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Biomedical subjects

P A O'Brien

Publications and source records attributed to P A O'Brien.

At least 19 recordsLinked to original sources
PubMed2006

Nitrogen dynamics in an Australian semiarid grassland soil.

We conducted a four-week laboratory incubation of soil from a Themeda triandra Forsskal grassland to clarify mechanisms of nitrogen (N) cycling processes in relation to carbon (C) and N availability in a hot, semiarid environment. Variation in soil C and N availability was achieved by collecting soil from either under tussocks or the bare soil between tussocks, and by amending soil with Themeda litter. We measured N cycling by monitoring: dissolved organic nitrogen (DON), ammonium (NH4+), and nitrate (NO3-) contents, gross rates of N mineralization and microbial re-mineralization, NH4+ and NO3- immobilization, and autotrophic and heterotrophic nitrification. We monitored C availability by measuring cumulative soil respiration and dissolved organic C (DOC). Litter-amended soil had cumulative respiration that was eightfold greater than non-amended soil (2000 compared with 250 microg C/g soil) and almost twice the DOC content (54 compared with 28 microg C/g soil). However, litter-amended soils had only half as much DON accumulation as non-amended soils (9 compared with 17 microg N/g soil) and lower gross N rates (1-4 compared with 13-26 microg N x [g soil](-1) x d(-1)) and NO3- accumulation (0.5 compared with 22 microg N/g soil). Unamended soil from under tussocks had almost twice the soil respiration as soil from between tussocks (300 compared with 175 microg C/g soil), and greater DOC content (33 compared with 24 microg C/g soil). However, unamended soil from under tussocks had lower gross N rates (3-20 compared with 17-31 microg N x [g soil](-1) d(-1)) and NO3- accumulation (18 compared with 25 microg N/g soil) relative to soil from between tussocks. We conclude that N cycling in this grassland is mediated by both C and N limitations that arise from the patchiness of tussocks and seasonal variability in Themeda litterfall. Heterotrophic nitrification rate explained >50% of total nitrification, but this percentage was not affected by proximity to tussocks or litter amendment. A conceptual model that considers DON as central to N cycling processes provided a useful initial framework to explain results of our study. However, to fully explain N cycling in this semiarid grassland soil, the production of NO3- from organic N sources must be included in this model.

Carbon↗
PubMed2005

Frameless versus classical intrauterine device for contraception.

BACKGROUND: The frameless intrauterine device (IUD) dispenses with the frame in the classical IUD and holds the device in the uterus by anchoring one end of a nylon thread in the fundal myometrium, to which copper sleeves are attached. OBJECTIVES: This review examines the hypothesis that the frameless IUD Gynefix reduces risk of expulsion and pregnancy, and the problems of bleeding and pain necessitating early removal. SEARCH STRATEGY: We searched the Cochrane Controlled Trial Register (Cochrane Library Issue 2, 2004), MEDLINE, and Popline from 1980 to March 2004, and reference list of articles. SELECTION CRITERIA: We selected for the review randomised trials that compared the frameless device to a classical framed device for contraception. DATA COLLECTION AND ANALYSIS: Both authors extracted data independently. We contacted study author for additional data. We calculated rate ratios and rate differences for cumulative rates for each outcome at yearly intervals. We used the inverse variance-based method to combine trials, and tested the results for heterogeneity. MAIN RESULTS: Four trials were included in the review involving 5,939 women randomised to either a frameless device or TCu380, with data up to eight years for the largest, and with a total experience of 23,180 years. Apart from one small trial, nulliparous women were excluded from the trials. The two earlier trials used a prototype introducer and there was a higher expulsion rate at one year (relative risk 2.48, 95% confidence intervals 1.89 to 3.26). However, between two and six years in the large WHO trial the risk of pregnancy was lower with the frameless device (relative risk 0.53, 95% confidence intervals 0.32 to 0.91). In a recent trial using GyneFix with a new introducer early expulsions and pregnancies were not statistically different from the control device. Removals rates for excessive bleeding and/or pain were no different between the devices (relative risks 0.92, 95% confidence intervals 0.74 to 1.14, at one year and 1.13, 0.93 to 1.37, at six years). There was a tendency towards fewer removals for pain in early years but no difference at six years (relative risk 1.13, 95% confidence intervals 0.93 to 1.37). AUTHORS' CONCLUSIONS: There is insufficient data to show that problems of early expulsions have been overcome with the modified introducer used in GyneFix. Apart from that, the frameless device performs similarly to TCu380, and appears to have a lower pregnancy rate in later years, although the absolute difference is small.

