Search PubMed⌕ Search

Biomedical subjects

P R Lewis

Publications and source records attributed to P R Lewis.

At least 19 recordsLinked to original sources
PubMed2003

Symptoms of asthma: comparison of a parent-completed retrospective questionnaire with a prospective daily symptom diary.

In a study of the effects of indoor air pollution on the respiratory health of children in Newcastle, Australia, parental reports of symptoms experienced by children over the previous 12 months were compared with a prospective record of symptoms of cough and wheeze. Parents of 390 children aged 8-11 years completed a questionnaire about child and family respiratory health, which was used to assign children to one of four symptom groups: Wheeze (two or more attacks of wheezing in the last 12 months), Chest-Colds (two or more chest-colds in the last 12 months without wheezing), Cough Alone (a dry cough at night, without a cold or chest infection, that lasted for more than 2 weeks), or Control (none). A balanced sample of children (n=139) was invited to participate further by completing lung function tests, atopy testing, and keeping a daily diary of peak expiratory flow (PEF) and symptoms of cough and wheeze over a 7-week period. Valid data for the daily diary were provided by 66/85 (77.6%) of participants who commenced this stage (47.5% of the 139 invited to participate). The Wheeze group reported significantly more subsequent wheeze (median 16.8% of days) than the other three groups (median 0% of days). Parent reports of asthma-like symptoms over the previous 12 months were consistent with the subsequent experience of symptoms recorded in a daily diary.

Adult↗
PubMed2001

Evaluating the efficacy of vaccine storage in the general practice setting.

OBJECTIVES: To describe the implementation of guidelines for vaccine storage in general practice, and their effectiveness in achieving optimum vaccine storage temperatures in fridges. DESIGN: Repeated cross-sectional surveys over time--phase 1 1996/97, phase 2 1998/99, phase 3 1999/2000. SETTING: Central Coast, New South Wales. PARTICIPANTS: Phase 1--all general practices on the Central Coast. Phases 2 and 3--samples of practices. INTERVENTIONS: Each practice was surveyed about how they stored vaccines. A datalogger recorded fridge temperatures over six days. Individual feedback and advice were given. MAIN OUTCOME MEASURES: Proportion of: 1. fridges maintaining a temperature in the 2-8 degrees C range; 2. fridges freezing; 3. practices with one person responsible for vaccine storage; 4. bridge temperature checked daily; 5. fridges storing no items other than vaccines; 6. bridges with thermometers; and 7. associations between storage practices and fridge temperatures. RESULTS: In phase 1, 102 fridges, and in phase 3, a random sample of 36 practices was surveyed. The findings for phase 1 and phase 3 respectively were: 31% and 50% of fridges were in the 2-8 degrees C range; 36% and 25% were <0 degrees C; one person was responsible in 52% and 53% of cases; 20% and 38% reported daily checks; 74% and 94% of fridges had no extraneous items and 53% and 86% of fridges had thermometers. No statistically significant associations were found between vaccine storage practices and bridge temperatures. CONCLUSIONS: Despite improvements in vaccine storage practices, a quarter of fridges were freezing, thereby compromising the potency of many of the immunisation schedule vaccines.

Drug Storage↗
PubMed2000

Does treatment of acute herpes zoster prevent or shorten postherpetic neuralgia?

OBJECTIVE: Our goal was to determine if any treatment of acute herpes zoster alters the incidence or duration of postherpetic neuralgia (PHN), a common sequela in elderly patients. SEARCH STRATEGY: We systematically searched MEDLINE and The Cochrane Library. We also examined the reference lists of identified trials and reviews. SELECTION CRITERIA: We included all randomized controlled trials of treatments of zoster published in English that included assessment of pain at any time after rash healing. DATA COLLECTION/ANALYSIS: Forty-two trials met inclusion criteria, and 2 reviewers independently evaluated them for methodologic quality and the statistical and clinical significance of results. MAIN RESULTS: Four placebo-controlled trials of oral acyclovir with 692 patients provided marginal evidence for reduction in pain incidence at 1 to 3 months following zoster onset. Famciclovir significantly reduced duration but not incidence of PHN in one placebo-controlled trial of 419 patients. Valacyclovir significantly reduced duration but not incidence of PHN in one acyclovir-controlled trial of 1141 patients. Steroids had no effect on PHN. Amitriptyline for 90 days reduced pain incidence at 6 months in one placebo-controlled trial of 80 patients. A single trial of percutaneous electrical nerve stimulation (PENS) in 50 patients suggested a decrease in pain incidence at 3 and 6 months compared with famciclovir. CONCLUSIONS: There is limited evidence that current interventions prevent or shorten PHN. Famciclovir and valacyclovir have been shown to reduce the duration of PHN in single published trials. Well-designed and larger trials of amitriptyline and PENS should be conducted.

