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Biomedical subjects

M A Palmer

Publications and source records attributed to M A Palmer.

At least 19 recordsLinked to original sources
PubMed2006

Stream insect occupancy-frequency patterns and metapopulation structure.

An understanding of the distribution patterns of organisms and the underlying factors is a fundamental goal of ecology. One commonly applied approach to visualize these is the analysis of occupancy-frequency patterns. We used data sets describing stream insect distributions from different regions of North America to analyze occupancy-frequency patterns and assess the effects of spatial scale, sampling intensity, and taxonomic resolution on these patterns. Distributions were dominated by satellite taxa (those occurring in or=90% of sites) determined the overall modality of occupancy-frequency patterns. The proportions of satellite taxa increased with spatial scale and showed positive relationships with sampling intensity (r2=0.74-0.96). Furthermore, analyses of data sets from New York (USA) showed that generic-level assessments underestimated the satellite class and occasionally shifted occupancy-frequency distributions from unimodal to bimodal. Our results indicate that, regardless of species- or generic-level taxonomy, stream insect communities are characterized by satellite species and that the proportion of satellite species increases with spatial scale and sampling intensity. Thus, niche-based models of occupancy-frequency patterns better characterize stream insect communities than metapopulation models such as the core-satellite species hypothesis.

Animals↗
PubMed2001

Eradication of ovine footrot by repeated daily footbathing in a solution of zinc sulphate with surfactant.

OBJECTIVE: To investigate the effect on ovine footrot of repeated daily footbathing in a solution of zinc sulphate with surfactant. DESIGN: Merino sheep were allocated to control and treatment groups of 119 sheep each at week 0. The sheep had a history of S1, U1, T and/or U6 types of Dichelobacter nodosus in interdigital and underrunning footrot lesions. Feet were not pared prior to treatment. PROCEDURE: Treatment sheep were footbathed in a 15 to 18% (w/v) solution of zinc sulphate with surfactant for 10 min on five consecutive days during week 1. At week 2, and fortnightly to week 52, all feet were inspected, lesion scores were recorded and samples were taken for laboratory tests. At week 53, all feet with no lesions at week 52, but with underrunning lesions prior to week 1, were pared and samples were taken. RESULTS: After footbathing, there were no lesions in any treatment sheep at any inspection to week 52. The percentage of feet of control sheep with lesions increased from 9% (391 of 4,284) between weeks 20 and 36, to 14% (593 of 4,284) between weeks 36 and 52. Ninety-five of 96 control sheep with no lesions at week 20 were still asymptomatic at week 52. D nodosus was not isolated from samples taken from 99 and 87 pared feet of treatment and control sheep, respectively. CONCLUSION: Repeated daily footbathing combined with prolonged exposure to a dry environment eradicated footrot in sheep with both interdigital and underrunning lesions in feet that were not pared prior to treatment.

Animals↗
PubMed2000

Effects of environmental noise on computer-derived voice estimates from female speakers.

The purpose of this study was to examine the influence of noise on voice profile statistics from female samples. Six young adult females served as subjects. Five had normal voices; one had a pathological voice with accompanying bilateral vocal nodules. Each female subject was required to match a generated 235 Hz tone (+/- 2 Hz) while maintaining a constant output level of 70 dB SPL (+/- 5 dB). Data collected from a previous study involving a normal male subject were included for comparative purposes. Noise was generated from a personal computer fan which had a strong center frequency component at 235 Hz. Six different A-weighted signal-to-noise [S/N(A)] conditions were created, ranging in 5 dB increments from 25 to 0 dB. Results revealed that fundamental frequency was reasonably resistant to the effects of noise and to the effects of the noisy (pathological) voice signal. Jitter and shimmer estimates generally increased as noise floors elevated. The greatest amount of measurement error was found for the pathological female voice when captured in the presence of environmental noise. Findings are discussed relative to clinical issues surrounding measurement error.

Adult↗
PubMed2000

Occurrence of different strains of Dichelobacter nodosus in new clinical lesions in sheep exposed to footrot associated with multi-strain infections.

OBJECTIVE: To investigate the occurrence of S1, U1 and T strains of Dichelobacter nodosus in new clinical lesions in sheep exposed to footrot associated with multi-strain infections. DESIGN: Seventy-seven donor sheep were grazed with 84 recipients for 33 weeks. The donor sheep were Merinos with a history of clinically virulent footrot associated with protease type S1, U1 and T strains of D nodosus that hybridised with gene sequences pJIR314B, pJIR318 and/or pB645-335. The recipient sheep were Merinos with no history of footrot. PROCEDURE: Each fortnight, all feet were examined, their lesion scores were recorded and samples of lesion material were taken for laboratory tests. RESULTS: Eighty-nine percent (299 of 336) of feet of recipient sheep developed new clinical lesions. S1, U1 and T strains of D nodosus were recovered from 58%, 22% and 18%, respectively, of these lesions at a ratio that remained constant during two apparent peaks in footrot transmission. Gene sequences homologous to pJIR314B and pB645-335 were detected in 56% (93 of 166) and 29% (48 of 166), respectively, of S1 strains of D nodosus at a ratio that was not constant during the experiment. CONCLUSIONS: S1 was the dominant protease type of D nodosus in new clinical lesions. The occurrence of S1 strains did not increase relative to U1 and T strains of D nodosus during the experiment. S1, U1 and T strains of D nodosus remained in equilibrium despite changes in environment, genetic types in the population of S1 strains, and host resistance to footrot.

