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Biomedical subjects

S M Donnelly

Publications and source records attributed to S M Donnelly.

At least 19 recordsLinked to original sources
PubMed2001

Losartan may modulate erythropoietin production.

Erythropoietin (Epo) is distinct amongst haematopoietic hormones, in that it is produced remote from the bone marrow. The tissue oxygen pressure required to trigger the Epo gene under physiological conditions is uniquely sited at a restricted area in the kidney termed the critmeter. Angiotensin II (Ang II) increases sodium reabsorption and hence oxygen consumption at any given bloodflow rate; therefore, it may affect the balance of renal oxygen supply vs. demand and hence Epo production. The purpose of this study was to determine whether Epo production is modulated by the renin-angiotensin system (RAS). Twenty normal subjects on a controlled sodium and protein diet had glomerular filtration rate (GFR) and renal plasma flow (RPF)assessed by standard methods of inulin and para-aminohippurate clearance, respectively, at baseline, hourly after the administration of losartan (25 mg) and after each 30 minute period of the infusion of Ang II at doses of 0.5, 1.5 and 2.5 ng/kg/minute. The baseline GFR was 115+/-4.0 ml/minute/1.73 m2, RPF 650+/-29 ml/minute/1.73 m2 and Epo 12.4+/-0.8 U/L. In spite of a marked increase in filtration fraction (FF) with Ang II, no changes in serum Epo levels were observed at two hours(11.7+/-1.3 U/L, p=n.s. compared with baseline). After the administration of losartan, there was a variable effect on FF, but a strong correlation of the change in serum Epo concentration and the change in FF(r=0.648, p=0.002), suggesting that the RAS may modulate Epo production.

Adult↗
PubMed2000

Common symptoms in advanced cancer.

The relief of physical and psychological symptoms is an essential part of palliative care. Advanced cancer is an acute process; because the clinical picture changes rapidly, symptoms must be reassessed regularly, and a careful history is essential. Defining the relationship of the symptoms to the disease can defuse fear and encourage a sense of control in patients and their families. We review the pathophysiology, causes, prevalence, consequence, and management of common symptoms in advanced cancer.

Disease Progression↗
PubMed1999

Testing for multiple species in fossil samples: an evaluation and comparison of tests for equal relative variation.

Tests for equal relative variation are valuable and frequently used tools for evaluating hypotheses about taxonomic heterogeneity in fossil hominids. In this study, Monte Carlo methods and simulated data are used to evaluate and compare 11 tests for equal relative variation. The tests evaluated include CV-based parametric bootstrap tests, modifications of Levene's test, and modified weighted scores tests. The results of these simulations show that a modified version of the weighted scores test developed by Fligner and Killeen ([1976] J. Am. Stat. Assoc. 71:210-213) is the only test that maintains an acceptable balance of type I and type II errors, even under conditions where all other tests have extraordinarily high type I error rates or little power.

Animals↗
PubMed1998

Technical note: a blind test of mandibular ramus flexure as a morphologic indicator of sexual dimorphism in the human skeleton.

Loth and Henneberg (1996, Am. J. Phys. Anthropol. 99:473-487) identified a single morphological feature of the mandible, the presence or absence of a distinct flexure or angulation of the posterior margin of the mandibular ramus at the level of the occlusal plane, which appears to be an extraordinarily accurate predictor of sex. Using only this feature, Loth and Henneberg were able to predict sex with 94% accuracy in a large sample of mandibles. In this article, we report the results of a blind test of mandibular ramus flexure as a predictor of sex. In our blind test, only 62.5% of the mandibles were correctly sexed, and virtually identical results were obtained when the same sample of mandibles was examined by a second observer. Overall, our results demonstrate that: 1) the association between ramus flexure and sex is weak; 2) the predictive accuracy of Loth and Henneberg's method is better than chance for only one sex, males; and 3) the method is based on a trait that cannot be reliably or consistently identified.

Adult↗
PubMed1998

Identification and expression of multidrug transporters responsible for fluconazole resistance in Candida dubliniensis.

