Cloning and sequence analysis ofAlcaligenes faecalis nifHDK gene cluster

Total DNA ofAlcaligenes faeculis was probed with both the nifH and nifHD sequences fromK. pneumoniae.One positive band of about 4. 6 kb was discovered. This nifH homologous fragment was cloned into the vector pBluescript SK(+) to construct the recombinant plasmid pBZ1. The inserted fragment in pBZl was analyzed by physical mapping and was further subcloned for sequencing. It was found that thisA. faecalis nifHDK homology possessed a typical Sigma(54)-dependent promoter region with upstream activator sequence (UAS) and A-T rich region. The nifH and nifD ORFs were 888 and 1 476 bp long respectively. The GC contents of these two genes were about 61.6% and 60.0%. The intergenic regions of nifH-nifD and nifn-nifK were 101 and 105 bp respectively. There were separate SD sequences upstream of all the three genes. The deduced amino acid sequences of the nifH gene product (the Feprotein) and the nifD gene product (the Mo-Fe-protein) were also highly homologous to other nitrogen-fixing bacteria, especially in those conserved motif. TheA. faeculis sequence has the highest similarity to that ofA. uinelandii.

Lung neutrophil retention and injury after intestinal ischemia/reperfusion

OBJECTIVE

To define the mechanisms responsible for the lung leukosequestration and injury elicited by intestinal ischemia/reperfusion (I/R).

METHODS

The effect of 120 minutes of superior mesenteric artery occlusion and 90 minutes of reperfusion on neutrophil deformability, lung neutrophil retention, and pulmonary microvascular permeability was determined.

RESULTS

Compared with control surgery, intestinal I/R resulted in a significant increase in neutrophil stiffness (mean yield pressure [Pyield], 1.533 +/- 0.075 and 2.302 +/- 0.288 cm H2O, respectively) and lung neutrophil content (6.3 +/- 1.4 and 31.5 +/- 6.4 U/g wet weight, respectively). These changes were not affected by inhibition of neutrophil adherence before gut reperfusion. However, the increased lung microvascular permeability elicited by gut I/R (0.111 +/- 0.020 [control surgery] and 0.255 +/- 0.041 [I/R] mL/min/cm H2O/100 g lung tissue) was significantly attenuated by administration of antibodies directed against neutrophil or endothelial determinants of leukocyte adhesion.

CONCLUSIONS

The results of this study suggest that intestinal I/R is a potent inflammatory stimulus that elicits an increase in neutrophil stiffness and lung neutrophil retention independent of neutrophil-endothelial cell adhesion. In contrast, the increased lung microvascular permeability elicited by gut I/R is attenuated by strategies that interfere with neutrophil-endothelial cell adhesion.

[Employing deconvolution method for correcting scatter in radiography]

It is well known that the scattered-radiation (SR) results in degradation of the images contrast in digital X-ray radiograph. The main reason affecting radiographic image quality is the SR arising from interaction of the photons with object being radiographed and veiling glare from detector system in the II-TV chai imaging system. With the aim of improving the image quality, we employed the Gaussian function to approximate the scattered point spread function (PSF) and determined the fraction of SR, rho and the parameter, sigma experimentally on an individual system; then we built an inverse filter to process the digital chest X-ray images, which were acquired with the same system and transformed in 2-D Fourier tansform operation. The images processed were corrected by using a variable weihting factor and the resulting images are shown in this paper. The method provides a useful way for solving the problem of correction of the SR in digital X-ray images.

Complement-mediated lung injury and neutrophil retention after intestinal ischemia-reperfusion

Complement-mediated neutrophil activation appears to play an important role in ischemia-reperfusion (I/R) injury in a variety of tissues, including the heart, lung, and small bowel. The objective of this study was to determine whether inhibition of the alternative and classic complement cascades by administration of soluble complement receptor 1 (sCR1) prevents the increased neutrophil stiffness, lung neutrophil retention, and pulmonary microvascular injury elicited by a systemic inflammatory insult. Isolated lungs were perfused with blood obtained from animals subjected to 2 h of intestinal ischemia and 20 min of reperfusion (I/R) or control (nonischemic) surgery. Intestinal I/R resulted in a significant increase in neutrophil stiffness, lung neutrophil retention, and increased pulmonary microvascular permeability, effects that were prevented by administration of sCR1 before intestinal reperfusion. The results of this study suggest that I/R injury in the gut is a potent systemic inflammatory stimulus that induces complement-mediated neutrophil stiffness, lung neutrophil entrapment, and pulmonary microvascular dysfunction.