Animals↗
PubMed1998

Severity and persistence of footrot in Merino sheep experimentally infected with a protease thermostable strain of Dichelobacter nodosus at five sites.

OBJECTIVE: To test the hypothesis that ovine footrot associated with a thermostable protease strain of Dichelobacter nodosus undergoes self cure or is sustained as an annually recurring disease, depending on the environment. DESIGN AND PROCEDURE: Forty Merino sheep from a single blood line were infected with a protease thermostable strain of D nodosus at each of five sites in Western Australia. Footrot lesions and microscopic evidence of D nodosus were recorded every fortnight for 2.5 years, supplemented by laboratory culture. Rainfall, soil and air temperature, pasture quantity and composition and soil types were also recorded. Flocks that apparently self cured were relocated to a more favourable site for footrot in the final spring season. RESULTS: The maximum prevalence of feet with clinical footrot lesions was 80.6, 1.3, 14.4, 3.8 and 88.1% at the five sites. Severe footrot occurred for three consecutive spring seasons at one site that had clay loam soil and at least 3500 kg/ha total pasture dry matter annually. However, the infection was asymptomatic for up to 10 weeks between outbreaks. D nodosus was isolated from flocks for 2.5 years at only two sites, although there was microscopic evidence of the organism at other sites in the final year. A thermolabile variant (strain U6) of D nodosus was isolated from the two sites where footrot persisted. CONCLUSION: Depending on time and location, ovine footrot induced by a protease thermostable strain of D nodosus either self cured or persisted as annual outbreaks interspersed with periods of asymptomatic infection.

Animals↗
PubMed1996

Comparison of gene probe and conventional methods for the differentiation of ovine footrot isolates of Dichelobacter nodosus.

In a collaborative study that involved four Australian veterinary diagnostic laboratories a gene probe test based on the recombinant plasmids pJIR318, pJIR314B, and pJIR313, which contain genomic vap or vrl regions, was compared with conventional tests used for the differential diagnosis of ovine footrot. A total of 771 clinical dichelobacter nodosus isolates were tested and designated as belonging to one of several gene probe categories. The results showed that 87% of the virulent isolates belonged to gene probe category 1, compared to only 6% of the benign isolates. It was concluded that there was good correlation between the gene probe test and the virulence designation of these isolates as well as the results of elastase, gelatin-gel and protease isoenzyme tests. Furthermore, the gene probe test was converted to a polymerase chain reaction (PCR)-based test. It is suggested that diagnostic laboratories consider carrying out both this PCR test and tests based on the extracellular proteases of D. nodosus.

Animals↗
PubMed1995

FGF suppresses apoptosis and induces differentiation of fibre cells in the mouse lens.

To determine whether fibroblast growth factor (FGF) has a role in lens development, we have generated transgenic mice expressing a dominant-negative form of the murine FGF receptor-1 (FGFRDN) in the lens. Using the fibre cell-specific alpha A-crystallin promoter to express the FGFRDN, we have asked whether FGF is required for fibre cell differentiation. The transgenic mice display diminished differentiation of fibre cells as indicated by their reduced elongation. In addition, transgenic lenses have an unusual refractile anomaly that morphological and biochemical data show results from the apoptosis of fibre cells in the central region of the lens. These results show that lens fibre cells are dependent on FGF for their survival and differentiation, and demonstrate that growth factor deprivation in vivo can lead to apoptosis.

Animals↗
PubMed1995

Seasonal characteristics of ragweed pollen dispersal in the United States.

BACKGROUND: The most definitive reports concerning the seasonal characteristics of ragweed (Ambrosia spp) pollen dispersal in the United States date back 60 years to work conducted with gravity slide samples. OBJECTIVE: Volumetric pollen data from 23 sampling sites were used to study the ragweed pollen season. METHODS: The date of first and final pollen capture and the date with maximum airborne pollen concentration (the "peak date") were used to compare the pollen seasons at locations ranging from approximately 30 degrees N to 45 degrees N latitude. RESULTS: Sixteen cities located north of 38 degrees N possessed similar peak dates (P = 1), generally achieving maximum airborne pollen concentration in late August or early September. Four cities located south of 38 degrees N experienced later peak dates, with the most southerly city reaching maximum pollen levels in mid-October. Three cities located in the Northwest did not recover ragweed pollen in air samples. CONCLUSION: This study confirms earlier reports and suggests what time of year source avoidance is most critical for ragweed sensitive individuals in various locations.

Allergens↗
PubMed1994

Simultaneous measurement of urethral opening pressure and urethral cross-sectional area during voiding cystometry.

