A dense ring of the trans-Neptunian object Quaoar outside its Roche limit

Planetary rings are observed not only around giant planets1, but also around small bodies such as the Centaur Chariklo2 and the dwarf planet Haumea3. Up to now, all known dense rings were located close enough to their parent bodies, being inside the Roche limit, where tidal forces prevent material with reasonable densities from aggregating into a satellite. Here we report observations of an inhomogeneous ring around the trans-Neptunian body (50000) Quaoar. This trans-Neptunian object has an estimated radius4 of 555 km and possesses a roughly 80-km satellite5 (Weywot) that orbits at 24 Quaoar radii6,7. The detected ring orbits at 7.4 radii from the central body, which is well outside Quaoar's classical Roche limit, thus indicating that this limit does not always determine where ring material can survive. Our local collisional simulations show that elastic collisions, based on laboratory experiments8, can maintain a ring far away from the body. Moreover, Quaoar's ring orbits close to the 1/3 spin-orbit resonance9 with Quaoar, a property shared by Chariklo's2,10,11 and Haumea's3 rings, suggesting that this resonance plays a key role in ring confinement for small bodies.

Liver transplantation outcome in patients with angiographically proven coronary artery disease: a multi-institutional study

Over the last decade the age of liver transplant (LT) recipients and the likelihood of coronary artery disease (CAD) in this population have increased. There are no multicenter studies that have examined the impact of CAD on LT outcomes. In this historical cohort study, we identified adult LT recipients who underwent angiography prior to transplantation at seven institutions over a 12-year period. For each patient we recorded demographic data, recipient and donor risk factors, duration of follow-up, the presence of angiographically proven obstructive CAD (≥50% stenosis) and post-LT survival. Obstructive CAD was present in 151 of 630 patients, the CAD(+) group. Nonobstructive CAD was found in 479 patients, the CAD(-) group. Patient survival was similar for the CAD(+) group (adjusted HR 1.13, CI = [0.79, 1.62], p = 0.493) compared to the CAD(-) group. The CAD(+) patients were further stratified into severe (CADsev, >70% stenosis, n = 96), and moderate CAD (CADmod, 50-70% stenosis, n = 55) groups. Survival for the CADsev (adjusted HR = 1.26, CI = [0.83, 1.91], p = 0.277) and CADmod (adjusted HR = 0.93, CI = [0.52, 1.66], p = 0.797) groups were similar to the CAD(-) group. We conclude that when current CAD treatment strategies are employed prior to transplant, post-LT survival is not significantly different between patients with and without obstructive CAD.

Genome dynamics and transcriptional deregulation in aging

Genome instability has been implicated as a major cause of both cancer and aging. Using a lacZ-plasmid transgenic mouse model we have shown that mutations accumulate with age in a tissue-specific manner. Genome rearrangements, including translocations and large deletions, are a major component of the mutation spectrum in some tissues at old age such as heart. Such large mutations were also induced by hydrogen peroxide (H2O2) in lacZ-plasmid mouse embryonic fibroblasts (MEFs) and demonstrated to be replication-independent. This was in contrast to ultraviolet light-induced point mutations, which were much more abundant in proliferating than in quiescent MEFs. To test if large rearrangements could adversely affect patterns of gene expression we PCR-amplified global mRNA content of single MEFs treated with H2O2. Such treatment resulted in a significant increase in cell-to-cell variation in gene expression, which was found to parallel the induction and persistence of genome rearrangement mutations at the lacZ reporter locus. Increased transcriptional noise was also found among single cardiomyocytes from old mice as compared with similar cells from young mice. While these results do not directly indicate a cause and effect relationship between genome rearrangement mutations and transcriptional deregulation, they do underscore the stochastic nature of genotoxic effects on cells and tissues and could provide a mechanism for age-related cellular degeneration in postmitotic tissue, such as heart or brain.

T cell subsets and in vitro immune regulation in "infectious" transplantation tolerance

CD4-targeted mAb therapy results in permanent acceptance of cardiac allografts in rat recipients, in conjunction with features of the infectious tolerance pathway. Although CD4(+) T cells play a central role, the actual cellular and molecular tolerogenic mechanisms remain elusive. This study was designed to analyze in vitro alloimmune responses of T lymphocytes from CD4 mAb-treated engrafted hosts. Spleen, but not lymph node, cells lost proliferative response against donor alloantigen in MLR and suppressed test allograft rejection in adoptive transfer studies, suggesting compartmentalization of tolerogenic T cells in transplant recipients. A high dose of exogenous IL-2 restored the allogeneic response of tolerogenic T cells, indicating anergy as a putative mechanism. Vigorous proliferation of the tolerogenic T cells in in vivo MLR supports the existence of alloreactive lymphocytes in tolerogenic T cell repertoire and implies an active operational suppression mechanism. The tolerogenic splenocytes suppressed proliferation of naive splenocytes in vitro, consistent with their in vivo property of dominant immune regulation. Finally, CD45RC(+) but not CD45RC(-) T cells from tolerant hosts were hyporesponsive to alloantigen and suppressed the proliferation of normal T cells in the coculture assay. Thus, nondeletional, anergy-like regulatory mechanisms may operate via CD4(+)CD45RC(+) T cells in the infectious tolerance pathway in transplant recipients.

