Bridge therapy in hepatocellular carcinoma before liver transplantation: the experience of two Chilean centers

BACKGROUND

Orthotopic liver transplantation (OLT) is currently an established therapy for small, early-stage hepatocellular carcinoma (HCC) within the Milan criteria. Long waiting times due to the shortage of donor organs can result in tumor progression and drop-out from OLT candidacy. Therefore a wide variety of procedures are necessary before OLT. The aim of this retrospective study was to review our experience in relation to bridge therapy prior to OLT for HCC.

METHODS

This was a retrospective database review of all of the patient who underwent transplantation in our institutions between January 1993 and June 2009. We analyzed patients with a diagnosis of HCC in the explant.

RESULTS

Among 29 patients, including 12 who were diagnosed by the explant and 17 prior to transplantation, 88% underwent bridge therapy during a mean waiting time to OLT of 12 months. Among the 23 procedures, namely 1.5 procedures per patient, included most frequently chemoembolization (48%), alcohol ablation (30%), radiofrequency ablation (13%), and surgery (9%). Thirty-three percent of the explants contained lesions within the Milan criteria. In our series the 5-year survival rate for patients transplanted for HCC was 86%; in the bridge therapy group, it was 73%.

CONCLUSIONS

The incidence of patients who underwent bridge therapy (52%) was similar to other reported experiences, but the fulfillment of Milan criteria in the explants was lower. Among the bridge therapy group, the survival was slightly lower, probably because this group displayed more advanced disease.

GM-CSF neutralisation suppresses inflammation and protects cartilage in acute streptococcal cell wall arthritis of mice

OBJECTIVE

The pathogenic involvement of granulocyte-macrophage colony-stimulating factor (GM-CSF) in arthritis has been put forward. We have investigated the therapeutic effect of GM-CSF neutralisation in the streptococcal cell wall (SCW) arthritis model in mice. In this model, the pathogenic contribution of tumour necrosis factor (TNF)alpha is minor and is expressed only on joint swelling, whereas cartilage proteoglycan depletion is independent of this cytokine.

METHODS

Acute monarthritis was induced by injection of SCW bacterial extracts to mouse knees. Treatments (mAb 22E9 at 300, 100, 30 microg; or Enbrel 300 microg) were given twice intraperitoneally 2 h before and 3 days after disease induction. Swelling was assessed by (99m)Tc uptake into knees on days 1 and 2. Local cytokine levels were determined in patellae washouts on day one. Proteoglycan loss from cartilage was scored on histological sections at termination on day four.

RESULTS

Treatment with anti-GM-CSF mAb 22E9 showed a dose-related efficacy by decreasing swelling that was significant at the 300 and 100 microg doses in comparison to isotype control, and comparable to dexamethasone (5 mg/ml). Proteoglycan loss from cartilage was also significantly reduced by mAb 22E9 300 microg (p=0.001). This reduced proteoglycan loss observed after GM-CSF neutralisation was not seen after TNFalpha-blockade with Enbrel. Similarly, levels of interleukin 1beta in joints were reduced after treatment with 22E9 mAb (p=0.003) but not in mice receiving Enbrel.

CONCLUSIONS

Our findings show a pathogenic role for GM-CSF in this arthritis model, support the therapeutic potential of neutralising this cytokine, and may indicate therapeutic activity of an anti-GM-CSF mAb in TNFalpha-independent disease situations.

Early Posttransplant Lymphoproliferative Disease in Pediatric Liver Transplant Recipients

Among 23 pediatric patients who underwent orthotopic liver transplant (OLT), we report two (11 and 26 months old) with posttransplant lymphoproliferative disease (PTLD) that occurred in the early posttransplantation period. They were Epstein-Barr Virus (EBV)-negative and received graft from EBV-positive donors. The surveillance for EBV viremia using serial EBV polymerase chain reaction determinations in the peripheral blood was positive at 10 and 90 days after OLT concomitant with symptoms of primary infection, both patients were treated with gancyclovir. The patients should progression to a Burkitt's and a non-Hodgkin's lymphoma that appeared 3 months posttransplantation. They were treated by withdrawal of immunosuppression and six courses of cyclophosphamide as well as anti-CD20 monoclonal antibody (Rituximab) every 21 days. One patient experienced acute graft rejection, which resolved with steroids and low doses of tacrolimus, she is free of disease at 24 months after the end of treatment. The other patient relapsed with a cerebral lymphoma, receiving aggressive chemotherapy, but died due to sepsis. In conclusion, PTLD occurred among in 2/23 patients who underwent OLT and appeared in the first quarter post OLT. The risk factors associated with early PTLD were primary EBV infection after OLT, young age, and EBV-negative recipient receiving a transplant from an EBV-positive donor. Antiviral treatment alone was inefficient; withdrawal of immunosuppression and courses of Rituximab and cyclophosphamide were well tolerated and controlled PTLD. The risk of graft rejection was increased by withdrawal of immunosuppression. One patient died.

