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Biomedical subjects

N A Saunders

Publications and source records attributed to N A Saunders.

At least 91 records · Page 5Linked to original sources
PubMed1991

Measurement of IgM responses to a subunit influenza A vaccine by sucrose-gradient centrifugation and membrane-filtration enzyme immunoassays.

IgM responses to a deoxycholate-split influenza vaccine containing the surface antigens of the H3N2 virus A/Philippines/2/82 were studied in five volunteers, three of whom were seronegative by haemagglutination inhibition (HI) tests. Responses were measured by a sucrose-gradient centrifugation technique, in which IgM-specific HI activity was computed as a proportion of total IgM and IgG-specific HI activity, and by a membrane filtration-enzyme immunoassay (MF-EIA). Responses could be detected in all volunteers when measured by sucrose-gradient centrifugation within 1-2 weeks, and the IgM induced was 5-40% of total HI-specific activity. The response was also observed in the presence of low levels of pre-existing antibody. Levels of IgM antibody, when measured by MF-EIA, could be easily detected in two of the volunteers, while those of two others were very low and there was no response in a fifth. No biphasic virus-specific response to vaccination, involving first IgM and then IgG, could be measured by either technique. From these studies, the sucrose-gradient fractionation technique appears to be the more sensitive procedure.

Centrifugation, Density Gradient↗
PubMed1991

The use of 16S ribosomal RNA analyses to investigate the phylogeny of the family Legionellaceae.

The 16S ribosomal RNA sequences of Legionella pneumophila, L. erythra, L. hackeliae, L. spiritensis, L. longbeachae, L. bozemanii (Fluoribacter bozemanae) and L. micdadei (Tatlockia micdadei) were determined using reverse transcriptase. The sequences were compared with published sequences for Gram-negative bacteria and phylogenetic trees were constructed. The data confirm previous work which showed that the family Legionellaceae forms a monophyletic subgroup within the gamma subdivision of the Proteobacteria. The data show that all of the legionellae studied are highly related (greater than 95%) on the basis of 16S rRNA sequences and do not support the division of the family Legionellaceae into three genera.

Base Sequence↗
PubMed1991

An epidemiologically valuable typing method for Neisseria meningitidis by analysis of restriction fragment length polymorphisms.

A restriction fragment length polymorphism (RFLP) typing method was developed for Neisseria meningitidis. A cloned EcoRI fragment from a Neisseria meningitidis Group B serotype 15P1.16 sulphonamide-resistant strain was used to probe Southern blots of total chromosomal DNA restriction fragments (enzyme AvaI). A group of 75 apparently unrelated organisms gave rise to 26 different restriction fragment length patterns and two different groups of epidemiologically related strains had RFLP patterns that were distinct for each group. The technique was highly reproducible and discriminatory. The RFLP data were compared with the results of serotyping and subtyping and isoenzyme electrophoretotyping. The RFLP data were consistent with those from the alternative typing methods; clones defined by isoenzyme analysis were subdivided by this technique. The use of RFLP typing by cloned probes should be of considerable epidemiological value.

Blotting, Southern↗
PubMed1991

A comparison of probes for restriction fragment length polymorphism (RFLP) typing of Legionella pneumophila serogroup 1 strains.

The use of probes derived from rRNA sequences to detect restriction fragment length polymorphisms (RFLPs) associated with the ribosomal RNA genes for epidemiological typing (ribotyping) is a powerful and readily applicable tool. Different probes and enzymes for ribotyping were compared for a series of 73 unrelated Legionella pneumophila serogroup 1 strains. The probes compared were cDNAs, transcribed from L. pneumophila or Escherichia coli rRNA subunits, and a cloned L. pneumophila rRNA gene. The cloned rRNA gene probe gave the best discrimination and this probe was further compared with cloned probes comprised of randomly selected (non-rRNA) parts of the L. pneumophila chromosome. In this instance the greatest discrimination was achieved when one of the non-ribosomal RNA gene probes was employed. The overall discrimination of RFLP typing was enhanced by combining the data obtained with both rRNA and non-rRNA probes.

