A mouse model provides evidence that genetic background modulates anemia and liver injury in erythropoietic protoporphyria

Erythropoietic protoporphyria is an inherited disorder of heme biosynthesis caused by partial ferrochelatase deficiency, resulting in protoporphyrin (PP) overproduction by erythrocytes. In humans, it is responsible for painful skin photosensitivity and, occasionally, liver failure due to accumulation of PP in the liver. The ferrochelatase deficiency mouse mutation is the best animal model available for human erythropoietic protoporphyria. The original description, based on mice with a BALB/cByJCrl genetic background, reported a disease resembling the severe form of the human disease, with anemia, jaundice, and liver failure. Using congenic strains, we investigated the effect of genetic background on the severity of the phenotype. Compared with BALB/cByJCrl, C57BL/6JCrl mice developed moderate but increasing anemia and intense liver accumulation of PP with severe hepatocyte damage and loss. Bile excretory function was not affected, and bilirubin remained low. Despite the highest PP concentration in erythrocytes, anemia was mild and there were few PP deposits in the liver in SJL/JOrlCrl homozygotes. Discriminant analysis using six hematologic and biochemical parameters showed that homozygotes of the three genetic backgrounds could be clustered in three well-separated groups. These three congenic strains provide strong evidence for independent genetic control of bone marrow contribution of PP overproduction to development of liver disease and biliary PP excretion. They provide a tool to investigate the physiological mechanisms involved in these phenotypic differences and to identify modifying genes.

Evaluation of the increase in model for end-stage liver disease (DeltaMELD) score over time as a prognostic predictor in patients with advanced cirrhosis: risk factor analysis and comparison with initial MELD and Child-Turcotte-Pugh score

BACKGROUND/AIMS

The model for end-stage liver disease (MELD) has been used to prioritize cirrhotic patients awaiting liver transplantation. The change in MELD score over time (DeltaMELD) may have additional prognostic value. We investigated the ability of DeltaMELD to predict the outcome of advanced cirrhosis and prospectively assessed the factors associated with increasing DeltaMELD.

METHODS

Risk factors were determined in 58 prospectively followed-up patients. The predictive power of DeltaMELD, initial MELD and Child-Turcotte-Pugh (CTP) score was compared by using c-statistic in 351 patients.

RESULTS

Ascites (P=0.020) and hepatic encephalopathy (P=0.023) were significantly associated with increasing MELD score at 3 months. The area under receiver operating characteristic (ROC) curve for DeltaMELD/month was 0.779 compared with 0.718 for MELD (P=0.130) and 0.528 for CTP score (P<0.001) at 6 months; the area was 0.822, 0.744 and 0.528, respectively (P=0.018 and <0.001, respectively) at 12 months. DeltaMELD/month >2.5 was the only significant prognostic predictor at 6 (odds ratio: 9.8, P<0.001) and 12 months (odds ratio: 16.3, P<0.001) in multivariate logistic analysis.

CONCLUSIONS

Increasing MELD score is associated with the onset of ascites and encephalopathy. DeltaMELD is superior to initial MELD and CTP scores to predict intermediate term outcome in patients with advanced cirrhosis.

Analyses of prognostic indices of chronic liver failure caused by hepatitis virus

AIM: To analyze the related indices about the prognoses of chronic liver failure caused by hepatitis virus.

METHODS: Retrospectively reviewed 320 cases of chronic liver failure caused by hepatitis viruses. An improved group and an ineffective group (IG) were made to compare and analyze their clinical manifestations, laboratory examination indices and complications. Logistic regression was also carried out.

RESULTS: There were significant differences (P<0.05) between the improved group and the IG upon such indices as age, bilirubin, prothrombin time, albumin, alpha fetoprotein, the size of liver and complications (P<0.05). The regression formula was as follows: P = 1/(1+e^-y) (y = 1.7262-0.0948X₁+2.9846X₂+0.6992X₃+1.6019X₄+ 2.0398X₅). (Note: X₁-Prothrombin activity; X₂-digestive tract hemorrhage; X₃-hepatic encephalopathy; X₄-hepatorenal syndrome; X₅-pulmonary infection.).

CONCLUSION: Laboratory examination such as bilirubin, prothrombin time and alpha fetoprotein can be regarded as indices of the prognoses of chronic liver failure caused by hepatitis. Moreover, the regression equation can evaluate prognoses more comprehensively and direct our treatments.