Rapid steroid taper and neoral monotherapy in liver transplantation in Chile: a step in the right direction?

Diabetes, hypercholesterolemia, hypertension, obesity, osteopenia, and increased risk of viral recurrence are among the complications associated with posttransplant steroid use. Steroid withdrawal or rapid taper has been reported to be safe. The aim of this study was to compare the rejection incidence and severity among patients treated with two different steroid taper strategies.

METHODS

This retrospective study included all the adult liver transplant recipients since the program's inception from 1993 to January 2002. The minimum follow-up was 1 year. Exclusions included patients receiving an immunosupressive regimen other than mycophenolate mofetil, steroids, and Neoral, or suffering an autoimmune etiology, or displaying patient or graft survival less than 1 year. The incidence and severity of rejection episodes were compared between the two groups of steroid taper protocols: group A received methylprednisolone (1 g) intraoperatively with a slow taper to 10 mg prednisone per day at 1 year. Group B received methylprednisolone (2 g) intraoperatively followed by a rapid reduction with intention to withdraw by month 4, continuing on Neoral monotherapy. Rejection diagnosis was made on histological bases.

RESULTS

One-month and 1-year rejection rates were 47% and 53%, respectively, among the rapid taper group with Neoral monotherapy, which was similar to 60% and 64%, respectively, in the slow taper group. Rejection severity was also comparable between the two groups.

CONCLUSIONS

Patients treated with a rapid steroid taper protocol followed by Neoral monotherapy or a slow taper protocol showed similar acute rejection incidences and severities. Their survival rates were also comparable. Further study is necessary to evaluate the impact of rapid steroid taper to prevent the complications of steroid use.

Liver transplantation in Latin America: current status

The current status of liver transplantation in Latin America is reviewed. For an estimated population of 470 million people, approximately 1100 liver transplantations were performed in 2002, namely, 2.3 liver transplantations per million people per year (pmp). The top transplantation rates were in Argentina 4.5, Brazil 3.9, and Chile 3.6 pmp. In 2001, liver transplantations were not performed in 2 of 10 South American countries nor were liver transplantations performed in 5 of 6 Central American countries. In the Latin American countries performing this procedure, living donor liver transplantation has been performed to palliate the organ shortage for pediatric patients in most of these countries. However, only 3 countries have used the procedure for adult liver transplantation. The lack of adequate financial coverage, education, and organization are the main limiting factors to the development of liver transplantation in Latin America.

Predictive models in cirrhosis: correlation with the final results and costs of liver transplantation in Chile

Medical scores for predicting survival are essential to stratify patients with end-stage liver disease (ESLD) for prioritization for liver transplantation (OLT). Recently the UNOS has adopted the Mayo Model for End-stage Liver Disease (MELD) score as the basis for liver allocation in the United States. We retrospectively evaluated and assessed the prognostic impact, the length of stay (LOS), and hospital charges for OLT using two severity scores (Child-Turcotte-Pugh [CTP] versus MELD) to stratify cirrhotic patients before OLT. Twenty-six consecutive adult cirrhotic patients (11 women, mean age 46 years) underwent LT between 2000 and 2002. The main causes for transplantation were alcohol and primary biliary cirrhosis. The mean CTP and MELD scores at the moment of listing for OLT were 8.9 and 16.3 points, respectively. The best discriminative values with prognostic impact in terms of outcome and costs of OLT were a Child Pugh score >/=11 points or a MELD score >/=20 points. Patients in these strata showed a significant increase in LOS in the hospital (from a mean of 12 to 22 days) and intensive care stay (from a mean of 4 to 14 days) post-OLT when compared with patients with a lower CTP or MELD score (P <.05). There was also a trend toward higher hospital charges (P =.06). Organ allocation by MELD score will probably adversely affect the LOS and hospital charges of patients being transplanted due to ESLD.

A decade of adult liver transplantation in a single center in Chile

INTRODUCTION

Since the early days, liver transplantation (OLT) has conquered several barriers worldwide to become a proven therapy. We assessed the evolution of our adult liver transplant program.

METHODS

We studied all adult patients who underwent OLT since the inception from November 1993 through May 2003. Donor data, recipient pretransplantation evaluation, surgical technique, results, and costs were examined over our evolution, stratifying 3 groups over time, based on the number of adult OLT per year.

