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Biomedical subjects

R Donnelly

Publications and source records attributed to R Donnelly.

At least 55 records · Page 3Linked to original sources
PubMed2000

Variability of diurnal changes in ambulatory blood pressure and nocturnal dipping status in untreated hypertensive and normotensive subjects.

An absent or diminished blood pressure (BP) fall during sleep (so-called "nondipping") has been associated with a higher risk of cardiovascular complications, but the long-term reproducibility of dipper status and the relationship between diurnal changes in BP and perceived sleep quality have not been previously documented in untreated hypertensive patients. Ambulatory BP (ABP) and dipping status were examined in 79 subjects (69 hypertensives and 10 normotensives) at 0, 6, and 12 months. Fifty-six percent of subjects had no change in their dipping status, the majority (53%) dipping normally on all three occasions. However, 44% of patients had variable dipping status, and normal nighttime dipping in BP was observed more often when patients perceived their sleep quality to be good during the period of ABP recording. These results highlight significant intrasubject variability in the diurnal fluctuations in ABP and dipper status, which may in part reflect day-to-day variations in sleep disturbance during ABP monitoring. Classifying hypertensive patients into dippers or nondippers on the basis of a single ABP recording is unreliable and potentially misleading.

Adult↗
PubMed2000

What is the signal for the posttranslational arginylation of proteins?

The N-terminal, posttranslational arginylation of proteins is ubiquitous in eukaryotic cells. Previous experiments, using purified components of the reaction incubated in the presence of exogenous substrates, have shown that only those proteins containing acidic residues at their N-terminals are arginylation substrates. However, data from experiments that used crude extracts of brain and nerve as the source of the arginylating molecules, suggest that the in vivo targets for arginylation are more complex than those demonstrated using purified components. One of the proposed functions for arginylation is as a signal for protein degradation and proteins that have undergone oxidative damage have been shown to be rapidly degraded. In the present experiments we have tested the hypothesis that the presence of an oxidatively damaged residue in a protein is a signal for its arginylation. These experiments have been performed by adding synthetic oxidized peptides to crude extracts of rat brain, incubating them with [3H]Arg and ATP and assaying for arginylated peptides using RP-HPLC. Results showed that while the oxidized A-chain of insulin was arginylated in this system, confirming previous experiments, other peptides containing oxidized residues were not. When a peptide containing Glu in the N-terminus was incubated under the same conditions it too was not a substrate for arginylation. These findings show that neither the presence of an N-terminal acidic residue nor an oxidized residue alone are sufficient to signal arginylation. Thus, another feature of the oxidized A-chain of insulin is required for arginylation. That feature remains to be identified.

Adenosine Triphosphate↗
PubMed2000

Effects of tumour necrosis factor-alpha and inhibition of protein kinase C on glucose uptake in L6 myoblasts.

Clinical and experimental studies have implicated high circulating levels of the cytokine tumour necrosis factor-alpha (TNF-alpha) in the pathogenesis of insulin resistance, not only in obesity and diabetes, but also in clinical conditions associated with cachexia and sepsis. TNF-alpha impairs insulin-mediated glucose uptake in adipocytes, but because of lipolytic effects the interpretation of clinical studies and the extent to which TNF-alpha affects muscle insulin sensitivity are unclear. In addition, protein kinase C (PKC) has recently been implicated in the mechanism of TNF-alpha-induced insulin resistance. The present study investigated the effects of TNF-alpha and a PKC inhibitor (RO-318220) on basal and insulin-stimulated 2-[(3)H]deoxyglucose uptake in cultured L6 myoblasts. Reverse transcriptase-PCR analysis confirmed that L6 myoblasts express TNF-alpha receptors I and II (p60 and p80). Dose-response curves for glucose uptake were fitted to a quadratic function to derive C(I-150) values (concentration of insulin required to increase glucose uptake by 50%). Incubation with TNF-alpha at 1 or 10 ng/ml for 24 h had no significant effect on basal glucose uptake, insulin sensitivity or maximal insulin responsiveness. C(I-150) values (means+/-S.E.M.) were as follows: basal, 91.2+/-13 nM; 1 ng/ml TNF-alpha, 102+/-12 nM; and basal, 70.8+/-13 nM; 10 ng/ml TNF-alpha, 43.7+/-40 nM. PKC inhibition markedly attenuated glucose uptake, but there was no difference in insulin sensitivity with RO-318220 alone compared with RO-318220+TNF-alpha. In conclusion, although increased TNF-alpha expression and plasma concentrations have been implicated in the pathogenesis of insulin resistance in various clinical states, there is no evidence that TNF-alpha impairs insulin-stimulated glucose uptake in a skeletal-muscle-derived cell line.

