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Biomedical subjects

J Mercer

Publications and source records attributed to J Mercer.

At least 19 recordsLinked to original sources
PubMed2000

Human hip and knee torque accommodations to anterior cruciate ligament dysfunction.

It has been postulated that the adaptations of lower extremity function exhibited by anterior cruciate ligament (ACL) deficient and post-ACL surgical patients represent early accommodations to the loss of ACL function after injury so that excessive anterior displacement of the tibia is prevented. Prior studies have suggested that compensation patterns in ACL deficient and post-ACL surgical subjects may affect joint moments of the knee as well as the hip. However, the variance in knee and hip forces between ACL deficient, post-surgical ACL and uninjured groups has not been clearly elucidated. The purpose of this study was to assess hip:knee extensor torque ratios relative to anterior tibia shear in pre-surgical-ACL deficient, post-surgical and uninjured subjects. Measurements of hip and knee joint moments and anterior tibia shear were recorded from 45 injured and uninjured subjects (21 men, 24 women) during lower extremity, variable resistance exercise. Anterior tibia shear was computed by decomposing joint moments and reaction forces according to a model derived from cadaver knee dissections and radiography, in combination, to estimate the tibio-femoral compressive and shear forces generated by the patellar tendon at various angles throughout the knee joint range. Three groups of subjects were studied: recently injured ACL deficient pre-surgical subjects who were scheduled for immediate surgery (PRE; n = 15); postsurgical subjects who had undergone ACL reconstructive surgery at least 1 year prior to testing (POST; n = 15); and uninjured controls (CON; n = 15). All PRE and POST subjects had a normal contralateral limb. Tests were conducted under six conditions: 1 and 1.5 Hz cadence and maximal speed at 33% and 50% one repetition maximum resistance. The results revealed that the hip:knee ratios were significantly greater for the post-ACL surgical group than the PRE and CON groups (P<0.01; P<0.03). There were significant negative correlations between the hip extensor:knee extensor torque ratios and maximal anterior tibia shear across all groups. The hip:knee extensor torque ratio increased with decreased anterior tibia shear in all groups with significant correlations ranging from -0.55 to -0.88 (P<0.01) for the injured limbs of PRE and POST groups, and -0.64 to -0.78; (P<0.01) for the CON group. The highest overall correlations were found for the post-surgical subjects. The results revealed that anterior tibia shear declined significantly with speed (P<0.01) in all groups. However, the converse was true for the hip:knee extensor torque ratio across speeds. The ratio increased significantly with speed (P<0.001) for all groups at the 33% and 50% resistances. The results suggest (1) that post-ACL surgical subjects appear to accommodate to ACL substitution by using hip extensors to a significantly greater extent than the uninjured controls in closed-chain lower extremity exercise; (2) that the hip:knee extensor torque ratio is significantly related to the magnitude of anterior tibia shear; and (3) that the anterior tibia shear is significantly reduced as speed increases in closed-chain lower extremity exercise.

Adaptation, Physiological↗
PubMed1999

Spirometry in primary care practice: the importance of quality assurance and the impact of spirometry workshops.

OBJECTIVE: To determine the quality of spirometry performed in primary care practice and to assess the impact of formal training. DESIGN: Randomized, controlled prospective interventional study. SETTING: Primary care practice, Auckland City, New Zealand. PARTICIPANTS: Thirty randomly selected primary care practices randomized to "trained" or "usual" groups. One doctor and one practice nurse were nominated to participate from each practice. INTERVENTIONS: "Trained" was defined as participation in an "initial" spirometry workshop at week 0 and a "maintenance of standards" workshop at week 12. "Usual" was defined as no formal training until week 12, when participants they attended the same "initial" workshop provided for the trained group. The study duration was 16 weeks. Each practice was provided with a spirometer to be used at their clinical discretion. MEASUREMENTS AND RESULTS: Spirometry data were uploaded weekly and analyzed using American Thoracic Society (ATS) criteria for acceptability and reproducibility. The workshops were assessed objectively with practical and written assessments, confirming a significant training effect. However, analysis of spirometry performed in clinical practice by the trained practitioners revealed three acceptable blows in only 18.9% of patient tests. In comparison, 5.1% of patient tests performed by the usual practitioners had three acceptable blows (p<0.0001). Only 13.5% of patient tests in the trained group and 3.4% in the usual group (p<0.0001) satisfied full acceptability and reproducibility criteria. However, 33.1% and 12.5% of patient tests in the trained and usual groups, respectively (p<0.0001), achieved at least two acceptable blows, the minimum requirement. Nonacceptability was largely ascribable to failure to satisfy end-of-test criteria; a blow of at least 6 s. Visual inspection of the results of these blows as registered on the spirometer for the presence of a plateau on the volume-time curve suggests that < 15% were acceptable. CONCLUSIONS: Although a significant training effect was demonstrated, the quality of the spirometry performed in clinical practice did not generally satisfy full ATS criteria for acceptability and reproducibility. Further study would be required to determine the clinical impact. However, the ATS guidelines allow for the use of data from unacceptable or nonreproducible maneuvers at the discretion of the interpreter. Since most of the failures were end-of-test related, the FEV1 levels are likely to be valid. Our results serve to emphasize the importance of effective training and quality assurance programs to the provision of successful spirometry in primary care practice.

