Interfacial behavior of common food contact polymer additives.

Irganox 1076 (IN1076) and Irganox 1010 (IN1010), phenol containing species often used as antioxidant additives in food packaging polymers have both hydrophilic and hydrophobic functional groups. Consequently these additives are likely to absorb to surfaces where their free energy is minimized. Experiments described in this work examine the two-dimensional phase behavior and vibrational structure of IN1076 and IN1010 films adsorbed to the air/water interface. Surface pressure isotherms show that repeated compression of these films leads to continued irreversible loss of molecules and that on a per molecule basis, this loss is more pronounced for IN1076 than for IN1010. Differences in the surface properties of these two antioxidant additives are interpreted based on differences in molecular structure. Surface specific vibrational measurements of these organic films show very little conformational order, implying that even when closely packed, both antioxidant species have little affinity for forming highly organized domains. These findings have important ramifications for mechanisms that reduce antioxidant activity in polymers as well as descriptions of antioxidant blooming on polymer surfaces.

Failure of mannitol to reduce myocardial infarct size in the baboon.

OBJECTIVE: The aim was to determine whether mannitol, previously shown to have several myocardial protective properties, could reduce the myocardial infarct size after coronary occlusion in the baboon. METHODS: Anaesthetised baboons underwent a 2 h transient coronary artery occlusion. Each was randomised into one of two groups receiving either mannitol (n = 6) or no adjunct (n = 8). Mannitol (20%) was given at a rate of 0.4 ml.min-1 x kg-1 starting at 105 min postocclusion until reperfusion was allowed at 2 h, and at a rate of 0.2 ml.min-1 x kg-1 thereafter, until a total of 500 ml had been delivered. Changes in the ST segments were recorded with epicardial wires. The animals were killed at 24 h postocclusion and the hearts excised. Silicone microvascular dye was injected into the previously occluded coronary artery to delineate the perfusion bed. The hearts were fixed in formalin, sliced, and mounted on slides. Using planimetry the ratios of the mean volume of infarct to the mean volume of the perfusion bed (VI/VPB) were calculated and compared. RESULTS: The VI/VPB for the mannitol treated group was 71.7(SEM 14.0)% and for the control group, 65.6(6.9)% (NS). No significant difference was noted in the mean summated ST segment elevations between the two groups. CONCLUSIONS: Mannitol does not reduce myocardial infarct size or ischaemia in the baboon.

Total abdominal evisceration: an en bloc technique for abdominal organ harvesting.

This paper describes an en bloc total abdominal evisceration (TAE) technique that has been used successfully in 81 consecutive multi-organ procurements in donors ranging from 2.5 to 85 kg. Preliminary dissection performed by the surgeon and physician's assistant averaged 30 to 45 minutes before aortic cross-clamping. Removal of all abdominal organs (liver, kidneys, pancreas, bowel) en bloc averaged 16 to 24 minutes after aortic cross-clamping, depending on the speed of the thoracic procurement. Organ grafts were preserved with the University of Wisconsin preservation solution. Total procurement time for the removal of the liver, pancreas, and kidneys averaged 1.5 to 2.25 hours. Because all vascular anomalies were easily recognized ex vivo, vascular reconstruction was possible, so that all donors could potentially provide for combined liver, pancreas, and kidney transplantation. In the TAE group, primary liver graft nonfunction was 1.2% (1/81 grafts), which is less than the non-TAE liver graft nonfunction rate of 7% (7/99 grafts); this is statistically significant (p less than 0.05). Also, the incidence of fresh frozen plasma support after liver transplantation in the TAE group (2/81 transplantations) was lower than the non-TAE group (9/99 transplantations) (p less than 0.05). The overall liver recipient survival rate was 87% (non-TAE; 78/94 recipients; TAE; 65/70 recipients). Kidney-graft initial function has been similar in both the TAE and non-TAE groups. All pancreas tissue was histologically normal, and extraction of viable islet cells (average, 3600 islets per gram pancreas) was possible with yields similar to standard pancreatic (average, 379 islets per gram pancreas) harvest techniques. Preliminary experience with combined liver and whole-organ pancreas transplantations has been encouraging, with immediate discontinuation of intraoperative insulin during transplantation.

Safety and efficacy of radiofrequency thermal ablation in advanced liver tumors.