Bacteriophage lambda↗
PubMed1991

Second serogroup of Legionella quinlivanii isolated from two unrelated sources in the United Kingdom.

A series of strains, presumptively identified as legionellas on the basis of their nutritional requirements and biochemical reactivity, were isolated from two unrelated environmental sources in the UK. Representatives of each of these series had a restriction endonuclease digest pattern indistinguishable from that of the Legionella quinlivanii type strain (1442-AUS-E) and the identity of these strains was confirmed by DNA homology studies. Serological examination of the two strains showed that they were distinct from the type strain 1442-AUS-E but indistinguishable from each other. A second serogroup, L. quinlivanii serogroup 2 (type strain LC870; NCTC 12434), is proposed to accommodate these strains.

Air Conditioning↗
PubMed1991

Wheat dust-associated respiratory disease in a farming community.

Sixty-six volunteers who considered themselves to have wheat dust-related respiratory disease, were reviewed from a farming community. A spectrum of disease was described ranging from a mild allergic rhinitis limited to periods of wheat dust exposure through to perennial asthma in which wheat dust was but one of several precipitating factors. Approximately half of those with asthma had symptoms limited to times of wheat dust exposure. Results of a limited survey of farmers showed patterns of symptoms similar to those in the volunteer group. Most subjects were atopic with elevated IgE levels, and had positive skin prick tests to environmental allergens. All but one of 65 subjects tested had a positive RAST test to wheat dust antigen. It is concluded that wheat dust associated respiratory tract disease is a significant problem in Australian farming communities, that a particular pattern of asthma can be described, and that IgE mediated reactions contribute to this disease pattern.

Adolescent↗
PubMed1991

Long-term nasal CPAP does not ameliorate obstructive sleep apnoea.

Fifty-seven patients with obstructive sleep apnoea (OSA) were treated for at least six months with nasal continuous positive airway pressure (CPAP). At follow-up, sleep studies were performed in which CPAP was not used for the first half of the night. We compared the severity of OSA at follow-up without CPAP to the severity of OSA during the patient's initial diagnostic study. Apnoea and hypopnoea index (AHI) fell from 41.4 +/- 7.5 (mean +/- 95% CI) to 34.8 +/- 7.9 (p = 0.06 by Wilcoxon test) and minimum oxygen saturation rose from 71.6 +/- 3.2 to 78.5 +/- 2.6 (p less than 0.001). Some of this change may have been due to reduced REM sleep in the follow-up study (10.5 +/- 2.1% Total Sleep Time vs 7.4 +/- 2.4% TST, p less than 0.05). Long-term nasal CPAP was not associated with any reduction of obesity (BMI before CPAP 31.9 +/- 1.0, after CPAP 31.7 +/- 1.0 (p = 0.39). Systolic arterial pressure fell (before CPAP 143.0 +/- 4.5 mmHg, after CPAP 136.3 +/- 4.6, p less than 0.05) but diastolic pressure did not (before CPAP 88.5 +/- 3.0 mmHg, after CPAP 85.6 +/- 2.9 mmHg, p = 0.11). We concluded that the effect of CPAP treatment for six or more months was a small fall in AHI and a small rise in minimum SaO2, but that this would be of marginal clinical significance, and may be artefactual.

Aged↗
PubMed1991

Differences in the symptoms of men and women with obstructive sleep apnoea.

In order to determine whether the clinical features of obstructive sleep apnoea (OSA) are the same in men and women we reviewed the records of 22 women with OSA. The women were matched with 44 men of similar age (+/- 5 years) and frequency of respiratory events (less than or equal to 15/hr, 16-40/hr, 41-70/hr and greater than 70/hr). The degree of daytime somnolence was similar in men and women. Women are more likely than men to complain of morning fatigue and morning headache, and less likely to report restless sleep or to have been told of apnoea during sleep. Difficulty initiating sleep (DIS) was twice as common in women as in men (p less than 0.05). Most of these differences were also seen when women and men who snored but did not have OSA were compared. Arterial hypertension was less common in women (3/22) than in men (18/44), (p less than 0.001). More striking than the differences between men and women in the prevalence of single symptoms was the existence of a subgroup of women (9/22) with no complaint of either apnoea, choking arousals or restless sleep, and normal blood pressure, complaining only of fatigue and morning headache, and in three cases DIS as well. We concluded that OSA may be commoner in women than previous reports suggest, and that the clinical features may be misleading in women.

