Leveraging genetically simple traits to identify small-effect variants for complex phenotypes.

BACKGROUND: Polymorphisms underlying complex traits often explain a small part (less than 1 %) of the phenotypic variance (σ2P). This makes identification of mutations underling complex traits difficult and usually only a subset of large-effect loci are identified. One approach to identify more loci is to increase sample size of experiments but here we propose an alternative. The aim of this paper is to use secondary phenotypes for genetically simple traits during the QTL discovery phase for complex traits. We demonstrate this approach in a dairy cattle data set where the complex traits were milk production phenotypes (fat, milk and protein yield; fat and protein percentage in milk) measured on thousands of individuals while secondary (potentially genetically simpler) traits are detailed milk composition traits (measurements of individual protein abundance, mineral and sugar concentrations; and gene expression). RESULTS: Quantitative trait loci (QTL) were identified using 11,527 Holstein cattle with milk production records and up to 444 cows with milk composition traits. There were eight regions that contained QTL for both milk production and a composition trait, including four novel regions. One region on BTAU1 affected both milk yield and phosphorous concentration in milk. The QTL interval included the gene SLC37A1, a phosphorous antiporter. The most significant imputed sequence variants in this region explained 0.001 σ2P for milk yield, and 0.11 σ2P for phosphorus concentration. Since the polymorphisms were non-coding, association mapping for SLC37A1 gene expression was performed using high depth mammary RNAseq data from a separate group of 371 lactating cows. This confirmed a strong eQTL for SLC37A1, with peak association at the same imputed sequence variants that were most significant for phosphorus concentration. Fitting any of these variants as covariables in the association analysis removed the QTL signal for milk production traits. Plausible causative mutations in the casein complex region were also identified using a similar strategy. CONCLUSIONS: Milk production traits in dairy cows are typical complex traits where polymorphisms explain only a small portion of the phenotypic variance. However, here we show that these mutations can have larger effects on secondary traits, such as concentrations of minerals, proteins and sugars in the milk, and expression levels of genes in mammary tissue. These larger effects were used to successfully map variants for milk production traits. Genetically simple traits also provide a direct biological link between possible causal mutations and the effect of these mutations on milk production.

Effect of temperature on heart rate in diploid and triploid brook charr, Salvelinus fontinalis, embryos and larvae.

Increased cell size in triploid fish likely affects rates of respiratory gas exchange. Respiratory deficiencies can be addressed in fish by adjustments in cardiac output, through changes in heart rate and stroke volume. The aim of this study was to determine whether heart rate differs between triploid and control (diploid) brook charr, Salvelinus fontinalis, at embryo-larval stages, when the heart is easily visible and the fish are relatively inactive. Heart rate was measured at 6, 9 and 12 degrees C at three developmental stages: eyed-egg, hatch and yolk absorption. Heart rate was unaffected by ploidy, but increased with temperature and age from a low of 43.4+/-2.2 beats/min (6 degrees C, eyed egg) to a high of 73.3+/-1.5 beats/min (12 degrees C, yolk absorption). The Q(10) for heart rate was unaffected by ploidy and age, but decreased with temperature from 1.99+/-0.28 at 6-9 degrees C to 1.72+/-0.17 at 9-12 degrees C. Triploid brook charr thus do not use adjustments in heart rate as a mechanism to deal with the physiological consequences of altered haematology at embryo-larval stages.

Mycophenolate mofetil versus azathioprine in patients surviving the initial cardiac transplant hospitalization: an analysis of the Joint UNOS/ISHLT Thoracic Registry.