[Gasometric alterations in hospitalized cirrhotic patients]

BACKGROUND AND OBJECTIVES

Gas exchange alterations have been described in cirrhotic patients; but by the moment, a few prospective studies have focused in them. The aim of this study was to describe the frequency and severity of gasometric alterations in hospitalized cirrhotic patients, a their correlation with hepatocellular disfunction.

PATIENTS AND METHODS

50 consecutive cirrhotic patients (41 males) admitted for liver decompensation (ascites, liver encephalopathy, alcoholic hepatitis and upper gastrointestinal bleeding) without acute or chronic cardiopulmonary disfunction were included in the study. Patients were classified according with Child-Pugh score (A, n = 13; B, n = 21; C, n = 16). Severe alcoholic hepatitis (SAH) was confirmed in 7 patients. Arterial gasometry was performed in all patients before discharge. Contrast echocardiography was performed in any case of suspicion of hepatopulmonary syndrome (HPS).

RESULTS

Light hypoxemia was observed (80.9 mmHg), without differences with Child-Pugh. Hypocapnia was significantly more evident in Child C than in A and B (31.2 +/- 3.1 vs. 38.1 +/- 4.3 y 36.3 +/- 5 mmHg; p < 0,05), respectively. Cirrhotic patients with SAH showed a significantly higher hypocapnia by comparison with others (31.2 +/- 3.1 vs. a 36.3+/-5 mmHg; p < 0.05). In multivariate analysis, independent prognostic variables for hypocapnica were plasmatic levels of protrombin time, albumin and sodium. HPS was confirmed in 8 patients (16%).

CONCLUSIONS

The most prevalent gas exchange abnormality in cirrhosis was the alteration of alveolar-arterial oxygen tension gradient, directly correlated with hepatocellur disfunction. Hypocapnia could be a compensatory mechanism or the result of the activation of central respiratory centres by non-depurated substances by the liver.

Sexual dimorphism in endotoxin susceptibility after partial hepatectomy in rats

BACKGROUND/AIMS

Liver failure due to endotoxemia after hepatectomy is a fatal complication. Little is known regarding the gender influence on this pathophysiological condition. This study was conducted to investigate whether a gender difference exists in the endotoxin susceptibility after hepatectomy.

METHODS

Sexually mature male and female rats received an intravenous administration of lipopolysaccharide (LPS), as endotoxin, 48h after a two-thirds hepatectomy.

RESULTS

The 24-h survival rate after LPS administration was significantly higher in females (75%) than in males (38%). Ovariectomy reduced the survival rate in females to 44%. Plasma tumor necrosis factor-alpha levels 1h after LPS were significantly elevated in males and ovariectomized females. The inducible nitric oxide synthase (iNOS) gene expression in liver and spleen, and consequent nitric oxide production 3h after LPS were significantly enhanced in males and ovariectomized females when compared to females, in addition to less functional and structural liver damage in females.

CONCLUSIONS

Our results indicate a gender difference in the susceptibility to endotoxemia in the early phase after hepatectomy. Female tolerance to these conditions may be mediated by an inhibition of excessive inflammatory response in the liver and the spleen, partially via the suppression of iNOS gene up-regulation.

Influence of heme-based solutions on stress protein expression and organ failure after hemorrhagic shock

OBJECTIVE

Hemoglobin-based oxygen carriers (e.g., diaspirin-cross-linked hemoglobin [DCLHb] and hemoglobin glutamer-200 [HbG]) may have potential in the treatment of hemorrhagic shock. The nitric oxide scavenging and direct vasoconstrictive side effects of free hemoglobin of currently available preparations may increase organ injury after shock in contrast to non-oxygen-carrying heme solutions (e.g., hemin arginate [HAR]). However, both classes of substances might induce the protective enzyme heme oxygenase (HO)-1, particularly in the liver. The aim of the study was to assess the role of pretreatment with DCLHb, HbG, or HAR on HO-1 expression and organ injury after hemorrhagic shock.

DESIGN

Prospective controlled laboratory study.

SETTING

Animal research laboratory at a university hospital.

SUBJECTS

Male Sprague-Dawley rats (200-300 g body weight, n = 5-12/group).