Adult↗
PubMed1991

Long-term acceptance of continuous positive airway pressure in obstructive sleep apnea.

We studied the long-term acceptability of nasal continuous positive airway pressure (CPAP) treatment in 168 consecutive patients, 147 with obstructive sleep apnea (OSA) and 21 with snoring. Follow-up was between 1.5 and 78 months. At latest follow-up 107 of 168 (64%) were still using CPAP. Acceptance of CPAP was least for patients with snoring alone (6 of 21 persisted) and best for patients with both excessive daytime somnolence and severe hypoxemia (minimum SaO2 less than 75%), of whom 40 of 45 (89%) persisted with treatment. Patients with excessive daytime somnolence but without severe hypoxemia were less tolerant of CPAP (39 of 71, 55%, persisted) than patients with no symptoms of excessive somnolence but with severe hypoxemia (21 of 30, 70%, persisted). The most common reasons for discontinuing CPAP were intolerance of the mask (26 of 61), the inconvenience of treatment (16 of 61), and the lack of symptomatic benefit from treatment (10 of 61). We concluded that long-term acceptance of CPAP was difficult to predict in advance but that it was most likely in patients with the most severe sleep apnea. Because intolerance of the mask and inconvenience were the most common reasons for ceasing treatment, improvements in the design of CPAP systems and careful patient training may improve the acceptability of CPAP substantially.

Female↗
PubMed1991

Evaluation of a new asthma questionnaire.

The new International Union Against Tuberculosis (IUAT) bronchial symptoms questionnaire was completed by 827 subjects participating in a prospective study of respiratory symptoms and lung function in aluminum smelter workers. A modified Medical Research Council (MRC) questionnaire was also administered. Bronchial reactivity (BR) was measured in 809 subjects by methacholine challenge using a rapid method. Factor analysis demonstrated sensible clustering of responses to items unique to the new questionnaire such as nocturnal, spontaneous, and postexertional dyspnea, dust-induced dyspnea and tightness, and breathing difficulty. Responses to IUAT questions concerning past asthma, wheeze, chest tightness, morning cough and sputum, and asthma medication agreed well with corresponding items from the MRC questionnaire. Questions concerning asthma, medication, dust-induced, nocturnal, and spontaneous dyspnea, chest tightness, wheeze, nocturnal cough, postexertional dyspnea and breathing difficulty also had high validity against the criterion of concurrently measured bronchial reactivity. It is concluded that the IUAT questionnaire is a valid asthma questionnaire.

Asthma↗
PubMed1991

Night-to-night variability of disturbed breathing during sleep in an elderly community sample.

Night-to-night variability of breathing and oxygenation during sleep was examined with portable monitoring equipment in 30 residents of a retirement village. Subjects had a variety of health problems as might be expected in the elderly, but all were living independently in self-contained units. None had clinical features to suggest obstructive sleep apnea. Two pairs of consecutive nights were studied, separated by 4-6 months. Satisfactory recordings on all four nights were obtained in 15 subjects, and in these subjects variability of measurements was examined across nights 1-4 using the kappa (K) statistic. There was low but significant agreement in estimated total sleep time (K = 0.23, p less than 0.01) and estimated wakefulness after sleep onset (K = 0.18, p less than 0.05) as assessed with a wrist actigraph. Good agreement was found among measures of disturbed breathing during sleep whether expressed in terms of numbers of events [respiratory disturbance index (RDI), K = 0.62, p less than 0.0001], their duration (event minutes, K = 0.53, p less than 0.0001), or associated disturbance of oxygenation (% cumulative time less than 90% SaO2, K = 0.50, p less than 0.001, n = 9). Twenty-eight subjects had at least two nights' satisfactory recordings. Although some of these individuals showed considerable variation in RDI, this had little overall effect on classification of them into normal (RDI less than or equal to 15) and abnormal groups. The accuracy of the first night's recording in predicting classification derived from recording on three or four nights was 83%.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1990