[The expression of Rb, p16 and cyclin D1 in 41 esophageal cancers]

D-type cyclins being considered as oncogenes promote progression of the cell through the G1 phase of the cell cycle by CDK4 mediated phosphorylation of the retinoblastoma protein. The activities of CDK4 is constrained by inhibitors such as p16, the product of the CDKN2 in tumor cells and primary tumors suggests that p16 acts as a tumor suppressor. We examined these proteins and genes by immunohistochemistry and in situ hybridization techniques in 41 primary esophageal cancers. Overexpression of cyclin D1 was revealed in 26/41 samples (63.4%) and also in the mucosa adjacent to the cancers in 10 of 26 cyclin D1 overexpression samples, which also have high levels of cyclin D1. P16 was undetectable in 13 of 41 samples. Interestingly, 17 of 24 Rb positive cancers had no or low p16, while 9 Rb-negative cancers showed high levels of p16. These results suggest that the overexpression of cyclin D1 may be a common molecular abnormality and an early molecular event in esophageal cancer, followed either by Rb loss, as occurred in Rb negative samples, or by loss of p16, as occurred in p16 negative samples. Cyclin D1 overexpression and Rb inactivation can coexist in esophageal cancer. However, there is a reciprocity between Rb inactivation and p16 expression in esophageal cancer. Thus, abnormality in the negative feedback regulatory pathway of cyclin D1/CDK4, Rb and p16 may be involved in the molecular mechanism of esophageal cancer.

[Changes of brain potentials related to visual attention during simulated weightlessness]

To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) during a simple visual selective response task were compared between head down tilt (HDT) and head up tilt (HUT) in 9 normal subjects. The results were: both the target (T) and non-target (NT) flash signals induced significant slow positive potentials which were supposed to be related to the attention activity; the amplitude of the positive potentials in the frontal regions decreased significantly especially for NT-ERPs during HDT as compared with that during HUT. The data provide new evidence indicating that the ability of brain response declined during simulated weightlessness and more attention should be paid to the study of brain function during space flight.

Delayed xenograft rejection in the concordant hamster heart into Lewis rat model

The inability to provide an adequate supply of human organs for clinical transplantation has created a strong interest in the use of nonhuman, especially nonprimate, organs. The first biological obstacle confronting such discordant transplantations is a series of violent reactions that result in hyperacute rejection of the xenograft. Significant advances in controlling hyperacute rejection have been achieved recently through the generation of transgenic pig donors bearing human complement regulatory proteins. However, when hyperacute rejection is averted, the xenografts are rejected in 2-70 days in spite of high-dose immunosuppression, by a process collectively termed delayed xenograft rejection. Delayed xenograft rejection is characterized by a refractoriness to conventional immunosuppression, extensive xenoreactive antibody deposition, and cellular infiltration that is dominated by macrophages. We have examined the features of extended host and graft response in the concordant hamster-to-rat xenotransplant model, where such features have historically been obscured by early graft destruction. Hamster hearts transplanted into rats do not encounter hyperacute rejection but are rejected within 3-4 days when xenoreactive antibody titers rise exponentially to levels that elicit a classical antibody- and complement-mediated acute xenograft rejection. We have successfully blocked acute xenograft rejection by a combination of immunosuppressive agents, leflunomide, and cyclosporine. Stopping the immunosuppression resulted in graft rejection that is histologically characterized by extensive xenoreactive antibody deposition and cellular infiltration that is predominantly composed of macrophages. We have noted the similarities between the histopathology of rejection of long-surviving concordant xenografts and that described for discordant xenografts and refer to the process of rejection of concordant grafts that have escaped acute xenograft rejection, delayed xenograft rejection.

