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Biomedical subjects

Michael J Stewart

Publications and source records attributed to Michael J Stewart.

At least 19 recordsLinked to original sources
PubMed2006

A prospective randomised controlled trial to determine the early and late reactions after the use of iopamidol 340 (Niopam) and iomeprol 350 (Iomeron) in cardiac catheterisation.

UNLABELLED: A new generation of intravascular contrast agents, the non-ionic monomers have safety profiles that are superior to those of older ionic compounds. There are, however, significant differences between these agents. AIM: The aim of this study was to determine the incidence of early (<24h) and late (>24h to 7 days) reactions to two non-ionic contrast agents currently used during cardiac catheterisation: iopamidol 340 (Niopam Bracco UK Ltd.) and iomeprol 350 (Iomeron Bracco UK Ltd.). METHODS: This was a prospective, randomised, double blinded trial. One thousand nine hundred and eighty-five patients undergoing cardiac catheterisation received one of the following contrast agents on a weekly basis: iopamidol 340 (Niopam) and iomeprol 350 (Iomeron). Reactions that were possibly related to the contrast agents were recorded on predefined data collection forms during the first 24h of the procedure (early reaction) and after 24h to 7 days (late reaction) by means of a questionnaire. RESULTS: The baseline characteristics were matched in both the groups. There was no significant difference in the incidence of heat sensation experienced between the two groups (p=0.1). Early non-heat reactions occurred in 2.7% of patients receiving iopamidol 340 (Niopam) and 4% of those receiving iomeprol 350 (Iomeron) (p=0.1). Significant electrocardiographic changes were recorded in 1.7% of patients who received iopamidol 340 (Niopam), and 1% of those who received iomeprol 350 (Iomeron) (p=0.2). Bradycardia occurred more frequently in the iopamidol 350 group (0.8%) compared to the iomeprol 350 group (0.1%) p=0.02. Late reactions occurred in 16.2% of those receiving iopamidol 340 (Niopam) and 21.7% of those receiving iomeprol 350 (Iomeron) (p=0.02). A total of 23 (3.7%) patients in the iopamidol group and 39 (6.2%) patients in the iomeprol group reported nausea, p=0.01. CONCLUSIONS: The incidence of early adverse reactions was similar with the two non-ionic contrast agents. Although bradycardia was slightly more frequent using iopamidol 340, nausea was reported more commonly 24h after the procedure in patients receiving Iomeron 350 (Iomeron). We conclude that there were only minor clinical differences between these agents; both are safe and well tolerated.

Adult↗
PubMed2006

Platypnoea orthodeoxia in a patient with aortic root dilatation and a patent foramen ovale.

Platypnoea orthodeoxia syndrome is a rare condition in which shortness of breath and hypoxaemia occur when upright and resolve when prone. The hypoxaemia results from increased right to left shunting of deoxygenated blood, when standing, through a patent foramen ovale (PFO), atrial septal defect (ASD) or other right to left shunt, in the absence of raised right-heart pressure. We present the case of a patient with platypnoea orthodeoxia with marked shunting through a large PFO, evaluated by transesophageal and transthoracic echo.

Aged↗
PubMed2006

A randomized trial of prophylactic antiarrhythmic agents (amiodarone and sotalol) in patients with atrial fibrillation for whom direct current cardioversion is planned.

UNLABELLED: Antiarrhythmic agents enhance maintenance of sinus rhythm (SR) after direct current cardioversion (DCC) for atrial fibrillation but there are few comparative trials. BACKGROUND: The aims of the study were (1) to establish whether patients successfully cardioverted to SR are more likely to stay in SR over 6 months if taking amiodarone or sotalol, and if so, to establish whether one agent is better than the other; (2) to establish whether taking amiodarone or sotalol is better at achieving chemical cardioversion within the 6 weeks before DCC; and (3) to establish whether DCC is more likely to be successful on a drug. METHODS: Randomized, prospective, nonblinded, controlled study of treatment with either amiodarone (n = 27), sotalol (n = 36), or no antiarrhythmic agent (n = 31). RESULTS: Chemical cardioversion occurred in 7 patients in the amiodarone group (A), 7 patients in the sotalol group (S), but none in the no-antiarrhythmic group (N). A total of 33 (92%) patients in the sotalol group, 22 (81%) patients in the amiodarone group, and 23 (74%) patients in the no-antiarrhythmic group were in SR after cardioversion. Of the original cohort of patients, 17 (63%) patients in the amiodarone group remained in SR at 6-month follow-up, compared with 14 (39%) in the sotalol group and 5 (16%) in the no-antiarrhythmic group (A vs N, P < .0002, P < .0006B [after Bonferroni correction]; A vs S, P = .05, P = .15B; and S vs N, P = .03, P = .09B). CONCLUSIONS: Amiodarone and sotalol achieved chemical cardioversion before planned electrical cardioversion in 26% and 19% of patients, respectively. After successful cardioversion, amiodarone appears better than sotalol at maintaining SR at 6 months.