Animals↗
PubMed2000

Pharmacokinetics of epimeric budesonide and fluticasone propionate after repeat dose inhalation--intersubject variability in systemic absorption from the lung.

AIMS: Pharmacokinetic variability is likely to be a significant factor contributing to the interindividual differences in dose requirements, anti-inflammatory response and side-effects with inhaled corticosteroids (ICS), but there is limited information about the disposition of ICS during regular dosing with a pressurized metered dose inhaler (pMDI). This study uses a mixed effects modelling approach to quantify and compare the interindividual variability in pharmacokinetics of epimeric budesonide (BUD) and fluticasone propionate (FP) after repeat-dose inhalation. METHODS: This pharmacokinetic substudy was part of a previously published open-label, randomised, placebo-controlled, 7-period crossover study to evaluate the short-term effects on plasma cortisol levels of inhaled BUD (400, 800, 1600 microg twice daily) and FP (375, 750, 1000 microg twice daily) via pMDI in a group of healthy male volunteers. On the fifth day of each high-dose treatment period (BUD 1600 microg twice daily and FP 1000 microg twice daily), venous blood samples were collected in nine subjects prior to the last dose and at 15 min, 30 min, 1, 2, 4, 6 and 8 h postdose for measurement of plasma drug concentrations to determine the pharmacokinetics of epimeric BUD and FP following inhalation. Non-compartmental analysis and a mixed effects model were used to characterize the disposition profiles. RESULTS: Both drugs had a rapid absorption half-life (BUD 10 min vs FP 11.3 min), but quite different elimination half-lives (BUD 2.4 h vs FP 7.8 h). Although there were intraindividual differences in the handling of the 22R-and 22S-epimers of BUD, there were no consistent pharmacokinetic differences between the two enantiomers in the group as a whole. Consistent with previous reports of FP's higher volume of distribution (V) and lower systemic bioavailability (F), the V/F ratio was lower for BUD than FP (498 l vs 8100 l). The parameter with the greatest interindividual variability for both BUD and FP was the rate of systemic absorption from the lung. CONCLUSIONS: This is the first report describing the pharmacokinetics of epimeric BUD and FP after repeat dose inhalation via pMDI. Three observations may be of clinical relevance: (1) there is considerable intersubject variability in the rate of absorption of both drugs from the lung; (2) in some individuals there was a long t(1/2),z for BUD, resulting in higher and more sustained plasma drug levels in the 4-12 h postdose period than would be predicted from single-dose pharmacokinetic data; and (3) there is evidence of diurnal variation in FP pharmacokinetics, with higher-than-expected plasma drug concentrations in the morning compared with the evening.

Administration, Inhalation↗
PubMed2000

Trandolapril does not improve insulin sensitivity in patients with hypertension and type 2 diabetes: a double-blind, placebo-controlled crossover trial.

Angiotensin-converting enzyme (ACE) inhibitors are increasingly used as first-line therapy for hypertension in type 2 diabetes mellitus and are widely believed to improve insulin sensitivity (M). However, the evidence for the latter effect does not stand close scrutiny. We have assessed the effect of the ACE inhibitor trandolapril on M in 16 patients (mean +/- SD age, 58 +/- 10.6 yr) with mild-to-moderate essential hypertension (initial blood pressure, 173 +/- 14.5/93 +/- 8.0 mm Hg), obesity (body mass index, 30 +/- 5.4 kg/m2), and impaired glucose intolerance (n = 4) or type 2 diabetes (n = 12) in a double-blind, placebo-controlled crossover design. All patients underwent three 3-h euglycemic hyperinsulinemic clamp studies (soluble insulin, 1.5 mU/kg x min) after a 2-week placebo run-in and at the end of two 4-week periods of treatment with 2 mg trandolapril or placebo (2-week washout). M (mean +/- SD) did not change with trandolapril: placebo (run-in), 5.2 +/- 1.98 mg/kg x min; placebo, 5.3 +/- 1.70 mg/kg x min; trandolapril, 5.1 +/- 1.65 mg/kg x min; P = 0.58; 95% confidence intervals, -0.74, 0.43 (trandolapril vs. placebo); 95% power to exclude an 8% increase in M. In conclusion, trandolapril had no clinically relevant effect on M in patients with hypertension and type 2 diabetes. Previous reports of improved M during ACE inhibitor treatment may be attributable to suboptimal study design and/or use of surrogate measures of M.