BACKGROUND: Although the randomized mycophenolate mofetil- (MMF) azathioprine (AZA) trial is likely applicable to cardiac transplantation in general, it was limited to select and usually larger cardiac transplant centers and suffered from substantial cross-over and failure of many patients to receive assigned treatment drug. METHODS: The Joint ISHLT/UNOS Thoracic Registry was analyzed for the effects of MMF versus AZA in patients 1) on a cyclosporine- (CsA) based immunosuppression protocol; 2) having survived long enough to be discharged from the transplant hospitalization. RESULTS: A total of 5599 patients (4942 CsA/AZA and 657 CsA/MMF) were included with no significant differences between the MMF and AZA groups in baseline characteristics with the exception of recipient age (50 vs. 47 years), donor age (29 vs. 28 years), ischemic time (3.0 vs. 2.9 hr), and pretransplant medical condition (more AZA patients in ICU, more MMF patients on VAD). Actuarial survival was greater in the MMF group compared to the AZA group in patients surviving the initial transplant hospitalization (1 year 96 vs. 93%, 3 years 91 vs. 86%, P=0.0012). This difference was confirmed in the logistic regression analysis of 3-year mortality showing a relative risk of 0.62 (P=0.011). CONCLUSIONS: These data provide independent support for the broad applicability of the positive results from the randomized MMF-AZA clinical trial in a substantially larger patient population and confirm improved survival in patients using mycophenolate mofetil compared to azathioprine late after cardiac transplantation.

Effect of donor age on outcome of kidney transplantation. A two-year analysis of transplants reported to the United Network for Organ Sharing Registry.

The shortage of cadaveric donors coupled with a rapidly growing number of potential recipients has resulted in an increased use of older donors. In 1992, 10.7% of all cadaveric kidney transplants were from donors above the age of 55 compared with 5.4% in 1988. The present investigation serves as a follow-up of a prior study of the effect of donor age on outcome with a 2-year analysis of more than 30,000 cadaveric kidney transplants performed in the United States between October 1, 1987, and December 31, 1991, that were reported to the United Network for Organ Sharing. There was no difference between the graft survival at 1 and 2 years comparing donors aged 56-65 versus 65 and older, but the older donors (aged 56 and greater) had a 1- and 2-year graft survival that was approximately 10% and 14% less than that for recipients from the ideal age group of donors (16-45 years). There was no practical adverse interaction between donor age and recipient age, gender, diabetic status, peak PRA (panel reactive antibody activity) level of mismatch, cold ischemia time, or recipient race on outcome. The kidneys from older donors had poorer graft survival than the kidneys from younger donors when transplanted into recipients of repeat transplants, though the impact of repeat transplant and donor age on graft survival are independent of one another. These data suggest that kidneys from donors over the age of 55 overall have reduced functional reserve, which has an adverse effect on long-term function. Thus, attempts should be made to better estimate functional reserve among the older age group, but age alone should not be the sole factor for exclusion of a potential donor. The use of older donors appears to present an increased but acceptable risk of graft loss 2 years after transplant.

Effect of HLA matching on the relative risk of mortality for kidney recipients: a comparison of the mortality risk after transplant to the mortality risk of remaining on the waiting list.

BACKGROUND: Patients must wait increasingly longer periods on the kidney waiting list (WL) before receiving a transplant. Although patients can be maintained on dialysis, many deaths occur while waiting. To determine whether the risk of mortality on the WL is different from that related to the transplant procedure, data from the Organ Procurement and Transplantation Network and Scientific Registry were used to analyze all adult patients entered on the United Network for Organ Sharing (UNOS) kidney WL for a primary transplant between April 1, 1994, and December 31, 1994 (n=9925). METHODS: To account for the time spent on the WL before transplant, a time dependent, nonproportional hazards model was used to assess the risk of mortality after transplant for both well-matched (zero to two HLA mismatches) and poorly-matched (three to six HLA mismatches) transplants compared with the mortality risk of remaining on the WL. This model incorporated an exponential decay component to account for the transient increased risk after kidney transplantation. Patients were stratified by age, race, creatinine level, panel-reactive antibody at listing, and blood group. RESULTS: Although there was an increased risk of mortality in the initial posttransplant period, the risk of mortality at 1 year for transplanted patients was 59% (three to six mismatches) to 67% (zero to two mismatches) less than that of patients who remained on the waiting list for an additional year. CONCLUSIONS: Kidney transplantation is more beneficial than remaining on the waiting list. Even poorly-matched kidneys provided a significant reduction in the risk of mortality by 6 months as compared with the mortality risk of continuing to wait. Patients receive the maximum benefit when transplanted with well-matched kidneys.

Risk factors for renal allograft survival from older cadaver donors.