Aged↗
PubMed2006

c-Jun N-terminal kinase negatively regulates dsRNA and RSV induction of tumor necrosis factor- alpha transcription in human epithelial cells.

Secretion of inflammatory cytokines is the initial step of the immune response to viral infections. This innate immune response is mediated by the expression of a variety of cytokines, exemplified by tumor necrosis factor- alpha (TNF-alpha). The presence of dsRNA during viral infections is a key step in activation of several signaling pathways, including protein kinase R (PKR), toll-like receptor 3 (TLR3), mitogen-activated protein kinase (MAPK), activator protein-1 (AP-1), interferon regulatory factors (IRFs), and NF-kappaB pathways, which are all relevant in the expression of inflammatory cytokines. We previously reported that PKR and p38 MAPK were required for dsRNA and viral induction of inflammatory cytokines in epithelial cells. Here, we report that activation of c-Jun N-terminal kinase (JNK) during dsRNA treatment or respiratory syncytial viral (RSV) infection negatively regulates the induction of TNF-alpha in human epithelial cells. Inhibition of JNK by a pharmacologic inhibitor showed that expression of TNF-alpha increased following both dsRNA treatment and infection with RSV. Importantly, transfection of epithelial cells with a dominant-negative mutant of JNK significantly increased dsRNA induction of TNF-alpha. The mechanism by which JNK inhibition increases TNF-alpha induction appears to be through p38 MAPK activation. Our data show that JNK is a negative regulator of dsRNA and RSV induction of TNF-alpha expression and, thus, may act as a counterbalance to proinflammatory signals generated during viral infections.

Anthracenes↗
PubMed2005

Africa's present and future needs in toxicology education: Southern African perspective.

Degrees and diplomas as well as certificates that are granted by universities and technikons in South Africa in scientific disciplines, such as forensic medicine, pharmacology, marine and veterinary sciences, environmental health, and occupational hygiene, include toxicology as one of the subjects in their overall syllabus. However, aspects of toxicology included in each of these courses are biased towards that particular subdiscipline and basic level of toxicology may be taught. Educational needs in toxicology in South Africa can be summarized as follows: (a) recognition of toxicology as a discipline in its own right at these tertiary education institutions and (b) creation of opportunities to study and obtain higher degrees in one or more of the many subdisciplines of toxicology. The results from a survey conducted on the toxicology syllabi offered at these tertiary education institutions are used to substantiate these needs.

Education↗
PubMed2005

A cardiac paraganglioma presenting with atypical chest pain.

Primary cardiac tumours are rare. The majority are benign and 75% are atrial myxomas. One of the more unusual benign tumours affecting the heart is a cardiac paraganglioma. A 56-year male was presented with a 6-month history of vague, left-sided chest pain, intermittent parathesia of the left arm and dyspnoea on bending. Echocardiography documented a large, highly vascular mass, attached to the intra-atrial septum. All investigations, haematological, biochemical, neuroendocrine tumour markers and urinary cathecholamine levels, were within normal limits. Macroscopically the tumour involved the whole of the atrial septum, roof of the left atrium and extended to surround the superior vena cava, excluding total resection. The feeding vessels were ligated in the hope of infarcting the remainder of the tumour. In over 2-years of follow-up, the patient remains clinically stable. To our knowledge this is the first reported case where vascular ligation has been used to control a cardiac paraganglioma.

Chest Pain↗
PubMed2005

Adulteration of South African traditional herbal remedies.

Traditional herbal remedies are used as alternative medicine by a large proportion of people worldwide. Herbals are generally perceived as safe, harmless, and free from side effects, but there have been reports of adulteration of Asian herbal remedies with Western pharmaceuticals, a practice that has not hitherto been observed in Africa. The authors present 2 cases from South Africa in which herbal remedies, consumed by patients admitted to hospital, were found to be adulterated with commercially available Western medicines. The adulterants were identified using high-performance liquid chromatography with a photodiode array detector and gas chromatography-mass spectrometry. The authors alert clinicians to the fact that adulteration of herbal remedies may become more common and should be considered, especially in cases where the symptoms are confusing in light of the history.

