic surveillance is indicated.

Animals↗
PubMed1985

Clinical and hemodynamic effects of the new dilator drug molsidomine.

The effects of a single 2 mg oral dose of molsidomine were assessed with treadmill multistage exercise testing in six men with stable angina. A double-blind, placebo-controlled protocol was used, with exercise to the point when anginal pain forced the patient to stop. Exercise was undertaken before and at 1/2, 1 1/2, 4, and 6 hours after drug administration. Molsidomine improved exercise performance, with the best antianginal effect at 1 1/2 hours after administration, when the mean times to limiting angina were approximately 6 3/4 minutes with placebo and 11 1/2 minutes with molsidomine (p less than 0.05). The corresponding energy expenditures were 33.8 and 77.6 mets, an increase of 130% with the active drug. Intra-arterial blood pressure recording verified that molsidomine had a vasodilator hemodynamic profile, and the immediate postexercise rate-pressure product 1 1/2 hours after molsidomine treatment was 232 mm Hg/min X 10(-2), compared with 183 mm Hg/min X 10(-2) after administration of placebo (NS). Side effects of molsidomine were limited to headache in two patients.

Adult↗
PubMed1985

Polyadenylation of a human mitochondrial ribosomal RNA transcript detected by molecular cloning.

We have identified by molecular cloning a polyadenylated RNA transcript in the human leukemia cell line, K562, which is complementary to a portion of the gene-encoding mitochondrial 16S ribosomal RNA (mt 16S rRNA). The cloned portion of the transcript corresponds to positions 2191-2395 of the human mt genome. The clone represents a cDNA copy of an RNA transcript from the H strand and carries an additional poly(A) tail 21 residues long at its 3'-end. Our data provide direct evidence for polyadenylation of some mt 16S rRNA transcripts.

Base Sequence↗
PubMed1985

A rapid method of gene detection using DNA bound to Sephacryl.

A rapid method of gene detection has been developed utilising DNA fragments immobilized on resins and a sandwich hybridization assay. This method permits the detection of restriction fragment length polymorphisms (RFLPs) without the need to immobilize sample DNA. The method is based on the use of two non-overlapping DNA restriction fragments, one of which is attached to a resin (fragment A) and the other 32P-labelled (fragment B). Fragments A and B will not hybridize to each other unless there is a DNA or RNA fragment capable of hybridizing to both A and B present in the same reaction. Hybridization in this instance will result in the resin being radioactively labelled. The RFLP associated with the mutation causing sickle-cell anaemia was used as a model to develop the method. The resin Sephacryl S-500 appeared most suited to our method for two reasons: (i) DNA immobilization experiments using two coupling procedures and four resins indicated that Sephacryl S-500 bound the most DNA with very little non-covalent coupling. (ii) Hybridization experiments with DNA bound to a number of resins showed that DNA bound to Sephacryl S-500 hybridized most efficiently with a low level of nonspecific hybridization. Using optimum hybridization conditions 5 X 10(-18) mol of beta-globin DNA could be detected. The method has been used to distinguish between DNA from sickle, heterozygote and normal patients.

Acrylic Resins↗
PubMed1985

Evaluation of an ELISA system for determination of class-specific antibodies to native and denatured DNA in man.

Enzyme-linked immunosorbent assays (ELISA) have been set up for determination of plasma IgG and IgM antibodies to native (n) and denatured (d) DNA. Normal male and female donors generally gave low values in the assays for IgG; IgM control values were higher, particularly in females. Mean values for patients with systemic lupus erythematosus (SLE) were greatly raised in all four categories of assay in relation to the control (female) group. Levels of IgG anti-nDNA in SLE correlated well with a standard diagnostic test (Farr), and this ELISA assay was more successful than Farr in discriminating between patients and normal females. No such correlation with Farr was found for IgM anti-nDNA. Correlations were found in SLE between levels of antibodies to nDNA and dDNA. Inhibition tests--including those with a plasmid DNA preparation containing no single-stranded regions--showed that most of the IgG antibodies determined in the 'native' assay were able to bind to nDNA and dDNA with comparable avidity, whereas most of those reacting in the 'denatured' assay could only bind dDNA. The former antibodies were probably directed against shared determinants on the deoxyribose-phosphate backbone and the latter against base-dependent structures not exposed in nDNA. Inhibition results for IgM assays were similar, though the predominance of antibodies specific for dDNA appeared less marked. ELISA assays could well prove more useful than established methods in diagnosis and monitoring of SLE and other diseases.

Antibodies↗