Metabolic defence against oxidative stress: the road less travelled so far

Bacteria have survived, and many have thrived, since antiquity in the presence of the highly-reactive chalcogen-oxygen (O₂ ). They are known to evoke intricate strategies to defend themselves from the reactive by-products of oxygen-reactive oxygen species (ROS). Many of these detoxifying mechanisms have been extensively characterized; superoxide dismutase, catalases, alkyl hydroperoxide reductase and the glutathione (GSH)-cycling system are responsible for neutralizing specific ROS. Meanwhile, a pool of NADPH-the reductive engine of many ROS-combating enzymes-is maintained by metabolic enzymes including, but not exclusively, glucose-6 phosphate dehydrogenase (G6PDH) and NADP-dependent isocitrate dehydrogenase (ICDH-NADP). So, it is not surprising that evidence continues to emerge demonstrating the pivotal role metabolism plays in mitigating ROS toxicity. Stemming from its ability to concurrently decrease the production of the pro-oxidative metabolite, NADH, while augmenting the antioxidative metabolite, NADPH, metabolism is the fulcrum of cellular redox potential. In this review, we will discuss the mounting evidence positioning metabolism and metabolic shifts observed during oxidative stress, as critical strategies microbes utilize to thrive in environments that are rife with ROS. The contribution of ketoacids-moieties capable of non-enzymatic decarboxylation in the presence of oxidants-as ROS scavengers will be elaborated alongside the metabolic pathways responsible for their homeostases. Further, the signalling role of the carboxylic acids generated following the ketoacid-mediated detoxification of the ROS will be commented on within the context of oxidative stress.

Aluminum-induced defective mitochondrial metabolism perturbs cytoskeletal dynamics in human astrocytoma cells

Although aluminum (Al), a known environmental toxin, has been implicated in a variety of neurological disorders, the molecular mechanism responsible for these conditions is not fully understood. In this report, we demonstrate the ability of Al to trigger mitochondrial dysfunction and ineffective adenosine triphosphate (ATP) production. This situation severely affected cytoskeletal dynamics. Whereas the control cells had well-defined structures, the Al-exposed astrocytoma cells appeared as globular structures. Creatine kinase (CK) and profilin-2, two critical modulators of cellular morphology, were markedly diminished in the astrocytoma cells treated with Al. Antioxidants such as alpha-ketoglutarate and N-acetylcysteine mitigated the occurrence of the globular-shaped cells promoted by Al toxicity. Taken together, these data reveal an intricate link between ATP metabolism and astrocytic dysfunction and provide molecular insights into the pathogenesis of Al-induced neurological diseases.

Hais cuaj txub kaum txub--to speak of all things: a Hmong cross-cultural case study

Cross-cultural medicine is a field that describes how disparate value and belief systems concerning health and disease affect the delivery of health care. This report describes the conflict between a Hmong immigrant family and the Western medical establishment over the care of their child with end stage renal disease [ESRD]. The health care providers, social service agencies and medical center failed to adequately respond to the needs of the family. The medical staff [nephrologist, nurse coordinator, dietician, social worker, and CPS worker] worked with a transcultural nurse, Hmong community health worker and the family, to design and negotiate a treatment plan that would be acceptable to the family and the health care team. Trust was reestablished between the family and the healthcare providers and the medical outcome for the child improved.

Single-dose pharmacokinetics and tolerability of everolimus in stable pediatric renal transplant patients

Everolimus (Certican; RAD), a novel macrolide with potent immunosuppressive and anti-proliferative activities, prevents acute rejection in adult recipients of renal transplantation. This phase I trial conducted in stable pediatric renal transplant patients examined the single-dose pharmacokinetics, safety, and tolerability of everolimus in combination with cyclosporin A (CsA; Neoral) and corticosteroids, with or without azathioprine. Nineteen pediatric patients were enrolled and received a single 1.2 mg/m2 dose of everolimus. Everolimus was safe and well tolerated, with a low incidence of adverse events reported and none judged to be related to the study medication. Everolimus administration did not increase infection rates or produce clinically significant changes in vital signs or changes in electrocardiograms. Apparent clearance and volume of distribution of everolimus increased with age, weight, and body surface area in a generally linear manner across the pediatric demographic ranges. Compared with adults from a previous study, apparent clearance (L/h) and distribution volume (L) were lower in pediatric patients, whereas the elimination half-life was similar. Single-dose everolimus co-administration did not affect the steady-state pharmacokinetics of CsA. Based on this information, pediatric patients will need a dose scaled down for body size, but can probably maintain the same twice-daily dosing schedule used in adults.