RESULTS

Between November 1993 and May 2003, 70 OLT were performed in 64 patients older than 15 years of age. Preoperative Child score, preoperative creatinine level, donor and recipient age, and proportion of emergencies were similar in the 3 groups. Over time, the predominant surgical technique was the piggyback technique (97% of OLT) with a decrease in the use of bypass from 63% to 5% during the last time period. Over the 10 years of our program's existence, warm ischemia time has been reduced to less than 1 hour, whereas cold ischemia time has remained constant at around 5 hours. Biliary and vascular complications decreased over time to around 10%. The mean length of hospital stay (LOS) decreased to 12 days (excluding emergencies). Since inception, our 1-year patient survival rate average is 91%; however, in just the last 3 years of our program (2000 through 2003), the 1-year patient survival rate is 97%.

CONCLUSIONS

In summary, our surgical technique has evolved toward piggyback use without veno-venous bypass with a significant decrease in warm ischemia times. As expected, our results have improved over time and our LOS and costs have decreased. Finally, our current results are similar to the best ones reported in the medical literature today.

Transcystic cholangiogram access via rubber band with early withdrawal after liver transplantation: A safe technique

OBJECTIVE

Since different techniques have been described for cholangiogram access after liver transplantation, we compared two different methods for patients with duct-to-duct biliary anastomoses.

METHODS

Adult liver transplant patients from program inception in 1993 to May 2003 in whom a duct-to-duct biliary anastomosis with a T-tube choledochostomy were compared with those having a transcystic duct catheter using a rubber band. We excluded 10 patients in which a different technique was used or graft or patient survived less than 21 days. Group A (n = 28,) had a number 10 T-tube exteriorized through the recipient main bile duct; and group B (n = 33) a number 5 Bard ureteral stent tied to the cystic stump with reabsorbable suture and secured with a hemorrhoidal rubber ligature.

RESULTS

The biliary complication rate was lower among the transcystic catheter group (9.1%, 3/33) compared to the T-tube group (35.7%, 10/28). Postcatheter withdrawal peritonitis was present in two patients in the T-tube group, one of whom required emergency laparotomy. A satisfactory postoperative cholangiogram was obtained in both groups. The transcystic catheter was withdrawn on average at 29 days, compared to 136 days in the T-tube group.

CONCLUSIONS

Both techniques are equally effective in obtaining a satisfactory postoperative cholangiogram. However, the transcystic catheter technique allows a significantly earlier withdrawal with fewer complications compared to the T-tube technique.

Clinical characterization and survival of adult patients awaiting liver transplantation in Chile

Liver transplantation has become widely used for patients with decompensated disease. Because of the shortage of donors, each year more patients die on the waiting list. Our aim was to characterize and evaluate the final outcomes of all listed candidates for liver transplantation during a 34-month period. We retrospectively evaluated all adults listed between January 2000 and November 2002. Sixty-three patients (37 women, mean age 45.8 years) were listed: 48 due to chronic liver disease and 15 for a highly urgent transplantation due to acute liver failure. The main etiology of chronic disease was alcoholic (22%) or primary biliary cirrhosis (17%). Of 52 chronic patients, 26 (50%) were transplanted with a mean waiting time of 168 days. Among the others, 8 died (15%) while awaiting transplantation, 3 (5%) were removed from the list, and 15 patients still await transplantation (28%). Among acute liver failure patients, the main etiologies were autoimmune (25%) and medication induced (25%). Of 15 acute patients, 6 (37.5%) have been transplanted at a mean waiting time of 6.8 days with 100% survival posttransplantation. In this cohort, 6 patients (37.5%) died while awaiting liver transplantation, and 4 (25%) survived with medical support. In conclusion, the severity of liver disease and death rate among our waiting list was similar to that observed in developed countries. It seems reasonable to review our current allocation system based on waiting time on the list. We will have to decide whether to transplant sicker patients or those with hepatocarcinoma (as in the United States recently with the MELD system), thereby possibly decreasing the mortality rate on the waiting list at the expense of higher costs and more difficult postoperative care or to just keep our current policy.

Trends in mechanical ventilation and immediate extubation after liver transplantation in a single center in Chile

INTRODUCTION

Some groups have reported early extubation post-liver transplantation in patients with previously defined criteria, in an attempt to shorten the ICU stay and decrease costs. We review our experience with trends in mechanical ventilation and resource utilization.

METHODS

We retrospectively reviewed the length of mechanical ventilation, ICU stay, hospital stay, transfusions, and costs of liver transplants performed since the program's inception in 1993 and 2002 including 82 OLT in 71 patients. We also report our experience with immediate postoperative extubation, which we have done from October to December of 2002. We compare different periods: the early days (1993 to 1997), namely, fewer than 10 OLT per year, with the subsequent years assessed individually.