Candida dubliniensis is a recently described Candida species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [3H] fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-N-oxide and methotrexate. These findings suggested that C. dubliniensis may encode multidrug transporters similar to those encoded by the C. albicans MDR1, CDR1, and CDR2 genes (CaMDR1, CaCDR1, and CaCDR2, respectively). A C. dubliniensis homolog of CaMDR1, termed CdMDR1, was cloned; its nucleotide sequence was found to be 92% identical to the corresponding CaMDR1 sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR, C. dubliniensis was also found to encode homologs of CDR1 and CDR2, termed CdCDR1 and CdCDR2, respectively. Expression of CdMDR1 in a fluconazole-susceptible delta pdr5 null mutant of Saccharomyces cerevisiae conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [3H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates of C. dubliniensis revealed that fluconazole resistance was associated with increased expression of CdMDR1 mRNA. In contrast, most studies showed that overexpression of CaCDR1 was associated with fluconazole resistance in C. albicans. Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives of C. dubliniensis generated in vitro, some of which also exhibited increased levels of CdCDR1 mRNA and CdCdr1p protein. These results demonstrate that C. dubliniensis encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Long-term effects of Semliki Forest virus infection in the mouse central nervous system.

Semliki Forest virus (SFV) infection of mice is used as a model to study pathogenic processes occurring in viral encephalitis and demyelinating disease. In this study, the long-term effects of infection by the avirulent M9 mutant of SPV on the central nervous system (CNS) of BALB/c and SJL mice were determined. The presence of infectious virus, viral RNA and cytokine mRNA in the brains of individual mice and the presence of lesions in the spinal cords of the same mice up to 360 days post-infection (d.p.i.) were analysed in order to detect any correlation between these parameters of pathogenesis. Infectious virus could not be detected beyond 7 d.p.i. for either mouse strain. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to detect the presence of the E2 and nsP1 regions of the virus genome and mRNA for interferon-gamma and tumour necrosis factor-alpha. Viral RNA could be detected up to 90 d.p.i. for both mouse strains. Cytokine mRNA could be detected up to 28 d.p.i. for BALB/c mice but up to 360 d.p.i. for SJL mice. Inflammatory lesions, which were associated with cytokine mRNA expression, were not detected in BALB/c mice beyond 28 d.p.i. but were detected in two SJL mice at 90 d.p.i. It is concluded that M9-SFV infection induces long-term prolonged expression of pro-inflammatory cytokines in the CNS of the majority of SJL (but not BALB/c) mice which is not associated with persistence of the virus genome. M9-SFV infection of SJL mice may be a relevant model for the pathogenesis of multiple sclerosis in man.

Alphavirus Infections↗
PubMed1996

Accumulation of glycated albumin in end-stage renal failure: evidence for the principle of "physiological microalbuminuria".

In light of the growing understanding of the toxic effects of glycated albumin and of the preferential excretion of this substance, the excretion of glycated albumin could be considered a physiologic function of the kidney. Furthermore, if the increased load of glycated albumin in diabetic patients results in glycated albumin excretion rates in the range of 20 to 200 microg/min, might this not be considered "physiologic microalbuminuria"? The hypothesis is presented that microalbuminuria composed of glycated albumin is a homeostatic renal function. Although some proteins are glycosylated for their normal physiologic function, many proteins are glycated nonenzymatically according to ambient blood glucose. Albumin is subject to nonenzymatic glycation in all humans, but at increased rates in diabetic patients. Glycated albumin induces changes in the microvasculature and glomerulus that may lead to endothelial dysfunction and diabetic nephropathy, respectively. Renal excretion of glycated albumin is enhanced compared with native albumin. To explore this potential homeostatic function of the kidney, patients with impaired renal function were studied to determine whether glycated albumin accumulates. Plasma levels of glycated albumin were determined in diabetic and nondiabetic patients on hemodialysis. Hemoglobin A1c was used as an index of the rate of nonenzymatic glycation of proteins. Hemoglobin A1c was increased in the diabetic subjects but was normal in the nondiabetic group (7.9% +/- 0.5% v 6.2% +/- 0.2%, respectively; P < 0.01). On the other hand, the glycated albumin was elevated in both groups and was not significantly different between them (1.95% +/- 0.15% in the diabetic patients v 1.75% +/- 0.14% in the nondiabetic patients; P = NS). The results of this study provide the first clinical evidence supporting the hypothesis that the excretion of glycated albumin is a homeostatic renal function.

Aged↗
PubMed1996

Prevention of early glomerulopathy with tolrestat in the streptozotocin-induced diabetic rat.