Transjugular intrahepatic portosystemic shunt prior to renal transplantation in a child with autosomal-recessive polycystic kidney disease and portal hypertension: A case report

Autosomal-recessive polycystic kidney disease (ARPKD) can cause renal failure and portal hypertension in children. Portal hypertension may complicate the course of renal transplantation (Tx). We report the successful outcome of a patient with end-stage renal disease (ESRD) and portal hypertension treated with transjugular intrahepatic portosystemic shunt (TIPS), a minimally invasive endovascular technique of portosystemic shunt, prior to renal Tx.

Neoral pharmacokinetics in Latino and Caucasian pediatric renal transplant recipients

Interpopulation variability of drug pharmacokinetics (PK) has been described. For example, the systemic clearance of nifedipine is higher in Mexicans than Caucasians. African-Americans have a lower cyclosporine bioavailability than Caucasians. Limited data are available in the Latino population. Under identical conditions, we compared the PK profile of Neoral (cyclosporine for microemulsion) obtained in stable pediatric renal transplant recipients of Latino and Caucasian origin. A slightly lower area under the curve (AUC) when corrected for dose per body surface area or per kilogram of body weight was observed in Caucasians compared with Latinos. This difference was more pronounced in the younger age group (< 12 years) with a higher peak-to-trough ratio. However, the Caucasians required a higher dosage of Neoral than the Latinos to achieve that same AUC. There was no difference between the groups in the time (tmax) to reach maximal concentration (Cmax) of Neoral. A higher apparent clearance of the drug was observed in the Caucasians compared with the Latinos, especially in the younger age group. No differences in pre- and post-dose levels were observed between the two groups. These differences might affect dose adjustment between the two subpopulations.

1,25-Dihydroxyvitamin D3--a hormone with immunomodulatory properties

The active vitamin D metabolite, 1,25-dihydroxyvitamin D3[1,25-(OH)2D3], exerts immunosuppressive activity. At a cellular and molecular level, the hormone preferentially targets helper T cell activity (Th1) by inhibiting the secretion of both IL-2 and IFN-gamma by Th1 and by suppressing the secretion pro-Th1 cytokine IL-12 by antigen-presenting cells. The active metabolite further inhibits class II antigen expression and enhances suppressor cell activity. In animal models of autoimmunity, 1,25-(OH)2D3 prevents the development of experimental autoimmune encephalomyelitis, reduces the incidence of diabetes, and attenuates murine lupus. The hormone also prolongs graft survival in animal models of transplantation. In humans, non-classical use of 1,25-(OH)2D3 has led to an anti-proliferative effect in psoriasis, antineoplastic effect in prostate cancer, and immunomodulatory effect in scleroderma. The development of less hypercalcemic analogs might open a new therapeutic area for vitamin D3.

Nonsteroidal anti-inflammatory drug use in adolescence

Nonsteroidal anti-inflammatory drugs (NSAIDs) have been recently released as over-the-counter drugs making them more widely available to the general public. We present five cases of adolescents with complications, including acute and chronic renal failure, related to the use of NSAIDs. Risk factors for NSAID nephrotoxicity include chronic illness, dehydration, ethanol and use of other medications. Adolescents should be educated about the risks and prevention of NSAID toxicity.

Intraocular pressure change measured by Goldmann tonometry after laser in situ keratomileusis

PURPOSE

To assess the accuracy of Goldmann tonometry after laser in situ keratomileusis (LASIK).

SETTING

University-based refractive surgery group (Clinique du Laser Visuel).

METHOD

The database of patients who had LASIK was retrospectively reviewed. Preoperative and postoperative intraocular pressure (IOP) was measured in 145 patients. The correlation between decrease in IOP and various preoperative and intraoperative parameters was evaluated by regression analysis. Only one eye in patients having bilateral surgery was used for statistical analysis.

RESULTS

Laser in situ keratomileusis was associated with a mean decrease in IOP of 1.9 mm Hg +/- 2.9 (SD). There was no significant correlation between the decrease and any parameter evaluated.

