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Biomedical subjects

A Keogh

Publications and source records attributed to A Keogh.

At least 19 recordsLinked to original sources
PubMed2005

Confocal laser scanning microscopy in orthopaedic research.

Confocal laser scanning microscopy (CLSM) is a type of high-resolution fluorescence microscopy that overcomes the limitations of conventional widefield microscopy and facilitates the generation of high-resolution 3D images from relatively thick sections of tissue. As a comparatively non-destructive imaging technique, CLSM facilitates the in situ characterization of tissue microstructure. Images generated by CLSM have been utilized for the study of articular cartilage, bone, muscle, tendon, ligament and menisci by the foremost research groups in the field of orthopaedics including those teams headed by Bush, Errington, Guilak, Hall, Hunziker, Knight, Mow, Poole, Ratcliffe and White. Recent evolutions in techniques and technologies have facilitated a relatively widespread adoption of this imaging modality, with increased "user friendliness" and flexibility. Applications of CLSM also exist in the rapidly advancing field of orthopaedic implants and in the investigation of joint lubrication.

Animals↗
PubMed2001

Nuclear membrane proteins in failing human dilated cardiomyopathy.

Emerin (34 kDa) is a 254 amino acid protein located on the cytoplasmic surface of the inner nuclear membrane in cardiac muscle. It interacts with nuclear lamins and nuclear actin. Emerin is usually completely absent in Emery-Dreifuss muscular dystrophy, a condition that also manifests in the heart. Nuclear lamins are specialized nuclear proteins that line the inner nuclear membrane. Two isoforms, lamin A and C, differ in their C-terminal amino acids. Both are important in apoptosis and are degraded by caspase enzymes. Mutations in the rod domain of the lamin A/C gene are known to cause dilated cardiomyopathy (DCM) (Fatkin et al. New Engl. J. Med. 1999, 351, 1715-1724). We have used Western blots to detect emerin and lamin A/C in left ventricles from both nondiseased and failing DCM samples. The lamins form dimers, however it is not known if they are homodimers and / or heterodimers. In this report we compare and quantify expression levels of emerin from samples of left ventricles from ten failing DCM patients and five nondiseased (donor) hearts. We observed three lamin bands that suggest the expression of the three isoforms of the A-type lamin gene, lamin A, lamin C and lamin C2 (Ye et al. Subcellular Biochem. 1998, 31, 587-610). Preliminary data show that both lamin isoforms and emerin are present.

Blotting, Western↗
PubMed2001

Profiling beds versus standard hospital beds: effects on pressure ulcer incidence outcomes.

Most standard hospital beds are flat based with a pull-out backrest, resulting in a tendency for the patient to slide down the bed. This study aimed to compare the outcome for patients at high risk of developing pressure ulcers nursed on either this type of bed or an electrically operated, multi-sectioned profiling bed. A total of 100 patients were randomly assigned either to the profiling bed with a pressure-reducing foam mattress (experimental group) or a flat-based bed with an appropriate pressure-redistributing mattress (control group) for a maximum of 10 days. Risk status and pressure damage were assessed daily. Both a patient and a nurse questionnaire were completed. Data from 70 patients who participated in the study for five days or more were included in the analysis. Pressure ulcer incidence was 0% in both groups. All patients (35) in the experimental group were able to maintain a sitting position compared with only 12/35 in the control group (p = 0.0001). While the questionnaire results suggest there were significant differences in postural control and ease of transfer between patients in the two groups, it was not possible to map this to pressure ulcer formation. Poor recruitment into the study was due to the 'blocking' of electric beds by heavily dependent patients who did not meet the inclusion criteria, precluding a significant result in terms of pressure ulcer outcomes. This nurse-led use of the profiling beds was examined alongside the main study to investigate why they were allocated in this way.

Adult↗
PubMed2001

Protective effect of short-tem calcitriol or cyclical etidronate on bone loss after cardiac or lung transplantation.

Bone loss is most rapid in the immediate period after cardiac or lung transplantation. This randomized study compared the efficacy of 6 months of treatment with either calcitriol (1,25-dihydroxyvitamin D3; 0.5 microg/day) or two cycles of etidronate plus calcium in preventing bone loss in 41 patients undergoing cardiac or lung transplantation. Patients were followed for 18 months after cessation of treatment. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA). There were no significant differences between groups with respect to age or cumulative dose of prednis(ol)one or cyclosporin over the 2 years. Bone loss did not differ between groups after 6 months and, despite 6 months prophylaxis with either agent, bone loss was significant in both groups at 6 months and 12 months. However, compared with an untreated reference group, both therapies offered significant protection at 6 months and etidronate provided significant protective carryover after therapy had been discontinued. These data suggest short-term prophylaxis with calcitriol or cyclical etidronate is partially effective in reducing bone loss after cardiac or lung transplantation but treatment needs to be continued for a longer term.