Granulocyte colony-stimulating factor immunomodulation in the rat cardiac transplantation model

Granulocyte colony-stimulating factor (G-CSF) administration decreases tumor necrosis factor(TNF) release, an important mechanism in allograft rejection. to study G-CSF's possible antirejection effects, 30 Lewis rats underwent heart transplantation using Brown-Norway donors and were assigned varying dosages of recombinant human G-CSF (0, 20, 100, 250 and 500 microgram/kg/day) for 14 days following the operation. Recipients receiving 250 microgram/kg/day experienced an improvement in graft survival (12.3+/-4 days vs. 7.0+/-0.6 days, P>0.05, Breslow). In a separate cohort, G-CSF-treated recipients (250 microgram/kg/day x 14) killed at 2,4,and 6 days after transplantation revealed improved serial allograft biopsy grading scores versus untreated controls (P<0.001 stratified Wilcoxon). Significant reduction in serum TNF levels was noted in the G-CSF-treated animals (P<0.025, analysis of variance). These data describe a moderate antirejection effect of G-CSF administration. Inhibition of circulating TNF in the G-CSF-treated recipients may describe a marker or possible mechanism of this antirejection effect.

Resuscitative hypothermia

Resuscitative (postinsult) hypothermia is less well studied than protective-preservative (pre- and intra-arrest) hypothermia. The latter is in wide clinical use, particularly for protecting the brain during cardiac surgery. Resuscitative hypothermia was explored in the 1950s and then lay dormant until the 1980s when it was revived. This change occurred through the discoveries of brain damage mitigating effects after cardiac arrest in dogs, and after forebrain ischemia in rats, of mild (34 degrees C) hypothermia (which is safe), and of benefits derived from moderate hypothermia (30 degrees C) after traumatic brain injury or focal brain ischemia in various species. The idea that protection-preservation or resuscitation by hypothermia is mainly explained by its ability to reduce cerebral oxygen demand has been replaced by an increasingly documented synergism of many beneficial mechanisms. Deleterious chemical cascades during and after these insults are suppressed even by mild hypothermia. Prolonged moderate hypothermia carries some risks, e.g., arrhythmias, infection and coagulopathies. These side effects need further study. In global brain ischemia, protective-preservative mild hypothermia provides lasting mitigation of brain damage. Resuscitative mild hypothermia, however, may be beneficial in terms of long-term outcome or may merely delay the inevitable loss of selectively vulnerable neurons. Even if the latter is true, mild hypothermia may extend the therapeutic window for other interventions. This extension of the therapeutic window requires further documentation. After normothermic cardiac arrest of 11 mins in dogs, mild resuscitative hypothermia from 15 mins to 12 hours after reperfusion plus cerebral blood flow promotion normalized functional recovery with the least histologic damage seen thus far. Optimal duration of, and rewarming methods from, resuscitative hypothermia need clarification. The earliest possible induction of mild hypothermia after cardiac arrest seems desirable. Head-neck surface cooling alone is too slow. Among many clinically feasible rapid cooling methods, carotid cold flush and peritoneal cooling look promising. After traumatic brain injury or focal brain ischemia, which seem to still benefit from even later cooling, surface cooling methods may be adequate. Resuscitative hypothermia after cardiac arrest, traumatic brain injury, or focal brain ischemia should be considered for clinical trials.

Cerebral resuscitation from cardiac arrest: pathophysiologic mechanisms

Both the period of total circulatory arrest to the brain and postischemic-anoxic encephalopathy (cerebral postresuscitation syndrome or disease), after normothermic cardiac arrests of between 5 and 20 mins (no-flow), contribute to complex physiologic and chemical derangements. The best documented derangements include the delayed protracted inhomogeneous cerebral hypoperfusion (despite controlled normotension), excitotoxicity as an explanation for selectively vulnerable brain regions and neurons, and free radical-triggered chemical cascades to lipid peroxidation of membranes. Protracted hypoxemia without cardiac arrest (e.g., very high altitude) can cause angiogenesis; the trigger of it, which lyses basement membranes, might be a factor in post-cardiac arrest encephalopathy. Questions to be explored include: What are the changes and effects on outcome of neurotransmitters (other than glutamate), of catecholamines, of vascular changes (microinfarcts seen after asphyxia), osmotic gradients, free-radical reactions, DNA cleavage, and transient extracerebral organ malfunction? For future mechanism-oriented studies of the brain after cardiac arrest and innovative cardiopulmonary-cerebral resuscitation, increasingly reproducible outcome models of temporary global brain ischemia in rats and dogs are now available. Disagreements exist between experienced investigative groups on the most informative method for quantitative evaluation of morphologic brain damage. There is agreement on the desirability of using not only functional deficit and chemical changes, but also morphologic damage as end points.