HYPOTHESIS: Radiofrequency thermal ablation (RFA) can be performed safely and effectively to control local disease in patients with advanced, unresectable liver tumors. DESIGN, SETTING, AND PATIENTS: Prospective study of 76 patients with unresectable liver tumors who underwent RFA at a private tertiary referral hospital. INTERVENTIONS: Ninety-nine RFA operations were performed to ablate 328 tumors. MAIN OUTCOME MEASURES: Complications and local recurrence. RESULTS: There was 1 death (1%), major complications occurred in 7 operations (7%), and minor complications occurred in 10 operations (10%). Local recurrence was identified in 30 tumors (9%) at a mean follow-up of 15 months. Size (P<.001), vascular invasion (P<.001), and total volume ablated (P<.001) were associated with recurrence but the number of tumors was not (P =.39). CONCLUSION: Radiofrequency thermal ablation provides local control of advanced liver tumors with low recurrence and acceptable morbidity.

Ultrasound-guided radiofrequency thermal ablation of liver tumors: percutaneous, laparoscopic, and open surgical approaches.

Only 10% to 20% of patients with primary and colorectal metastatic liver tumors are candidates for curative surgical resection. Even after curative treatment, tumors recur commonly in the liver. As a less invasive therapy, radiofrequency thermal ablation (RFA) of primary, metastatic, and recurrent liver tumors was performed under percutaneous, laparoscopic, or open intraoperative ultrasound guidance. The safety and local control efficacy of RFA were investigated. RFA was performed mostly in patients with unresectable hepatomas or metastatic liver tumors. Patients with large tumors, major vessel or bile duct invasion, limited extrahepatic metastases, or liver dysfunction were not excluded. An RFA system with a 15-gauge electrode-cannula with four-pronged retractable needles was used. All patients were followed for more than 8 months to assess morbidity and mortality, and to determine tumor recurrence. Sixty RFA operations were performed in 46 patients: 11 patients underwent repeat RFA once or twice. A total of 204 tumors were treated: 70 hepatomas and 134 metastatic tumors. Tumor size ranged from 5 mm to 180 mm (mean 36 mm). RFA was performed in 29 operations for 81 tumors percutaneously, in seven operations for 14 tumors laparoscopically, and in 24 operations for 109 tumors by open surgery. Combined colorectal resection was carried out in five operations and combined hepatic resection was carried out in three operations. There was one death (1.7%) from liver failure, and there were three major complications (5%): one case of bile leakage and two biliary strictures due to thermal injury. There were no intra-abdominal infectious or bleeding complications. The length of hospital stay ranged from 0 to 2, 1 to 3, and 4 to 7 days for percutaneous, laparoscopic, and open surgical RFA, respectively. During a mean follow-up period of 20.5 months, local tumor recurrence at the RFA site was diagnosed in 18 (8.8%) of 204 tumors. The risk factors for local recurrence included large tumor size and major vessel invasion: recurrence rates for tumors less than 4 cm, 4 to 10 cm, and greater than 10 cm, and for those with vessel invasion were 3.3%, 14.7%, 50%, and 47.8%, respectively. Ten of 18 tumors recurring locally were retreated by RFA, and eight of them showed no further recurrence. Ultrasound-guided RFA is a relatively safe, well-tolerated, and versatile treatment option that offers excellent local control of primary and metastatic liver tumors. The appropriate use of percutaneous, laparoscopic, and open surgical RFA is beneficial in the management of patients with liver tumors in a variety of situations.

A salvage technique for continuous ambulatory peritoneal dialysis catheters with exit-site infections.

Catheter infection is a major complication of continuous ambulatory peritoneal dialysis (CAPD) therapy for end-stage renal disease. Catheter exist-site infections were treated with a new surgical technique consisting of dissection and removal of the existing catheter in the subcutaneous layer, insertion of a catheter connector and new catheter piece, and creation of a new subcutaneous tunnel. The new surgery can be performed on an outpatient basis and allows for the continuation of CAPD, thereby avoiding the cost associated with inpatient admission and interim hemodialysis.

Quantitative assessment of free-radical generation during ischemia and reperfusion in the isolated rabbit heart.