Adrenal Cortex Hormones↗
PubMed2000

Determination of P2X1alpha-sarcoglycan (adhalin) expression levels in failing human dilated cardiomyopathic left ventricles.

This study is concerned with the molecular basis of human idiopathic dilated cardiomyopathy (DCM). This disorder affects the entire heart including both atria and ventricles. It is characterized by a progressive dilatation of the ventricles and loss of contractile power that results in an impaired cardiac output. Changes in cellular levels of dystrophin have been reported in patients with muscular dystrophies (Beckers and Duchenne) which manifest as DCM. However, previous studies using Western blots dos Remedios et al., Electrophoresis 1996, 17, 235-238) of samples of left ventricles from DCM patients showed no abnormalities in dystrophin content. P2X receptors are ATP-gated cation channels located in the sarcolemma. They are upregulated by a factor of about two in the atria of DCM patients compared with nondiseased control samples. A dystrophin-associated protein, alpha-sarcoglycan, has recently been shown to be an ecto-ATPase (an extracellular ATPase) capable of regulating ATP concentrations in the space between the cardiomyocytes. In this report we examine the relationship between changes in P2X1 receptors in left ventricle samples from DCM patients and the concentration of alpha-sarcoglycan. We found no evidence for upregulation of P2X1 receptors nor was the expression of alpha-sarcoglycan significantly altered.

Cardiomyopathy, Dilated↗
PubMed2000

Efficacy and safety of pravastatin vs simvastatin after cardiac transplantation.

Prior studies of cardiac transplant recipients have shown that pravastatin reduces 12-month rejection and mortality after cardiac transplantation and simvastatin reduces 4-year mortality, low-density lipoprotein (LDL) cholesterol levels, and intimal thickening. In a 12-month observational study, cardiac transplant recipients received open-label pravastatin 40 mg (n = 42) or simvastatin 20 mg daily (n = 45) on an alternating basis from the time of transplantation. Lipid levels, safety, and post-transplant outcomes were compared. We found no significant differences in total LDL or high-density lipoprotein cholesterol, triglycerides, linearized infection or rejection rates, liver function tests, or immunosuppressant dosages between groups at 1, 3, 6, or 12 months. Rhabdomyolysis or myositis occurred only in patients on simvastatin (n = 6, 13.3%) with no episodes for patients on pravastatin (p = 0. 032). Survival at 12 months on an actual treatment basis was 97.6% for patients on pravastatin and 83.7% for those on simvastatin (p = 0.078). Immunosuppression-related deaths occurred in only 2.4% (1 patient) on pravastatin vs 15.6% (n = 7) on simvastatin (p = 0.06). Pravastatin and simvastatin resulted in comparable lipid profiles. Pravastatin use was however free from the high rates of rhabdomyolysis and myositis seen with simvastatin use. Pravastatin was additionally associated with a trend toward superior survival, attributable to fewer immunosuppression-related deaths. For safety and pharmacokinetic reasons, pravastatin should be considered the statin of choice after heart transplantation.

Cholesterol, HDL↗
PubMed2000

Pulmonary vascular resistance and reactivity in children with end-stage cardiomyopathy.

Pulmonary vascular resistance (PVR) and reactivity were compared in 63 children with end-stage cardiomyopathy (CM) referred for cardiac transplantation. Diagnostic category of CM was the sole determinant of PVR. Compared with other patients, children with restrictive CM were younger at diagnosis and had a significantly higher pulmonary vascular resistance index (PVRI). Children with a baseline PVRI of up to 11.8 units per meter squared (U.m(2)) who showed reactivity underwent successful orthotopic cardiac transplantation.

Adolescent↗
PubMed2000

Predicting the occurrence of diabetes mellitus in recipients of heart transplants.

AIMS: To establish the incidence of post-transplant diabetes mellitus (PTDM) and factors predictive of its development. METHODS: This was a retrospective review (using hospital records and transplant database) of 97 consecutive adult patients who underwent cardiac transplantation at St Vincent's Hospital, Sydney, Australia. RESULTS: Mean follow-up was 27 months. Excluding five patients who had pre-existing diabetes, the cumulative incidence of PTDM was 15.7%. Pre-transplant random blood glucose (5.6 +/- 0.8 vs. 5.2 +/- 0.6 mmol/l, P<0.05), family history (46% vs. 15%, P<0.05) and a continuing requirement for insulin on the second post-transplant day (54% vs. 15%, P< 0.01) differed in those who developed PTDM as opposed to those who remained free of diabetes. Patients who developed PTDM had received slightly higher mean doses of prednisolone at three months (0.21 +/- 0.03 vs. 0.19 +/- 0.03 mg. kg(-1)/day(-1), P<0.01). Of the factors identifiable prior to initial hospital discharge, only family history of diabetes mellitus and second post-transplant day insulin requirement independently predicted the occurrence of PTDM. CONCLUSIONS: A family history of diabetes and the need for insulin beyond the first 24 h after transplantation are factors identifiable prior to hospital discharge, which predict patients at risk of developing PTDM. In such patients, consideration to minimizing the dose of glucocorticoids should be given where possible.