Adult↗
PubMed2000

Possible interactions between angiotensin II and insulin: effects on glucose and lipid metabolism in vivo and in vitro.

Angiotensin II (ANGII) increases insulin sensitivity in diabetic and non-diabetic subjects, even at subpressor doses, and because there is 'crosstalk' between ANGII and insulin-signaling pathways the underlying mechanism may not be due solely to changes in regional blood flow. A series of experimental studies was undertaken to evaluate the effects of ANGII on glucose and lipid metabolism in vivo and in vitro. Groups of fructose-fed, insulin-resistant Sprague-Dawley (SD) rats were pre-treated with 0.3 mg/kg per day of the AT(1)-receptor antagonist L-158 809 (n=16), or vehicle (n=16), by oral gavage. This was prior to an oral glucose tolerance test (day 5) and measurement of the effects of ANGII infusion (20 ng/kg per min i.v. for 3 h) on whole-body insulin sensitivity using the insulin suppression test (day 7). The effect of ANGII infusion on total triglyceride secretion rate (TGSR) was evaluated in normal SD rats pretreated for 7 days with L-158 809 (n=12) or vehicle (n=12). AT(1)- and AT(2)- receptor mRNA expression and [(3)H]2-deoxyglucose uptake were assessed in cultured L6 myoblasts. Short-term treatment with L-158 809 had no effect on glucose tolerance or fasting triglyceride levels in fructose-fed rats. ANGII infusion had no effect on insulin sensitivity in fructose-fed rats pretreated with vehicle (steady-state plasma glucose (SSPG) values 8.1+/-1.6 vs 8. 4+/-0.4 mmol/l), but pretreatment with L-158 809 resulted in ANGII having a modest insulin antagonist effect in this insulin-resistant model (SSPG values 9.6+/-0.3 vs 7.1+/-0.6, P<0.03). ANGII infusion had no significant effect on TGSR (e.g. 24.6+/-1.4 vs 28.4+/-0.9 mg/100 g per h in vehicle-treated animals). RT-PCR analysis showed that L6 cells express both AT(1)- and AT(2)-receptor mRNA. Incubation with ANGII (10(-9) and 10(-8) M) had no significant effect on the dose-response curve for insulin-stimulated [(3)H]2-deoxyglucose uptake. For example, C(I200) values (dose of insulin required to increase glucose uptake by 200%) were 4.5 x 10(-9) M (control) vs 3.9 x 10(-9) M and 6.2 x 10(-9) M, whereas the positive control (glucagon-like peptide-1) increased insulin sensitivity. Thus, ANGII infusion may have a modest insulin antagonist effect on glucose disposal in insulin-resistant fructose-fed rats pretreated with an AT(1)-blocker, but ANGII has no effect on TGSR or in vitro glucose uptake in L6 myoblasts. These findings are relevant to recent clinical discussions about the metabolic effects of ANGII and renin-angiotensin system blockade.

Analysis of Variance↗
PubMed2000

Prenatal testing for late infantile neuronal ceroid lipofuscinosis.

Classic late infantile neuronal ceroid lipofuscinosis (LINCL) is a neurodegenerative disease in which autofluorescent "curvilinear" storage bodies accumulate in tissues from affected patients. Recently, the LINCL gene (CLN2) has been found to code for a pepstatin-insensitive lysosomal protease whose activity is deficient in LINCL specimens. We report the first 2 cases of successful prenatal testing for LINCL by using DNA and enzyme-based methods on amniocytes, and describe a new private mutation in one of the families analyzed. These approaches allow definitive prenatal diagnosis and represent a significant improvement over previous pathological methods.

Adult↗
PubMed1999

Tissue- and isoform-specific effects of aging in rats on protein kinase C in insulin-sensitive tissues.