Hyperglycemia is of central importance in the pathogenesis of the complications of diabetes mellitus. Glucose activation of the polyol pathway may lead to renal arteriolar smooth muscle and glomerular mesangial cell hypocontractility. In the streptozotocin-induced diabetic rat, the effect of the aldose reductase inhibitor, tolrestat, in preventing glomerular hyperfiltration, renal hypertrophy, extracellular matrix accumulation, and mesangial cell hypocontractility was addressed. Streptozotocin-induced diabetic rats were followed for 12 weeks and half received tolrestat (25 mg/kg per day). Increased glomerular filtration rate was prevented by tolrestat (3.1 +/- 0.3 vs. 1.8 +/- 0.2 mL/min, diabetes vs. diabetes + tolrestat, p < 0.01), in part by reduction of the filtration fraction (0.39 +/- 0.03 vs. 0.29 +/- 0.01, diabetes vs. diabetes + tolrestat, p < 0.01). Tolrestat prevented the raised albumin excretion rates (3594 +/- 1154 vs. 713 +/- 161 mg/24 h, diabetes vs. diabetes + tolrestat, p < 0.01). Endothelin-1-induced contraction of isolated glomeruli was normal in tolrestat-treated diabetic animals compared with the hypocontractile diabetic glomeruli. Tolrestat prevented glomerular hypertrophy (1.86 +/- 0.10 vs. 1.49 +/- 0.03 microns 2 x 10(5), diabetes vs. diabetes + tolrestat, p < 0.001) and attenuated the accumulation of basement-membrane-like material (50.2 +/- 0.4% vs. 46.4 +/- 0.8%, diabetes vs. diabetes+tolrestat, p < 0.001). Fractional mesangial expansion was unchanged in tolrestat-treated diabetic rats compared with untreated animals. Tolrestat prevents the functional changes of glomerular hyperfiltration, mesangial cell hypocontractility, and increased glomerular permeability to albumin. Polyol accumulation may have differential effects on glomerular growth and extracellular matrix accumulation in early diabetic nephropathy.

Ampholyte Mixtures↗
PubMed1994

Mobile lipids and metabolic heterogeneity of brain tumours as detectable by ex vivo 1H MR spectroscopy.

To examine metabolic heterogeneity in primary brain tumour, multiple biopsies (one to five per tumour) from four benign meningiomas, five acoustic schwannomas, eleven glial tumours and five medulloblastomas were each subdivided into one to five samples (total = 194) and investigated using ex vivo 360 MHz 1H MR spectroscopy with histopathological correlation. Low amounts of mobile lipids were detected in meningothelial meningiomas and medulloblastomas, high amounts in some or all samples of all other tumours. The differences in non-lipid metabolites between different tumour types were less marked, with the exception of the medulloblastomas, which had high amounts of N-acetyl aspartate and cholines. The amount of mobile lipid correlated with Antoni type B areas in schwannomas and necrosis in a high grade giant cell tumour. The amount of lipid varied significantly from sample to sample in a grade 2 astrocytoma and grade 4 astrocytoma samples with 0-5% necrosis but did not correlate with the site in the tumour or histopathological characteristics. The metabolic heterogeneity occurred on a spatial scale at least as small as the size of the MR samples, i.e., < or = 60 mg. These results suggest that the detection of metabolic heterogeneity and mobile lipids may have importance for the design of clinical studies.

Astrocytoma↗
PubMed1993

Doppler echocardiographic evidence of left ventricular diastolic dysfunction in ankylosing spondylitis.

Although cardiac involvement in the form of conduction abnormalities or aortic regurgitation occurs in 5 to 10% of patients with ankylosing spondylitis, few studies have assessed left ventricular (LV) function. This study assesses the prevalence of both systolic and diastolic LV dysfunction and other cardiac abnormalities in patients with ankylosing spondylitis who have no clinical cardiac manifestations. Fifty-nine patients (49 men and 10 women, mean age 42 +/- 10 years) underwent full clinical examination, electrocardiography, 24-hour Holter monitoring and 2-dimensional, M-mode and Doppler echocardiography. Mean disease duration was 17 +/- 9 years (range 1 to 42). Seventeen patients had evidence of noncardiac extraarticular manifestations. Precordial examination was normal in all. An age- and sex-matched control group of 44 healthy subjects was also studied. On echocardiography, abnormal LV diastolic function was detected in 12 patients (20%). Prolonged isovolumic relaxation time, prolonged deceleration time, reduced rate of descent of flow velocity in early diastole (EF slope) and reversal of the early and late peak transmitral diastolic flow velocities (E/A ratio) were noted in 9 patients. In 3 patients there was an increased E/A ratio, reduced deceleration time and increased EF slope. Mild aortic regurgitation and mitral regurgitation was seen in 1 and 3 patients, respectively. No abnormalities of left atrial size, LV systolic or diastolic dimensions or wall thicknesses were noted. There was no correlation between the presence of LV diastolic dysfunction and age, disease severity, disease duration, or the presence of extraarticular manifestations.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Deoxyribonucleic acid flow cytometry in invasive bladder carcinoma: a possible predictor for successful bladder preservation following transurethral surgery and chemotherapy-radiotherapy.

