Biomedical subjects

S McMahon

Publications and source records attributed to S McMahon.

At least 37 records · Page 2Linked to original sources

PubMed2003

Measurement of the B0-->J/psipi+pi- branching fraction.

We present a measurement of the branching fraction for the decay of the neutral B meson into the final state J/psipi(+)pi(-). The data set contains approximately 56 x 10(6) BB pairs produced at the Upsilon(4S) resonance and recorded with the BABAR detector at the PEP-II asymmetric-energy e(+)e(-) storage ring. The result of this analysis is B(B0-->J/psipi(+)pi(-))=(4.6+/-0.7+/-0.6) x 10(-5), where the first error is statistical and the second is systematic. In addition, we measure B(B0-->J/psirho(0))=(1.6+/-0.6+/-0.4) x 10(-5).

Journal Article↗

PubMed2003

Semaphorin 3C preserves survival and induces neuritogenesis of cerebellar granule neurons in culture.

Semaphorins (sema) constitute a family of molecules sharing a common extracellular domain (semaphorin domain). This family includes several types of secreted and membrane-associated molecules that are grouped into eight subclasses (subclasses 1-7 and viral semaphorins). Subclass 3 semaphorins are secreted molecules involved in axonal guidance, mainly through repulsive gradients and induction of growth cone collapse. More recently sema 3 molecules have been identified as positive factors in dependence of the type of neurons. Besides their axonal guidance function, some semaphorins have been implicated in apoptosis and survival. We investigated the effect of sema3C on survival and neurite outgrowth of rat cerebellar granule neurons (CGNs) in culture. 3T3 cells were stably transfected with sema3C. Several clonal lines were established and tested for their neuritogenic activity and one, S3C-8, was selected for the bulk of experiments. S3C-8 was co-cultured with CGNs. Sema3C enhanced CGN viability as assessed in co-cultures of CGNs with monolayers of S3C-8 in comparison with co-cultures of CGNs with control mock-transfected 3T3 cells. Moreover sema3C induced neuritogenesis of cultured CGNs, which express neuropilin-1 and -2. S3C-8 cells, overexpressing sema3C, were significantly more neuritogenic for CGN than poly l-lysine (PLL), a positive substrate for CGNs, as assessed by the measurement of the length of neurites and confirmed by Tau expression along the time of culture. CGNs co-cultured with S3C-8, showed up-regulation of the expression of axonal microtubule-associated proteins (MAPs) such as Tau, phosphorylated MAP2C and mode I-phosphorylated MAP1B compared with neurons cultured on control 3T3 cells. We also found increased expression of a specific marker of neuronal cell bodies and dendrites, high molecular weight MAP2 (HMW-MAP2). Interestingly, there was no accompanying up-regulation of a marker enriched within the neuronal somatodendritic domain, mode II-phosphorylated MAP1B. These data support the idea that secreted sema3C favors survival and neuritogenesis of cultured CGNs.

3T3 Cells↗

PubMed2002

Measurements of branching fractions and CP-violating asymmetries in B0-->pi+pi-, K+pi-, K+K- decays.

We present measurements of branching fractions and CP-violating asymmetries for two-body neutral B meson decays to charged pions and kaons based on a sample of about 88x10(6) Upsilon(4S)-->BB decays. From a time-independent fit we measure the charge-averaged branching fractions B(B0-->pi+pi-)=(4.7+/-0.6+/-0.2)x10(-6), B(B0-->K+pi-)=(17.9+/-0.9+/-0.7)x10(-6), and the direct CP-violating charge asymmetry A(Kpi)=-0.102+/-0.050+/-0.016 [-0.188,-0.016], where the ranges in square brackets indicate the 90% confidence intervals. From a time-dependent fit we measure the B0-->pi+pi- CP-violating parameters S(pipi)=0.02+/-0.34+/-0.05 [-0.54,+0.58] and C(pipi)=-0.30+/-0.25+/-0.04 [-0.72,+0.12].

Journal Article↗

PubMed2002

Measurement of the CP asymmetry amplitude sin2beta with B0 mesons.

We present results on time-dependent CP asymmetries in neutral B decays to several CP eigenstates. The measurements use a data sample of about 88 x 10(6) Upsilon(4S)-->B(-)B decays collected between 1999 and 2002 with the BABAR detector at the PEP-II asymmetric-energy B factory at SLAC. We study events in which one neutral B meson is fully reconstructed in a final state containing a charmonium meson and the other B meson is determined to be either a B(0) or B(-0) from its decay products. The amplitude of the CP asymmetry, which in the standard model is proportional to sin2beta, is derived from the decay-time distributions in such events. We measure sin2beta=0.741+/-0.067(stat)+/-0.034(syst) and |lambda|=0.948+/-0.051(stat)+/-0.030(syst). The magnitude of lambda is consistent with unity, in agreement with the standard model expectation of no direct CP violation in these modes.