INTERVENTIONS

Twenty-four hours after different doses of DCLHb, HbG (each 1, 2, or 3 g/kg of body weight), or HAR (5, 25, or 75 mg/kg of body weight), the protein expression of HO-1 and heat shock protein-70 in liver, kidney, heart, lungs, and aorta was determined. Twenty-four hours after pretreatment with DCLHb, HbG, or HAR, rats were subjected to hemorrhage (mean arterial blood pressure, 35-40 mm Hg for 1 or 2 hrs)/resuscitation (5 or 4 hrs, respectively). Animals treated with Ringer's solution (30 mL/kg of body weight) served as controls. In additional experiments, HO activity was blocked with tin mesoporphyrin-IX.

MEASUREMENTS AND MAIN RESULTS

DCLHb, HbG, and HAR dose-dependently induced HO-1 protein but not heat shock protein-70. Pretreatment with DCLHb or HbG shortened the onset of decompensation in shock (DCLHb, 40 +/- 11 mins; HbG, 36 +/- 4 mins) compared with vehicle (68 +/- 4 mins, p < .05) and HAR pretreatment (81 +/- 7 mins, p < .05). High doses of DCLHb pretreatment increased mortality (2 hrs of shock, 80%; p < .05 vs. vehicle or HAR). Pretreatment with HAR led to higher shed blood volumes (p < .05) and higher hepatocellular ATP levels (2 hrs of shock, p < .05 vs. DCLHb and HbG). Blockade of HO activity by tin mesoporphyrin-IX abolished the protection mediated by HAR.

CONCLUSIONS

Although DCLHb, HbG, and HAR induce HO-1 in the absence of an unspecific stress response, only HAR pretreatment protects against shock-induced organ failure. Although the underlying mechanisms of positive HAR priming are not completely understood, the induction of HO-1 expression and the lack of nitric oxide scavenging through HAR may play an important role.

Liver fibrosis

Liver fibrosis is the excessive accumulation of extracellular matrix proteins including collagen that occurs in most types of chronic liver diseases. Advanced liver fibrosis results in cirrhosis, liver failure, and portal hypertension and often requires liver transplantation. Our knowledge of the cellular and molecular mechanisms of liver fibrosis has greatly advanced. Activated hepatic stellate cells, portal fibroblasts, and myofibroblasts of bone marrow origin have been identified as major collagen-producing cells in the injured liver. These cells are activated by fibrogenic cytokines such as TGF-beta1, angiotensin II, and leptin. Reversibility of advanced liver fibrosis in patients has been recently documented, which has stimulated researchers to develop antifibrotic drugs. Emerging antifibrotic therapies are aimed at inhibiting the accumulation of fibrogenic cells and/or preventing the deposition of extracellular matrix proteins. Although many therapeutic interventions are effective in experimental models of liver fibrosis, their efficacy and safety in humans is unknown. This review summarizes recent progress in the study of the pathogenesis and diagnosis of liver fibrosis and discusses current antifibrotic strategies.

The MELD score may help to determine optimum time for liver transplantation

BACKGROUND

The model for end-stage liver disease (MELD) score is a good predictor of mortality on the waiting list and short-term survival post liver transplantation.

AIM

Our aim was to determine if there is a pretransplant MELD score beyond which liver transplantation is prohibitive.

PATIENTS AND METHODS

Forty-six adult patients underwent primary liver transplantation from January 1996 to December 2002. Patients followed to the most recent visit or death underwent survival analysis using Cox regression and Kaplan Meier methods.

RESULTS

There was a significant correlation between the pretransplant MELD score and survival at 6 months posttransplant (P=.037 95% CI: 1.004-1.13). Patients with pretransplant MELD score greater than or equal to 32 showed significantly greater mortality compared with those less than 32 (HR 9.18, 95%CI=1.16-72.44).

CONCLUSION

Pretransplant MELD may help to determine the optimum time for liver transplantation.

