Precorneal retention time of ocular lubricants measured with fluorophotometry in healthy dogs.

OBJECTIVE: Determine the precorneal retention time of five different ocular lubricants commonly used in dogs. ANIMALS STUDIED: Six healthy Beagle dogs (n = 12 eyes). PROCEDURES: Five ocular lubricants were studied: Artificial Tears Solution® (1.4% polyvinyl alcohol), I-Drop® Vet Plus (0.25% hyaluronate), Optixcare® Eye Lube Plus (0.25% hyaluronate), Systane® Ultra (0.4% polyethylene glycol 400 and 0.3% propylene glycol), and Artificial Tears Ointment® (mineral oil/white petrolatum). Each lubricant was mixed with 10% sodium fluorescein to achieve 1% fluorescein formulations. Following topical administration of 35 mg in each eye, tear fluid was collected with capillary tubes at selected times (0, 1, 5, 10, 20, 30, 40, 50, 60, 90, 120, 180 min) and fluorescein concentrations were measured with a computerized scanning ocular fluorophotometer. RESULTS: Tear fluorescence was significantly greater with Artificial Tears Ointment® compared with other lubricant formulations from 1 to 20 min post-administration. Median (range) precorneal retention times were significantly different among the 5 lubricants, ranging from 40 minutes (20-90 min) for Artificial Tears Ointment®, 35 min (20-90 min) for Systane® Ultra, 30 min (10-60 min) for I-Drop® Vet Plus, 25 min (10-60 min) for Optixcare® Eye Lube Plus, and 10 min (10-20 min) for Artificial Tears Solution®. Precorneal retention time was significantly lower for Artificial Tears Solution® compared with the other 4 formulations. CONCLUSIONS: This study established normative data for the retention time of common lubricants on the ocular surface of dogs, which may be used to guide clinicians with their choice of lubricant and frequency of administration.

Proliferation signal inhibitors and post-transplant malignancies in heart transplantation: practical clinical management questions.

Although malignancy is a major threat to long-term survival of heart transplant (HT) recipients, clear strategies to manage immunosuppression in these patients are lacking. Several lines of evidences support the hypothesis of an anticancer effect of proliferation signal inhibitors (PSIs: mammalian target of rapamycin [mTOR] inhibitors) in HT recipients. This property may arise from PSI's ability to replace immunosuppressive therapies that promote cancer progression, such as calcineurin inhibitors or azathioprine, and/or through their direct biological actions in preventing tumor development and progression. Given the lack of randomized studies specifically exploring these issues in the transplant setting, a collaborative group reviewed current literature and personal clinical experience to reach a consensus aimed to provide practical guidance for the clinical conduct in HT recipients with malignancy, or at high risk of malignancy, with a special focus on advice relevant to potential role of PSIs.

Optimal pressure for low pressure controlled reperfusion to efficiently protect ischemic heart: an experimental study in rats.

Recent work has demonstrated the benefit of low pressure (LP) reperfusion to protect the heart undergoing an ischemic insult. The goal of the present study was to determine the optimal pressure for the application of LP reperfusion. Isolated rats hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion with a pressure fixed at 100 cm H(2)O (normal pressure [NP] = control group), 85 cm (group LP [low pressure]-85), 70 cm (group LP-70), or 55 cm (group LP-55). Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring lactate dehydrogenase (LDH) and creatine kinase (CK) leakage in the coronary effluents. Functional recovery was progressively and significantly improved with decreased perfusion pressure. Rate-pressure product (RPP) averaged 3765 +/- 408, 6824 +/- 439, and 12,036 +/- 664 mm Hg/min, respectively, among the control, LP-85, and LP-70 groups (P < .001, LP-70 vs other groups). However, RPP collapsed in the LP-55 group. Similarly, necrosis as measured by LDH and CK leakage progressively reduced between LP-100 and LP-70 hearts (P < .01), with a drastic increase in enzyme in the LP-55 group. In conclusion, this study demonstrated that 70 cm H(2)O is an optimal LP to improve postischemic contractile dysfunction and attenuate necrosis during reperfusion.

Cyclosporine-related posterior reversible encephalopathy syndrome after heart transplantation: should we withdraw or reduce cyclosporine?: case reports.