BACKGROUND: The shortage of cadaver donors for kidney transplantation has prompted many centers to use kidneys from older donors. The use of older donor kidneys has been associated with lower graft survival. METHODS: United Network for Organ Sharing data of all adult cadaveric renal transplant recipients receiving kidneys from adult donors between 1988 and 1994 (transplants, n=35,621) were analyzed to further study this issue. All patients were followed for a minimum of 1 year after transplantation. The recipients were classified according to donor age: group 1, 19-50 years; group 2, 51-60 years; and group 3, >60 years. RESULTS: The actuarial kidney survival estimates for group 1: (n=27,999) at 1, 3, and 5 years were 82.7%, 72.2%, and 61.4%. The corresponding values for group 2 (n=5,367) and group 3 (n=2,255) were 77.3%, 63.3%, and 51.3%; and 71.7%, 55.3%, and 42.7%, respectively (P<0.0001). Logistic regression analysis for 1-year graft survival was performed, and odds ratios (ORs) were computed for various risk factors. Increased odds of graft failure were seen with increasing donor age, previous transplantation, and elevated panel-reactive antibody. In the older donor group, lower ORs were observed if the recipients were Hispanic or Asian. In addition, kidneys from African-American or Asian donors had a poorer graft outcome. A similar analysis for 3-year graft survival for those grafts functioning at 1 year revealed poorer survival with older African-American donors (OR=1.78, P<0.02), whereas improved survival rates were seen when older kidneys were used for older (OR=0.635, P<0.01) and female (OR=0.733, P < 0.01) recipients. Statistically significant factors such as HLA mismatch, cold ischemia time, and African-American or diabetic recipients differ in their impact on graft survival across the donor age groups. CONCLUSION: In conclusion, kidneys from older donors are associated with poorer graft survival rates with African-American and Asian donors and African-American recipients, and no detrimental effects when used for older, Hispanic, Asian, or female recipients.

The results of cardiac retransplantation: an analysis of the Joint International Society for Heart and Lung Transplantation/United Network for Organ Sharing Thoracic Registry.

BACKGROUND: It is well established that repeat heart transplantation has a significantly worse outcome when compared with primary (first time) transplantation. Defining the risk factors for mortality within this group has been difficult due to small numbers of patients at individual centers. METHODS: All cardiac retransplants performed in the United States and registered in the Joint International Society for Heart and Lung Transplantation (ISHLT)/United Network for Organ Sharing (UNOS) Thoracic Registry were analyzed for demographics, morbidity posttransplantation, immunosuppression, and risk factors for mortality. RESULTS: The study cohort included 514 patients of which 81% were male with a mean age of 47+/-12 years. Time from primary transplant to retransplantation ranged from 1 day to 15.5 years and more than 50% of the patients underwent retransplantation for chronic rejection. More than 60% of patients were in the intensive care unit at the time of retransplantation and more than 40% of the patients were reported to be on some form of life support (ventricular assist device, ventilator, and/or inotropic therapy). Survival for the entire retransplant cohort was 65, 59, and 55% for 1, 2, and 3 years, respectively, but was substantially lower when the intertransplant interval was short. Conversely, when the interval between primary and retransplantation was more than 2 years, 1 year survival postretransplantation approached that of primary transplantation. Additional independent risk factors for mortality for the retransplant cohort included overall cardiac transplant center volume, the use of a ventricular assist device or ventilator, the patient being in the intensive care unit, and recipient age. The four most common causes of death were infection, primary/nonspecific graft failure, chronic rejection (allograft vasculopathy), and acute rejection. CONCLUSIONS: The data confirm that repeat heart transplantation is a higher risk procedure than primary transplantation, especially early after the primary heart transplant.

National impact of pulsatile perfusion on cadaveric kidney transplantation.

BACKGROUND: The simplicity and success of cold storage of cadaveric kidneys have led to the infrequent use of pulsatile perfusion. However, there may be advantages to pulsatile perfusion for less optimal donors. METHODS: United Network for Organ Sharing data were analyzed retrospectively to determine the impact of pulsatile perfusion on initial function and 1-year graft survival. The analysis included 60,827 cadaveric kidney transplants performed between 1988 and 1995. Multivariate logistic regression analyses were used to determine the effect of preservation method on both early kidney function (need for first-week dialysis after transplant) and 1-year graft survival, after adjusting for other known risk factors. RESULTS: The preservation method exhibited a highly significant impact on the need for first-week dialysis. Ice-preserved kidneys were associated with a 2.13-fold increase in the odds of requiring dialysis compared with perfused kidneys. If the donor age was > or =55 years, the odds were 2.33-fold higher for ice-preserved as compared with perfused. If cold ischemic time was > or =24 hr, there was a 2.19-fold increase in the odds of dialysis for ice-preserved kidneys. African-American recipients of cold-stored kidneys had a 2.29-fold greater odds of first-week dialysis. CONCLUSIONS: Based on these findings, it was estimated that the increased cost of perfusing kidneys from all donors > or =55 years of age would be balanced by the decreased need for posttransplant dialysis if the cost related to dialysis were $14,700 or greater per patient. These facts, coupled with the ability to assess an older donor kidney before transplant, could make pulsatile perfusion for the expanded donor financially as well as medically desirable.