Adult↗
PubMed2000

Effect of calcitriol on bone loss after cardiac or lung transplantation.

Rapid bone loss after cardiac and lung transplantation results in an increased risk of osteoporotic fracture. This study examined the efficacy of treatment with calcitriol (1,25-dihydroxyvitamin D3) in preventing bone loss in patients undergoing cardiac or lung transplantation. In this 2-year double-blind, stratified study, 65 patients undergoing cardiac or single lung transplantation were randomly allocated to receive either placebo or calcitriol (0.5-0.75 microg/day), the latter for either 12 months or 24 months. All patients received 600 mg calcium/day. Bone mineral density (BMD) was measured every 6 months for 2 years by dual-energy X-ray absorptiometry. There was no significant difference between groups with respect to age or cumulative dose of prednis(ol)one or cyclosporine over the 2 years. Bone loss at the proximal femur was significantly reduced or prevented at all three sites by treatment with calcitriol for 2 years compared with treatment with calcium alone. Treatment with calcitriol for 12 months followed by calcium for 12 months resulted in similar proximal femoral bone loss to that seen in those patients treated with calcium for 24 months, suggesting calcitriol prophylaxis needs to be continued beyond 12 months. At the lumbar spine, there were no significant differences in BMD between groups. Over a period of 2 years, 22 new vertebral fractures/deformities occurred in 4 patients treated with calcium alone compared with one new vertebral fracture in 1 patient treated with calcitriol. Because the sample size was too low to provide reliable interpretation of vertebral fracture rates, this difference is likely a chance result. Mild hypercalcemia was common with calcitriol therapy, as was mild hypercalciuria (59% of patients vs. 10% controls), but there were no significant differences between groups in serum creatinine after 2 years. These data suggest calcitriol has a role in reducing proximal femur bone loss after cardiac or lung transplantation but treatment needs to be continued beyond 1 year.

Adrenal Cortex Hormones↗
PubMed1999

Increase in expression of P2X1 receptors in the atria of patients suffering from dilated cardiomyopathy.

P2X1 receptors are ATP-sensitive ligand-gated cation-selective channels abundant in smooth muscle tissues such as bladder and vas deferens. They have also been detected in the central and peripheral nervous system and in heart tissue. We have earlier reported distinct changes in the expression of the PX1 subtype of P2X receptors in hearts of patients suffering from dilated cardiomyopathy (DCM). The study was, however, based on Western blots from only five DCM samples and three control hearts. Moreover, the antibody was directed against a peptide derived from the sequence of rat P2X1. In the present project we have examined larger groups of both DCM and control hearts (n = 14 and 11, respectively). Furthermore, the antibody used in this paper differs significantly from the one used in our previous report. The present antibody was raised against an 18-residue peptide sequence (Lys 68-84 Val) derived from the human P2X1 sequence. Most of the label in the Western blots was concentrated over a triplet of bands migrating with an apparent Mr of about 45,000. Quantitative densitometry indicated that this band was more strongly expressed (by approximately 80%) in DCM hearts compared with the controls.

Adolescent↗
PubMed1999

Idoxifene derivatives are less reactive to DNA than tamoxifen derivatives, both chemically and in human and rat liver cells.

The drug tamoxifen shows evidence of genotoxicity, and induces liver tumours in rats. Covalent DNA adducts have been detected in the liver of rats treated with tamoxifen, and these arise through metabolism at the alpha-position to give an ester which reacts with DNA. (E)-1-(4-iodophenyl)-2-phenyl-1-[4-(2-pyrrolidinoethoxy)phenyl]-but-1-en e (idoxifene) is an analogue of tamoxifen in which formation of DNA adducts is greatly reduced; we could not detect any adducts in the DNA of cultured rat hepatocytes treated with 10 microM idoxifene, after analysis by the 32P-post-labelling method. The metabolite (Z)-4-(4-iodophenyl)-4-[4-(2-pyrrolidinoethoxy)phenyl]-3-phenyl-3-but en-2-ol (alpha-hydroxyidoxifene) gave adducts in rat hepatocytes, but far fewer than the corresponding tamoxifen metabolite. In human hepatocytes, neither idoxifene nor tamoxifen induced detectable levels of DNA adducts. We prepared the alpha-acetoxy ester of idoxifene as a model for the ultimate reactive metabolite formed in rat liver. It was less reactive than alpha-acetoxytamoxifen, as might be expected on mechanistic grounds. It reacted with DNA in the same way, to give adducts which were probably N2-alkyldeoxyguanosines, but to a lower extent. All these results indicate that idoxifene is much less genotoxic than tamoxifen, and should therefore be a safer drug.