Effects of liver transplantation on the nutritional status of patients with cystic fibrosis*

The long-term effects of liver transplantation on nutritional status, body composition and pulmonary function in patients with liver disease associated with cystic fibrosis (CF) are poorly defined. We studied 15 patients with CF-associated biliary cirrhosis and severe portal hypertension. Seven underwent liver transplantation (age: 14.8 +/- 6.2 years), and eight were treated conservatively (age: 15.9 +/- 6.7 years). All patients were evaluated at baseline and thereafter yearly for a median duration of 5 years. During follow-up, transplanted patients gained weight and showed a significant increment in body mass index (P < 0.004), whereas patients without transplantation remained stable (P = 0.063). Baseline bone mineral content (dual energy X-ray absorptiometry scan) was lower than normal in all patients (more in transplanted patients) and increased in transplanted patients (P < 0.05), but not in patients without transplantation. In both groups percent body fat did not change, whereas fat free mass increased only in the transplant group (P = 0.06) (P < 0.03 versus nontransplanted patients). Only in transplanted patients' plasma concentrations of vitamin E and A increased (P < 0.05 versus nontransplanted patients). Forced espiratory volume in 1 s and forced vital capacity showed similar deterioration in transplanted and in nontransplanted patients. Liver transplantation is associated with long-term beneficial effects on the nutritional status of CF patients and seems to favor bone mineralization.

Anesthesia for liver transplant surgery

Liver transplantation offers patients with liver disease an optimal chance for long-term survival. Current indications, preoperative assessment, patient selection, intraoperative anesthetic management and outcomes are described. The management of special situations, including retransplantation, pediatric transplantation, and fulminant hepatic failure are also reviewed. The success of liver transplantation has led to increased demand. This demand, coupled with a nonexpanding supply of deceased donor organs, has resulted in a shortage of grafts and prolonged waiting times. Novel solutions using segmental liver grafts from living donors, and the challenges associated with this approach, are discussed.

Serum sodium predicts mortality in patients listed for liver transplantation

With the implementation of the model for end-stage liver disease (MELD), refractory ascites, a known predictor of mortality in cirrhosis, was removed as a criterion for liver allocation. Because ascites is associated with low serum sodium, we evaluated serum sodium as an independent predictor of mortality in patients with cirrhosis who were listed for liver transplantation and whether the addition of serum sodium to MELD was superior to MELD alone. This is a single-center retrospective cohort of all adult patients with cirrhosis listed for transplantation from February 27, 2002, to December 26, 2003. Listing laboratories were those nearest the listing date +/-2 months. Of the 513 patients meeting inclusion criteria, 341 were still listed, while 172 were removed from the list (105 for transplantation, 56 for death, 11 for other reasons). The median serum sodium and MELD scores were 137 mEq/L (range, 110-155) and 15 (range, 6-51), respectively, at listing. Median follow-up was 201 (range, 1-662) days. The risk of death with serum sodium <126 mEq/L at listing or while listed was increased, with hazard ratios of 7.8 (P < .001) and 6.3 (P < .001), respectively, and the association was independent of MELD. The c-statistics of receiver operating characteristic curves for predicting mortality at 3 months based upon listing MELD with and without listing serum sodium were 0.883 and 0.897, respectively, and at 6 months were 0.871 and 0.905, respectively. In conclusion, serum sodium <126 mEq/L at listing or while listed for transplantation is a strong independent predictor of mortality. Addition of serum sodium to MELD increases the ability to predict 3- and 6-month mortality in patients with cirrhosis.

Value of albumin dialysis therapy in severe liver insufficiency

A blood purification system, molecular adsorbents re-circulating system (MARS), is based on the removal of both protein-bound and water-soluble substances and toxins in the liver. We treated a total of 88 patients within 2 years. Of these patients, 45 had acute liver failure (ALF), 31 had acute decompensation of chronic liver disease, eight had graft failure and four had miscellaneous conditions. Of the patients with ALF, 80% survived; in 23 patients their own liver recovered and 13 patients underwent successful transplantation. Only 23% of patients with acute-on-chronic liver failure survived. Most of them were not considered for transplantation due to their having liver failure from alcoholism and from not abstaining from drinking. MARS is a promising therapy for ALF, allowing the patient's own liver to recover or allowing enough time to find a liver graft. Best results were achieved in patients who had been intoxicated with a lethal dose of toxin. On the other hand, we did not observe much benefit in patients with severe acute-on-chronic liver failure (AcoChr) who did not undergo liver transplantation.