Tumor deoxyribonucleic acid (DNA) ploidy was evaluated as an objective parameter that may correlate better with the responsiveness of bladder cancer to chemotherapy plus radiotherapy than do clinical features or histopathological subtypes. A total of 40 patients with localized muscle-invading bladder cancer (clinical stages T2 to T4) underwent prospective treatment on a potential bladder preserving protocol. Tumors of 37 of the 40 patients were analyzed by DNA flow cytometry of multiple paraffin embedded specimens. Transurethral resection, neoadjuvant chemotherapy and 40 Gy. radiotherapy plus cisplatin were followed by urological reevaluation of the tumor (a complete response required a negative biopsy and a negative urine cytology study). A total of 7 noncomplete response patients underwent immediate radical cystectomy whereas the full bladder sparing treatment (radiotherapy to 64.80 Gy. plus cisplatin) was given to 23 complete response patients and 7 noncomplete response patients who were unsuited for surgery. Of the tumors 22 (59%) were purely aneuploid and 10 (27%) were purely diploid. Five tumors contained aneuploid and diploid patterns in different tumor specimens (partly diploid). Current status with a 30-month median followup in surviving patients includes an 82% overall survival rate in the aneuploid group versus 47% in the diploid/partly diploid group. Of all the patients 68% are free of invasive tumor: 82% in the aneuploid group versus 47% in the diploid/partly diploid group. By multivariate analysis pure aneuploidy was significantly (p = 0.05) correlated with freedom from invasive tumor in the bladder (either as persistence or as recurrence) and approached significance (p = 0.08) in correlation with overall patient survival. A longer observation time will be required to confirm this unexpectedly good outcome for patients with pure aneuploid tumors. We hypothesize that pretreatment DNA ploidy status may become a clinically useful prognostic factor in selecting patients for successful treatment with transurethral surgery and neoadjuvant chemotherapy plus radiotherapy.

Clinical Protocols↗
PubMed1992

Effect of n-3 fatty acids from fish oil on hemostasis, blood pressure, and lipid profile of dialysis patients.

Dialysis patients have an inordinate risk of cardiovascular events. Fish oils, rich in n-3 fatty acids, are believed to be beneficial in the prevention of atherosclerosis and thrombosis. Hence, the use of fish oils deserves consideration as a preventative or therapeutic intervention in dialysis patients. The suggestion has been made that n-3 fatty acids could increase the risk of bleeding, and thus, the safety of the use of these agents in dialysis patients must be established before long-term studies are undertaken. This study addresses the effect of n-3 fatty acids on the hemostatic profile of dialysis patients. Sixteen patients on chronic dialysis therapy were randomized to fish oil (MaxEPA) or placebo (olive oil) in a double-blind cross-over study. They received 3.6 g of n-3 fatty acids for 4 wk. Bleeding times were 4.8 +/- 0.4 min on MaxEPA and 4.5 +/- 0.3 min on placebo. Platelet aggregation to low-dose ADP or collagen also remained unchanged. There was a trend to lower serum triglyceride levels (2.7 +/- 0.5 versus 3.4 +/- 0.6 mmol/L, fish oil versus placebo) that did not reach statistical significance. Gastrointestinal side effects occurred in 10 of the 16 subjects and were severe in 5 patients. These side effects occurred in both the olive oil and the fish oil groups. The study had a 95% chance of detecting a clinically doubling significant increase in bleeding time, i.e., beta error less than 5%. In conclusion, n-3 fatty acids do not introduce a clinically important risk of bleeding for patients with end-stage renal disease.

Adult↗
PubMed1991

Renal tubular acidosis (RTA): recognize the ammonium defect and pHorget the urine pH.

To maintain acid-base balance, the kidney must generate new bicarbonate by metabolizing glutamine and excreting ammonium (NH4+). During chronic metabolic acidosis, the kidney should respond by increasing the rate of excretion of NH4+ to 200-300 mmol/day. If the rate of excretion of NH4+ is much lower, the kidney is responsible for causing or perpetuating the chronic metabolic acidosis. Thus, the first step in the assessment of hyperchloraemic metabolic acidosis is to evaluate the rate of excretion of NH4+. It is important to recognize that the urine pH may be misleading when initially assessing the cause of this acidosis, as it does not necessarily reflect the rate of excretion of NH4+. If proximal renal tubular acidosis (RTA) is excluded, low NH4+ excretion disease may be broadly classified into problems of NH4+ production and problems of NH4+ transfer to the urine; the latter being due to either interstitial disease or disorders of hydrogen ion secretion. The measurement of the urine pH at this stage may identify which problem predominates. This approach returns the focus of the investigation of RTA from urine pH to urine NH4+.