Cyclosporine (CsA) related encephalopathy has not been well documented after heart transplantation. We report 2 cases of posterior reversible encephalopathy syndrome (PRES). The first case was a 68-year-old woman who underwent heart transplantation and received immunosuppression with mycophenolate mofetil, prednisone, and CsA. On day 14, she developed arterial hypertension, headache, visual disturbances, and generalized seizures. Fluid-attenuated inversion recovery magnetic resonance imaging (MRI) of the brain showed diffuse and bilateral high signals in the frontal posterior and the occipital areas. The second case was a 19-year-old man with a heart transplant receiving immunosuppression with prednisone and CsA. On day 44, he developed acute headache and generalized seizures. T2-weighted MRI of the brain showed diffuse high signals in the cerebellum, right lenticular and occipital areas. In both cases blood CsA concentration was therapeutic. Both cases recovered but in the first case neurologic findings were reversed only after CsA withdrawal.

Lack of effect of a topical regenerative agent on re-epithelialization rate of canine spontaneous chronic corneal epithelial defects: A randomized, double-masked, placebo-controlled study.

Spontaneous chronic corneal epithelial defects (SCCEDs) are characteristic ulcers in dogs that are refractory to healing. The aim of the study was to evaluate the use of a topical regenerative agent to promote healing of SCCEDs. Nineteen dogs (20 eyes) were randomized to receive either regenerative agent (10 eyes) or placebo (10 eyes) every 48h following corneal debridement, which was repeated 1 week later if the SCCED had not yet healed. The mean±standard deviation time to re-epithelialization was 17.3±12.8 days for the group treated with a topical regenerative agent and 19.3±11.7 days for the group treated with a placebo; the cumulative healing rates were not statistically different (P>0.650). A positive association was found between the initial size of the ulcer and the time to re-epithelialization (r=0.555, P=0.011). Although well tolerated by dogs, there was no therapeutic advantage in using a topical regenerative agent for re-epithelialization of SCCEDs.

Optimal time duration for low-pressure controlled reperfusion to efficiently protect ischemic rat heart.

Previous studies have shown the capacity of low-pressure (LP) reperfusion to protect the ischemic heart. The present study sought to determine the optimal time for the application of LP reperfusion. Isolated rat hearts (n = 30) were exposed to 40 minutes of global warm ischemia followed by 70 minutes of reperfusion. Reperfusion was performed under LP (LP = 70 cm H(2)O) for 0 (control group), 5 (group LP-5), 10 (group LP-10), 30 (group LP-30), or 60 (group LP-60) minutes. Following the LP period the hearts were reperfused with normal pressure (100 cm H(2)O) until the end of reperfusion. Cardiac function was assessed during reperfusion using the Langendorff model. Myocardial necrosis was assessed by measuring LDH leakage in the coronary effluents. Functional recovery was reduced among the control and LP-5 groups with rate-pressure products (RPP) averaging 3788 +/- 499 and 5333 +/- 892 mm Hg/min, respectively. RPP was significantly improved in other groups with RPP averaging 7363 +/- 1159, 7441 +/- 863, and 7269 +/- 692 mm Hg/min in LP-10, LP-30, and LP-60 (P < .01). Similarly, necrosis measured by LDH leakage was significantly reduced in LP-10, LP-30, and LP-60 hearts (P < .01). This study demonstrated that LP reperfusion improves postischemic contractile dysfunction and attenuates necrosis when applied for at least 10 minutes.

Identification and characterization of two genes (MIP-1beta, VE-CADHERIN) implicated in acute rejection in human heart transplantation: use of murine models in tandem with cDNA arrays.

BACKGROUND: Genes and mechanisms of action involved in human acute rejection after allogeneic heart transplantation remain to be elucidated. The use of a murine allograft model in tandem with cDNA arrays and quantitative real-time polymerase chain reaction (Q-PCR) can greatly help in identifying key genes implicated in human heart acute rejection. METHODS AND RESULTS: Hearts from Balb/c mice were either not transplanted or transplanted heterotopically in the abdomen of Balb/c (isografts) and C57BL/6 (allografts) mice. Histological analysis showed acute rejection only in allografts. Total RNA was extracted from isografts (n=3), allografts (n=4), and not transplanted hearts (n=4); reverse transcribed; and labeled with P32. Each probe was hybridized to cDNA macroarrays. Eight genes were overexpressed and 7 genes were underexpressed in allografts compared with isografts. Macrophage inflammatory protein-1beta (MIP-1beta), an overexpressed gene, and VE-cadherin, an underexpressed gene, were validated by immunohistochemistry and Q-PCR in the murine models. Genes of interest, validated in the 3 murine groups, were then investigated in human heart tissues. Immunohistochemistry and Q-PCR performed on endomyocardial biopsies after heart transplantation showing no rejection (n=10) or grade IB (n=10) or IIIA (n=10) rejection, according to International Society of Heart and Lung Transplantation criteria, confirmed the results obtained from the murine model. CONCLUSIONS: We have demonstrated that the upregulation of MIP-1beta and downregulation of VE-cadherin may strongly participate in human acute heart rejection.