Acute Disease↗
PubMed1999

Topical therapies for glaucoma: what family physicians need to know.

Medication classes historically used in the management of glaucoma include beta blockers, miotics, sympathomimetics and carbonic anhydrase inhibitors. Because topically applied medications are more site specific, they are preferred in the treatment of glaucoma. Compared with oral medications, topical agents are associated with a decreased incidence of systemic side effects. With topical administration, conjunctival and localized skin allergic reactions are relatively common, whereas severe reactions, including death, are rare. Recently introduced topical agents for glaucoma therapy include dorzolamide and brinzolamide, the first topical carbonic anhydrase inhibitors; brimonidine and apraclonidine, more ocular-specific alpha agonists; and latanoprost, a prostaglandin analog, which is a new class of glaucoma medication. Latanoprost has the unique side effect of increasing iris pigmentation. Like their predecessors, the newer agents lower intraocular pressure by a statistically significant degree. Preservation of visual field, the more substantial patient-oriented end point, continues to be studied.

Adrenergic beta-Antagonists↗
PubMed1998

Outdoor air pollution and children's respiratory symptoms in the steel cities of New South Wales.

OBJECTIVE: To investigate the relationship between outdoor air pollution and the respiratory health of children aged 8 to 10 years. DESIGN: A cross-sectional survey (between October 1993 and December 1993) of children's health and home environment. Summary measures of particulate pollution (levels of particles with an aerodynamic diameter less than 10 microns [PM10] each 6th day) and SO2 (daily mean and maximum hourly values) were estimated for each area (using air quality monitoring station data from July 1993 to June 1994). SETTING AND SURVEY PARTICIPANTS: Parents of 3023 primary school children (Years 3, 4 and 5) from industrial and non-industrial areas with air quality monitoring stations in the Hunter and Illawarra regions of New South Wales. MAIN OUTCOME MEASURES: Reported occurrence of four or more chest colds, four or more attacks of wheezing, and night-time cough without a cold for more than two weeks, all within the previous 12 months. RESULTS: 77% response rate, ranging by area from 66% to 88%. The average annual outdoor air pollution for the nine areas was 18.6-43.7 micrograms/m3 for PM10 and 0.16-0.90 parts per hundred million for SO2. The proportion of children reported to have the main outcome symptoms were: chest colds, 3.0%-9.7%; night cough, 12.3%-30.5%; and wheeze, 3.4%-11.3%. There was no significant association with SO2, but a significant increase in the odds of symptoms per 10 micrograms/m3 increase in PM10 on chest colds (odds ratio [OR], 1.43; 95% confidence interval [CI], 1.12-1.82) and night-time cough (OR, 1.34; 95% CI, 1.19-1.53), but not wheeze. Passive smoking was significantly associated with chest colds but not with the other symptoms. Maternal allergy was associated with all three respiratory symptoms, most strongly with wheeze. CONCLUSION: These results provide evidence of health effects at lower than expected levels of outdoor air pollution in the Australian setting. They also suggest differences in contributions of environmental and hereditary factors to cough and chest colds compared with wheeze.

Air Pollution↗
PubMed1998

Vaccine storage in pharmacies on the Central Coast of New South Wales.