CONCLUSION

Intraocular pressure after LASIK decreased by a mean of 1.9 +/- 2.9 mm Hg. The cause of the decrease remains unknown.

The syndrome of autoimmune interstitial nephritis and membranous nephropathy

A 2-year-old male patient was evaluated for Fanconi syndrome with hypertension and failure to thrive. Renal biopsy revealed autoimmune interstitial nephritis with membranous nephropathy. The patient developed autoimmune hemolytic anemia and intractable diarrhea with villous atrophy of the jejunum. He progressed to end-stage renal disease and was transplanted without recurrent disease. Immune work-up done prior to immunosuppressive therapy showed marked elevation of IgE. Studies of T lymphocyte cytokine production showed normal production of interleukin-4 but depressed levels of interferon-gamma. The simultaneous occurrence of autoimmune interstitial nephritis and membranous nephropathy in a young male represents a unique syndrome. Abnormalities of T lymphocyte subpopulations and their cytokines may be involved in the pathogenesis of this disorder.

Effect of occlusive pressure patching on the rate of epithelial wound healing after photorefractive keratectomy

PURPOSE

This study measured the effect of pressure patching on the rate of epithelial wound healing in 41 myopic patients after photorefractive keratectomy (PRK).

METHODS

On day 0, mechanical debridement was done to remove the central 6.5 mm diameter of epithelium. Subsequently, a 5.0 mm diameter photoablation was performed, the depth of ablation being proportional to the degree of myopia (-1.0 to -6.0 diopters). The patients were discharged with an application of antibiotic/steroid ointment (A/S) followed by pressure patching. On day 1, the epithelial defects were stained with fluorescein and photographed. The patients were then randomized prospectively into two groups: Group 1 was pressure patched after application of A/S ointment; Group 2 received A/S ointment twice a day without patching. A photograph of the remaining epithelial defect was taken on day 2. The area of the epithelial defect was measured with a computerized image analyzer. Wound diameter (radius) was used to calculate the epithelial healing rate (EHR).

RESULTS

Between days 1 and 2, the mean EHR in Group 1 was 0.072 +/- 0.005 mm/hr and in Group 2, 0.056 +/- 0.004 mm/hr (P < 0.05). There was no correlation between the EHR and patient gender or the degree of myopia. However, a correlation was noted between patient age and wound size on day 1.

CONCLUSION

Pressure patching significantly accelerated the EHR following PRK.

Anterior chamber fluid contamination after uncomplicated phacoemulsification

This study determined the rate of anterior chamber aerobic bacterial contamination in 103 eyes that had uncomplicated posterior chamber phacoemulsification. Anterior chamber fluid was aspirated on completion of surgery. Cultures of sterile balanced salt solution served as a control. Of 103 anterior chamber cultures, 4 (3.9%) showed contamination; however, 3 of 103 control cultures (2.9%) also grew micro-organisms. These findings suggest a very low rate of aerobic bacterial contamination after uncomplicated phacoemulsification and underscore the importance of control cultures when determining contamination rates.

Effect of timolol vs. acetazolamide on sodium hyaluronate-induced rise in intraocular pressure after cataract surgery

This prospective study was done to compare the efficacy of timolol and acetazolamide in lowering the intraocular pressure (IOP) secondary to the use of sodium hyaluronate (Healon) in cataract surgery. Fifty patients undergoing extracapsular cataract extraction and implantation of a posterior chamber lens were randomly assigned to one of four treatment groups: no viscoelastic (10 patients), Healon with 0.5% timolol drops postoperatively (12 patients), Healon with acetazolamide postoperatively (16 patients), or Healon only (12 patients). The IOP was measured during the first 24 hours after surgery. Sodium hyaluronate caused a marked increase in IOP in the early (6 to 12 hours) postoperative period. Timolol proved to be more effective than acetazolamide in controlling this pressure increase.

Transient hemiparesis associated with monoclonal CD3 antibody (OKT3) therapy

OKT3 therapy for prevention or reversal of allograft rejection has been associated with a constellation of acute systemic side effects, defined as an OKT3 first-dose reaction. Specific neurologic syndromes, including aseptic meningitis and diffuse encephalitis, have also been observed. This report describes a 12-year-old girl with steroid-resistant renal allograft rejection who developed hemiparesis associated with initiation of OKT3 therapy.