RESULTS

There has been a progressive decrease over time in the length of mechanical ventilation, ICU stay, hospital stay, and costs. Since the program's inception actuarial adult patient 1- and 5-year survival rates were 88.7% and 78%, respectively. The 1-year survival rate increased to 97% during the period of 2000 to 2002 (n = 30). From October to the present, we extubated four of seven adult patients who met criteria with none of them requiring reintubation.

CONCLUSIONS

We demonstrate improved results, decreased length of mechanical ventilation, ICU, and hospital stay, and costs. The immediate postoperative extubation may be feasible for patients who meet previously defined criteria.

IL-2 receptor blockers in liver transplantation: initial experience with daclizumab in Chile

Monoclonal antibodies against the interleukin 2 receptor have been developed in an effort to decrease rejection rates and spare calcineurin inhibitors when renal dysfunction occurs after transplant. While success has been reported in kidney transplantation, its effectiveness in liver transplantation is less clear.

METHODS

This prospective nonrandomized study including adult patients was performed between October 2000 and April 2003. Two groups of immunosuppressive regimens were compared: group A received 2 g of methylprednisolone intraoperatively followed by a rapid reduction with intention to withdraw by month 4, continuing on Neoral monotherapy. Cellcept was also given for 2 months in the absence or for up to 4 months in the presence of rejection. Group B received the same immunosuppressive regimen but, in addition, daclizumab 1 to 1.5 mg/kg on day 1 and day 5 posttransplant. Rejection diagnosis is made on histology basis. Protocol biopsies were performed in all the patients on day 7 and if indicated by biochemistry thereafter.

RESULTS

Both groups were similar in terms of preoperative CHILD score, serum creatinine, incidence of status I, donor and recipient age and ischemia times. The mean follow-up time was 20 months for Group B (n = 24) and 7 months for Group A (n = 10). The 1-month and 1-year rejection rates are 29.1% and 41% in Group A versus 20% and 30% in group B. Rejection severity was similar between both groups. One-year patient and graft survival rates were 96% and 92% in group A and 100% for both in Group B.

CONCLUSIONS

In this series, daclizumab induction therapy seems to display a trend toward a lower rejection rate without increasing infectious complications nor affecting graft survival rates.

[Chronic pancreatitis. A recent national experience with its surgical management]

BACKGROUND

The prevalence of chronic pancreatitis in Chile is not known and there is no local information about the surgical treatment of this disease.

AIM

To review retrospectively the results of surgical treatment of chronic pancreatitis.

MATERIAL AND METHODS

The charts of 17 patients (12 male), aged 7 to 65 years old, with chronic pancreatitis that were operated in three different Chilean regions, were reviewed.

RESULTS

Seven patients had previous endoscopic therapeutic procedures (papillotomy in 4 and stent placing in 3). Seven patients had been subjected to previous biliary surgical procedures. Indications for surgery were severe pain in 14 patients, the suspicion of a pancreatic carcinoma in 4 patients, an infected pseudocyst in one and massive bleeding of multiple pseudo-aneurysms in a pseudocyst in one patient. Twelve patients were subjected to decompressions and 5 to pancreatic resections. There was no operative mortality and one transient pancreatic fistula. After an average follow up of 22 months, pain improved in 94% of cases, pancreatic cancer was diagnosed in one patient and 79% of subjects gained weight. One patient became insulin dependent, one increased his insulin requirements and one had transient steatorrhea, since she could not afford pancreatic enzyme replacement therapy.

CONCLUSIONS

The multidisciplinary approach of patients with chronic pancreatitis, with selective use of surgery, may greatly improve their quality of life.

Affinity labelling of frog brain opioid receptors by dynorphin(1-10) chloromethyl ketone

It has been previously found that chloromethyl ketone derivatives of enkephalins bind irreversibly to the opioid receptors in vitro. Recently a novel affinity reagent, Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Gly chloromethyl ketone (Dynorphin(1-10)-Gly11 chloromethyl ketone, DynCMK) was synthesized, and its binding characteristics to frog (Rana esculenta) brain membranes were evaluated. In competition experiments, the product shows a relatively high affinity for the kappa-opioid binding sites labelled by [3H]ethylketocyclazocine (Ki is approximately equal to 200 nM), whereas its binding to the 1 ([3H]dihydromorphine) and to the delta sites ([3H]D-Ala2-Leu5]enkephalin) is weaker. Preincubation of the frog brain membranes with DynCMK at micromolar concentrations results in a washing-resistant and dose-dependent inhibition of the [3H]ethylketocyclazocine binding sites. Saturation binding analysis of the membranes preincubated with 50 microM DynCMK reveals a significant decrease in the number of specific binding sites for [3H]ethylketocyclazocine compared to the control values. The kappa-preferring binding properties of the compound suggest that it could serve as an affinity label for the kappa-type of opioid receptors.

