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Biomedical subjects

K McLeod

Publications and source records attributed to K McLeod.

At least 19 recordsLinked to original sources
PubMed2005

Inter- and intraobserver variability in LVH and RVH reporting in pediatric ECGs.

BACKGROUND: Physicians' diagnoses are often used as the gold standard for evaluating computer electrocardiogram (ECG) interpretation programs. As part of a larger study to evaluate the Glasgow pediatric ECG analysis program, inter- and intraobserver variability in the ECG reporting of two pediatric cardiologists was examined. METHODS: The ECGs of 984 children were sent for reporting independently by two cardiologists with all identifying information except age and sex removed. Three hundred twenty ECGs had no clinical indication available, and they were thus reported "blind." For 664 ECGs, the clinical indication was known and included with the ECG trace. All ECGs reported as right ventricular hypertrophy (RVH) or left ventricular hypertrophy (LVH) were returned to the cardiologists without their knowledge for reporting a second time "blind" as to the clinical indication. RESULTS: When the cardiologists' reports were compared with each other, the provision of clinical information led to greater agreement between them for the diagnosis of LVH (kappa increased from 0.44 to 0.52) but did not substantially affect their agreement in diagnosing RVH (kappa fell from 0.66 to 0.63). Intraindividual comparisons in 166 ECGs revealed that one cardiologist was more consistent in diagnosing RVH and the other more consistent in diagnosing LVH. CONCLUSIONS: This study has demonstrated the difficulties in using cardiologists' diagnoses as the gold standard with which to evaluate pediatric ECGs.

Adolescent↗
PubMed2005

Long-term survival of surgically treated hip fracture in an Australian regional hospital.

This study was undertaken to identify factors influencing outcome in elderly patients operated for hip fracture. In particular, this study examined factors related to mortality at least 30 months post-fracture. Hospital records and death registrations were analysed for 463 patients aged 60 or more years treated for hip fracture at a Queensland regional hospital between 1997 and 2001. The overall mortality for surgically treated patients was 13.7% at 100 days and 24.9% at one year Patient factors including age, gender, health status and place of residence were the predominant influences on mortality. Non-patient and process factors including delay to surgery, type of operation and type of anaesthetic had minimal impact on mortality. No major determinants of length of hospital stay were identified. Patient health status was the main determinant for surgical delay. Our results confirm the persistently high mortality in this group of patients, and suggest that the main determinants of outcome are patient- rather than process-related.

Age Distribution↗
PubMed2003

Use of an implantable loop recorder to investigate syncope in a cat.

The Reveal is an implantable loop recorder. It is increasingly being used in humans for the diagnosis of unexplained syncope where it is believed that cardiac arrhythmias may play a role, and may have great potential for investigating syncope in veterinary patients. The purpose of this report is to describe the first use of the device in the diagnosis of unexplained syncope in a cat.

Animals↗
PubMed2003

Tobacco in the news: an analysis of newspaper coverage of tobacco issues in Australia, 2001.

OBJECTIVE: To assess the extent and nature of newspaper coverage of tobacco related issues in Australia in 2001. DESIGN: Content analysis of newspaper articles. SUBJECTS: All articles (n=1188) at least seven lines long and containing at least one paragraph focused on tobacco in all major Australian national and State capital city newspapers (n=12) in 2001. MAIN OUTCOME MEASURES: Number of articles, month of publication, State in which newspaper published, prominence of article, type of article, article theme, and slant of article relative to tobacco control objectives. RESULTS: The number of tobacco articles varied considerably in different months over the course of the year, from a low of 51 in December to a peak of 180 in May. The most frequent theme was secondhand smoke issues (30% of articles), with the second most dominant theme related to education, prevention, and cessation programmes and services (20%). Events that were covered were predominantly positive for tobacco control: 62% of articles were related to events that were positive, compared with 21% that were negative for tobacco control objectives. Excluding news articles, the opinions expressed by the authors of articles were also mainly positive (61%) rather than negative (22%) for tobacco control objectives. The amount of coverage of and population exposure to tobacco focused articles showed considerable variation across different Australian States, with Victoria having the highest frequency and rate of articles and the most media impressions per capita throughout 2001. CONCLUSIONS: : Coverage of events and opinions related to tobacco in Australian newspapers in 2001 was generally positive for tobacco control objectives. Given that over 2 million individuals (out of a population of 19 million) were potentially exposed to tobacco related newspaper articles per day in Australia, this represents good news for tobacco control advocates. The variation in news coverage in different States and at different times in the year, however, illustrates how a combination of local events and advocacy efforts may at times combine to make tobacco more newsworthy. Understanding which tobacco issues are most likely to be covered and the nature of the coverage about them provides valuable feedback for tobacco control advocates and is a useful gauge of actual events as well as the tobacco related agendas promoted by the press.