Effects of dietary supplementation with alpha-tocopherol on myocardial infarct size and ventricular arrhythmias in a dog model of ischemia-reperfusion.

OBJECTIVES: We investigated whether dietary supplementation with the antioxidant vitamin alpha-tocopherol (500 mg daily) might reduce lethal ventricular arrhythmias and infarct size. BACKGROUND: Previous studies suggested that dietary supplementation with alpha-tocopherol may be associated with a reduced risk of ischemic heart disease. However, the mechanism of this protection remains unknown. METHODS: Beagle dogs were randomized to either a supplemented or a control group. Because of the low mortality rate in the supplemented group, five dogs were added to the control group. After 2 months, dogs were anesthetized and underwent a 2-h coronary artery occlusion and 6-h reperfusion. Plasma vitamin E, retinol and malondialdehyde concentrations were assessed in all dogs. RESULTS: Fourteen dogs (11 of 25 control vs. 3 of 19 supplemented dogs, p < 0.05) developed ventricular fibrillation during either ischemia or reperfusion. Malondialdehyde concentrations were higher in dogs that subsequently developed arrhythmias (2.7 +/- 0.2 mumol/liter, mean +/- SEM) compared with dogs that did not (2.1 +/- 0.2 mumol/liter, p = 0.03). Among survivors with significant ischemia, infarct size was larger in supplemented (n = 12, 58.5 +/- 3.3% of area at risk) than in control (n = 11, 41.9 +/- 6.5%, p < 0.04) dogs. In addition, for a given collateral flow, supplemented dogs (n = 16) developed larger infarct size than control dogs (n = 15, p < 0.001, analysis of covariance). CONCLUSIONS: The data suggest that dietary alpha-tocopherol supplementation prevented lethal ventricular arrhythmias associated with ischemia and reperfusion. However, its influence on infarct size and long-term prognosis warrants further investigation.

Chronic renal failure and end-stage renal disease are associated with a high rate of mortality after heart transplantation.

The aim of the study was to analyze the etiology, the factors for progression of chronic renal failure to end-stage-renal disease (ESRD), and the influence of ESRD on the survival rate among a cohort of 59 heart transplant patients (HTP) referred for the management of chronic renal failure (CRF). At the time of the first nephrology consultation (6 +/- 4.25 years after cardiac transplantation) the mean creatininemia was 261.5 +/- 99 micromol/L and mean creatinine clearance (Cockcroft formula) was 32 +/- 15 mL/min. The cause of CRF were calcineurin inhibitor toxicity in 38.9% of patients, vascular events in 15.2%, hemolytic uremic syndrome in 5%, membranous glomerulopathy in 3.3%, diabetes in two patients, focal/segmental glomerulosclerosis in 3.3%, renal hypoplasia in 1.7%, and unknown in 27%. Evolution to ESRD occurred in 38.9% of patients: 17 patients started hemodialysis, three peritoneal dialysis, and two received a preemptive kidney transplantation. Creatininemia (micromol/L) at the time of nephrology referral was 229.2 +/- 72.6 versus 315.8 +/- 113.4 (P < .001) and creatinine clearance (mL/min) was 34.9 +/- 15.1 versus 27.3 +/- 13.7 (P = .049) for patients with CRF versus ESRD, respectively. Both proteinuria (g/24 hours) of 1 +/- 2.2 versus 2.3 +/- 1.8 (P = .02) and tobacco use in 35.1% versus 54.4% (P = .045) were significantly associated with progression of CRF, while age at the time of heart transplantation, cause of cardiac failure and renal failure, high blood pressure, type 2 diabetes, dyslipidemia, alcoholism, cirrhosis, and cerebral vascular accident were not. Death occurred in 18 HTP: 50% of patients with ESRD and 18.5% of patients with CRF-a 2.6 relative risk of of death in HTP patients with ESRD compared with HTP with CRF only (P < .01).

Acute myocardial infarction in dogs with experimental diabetes.