Surveillance of wild polioviruses in patients with acute flaccid paralysis in Malta during 1998 and 1999

Certification of global poliomyelitis eradication can only be accomplished when all countries have been certified as having achieved wild poliovirus eradication. In order to achieve certification of eradication of poliomyelitis in Malta an active acute flaccid paralysis (AFP) surveillance system comprising the whole population was set up. Surveillance became effective in January 1998. During 1998, there were nine reported cases of AFP (non-polio AFP rate: 2.38 per 100,000 population) two of whom were children under 15 years of age (non-polio AFP rate: 2.52 per 100,000 for the population aged <15 years). In 1999 five cases of AFP were reported (non-polio AFP rate: 1.32 per 100,000 population). One case occurred in a child under 15 years (non-polio AFP rate: 1.28 per 100,000 for population aged <15 years). Virological investigation did not detect any wild or Sabin-like polioviruses.

Liver transplantation for adult polycystic liver disease

Polycystic liver disease, commonly associated with polycystic kidney disease, can result in massive hepatomegaly and debilitating symptoms. Surgical intervention for symptomatic polycystic liver disease has been associated with significant morbidity and inconsistent long-term palliation; it is more appropriate in patients with a single dominant cyst or cysts which is/are confined to one lobe. At our institution, nine patients have undergone orthotopic liver transplantation for symptomatic hepatic cysts with excellent long-term results and minimal morbidity and mortality. Surgical candidates were selected based on severe limitations in daily activities and on sequelae of hepatic cystic involvement. Other factors considered were the extent and pattern of hepatic cystic disease, the degree of hepatic and renal dysfunction, and prior surgical intervention. Three patients (33%) required combined liver and kidney transplantation because of renal cystic involvement with renal insufficiency. The one-year survival rate was 89% with excellent symptomatic relief and improved quality of life in all the surviving patients. One death occurred in a significantly malnourished 62-year-old female. Complications included one case each of hepatic artery thrombosis requiring retransplantation, biliary leak necessitating biliary reconstruction, and postoperative bleeding requiring re-exploration. The mean hospital stay was 23 days and the mean intraoperative blood transfusion requirement was 18 units. Our experience demonstrates that appropriately selected patients with extensive hepatic involvement with adult polycystic liver disease can have an excellent outcome with transplantation, with morbidity comparable with other surgical options.

Efficacy of tacrolimus as rescue therapy for chronic rejection in orthotopic liver transplantation: a report of the U.S. Multicenter Liver Study Group

BACKGROUND

A study was performed by 17 different U.S. liver transplantation centers to determine the safety and efficacy of conversion from cyclosporine to tacrolimus for chronic allograft rejection.

METHODS

Ninety-one patients were converted to tacrolimus a mean of 319 days after liver transplantation. The indication for conversion was ongoing chronic rejection confirmed by biochemical and histologic criteria. Patients were followed for a mean of 251 days until the end of the study.

RESULTS

Sixty-four patients (70.3%) were alive with their initial hepatic allograft at the conclusion of the study period and were defined as the responder group. Twenty-seven patients (29.7%) failed to respond to treatment, and 20 of them required a second liver graft. The actuarial graft survival for the total patient group was 69.9% and 48.5% at 1 and 2 years, respectively. The actuarial patient survival at 1 and 2 years was 84.4% and 81.2%, respectively. Two significant positive prognostic factors were identified. Patients with a total bilirubin of < or = 10 mg/dl at the time of conversion had a significantly better graft and patient survival than patients converted with a total bilirubin > 10 mg/dl (P=0.00002 and P=0.00125, respectively). The time between liver transplantation and conversion also affected graft and patient survival. Patients converted to tacrolimus < or = 90 days after transplantation had a 1-year actuarial graft and patient survival of 51.9% and 65.9%, respectively, compared with 73.2% and 87.7% for those converted > 90 days after transplantation. The mean total bilirubin level for the responder group was 7.1 mg/dl at the time of conversion and decreased significantly to a mean of 3.4 mg/dl at the end of the study (P=0.0018). Thirteen patients (14.3%) died during the study. Sepsis was the major contributing cause of death in most of these patients.