Attitude to Health↗
PubMed2002

Mechanical strain, induced noninvasively in the high-frequency domain, is anabolic to cancellous bone, but not cortical bone.

Departing from the premise that it is the large-amplitude signals inherent to intense functional activity that define bone morphology, we propose that it is the far lower magnitude, high-frequency mechanical signals that continually barrage the skeleton during longer term activities such as standing, which regulate skeletal architecture. To examine this hypothesis, we proposed that brief exposure to slight elevations in these endogenous mechanical signals would suffice to increase bone mass in those bones subject to the stimulus. This was tested by exposing the hind limbs of adult female sheep (n = 9) to 20 min/day of low-level (0.3g), high-frequency (30 Hz) mechanical signals, sufficient to induce a peak of approximately 5 microstrain (micro epsilon) in the tibia. Following euthanasia, peripheral quantitative computed tomography (pQCT) was used to segregate the cortical shell from the trabecular envelope of the proximal femur, revealing a 34.2% increase in bone density in the experimental animals as compared with controls (p = 0.01). Histomorphometric examination of the femur supported these density measurements, with bone volume per total volume increasing by 32% (p = 0.04). This density increase was achieved by two separate strategies: trabecular spacing decreased by 36.1% (p = 0.02), whereas trabecular number increased by 45.6% (p = 0.01), indicating the formation of cancellous bone de novo. There were no significant differences in the radii of animals subject to the stimulus, indicating that the adaptive response was local rather than systemic. The anabolic potential of the signal was evident only in trabecular bone, and there were no differences, as measured by any assay, in the cortical bone. These data suggest that subtle mechanical signals generated during predominant activities such as posture may be potent determinants of skeletal morphology. Given that these strain levels are three orders of magnitude below strains that can damage bone tissue, we believe that a noninvasive stimulus based on this sensitivity has potential for treating skeletal complications such as osteoporosis.

Animals↗
PubMed2001

Anabolism. Low mechanical signals strengthen long bones.

Although the skeleton's adaptability to load-bearing has been recognized for over a century, the specific mechanical components responsible for strengthening it have not been identified. Here we show that after mechanically stimulating the hindlimbs of adult sheep on a daily basis for a year with 20-minute bursts of very-low-magnitude, high-frequency vibration, the density of the spongy (trabecular) bone in the proximal femur is significantly increased (by 34.2%) compared to controls. As the strain levels generated by this treatment are three orders of magnitude below those that damage bone tissue, this anabolic, non-invasive stimulus may have potential for treating skeletal conditions such as osteoporosis.

Adaptation, Physiological↗
PubMed2000

Globalization and international trade in the twenty-first century: opportunities for and threats to the health sector in the south.

Globalization and international trade are important forces at the turn of the century. This article explores how freer international trade will affect developing countries that are net importers of health care goods and services. Four commodities are used as special cases for discussion: pharmaceuticals, health care technologies, pesticides, and tobacco and its related products. The authors discuss the role of international specialized agencies, such as the World Trade Organization, World Health Organization, and World Bank, that are concerned with international trade and its health and health care consequences, and argue that closer collaboration is required among these agencies if the negative effects of trade liberalization on developing countries are to be mitigated. The authors pose a number of research questions that could help in developing proactive policies for the South on the trade of goods and services with harmful effects on health as well as those with potential health and economic benefits.

Commerce↗
PubMed2000

Performance and carcass merit of growing beef steers with chlortetracycline-modified sensitivity to pituitary releasing hormones and fed two dietary protein levels.