Pharmacies on the Central Coast of NSW were surveyed to assess the ability of refrigerators used for vaccine storage to maintain the recommended temperature range (2 to 8 degrees C). Refrigerators used for vaccine storage were monitored over a 3-day period using a temperature data logger. Fifty-nine (59) retail pharmacies were identified. The response rate was 90% (53/59) and 52 refrigerators were monitored successfully. Only 10 (19%) of the refrigerators maintained temperatures wholly within the recommended range for the 3-day monitoring period. The remaining refrigerators were considered in three groups--refrigerators keeping temperatures in the range 0.1 to 11.9 degrees C, below 0 degree C and above 8 degrees C for most of the time. There were 15 (29%), 12 (23%) and 15 (29%) refrigerators in these groups respectively keeping temperatures in the recommended range for 91%, 19% and 30% of the time. Of the refrigerators achieving temperatures below 0 degree C, none went below -5 degrees C and on average they kept temperatures less than 0 degree C for 49% of the time. This survey highlights the need for vigilance in vaccine storage for immunisation programs to be successful. Of the vaccines affected by freezing, hepatitis B vaccine was identified as being most at risk.

Data Collection↗
PubMed1994

Heat exhaustion in The Sun-Herald City to Surf fun run.

OBJECTIVE: To investigate the relationship between motivational factors and physical and biological causes of heat exhaustion in fun run entrants. DESIGN AND SETTING: Case-control study, The Sun-Herald City to Surf fun runs in Sydney in 1991 and 1992. PARTICIPANTS: There were 63,732 race entrants who completed the run and received a finishing time; 79 runners with heat exhaustion and 310 age, sex and performance matched controls were enrolled in the study. MAIN OUTCOME MEASURE: A diagnosis of heat exhaustion was made if a runner collapsed and, when first receiving medical care, had a rectal temperature of 38 degrees C or higher. RESULTS: Two readily identifiable groups of runners were at high risk of heat exhaustion--accomplished non-élite (preferred) runners and runners of good ability (Group A). The attack rate was highest among accomplished non-élite runners, but a combination of a relatively high rate and the large number of entrants in Group A runners accounted for most cases. Four major risk factors for heat exhaustion were identified: motivation to exceed previous performance targets; failure to drink fluids during the run; failure of trained runners to acclimatise for the race by training in the warmer parts of the day; and previous history of heat exhaustion. CONCLUSION: Information from this investigation will enable more effective targeting of educational prevention programs in The Sun-Herald City to Surf fun run and provide baseline data for monitoring the effectiveness of these programs to modify high risk behaviour by participants.

Adolescent↗
PubMed1992

Effect of myelination on the conduction velocity of optic nerve fibres.

It was proposed by Rushton in 1951, from theoretical considerations, that myelinated fibres less than 1 micron in diameter would conduct more slowly than unmyelinated fibres of the same size and that myelinated fibres below about 0.7 micron would not conduct at all. The experimental data on which he based his theory are all from the peripheral nervous system where small myelinated fibres are rare, and no experimental verification of Rushton's hypothesis has been attempted. In mammalian optic nerve, nearly all the fibres are myelinated; yet half have diameters below 1 micron, with many below 0.7 micron. The many studies of conduction velocities in the visual system enable a test of Rushton's hypothesis to be made. We have examined the correlations between conduction velocity and fibre diameter from a wide range of published studies of the mammalian visual system. The results of our analysis suggest that the small myelinated fibres of the optic nerve and optic tract conduct action potentials more rapidly than is predicted by Rushton's hypothesis, while the unmyelinated axons within the retina actually conduct more slowly than predicted. There is no reason to believe, in this case, that myelination of a small axon will reduce its conduction velocity.

Action Potentials↗
PubMed1991

Contraceptive effects of extended lactational amenorrhoea: beyond the Bellagio Consensus.