Acidosis, Lactic↗
PubMed2005

Nephrotoxicity associated with exposure to plant toxins, with particular reference to Africa.

Acute renal failure is a frequent cause of morbidity and mortality in the hospitalized population worldwide. In Africa, apart from hemodynamic causes and infections, herbal remedies contribute to both morbidity and mortality, although these causes often go unrecognized. This paper reviews reports of herbal remedies that have been shown to result in nephrotoxicity. The indications for use of the remedies, signs and symptoms in poisoned patients, and the methods used to detect toxic compounds in plant specimens or in biological fluids are covered.

Acute Kidney Injury↗
PubMed2005

Uranium concentrations in South African herbal remedies.

South Africa contains some of the world's largest mineral deposits, which include uranium. Uranium is mined as a by-product of gold production. The uranium content of the surface soil and groundwater in South Africa has been measured and shows marked variation, depending on location. Herbal remedies are collected by traditional healers from many sites, some of which may be contaminated. Thirty herbal remedies were analyzed using a sensitive adsorptive stripping voltammetry method. Eight samples had levels below the limit of detection, but in five the levels were greatly elevated, showing concentrations above 40,000 ppb. The mean uranium concentration of the remainder of the specimens was of the order of 15,000 ppb. We have attempted to put these data into context by comparison with other studies of absorption of uranium by the oral route.

Drug Contamination↗
PubMed2005

Basal and reovirus-induced beta interferon (IFN-beta) and IFN-beta-stimulated gene expression are cell type specific in the cardiac protective response.

Viral myocarditis is an important human disease, with a wide variety of viruses implicated. Cardiac myocytes are not replenished yet are critical for host survival and thus may have a unique response to infection. Previously, we determined that the extent of reovirus induction of beta interferon (IFN-beta) and IFN-beta-mediated protection in primary cardiac myocyte cultures was inversely correlated with the extent of reovirus-induced cardiac damage in a mouse model. Surprisingly, and in contrast, the IFN-beta response did not determine reovirus replication in skeletal muscle cells. Here we compared the IFN-beta response in cardiac myocytes to that in primary cardiac fibroblast cultures, a readily replenished cardiac cell type. We compared basal and reovirus-induced expression of IFN-beta, IRF-7 (an interferon-stimulated gene [ISG] that further induces IFN-beta), and another ISG (561) in the two cell types by using real-time reverse transcription-PCR. Basal IFN-beta, IRF-7, and 561 expression was higher in cardiac myocytes than in cardiac fibroblasts. Reovirus T3D induced greater expression of IFN-beta in cardiac myocytes than in cardiac fibroblasts but equivalent expression of IRF-7 and 561 in the two cell types (though fold induction for IRF-7 and 561 was higher in fibroblasts than in myocytes because of the differences in basal expression). Interestingly, while reovirus replicated to equivalent titers in cardiac myocytes and cardiac fibroblasts, removal of IFN-beta resulted in 10-fold-greater reovirus replication in the fibroblasts than in the myocytes. Together the data suggest that the IFN-beta response controls reovirus replication equivalently in the two cell types. In the absence of reovirus-induced IFN-beta, however, reovirus replicates to higher titers in cardiac fibroblasts than in cardiac myocytes, suggesting that the higher basal IFN-beta and ISG expression in myocytes may play an important protective role.

Animals↗
PubMed2005

GC/MS identification of toxic pyrrolizidine alkaloids in traditional remedies given to two sets of twins.

Neo- and perinatal mortality is high in most of Africa. Twins are at particular risk of perinatal mortality. The contribution of traditional remedies is seldom addressed. The case histories of two sets of twins who were treated with traditional remedies are described. The herbal remedies were analysed using gas chromatography-mass spectrometry. In one family, both siblings survived, albeit with hepatic damage. In the other family, one twin died within 24 h and the second one month after admission with a diagnosis of veno-occlusive liver disease (VOD). In both cases, the presence of the toxic pyrrolizidine alkaloid retrorsine, which is known to lead to VOD, was identified. Health-care workers should be aware of the possibility of traditional medicine administration as a cause of illness, specifically in twin births.

Diseases in Twins↗
PubMed2005

Acute renal failure associated with the use of traditional folk remedies in South Africa.