Outcomes in recipients of combined heart-kidney transplantation: multiorgan, same-donor transplant study of the International Society of Heart and Lung Transplantation/United Network for Organ Sharing Scientific Registry.

In patients awaiting heart transplantation, end-stage disease of a second organ may occasionally require consideration of simultaneous multiorgan transplantation. Outcome statistics in multiorgan transplant recipients are needed to define optimal utilization of scarce donor resources. Incidence of cardiac allograft rejection, actuarial recipient survival, and cardiac allograft rejection-free survival were evaluated in 82 recipients of 84 simultaneous heart and kidney transplants. Twenty-three of the 82 dual-organ recipients have died with 1, 6, 12, and 24-month actuarial survival rates of 92%, 79%, 76%, and 67%, respectively. The actuarial survival rates in the heart-kidney recipients were similar to those observed in 14,340 isolated heart recipients (United Network for Organ Sharing Scientific Registry) during the same period (92%, 86%, 83%, and 79%, respectively; P=0.20). Clinical data on all episodes of treated rejection in either organ and on immunosuppressive regimens were available on 56 patients; 48% of these patients have had no rejection in either organ, 27% experienced heart rejection alone, 14% experienced kidney rejection alone, and 11% had both heart and kidney allograft rejection. Heart allograft rejection was less common in heart-kidney recipients, as compared with isolated heart transplant recipients; 0, 1, and > or = 2 treated cardiac allograft rejection episodes occurred in 63%, 20%, and 18% of heart-kidney recipients compared with 46%, 27%, and 28% of 911 isolated heart recipients reported by Transplant Cardiologists' Research Database (P=0.02). The rejection-free survival rates at 1, 3, and 6 months were 88%, 74%, and 71% in the double-organ recipients, as compared with 66%, 44%, and 39%, respectively, in the single-organ recipients. Compared with isolated heart transplantation, combined heart-kidney transplantation does not adversely affect intermediate survival and results in a lower incidence of treated cardiac allograft rejection. The findings suggest that combined heart-kidney transplantation may be an acceptable option in a small subset of potential heart transplant recipients with severe renal dysfunction.

Organ preservation solutions in heart transplantation--patterns of usage and related survival.

Despite experimental advantages for certain heart preservation solutions (HPS), their clinical popularity and related survival are uncertain. We surveyed all active UNOS heart transplant centers to determine their HPS. HPS survival benefits were tested using the UNOS heart transplant registry. Centers used from 1 to 3 types of 167 solutions. Of these formulations, 55.1% were commonly cited solutions. The other (custom) mixtures differed from those usually reported. All solutions were classified as intracellular (I, [Na++] < 70 mEq/L) or extracellular (E, [Na++] > or = 70 mEq/L). Significant variations in solution usage were observed among major regions of U.S. transplant activity (Northeast [NE], Southeast [SE], and West [W], P < 0.001). For example, 62.5% of University of Wisconsin (UW) and 49.3% of "Other" usage occurred in the NE; 75% of Roe and 100% of Collins usage occurred in the SE; and 100% of Krebs and 46% of Stanford usage occurred in the W. Logistic regression analyses of 9401 patients who underwent transplantation from 10/87 to 12/92 showed a reduction in the adjusted one month mortality odds ratio for grafts preserved with I rather than E solutions (0.85, P < 0.05). Compared with the most commonly used solution, Plegisol (20.1% of cases), the following adjusted odds ratios for one-month mortality were observed: UW, 1.09 (ns); Stanford, 0.80 (P < 0.10); Roe, 0.36 (P < 0.001); Collins, 0.82 (ns); Krebs, 0.14 (P < 0.01). Using the same one month comparison with Plegisol, 16.8% of grafts that received Custom-I solutions also fared better (0.75, P < 0.05) than the 21.4% that had Custom-E mixtures (0.91, ns). HPS usage varies greatly and there are regional preferences. There may be early survival benefits for certain intracellular HPS--however, further study is warranted to explore such relationships.