Adolescent↗
PubMed1998

Short-term side effects of stimulant medication are increased in preschool children with attention-deficit/hyperactivity disorder: a double-blind placebo-controlled study.

Preschool children with attention-deficit/hyperactivity disorder (ADHD) (27 boys, 5 girls, mean age 4 years 10 months) participated in a double-blind placebo-controlled crossover drug study to assess the side effects of methylphenidate. Children received twice daily, for at least 1 week each, placebo, 0.3 mg/kg methylphenidate, and 0.5 mg/kg methylphenidate. Side effects were monitored by a parent rating scale designed for medication studies. In general, methylphenidate was tolerated relatively well, with no children withdrawing because of adverse effects. Of 17 childhood behaviors usually associated with side effects, 8 behaviors showed significant changes, generally at the higher dose of methylphenidate. Interestingly, 3 of the side effects were associated with improved behavior. The number of side effects appeared higher than what is usually reported in a population of school-age children, but few parents reported them as being severe. Severe side effects were reported in less than 10% of the sample, with approximately as many reports of severe effects on placebo as on low and high doses of the medication. The results indicate that methylphenidate has a relatively low toxicity in preschool children (over the first 7-10 days), that some behavioral changes that might be viewed as side effects of methylphenidate are actually normal behaviors or ADHD behaviors in preschool children (e.g., sociability), that these "side-effect" behaviors are more common in preschool than school-age children, that some "side effects" of methylphenidate are associated with improvements in behavior, and that preschool and school-age children may have different side effects of methylphenidate (e.g., mood changes and anxiety).

Affect↗
PubMed1997

Effects of methylphenidate on preschool children with ADHD: cognitive and behavioral functions.

OBJECTIVE: To report on implications for methylphenidate treatment of this very young age group and the need to examine factors related to achieving compliance. METHOD: Thirty-one children with attention-deficit hyperactivity disorder (ADHD), aged 4 to 6 years, participated in a double-blind, placebo-controlled study using placebo, 0.3 mg/kg, and 0.5 mg/kg of methylphenidate twice per day. RESULTS: Improvements related to medication were obtained on cognitive tests of attention and impulsivity as well as behaviors assessed by parent rating scales. In an interactive setting with their mothers, attentional abilities and the children's ability to work more productively also showed improvement. However, no changes were obtained with respect to the children's tendency to comply with parental requests. Side effects increased slightly with the high dosage of medication but remained mild. CONCLUSION: The results suggest that methylphenidate can be used to improve the functioning of preschool-age children with ADHD, in a manner similar to their school-age counterparts.

Attention Deficit Disorder with Hyperactivity↗
PubMed1997

Managing vancomycin-resistant enterococci. A winning team approach.

Antibiotics have been the treatment of choice for a broad range of bacterial infections for decades. In recent years, however, concern has been growing over the increasing incidence of infections that are resistant to known antibiotics. A 1995 outbreak of ampicillin- and vancomycin-resistant enterococci (VRE) at the 3Y site of the McMaster University Medical Centre brought this concern home to us and resulted in the development of outbreak-management guidelines for VRE.