BACKGROUND: Several investigators have indirectly implicated oxygen free radicals in reperfusion injury following ischemia in the isolated rabbit heart. METHODS: A quantitative assessment of free-radical production during ischemia and reperfusion was made using electron paramagnetic resonance (EPR) spectroscopy. Serial frozen (77 degrees K) tissue biopsies of the left ventricular wall in isolated rabbit hearts were performed during perfusion, ischemia, and reperfusion. These were pulverized into a fine powder that was filled into EPR tubes. EPR spectra of the tissue were recorded at 77 degrees K. RESULTS: Three predominant signals were seen on EPR analysis: signal A, g = 2.028; signal B, g = 2.005, and signal C, g = 1.940. All three signals were present during the perfusion period and decreased in size during the period of ischemia. After reperfusion, all three signals doubled in size. CONCLUSION: This study lends direct support to the theory that free radicals are generated during myocardial reperfusion and may result in reperfusion injury.

Pancreas transplantation for diabetic patients in Hawaii.

Diabetes mellitus is a common disease affecting a large population in Hawaii. Over the past 20 years, pancreas transplantation has evolved into a viable therapeutic option for selected patients with diabetes mellitus. This report describes the first combined pancreas-kidney transplant performed in Hawaii on June 28, 1993 on a patient with juvenile-onset diabetes mellitus and diabetic nephropathy. The patient has remained off insulin and off dialysis since the transplant. The history, indications, techniques, and potential complications related to this procedure are discussed.

The first non-heart-beating organ donor in Hawaii--medical and ethical considerations.

The shortage of organ donors remains a major obstacle in transplantation in Hawaii. Some patients die while waiting for a life-saving organ. Across the nation, "marginal" donors, including non-heart-beating donors are used. The authors describe the first successful non-heart-beating organ donor transplant in Hawaii, and include medical and ethical considerations.

Attitudes on organ donation among Hawaii physicians.

A survey of physicians attending the recent Hawaii Medical Association meeting was conducted in order to assess physician attitudes on organ donation. Physicians were asked 6 questions and demographics were collected. Results indicate that Hawaii physicians generally support organ donation and are aware of some of the current federal legislation regarding donation.

Hepatic cryosurgery: early experience in Hawaii.

Liver cancer, both primary and metastatic, is often deemed hopeless and patients with advanced disease cannot be offered a treatment that is completely effective. Surgical resection is the treatment of choice, but less than 20% of patients are candidates for this treatment. Hepatic cryosurgery is a relatively new procedure in which the tumor is localized intraoperatively with ultrasound guidance and exposed to liquid nitrogen at -196 degrees C. Nine cases have been performed in Hawaii, and we present the first four cases here. Of these cases, there were no mortalities and only one patient required blood transfusion. All patients currently are alive with up to 11-month follow-up. Long-term studies will be necessary to assess the effectiveness of this modality.

Liver transplantation in Hawaii.

The first liver transplant performed in Hawaii was on May 17, 1993 in a patient with end-stage liver disease caused by autoimmune hepatitis. Liver transplantation is a well-accepted treatment for end-stage liver disease with a 1-year patient survival of 80% to 85%. Early recognition of the appropriate candidate by primary care physicians and prompt referral to a liver transplant center are essential for optimal results. The indications, contraindications, organ procurement and allocation, complications, and results of liver transplantation are described. Finally, several controversial areas will be introduced, including liver transplant for alcoholic cirrhosis and hepatitis B, and use of transjugular intrahepatic portosystemic shunts (TIPS).

The need for organ donation in Hawaii.

Donor organ availability is the primary limiting factor in organ transplantation. The number of patients on the national organ waitlist has increased to more than 32,000, while the number of donors has remained fairly constant at approximately 4,500 per year. In Hawaii, there are 98 patients awaiting organ transplants, and for the past 5 years, the average number of donors per year was 15. The criteria for organ donation, brain death, approaches to donation request, and the management of the multiple organ donor are discussed.

25 years of kidney transplantation in Hawaii.

The first kidney transplant in Hawaii was performed in August 1969. In the following 25 years, more than 433 kidney transplants were performed. The most common etiology leading to transplantation was chronic glomerulonephritis. Patient and graft survivals after a kidney transplant have progressively improved, particularly after the introduction of cyclosporine in 1984. The overall one-year patient and graft survival rates now are 96% and 85%, respectively; these results exceed the national averages.