OBJECTIVE: The aim was to examine whether diabetes interferes with the development of myocardial injury in a canine ischaemia-reperfusion model. METHODS: Non-insulin-requiring diabetes was induced in dogs by the streptozotocin-alloxan method. After 75 d, the dogs were anaesthetised and myocardial infarction was provoked by occluding the left anterior descending coronary artery for 2 h followed by 6 h reperfusion. RESULTS: Diabetic dogs had higher blood glucose [9.4(SEM 1) mmol.litre-1], fructosamine [417(57) mumol.litre-1], and glycated haemoglobin [3.3(0.7)%], than control dogs [5.5(0.6), p = 0.04, 243(15), p = 0.01, and 0.7(0.2), p = 0.003, respectively], and they also had higher serum lipids (p = 0.001) and platelet aggregation (p = 0.03). Area at risk was similar in diabetic and control dogs but in contrast to controls (r = 0.78, p = 0.007), area at risk and infarct size were not correlated in diabetics (r = 0.08). In both groups, collateral flow was the major determinant of infarct size: r = -0.73 in controls (p = 0.02) and -0.97 in diabetics (p = 0.001). In spite of higher subendocardial collateral flow in diabetics [representing 21.6(6)% of the flow in the corresponding non-ischaemic zone] than in controls [11.2(6)%], infarct size was similar in both groups. However, the mean observed infarct size in the diabetic group [7.5(2.8)% of the left ventricle] was significantly (p < 0.03) larger than the mean predicted infarct size [5.2(2)%]. Multivariate analysis confirmed that diabetes, as well as collateral flow, is an independent (p = 0.03) predictor of infarct size. CONCLUSIONS: For a given collateral flow, diabetic dogs develop larger infarcts than controls. Further studies are required to investigate the biochemical mechanism(s) underlying this deleterious effect. However, this may partly explain the poor prognosis of myocardial infarction in diabetic persons.

Intracoronary administration of the alpha 1-receptor agonist, methoxamine, does not reproduce the infarct-limiting effect of ischemic preconditioning in dogs.

BACKGROUND: The cardioprotective effect of ischemic preconditioning has been hypothesized to occur through one or more signalling mechanisms which activate protein kinase C. Stimulation of alpha 1-adrenergic receptors by catecholamines released during the preconditioning episodes of ischemia is one of these putative signalling mechanisms. METHODS: To determine whether stimulation of alpha 1-adrenergic receptors before an ischemic challenge can mimic preconditioning, anesthetized dogs were treated with 4 intracoronary infusions of methoxamine HCl (10 micrograms/kg/min; n = 8), each 5 min in duration and followed by 5 min of washout. Control dogs (n = 10) were given similar infusions of 0.9% NaCl. A third group of dogs was preconditioned with 4 cycles of 5 min ischemia, each followed by 5 min of reperfusion (n = 8). All dogs then underwent 60 min of ischemia (circumflex coronary occlusion) followed by 3 h of reperfusion. Infarct size (expressed as % of area-at-risk) was measured with TTC macrochemistery and analyzed (using analysis of covariance [ANCOVA]) with respect to coronary collateral blood flow (measured using radioactive microspheres). RESULTS: Methoxamine markedly increased systemic arterial and left atrial pressures prior to but not during the ischemic challenge. Baseline predictors of infarct size were not different among the groups. Mean infarct size (adjusted from ANCOVA) did not differ between control and methoxamine-treated groups, 28.3 +/- 2.8% vs. 29.7 +/- 3.2%, respectively (P = NS), but was only 12.7 +/- 3.2% in the preconditioned group (P < 0.01 vs. control and methoxamine). CONCLUSIONS: A series of methoxamine infusions before an ischemic challenge did not affect infarct size. Thus, stimulation of alpha 1-adrenergic receptors alone is insufficient to mimic the cardioprotective effect of ischemic preconditioning in this canine model.

Thiopurine S-methyltransferase gene polymorphism is predictive of azathioprine-induced myelosuppression in heart transplant recipients.

Azathioprine (AZA) is metabolized via the cytosolic enzyme thiopurine S-methyltransferase (TPMT). TPMT activity exhibits genetic polymorphism with four prevalent (75%) mutant alleles TPMT*2 (G238C) and TPMT*3 (A719G and/or G460A) and a wild-type allele TPMT*1. To test the hypothesis that presence of these mutations is associated with greater toxicity of AZA in heart transplant recipients, 30 consecutive patients treated with AZA were followed up for the first month after heart transplant. Mutation of TPMT gene (mutation-specific polymerase chain reaction-based methods) was observed in four patients (A719G: n = 2; A719G plus G460: n = 2). Agranulocytosis did not occur in patients with the wild genotype. It occurred in the two patients with mutation A719G and there was a 40% drop in neutrophils in the two other patients. Discontinuation of AZA in the four mutant patients corrected for the drop. Presence of TPMT mutations is associated with a greater likelihood of agranulocytosis. Determination of these mutations could reduce the risk for hematological side-effects.