Ampicillin Resistance↗
PubMed1995

How "blind" are double-blind placebo-controlled trials of benzodiazepine hypnotics?

This study examined the accuracy of insomnia patients and their treating physicians in rating whether an active hypnotic drug or a placebo was given in treatment. Forty older adults with primary insomnia were randomly assigned to either an active (temazepam) or a placebo condition using a double-blind strategy. Ratings of treatment conditions were obtained at 1 week (early treatment), 4 weeks (midtreatment), and 8 weeks (late treatment). Patients were able to accurately discriminate (beyond chance levels) between the active and placebo medications at the early (76.9% accuracy) and late treatment assessment timepoints (78.1% accuracy), but not at midtreatment (51.5% accuracy). Therapists, however, were able to make accurate discriminations at the late treatment assessment timepoint only (80% accuracy); early (69.2% accuracy) and midtreatment (47.2% accuracy) ratings did not exceed chance levels. Patients who had used hypnotic drugs prior to this trial were more accurate in their judgments of treatment conditions than those without prior exposure. The findings raise an important issue about the internal validity of the double-blind strategy, which may in fact be only a single-blind procedure.

Aged↗
PubMed1994

An evaluation of iodine-123 iodoazomycinarabinoside as a marker of localized tissue hypoxia in patients with diabetes mellitus.

Peripheral vascular disease is a serious and common complication in patients with diabetes mellitus (DM). Evaluation is, conventionally, by transcutaneous oxygen tension measurements (TcpO2), although this technique has some limitations in the evaluation of tissue viability. We have evaluated a new, radiolabelled, in vivo marker of tissue hypoxia, iodoazomycinarabinoside (IAZA), by comparing TcpO2 measurements with patterns of iodine-123 IAZA uptake in ten patients (19 lower limbs) with DM and peripheral vascular disease using conventional gamma camera imaging techniques. Normal uptake patterns were seen in limbs in which normal TcpO2 measurements were obtained. Diffusely increased uptake of [123I]IAZA was seen in limbs with reduced TcpO2. Focally increased uptake was seen in ulcers or in areas of atrophic skin change. A semi-quantitative measure showed an inverse correlation between [123I]IAZA and TcpO2 values. These data suggest that tissue hypoxia can be imaged in this population of patients and that severity of disease can be assessed. A longitudinal prospective trial is now being developed.

Adult↗
PubMed1994

Tuberculosis case-finding in Western Australia.

The records of a total of 497 patients notified to have active tuberculosis (TB) in Western Australia from 1986 to 1990 inclusive have been reviewed in relation to case-finding. Of these, 276 (55.5%) were Asian migrants, 92 (18.5%) Europeans and 110 (22.1%) Australians. The disease was confirmed bacteriologically in 247 (49.7%). The most common mode of diagnosis was symptomatic presentation (39.8%), followed by migrant health surveillance (36.8%), incidental finding (7.5%), regular follow-up (3.8%) and pre-employment chest radiography (1.8%). Contact examination in the non-Asians accounted for only 0.4% while diagnosis after death 2.6%. There was no statistical difference in the detection of TB disease and infection among contacts of index patients with diseases at different sites or of different bacteriological status. The results of the study justify the present strict surveillance over the Asian migrants but do not support the overcautious policy of the contact examination procedures in the non-Asians, for which changes are proposed. Twelve patients whose confirmed TB was diagnosed only at autopsy had a mean age of 75.4 (range 41-86) years. Six of them had miliary or disseminated TB, three co-existing serious medical conditions and none a past history of the disease. The pattern has been well described and clinicians should keep a high index of suspicion for TB in this group of patients.

Adult↗
PubMed1994

Neuropsychological functioning in older insomniacs with or without obstructive sleep apnea.

The relationships between neuropsychological functioning and sleep loss, sleep apnea, and hypoxemia were examined. Forty-five older insomniacs (M age = 64.6 years) with or without sleep apnea were administered neuropsychological tests after 1 night of nocturnal monitoring in a sleep laboratory. The results showed few differences on cognitive and psychomotor performance between individuals with sleep disruptions alone compared with those whose insomnia was associated with sleep apnea and hypoxemia. There were no significant relationships between nocturnal sleep and respiratory variables and daytime functioning. Furthermore, cognitive and psychomotor performance in older insomniacs with or without sleep apnea revealed minimal impairment compared with age-matched normative data. The results suggest that when the severity of sleep disruptions is controlled, there are minimal differences in neuropsychological functioning of older adults with mild to moderate sleep apnea compared with those without apnea.