Journal Article↗

PubMed2002

Measurement of the branching fraction and CP content for the decay B0-->D(+)D(-).

We report a measurement of the branching fraction of the decay B0-->D(*+)D(*-) and of the CP-odd component of its final state using the BABAR detector. With data corresponding to an integrated luminosity of 20.4 fb (-1) collected at the Upsilon(4S) resonance during 1999-2000, we have reconstructed 38 candidate signal events in the mode B0-->D(*+)D(*-) with an estimated background of 6.2+/-0.5 events. From these events, we determine the branching fraction to be B(B0-->D(*+)D(*-))=[8.3+/-1.6(stat)+/-1.2(syst)]x10(-4). The measured CP-odd fraction of the final state is 0.22+/-0.18(stat)+/-0.03(syst).

Journal Article↗

PubMed2002

Measurement of the B(0) lifetime with partially reconstructed B(0)-->D(-)l(+)nu(l) decays.

The B(0) lifetime was measured with a sample of 23 million BB pairs collected by the BABAR detector at the PEP-II e(+)e(-) storage ring during 1999 and 2000. Events from the semileptonic decay B(0)-->D(*-)l(+)nu(l) have been selected with a partial reconstruction method in which only the charged lepton and the slow pi from the D*--->D(0)pi(-) decay are reconstructed. The result is tau(B(0)) = 1.529+/-0.012(stat)+/-0.029(syst) ps.

Journal Article↗

PubMed2002

Search for the rare decays B-->Kl(+)l(-) and B-->K(*)l(+)l(-).

We present results from a search for the flavor-changing neutral current decays B-->Kl(+)l(-) and B-->K(*)l(+)l(-), where l(+)l(-) is either an e(+)e(-) or mu(+)mu(-) pair. The data sample comprises 22.7 x 10(6) Upsilon(4S)-->B(-)B decays collected with the BABAR detector at the PEP-II B Factory. We obtain the 90% C.L. upper limits B(B-->Kl(+)l(-))<0.51 x 10(-6) and B(B-->K(*)l(+)l(-))<3.1 x 10(-6), close to standard model predictions for these branching fractions. We have also obtained limits on the lepton-family-violating decays B-->Ke+/-mu(-/+) and B-->K(*)e(+/-)mu(-/+).

Journal Article↗

PubMed2002

Measurement of B0-B-0 flavor oscillations in hadronic B0 decays.

Flavor oscillations of neutral B mesons have been studied in e+e- annihilation data collected with the BABAR detector at center-of-mass energies near the upsilon(4S) resonance. The data sample used for this purpose consists of events in which one B0 meson is reconstructed in a hadronic decay mode, while the flavor of the recoiling B0 is determined with a tagging algorithm that exploits the correlation between the flavor of the heavy quark and the charges of its decay products. From the time development of the observed mixed and unmixed final states, we determine the B0-B-0 oscillation frequency deltamd to be 0.516+/-0.016(stat)+/-0.010(syst) ps-1.

Journal Article↗

PubMed2002

Measurement of the B0-B-0 oscillation frequency with inclusive dilepton events.

The B0-B-0 oscillation frequency has been measured with a sample of 23 x 10(6) BB- pairs collected with the BABAR detector at the PEP-II asymmetric B Factory at SLAC. In this sample, we select events in which both B mesons decay semileptonically and use the charge of the leptons to identify the flavor of each B meson. A simultaneous fit to the decay time difference distributions for opposite- and same-sign dilepton events gives deltamd = 0.493+/-0.012(stat)+/-0.009(syst) ps-1.

Journal Article↗

PubMed2002

Search for T and CP violation in B0-B-0 mixing with inclusive dilepton events.

We report the results of a search for T and CP violation in B0-B-0 mixing using an inclusive dilepton sample collected by the BABAR experiment at the PEP-II B Factory. The asymmetry between l+l+ and l-l- events allows us to compare the probabilities for B-0-->B0 and B0-->B-0 oscillations and thus probe T and CP invariance. Using a sample of 23 x 10(6) BB- pairs, we measure a same-sign dilepton asymmetry of A(T/CP) = [0.5+/-1.2(stat)+/-1.4(syst)]%. For the modulus of the ratio of complex mixing parameters p and q, we obtain q/p = 0.998+/-0.006(stat)+/-0.007(syst).

Journal Article↗

PubMed2001

Work experience program at a metropolitan paediatric hospital: assisting rural and metropolitan allied health professionals exchange clinical skills.