Cerebral resuscitation from cardiac arrest: treatment potentials

In 1961, in Pittsburgh, PA, "cerebral" was added to the cardiopulmonary resuscitation system (CPR --> CPCR). Cerebral recovery is dependent on arrest and cardiopulmonary resuscitation times, and numerous factors related to basic, advanced, and prolonged life support. Postischemic-anoxic encephalopathy (the cerebral postresuscitation disease or syndrome) is complex and multifactorial. The prevention or mitigation of this syndrome requires that there be development and trials of special, multifaceted, combination treatments. The selection of therapies to mitigate the postresuscitation syndrome should continue to be based on mechanistic rationale. Therapy based on a single mechanism, however, is unlikely to be maximally effective. For logistic reasons, the limit for neurologic recovery after 5 mins of arrest must be extended to achieve functionally and histologically normal human brains after 10 to 20 mins of circulatory arrest. This goal has been approached, but not quite reached. Treatment effects on process variables give clues, but long-term outcome evaluation is needed for documentation of efficacy and to improve clinical results. Goals have crystallized for clinically relevant cardiac arrest-intensive care outcome models in large animals. These studies are expensive, but essential, because positive treatment effects cannot always be confirmed in the rat forebrain ischemia model. Except for a still-elusive breakthrough effect, randomized clinical trials of CPCR are limited in their ability to statistically document the effectiveness of treatments found to be beneficial in controlled outcome models in large animals. Clinical studies of feasibility, side effects, and acceptability are essential. Hypertensive reperfusion overcomes multifocal no-reflow and improves outcome. Physical combination treatments, such as mild resuscitative (early postarrest) hypothermia (34 degrees C) plus cerebral blood flow promotion (e.g., with hypertension, hemodilution, and normocapnia), each having multiple beneficial effects, achieved complete functional and near-complete histologic recovery of the dog brain after 11 mins of normothermic, ventricular fibrillation cardiac arrest. Calcium entry blockers appear promising as a treatment for postischemic-anoxic encephalopathy. However, the majority of single or multiple drug treatments explored so far have failed to improve neurologic outcome. Assembling and evaluating combination treatments in further animal studies and determining clinical feasibility inside and outside hospitals are challenges for the near future. Treatments without permanent beneficial effects may at least extend the therapeutic window. All of these investigations will require coordinated efforts by multiple research groups, pursuing systematic, multilevel research--from cell cultures to rats, to large animals, and to clinical trials. There are still many gaps in our knowledge about optimizing extracerebral life support for cerebral outcome.

Protective effect of diallyl sulfone against acetaminophen-induced hepatotoxicity in mice

Diallyl sulfone (DASO2) is a metabolite of diallyl sulfide, a compound derived from garlic. The present study investigated the effect of DASO2 as a protective agent against acetaminophen (APAP)-induced hepatotoxicity in mice. Oral administration of DASO2 protected mice against the APAP-induced hepatotoxicity in a dose- and time-dependent manner. When administered 1 hour prior to, immediately after, or 20 minutes after a toxic dose of APAP, DASO2 at a dose of 25 mg/kg completely protected mice from development of hepatotoxicity, as indicated by liver histopathology and serum lactate dehydrogenase levels. Protective effect was observed when DASO2 at a dose as low as 5 mg/kg was given to mice 1 hour prior to APAP administration. Oral administration of DASO2 to mice 1 hour prior to a toxic dose of APAP significantly inhibited the APAP-induced glutathione depletion in the liver. DASO2 treatment also decreased the levels of oxidative APAP metabolites in the plasma without affecting the concentrations of nonoxidative APAP metabolites. In liver microsomes, 0.1 mM of DASO2 caused a 60% decrease in the rate of APAP oxidation to N-acetyl-p-benzoquinone imine, which was determined as glutathione conjugate. This inhibitory effect is mainly due to its inhibition of cytochrome P450 2E1 activity; with an IC50 value equal to 0.11 mM. DASO2 also slightly inhibited the activities of P450s 3A and 1A, with IC50 values > 5 mM. Furthermore, a single oral dose of DASO2 inactivated P450 2E1- and P450 1A-dependent activities in liver microsomes. The results suggest that the protective effect of DASO2 against APAP-induced hepatotoxicity is due to its ability to block acetaminophen bioactivation mainly by the inactivation and inhibition of P450 2E1.