The mechanisms responsible for the age-related decline in insulin sensitivity have not been clearly identified, but activation of the diacylglycerol/protein kinase C (PKC) signalling pathway (often confined to individual isoforms of PKC) has recently been implicated in the pathogenesis of other insulin-resistant states in both humans and animal models. Fasting serum glucose, insulin and triacylglycerol (triglyceride) concentrations, and results of oral glucose tolerance tests, were compared in groups of 6-week-old (n=8) and 6-month-old (n=8) Sprague-Dawley rats. Insulin-responsive tissues (liver, soleus muscle and epididymal fat pad) were collected to compare levels of diacylglycerol, PKC enzyme activity and protein expression of individual PKC isoforms in cytosol and membrane fractions. The older group were heavier (556+/-14 g, compared with 188+/-7 g) and relatively insulin-resistant and hyperinsulinaemic (477+/-73 pM compared with 293+/-51 pM; P<0.05) compared with young rats; they also had greater areas under the serum glucose (old, 20. 3+/-1.1; young, 17.3+/-0.7 mmol.h(-1).l(-1)) and insulin (old, 1254+/-76; young, 721+/-113 mmol.h(-1).l(-1)) profiles following an oral glucose tolerance test, and significantly higher fasting triacylglycerol levels (old, 1.24+/-0.06 mM; young, 0.92+/-0.07 mM; P<0.01). There were no age-related differences in diacylglycerol levels or PKC activity in muscle and liver, but membrane-associated PKC activity was 2.5-fold higher in the adipose tissue of older rats (101+/-19 compared with 40+/-5 pmol.min(-1).mg(-1) protein; P<0.05) due to increased translocation of PKC-beta(I), -beta(II) and -epsilon. Thus insulin resistance due to normal aging is associated with tissue- and isoform-specific changes in diacylglycerol/PKC signalling. In contrast with diabetes and dietary-induced insulin resistance, there were no changes in diacylglycerol/PKC signalling in skeletal muscle and liver, but isoform-specific translocation and higher PKC activity in adipose tissue may blunt the insulin-mediated inhibition of lipolysis and contribute to the increased triacylglycerol levels observed in older animals.

Adipose Tissue↗
PubMed1999

Protein kinase C isoforms in human airway smooth muscle cells: activation of PKC-zeta during proliferation.

Protein kinase C (PKC) is implicated in the regulation of smooth muscle contractility and growth. We have previously described the pattern of isoform expression of PKC in canine airway smooth muscle. This study identified the isoforms present in human cultured airway smooth muscle cells and also addressed the question of whether mitogenesis in these cells is associated with changes in a specific isoform, PKC-zeta. Western blot analysis revealed the presence of PKC-alpha, -betaI, and -betaII of the conventional group; PKC-delta, -theta, -epsilon, and -eta of the novel group; and PKC-zeta, -mu, and -iota of the atypical group. There was a significant increase in density of the Western blot for PKC-zeta in cells proliferating in response to 10% fetal bovine serum (FBS) to 372 +/- 115% of control values (P < 0.05; n = 3 patients) in the cytosolic fraction. Platelet-derived growth factor (PDGF) produced increases in PKC-zeta in both the cytosolic and membrane fractions to 210 +/- 49 and 443 +/- 227%, respectively, of control values (P < 0.05; n = 4 patients). There was no change in expression of PKC-alpha, -betaI, -betaII, -theta, -epsilon, -eta, -delta, or -iota in response to the same stimuli. PGE2 (1 microM) added to the cells 30 min before PDGF reduced incorporation of [3H]thymidine from 5,580 +/- 633 (SE) to 3, 980 +/- 126 dpm (P < 0.05; n = 3 patients) and, in addition, reduced expression of PKC-zeta in the membrane fraction as determined by Western blotting from 266 +/- 66 to 110 +/- 4% of control values (P < 0.05; n = 3 patients). PKC-zeta activity in stimulated cells (10% FBS), as assessed by immunoprecipitation and phosphorylation of glycogen synthase peptide, was approximately 3-fold greater than that in unstimulated cells, and the amount of PKC-zeta protein correlated with isoenzyme activity (r2 = 0.91; P < 0.02; n = 4 patients). In conclusion, this study 1) provides the first description of which isoforms of PKC are present in human cultured airway smooth muscle cells and 2) shows that proliferation of these cells is associated with upregulation of PKC-zeta. Whether activation of PKC-zeta is a primary or secondary event in airway smooth muscle cell proliferation remains to be determined.

Bronchi↗
PubMed1999

Tissue and isoform-selective activation of protein kinase C in insulin-resistant obese Zucker rats - effects of feeding.