We have recorded the duration of lactational anovulation and amenorrhoea in a well-nourished group of Australian women who breastfed their babies throughout the study. The data enabled us to compare the theoretical cumulative probability of conception among breastfeeding women who had unprotected intercourse irrespective of their menstrual status with that of those who had unprotected intercourse only during lactational amenorrhoea. Breastfeeding alone is not an effective form of contraception, since all the women in our study resumed normal ovulation while still breastfeeding. However, among women who have unprotected intercourse only during lactational amenorrhoea but adopt other contraceptive measures when they resume menstruation, only 1.7% would have become pregnant during the first 6 months of amenorrhoea, only 7% after 12 months, and only 13% after 24 months. Thus for our women it would be possible to extend the Bellagio Consensus Conference guidelines which stated that lactational amenorrhoea can only be relied on as a contraceptive for the first 6 months post-partum in women who are fully or almost fully breastfeeding. The lactational amenorrhoea method can be relied on for excellent contraceptive protection in the first 6 months of breastfeeding, irrespective of when supplements are introduced into the baby's diet; for women who continue to breastfeed the method can also give good protection for up to 12 months post partum. Once menstruation has returned, other forms of contraception are essential to prevent pregnancy.

Amenorrhea↗
PubMed1991

The resumption of ovulation and menstruation in a well-nourished population of women breastfeeding for an extended period of time.

We have studied a large group of Australian women breastfeeding for an extended period of time to determine the duration of lactational anovulation (n = 89) and amenorrhea (n = 101). Salivary progesterone assays were used to determine ovulation. These women had a mean of 322 days of anovulation and 289 days amenorrhea. Less than 20% had ovulated and less than 25% had menstruated by 6 months postpartum. The latest ovulation was at 750 days and the latest menstruation at 698 days. There was no significant correlation between any measure of maternal nutritional status and the duration of anovulation or amenorrhea. Neither the time of first supplement introduction to the baby nor the amount of supplement given was an accurate predictor of the return of ovulation or menstruation. However, our results clearly show that lactational amenorrhea can provide good protection against pregnancy in the 1st 6 months postpartum, even in well-nourished women who are giving their babies supplemental feeds.

Adult↗
PubMed1987

Vaccination against lumpy jaw and measurement of antibody response in wallabies (Macropus eugenii).

Successful protection against lumpy jaw disease in a colony of captive wallabies (Macropus eugenii) was induced by vaccination with a commercial ovine footrot vaccine. No mortalities attributable to lumpy jaw were observed in 69 vaccinated animals while six of 42 unvaccinated control wallabies died of the disease. Vaccinated animals exhibited significant increases in antibody titres to Bacteroides nodosus after the first and second doses of vaccine. Titres were measured by an enzyme-linked immunosorbent assay.

Animals↗
PubMed1987

The characterization of the mutagenic activity of soil.

The solvent extracts of non-agricultural soil were shown to cause a potent mutagenic response to Salmonella bacteria. The extract of soil from local sites had activities of 100,000-250,000 TA98 revertants per kg with S9 activation and 44,000-83,000 revertants per kg to TA100 with activation. The soil is mutagenic to both strains without S9, but at lower levels. Nitroreductase-deficient bacterial strains show that the soil extract may have mutagenic compound(s) containing a nitro group. The revertant numbers per gram of soil are lowest at the surface, increase at 4-10 cm and decrease in a linear fashion to a depth of 0.5 meter. HPLC fractionation shows that there is more than one separable component responsible for the mutagenicity of the soil. The source and consequences of the high levels of mutagenicity in 'ordinary soil' are unknown. Soil mutagens can be a significant complicating factor to those using the Ames/Salmonella assay for environmental sampling.

California↗
PubMed1987

Salivary oestriol and progesterone concentrations in women during late pregnancy, parturition and the puerperium.

Oestriol and progesterone concentrations were measured by specific radioimmunoassays in the saliva of six women on a daily basis during the last month of pregnancy, at frequent intervals during labour and daily during the puerperium. Salivary steroid concentrations are thought to reflect the circulating concentrations of the free hormone, and hence may be more biologically relevant than the total plasma concentration, or the urinary excretion of a metabolite. There was no sign of a fall in salivary oestriol or progesterone concentrations before the onset of labour. During the first and second stages, the concentrations fluctuated widely, perhaps due to alterations in uterine blood flow. After delivery of the placenta, hormone concentrations declined abruptly. Oestriol reached undetectable levels of less than 0.1 nmol/l within a day, whereas progesterone concentrations declined somewhat more slowly, approaching follicular-phase values after 2-3 days. This slower decline in the concentration of progesterone may be due to a leaching-out of the hormone from body fat stores. The absence of any prepartum progesterone withdrawal presumably explains the characteristic postpartum delay in the onset of lactogenesis.