Streptokinase thrombolysis of a chronically thrombosed mitral prosthetic valve

Thrombus obstruction of a prosthetic heart valve is usually treated surgically. We report a well-documented case of an obstructed mitral prosthetic valve where fibrinolytic treatment was successful. Furthermore the thrombus formation probably had occurred 6 months earlier. Thus fibrinolysis appears to be a safe alternative to surgery although late occurrence of thrombosis may be possible.

The various renal manifestations of the nephropathic form of cystinosis

Three phenotypic forms of cystinosis (nephropathic, juvenile-onset and benign adult forms) are well recognized. That not all infants and children have the classical nephropathic form with Fanconi's syndrome is illustrated by 2 of the 3 patients in this report. Case 1 had the typical nephropathic form with generalized proximal tubular dysfunction. In contrast, case 2 had transient features of Bartter's syndrome which preceded the manifestations of Fanconi's syndrome. Case 3 was more complex because he first presented with a syndrome of nephrogenic diabetes insipidus. He then developed features of Fanconi's syndrome as well as metabolic acidosis, hyponatremia and hyperkalemia. The failure of deoxycorticosteroid administration to elevate the serum concentration suggested, in retrospect, that he may also have had a form of acquired pseudohypoaldosteronism.

Induction of tolerance to factor VIII in a child with a high-titer inhibitor: in vitro and in vivo observations

High dose factor VIII concentrate was infused over 12 months in a 3-year-old child with hemophilia A and a high-titer inhibitor. This regimen was successful in producing clinical tolerance to the factor VIII and was associated with a fall of inhibitor titer from 85 BU to less than 1 BU. Subsequently, a rise in inhibitor to peak at 3.5 BU correlated with a decrease in infusion dose. In vitro studies using a microdroplet assay for immunoglobulin synthesis in the presence of varying concentrations of factor VIII was carried out prior to the clinical trial. This system indicated that the patient's peripheral blood mononuclear cells were stimulated to release IgG by 0.01 U/ml factor VIII coagulant activity and inhibited at 0.9 U/ml FVIIIc. Lymphocyte subsets were monitored during the course of therapy. The ratio of Leu-3a+/Leu-2a+ (helper/suppressor) varied considerably, fluctuating between a peak of 4.4 and low point of 0.6, with the initial pretrial ratio being 1.2.

Hemodynamic and coronary effects of intravenous labetalol in coronary artery disease

Labetalol, an alpha and beta receptor blocking agent, was evaluated in 11 patients with documented coronary artery disease and stable angina. The mean dose of labetalol was 1.5 (range 1 to 2) mg/kg. Cardiovascular effects began within 1 minute after injection and were maximal within 10 minutes. Mean arterial pressure decreased from 105 +/- 13 to 81 +/- 10 mm Hg (p less than 0.0001), heart rate from 70 +/- 10 to 66 +/- 7 beats/min (p less than 0.05) and the pressure-rate product from 10,322 +/- 2,344 to 7,171 +/- 1,650 (p less than 0.001). Cardiac output and pulmonary wedge pressure did not change significantly. Mean pulmonary arterial pressure decreased from 20 +/- 3 to 16 +/- 2 mm Hg (p less than 0.005). Systemic and pulmonary resistances also decreased significantly (p less than 0.0001 and p less than 0.01, respectively). Coronary sinus flow increased from 107 +/- 26 to 118 +/- 25 ml/min (p less than 0.01) and coronary vascular resistance decreased from 1.0 +/- 0.2 to 0.77 +/- 0.1 mm Hg/ml per min (p less than 0.001). Labetalol may be a useful adjunct in the treatment of angina not only because it diminishes myocardial oxygen requirements but also because it improves coronary hemodynamics. Thus, labetalol appears to have some advantage compared with the usual beta blocking agents with their potentially detrimental effects on coronary hemodynamics.