CONCLUSIONS

Our results suggest that conversion to tacrolimus for chronic rejection after orthotopic liver transplantation represents an effective therapeutic option. Conversion to tacrolimus before development of elevated total bilirubin levels showed a significant impact on long-term outcome.

Hepatic lesion characterization in cirrhosis: significance of arterial hypervascularity on dual-phase helical CT

OBJECTIVE

Our goal was to evaluate the diagnostic significance of the presence and pattern of arterial hypervascularity in lesions detected on dual-phase helical CT in cirrhotic patients.

MATERIALS AND METHODS

Fifty-eight lesions greater than 1 cm in size were prospectively identified in 26 patients with end-stage liver disease who had undergone dual-phase helical CT for preoperative liver transplantation evaluation. All 26 patients had diagnoses proven by histologic evaluation or by clinical criteria. All arterial phase scans were retrospectively reviewed and lesions were categorized for the presence and pattern of arterial hypervascularity. Radiologic findings were correlated with histopathologic data.

RESULTS

Thirty-seven of the 58 lesions had hypervascular components on arterial phase scans. All 37 of these lesions were found to represent hepatocellular carcinoma (HCC) (positive predictive value, 100%). Of the 21 remaining hypovascular lesions, 17 were HCC and four were benign (positive predictive value, 81%). Of the nine patients in whom all lesions were hypovascular, six had HCC (positive predictive value, 66%). The value of the presence of arterial hypervascularity for diagnosing HCC was statistically significant (p < .05). However, the presence or absence of arterial hypervascularity and the specific enhancement pattern revealed by helical CT did not correlate with histologic grading.

CONCLUSION

The presence of hypervascularity in hepatic masses found in cirrhotic patients is highly predictive of malignancy.

Etiology and management of symptomatic adult hepatic artery thrombosis after orthotopic liver transplantation (OLT)

Hepatic artery thrombosis (HAT) after adult orthotopic liver transplantation (OLT) is associated with fulminant sepsis and irretrievable loss of the graft. The purpose of this study was 1) to identify recipients at risk for the development of HAT; 2) to define early signs and methods for diagnosis; 3) to determine surgical treatment strategies following diagnosis of HAT. The charts of 680 adults who underwent primary OLT were reviewed. Eleven patients were symptomatic from HAT. Operative data revealed problematic arterial reconstruction in 9/11, and were related to inadequate recipient inflow, necessitating an interposition allogeneic iliac graft in seven patients, or anastomosis to aberrant right hepatic artery in two recipients. Early HAT in 4/11 occurred within 4 weeks after transplantation, whereas late thrombosis in 7/11 was identified 30 days to 1 year after OLT. The postthrombosis course was manifested by elevated liver transaminases (7/11), sepsis and recurrent cholangitis (9/11), or gas gangrene of the liver (4/11). The treatment modalities included thrombectomy and revision of the arterial anastomosis (1/11), emergency hepatectomy with temporary portocaval shunt (2/11), and urgent retransplantation (5/11). Antibiotic therapy and elective retransplantation was the treatment in 4/11. Overall 1-year patient survival and satisfactory graft function was 45 percent.

Volvulus of the Roux-en-Y hepaticojejunostomy. A rare complication manifested by recurrent ascending cholangitis

A case of volvulus of a Roux-en-Y hepaticojejunostomy causing recurrent ascending cholangitis is reported. This rare complication of biliary reconstruction was diagnosed preoperatively by percutaneous transhepatic cholangiogram, and successfully treated by resection of the involved segment. The impaired myoelectric activity of the isolated Roux limb may contribute to this pathology.

Color Doppler imaging of the hepatic vasculature

Duplex sonography added a new dimension to real-time sonographic imaging and can be used to characterize flow dynamics. Unfortunately, duplex sonography also has significant drawbacks, most of which are the result of the limited sampling ability of pulse-gated technology and the inability to provide a global display of Doppler information. Sonographic imaging of intraabdominal vessels has improved markedly with the advent of color Doppler techniques. This article reviews the use of color Doppler sonography in the evaluation of hepatic vessels. The complementary role of Doppler spectral analysis is also considered.

Prostacyclin accumulation during orthotopic liver transplantation in man

Significant hypotension commonly occurs upon reperfusion of the donor liver. In this study we tried to determine if there is accumulation of prostacyclin in the portal system. Blood samples for prostacyclin in twelve patients undergoing orthotopic liver transplantation were studied. Samples were collected at the beginning and end of portal vein anastomosis. Hemodynamic measurements were determined 1 min before and 3 min after portal revascularization. The results show an increase of prostacyclin from 524 +/- 134 pg/ml (n less than 72 pg/ml) to 1132 +/- 264 pg/ml. Eight patients had a decrease in systolic blood pressure from 98 +/- 5 mmHg to 61 +/- mmHg with concomitant significant increase in cardiac output (6.0) from 6.9 +/- 0.7 to 9.9 +/- 1.05 L/mm and significant decrease in systemic vascular resistance (SVR) from 724 +/- 130 dynes/sec/cm to 309 +/- 98. In conclusion, 60% of patients undergoing OLT accumulate prostacyclin in the portal vein, which could be one of the causes of hypotension seen at reperfusion of the donor liver.