Adult↗
PubMed1986

The isolation and identification of a new mutagen from fried ground beef: 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP).

A new mutagenic compound has been isolated from ground beef which was fried at 300 degrees C for 5.5 min on each side. The new mutagen was purified using an aqueous acid extraction, XAD-2 adsorption-solvent elution, a series of preparative and analytical h.p.l.c. purification steps, and monitored with the Ames/Salmonella assay. This study reveals a new mutagen member of the amino-imidazoazaarene class of aromatic amines, having a mol. w of 224, and a formula of C13H12N4 as determined by high-resolution mass spectrometry. N.m.r. spectrometry supports the structure, 2-amino-1-methyl-6-phenyl-imidazo[4,5-b]pyridine (PhIP), for the new mutagen. The 1-methyl and 3-methyl synthesized isomers of PhIP were compared to the purified mutagen. The two isomers had identical mass spectra to the purified compound, but only the 1-methyl isomer showed similar u.v. and n.m.r. spectra. The two synthetic isomers were separable by h.p.l.c. and the beef derived component co-eluted with the 1-methyl-PhIP isomer. PhIP has a specific activity in the Ames/Salmonella assay of 1950 revertants/microgram. Although it is not as mutagenic as other compounds isolated from fried beef (e.g. MeIQx, 58 000 revertants/microgram) it is the most abundant mutagenic compound by mass in fried beef. PhIP is present at approximately 15 p.p.b. of the original weight of uncooked beef (accounting for 75% of the mass of genotoxic material) and contributes 18% of the total mutagenicity of the fried beef.

Animals↗
PubMed1986

Prostaglandin in the peripheral plasma of tammar wallabies during parturition.

Tammar wallabies (Macropus eugenii) were observed for 7 days, 24 h/day, at the expected time of birth in two consecutive breeding seasons. Blood was collected from the lateral tail vein 1-2 days before birth, then at 10- to 20-min intervals in the peripartum period and less frequently to 30-h post partum. Plasma was assayed for the prostaglandin metabolite 13,14-dihydro-15-oxo-prostaglandin F2 alpha (PGFM), progesterone and LH. An assay for PGFM was validated which allows direct measurement in 100 microliter unextracted plasma with a sensitivity of 0.14 nmol/l (50 pg/ml). There was a short-lived peak of PGFM immediately before or at birth (7.15 +/- 2.52 nmol/l; 2536 +/- 892 pg/ml) which declined to less than 0.28 nmol/l (100 pg/ml) within 2-h post partum. Progesterone concentrations declined about the time of birth, coincident with the peak of PGFM, and reached levels observed in lactationally quiescent animals by 16-h post partum, which was also the time of the LH peak. The transient prostaglandin pulse was detected only by frequent sampling and suggests that, as in other mammals, prostaglandin is important in parturition.

Animals↗
PubMed1985

Effects of temperature, patty thickness and fat content on the production of mutagens in fried ground beef.

The high-pressure liquid chromatography (HPLC) profiles of mutagenic components were compared for extracts of ground beef patties fried at 200, 250 and 300 degrees C for 6 min/side. The HPLC profiles of the mutagenic samples were similar, although total mutagenic activity in Salmonella typhimurium TA1538 was roughly four times as high after the 300 degrees C than after the 200 degrees C frying. Six mutagenic peaks were analysed quantitatively at different temperatures and meat thicknesses. Two major components, 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline and 2-aminotrimethylimidazo[4,5-f]quinoxaline, and a minor component, 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), were all present at the three different temperatures. Thus, in general, cooking temperature seems to have a major effect on the quantities of mutagens produced but not on their HPLC profiles. The thickness of the meat patty did not affect the total yield of mutagens except at longer cooking times (8-10 min/side) and, in general, neither did it affect the HPLC profiles of the mutagenic components. Total mutagenic activity increased with increasing cooking times. Increasing the fat content lowered the total mutagenicity, with 150,000 revertants/kg of fresh beef at 30% fat compared with 230,000 revertants/kg at 15%, but had little effect on the mutagenicity due to IQ.

Animals↗