The use of folk remedies is widespread throughout Africa. Acute renal failure (ARF) is one of the most severe, but under-recognized, complications of folk remedy use. This report aims to describe the clinical presentation, outcomes, and nature of renal injury in patients with folk-remedy-associated ARF. Clinical data were evaluated retrospectively in 78 patients with ARF associated with recent folk remedy use. ARF was defined as elevated serum urea and creatinine above the age-appropriate normal ranges, persistent oligoanuria, worsening renal function with time, or need for dialysis. Overall mortality in patients with ARF was 41%. Mortality was higher in adults (45.5%) than in infants (36.6%), in patients with both renal and liver dysfunction (62.5%) than in those with renal dysfunction alone (22.6%), and in HIV-positive (44.4%) versus HIV-negative (34.6%) patients. Vomiting (51.3%) and diarrhea (43.6%) were the most frequent presenting symptoms. Metabolic acidosis (80.8%) and volume depletion (62.8%) were the most frequent clinical findings. The definable causes of ARF were pre-renal (26.9%), acute tubular necrosis (ATN; 26.9%), hepatorenal syndrome (6.4%), urinary tract infection/sepsis (7.7%), and primary renal disorders (7.7%). Twenty-seven patients had concomitant medical conditions unlikely primarily related to folk remedy ingestion. In conclusion, ARF occurring after use of folk remedies in South Africa is associated with significant morbidity and mortality. The most common contributors to ARF in this setting are volume depletion and ATN. Significantly, although a proportion of patients have underlying systemic or renal conditions that may contribute to renal dysfunction, in the majority of patients, folk remedy use appears to be the most likely proximate cause. In view of the large numbers of Africans living abroad, more widespread awareness of this important clinical problem needs to be raised.

Acute Kidney Injury↗
PubMed2004

A randomized trial of rescue angioplasty versus a conservative approach for failed fibrinolysis in ST-segment elevation myocardial infarction: the Middlesbrough Early Revascularization to Limit INfarction (MERLIN) trial.

OBJECTIVES: We sought to compare emergency coronary angiography with or without rescue percutaneous coronary intervention (PCI) with conservative treatment in patients with failed fibrinolysis complicating ST-segment elevation myocardial infarction (STEMI). BACKGROUND: Most patients with STEMI receive fibrinolytic therapy and aspirin. The management of failed fibrinolysis is unclear. METHODS: A total of 307 patients with STEMI and failed fibrinolysis were randomized to emergency coronary angiography with or without rescue PCI or conservative treatment. RESULTS: Thirty-day all-cause mortality was similar in the rescue and conservative groups (9.8% vs. 11%, p = 0.7, risk difference [RD] 1.2%, 95% confidence interval [CI] -5.8 to 8.3). The composite secondary end point of death/re-infarction/stroke/subsequent revascularization/heart failure occurred less frequently in the rescue group (37.3% vs. 50%, p = 0.02, RD 12.7%, 95% CI 1.6 to 23.5), driven by less subsequent revascularization (6.5% vs. 20.1%, p < 0.01, RD 13.6%, 95% CI 6.2 to 21.4). Re-infarction and clinical heart failure were less common in the rescue group (7.2% vs. 10.4%, p = 0.3, RD 3.2%, 95% CI -3.3 to 9.9; and 24.2% vs. 29.2%, p = 0.3, RD 5.7%, 95% CI -4.3 to 15.6, respectively). Strokes and transfusions were more common in the rescue group (4.6% vs. 0.6%, p = 0.03, RD 3.9%, 95% CI 0.5 to 8.6; and 11.1% vs. 1.3%, p < 0.001, RD 9.8%, 95% CI 4.9 to 19.9, respectively). Left ventricular function at 30 days was the same in the two groups. CONCLUSIONS: Rescue angioplasty did not improve survival by 30 days, but improved event-free survival, almost completely due to a reduction in subsequent revascularization. Rescue angioplasty was associated with more strokes and more transfusions and did not result in preservation of left ventricular systolic function at 30 days.

Angioplasty, Balloon, Coronary↗
PubMed2004

Corrected TIMI frame count: applicability in modern digital catheter laboratories when different frame acquisition rates are used.