Should we still perform angioplasty and stenting of an unprotected left main coronary artery stenosis in heart transplant patients? Two new cases and a review of the literature.

Coronary balloon angioplasty with stent implantation has emerged as a possible alternative to bypass grafting or repeat transplantation in left main coronary stenosis in heart transplant patients. We report 2 new cases of stent implantation for unprotected and isolated left main stenosis in heart transplant patients. Despite an initially successful procedure, restenosis prompted the performance of bypass surgery in both patients. The relative advantages and disadvantages of available techniques of revascularization are discussed in the context of the literature.

Superparamagnetic iron oxide particles and positive enhancement for myocardial perfusion studies assessed by subsecond T1-weighted MRI.

Superparamagnetic iron oxide particles (SPIOs) are usually referred to as T2 MR contrast agents, reducing signal intensity (SI) on T2-weighted MR images (negative enhancement). This study reports the original use of SPIOs as T1-enhancing contrast agents, primarily assessed in vitro, and then applied to an in vivo investigation of a myocardial perfusion defect. Using a strongly T1-weighted subsecond MR sequence with SPIOs intravenous (IV) bolus injection, MR imaging of myocardial vascularization after reperfusion was performed, on a dog model of coronary occlusion followed by reperfusion. Immediately after the intravenous bolus injection of 20 mumol/kg of SPIOs, a positive signal intensity enhancement was observed respectively, in the right and left ventricular cavity and in the nonischemic left myocardium. Moreover, compared to normal myocardium, the remaining ischemic myocardial region (anterior wall of the left ventricle) appeared as a lower and delayed SI enhancing area (cold spot). Mean peak SIE in the nonischemic myocardium (posterior wall) was significantly higher than in the ischemic myocardium (anterior wall) (110 +/- 23% vs. 74 +/- 22%, Mann-Whitney test alpha < 1%, n1 = 6, n2-n1 = 0, U > 2). In conclusion, the T1 effect of SPIOs at low dose, during their first intravascular distribution, suggests their potential use as positive markers to investigate the regional myocardial blood flow and some perfusion defects such as the "no-reflow phenomenon."

Alteration of the left ventricular contractile reserve in heart transplant patients: a dobutamine stress strain rate imaging study.

BACKGROUND: Strain rate imaging (SRI), a recently developed Doppler-derived process, allows quantification of myocardial systolic function. We investigate whether SRI quantifies the contractile reserve during dobutamine stress tests in heart transplant patients (HT), when compared with normal individuals. METHODS: An incremental dobutamine test (5 to 40 microg/kg per minute) was performed in 10 HT and 15 control subjects, all of whom displayed normal coronary angiography. Gray-scale and color myocardial Doppler data were acquired in standard B-mode views at baseline, low-dose, peak, and recovery. Longitudinal SR was processed from the myocardial velocities for each segment. The changes in maximal systolic SR were used to quantify myocardial contractile reserve. RESULTS: Dobutamine infusion failed to induce clinical symptoms or electrocardiographic (ECG) changes in either group. Visually determined wall motion score was considered normal in all segments for each stage of the dobutamine stress. Heart rate was augmented similarly in both groups during dobutamine infusion. In controls, systolic SR increased gradually with incremental dobutamine dose and returned to baseline values upon recovery. Conversely, in HT patients, the increase in systolic SR was blunted at peak dobutamine, at which point it was significantly different vs controls. CONCLUSIONS: Quantitative assessment of myocardial function using SRI during dobutamine stress revealed an impaired contractile reserve in HT patients with normal coronary angiography. These subtle changes in regional myocardial function could not be identified using visual wall motion scoring. Additional studies are necessary to evaluate whether SR imaging detection of contractile reserve impairment will improve clinical efficiency or event prediction in this population.

[Hypervasopressinism during tuberculous meningitis]. / L'hypervasopressinisme au cours des méningites tuberculeuses.

In tuberculous meningitis there is a disturbance of control involving hyponatraemia and increased urinary elimination of antidiuretic hormone resulting in hypersecretion of vasopressin. This inappropriate secretion of antidiuretic hormone should not be confused with the Schwartz-Bartter syndrome, which is reserved for paraneoplastic syndromes. The pathophysiology remains poorly understood but its recognition in cases of lymphocytic meningitis is improved as the correct diagnosis has precise therapeutic implications.