Animals↗
PubMed1999

Cyclosporine plasma unbound fraction in heart and lung transplantation recipients.

To investigate the variability in the unbound fraction (fu) of cyclosporine in recipients of heart, heart-lung, and lung transplantation, cyclosporine fu was determined ex vivo in plasma by equilibrium dialysis. In a retrospective study, 260 samples of plasma (one to seven per patient) were obtained from 89 heart (86%), lung (9%), and heart-lung (5%) transplant patients. The unbound fraction (x100) of cyclosporine ranged from 0.52% to 3.94%, with an overall mean of 1.53%+/-0.375% (SD). The mean percentage unbound for individual patients ranged from 0.71% to 1.98%, giving a 2.8-fold interpatient variation. In heart transplant recipients (66 patients), the values of fu were significantly lower (p < 0.01) during more severe rejection episodes, which required antirejection treatment (endomycardial biopsy result of grade 3a and higher) than in the absence of rejection (grade 0) or during grade la rejections. The value of fu did not vary with organ transplanted (p = 0.35) or etiology of organ failure (p = 0.32). Cyclosporine fu was negatively correlated with the age of the patient (r = -0.18, p < 0.05). Correlations were not observed between fu and blood biochemical and cytologic indices. However, fu was significantly lower (p < 0.01) in hypercholesterolemic transplant recipients (1.37+/-0.52%) than in normocholesterolemic patients (1.60+/-0.63%). Administration of simvastatin resulted in a significant increase in the mean fu from 1.40+/-0.09%) to 1.82+/-0.13% (paired t test, n = 13; p < 0.01). In patients who received ketoconazole, fu was not different from controls. These findings suggest that the level of cyclosporine fu may be an important determinant of immunosuppressive activity of cyclosporine. Moreover, the variation in fu could be strongly related to the concentration of serum lipoproteins; interpretation of the results of cyclosporine monitoring thus requires consideration of the lipidemic status of the patient.

Adolescent↗
PubMed1998

A randomized active-controlled trial of mycophenolate mofetil in heart transplant recipients. Mycophenolate Mofetil Investigators.

BACKGROUND: After heart transplantation, 1-year and 5-year survival rates are 79% and 63%, respectively, with rejection, infection, and allograft coronary artery disease accounting for the majority of deaths. Mycophenolate mofetil (MMF), an inhibitor of the de novo pathway for purine biosynthesis, decreases rejection in animals and in human renal transplantation. METHODS: In a double-blind, active-controlled trial, 28 centers randomized 650 patients undergoing their first heart transplant to receive MMF (3000 mg/day) or azathioprine (1.5-3 mg/kg/day), in addition to cyclosporine and corticosteroids. Rejection and survival data were obtained for 6 and 12 months, respectively. Because 11% of the patients withdrew before receiving study drug, data were analyzed on all randomized patients (enrolled patients) and on patients who received study medications (treated patients). RESULTS: Survival and rejection were similar in enrolled patients (MMF, n=327; azathioprine, n=323). In treated patients (MMF, n=289; azathioprine, n=289), the MMF group compared with the azathioprine group was associated with significant reduction in mortality at 1 year (18 [6.2%] versus 33 deaths [11.4%]; P=0.031) and a significant reduction in the requirement for rejection treatment (65.7% versus 73.7%; P=0.026). There was a trend for fewer MMF patients to have > or = grade 3A rejection (45.0% versus 52.9%; P=0.055) or require the murine monoclonal anti-CD3 antibody or antithymocyte globulin (15.2% versus 21.1%; P=0.061). Opportunistic infections, mostly herpes simplex, were more common in the MMF group (53.3% versus 43.6%; P=0.025). CONCLUSIONS: Substitution of MMF for azathioprine may reduce mortality and rejection in the first year after cardiac transplantation.

Aged↗
PubMed1998

Alterations in the expression of P2X1 receptors in failing and nondiseased human atria.

This is the first report of the analysis of the ATP-specific P2X1 receptor subunit in human hearts. We have examined homogenate samples of human left atria for the presence of P2X1 receptors using Western blots. Anti-P2X1 immunoreactivity was detected in populations of nondiseased atria as well as in atria from explanted hearts from patients with terminally failing heart conditions such as dilated cardiomyopathy. At least three groups of P2X1 immunoreactive proteins were detected in the Western blots with approximate molecular mass values of 50, 70, and 160 kDa. We report changes in expression of their 50 and 70 kDa components. These changes may be related to the type of deficit in these hearts since the changes have been observed in hearts with decreased ejection fractions characteristic of dilated cardiomyopathy.

Animals↗