This paper reports the effects of reduced sensitivity to growth hormone-releasing hormone and thyrotropin-releasing hormone through feeding a subtherapeutic level of chlortetracycline (CTC; 350 mg CTC/d) and two levels of dietary CP (10% and 13% of diet DM) on growth performance and carcass merit characteristics. Thirty-two steers (initial average BW, 286 kg) were adapted to a common 13% CP diet consisting primarily of grass hay, corn, and soybean meal fed to gain 1.25 kg/d. The steers were assigned to four treatments (with or without CTC and 10% or 13% dietary CP in a factorial arrangement) and fed ad libitum amounts of diet for 91 d. Feed intake was determined daily and steers were weighed weekly. Steers were killed at the end of the feeding period for carcass merit determinations. Efficiency of BW gain was greater (P < .05) for steers fed the 13% CP diet than for the 10% CP diet and tended to be less for CTC-steers when the 10% CP diet was fed and greater for the CTC-steers when the 13% CP diet was fed (CTC x dietary CP interaction, P < .10). Feeding CTC increased (P < .01) fat over the longissimus muscle and marbling. This study is interpreted to indicate that the sustained effect of subtherapeutic feeding of CTC to cattle appears to increase fat deposition consistent with a reduced growth hormone and thyroid status reported earlier for these same steers. This would tend to increase energy utilization but may not necessarily produce a measurable increase in BW gain.

Administration, Oral↗
PubMed1999

Increased expression of matrix metalloproteinase-1 in osteocytes precedes bone resorption as stimulated by disuse: evidence for autoregulation of the cell's mechanical environment?

An in vivo animal model of bone adaptation was used to examine a possible role for matrix metalloproteinase-1 in the local mediation of bone remodeling: to corrode the coupling of osteocytes to the matrix in an attempt to autoregulate the cell's perception of its mechanical environment. Twelve young (12-16 months old) skeletally mature turkeys were separated into groups to be studied for stimulus periods of either 3 or 30 days. In each animal, the left ulna was functionally isolated and subjected to either disuse or 3,000 microstrain at 1 Hz for 10 minutes per day. The right ulna remained intact and served as an intra-animal control. No significant differences in bone area were detected at 3 days; however, ulnae subjected to disuse lost 8 +/- 4% (+/-SD) of bone area by 30 days. Over the same period, ulnae subjected to the mechanical stimulus gained 21 +/- 9% of bone area. With use of in situ reverse transcription-polymerase chain reaction, less than 2% of the osteocytes examined from the intact control ulnae stained positively for matrix metalloproteinase-1 mRNA. An antibody raised against matrix metalloproteinase-1 revealed no positively labeled osteocytes in the intact ulnae. This low percentage of osteocytes expressing matrix metalloproteinase-1 mRNA was similar to that seen in ulnae subjected to the osteogenic mechanical stimuli. In contrast, ulnae subjected to either 3 or 30 days of disuse showed evidence of matrix metalloproteinase-1 mRNA activity in a high percentage of osteocytes (89 +/- 5 and 66 +/- 8%, respectively; each time point significantly different from intact ulnae, as well as from each other, p < 0.05). The percentage of osteocytes labeled with the anti-matrix metalloproteinase-1 antibody was also highly elevated following 3 days of disuse (74 +/- 17%). These data demonstrate that an early response of bone to disuse is the upregulation of matrix metalloproteinase-1 activity in osteocytes. It is proposed that this upregulation of collagenase activity is indicative of the cell's degradation of coupling to the matrix, and it thus reflects the osteocyte's regulation of its own mechanical environment. We believe that such autoregulation of the osteocyte's physical environment will accommodate subtle changes in the bone's functional environment without the need to add or resorb bone tissue.

Animals↗
PubMed1999

The New Zealand Socioeconomic Index: developing and validating an occupationally-derived indicator of socio-economic status.

OBJECTIVE: Following revision of the international standard classification (ISCO88), to update and validate on health data an occupationally derived indicator of socio-economic status (SES) adapted to changing occupational and demographic conditions. METHOD: The development of the New Zealand Socioeconomic Index (NZSEI) is based on a 'returns to human capital' model of the stratification process and uses data from the 1991 New Zealand Census (n = 1,051, 926) to generate scores for 97 occupational groups. The construct validation of the scale is carried out on data from the 1992-93 nationwide Household Health Survey (n = 3,000) using three health indicators (self-assessed health, cigarette smoking, general practitioner visits). RESULTS: In general, the results are consistent with expected socio-economic patterns drawn from the literature for the three indicators. CONCLUSIONS: While further work is required on a number of methodological and conceptual issues, the NZSEI provides a robust, standardised and internationally comparable occupational scale of SES for both males and females in either full- or part-time employment. IMPLICATIONS: The NZSEI can be used on routinely collected occupational data. It has a clear conceptual rationale, updates existing SES scales, and provides a link to international standards in SES and occupational classification.