Effect of donor age and ischemic time on intermediate survival and morbidity after lung transplantation.

BACKGROUND: Pressure to expand the donor pool has required the use of lungs from older donors or from more-distant procurement areas. The long-term consequences of this policy have not yet been fully addressed. The effect of donor age and donor ischemic time on intermediate survival and important secondary end points after lung transplantation was therefore examined. METHODS: A cohort of 1,800 lung transplant recipients with complete 2-year follow-up, operated on in the United States between April 1, 1993, and March 31, 1996, was studied to assess survival. For analysis of secondary end points, the cohort was limited to 1,450 patients. RESULTS: Donor age when analyzed independently did not significantly affect intermediate survival (p = 0.4). Secondary end points were also not affected by age, with the exception of the incidence of hospitalization for rejection in the univariate analysis (p = 0.02) and in the multivariate analysis (p = 0.04). Moreover, there was not a significant impact of donor age or ischemic time independently on survival in the multivariate analysis. Similarly, when the interaction between ischemic time and donor age was examined in all of the multivariate models, none of the secondary end points were found to be significantly influenced. However, the combined interaction between donor age and ischemia time demonstrated a significantly worse survival at 2 years (p = 0.02) with donor age of > 50 years and donor ischemic time > 7 h. CONCLUSIONS: Donor age and donor ischemic time did not independently influence survival or important secondary end points after lung transplantation. However, intermediate-term survival was affected by the use of older donors when combined with a prolonged ischemic time. The impact of this combination should be considered when attempting to expand the donor pool.

Transplantation with older donor hearts for presumed "stable" recipients: an analysis of the Joint International Society for Heart and Lung Transplantation/United Network for Organ Sharing Thoracic Registry.

BACKGROUND: We have previously demonstrated that the use of older donor hearts (>45 years) increases the odds of death nearly twofold in the early posttransplantation period when compared with the use of hearts from younger donors. Before excluding this segment of the donor pool, however, the mortality risk for remaining on the waiting list compared with that of receiving an older donor heart should also be considered. METHODS: We examined all adult status 2 patients added to the United Network for Organ Sharing heart transplant waiting list for primary transplantation between 1992 and 1995 (n = 4681). To account for the transient increased risk after transplantation, we used a time-dependent nonproportional hazards model with an exponential decay component for the analysis. For patients with an equal time since listing, the resulting risk ratios represent the ratio of mortality risk for a patient who receives an older donor heart to the mortality risk for a patient who remains on the waiting list. RESULTS: After 30 days posttransplantation, the risk of death for recipients of 45- to 49-year-old donor hearts was lower than if they had remained on the waiting list, and by 6 months the relative risk was 0.37 (95% confidence interval: 0.22, 0.62). For recipients of hearts from donors 50 years or older, the risk after transplantation was lower after 64 days, and by 6 months the relative risk was 0.48 (95% confidence interval: 0.31, 0.75). CONCLUSION: These results suggest that in spite of a high initial risk resulting from the transplant procedure, there was a clear long-term survival benefit for status 2 recipients of older donor hearts. Thus overall, in spite of the increased risk of death associated with receiving older donor hearts, the risk of death without a transplant was even greater. On the basis of this analysis we cannot support the exclusion of older donors from the donor pool.

Does human leukocyte antigen matching influence the outcome of lung transplantation? An analysis of 3,549 lung transplantations.