Severe cytomegalovirus infection and immunosuppressive therapy in pediatric liver transplantation

Twenty-two post-orthotropic liver transplant (OLT) recipients were studied to investigate the clinical, laboratory and histopathological differences between rejection and CMV infection. The mean age at the time of transplantation was five years. Nine of 22 (41%) patients developed positive CMV, CF-IgG and IgM antibody titers and cultures for CMV following surgery, and three (group 1a) developed interstitial pneumonitis. CMV specific inclusion bodies were found in lung and liver biopsies. Two patients in group 1a were treated successfully with DHPG and decreasing immunosuppressive treatment, while the third died. Clinical presentation of rejection episodes were similar in all groups. CMV infected patients (group 1) received more transfusions of blood and blood products than the non-infected patients (group 2). Rejection episodes occurred sooner and more frequently in group 1a than in group 1b (CMV infected-asymptomatic) and group 2 (non-infected). Group 2 received fewer steroid boluses as well as azathioprine and OKT 3. A percutaneous liver biopsy with routine stains helped detect CMV when inclusion bodies were seen. We conclude that culture proven CMV infection is common post-OLT. Severe CMV infection occurred more frequently in those who had received greater doses of immunosuppressive therapy for possible graft rejection. Monitoring CMV infection following OLT is absolutely necessary. After OLT, decreasing the immunosuppressives and using antiviral agents are important in the management of CMV infection.

Budd-Chiari syndrome: the results of duplex and color Doppler imaging

This study was designed to evaluate duplex and color-flow Doppler imaging as potential noninvasive methods of diagnosing patients with Budd-Chiari syndrome and following them after surgery. Five patients with confirmed hepatic venoocclusive disease were imaged. All five underwent duplex Doppler examinations; three were also evaluated with color-flow Doppler. The hepatic vasculature was examined in all five patients; decompressive mesoatrial shunts were present and were evaluated in four of the five patients. Color-flow Doppler precisely defined intrahepatic, portal, and inferior vena caval circulatory dynamics. Correlation with angiography was excellent. In the two patients in whom hepatic vasculature was evaluated with duplex Doppler alone, the results were less impressive. Intrahepatic flow abnormalities were identified, but the sites of occlusion were not determined convincingly. Signals transmitted from the heart and the inability to visualize the hepatic veins made duplex Doppler evaluation problematic. Duplex Doppler was able to define patency and the direction of flow in the portal vein and inferior vena cava. Our results suggest that color-flow Doppler is an excellent technique for the initial evaluation of patients suspected of having Budd-Chiari syndrome. In the evaluation of decompressive mesoatrial shunts, color-flow Doppler produced dramatic images. However, both duplex and color-flow Doppler were highly accurate in determining the patency of decompressive shunts. Either duplex or color-flow Doppler may be used as the primary imaging procedure to determine shunt patency.

[Intraspinal epidermoid cysts and lumbar punctures]

The authors describe a case of intra-spinal epidermoid cyst and recall the scarcity of the symptoms of such tumors and their slow evolution and emphasize the very likely part taken by spinal punctures in the genesis of a number of them.

[Anhidrosis. Presentation of an unusual case report]

A one month old girl with sudden attacks of fever and dehydration was found to have anhydrosis. Histologically the sweat glands were normal but the electrical resistance of the skin showed there was an abnormality of sweating. The cause of the disorder is unknown but could be due to a defect in the secretion of acetyl choline by the post ganglionic sympathetic nerves or due to a receptor defect in the sweat gland. This new syndrome should be considered in all infants with a high fever of unknown origin.

[Benigne multi-recurrent meningitis (Mollaret's disease). A case in a child of 2 years and 8 months]

The authors report a case of meningitis, presenting all characteristics of the disease described in 1944 by P. Mollaret, occurring in a child aged 2 years and 8 months. They stress the rarity of cases on childhood. The cells found in the cerebrospinal fluid, photographs of which are included, are fragile and may undergo early lysis. They are present in association with lymphocytes and polynuclears, giving the slide examined a highly characteristic mottled appearance. The authors raise the question of the morphological similarity of these large cells, with their polygonal contour and small central nucleus, with an epithelium.