Binding of bilirubin and bromosulphthalein to albumin: implications for understanding the pathophysiology of liver failure and its management

The binding/transporting functions of albumin provide the rationale for using albumin dialysis (e.g., molecular adsorbents recirculating system [MARS]) in liver failure. This study investigates these properties in vitro, validating the findings in vivo. In vitro bromosulphthalein (BSP) and bilirubin-spiked plasma were dialyzed against albumin and sampled. In vivo serum biochemistry was analyzed in: 7 MARS-treated liver failure patients; 98 MARS-treated patients from the MARS Registry; and 8 patients receiving albumin infusion. In vitro BSP concentrations did not equilibrate, but the molar ratio of BSP to albumin (C(BSP)/C(alb)) did, with no subsequent transmembrane transport, suggesting that the C(BSP)/C(alb) gradient (rather than simple diffusion) drives BSP transport. Bilirubin was transported similarly. In vivo serum bilirubin reduction during MARS sessions (n = 26) correlated with pre-treatment bilirubin (r = 0.42), but better (r = 0.85) with pre-treatment molar ratio of bilirubin to albumin (C(bilirubin)/C(alb)). The strongest correlation was between C(bilirubin)/C(alb) reduction and pre-treatment C(bilirubin)/C(alb) (r = 0.9). A similar pattern was observed in the MARS Registry patients. After albumin infusion (n = 8), both serum albumin and bilirubin increased, while C(bilirubin)/C(alb) remained unchanged. C(bilirubin)/C(alb) appears to be important in albumin dialysis, and generally in liver disease patients, reinforcing the importance of the toxin-binding functions of albumin in liver disease.

Dynamic movement of cytochrome c from mitochondria into cytosol and peripheral circulation in massive hepatic cell injury

BACKGROUND

In the process of apoptosis, it is known that the transition of cytochrome c from mitochondria into the cytosol occurs, and tumor necrosis factor (TNF)-alpha is one of the molecules responsible for this event. But in the state of hypercytokine induced by D-galactosamine (D-GaIN)/Lipopolysaccharide (LPS), the localization of cytochrome c is little known.

METHODS

Rats were administrated with D-GaIN(700 mg/kg)/LPS(200 microg/kg). Blood and tissue samples were collected and examined for levels of pro-inflammatory cytokines, the apoptosis of liver cells, and the localization of cytochrome c.

RESULT

Before administration of D-GaIN/LPS, cytochrome c was definitely localized in the mitochondria. At 2 h after simultaneous administration of D-GaIN/LPS, cytochrome c had accumulated in the cytosol following abrupt increases of plasma TNF-alpha. Massive cell destruction due to apoptosis proved by Terminal deoxynucleo-tidyl transferase-mediated dUTP nick end labeling staining was observed in liver tissue 4 h later and markedly increased levels of cytochrome c were detected in the plasma 12 h after D-GaIN/LPS administration.

CONCLUSION

Liver injury induced by simultaneous administration of D-GaIN/LPS was closely associated with the production of TNF-alpha, and also with the dynamic movement of cytochrome c from the mitochondria into the cytosol, and then into the systemic circulation. The detection of plasma cytochrome c levels may be a useful clinical tool for the detection of apoptosis in vivo.

Organ allocation for liver-intestine candidates

1. Patients listed for combined liver and intestine transplantation have the highest waitlist mortality of any transplant candidates. 2. Liver-intestine candidates have higher mortality rates than other patients listed for liver transplantation at all model for end-stage liver disease (MELD) and pediatric end-stage liver disease (PELD) scores, sepsis rather than liver failure being the major cause of death in this group. 3. Increasing PELD scores appear to correlate with increasing waitlist mortality in patients awaiting combined liver and intestinal transplantation. 4. Present policy to increase MELD / PELD scores for liver-intestine patients by an additional estimated 10% mortality risk is an attempt to bridge the difference in waitlist mortality while maintaining the principle of allocating organs on the basis of disease severity. 5. Scheduled reevaluation of present allocation practices is essential to refine Organ Procurement and Transplantation Network United Network for Organ Sharing policy as it relates to patients in need of combined liver and intestinal transplantation.

How will patients be selected for transplantation in the future?

1. The model for end-stage liver disease has become a selection tool for recipients for liver transplantation. 2. The present selection / allocation system does not recognize distinctions in "donor organ quality." 3. Many studies have shown that donor factors such as age, gender, fat content, and heart beating versus non-heart beating status influence outcome of the liver transplantation. 4. Efforts to increase organ donation are likely to provide more "expanded-criteria donors." 5. Future selection practices may attempt to match specific recipients to specific donors.