BACKGROUND AND OBJECTIVE: Human leukocyte antigen (HLA) compatibility has been shown to improve the outcome of renal and cardiac transplantation. However, its impact on outcome following lung transplantation is not clear, with several single-center studies reporting inconsistent results. We studied the influence of HLA matching on survival and the development of rejection and obliterative bronchiolitis after lung transplantation, using data from the United Network for Organ Sharing/International Society for Heart and Lung Transplantation registry. METHODS: The study population included adult patients who received cadaveric lung transplants between October 1987 and June 1997 for whom HLA data were available. Two cohorts were examined, depending on the era of transplantation: (1) October 1987 to June 1997 (n = 3,549): Differences in actuarial survival as stratified by either the total number of HLA mismatches or the number of mismatches at each HLA locus were determined using a log-rank test. Multivariate logistic regression models were developed to determine independent predictors of survival at 1, 3, and 5 years following lung transplantation. (2) April 1994 to June 1997 (n = 1,796): The association of HLA mismatching with acute rejection and obliterative bronchiolitis was determined using a chi-squared analysis. RESULTS: Only 164 patients (4.6%) received lung grafts with 2 or fewer HLA mismatches. Univariate analyses demonstrated a significant difference in post-transplant survival by mismatch level, with the total number of HLA mismatches (p = 0.0008) and mismatching at the HLA-A locus (p = 0.002) associated with worse survival. Multivariate logistic regression demonstrated that the number of mismatches at the HLA-A and HLA-DR loci predicted 1-year mortality (incremental odds ratios 1.18, p = 0.01, and 1.15, p = 0. 03, respectively). The total number of HLA mismatches predicted 3- and 5-year mortality (incremental odds ratios 1.13 at 3 years, p = 0. 0004, and 1.14 at 5 years, p = 0.0002). However, other covariates such as repeat transplantation, transplantation for congenital heart disease, advanced recipient age, and an early era of transplantation were stronger predictors of mortality. We found no significant association between HLA mismatching and the development of obliterative bronchiolitis, although there was an association between mismatching at the HLA-A locus and acute rejection episodes requiring hospital admission (p = 0.008). We also found no association between mismatching at the HLA-B locus and rejection episodes requiring either hospitalization or the alteration of anti-rejection medications (p = 0.034). CONCLUSION: Although the number of HLA mismatches at the HLA-A and HLA-DR loci predicted 1-year mortality and the total number of mismatches predicted 3- and 5-year mortality following lung transplantation, the effect of each covariate was small in this multicenter study of 3,549 patients. Further close follow-up of registry patients is necessary to determine the effect of HLA matching on long-term survival and freedom from obliterative bronchiolitis and rejection following lung transplantation. A prospective study of HLA matching for lung transplantation should not yet be considered in view of the small number of grafts with 2 or fewer mismatches and the modest effect of HLA matching on outcome.

Single vs bilateral, sequential lung transplantation for end-stage emphysema: influence of recipient age on survival and secondary end-points.

BACKGROUND: The appropriate age to perform bilateral, sequential lung transplants (BSLT) in patients with chronic obstructive pulmonary disease (COPD) remains controversial. Although single lung transplant (SLT) offers an advantage in terms of organ availability, the long-term survival may not warrant this strategy in all age groups. METHODS: We analyzed 2,260 lung transplant recipients (1835 SLT, 425 BSLT) with COPD recorded in the International Society for Heart and Lung Transplantation/United Network for Organ Sharing thoracic registry between January 1991 and December 1997. To assess mortality, we performed univariate (Kaplan-Meier method and the chi-square statistic) and multivariate analyses (proportional hazards method). Because of incomplete morbidity data in the international registry, only data from U.S. centers (n = 1778, 1467 SLT, 311 BSLT) were used in the morbidity analysis. RESULTS: Survival rates (%) computed using the Kaplan-Meier method at 30 days, 1 year, and 5 years for the patients aged < 50 years were 93.6, 80.2, and 43.6, respectively, for the SLT patients, and 94.9, 84.7, and 68.2, respectively, for the BSLT patients. For patients aged 50 to 60 years, survival rates (%) were 93.5, 79.4, and 39.8 for the SLT patients compared with 93.0, 79.7, and 60.5 for the BSLT patients. For those aged > 60 years, SLT survival (%) was 93.0, 72.9, and 36.4, compared with 77.8 and 66.0 for the BSLT group (a 5-year rate could not be completed in this group). The multivariate model showed a higher risk ratio for mortality in patients aged 40 to 57 years who received SLT vs BSLT. Recipient age and procedure type did not appear to affect the development of rejection, bronchiolitis obliterans, bronchial stricture, or lung infection. CONCLUSIONS: Single lung transplant may offer acceptable early survival for patients with end-stage respiratory failure. However, long-term survival data favors BSLT in recipients until approximately age 60 years. These data suggest that a BSLT approach offers a significant survival advantage to recipients younger than 60 years of age.