The needs of rural allied health professionals (AHPs) have been widely documented. In particular, problems of professional isolation, lack of professional development opportunities and limited support systems have been highlighted as problems associated with working in rural and remote areas. This research aimed to provide rural and remote AHPs with an opportunity to gain experience in paediatric clinical areas of their choice, to provide rural/remote and metropolitan AHPs with an opportunity to share clinical knowledge and expertise, and to develop networks between rural/remote and metropolitan AHPs. A clinical experience program was developed to meet these aims. Twenty-nine AHPs from rural and remote areas of Queensland participated in the program. Participants completed questionnaires at the end of clinical experience program and 4-8 weeks after the visit. A focus group was also conducted. Analyses found the program met the majority of participants goals and expectations. Enhanced clinical skills in specialist paediatric areas, increased networking and access to resources were reported by rural/remote AHPs as benefits of the program. The role of a clinical consultant was found to be critical to the success of the program.

Allied Health Personnel↗

PubMed2000

Clinical utility of the modified barium swallow.

The purpose of this investigation was to evaluate the immediate and clinically relevant information gained from the modified barium swallow study and to determine the impact of the procedure on patient management. A database containing a nonrandom sample of 608 swallowing studies was reviewed. Results showed that only 10.4% of the studies were classified as normal examinations and aspiration occurred in 32.4%. However, swallowing abnormality without aspiration was recorded in 57.2% of the studies. Five additional outcome variables were assessed: referrals made to other specialties, effectiveness of applied compensatory strategies, treatment recommendations, mode of intake change, and diet grade change. Nearly 83% of the 608 studies showed change in at least one of the variables: needed referral to a specialist was identified on 26.3%; compensatory strategies that improved swallow physiology were identified on 48.4%; swallowing therapy was recommended on 37.2%; changes in mode of intake occurred on 31.4%; and diet texture changes were recommended on 43.8%. The low percentage of normal studies coupled with the high percentage of change in measurable variables indicate high clinical utility for the modified barium swallow study. The misguided tendency to refer to the modified barium study only as a tool for identifying aspiration and the appropriate utilization of the examination for identification of underlying abnormality in swallowing physiology are explained.

Aged↗

PubMed2000

Rehabilitation of the burned upper extremity.

With the advancement in medical technology and more effective life-sustaining measures, the rehabilitation therapist is faced with the immense task of effectively restoring functional ROM, strength, and mobility and producing a cosmetic result acceptable to the patient. Rehabilitation therapists have a very significant role to play in achieving these goals. The patients and their families come to rely very heavily on the therapists for advice, support, and information both in the acute phase of burn management and, potentially, for years to follow. A concerted team approach is necessary for a satisfactory functional outcome following burn injury.

Arm Injuries↗

PubMed1999

Behaviour of DRG sensory neurites at the intact and injured adult rat dorsal root entry zone: postnatal neurites become paralysed, whilst injury improves the growth of embryonic neurites.

The dorsal root entry zone is a PNS-CNS junction between Schwann cells and astrocytes, defining the site where dorsal root ganglia (DRG) axons enter the adult mammalian spinal cord. Following dorsal root injury (rhizotomy), DRG axons regenerate within the PNS environment of the root but stop at the DREZ and fail to re-enter the spinal cord. We have used an in vitro model to compare how neurites growing from embryonic (E13) and postnatal (P0 and adult) DRG neurons behave at the uninjured and rhizotomized adult rat DREZ. We find that both freshly dissected and conditioned-lesioned postnatal DRG neurons seldom grow neurites across cryosections of the uninjured or rhizotomized DREZ. However, embryonic DRG neurons more readily grow neurites across cryosections of the uninjured and 7-day post-lesion (dpl) DREZ and are dramatically better able to cross the 21 dpl DREZ. This enhanced growth was abolished by co-incubation with a function-blocking antiserum to beta1-integrin receptors, whilst immunoreactivity for some beta1-integrin ligands (tenascin-C and fibronectin) increased at the DREZ by 21 dpl, suggesting that beta1-integrin ligands may stimulate the growth of embryonic neurites across the 21 dpl DREZ. Fluorescence time-lapse video-microscopy was used to record the behaviour of dye-labelled postnatal DRG neurites as they encounter the uninjured adult DREZ in vitro. Neurites rarely turned around at the DREZ, but instead became paralysed. Of a variety of chemical modifications to uninjured DREZ cryosections, only treatment with methanol, chloroform, or the protease inhibitor D-phe-pro-arg chloromethylketone hydrochloride (PPACK, 100 microM) caused any increase in the proportion of postnatal neurites which crossed the DREZ.

Animals↗

PubMed1998

The relationship between aerobic fitness and both power output and subsequent recovery during maximal intermittent exercise.