Contraception↗
PubMed2002

Are Sebacinaceae common and widespread ectomycorrhizal associates of Eucalyptus species in Australian forests?

A molecular survey of basidiomycete ectomycorrhizal fungi colonising root tips at a site in Eucalyptus marginata (jarrah) forest revealed the presence of many fungal species which could not be identified from a database of ITS-PCR-RFLP profiles from morphologically identified species. Three of these unidentified taxa were among the six most frequently encountered profiles. Phylogenetic analyses of ITS and nuclear LSU sequences revealed a close relationship among the three fungi and that they belong to the family Sebacinaceae (sensu Weiss and Oberwinkler 2001). The possibility that DNA of non-ectomycorrhizal rhizosphere or endophytic fungi had been amplified selectively by the basidiomycete-specific primers was tested by amplification with fungal-specific primers. A single PCR fragment was amplified in all but two of the 24 samples tested and digestion with two restriction enzymes produced RFLP profiles which matched those from the Sebacinoid sequence. We conclude, therefore, that at least three species of Sebacinaceae are common ectomycorrhizal associates of E. marginata.

Australia↗
PubMed2001

Frameless versus classical intrauterine device for contraception.

BACKGROUND: The frameless intrauterine device (IUD) dispenses with the frame in the classical IUD and holds the device in the uterus by anchoring one end of a nylon thread in the fundal myometrium, to which copper sleeves are attached. The introducer for the frameless device was modified following reports of early expulsions of the device. OBJECTIVES: This review examines the hypothesis that the frameless device reduces risk of expulsion and pregnancy, and the problems of bleeding and pain necessitating early removal. SEARCH STRATEGY: We searched the Cochrane Controlled Trial Register (Cochrane Library Issue 1, 2001), MEDLINE, EMBASE and Popline to Dec 2000, and reference list of articles. SELECTION CRITERIA: We selected for the review randomised trials that compared the frameless device to a classical framed device for contraception. DATA COLLECTION AND ANALYSIS: Both authors extracted data independently. We contacted study author for additional data. We calculated rate ratios and rate differences for cumulative rates for each outcome at yearly intervals. We used the general variance-based method to combine trials, and tested the results for heterogeneity. MAIN RESULTS: Three trials were included in the review involving over 5,800 women randomised to either a frameless device or TCu380A, with data up to eight years for the largest, and with a total experience of 23,000 women-years. All three trials excluded nulliparous women. The two earlier trials used a prototype introducer and there was a higher expulsion rate at one year (relative risk 2.48, 95% confidence intervals 1.89 to 3.26). However, between two and six years in the large WHO trial the risk of pregnancy was lower with the frameless device (relative risk 0.53, 95% confidence intervals 0.32 to 0.91). In a recent trial using GyneFix with a new introducer early expulsions and pregnancies were not statistically different from the control device; by the third year the expulsion rate with the frameless device was lower (relative risk 0.41, 95% confidence intervals 0.19 to 0.87) with no difference in pregnancy rate. Removals rates for excessive bleeding and/or pain were no different between the devices (relative risks 0.92, 95% confidence intervals 0.74 to 1.14, at one year and 1.13, 0.93 to 1.37, at six years). There was a tendency towards fewer removals for pain in early years but no difference at six years (relative risk 1.13, 95% confidence intervals 0.93 to 1.37). REVIEWER'S CONCLUSIONS: There are insufficient data to show that problems of early expulsions have been overcome with the new introducer used in GyneFix. Apart from that, the frameless device performs similarly to TCu380A, and appears to have a lower pregnancy rate in later years, although the absolute difference is small.