Improved cerebral resuscitation from cardiac arrest in dogs with mild hypothermia plus blood flow promotion

BACKGROUND AND PURPOSE

In past studies, cerebral outcome after normothermic cardiac arrest of 10 or 12.5 minutes in dogs was improved but not normalized by resuscitative (postarrest) treatment with either mild hypothermia or hypertension plus hemodilution. We hypothesized that a multifaceted combination treatment would achieve complete cerebral recovery.

METHODS

With our established dog outcome model, normothermic ventricular fibrillation of 11 minutes (without blood flow) was followed by controlled reperfusion (with brief normothermic cardiopulmonary bypass simulating low flow and low PaO2 of external cardiopulmonary resuscitation) and defibrillation at < 2 minutes. Controlled ventilation was provided to 20 hours and intensive care to 96 hours. Control group 1 (n = 8) was kept normothermic (37.5 degrees C), normotensive, and hypocapnic throughout. Experimental group 2 (n = 8) received mild resuscitative hypothermia (34 degrees C) from about 10 minutes to 12 hours (by external and peritoneal cooling) plus cerebral blood flow promotion with induced moderate hypertension, mild hemodilution, and normocapnia.

RESULTS

All 16 dogs in the protocol survived. At 96 hours, all 8 dogs in control group 1 achieved overall performance categories 3 (severe disability) or 4 (coma). In group 2, 6 of 8 dogs achieved overall performance category 1 (normal); 1 dog achieved category 2 (moderate disability), and 1 dog achieved category 3 (P < .001). Final neurological deficit scores (0% [normal] to 100% [brain death]) at 96 hours were 38 +/- 10% (22% to 45%) in group 1 versus 8 +/- 9% (0% to 27%) in group 2 (P < .001). Total brain histopathologic damage scores were 138 +/- 22 (110 to 176) in group 1 versus 43 +/- 9 (32 to 56) in group 2 (P < .001). Regional scores showed similar group differences.

CONCLUSIONS

After normothermic cardiac arrest of 11 minutes in dogs, resuscitative mild hypothermia plus cerebral blood flow promotion can achieve functional recovery with the least histological brain damage yet observed with the same model and comparable insults.

Pharmacologically induced regression of chronic transplant rejection

Chronic rejection, characterized by a progressive obliterative arteriopathy, is a major cause of graft failure in long-surviving human transplants for which there is no effective treatment. Leflunomide, an isoxazol derivative, has been shown to be a novel immunomodulatory drug that profoundly suppresses the immune response. In this study, 58 Fisher-344 rats received cardiac transplantation from Lewis rats. All the recipients were given CsA at 2.5 mg/kg for 5 days postoperatively. Without further treatments, the arterial intima was progressively injured by mononuclear cell infiltration and Ab deposition. Smooth muscle cell and fibroblast proliferation in the intima became a predominant phenomenon by day 90. CsA was ineffective in controlling the progress of arterial intimal thickening when treatment began on day 30. Leflunomide at 5 mg/kg failed to control arterial intimal thickening by day 60 when therapy began on day 30. However, the progress of arterial intimal thickening was significantly inhibited by day 90 when the dosage of leflunomide had been increased to 10 mg/kg on day 60. Combined therapy with leflunomide and CsA at 5 mg/kg for 30 days dramatically reversed the arterial thickening by day 60. After increasing the dosages of both leflunomide and CsA to 10 mg/kg on day 60, the combination therapy steadily controlled the chronic rejection. Only the combination therapy significantly down-regulated circulating antidonor IgM and IgG titers. In rat smooth muscle cell culture, this same drug combination had a synergistic inhibitory effect on proliferation. Therefore, the combination therapy of leflunomide and CsA could reverse and control the progress of chronic rejection, while leflunomide, at higher dosage as a monotherapy, could stabilize chronic rejection in this model. The mechanism of the regression of chronic rejection by leflunomide and cyclosporine may be related to their in vitro abilities to control not only lymphocyte but smooth muscle cell proliferation, as well. The synergistic effect of these two drugs on vascular smooth muscle cell proliferation in vitro may be an important part of this novel activity. This unique feature holds intriguing possibilities for treating established chronic rejection.