Morbidity, functional status, and immunosuppressive therapy after heart transplantation: an analysis of the joint International Society for Heart and Lung Transplantation/United Network for Organ Sharing Thoracic Registry.

BACKGROUND: The morbidity and mortality studies on heart transplantation to date have come from single-center or multicenter studies that often have required collection of data over periods of time greater than a year. Data are now available from the International Society for Heart and Lung Transplantation/United Network for Organ Sharing (ISHLT/UNOS) Thoracic Registry from all centers in the United States performing heart transplantation, which allows analysis of morbidity and mortality rates on an annual basis. METHODS: All transplantation centers in the United States are now required to submit registration (at the time of transplantation) and 1-year follow-up clinical data on all heart transplant recipients to the ISHLT/UNOS Thoracic Registry. Data forms were submitted to the Registry regarding pretransplantation diagnoses, causes of death, rehospitalization, functional and work status at 1 year, immunosuppressive therapy, and the development of complications such as hypertension, hyperlipidemia, renal insufficiency, diabetes, and malignancy. This study is an analysis of this database for the period of April 1, 1994, through March 31, 1995, examining specifically morbidity, functional status, and other clinical events occurring during the period after the initial hospitalization and up to the first-year follow-up. The study cohort consisted of the 1853 patients who survived the initial hospitalization and for whom matching registration and 1-year follow-up forms were available. RESULTS: Rehospitalization during the first year after the initial admission was required by more than 40% of survivors, and at least one third of these required admission to the intensive care unit. Infection and rejection were the most common reasons for rehospitalization, each accounting for about 20%. Complications during the first year occurring in 10% or more of survivors included hypertension, diabetes, renal dysfunction, and hyperlipidemia. Less common complications included symptomatic bone disease, chronic liver disease, cataracts, stroke, and malignancy. Allograft function was excellent among survivors at 1 year, with a mean ejection fraction of 57.4% and less than 7% of patients requiring pacemaker therapy or having development of coronary artery disease. Eighty-three percent of survivors reported no functional limitations, but only 27% were working full-time. Eighty-nine percent of survivors were receiving prednisone at their 1-year follow-up. CONCLUSION: Clinical data are now available from the ISHLT/UNOS Thoracic Registry on the basis of the initial registration and 1-year follow-up of all patients undergoing heart transplantation in the United States. Analysis of these data from April 1, 1994, through March 31, 1995, demonstrates that the first year after the initial hospitalization for heart transplantation is a period of significant morbidity and frequent rehospitalization but excellent survival. In spite of a high level of functional capacity at 1-year follow-up, only a minority of patients return to work. The ISHLT/UNOS Thoracic Registry can now serve as a valid source of data for future analysis of trends in heart transplantation in the United States.

Influence of graft ischemic time and donor age on survival after lung transplantation.

BACKGROUND: Increased graft ischemic time and donor age are risk factors for early death after heart transplantation, but the effect of these variables on survival after lung transplantation has not been determined in a large, multinational study. METHODS: All recipients of cadaveric lung transplantations performed between October 1, 1987 and June 30, 1997 which were reported to the United Network for Organ Sharing/International Society for Heart and Lung Transplantation (UNOS/ISHLT) Registry were analyzed. Patient survival rates were estimated using Kaplan-Meier methods. Multivariate logistic regression was used to determine the impact of donor and recipient characteristics on patient survival after transplantation. To examine whether the impact of donor age varied with ischemic time, interactions between the 2 terms were examined in a separate multivariate logistic regression model. RESULTS: Kaplan-Meier survival did not differ according to the total lung graft ischemia time, but recipient survival was significantly adversely affected by young (-10 years) or old (-51 years) donor age (p = 0.01). On multivariate analysis, neither donor age nor lung graft ischemic time per se were independent predictors of early survival after transplantation, except if quadratic terms of these variables were included in the model. The interaction between donor age and graft ischemia time, however, predicted 1 year mortality after lung transplantation (p = 0.005), especially if donor age was greater than 55 years and ischemic time was greater than 6 to 7 hours. CONCLUSIONS: Graft ischemia time alone is not a risk factor for early death after lung transplantation. Very young or old donor age was associated with decreased early survival, whereas the interaction between donor age and ischemic time was a significant predictor of 1 year mortality after transplantation. Cautious expansion of donor acceptance criteria (especially as regards ischemic time) is advisable, given the critical shortage of donor lung grafts.