Aged↗
PubMed1994

Microbiological aspects of an outbreak of Legionnaires' disease in south western Sydney.

In April 1992 an outbreak of Legionnaires' disease occurred in south western Sydney. Twenty four patients were diagnosed as having Legionnaires' disease either on the basis of a positive culture of Legionella pneumophila serogroup I from a respiratory specimen (14 patients) or a four-fold or greater rise in antibody titre or isolated convalescent titre > 1024 with IgM antibodies present (10 patients). This is the largest outbreak in New South Wales since 44 cases of Legionnaires' disease were reported in Wollongong in 1987. Culture and direct immunofluorescent staining (DFA) were performed for early laboratory diagnosis. The DFA test and a set of defined clinical criteria were then used to classify patients as probable cases of Legionnaires' disease for subsequent Public Health investigations. The DFA test had a predictive value for a positive culture of 45.8% and for a negative culture of 97.1%. Its positive predictive value for a definite diagnosis of Legionnaires' disease (either positive culture or seroconversion), however, was 78.3% with a negative predictive valve of 95.1%. During a 27 day period DFA and culture for Legionella species were performed on 198 specimens from 127 patients. Cultures became positive after a mean of 5 days incubation (range 1-11 days). The use of both selective and non-selective media is recommended for optimal recovery of L. pneumophila since some isolates were obtained on only one culture plate. After an initial evaluation of heat decontamination of specimens this process was abandoned, since in 8/63 specimens so treated, L. pneumophila was recovered prior to but not following heat decontamination and was not grown only in heated specimens.(ABSTRACT TRUNCATED AT 250 WORDS)

Disease Outbreaks↗
PubMed1993

Dysfunctional beliefs and attitudes about sleep among older adults with and without insomnia complaints.

This study examined the beliefs and attitudes about sleep among 145 older adults. Ss were either chronic insomniacs (n = 74) or self-defined good sleepers (n = 71). They rated their level of agreement or disagreement (visual analog scale) with 28 statements tapping various beliefs, expectations, and attributions about several sleep-related themes. The results showed that insomniacs endorsed stronger beliefs about the negative consequences of insomnia, expressed more hopelessness about the fear of losing control of their sleep, and more helplessness about its unpredictability. These findings suggest that some beliefs and attitudes about sleep may be instrumental in perpetuating insomnia. The main clinical implication is that these cognitions should be identified and targeted for alteration in the management of late-life insomnia.

Aged↗
PubMed1993

Physiological correlates of painful stimulation in preterm infants.

OBJECTIVE: The study investigates the physiological responses of preterm infants to procedures that are routinely performed in intensive care nurseries. Changes in heart rate, respiration rate, and oxygen saturation were examined as indicators of the level of discomfort experienced by the infant during the procedures. DESIGN: Clinical descriptive. Systematic observations of the infants were conducted during periods of rest as well as during routine interventions. SETTING: All observations were recorded from monitored preterm infants in the intensive care units of two urban hospitals. PATIENTS: Thirty-five preterm infants 24-30 weeks gestational age and weighing < 2,000 g at birth. Data were collected from all infants in the units who met the weight criterion. INTERVENTIONS: The researchers observed the infants while the intensive care nursery staff were performing routine care procedures. Observations were made during procedures that adults would consider to be painful, such as injection, heel stick, tape removal, and squeezing of the heel to induce blood flow after heel stick, as well as nonpainful procedures, such as handling, temperature taking, alcohol swabbing, patting, taping a tube, feeding, and placing a pacifier. MAIN OUTCOME MEASURES: Heart rate, respiration rate, and oxygen saturation were recorded from infant monitors. Mean values of the three measures during procedures were compared with mean values before and after procedures. RESULTS: Significant differences (p < 0.001) were found among pre-, peri-, and post-procedures for all three outcome measures. Heart rate and respiration rate means were significantly (p < 0.001) higher during procedures that adults consider to be painful than in those regarded as nonpainful. Oxygen saturation was lower (p < 0.001) for painful procedures than for nonpainful procedures. Gender and infant size comparisons yielded inconclusive results. CONCLUSION: The outcome measures appear to be reliable indices of preterm infant responses to painful stimulation.