Substrate- and inhibitor-specificity of a non-endothelial enzyme which forms [Met5]-enkephalin from [Met5]-enkephalin-Arg6,Phe7 in isolated rabbit ear artery: pharmacological characterization

The captopril-inhibited enzyme which forms [Met5]-enkephalin from [Met5]-enkephalin-Arg6,Phe7 in isolated rabbit ear artery was characterized further by using various natural substrate candidates/analogues ([Met5]-enkephalin-Arg6,Phe7 and its amide, [Met5]-enkephalin, angiotensin I and bradykinin), peptidase inhibitors such as captopril, enalaprilate and thiorphan and by endothelial removal. 10(-5) and 10(-4) M but not 10(-6) M captopril reduced the effectiveness of [Met5]-enkephalin-Arg6,Phe7 and potentiated the effect of bradykinin but did not affect markedly the action of the other peptides. Of the inhibitors, enalaprilate was less effective than captopril, and thiorphan had no effect. The [Met5]-enkephalin-Arg6,Phe7-->[Met5]-enkephalin conversion was not affected by endothelial removal. The substrate and inhibitor spectrum of this non-endothelial enzyme activity bears no relationship in other, hitherto characterized dipeptidylcarboxypeptidases/endopeptidases known to be involved in the metabolism of the tested peptides.

Design of opioid peptides for a potential delta-receptor affinity label function: comparison with the mu-specific Tyr-D-Ala-Gly-(Me)Phe-chloromethyl ketone

To find a delta-opioid receptor preferring peptide structure containing an Asp residue in a potentially interacting position, Tyr-Pro-Phe-Asp, Tyr-D-Ala-Phe-Asp, Tyr-D-Ala-Gly-Phe-Asp, Tyr-D-Ala-Gly-Phe-Asp alpha- and beta-methyl ester and Tyr-Gly-Gly-Phe-Asp peptides were synthesized and their biological activities were analyzed in vitro in mouse vas deferens and longitudinal muscle strip of guinea pig ileum. Changing the beta-methyl ester for an alkylating chloromethyl ketone moiety in the delta-receptor-selective agonist Tyr-D-Ala-Gly-Phe-Asp-beta-methyl ester enhanced further the delta-receptor preference. The delta-receptor selective chloromethyl ketone but not the beta-methyl ester gave a very slow washout after prolonged incubation in the mouse vas deferens bioassay; however, it was still readily displaceable by naloxone. The washout pattern of mu-specific Tyr-D-Ala-Gly-(Me)Phe chloromethyl ketone did not differ in the bioassays from that of the corresponding Gly5-ol derivative. Both chloromethyl ketones gave irreversible characteristics in the receptor binding assay.

A novel opioid structure which accepts protonated as well as non-protonated nitrogen: a family of pure, delta receptor selective antagonists

Conventional opioids including opioid peptides require an "opioid" nitrogen which exists in protonated state while interacting with the receptor. In the present paper we demonstrate that the Tyr-Pro-Gly-Phe-Leu-Thr hexapeptide sequence accepts N-terminal substituents such as N-t-Boc, N-phenylacetyl and N-diphenylacetyl where the N cannot become protonated, as well as "traditional" substitutions such as N,N-diallyl, where protonation is likely under physiological conditions. The opioid peptides bearing these substituents are pure antagonists of medium affinity (Ke values in the mouse vas deferens bioassay against [Met5]-enkephalin are in the 3 x 10(-7)-4 x 10(-6) M range) with a high delta receptor preference (50-350-fold delta over mu selectivity ratios).

Opioid receptor labeling with the chloromethyl ketone derivative of (3)H-Tyr-D-Ala-Gly-(Me)Phe-Gly-ol (DAMGO) I: Binding properties of 3H-Tyr-D-Ala-Gly-(Me)Phe chloromethyl

We prepared a tritiated chloromethyl ketone derivative of Tyr-D-Ala-Gly(Me)Phe-Gly-ol 3H-D-Ala-Gly-(Me)Phe-chloromethyl ketone, and studied its binding characteristics in rat brain membranes. A significant portion (about 70%) of the binding becomes wash-resistant after 60 min of incubation. The binding of the ligand is highly stereospecific and mu-opioid receptor selective. These characteristics of the ligand, together with its high specific radioactivity (57 Ci/mmol) makes it a good candidate for biochemical characterization and covalent labeling of mu opioid receptors.