Acid-Base Equilibrium↗
PubMed1991

The life shortening effects of treatment with doxorubicin and/or local irradiation on a cohort of young C3Hf/Sed mice.

The long-term consequences of treating a cohort of C3Hf/Sed mice in early life with either local-field single dose radiation, systemic doxorubicin, or both, are reported in this study. Significant life shortening was observed in all treatment groups. Median survival times (days) from time of treatment were: control, 690; 35 Gy, 560; 70 Gy, 460; 5 mg/kg doxorubicin, 580; 10 mg/kg doxorubicin, 350; 35 Gy + 5 mg/kg doxorubicin, 510; 70 Gy + 10 mg/kg doxorubicin, 310. Mice receiving hind limb irradiation died principally from induced sarcomas in a dose dependent fashion (80% after 70 Gy and 55% after 35 Gy). Those treated with doxorubicin alone showed an increase in the actuarial incidence of spontaneous malignancies but died mainly from non-malignant causes. Histological examination did not reveal any characteristic cardiac, renal or pulmonary lesions. Doxorubicin did not increase the rate of development of radiation induced sarcomas in mice treated with combined modality.

Animals↗
PubMed1991

Modulation of the secretion of potassium by accompanying anions in humans.

In animals, secretion of potassium (K) in the cortical collecting duct (CCD) is modulated by the properties of the accompanying anion. In humans, results are inconclusive as previous studies have not differentiated between a kaliuresis due to a rise in the concentration of K from one due to an increase in the volume of urine. Our purpose was to study the effects of chloride (Cl) and bicarbonate on the secretion of K in the CCD in humans using the transtubular K concentration gradient (TTKG), a semi-quantitative index of secretion of K in the terminal CCD. After control blood and urine samples were obtained, all subjects ingested 0.2 mg fludrocortisone to ensure that mineralocorticoids were not limiting the secretion of K. The anionic composition of the urine was varied using three protocols: Normal subjects (N = 11) ingested cystine and methionine to induce sulfaturia; nine subjects with a contracted ECF volume (to lower the concentration of Cl in the urine) were also studied during sulfaturia following the ingestion of cystine and methionine; 13 normovolemic subjects were studied during bicarbonaturia following the ingestion of acetazolamide. When the concentration of Cl in the urine was greater than 15 mmol/liter, sulfate had no effect on the TTKG. With lower concentrations of Cl in the urine, the TTKG rose 1.5-fold. The TTKG rose 1.8-fold in the presence of bicarbonaturia despite concentrations of Cl in the urine that were greater than 15 mmol/liter, suggesting that bicarbonate has additional effects on this K secretory process. At comparable concentrations of sulfate and bicarbonate in the urine, the TTKG was increased only with bicarbonaturia.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetazolamide↗
PubMed1991

Glue-sniffing and distal renal tubular acidosis: sticking to the facts.

An index case is presented to introduce the subject of the acid-base and electrolyte abnormalities resulting from toluene abuse. These include metabolic acidosis associated with a normal anion gap and excessive loss of sodium and potassium in the urine. The major question addressed is, what is the basis for the metabolic acidosis? Overproduction of hippuric acid resulting from the metabolism of toluene plays a more important role in the genesis of the metabolic acidosis than was previously believed. This conclusion is supported by the observation that the rate of excretion of ammonium was not low during metabolic acidosis in six of eight patients, suggesting that distal renal tubular acidosis was not an important acid-base abnormality in most cases where ammonium was measured. The excretion of hippurate in the urine unmatched by ammonium also mandates an enhanced rate of excretion of the cations, sodium and potassium. The loss of sodium causes extracellular fluid volume contraction and a fall in the glomerular filtration rate, which may transform the normal anion gap type of metabolic acidosis into one with a high anion gap (accumulation of hippurate and other anions). Continuing loss of potassium in the urine leads to hypokalemia. An understanding of the metabolism of toluene provides the basis for the unusual biochemical abnormalities seen with abuse of this solvent.

Acid-Base Equilibrium↗