Adult↗
PubMed1999

Assessment of the quality of neonatal echocardiographic images transmitted by ISDN telephone lines.

OBJECTIVE: To assess the quality of echocardiographic images from neonates transmitted over Integrated Service Digital Network 2 (ISDN2) channels. DESIGN: Echocardiographic images were viewed live in real time either by a direct video link or by transmission over the commercial network, using one, two, or three ISDN2 channels. The order of the viewing formats was random and four observers marked each view for potential for provision of complete diagnostic information and quality. SETTING: Cardiology department of tertiary referral centre for paediatric cardiac services. ISDN lines were positioned in two nearby rooms. Telephone connection was through the commercial network and video connection by a direct video cable. PATIENTS: 10 neonates were studied (weight 2600 to 3900 g). In each, nine echocardiographic studies were undertaken to assess imaging (M mode and cross sectional) and Doppler (spectral and colour) quality. RESULTS: No significant differences were found in diagnostic ability between the different formats for M mode, colour, or spectral Doppler studies. For cross sectional imaging the diagnostic information and image quality increased with increasing numbers of ISDN channels. With six channels there was little difference from the directly connected images. CONCLUSIONS: In echocardiographic assessment of the newborn, one or two ISDN2 channels will transmit images of satisfactory quality in many situations but three or more channels are necessary to ensure minimum degradation of the live image.

Echocardiography↗
PubMed1999

Long-term outcome after selective posterior rhizotomy in children with spastic cerebral palsy.

A retrospective analysis of data collected prospectively was performed to determine the long-term outcome of lumbosacral selective posterior rhizotomy (SPR) in children with spastic cerebral palsy (CP). The study population comprised children with spastic CP, who had SPR more than 4 years prior to the time of the study and had quantitative standardized assessments of lower limb spasticity (Ashworth scale), range of motion measured goniometrically, muscle strength (MRC scale) and ambulatory function, both preoperatively and at 1 year after SPR. Children meeting these criteria were reassessed at 5 years after SPR using the same measures. Hip adductor spasticity, hip abduction range of motion and quadriceps strength were chosen as the primary outcome measures for statistical analysis. Of 80 patients who met the entry criteria for the study, 33 completed the 5-year assessments. Significant improvements in spasticity, range of motion and muscle strength were noted both at 1 year and at 5 years after SPR. The preoperative, 1-year and 5-year values were as follows: hip adductor spasticity (Ashworth scale) = 4.1, 2.1, 2.2; hip abduction range of motion (degrees) = 20.4, 39.9, 31.7, and quadriceps strength (MRC scale) = 3.6, 4.0, 4.1. Ambulatory function seemed to be better at 1 and 5 years compared to baseline, but no statistical analysis was done for this secondary outcome measure. It was concluded that improvements in lower limb motor outcome are present at 1 year after SPR, and that these improvements are generally maintained at 5 years.

Biomechanical Phenomena↗
PubMed1999

Effects of oral chlortetracycline and dietary protein level on plasma concentrations of growth hormone and thyroid hormones in beef steers before and after challenge with a combination of thyrotropin-releasing hormone and growth hormone-releasing hormone.