Characterization of kappa 1 and kappa 2 opioid binding sites in frog (Rana esculenta) brain membrane preparation

The distribution and properties of frog brain kappa-opioid receptor subtypes differ not only from those of the guinea pig brain, but also from that of the rat brain. In guinea pig cerebellum the kappa 1 is the dominant receptor subtype, frog brain contains mainly the kappa 2 subtype, and the distribution of the rat brain subtypes is intermediate between the two others. In competition experiments it has been established that ethylketocyclazocine and N-cyclopropylmethyl-norazidomorphine, which are nonselective kappa-ligands, have relatively high affinities to frog brain membranes. The kappa 2 ligands (Met5)enkephalin-Arg6-Phe7 and etorphine also show high affinities to the frog brain. Kappa 1 binding sites measured in the presence of 5 microM/D-Ala2-Leu5/enkephalin represent 25-30% of [3H]ethylketocyclazocine binding in frog brain membranes. The kappa 2 subtype in frog brain resembles more to the mu subtype than the delta subtype of opioid receptors, but it differs from the mu subtype in displaying low affinity toward beta-endorphin and /D-Ala2-(Me)Phe4-Gly5-ol/enkephalin (DAGO). From our data it is evident that the opioid receptor subtypes are already present in the amphibian brain but the differences among them are less pronounced than in mammalian brain.

Method for isolation of kappa-opioid binding sites by dynorphin affinity chromatography

A kappa-opioid receptor subtype was purified from a digitonin extract of frog brain membranes, using affinity chromatography. The affinity resin was prepared by coupling dynorphin (1-10) to AH Sepharose 4B. The purified receptor binds 4,750 pmol [3H]ethylketocyclazocine (EKC) per mg protein (5,600-fold purification over the membrane-bound receptor) with a Kd of 9.1 nM. The addition of cholesterol-phosphatidylethanolamine (2:1) enhanced 3.6-fold the binding activity of the purified material, which gives a purification very close to the theoretical. The purified receptor protein exhibits high affinity for kappa-selective ligands. The purified fraction shows one major band (65,000 Mr) in sodium dodecyl sulfate (SDS) gel electrophoresis.

[Perspectives of liver transplantation in Chile]

After an initial experience with 4 patients who received orthotopic liver transplant (OLT) we analyze the perspectives of establishing liver transplantation programs in Chile. An estimated 100 adult and pediatric patients require OLT a year and no more than 3 centers are required to deal with this and acquire experience with the procedure. A national organization for organ procurement is essential, given the marked difficulties in obtaining cadaver organs at present. Each procedure has an estimated cost of $5 million with 2 more millions in the first year. Thus a program for 15 patients a year may cost $ 100 million, personnel expenses not included.

Changes of dipeptidyl peptidase (DP IV) activity in the T lymphocytes of rats following administration of ACTH, dexamethasone and opiates

The aim of the work was to study the effect of glucocorticoids, opiates and stressful stimuli on dipeptidyl peptidase IV (DP IV, EC 3.4.14.5) activity of T lymphocytes prepared from the thymus of intact and adrenalectomized rats. Four week old male rats of Wistar strain were used. The in vivo administration of ACTH, dexamethasone and morphine treatment resulted in an increase of DP IV activity in the cell suspension. In adrenalectomized rats ACTH treatment failed to modify the enzyme activity, however, pain or emotional stress resulted in an elevated DP IV activity. Morphine and D-Met2-Pro5-enkephalinamide resulted in a dose dependent activation of DP IV in T cells, an effect which could be modified by naloxone pretreatment. Our findings show that DP IV mechanisms in T cells are highly sensitive to exogenous and endogenous steroids, opiates and biologically active substances released in response to stress in rats.

Structural and functional integrity of specificity and catalytic sites of trypsin

The aspartic acid residue at the bottom of the substrate-binding pocket of trypsin was replaced by glutamic acid through site-directed mutagenesis. The wild-type (Asp-189) and mutant (Glu-189) trypsinogens were expressed in E. coli, purified to homogeneity, activated by enterokinase, and tested on a series of fluorogenic tetrapeptide substrates. The substrates were of the general formula succinyl-Ala-Ala-Pro-X-AMC, where AMC is 7-amino-4-methylcoumarin and X is Lys, Arg, or Orn (ornithine). As compared to Asp-189 trypsin, the activity of Glu-189 trypsin on lysyl and arginyl substrates decreased by 3-4 orders of magnitude while its Km values did not significantly change. Lengthening the side-chain of Asp-189 by one methylene group could not be compensated for by shortening the side-chain of the substrate, since Glu-189 trypsin had no measurable activity on the ornithyl substrate. The replacement of Asp-189 with glutamic acid at the base of the substrate-binding pocket of trypsin appears to distort the structure of the critical transition-state complex. This could happen by disrupting interactions normally associated with Asp-189, and by altering the relative position of the scissile peptide bond in the active site of the enzyme.