The mechanisms of insulin resistance in the obese Zucker rat have not been clearly established but increased diacylglycerol-protein kinase C (DAG-PKC) signalling has been associated with decreased glucose utilisation in states of insulin resistance and non-insulin-dependent diabetes mellitus. The purpose of this study was to characterise tissue- and isoform-selective differences in DAG-PKC signalling in insulin-sensitive tissues from obese Zucker rats, and to assess the effects of feeding on DAG-PKC pathways. Groups of male obese (fa/fa, n=24) and lean (fa/-, n=24) Zucker rats were studied after baseline measurements of fasting serum glucose, triglycerides, insulin and oral glucose tolerance tests. Liver, epididymal fat and soleus muscle samples were obtained from fed and overnight-fasted rats for measurements of DAG, PKC activity and individual PKC isoforms in cytosol and membrane fractions. Obese rats were heavier (488+/-7 vs 315+/-9 g) with fasting hyperglycaemia (10.5+/-0.8 vs 7.7+/-0.1 mM) and hyperinsulinaemia (7167+/-363 vs 251+/-62 pM) relative to lean controls. In fasted rats, PKC activity in the membrane fraction of liver was significantly higher in the obese group (174+/-16 vs 108+/-12 pmol/min/mg protein, P<0.05) but there were no differences in muscle and fat. The fed state was associated with increased DAG levels and threefold higher PKC activity in muscle tissue of obese rats, and increased expression of the major muscle isoforms, PKC-theta and PKC-epsilon: e.g. PKC activity in the membrane fraction of muscle from obese animals was 283+/-42 (fed) vs 107+/-20 pmol/min/mg protein (fasting) compared with 197+/-27 (fed) and 154+/-21 pmol/min/mg protein (fasting) in lean rats. In conclusion, hepatic PKC activity is higher in obese rats under basal fasting conditions and feeding-induced activation of DAG-PKC signalling occurs selectively in muscle of obese (fa/fa) rats due to increased DAG-mediated activation and/or synthesis of PKC-theta and PKC-epsilon. These changes in PKC are likely to exacerbate the hyperglycaemia and hypertriglyceridaemia associated with obesity-induced diabetes.

Animals↗
PubMed1999

Clinical implications of indapamide sustained release 1.5 mg in hypertension.

Recent international guidelines on the detection, clinical assessment and management of patients with hypertension have highlighted a number of themes that should be incorporated into routine clinical practice. First, although antihypertensive therapy is having a major impact on reducing the incidence of coronary heart disease, cerebrovascular disease and heart failure, community surveys show that most hypertensive patients remain untreated or have suboptimal blood pressure control. Second, the guidelines have emphasised the importance of making an overall assessment of individual patients to gauge their absolute risk of a cardiovascular event; risk factors include not only blood pressure but also target organ damage, the presence of coexisting symptomatic vascular disease and the number of associated cardiovascular risk factors. Patients at the highest risk, especially those with diabetes, the elderly and patients with target organ damage, merit vigorous antihypertensive therapy, and such patients often require treatment with more than one drug to achieve target levels of blood pressure (< 135/80 mm Hg). An additional important theme in recent guidelines has been a move towards using lower dosages and therapies that provide 24-hour blood pressure control with once-daily administration. Since diuretics have been reaffirmed as evidence-based first-line therapy in a broad spectrum of patients with hypertension, especially the elderly, a new lower dosage sustained release formulation of indapamide has been developed (indapamide SR 1.5 mg). Recent multicentre European clinical trials have defined the efficacy and tolerability of indapamide SR 1.5 mg, both relative to other antihypertensive drugs and in key subgroups of patients. Indapamide SR 1.5 mg has an antihypertensive effect, maintained throughout the 24-hour administration interval, equivalent to that of immediate release indapamide 2.5 mg, but the new formulation has even less effect on circulating K+ levels. Indapamide SR 1.5 mg is at least as effective as amlodipine or hydrochlorothiazide. In patients with left ventricular hypertrophy (LVH), a comparative study of indapamide SR 1.5 mg and enalapril (the LIVE study) used a rigorous unique study design with blinded reading of echocardiograms to show that after 1 year the ACE inhibitor had no significant effect on LVH regression, whereas indapamide SR 1.5 mg produced significant reductions in left ventricular mass index. Diuretic-based therapy for hypertension has been reaffirmed in international guidelines as effective first-line therapy, especially in the elderly and patients with LVH. Indapamide SR 1.5 mg shows an improved efficacy-tolerability profile, with impressive 24-hour effects on blood pressure, important ancillary properties with regard to LVH and cardiovascular protection.

Age Factors↗