Body Weight↗
PubMed1992

Neutralization of multiple laboratory and clinical isolates of human immunodeficiency virus type 1 (HIV-1) by antisera raised against gp120 from the MN isolate of HIV-1.

Vaccines prepared from the envelope glycoprotein, gp120, of the common laboratory isolate of human immunodeficiency virus type 1 (HIV-1) (IIIB/LAV-1) elicit antibodies that neutralize the homologous virus but show little if any cross-neutralizing activity. This may be because the principal neutralizing determinant (PND) of gp120 is highly unusual in the IIIB/LAV-1 strain and is not representative of those found in the majority of field isolates. We have now examined the immunogenicity of recombinant gp120 prepared from the MN strain of HIV-1 (MN-rgp120), whose PND is thought to be representative of approximately 60% of the isolates in North America. Our results show that MN-rgp120 is a potent immunogen and elicits anti-gp120 titers comparable to those found in HIV-1-infected individuals. While both MN-rgp120 and IIIB-rgp120 induced antibodies able to block gp120 binding to CD4, strain-specific and type-common blocking antibodies were detected. Finally, antibodies to MN-rgp120 but not to IIIB-rgp120 were effective in neutralizing a broad range of laboratory and clinical isolates of HIV-1. These studies demonstrate that susceptibility or resistance to neutralization by antibodies to gp120 correlates with the PND sequence and suggest that the problem of antigenic variation may not be insurmountable in the development of an effective AIDS vaccine.

Amino Acid Sequence↗
PubMed1990

Brush border enzymes in coeliac disease: histochemical evaluation.

Two hundred and ninety four duodenal and jejunal mucosal biopsy specimens from patients with coeliac disease, treated and untreated, and other conditions were examined histologically and by histochemical staining for five peptidase and three disaccharidase enzymes to determine profiles of activity. Suppression of activity paralleled the histology with the following enzymes: lactase, trehalase, brush border endopeptidase, dipeptidyl peptidase II and isomaltase. Lactase, trehalase, and brush border endopeptidase were specifically suppressed in untreated coeliac disease and were diagnostically useful. Examination of a combination of enzymes is recommended.

Adolescent↗
PubMed1989

Phenylalanine hydroxylase gene haplotypes in Polynesians: evolutionary origins and absence of alleles associated with severe phenylketonuria.

A total of 630 haplotypes for the phenylalanine hydroxylase (PAH) gene locus were established in five groups of Polynesians comprising Samoans, Tongans, Cook Islanders, Maori, and Niueans. Considerable genetic continuity was demonstrated between these widely dispersed populations, since three common haplotypes (4, 1, and 7) constituted over 95% of alleles. A control group of individuals from Southeast Asia shared the same major haplotypes, 4, 1, and 7, with Polynesians. These data provide further support for the theories of genetic homogeneity and of Asian affinities of the Polynesian precursor populations. The absence of severe phenylketonuria (PKU) in both Polynesians and Southeast Asians is consistent with the lack of PAH haplotypes 2 and 3, on which the severe PKU mutants have arisen among Caucasians.

Biological Evolution↗
PubMed1988

How do we teach pathology? The laser videodisc and computer-assisted learning.

A laser videodisc, holding 54,000 still frames per side, can be used to provide visual material of excellent quality for pathology teaching. In a collaborative project between ten pathology departments, the first pathology videodisc has recently been completed and the production of the disc is described. When used as illustrative material for computer-assisted learning programs, the videodisc offers accurate random access of still frames and allows the overlay of computer-generated graphics onto the video picture. This can be used to pre-identify every individual feature of a particular frame, and an example tutorial program is described to show how this may be used to improve the students' understanding of what they see. Details and costs are given for a workstation suitable for this application and potential future developments for this teaching method are discussed. Although objective assessment of the cost-effectiveness of interactive video in teaching pathology has yet to be undertaken, one suitably designed program can give individual tuition to many students, making this a most efficient use of teaching time.

Computer-Assisted Instruction↗