The effect of head-down tilt on brain potentials related to visual attention

To study the possible effect of simulated weightlessness on brain function state, the brain event-related potentials (ERPs) in a simple visual selective response task were compared between HDT and HUT in 9 normal subjects. The results were: The Target(T) and non-Target(NT) flash signals both induced significant slow positive potentials which were supposed to related to the attention state; the amplitude of the positive potentials in frontal regions decreased significantly especially for NT-ERPs during HDT compared with that during HUT. The data reported provide new evidence indicating that more attention should be paid on the brain function study during space flight.

ESR study on calcineurin

X-band electron spin resonance spectroscopy was used to investigate the binding of Mn2+ to the apo-forms of calcineurin and its A and B subunits. The results indicated the presence of 2 Mn2+ binding sites of different affinities (20 mumol/L and 60 mumol/L) in the calcineurin A subunit and 4 Mn2+ binding sites in the calcineurin subunit B, 2 high affinity and 2 low affinity binding sites with Kd's of 4 mumol/L and 90 mumol/L, respectively. Interestingly and quite surprisingly, Mn2+ binding to the holoenzyme was characterized by only 2 binding sites with Kd's of 7 mumol/L and 33 mumol/L. However, in the presence of calmodulin about 10 Mn2+ sites were detected, and the Mn2+ calmodulin-calcineurin complex exhibited enzymatic activity. These results, based on direct spectral measurements of the metal ligand, demostrate that Mn2+ binds to both free subunits of calcineurin in a manner distinct from binding to the holoenzyme. Also, the data suggest that conformational changes occur upon heterodimer formation and association of the holoenzyme with the regulatory protein calmodulin.

Peritoneal cooling for mild cerebral hypothermia after cardiac arrest in dogs

After normothermic cardiac arrest in dogs, we found that mild hypothermia (34 degrees C) of 1-2 h reduced brain damage, providing that hypothermia was achieved within 15 min of reperfusion. A clinically feasible rapid brain-cooling method is needed. As head-neck surface cooling alone in dogs was found to be too slow (0.1 degrees C/min), we reviewed peritoneal cooling in the Introduction and Discussion sections. PRELIMINARY EXPERIMENTS WITHOUT CARDIAC ARREST: In 5 dogs with spontaneous circulation and IPPV, 2 L of Ringer's solution at 10 degrees C were instilled into the peritoneal cavity, left for 5 min, and drained. Brain (tympanic membrane) temperature (Tty) decreased by a mean of 0.3 degrees C/min (12 min to 34 degrees C). Core (pulmonary artery) temperature (Tpa) decreased by a mean of 0.8 degrees C/min (5 min to 34 degrees C). COOLING AFTER CARDIAC ARREST: In our reproducible dog model of normothermic ventricular fibrillation cardiac arrest of 11 min (no flow), brief low-flow normothermic cardiopulmonary bypass (CPB) was used for reperfusion and restoration of spontaneous circulation (ROSC) within 2 min. In 24 dogs, mild hypothermia was induced by head-neck surface cooling with ice bags, starting with reperfusion, plus peritoneal lavage as above, starting with ROSC. All 24 dogs were resuscitated. Initial head-neck surface cooling alone over 2 min decreased Tty by only 0.15 degrees C/min. Subsequent additional peritoneal lavage decreased Tty by a mean of 0.3 degrees C/min (11 min to 34 degrees C); and Tpa 0.6 degrees C/min (7 min to 34 degrees C). There were no significant physiologic effects. We conclude that peritoneal instillation of cold Ringer's solution is more rapidly effective than other non-intravascular cooling methods reported previously. Peritoneal cooling should be tried in patients during CPR.