The primary aim of the study was to establish a link between aerobic adaptation and both the recovery from maximal short duration exercise, and the ability to maintain power output in a subsequent bout. The question as to whether the aerobic adaptations facilitating recovery are centrally or peripherally located was also examined. Male university level rugby and soccer players (n=20) volunteered for the study. Mean (SD) age, mass and maximal oxygen uptake (VO2 max) was 21.9 (1.8) years, 84.7 (12.7) kg and 52.7 (6.9) ml x kg(-1) x min(-1) respectively. Subjects completed six 15s maximal intensity sprints (90s active recovery) on a Monark friction braked cycle ergometer. A significant relationship (r=-.49, P=0.03) was obtained between VO2 max (mL x kg(-1) x min(-1)) and the percent drop-off in mean power in bouts 5 and 6 compared with bout 1. A correlation of r=-.62 (P=0.002) was obtained between VO2 max (mL x kg(-1) x min(-1)) and the percent drop off in peak power in bouts 5 and 6 compared with bout 1. A significant correlation was obtained between arterial venous oxygen difference and the drop in mean power (r=-.54, P=0.02) but not with the drop in peak power (r=-.22, P=.36). There was no significant relationship between cardiac output and the drop in mean power (r=-.16, P=.51) or the drop in peak power (r=-.02, P=.94). Percent drop-off in oxygen consumption, when compared with the first, in the second (RVO2(30-60)), third (RVO2(60-90)), fourth (RVO2(90-120)) and fifth (RVO2(120-150)) 30s time periods of recovery following the intermittent protocol was calculated. Correlations between VO2 max (ml x kg(-1) x min(-1)) and these variables were (r=.51, P=-0.03), (r=.44, P=0.06), (r=.63, P=-0.003) and (r=.6, P=0.007) respectively. Consequently it was concluded that maximal oxygen uptake particularly the peripheral component, is an important determinant of the ability to perform intermittent exercise of this nature and to recover between bouts.

Adaptation, Physiological↗

PubMed1998

Paediatricians: referral rates and speech pathology waiting lists.

OBJECTIVE: This study aimed to examine paediatricians' training in and understanding of communication development and disabilities and their attitudes to speech pathology waiting lists and management practices. The relationship between these factors and referral rates was also investigated. METHODOLOGY: A total of 229 paediatricians registered with the Australian College of Paediatrics participated in the study in November 1996. They answered 15 multiple-choice questions designed to collect demographic information and data pertaining to their training and understanding of communication development and disabilities. The survey also obtained data on referral rates to public and private speech pathology services and on paediatricians' perceptions of speech pathology waiting lists and possible management strategies. RESULTS: Referral rate to public and private speech pathology services was found to be associated with the quality of paediatricians' training in and knowledge of communication development and disabilities. Paediatricians who had regular contact with speech pathologists were also more likely to make more referrals. Waiting lists had a negative influence on referral rate. Treatment rather than assessment waiting lists were preferred. Paediatricians believed the best solution to speech pathology waiting lists was an increase in staffing levels particularly in community health centres. Respondents reported that 1-4 months was an acceptable time to wait for speech pathology care and indicated the order of importance of factors for prioritising children. CONCLUSIONS: The results have important implications for developing best practice models for improving referral processes and access to speech pathology services for children with communication disabilities.

Australia↗

PubMed1997

Postoperative analgesia with preoperative oral ibuprofen or acetaminophen in children undergoing myringotomy.

Previous studies have shown over 70% of children require analgesics following bilateral myringotomy and tube placement (BM&T). This double-blind, placebo-controlled study compared the postoperative analgesic effects of preoperatively administered oral acetaminophen or ibuprofen. Forty three ASA I or II children age six months or older scheduled for elective BM&T were randomized to receive acetaminophen (paracetamol) 15 mg.kg-1, ibuprofen 10 mg.kg-1, or placebo. Postoperative pain was assessed using the Children's Hospital of Eastern Ontario Pain Scale (CHEOPS) upon arrival to the PACU and at 5, 10, 15, 30, 45, and 60 min. CHEOP scores did not differ between the groups at any time. There was no difference in the number of children receiving rescue analgesia. This study showed no benefit of preoperatively administered oral ibuprofen 10 mg.kg-1 or acetaminophen 15 mg.kg-1 over placebo for the relief of postoperative pain in children undergoing BM&T.

Acetaminophen↗

PubMed1997

A comparison of the expressive communication skills of triplet, twin and singleton children.

Few studies have focused on the language acquisition of higher multiple birth sets. In this study, the communication skills of 51 triplet children are described. The measures used were: mean length of utterance; type-token ratio; conversational acts; phoneme repertoire; and number of different types of phonological processes used. The data gained were used to compare the communication skills of triplets with those of twins, singletons and normative data available in the literature. Siblings within triplet sets were also compared using language samples obtained from adult-child interactions and when the three children were playing together. The results indicated that the triplets' early communication skills were different from those of both singletons and twins. The triplets' difficulties included delayed syntactic development, limited use of different language functions and delayed phonological development. In contrast, twins' communication profile is characterised by disordered phonological development.

Child, Preschool↗