Design of trials of methods to reduce late renal allograft loss: the price of success.

The excellent present outcomes of renal transplantation pose major challenges for the construction of future studies of interventions to reduce late renal allograft loss. Using current data on expected renal allograft outcomes, we performed power calculations to estimate the required size of trials of primary and secondary interventions in chronic renal allograft rejection. A primary prevention trial would require recruitment of 1500 patients over three years and is probably not feasible. A secondary intervention trial would require entry of only 126 patients and is still feasible. The difficulty of performing trials using graft failure as the primary study outcome has encouraged interest in use of surrogate endpoints such as acute rejection. Using the UNOS renal transplant data base, we examined changes over time in the frequency of acute rejection within the first year and the risk of subsequent graft loss. Changes in acute rejection rates were neither parallel to nor predictive of changes in the rate of late graft loss, providing no support for the use of acute rejection as a surrogate for late graft loss. Future continued improvement in renal transplant outcomes may require changes in traditional scientific and administrative methods for evaluating the impacts of proposed interventions.

Singlet oxygen formation in monomeric and aggregated porphyrin c.

The absorption and fluorescence spectra of monomeric and aggregated species present in aqueous solutions of porphyrin c have been resolved by steady-state and time-resolved spectroscopy. The dependence of the singlet oxygen formation yield (phi delta) on excitation wavelength has also been determined. In the Q-band spectral region, the aggregate absorption and emission spectra are shifted to longer wavelengths with respect to the monomer spectrum with phi delta (monomer) = 0.59 and phi delta (aggregate) = 0.33. The relevance of these findings to the optimization of irradiation conditions in tumour phototherapy using porphyrin c are discussed.

Analysis of bovine immunoglobulin G by capillary gel electrophoresis.

A method for the analysis of bovine immunoglobulin G (IgG) using sodium dodecyl sulphate capillary gel electrophoresis (SDS-CGE) has been described. Under the electrophoretic conditions employed, monomeric and dimeric IgG were readily resolved, as were light chain and heavy chain subunits, and heavy chain dimers in reduced samples. Molecular weights determined by SDS-CGE compared favourably with those measured by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and published values. Reproducibility of protein quantitation was achieved resulting in a relative standard deviation of approximately 13% and calibration was linear in the range of 0.2-3.5 mg ml-1 protein under the conditions used.

Bioprospecting keratinous materials.

The concept of bioprospecting for bioactive peptides from keratin-containing materials such as wool, hair, skin and feathers presents an exciting opportunity for discovery of novel functional food ingredients and nutraceuticals, while value-adding to cheap and plentiful natural sources. The published literature reports multiple examples of proline-rich peptides with productive bio-activity in models of human disease including tumour formation, hypertension control and Alzheimer's disease. Bioactive peptides have been identified from food and other protein sources however the bioactivity of keratin-related proteins and peptides is largely unknown. Considering the high representation of proline-rich peptides among proven bioactive peptides, the proline-rich character of keratinous proteins supports current research. A selection of mammalian (cow epidermis, sheep wool) and avian (chicken feather) keratinous materials were subjected to enzymatic hydrolysis using established processing methods. A bio-assay of determining inhibition of early stage amyloid aggregation involved using a model fibril-forming protein - reduced and carboxymethylated bovine K-casein (RCMk-CN) and quantitation of fibril development with the amyloid-specific fluorophore, Thioflavin T (ThT). The assay was fully validated for analytical repeatability and used together with appropriate positive controls. Peptide library products derived from chicken feather (n=9), sheep wool (n=9) and bovine epidermis (n=9) were screened in the fibril inhibition assay based on K-casein. 3 of 27 products exhibited interesting levels of bio-activity with regard to fibril inhibition. HPLC profiles provide an indication of the complexity of the assemblage of peptides in the three active products. We conclude the bioprospecting research using keratinous materials shows promise for discovery of useful bioactive peptides.