Synthesis of 3H-Tyr-D-Ala-Gly-N(Me)Phe chloromethyl ketone--an opioid affinity label

A radioactive enkephalin affinity reagent, selective for the mu opioid receptor subtype, was synthesized by a fragment condensation method. 3H-BOC-Tyr-D-Ala-Gly-OH was prepared by catalytic tritiation of the protected iodinated tripeptide. The protected tritiated tripeptide and N(Me)Phe-CH2Cl were condensed by the mixed anhydride method. The protecting group was removed by HCl/acetic acid. The tritiated tetrapeptide has a specific radioactivity of 56.8 Ci/mmole (2.1 TBq/mmole).

Electrostatic complementarity within the substrate-binding pocket of trypsin

The aspartic residue (Asp-189) at the base of the substrate-binding pocket of trypsin was replaced by serine (present in a similar position in chymotrypsin) through site-directed mutagenesis. The wild-type (with Asp-189 in the mature trypsin sequence) and mutant (Ser-189) trypsinogens were expressed in Escherichia coli, purified to homogeneity, activated by enterokinase, and tested with a series of fluorogenic tetrapeptide substrates with the general formula succinyl-Ala-Ala-Pro-Xaa-AMC, where AMC is 7-amino-4-methyl-coumarin and Xaa is Lys, Arg, Tyr, Phe, Leu, or Trp. As compared to [Asp189]trypsin, the activity of [Ser189]trypsin on lysyl and arginyl substrates decreased by about 5 orders of magnitude while its Km values increased only 2- to 6-fold. In contrast, [Ser189]trypsin was 10-50 times more active on the less preferred, chymotrypsin-type substrates (tyrosyl, phenylalanyl, leucyl, and tryptophanyl). The activity of [Ser189]trypsin on lysyl substrate was about 100-fold greater at pH 10.5 than at pH 7.0, indicating that the unprotonated lysine is preferred. Assuming the reaction mechanisms of the wild-type and mutant enzymes to be the same, we calculated the changes in the transition-state energies for various enzyme-substrate pairs to reflect electrostatic and hydrogen-bond interactions. The relative binding energies (E) in the transition state are as follows: EII greater than EPP greater than EPA greater than EIP approximately equal to EIA, where I = ionic, P = nonionic but polar, and A = apolar residues in the binding pocket. These side-chain interactions become prominent during the transition of the Michaelis complex to the tetrahedral transition-state complex.

Covalent labeling of opioid receptors with 3H-D-Ala2-Leu5-enkephalin chloromethyl ketone. I. Binding characteristics in rat brain membranes

The chloromethyl ketone derivative of D-Ala2-Leu5-enkephalin was synthesized in a radioactive form, and the resulting compound (3H-DALECK) was used to label opioid receptors. 3H-DALECK binds with high affinity, specificity and saturability to rat brain membranes. The number of sites labeled is 130 fmoles/mg protein. Unlabeled opioids inhibited the binding of 3H-DALECK; etorphine and DAGO being most potent. A 10-fold preference for mu sites over delta was seen in site-specific competition experiments; while DALECK displayed low affinity for kappa sites of rat brain. DALECK irreversibly blocked a certain population of sites. Approximately 40% of 3H-DALECK binding at 15 min, and 60% at 60 min association time did not dissociate in the presence of a large excess of unlabeled DALECK and was resistant to washing. Autoradiography performed after SDS-PAGE revealed specific alkylation of proteins with molecular weight of 74, 65, 56, 43 and 34 kD. These results demonstrate the applicability of using 3H-DALECK to covalently label opioid receptors.

Covalent labeling of opioid receptors with 3H-D-Ala2-Leu5-enkephalin chloromethyl ketone. II. Binding characteristics in frog brain membranes

3H-D-Ala2-Leu5-enkephalin chloromethyl ketone (3H-DALECK) was used to label opioid receptors of frog brain membranes. We have previously shown (15) that 70% of the opioid receptors are of kappa type in this preparation. The binding of 3H-DALECK was of high affinity, half maximal binding being achieved by 0.9 nM of the radioligand. The number of sites labeled was calculated to be 108 fmol/mg protein. Opioid ligands, incubated with the membranes prior to the label, inhibited 3H-DALECK binding with the following rank order:etorphine greater than EKC greater than DAGO greater than DALECK greater than DADLE. Dissociation experiments showed that 70% of the binding is irreversible. Fluorography performed after SDS-PAGE revealed specific covalent labeling of protein subunits of 90, 58 and 20 kD molecular weights. Results will be compared to those obtained in rat brain (13). Our two studies demonstrate that 3H-DALECK is a useful probe for investigation the subunit structure of opioid receptors.