The original description of the TIMI frame count (TFC) method was based on angiograms acquired at 30 f/sec. Modern digital angiograms are acquired at lower frame rates (between 12.5 and 25 f/sec). Coronary angiography was acquired at 12.5 and 25 f/sec after 200 mug of intracoronary glyceryl trinitrate. Results of the corrected TIMI frame count (cTFC) at 12.5 and 25 f/sec for each vessel were: right coronary artery, 19.5 +/- 5.2 and 20.4 +/- 6.6 (P = 0.15); circumflex artery, 25.6 +/- 8.2 and 25.9 +/- 8.7 (P = 0.5); and left anterior descending artery, 22.5 +/- 8.1 and 23.8 +/- 10.4 (P = 0.15), respectively. The mean difference in the TFC between two injections by the same operator and by two operators was 0.4 (P = 0.7) and 0.4 (P = 0.2), respectively. The mean difference in the TFC for repeat measurements by the same observer and between two observers was 0.26 (P = 0.3) and 0.06 (P = 0.8), respectively. We confirm that the cTFC is a quantitative method to assess coronary flow that can be applied in a modern digital laboratory.

Aged↗
PubMed2004

Patterns of cerebral injury in a series of infants with congenital diaphragmatic hernia utilizing magnetic resonance imaging.

BACKGROUND: Congenital diaphragmatic hernia (CDH) is a condition with significant mortality and respiratory morbidity. Long-term neurodevelopmental outcome is not yet well documented. METHODS: The authors examined all cases of CDH at their institution over a 12-month period and performed magnetic resonance imaging (MRI) of the brain postoperatively. RESULTS: Eight of 10 patients survived to have an MR brain scan. All 8 patients had cerebral injury detected on MRI, with a predominance of white matter and deep nuclear gray matter injury. CONCLUSIONS: Cerebral injury detected with MRI is common in infants with congenital diaphragmatic hernia. The long-term significance of these MRI abnormalities is unknown, although the need for good long-term neurodevelopmental follow-up of infants with CDH is highlighted.

Brain↗
PubMed2004

Perceived psychological stress among high school basketball officials.

The purpose of this study was to survey certified high school basketball officials during midseason to assess whether the sources and magnitude of perceived psychological stress would be consistent with previous studies of officials in other sports. The sources and magnitude of perceived psychological stress were measured among 324 high school basketball officials (N=324; 312 men, 12 women) using a revised version of the Ontario Soccer Officials Survey. The mean age was 37.6 yr. (SD= 9.4), and the mean years of basketball refereeing experience was 11.7 yr. (SD=8.3). A random sample (N=498) of all basketball officials in a midwestern state (N=1,011) was used, and 324 of the surveys were returned (65%). The overall variance accounted for with the four factors was 84.7%. The magnitude of stress for these factors ranged from below mild to moderate.

Adult↗
PubMed2004

A prospective, randomized trial to determine the early and late reactions after the use of iopamidol 340 (Niopam) and iobitridol 350 (Xenetix) in cardiac catheterization.

BACKGROUND: Intravascular contrast agents presently used in modern digital catheter laboratories during cardiac catheterization are superior to older agents as regards patient tolerance. There are, however, significant differences between these agents. PURPOSE: The aim of this study was to determine the incidence of early (< 24 hours) and late (> 24 hours to 7 days) reactions to 2 contrast agents currently used during cardiac catheterization: iopamidol 340 (Niopam) and iobitridol 350 (Xenetix). METHODS: This was a prospective, randomized, double-blinded trial. Two thousand and nineteen patients undergoing cardiac catheterization received one of the following contrast agents: iopamidol 340 (Niopam) and iobitridol 350 (Xenetix). Reactions that were possibly related to the contrast agents were recorded during hospital admission (early reaction) and after discharge (late reaction) by means of a questionnaire. RESULTS: The baseline characteristics were matched in both the groups. There was no significant difference in the incidence of heat sensation experienced between the 2 groups, (p = 0.1). Early non-heat reactions occurred in 3.2% of patients receiving iopamidol 340 (Niopam) and 3.6% of those receiving iobitridol 350 (Xenetix), (p = 0.65). Electrocardiographic changes were recorded in 0.7% of patients who received iopamidol 340 (Niopam), and 2.6% of those who received iobitridol 350 (Xenetix), (p = < 0.01). Seven patients (0.8%) receiving iobitridol 350 suffered ventricular fibrillation requiring DC cardioversion compared with none in the iopamidol 340 group (p = < 0.01). Late reactions (post discharge symptoms) occurred in 13.9% of those receiving iopamidol 340 (Niopam) and 18.5% of those receiving iobitridol 350 (Xenetix) (p = 0.02). CONCLUSIONS: Iobitridol 350 (Xenetix) was associated with more ECG changes and, importantly, ventricular fibrillation, than iopamidol (Niopam). There were no features to suggest other benefits from iobitridol 350. These results suggest that iopamidol 340 is a preferable contrast agent in cardiac catheterization.

Adult↗