Phenotypic variation amongst genotypically homogeneous Legionella pneumophila serogroup 1 isolates: implications for the investigation of outbreaks of Legionnaires' disease.

One hundred and seventy-nine isolates of Legionella pneumophila serogroup 1, obtained from a site associated with an outbreak of Legionnaires' disease, were examined by monoclonal antibody subgrouping, restriction fragment length polymorphism typing, restriction endonuclease analysis and plasmid content. Nine distinct phenotypes were detected but at the genotypic level all strains were closely related. The data presented indicate that phenotypic variation of a single parent strain can occur within an environmental site. The implications of these findings are discussed in relation to the investigation of outbreaks of Legionnaires' disease.

Culture Media↗
PubMed1990

Dementia and abnormal breathing during sleep.

We have examined a group of cognitively impaired elderly people who already showed some increase in indices of sleep-disordered breathing and applied standard criteria for dementia to them. This resulted in a subgroup of truly demented subjects who showed significantly more abnormal breathing during sleep than either normal subjects or those whose cognitive impairment may not have been due to a dementing illness.

Aged↗
PubMed1990

Recognition of depression in the elderly: a comparison of general practitioner opinions and the Geriatric Depression Scale.

As part of a larger study, 133 subjects aged 70 years and over were screened for depression using the Geriatric Depression Scale, a 30-item questionnaire, as the screening instrument. Cognitive status was assessed using the Mini Mental State Examination. The subject's own general practitioner was asked his/her opinion as to whether the subject was depressed. Poor agreement was found between depression as measured by the Geriatric Depression Scale and the general practitioner's assessment. Possible reasons for this include the difficulty of finding a satisfactory operational definition of depression for use by general practitioners, the problems of identifying depression in the elderly, the arbitrary definition provided by the scale and the confounding of depression, as measured by the scale, with cognitive status.

Aged↗
PubMed1990

A method for typing strains of Legionella pneumophila serogroup 1 by analysis of restriction fragment length polymorphisms.

A restriction fragment length polymorphism (RFLP) typing method for Legionella pneumophila serogroup 1 was developed. The method depended upon the use of cloned EcoR1 fragments from L. pneumophila (Knoxville-1) probing Nci1 restriction fragments of chromosomal DNA. Examination of strains of L. pneumophila which were apparently unrelated showed that inter-strain RFLPs were common, and these formed the basis of the typing scheme. The technique was found to be highly reproducible and discriminatory. When the RFLP data were compared to that obtained by monoclonal antibody (MAb) subgrouping both methods of strain differentiation gave consistent results. The isolates examined by either method were also sub-divided by the alternative technique. The analysis of RFLPs by cloned probes should be of considerable epidemiological value.

Antibodies, Monoclonal↗
PubMed1990

Epidemiological typing of Yersinia enterocolitica by analysis of restriction fragment length polymorphisms with a cloned ribosomal RNA gene.

Intra-species restriction fragment length polymorphisms (RFLPs) of Yersinia enterocolitica were detected in assays with a cloned DNA fragment from Legionella pneumophila that included the 16S and 23S rRNA genes. By use of this method it was possible to identify different RFLP types within biogroups/serogroups which were indistinguishable by other means. Thus the 37 biogroup IV/serogroup O3 strains isolated worldwide from pig carcasses, pork and human patients, were subdivided into five different RFLP-types. Typing based on RFLP analysis was sensitive and independent of phenotypic characters. The method will be of value for the identification and evaluation of possible reservoirs and routes of infection.

Animals↗