Contraception↗
PubMed1998

Microsatellites in the mitochondrial genome of phytophthora cinnamomi failed to provide highly polymorphic markers for population genetics.

Microsatellites were evaluated as genetic markers for the mitochondrial genome (mtDNA) of Phytophthora cinnamomi for population studies. Two (A)n microsatellite loci were cloned from the mtDNA of P. cinnamomi. Amplification products from these loci showed little polymorphism among Phytophthora isolates due to their location in coding regions of mtDNA. A further three (A)n microsatellite loci obtained from the complete mtDNA sequence of P. infestans were also not highly polymorphic, although located in non-coding mtDNA. The presence of the (A)n microsatellites was not conserved in the genus Phytophthora. Unlike those of the chloroplast genome of plants, (A)n microsatellite loci of mtDNA do not have potential as highly polymorphic markers in Phytophthora.

Base Sequence↗
PubMed1996

Patellar tendinosis (jumper's knee): findings at histopathologic examination, US, and MR imaging. Victorian Institute of Sport Tendon Study Group.

PURPOSE: To determine the histopathologic findings of patellar tendinosis ("jumper's knee") demonstrated with ultrasonography (US) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: Twenty-four athletes (28 knees) with jumper's knee (23 men, one women; mean age, 30.9 years) scheduled to undergo open tenotomy underwent US patellar tendon examination. Seventeen patients (19 knees) also underwent MR imaging. Tissue was obtained for histopathologic examination in all 28 cases. Eleven age-, height-, and weight-matched athletes (22 knees) without previous knee symptoms served as control subjects for the US examination. Control material for histopathologic examination was obtained in 20 cadavers (39 knees). Data were analyzed with standard statistical methods. RESULTS: MR imaging and US both revealed an abnormal zone at the proximal patellar tendon attachment. Histopathologic examination revealed mucoid degeneration in all tendons in patients and in 8% (three of 39) of tendons in cadavers (P < .01). CONCLUSION: Jumper's knee is characterized by consistent changes at MR imaging, US, and histopathologic examination and is appropriately described as patellar tendinosis.

Adult↗
PubMed1995

Molecular characterization of Cryptosporidium isolates from humans and other animals using random amplified polymorphic DNA analysis.

Genetic variation in 25 Cryptosporidium isolates was analyzed using the random amplified polymorphic DNA (RAPD) technique. Simple reproducible polymorphisms were generated (using five primers) from Cryptosporidium DNA that was free of contaminating bacterial DNA. The results generated by four of the five primers were statistically correlated (P < 0.001). The combined data from three primers were used to construct a phenogram using Jaccard's distance. Four groupings could be distinguished. Two C. serpentis isolates from snakes formed a distinct group of their own, whereas C. parvum isolates were divided into two main groups: one containing most human isolates and the other containing mostly domestic animals plus two remaining human isolates. Due to the sensitivity of the RAPD technique, isolates can now be analyzed genetically, directly from fecal samples without further biological amplification. This represents a significant advance on current techniques.

Animals↗
PubMed1994

Stimulation of synthesis and release of swainosonine from transformed roots of Swainsona galegifolia.