Purification of a kappa-opioid receptor subtype from frog brain

A kappa-opioid receptor subtype was purified from a digitonin solubilized preparation of frog brain membranes using affinity chromatography. The affinity resin was prepared by coupling D-Ala2-Leu5-enkephalin to Sepharose-6B matrix. After elution of the receptor by 50 mumol naloxone, the kappa-subtype was separated from the mu- and delta-subtypes by gel permeation chromatography on Sepharose-6B. The purified receptor binds 3,900 pmol [3H]-ethylketocyclazocine per mg protein (a 4,300-fold purification over the membrane-bound receptor) with a KD of 8.3 nM. The purified receptor protein exhibits high affinity for kappa-selective ligands. The purified fraction shows two bands (Mr 65,000 and 58,000) in sodium dodecyl sulfate gel electrophoresis.

Tyr-D-Ala-Gly-(Me)Phe-chloromethyl ketone: a mu specific affinity label for the opioid receptor

An alkylating tetrapeptide enkephalin derivative, Tyr-D-Ala-Gly-(Me)Phe-chloromethyl ketone (DAMK) was synthesized, and its binding characteristics on rat brain membranes were evaluated. In competition experiments, the product shows high affinity for the mu opioid binding site of the rat brain membranes, whereas its binding to the delta and kappa subtypes is weak. Micromolar concentrations of this ligand produce a dose-dependent, apparently irreversible inhibition of /3H/-naloxone binding, with apparent IC50 value of 1-5 uM. Neither reversibly binding opioids nor tosyl-amino acid chloromethyl ketones show these effects. Saturation binding analysis with /3H/-naloxone of membranes preincubated with Tyr-D-Ala-Gly-(Me)Phe-CH2Cl reveal a selective and irreversible inhibition of the high affinity /3H/-naloxone binding site. Irreversible blockade of mu-selective /3H/-ligand binding by Tyr-D-Ala-Gly-(Me)Phe-CH2Cl is much more effective than that of the binding of /3H/-enkephalin or /3H/-ethylketocyclazocine. The mu-selective binding properties of this new irreversible enkephalin analogue suggest that it could serve as an affinity label for the mu opioid receptor subtype.

Irreversible labelling of rat brain opioid receptors by enkephalin chloromethyl ketones

Chloromethyl ketone derivatives of leucine enkephalin (LE), D-Ala2-Leu5-enkephalin (DALE) and D-Ala2-D-Leu5-enkephalin (DADLE) were synthesized. They all show high affinity for rat brain opioid binding sites. Preincubation of the membrane fraction with enkephalin chloromethyl ketones causes a significant inhibition of /3H/-naloxone binding which cannot be reversed by extensive washing. It was found that the irreversible inhibition is selective for the high affinity (KD less than 1 nM) /3H/-naloxone binding site (putative mu-1 site). The irreversible blockade of opioid binding was partially protected by opiate alkaloids and opioid peptides, suggesting that non-specific labelling also occurs. Affinity of enkephalin chloromethyl ketones toward the mu sites is greater than that of the parent compounds. It was also found that the covalent inhibition of mu sites (/3H/-dihydromorphine and /3H/-DAGO binding) is more effective than that of delta sites (/3H/-DALE binding). We conclude that these chloromethyl ketone derivatives can be used as affinity labels for the opioid receptors, allowing us to study the structure of the mu receptor subtype.

Long term results of Roux-en-Y hepaticojejunostomy

One hundred and twenty-three patients with benign diseases involving the bile ducts, curable by biliary bypass, underwent a Roux-en-Y hepaticojejunostomy, and the long term results of this operation were evaluated to ascertain if hepaticojejunostomy is a safe and durable procedure. There were no operative deaths. A peptic ulcer developed postoperatively in two patients. Only one instance of anastomotic stenosis was observed at follow-up study, averaging 5.5 years. Six of the 11 patients with postoperative biliary symptoms had intrahepatic lithiasis, a possible indication that the symptoms were due to temporary obstruction of the anastomosis by residual stones. A refined operative technique has improved the results which over-all are highly satisfactory.

Improving cholecystectomy

Bacteriologic study of bile in 100 patients undergoing cholecystectomy for various manifestations of choletithiasis yielded 36 per cent positive cultures, with greater frequency in older individuals and those with acute cholecystitis and common duct stone; these results are comparable to those in previous studies and reaffirm the septicity of the bile. Incidence of wound infection, averanging 10 per cent in published series of cholecystectomies, was 0.5 per cent in 200 patients in whom a water-impermeable wound drape was sewn to the peritoneum to prevent contamination by potentially infected bile. This result, in patients with an infectious risk comparable to that in other series, establishes the value of meticulous wound isolation in preventing wound infection.

Portal-systemic shunt in hepatic cirrhosis: does the type of shunt decisively influence the clinical result?

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