The objective of this study was to determine the effect of a subtherapeutic level of chlortetracycline (CTC) fed to growing beef steers under conditions of limited and adequate dietary protein on plasma concentrations of GH, thyroid-stimulating hormone (TSH), and thyroid hormones before and after an injection of thyrotropin-releasing hormone (TRH) + GHRH. Young beef steers (n = 32; average BW = 285 kg) were assigned to a 2x2 factorial arrangement of treatments of either a 10 or 13% crude protein diet (70% concentrate, 15% wheat straw, and 15% cottonseed hulls) and either a corn meal carrier or carrier + 350 mg of CTC daily top dressed on the diet. Steers were fed ad libitum amounts of diet for 56 d, and a jugular catheter was then placed in each steer in four groups (two steers from each treatment combination per group) during four consecutive days (one group per day). Each steer was injected via the jugular catheter with 1.0 microg/kg BW TRH + .1 microg/kg BW GHRH in 10 mL of saline at 0800. Blood samples were collected at -30, -15, 0, 5, 10, 15, 20, 30, 45, 60, 120, 240, and 360 min after releasing hormone injection. Plasma samples were analyzed for GH, TSH, thyroxine (T4), and triiodothyronine (T3). After 84 d on trial, the steers were slaughtered and the pituitary and samples of liver were collected and analyzed for 5'-deiodinase activity. Feeding CTC attenuated the GH response to releasing hormone challenge by 26% for both area under the response curve (P<.03) and peak response (P<.10). Likewise, CTC attenuated the TSH response to releasing hormone challenge for area under the response curve by 16% (P<.10) and peak response by 33% (P<.02), and attenuated the T4 response for area under the curve by 12% (P<.08) and peak response by 14% (P<.04). Type II deiodinase activity in the pituitary was 36% less (P<.02) in CTC-fed steers than in steers not fed CTC. The results of this study are interpreted to suggest that feeding subtherapeutic levels of CTC to young growing beef cattle attenuates the release of GH and TSH in response to pituitary releasing hormones, suggesting a mechanism by which CTC may influence tissue deposition in cattle.

Animal Nutritional Physiological Phenomena↗
PubMed1998

Enhancement of fracture healing by low intensity ultrasound.

Fracture healing is a highly complex regenerative process that is essentially a replay of developmental events. These events include the action of many different cell types, a myriad of proteins, and active gene expression that in the majority of cases ultimately will restore the bone's natural integrity. Several biologic and biophysical approaches have been introduced to minimize delayed healing and nonunions, some with promising results. One example of such an approach is low intensity pulsed ultrasound, a noninvasive form of mechanical energy transmitted transcutaneously as high frequency acoustical pressure waves in biologic organisms. Numerous in vivo animal studies and perspective double blind placebo controlled clinical trials have shown that low intensity ultrasound is capable of accelerating and augmenting the healing of fresh fractures. Preliminary evidence suggests efficacy in the treatment of delayed healing and nonunions as well. This article reviews the animal and clinical studies that consider the effects of ultrasound on fracture healing, and the in vivo and in vitro work that strives to identify the biologic mechanism(s) responsible for the ultrasound induced enhancement of osteogenesis and fracture healing.

Animals↗
PubMed1997

Pressure regulates osteoclast formation and MCSF expression in marrow culture.

One of the forces generated during skeletal loading is hydrostatic pressure. In the work presented here, the ability of increased pressure to influence recruitment of osteoclasts was evaluated. Murine marrow cultures, with pO2 and pCO2 kept constant, were subjected to either control (1.0 atm) or elevated (1.37 or 2.0 atm) hydrostatic pressure. As compared to control, cultures pressurized for 6 days at 1.37 atm formed less osteoclast-like cells (OCLC) (71 +/- 6% of control, P < 0.0001). A similar degree of inhibition occurred in cultures exposed to pressure during days 2-4 only (62 +/- 6%), while treatment during days 5-7 failed to inhibit the OCLC number relative to control (99 +/- 5%). Delivery of 2.0 atm pressure on days 2-4 generated 52 +/- 4% OCLC compared to control. Since macrophage colony stimulating factor (MCSF)-dependent proliferation of osteoclast precursors occurs during the pressure-sensitive period, semiquantitative RT-PCR for MCSF mRNA was performed after 3 days in 1.37 atm (days 2-4). As compared to controls, pressure caused a decrease in mRNA coding for the membrane bound form of MCSF (71.2 +/- 4% (n = 25, P < or = 0.05), while the MCSF RT-PCR product representing the secreted form showed no consistent change. This lack of response of the soluble MCSF RT-PCR product was expected, as levels of bioassayable MCSF were not altered by pressure. Extrapolating these data to in vivo conditions suggests that load-bearing will inhibit the formation of osteoclasts.

Animals↗
PubMed1997

Role of heat shock proteins in the pathogenesis of cystic fibrosis arthritis.