OBJECTIVE: To assess a new technique for measuring urethral opening pressure and urethral cross-sectional area during the course of routine voiding cystometry. PATIENTS AND METHODS: Twenty-eight male patients were studied, 24 of whom had cystometric evidence of bladder outlet obstruction, the other four being unobstructed. Urethral opening pressure was measured using an adapted fluid bridge test and urethral cross-sectional area was measured using the method described in the preceding paper. RESULTS: The mean urethral opening pressure in the obstructed patients was 68 cm/H2O (range 38-124) against a mean of 19 cm/H2O (range 16-22) in the unobstructed group. The mean urethral cross-sectional area in the obstructed group was 2.6 mm2 (range 0.9-7.9) compared with a mean of 14.2 mm2 (range 10.8-19.9) in the unobstructed patients. CONCLUSION: This technique allows measurement of the parameters of bladder outlet obstruction described by Schäfer during routine voiding cystometry, without specialized equipment. This provides a simple method for quantification of urinary outflow obstruction and should prove useful in the assessment of new treatment modalities.

Adult↗
PubMed1994

Elimination of the influence of intravesical pressure on the micturitional urethral pressure profile by calculation of urethral cross-sectional area: an experimental study.

OBJECTIVE: To determine whether it is possible to eliminate the influence of intravesical pressure on the pressure drop recorded between the bladder and prostatic urethra during the micturitional urethral pressure profile (MUPP). MATERIALS AND METHODS: An experimental study using an artificial bladder/urethral model and computerized urethral pressure profile measurement system. RESULTS: By simultaneous measurement of the flow rate and MUPP it is possible to calculate a theoretical cross-sectional area, based on Griffiths' theory of flow through distensible tubes. The calculated cross-sectional area for a given constriction remains the same despite changes in the driving pressure. CONCLUSION: The effect of changes in intravesical pressure on the MUPP can be eliminated by calculation of the urethral cross-sectional area. This parameter forms part of the Schäfer model of obstruction and this technique may therefore be useful in quantifying bladder outlet obstruction.

Humans↗
PubMed1994

The laboratory culture of Dichelobacter nodosus in a footrot eradication program.

As part of a program to eradicate virulent footrot from Western Australia, 2745 isolates of Dichelobacter nodosus were isolated from 5263 specimens from 1883 submissions. The virulence of each isolate was assessed using protease thermostability and isoenzyme zymogram. We describe changes to the materials and methods required to handle these specimens and to reduce the interval between submission and report to 8 days.

Aerobiosis↗
PubMed1993

A gelatin test to detect activity and stability of proteases produced by Dichelobacter (Bacteroides) nodosus.

Previously reported tests to distinguish thermostable and thermolabile proteases of Dichelobacter nodosus used hide powder azure as a test substrate. This paper describes an alternative test for protease stability using gelatin, an inexpensive and convenient substrate. The test required less equipment and time than the hide powder tests, and simplified the testing of multiple samples. Proteases from 2965 isolates of D. nodosus from samples collected as part of a footrot eradication scheme were tested using the gelatin method, 1707 produced thermostable, and 1258 produced thermolabile protease. Production of thermostable protease was used to identify isolates of D. nodosus which had the potential to cause the virulent form of ovine footrot. Comparisons were made with a hide powder test on 47 isolates. Further characterisation of all proteases was undertaken using polyacrylamide gel electrophoresis. Isoenzyme patterns of thermostable protease producing isolates were identified as S1 (1688 isolates) and S2 (19) whilst thermolabile protease producing isolates showed patterns U1 (1104 isolates), U2 (40), U3 (32), U4 (47), U5 (6), U6 (28) and S1 (1).

Animals↗
PubMed1993

Routine estimation of prostate specific antigen prior to clinic attendance in patients with symptoms of bladder outlet obstruction.

We report the use of serum prostate specific antigen (PSA) estimations prior to clinic attendance in 234 patients referred with symptoms of bladder outlet obstruction to a general urology clinic. Ninety-three patients with PSA levels > 10 ng/ml were seen earlier than planned and offered transurethral resection or transrectal biopsy of the prostate gland. Forty-six patients (49%) proved to have carcinoma of the prostate, compared with 10 of 141 (7%) patients who had PSA values < 10 ng/ml. With a decision value of 10 ng/ml, the sensitivity for detecting carcinoma was 82% and specificity 73.5%. Using a decision value of 7 ng/ml improved the sensitivity to 95% without significantly affecting the specificity (70%). Twenty-four patients with prostatic cancer had bone metastases; the sensitivity of PSA for predicting a positive bone scan using a decision value of 25 ng/ml was 92%, but the specificity was only 31%.

Adult↗
PubMed1993

Quantification of bladder outlet obstruction by measurement of urethral opening pressure using an adapted fluid bridge test.

A new technique for measuring urethral opening pressure above the distal sphincter is described, based on the fluid bridge test. This test eliminates many of the inaccuracies produced when using standard pressure flow studies. Nineteen males were studied, 15 of whom had cystometric evidence of bladder outlet obstruction, the other 4 being unobstructed. The mean urethral opening pressure in the obstructed group was 69 cm H2O (range 44-124) and in the unobstructed group 19 cm H2O (range 16-22). The test is simple to perform and is not affected by muscular activity in the pelvic floor or the time lag between detrusor pressure and flow rate measurement.

Adult↗