Transformed root cultures of Swainsona galegifolia were established for swainsonine production. Stimulation of production of swainsonine and its release into the culture medium was achieved using copper sulphate, reduction of medium pH and supply of swainsonine precursors. The yield of control cultures (0.3 g of roots grown in 15 ml medium for 30 days) was 79 micrograms swainsonine with only a trace of swainsonine in the medium. After treatment with 1 mM copper sulphate for two days before harvest on day 30, 155 micrograms of swainsonine was produced, of which 14.3 micrograms was in the medium. Reduction of medium pH from 5.7 to 2.7 for one day before harvest resulted in 159 micrograms of swainsonine (47 micrograms in the medium). Supplementation with 2 mM malonic acid for 12 days before harvest resulted in 187 micrograms total swainsonine (34 micrograms in the medium), while 2 mM pipecolic acid for six days before harvest gave the highest swainsonine yield (220 micrograms total, 43 micrograms in the medium). The increased yields were achieved through small increases in biomass, as well as increases in the level of swainsonine synthesis.

Copper↗
PubMed1993

Use of RAPD-PCR to isolate a species specific DNA probe for Phytophthora cinnamomi.

The products of RAPD-PCR amplification of Phytophthora cinnamomi DNA were separated by electrophoresis in agarose. Parallel Southern blots of the gels were hybridized with nick translated DNA from different species of Phytophthora. Fragments that hybridized specifically to P. cinnamomi DNA were identified. These fragments were purified and cloned into pUC18. Their specificity for P. cinnamomi was confirmed.

Base Sequence↗
PubMed1993

Clinical associations of an increased transthyretin band in routine serum and urine protein electrophoresis.

The 9697 electrophoretograms performed over an 8 year period were reviewed to identify the frequency and clinical associations of the finding of a prominent transthyretin band in serum or urine, the concentration of which was equal to or greater than a 64 mg/dL protein calibrator. All samples were electrophoresed at a constant 90 V using agarose gels with a barbital buffer pH 8.6 and Ponceau S staining. Reference calibrators were used as standards to identify increased transthyretin bands and the patients' clinical records were subsequently reviewed. High values were found in 46 patients' sera and a further nine patients' urines representing 0.57% of the total workload. Renal impairment was present in 58% of cases including those with chronic renal failure, the nephrotic syndrome and paraproteinaemia. The high levels were not persistent in three myeloma cases where there was a recovery in renal function following chemotherapy. In some nephrotics, a high urine transthyretin may be secondary to a general hepatic albumin and transport protein synthesis response to severe proteinuria. Why the serum transthyretin was elevated in many other cases remains unclear.

Adult↗
PubMed1987

Comparison of bepridil with nadolol for angina pectoris.

Bepridil hydrochloride is a unique calcium channel-blocking drug with anti-ischemic and type 1 antiarrhythmic properties. With a half-life of more than 40 hours, once-daily therapy is possible. Twenty-four patients (22 men, 2 women), mean age 58 years (range 43 to 72), with stable exertional angina were assigned to therapy with bepridil and nadolol in a randomized, double-blind, crossover trial. Antianginal efficacy was assessed by a diary of angina frequency and nitroglycerin consumption as well as by treadmill exercise testing. The effect of therapy on ventricular function was assessed by symptom-limited equilibrium gated exercise radionuclide angiography. During therapy with both nadolol and bepridil, the number of episodes of angina per week was significantly reduced and nitroglycerin consumption decreased compared with baseline evaluation. Exercise duration was prolonged by both therapies (baseline 281 +/- 122 seconds, nadolol 377 +/- 96 seconds, bepridil 400 +/- 109 seconds; p less than 0.005 for nadolol and bepridil vs baseline). Time to the onset of angina was similarly prolonged, 50% by nadolol and 65% by bepridil (p less than 0.005). Bepridil had no effect on PR and QRS durations, although QTc was significantly prolonged (baseline 0.43 +/- 0.03, nadolol 0.42 +/- 0.03, bepridil 0.45 +/- 0.04; p less than 0.005 for bepridil vs baseline and nadolol). By radionuclide angiography, neither nadolol nor bepridil had an adverse effect on left ventricular function at rest or during exercise. Bepridil therefore provides effective therapy for angina without adverse effects on left ventricular function, comparable to the effects of beta blockade with nadolol.

Adult↗