BACKGROUND: Arthritis is a well recognised complication of cystic fibrosis. The cause of this arthritis is not yet clear but it is likely to be an immunological reaction to one of the many bacterial antigens to which the lungs are exposed. One such group, the heat shock proteins, (hsp), was investigated. These are immunodominant antigens of a wide variety of infectious microorganisms and have varying amino acid chain sequences, some of which are similar to those found in human tissues. METHODS: Antibodies to human hsp 27 and hsp 90 in the serum of patients with cystic fibrosis, with and without arthritis, and in normal age and sex matched healthy controls were measured. The severity of the cystic fibrosis was assessed by lung function tests and chest radiographs. The nature of the organisms colonising the lungs was determined by bacteriological examination of sputum. RESULTS: Higher mean titres of serum IgG anti-human hsp 27 and hsp 90 antibodies were found in 50 patients with cystic fibrosis than in healthy controls (hsp 27, 0.25 (95% CI 0.19 to 0.33) versus 0.05 (95% CI 0.04 to 0.07); hsp 90, 0.27 (95% CI 0.22 to 0.32) versus 0.11 (95% CI 0.08 to 0.14)). These antibodies were higher in patients in whom the lungs were colonised with Pseudomonas aeruginosa than in those without infection (hsp 27, 0.41 (95% CI 0.17 to 0.63) versus 0.18 (95% CI 0.10 to 0.27); hsp 90, 0.37 (95% CI 0.18 to 0.57) versus 0.22 (95% CI 0.16 to 0.29)). The eight patients with cystic fibrosis with arthritis had higher anti-hsp 27 antibodies (0.48 (95% CI 0.13 to 0.92)) than the 42 patients without arthritis (0.22 (95% CI 0.17 to 0.30)). CONCLUSIONS: These findings suggest that the arthritis associated with cystic fibrosis, despite being seronegative for rheumatoid factor, was associated with more severe lung disease and with a greater inflammatory response to heat shock proteins.

Adolescent↗
PubMed1996

Differentiation of the bone-tissue remodeling response to axial and torsional loading in the turkey ulna.

The ability of bone tissue to differentiate between axial and torsional loading was determined with use of a functionally isolated turkey-ulna model of bone adaptation. Surface modeling and intracortical remodeling were quantified after four weeks of 5000 cycles per day of axial loading sufficient to cause 1000 microstrain normal to the long axis of the bone (five ulnae), 5000 cycles per day of torsional loading sufficient to cause 1000 microstrain of shear strain (five ulnae), or disuse (six ulnae). Of these three distinct regimens, only disuse caused a significant change in gross areal properties (12 per cent loss of bone; p < 0.05) as compared with those in the contralateral, intact control ulnae (sixteen ulnae). This finding suggested that both axial and torsional loading conditions were suitable substitutes for functional signals normally responsible for bone homeostasis. However, the intracortical response was strongly dependent on the manner in which the bone was loaded. Axial loading increased the number of intracortical pores by a factor of seven as compared with that in the controls (246 +/- 40.5 compared with 36 +/- 8.5 pores); it also increased the area lost because of porosis as compared with that in the controls (1.39 +/- 0.252 compared with 0.202 +/- 0.062 square millimeter); however, the mean size of the individual pores was similar to that in the controls (0.00565 +/- 0.0019 compared with 0.00561 +/- 0.0029 square millimeter). Conversely, torsional loading failed to increase substantially the number of pores (67 +/- 22.6 pores), the area of bone lost because of porosis (0.352 +/- 0.114 square millimeter), or the size of the pores (0.00525 +/- 0.0035 square millimeter) as compared with those in the controls. Although disuse failed to increase substantially the number of intracortical pores (59 +/- 22.4 pores), significant area (1.05 +/- 0.35 square millimeters; p < 0.05) was lost within the cortex because of a threefold increase in the mean size of each pore (0.0178 +/- 0.0126 square millimeter). It appears that bone tissue can readily differentiate between distinct components of the strain environment, with strain per se necessary to retain coupled formation and resorption, shear strain achieving this goal by maintaining the status quo, and axial strain increasing intracortical turnover but retaining coupling. While it is clear that load influences bone mass and morphology, it is also clear that specific parameters within the strain environment have distinct strategic roles in defining this architecture.

Adaptation, Physiological↗