Epinephrine and sodium bicarbonate during CPR following asphyxial cardiac arrest in rats

Although high-dose epinephrine during CPR improves coronary perfusion pressure (CoPP) and rate of return of spontaneous circulation (ROSC) in some models, its impact on long term outcome (> or = 72 h) has not been evaluated. Previous studies of sodium bicarbonate (NaHCO3) therapy during CPR indicate that beneficial effects may be dependent on epinephrine (EPI) dose. We hypothesized that EPI and NaHCO3 given during CPR have a significant impact on long term outcome. One hundred male Sprague-Dawley rats were prospectively studied in a block randomized placebo controlled trial. Rats were anesthetized, paralyzed, mechanically ventilated, instrumented, and each underwent 10 min of asphyxia, resulting in 6.8 +/- 0.4 min of circulatory arrest. Resuscitation was performed by mechanical ventilation and manual external chest compressions. EPI 0.0 (placebo), 0.01, 0.1, or 1.0 mg/kg IV was given at the onset of CPR, followed by NaHCO3 0.0 (placebo) or 1.0 mEq/kg IV. Successfully resuscitated rats were monitored and ventilated for 1 h without hemodynamic support. Neurologic deficit scores (NDS), cerebral histopathologic damage scores (CHDS) and myocardial histopathologic damage scores (MHDS) were determined in rats that survived 72 h. EPI improved CoPP and ROSC in a dose-dependent manner up to 0.1 mg/kg. Rats receiving EPI 0.1 and 1.0 mg/kg during CPR exhibited prolonged post-ROSC hypertension and metabolic acidemia, increased A-a O2 gradient, and an increased incidence of post-ROSC ventricular tachycardia or fibrillation. Overall survival was lower with EPI 0.1 and 1.0 mg/kg compared to 0.01 mg/kg. Although NDS was significantly less with EPI 0.1 mg/kg compared to placebo, there was no difference in CHDS between groups. In contrast, MDS was significantly higher with EPI 0.1 mg/kg compared to placebo or EPI 0.01 mg/kg. There was an overall trend toward improved survival at 72 h in rats that received NaHCO3 which was most evident in the EPI 0.1 mg/kg group. We conclude that (1) EPI during CPR has a biphasic dose/response curve in terms of survival, when post-resuscitation effects are left untreated and (2) NaHCO3 doses greater than 1.0 mEq/kg may be necessary to treat the side-effects of high-dose EPI. Further work is needed to determine if treating the immediate post-resuscitation effects of high-dose EPI can prevent detrimental effects on long-term outcome.

Leflunomide controls rejection in hamster to rat cardiac xenografts

Leflunomide is an isoxazole derivative that has the ability to prevent acute rejection of cardiac, renal, and skin transplants in strongly rejecting rat models. Furthermore, leflunomide is able to interact synergistically with CsA to inhibit allograft rejection and also reverse ongoing allograft rejection. In vitro studies suggest that the mechanism of action of leflunomide is via an interruption of cytokine signaling in T cells. This study defines the ability of leflunomide to prevent and reverse rejection of concordant xenografts. One hundred nine adult Lewis rats in 13 groups received abdominal heterotopic cardiac transplants from Golden Syrian hamsters. The xenograft survived 3.9 +/-0.3 days without treatment. When leflunomide was given at 2.5, 5, 10, 15, or 20 mg/kg by gavage daily, the cardiac xenograft survivals were 5.0 +/- 0.6, 8.0 +/- 3.0, 52.0 +/- 20.2, 76.5 +/- 21.14, and 58.9 +/- 28.1 days, respectively. The survival rates were 4.0 +/- 0 and 27.7 +/- 28.7 days when CsA was given at 10 and 20 mg/kg i.m., respectively. The combination of CsA at 10 mg/kg with leflunomide at 10 mg/kg or 5 mg/kg prolonged cardiac xenograft survival to 106.0 +/- 50.2 days and > 90 days, respectively. There were no observable side effects in the latter combination. Histologic studies of untreated graft hearts 4 days after transplantation revealed infarction of myocardium and severe RBC extravasation. In contrast, the rejected hamster hearts from long-term survivors showed massive mononuclear cell infiltration and myocardium fibrosis in contrast to the early rejected picture. Therapy with leflunomide begun on day 2 reversed these rejection responses by day 6. In addition, the increase in allospecific IgM titers observed on day 2 was reversed, and the allospecific IgM to IgG isotype switch that occurred in untreated animals was prevented by leflunomide. These observations demonstrate that leflunomide, at nontoxic doses, effectively controlled acute rejection of concordant xenografts and synergistic immunosuppressive effect was achieved with leflunomide and CsA.