Diffusion behaviour of additives in polypropylene in correlation with polymer properties.

The migration behaviour of polymer additives in 17 polypropylene (PP) samples is described. These samples cover the major types of PP used in food packaging. The diffusion coefficients of additives with relatively small molecular masses, M(r) = 136 (limonene), as well as the migration of typical antioxidants used in PP up to M(r) = 1178 (IRGANOX 1010), were measured at different temperatures. In addition, the diffusion data and percentages of xylene-soluble fractions were correlated. This enables a prediction of the migration behaviour of a PP sample by testing its 'isotactic index' with xylene. The results clearly indicate that PP can be subdivided, from the migration point of view, into the monophasic homopolymer (h-PP), the monophasic random copolymer (r-PP), and the heterophasic copolymer (heco-PP). The diffusion coefficients for r-PP are at least one order of magnitude higher than those of h-PP and comparable with the values for heco-PP. Upper limits for the diffusion values can be calculated based on the safety margin required by consumer protection laws.

Diffusion of limonene in polyethylene.

Diffusion coefficients of limonene in various linear low-density polyethylene (LLDPE) and low-density polyethylene (LDPE) resins have been determined from sorption data using a thermogravimetric methodology. From these data, one can determine whether polymer synthesis parameters such as the choice of catalytic process or co-monomer result in substantial differences in how much food packaging additives might migrate to food. For example, LLDPE is currently manufactured using either one of two distinct catalytic processes: Ziegler-Natta (ZN) and metallocene, a single-site catalyst. ZN catalysis is a heterogeneous process that has dominated polyolefin synthesis over the last half-century. It involves a transition metal compound containing a metal-carbon bond that can handle repeated insertion of olefin units. In contrast, metallocene catalysis has fewer than 20 years of history, but has generated much interest due to its ability to produce highly stereospecific polymers at a very high yield. In addition to high stereospecificity, metallocene-catalysed polymers are significantly lower in polydispersity than traditional ZN counterparts. Absorption and desorption testing of heat-pressed films made from LLDPE and LDPE resins of varying processing parameters indicates that diffusion coefficients of limonene in these resins do not change substantially.

Effects of temperature and mixing on polymer adjuvant migration to corn oil and water.

The effect of mixing on the migration of Irganox 1010 antioxidant from polypropylene and high-density polyethylene to water and corn oil was compared at 77, 100, and 135 degrees C. Irganox 1010 migration to water is enhanced almost five-fold by mixing at 77 degrees C, whereas at 135 degrees C, mixing has only a nominal effect on migration. Irganox 1010 migration to corn oil is virtually unaffected by mixing at the temperatures studied. Migration data indicate a similar trend for Irganox 1076.

Modelling of additive diffusion in polyolefins.

A semi-empirical model has been developed for additive diffusion in polymers. The model estimates apparent diffusion coefficients of an additive migrating through polyolefin polymers into a fatty food simulant for a range of temperatures between the glass transition and melting temperatures of the polymer. This diffusion model has been applied to several additive/polyolefin systems to determine its validity and limitations.

Poly(8-methyladenylic acid): a single-stranded regular structure with alternating syn-anti conformations.

Poly(8-methyladenylic acid) has been prepared by chemical synthesis of 8-methyladenosine 5'-diphosphate and enzymatic polymerization with polynucleotide phosphorylase. The polymer exhibits a large hypochromism and cooperative melting in neutral solution. The transition temperature is independent of salt concentration at moderate ionic strength and decreases slightly at high salt. The adenine ring vibration at 1626 cm-1 is independent of temperature. A high-resolution nuclear magnetic resonance spectrum is observed near the bottom of the melting range. The chemical shift of the H2 proton exhibits a large upfield shift in the ordered form, and the temperature profile of H2 is cooperative and congruent with the UV melting curve. The CH3 proton signal, in striking contrast to H2, is independent of temperature. These results support a regular, single-stranded helix in the ordered form, in contrast to both poly(adenylic acid) and poly(8-bromoadenylic acid). We suggest that the contrasting temperature dependence of the H2 and CH3 proton signals can be accounted for by regularly alternating syn and anti conformations of the 8-methyladenylic acid residues.