The role of coronary thrombosis in myocardial infarction: further evidence shown by intracoronary thrombolysis with streptokinase

Myocardial infarction is usually caused by a thrombus occurring on a significant coronary lesion. A 60-year-old male was admitted with an acute evolving anterior myocardial infarction. Three hours after the beginning of chest pain, the electrocardiogram showed ST-segment elevation in the anterior and lateral leads which persisted despite intravenous nitroglycerin (100 mcg/min). One hour later, an angiogram showed complete obstruction at the origin of the left anterior descending artery (LAD). After intracoronary streptokinase (250,000 units) the LAD opened and a 90% obstruction was seen at its origin. However, an anterior myocardial infarction occurred. One month later, an angiogram showed a slight irregularity at the origin of the LAD. Thus, this case demonstrates that 1) a myocardial infarction may occur with a near normal coronary artery, and 2) a thrombus may occur at the site of a slight coronary irregularity.

False aneurysm of the ascending aorta presenting as an acute myocardial infarction: a late complication of aortocoronary bypass

After coronary bypass surgery, a 40-year-old man developed disruption of the site of cannulation of the ascending aorta. The false aneurysm which ensued presented as recurrent episodes of spontaneous angina and myocardial infarction ending in coronary death 48 days after surgery. the aortic origin of all three permeable coronary bypasses were strangulated by the hematoma. Awareness of this unusual potential hazard is essential, since an early suspicion would lead to proper diagnostic interventions and reoperation.

Combined hemodynamic effects of dobutamine and IV nitroglycerin in congestive heart failure

The combined and separate hemodynamic effects of dobutamine and IV nitroglycerin were compared in 12 patients with chronic congestive heart failure (nine with ischemic heart disease, two with idiopathic congestive cardiomyopathy, and one with valvular heart disease). Dobutamine (7.1 micrograms/kg/min) increased cardiac index from 2.4 +/- 0.4 to 3.4 +/- 0.9 L/min/m2 (P < 0.001) and decreased pulmonary wedge pressure from 28 +/- 5 to 16 +/- 4 mm Hg (P < 0.001) while nitroglycerin (127 micrograms/min) alone increased cardia index to 2.8 L/min/m2 (P < 0.001) and decreased wedge pressure to 14.3 mm Hg (P < 0.001). With both drugs, cardiac index increased to 3.5 +/- 0.6 L/min/m2; (NS compared to dobutamine alone) wedge pressure decreased to 11 +/- 4L/min/m2 (P < 0.05 compared to dobutamine alone). Those beneficial hemodynamic effects occurred without a significant change in the double product of heart rate and blood pressure, and were associated with an improvement in the transmyocardial gradient. Thus, the greatly enhanced ventricular performance with dobutamine + nitroglycerin was associated with a better relationship between myocardial oxygen demand and supply.

Effects of angiographic contrast media on colloid oncotic pressure

Angiographic contrast media are known to induce alterations in cardiovascular dynamics which may result in acute pulmonary edema. The risk of pulmonary edema was previously shown to be negatively correlated to the level of colloid oncotic pressure (COP). It was also shown that the gradient between COP and left ventricular end-diastolic pressure (LVEDP) represents a better predictor of pulmonary edema than does LVEDP alone. The present report evaluates the effects of a bolus injection of contrast media on those pressures, as predisposing factors for pulmonary edema. Our data are based on 15 unselected patients admitted for coronary angiography. The plasma volume increased by 16.5% (2,903 to 3,384 ml.) at two minutes after injection of a 50 c.c. bolus of meglumine diatrizoate (Renographin 76%) and had returned towards normal at 30 minutes. In parallel the COP decreased from 23.4 +/- 2.4 to 19.6 +/- 2.3 mm. Hg (p < 0.001) to return the 22.7 +/- 2.6. The COP-LVEDP gradient decreased by 8.7 mm. Hg (8.4 to -0.3, P < 0.001). Such a gradient was well within the danger zone of pulmonary edema. These findings further clarify the mechanisms of pulmonary edema induced by contrast media.

[An ocular complication of amniocentesis]

An amniocentesis was performed two days prior to delivery by cesarian section, of a normal looking baby. Two days after birth, the pediatrician noticed the presence of a hyphema in the left eye. An examination under general anesthesia revealed a small laceration of the cornea with trapping of a small part of the iris in the wound. The needle used for the amniocentesis is presumed to be responsible for the wound of the cornea. This is the second such case to be reported in the literature.

Early surgical intervention for acute valvular dysfunction secondary to bacterial endocarditis

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