When is a patient too well and when is a patient too sick for a liver transplant?

1. Liver transplantation is currently offered as a therapeutic option for patients with a wide range of end-stage liver diseases. 2. Conventional wisdom suggests that patients who receive a liver transplant have a greater expected lifetime when compared to comparable candidates on the waiting list. 3. The model for end-stage liver disease (MELD) scoring system is an excellent predictor of mortality on the waiting list and also predicts mortality after liver transplantation. 4. The combination of waiting list mortality risk and posttransplant mortality risk assessed by MELD and other factors can be used to estimate whether candidates are likely to derive a survival benefit from a liver transplant.

Anti-inflammatory effects of hepatocyte growth factor: induction of interleukin-1 receptor antagonist

Hepatocyte growth factor (HGF) prevents liver failure in various animal models including endotoxin-induced acute liver failure. We were interested to find out whether human HGF exerts anti-inflammatory effects by modulation of cytokine synthesis. Therefore, human HepG2 cells were cultured with increasing concentrations of HGF. HGF dose-dependently upregulated the production of interleukin-1 receptor antagonist (IL-1Ra). Incubation of HepG2 cells with interleukin-1beta (IL-1beta) caused an increase in IL-1Ra levels, while interleukin-6 (IL-6) had no effect on IL-1Ra synthesis. Co-stimulation of HepG2 cells with HGF + IL-1beta resulted in a synergistic effect on IL-1Ra mRNA and protein expression. Stimulation of freshly isolated mouse hepatocytes from male C57 BL/6 mice with HGF increased IL-1Ra mRNA and protein synthesis dose-dependently. A co-stimulation with HGF and IL-1beta had a synergistic effect on IL-1Ra mRNA expression but only a partially additive effect on IL-1Ra protein synthesis. HGF-induced IL-1Ra production was significantly decreased by the mitogen-activated protein kinase (MAPK) inhibitor PD98059. Accordingly, HGF stimulation specifically increased MAPK-dependent signalling pathway (p42/44). In contrast, in preactivated PBMC mRNA expression and protein synthesis of IL-1Ra, interleukin-10 (IL-10) and tumor necrosis factor-alpha (TNF-alpha) were unaffected after stimulation with HGF. In conclusion, our data suggest that HGF exerts anti-inflammatory effects by modulating the signal transduction cascade leading to increased expression of IL-1Ra, which might explain the protective and regenerative properties of this cytokine in animal models of liver failure.

Hepatopulmonary syndrome and portopulmonary hypertension in the model for end-stage liver disease (MELD) era

1. How do physicians decide which patients with pulmonary vascular disease will benefit from liver transplantation? 2. Studies on patients with pulmonary vascular disease are limited and the findings and recommendations may not apply to all practice sites. 3. All patients with hypoxemia, liver disease, and pulmonary vasodilation do not have hepatopulmonary syndrome (HPS). 4. Not all patients with hepatopulmonary syndrome will benefit from liver transplantation. 5. The mean pulmonary artery pressure (mPAP) may not be an accurate predictor of mortality in patients with portopulmonary hypertension. 6. The effects of pulmonary vasodilators on the outcome of patients with portopulmonary hypertension (PPHTN) is still unconfirmed but promising.

Retransplantation for recurrent hepatitis C in the MELD era: maximizing utility

1. Retransplantation (re-LT) for hepatitis C virus (HCV) recurrence is controversial. Although re-LT accounts for 10% of all liver transplants (LTs), the number of patients requiring re-LT is expected to grow as primary LT recipients survive long enough to develop graft failure from recurrent disease. 2. Utility, as applied to the medical ethics of transplantation, refers to allocating organs to those individuals who will make the best use of them. The utility function (U) of liver transplantation is represented by the product of outcome (O = 1-year survival with LT) times emergency (E = 3-month mortality without LT), i.e., U = O x E. 3. For primary LT, maximal U is achieved by allocating organs at the highest model for end-stage liver disease (MELD) score (i.e., "sickest first"). No significant differences exist between HCV and non-HCV diagnoses. 4. For re-LT, maximal utility for HCV and non-HCV diagnoses are achieved at MELD scores of 21 and 24, respectively. Utility starts to decline at MELD scores above 28. 5. The current allocation system (MELD) fails to maximize utility with regard to re-LT.