Citations

The physiological role of the mitotic checkpoint protein Bub1 is unknown. To study this role, we generated a series of mutant mice with a gradient of reduced Bub1 expression using wild-type, hypomorphic, and knockout alleles. Bub1 hypomorphic mice are viable, fertile, and overtly normal despite weakened mitotic checkpoint activity and high percentages of aneuploid cells. Bub1 haploinsufficient mice, which have a milder reduction in Bub1 protein than Bub1 hypomorphic mice, also exhibit reduced checkpoint activity and increased aneuploidy, but to a lesser extent. Although cells from Bub1 hypomorphic and haploinsufficient mice have similar rates of chromosome missegregation, cell death after an aberrant separation decreases dramatically with declining Bub1 levels. Importantly, Bub1 hypomorphic mice are highly susceptible to spontaneous tumors, whereas Bub1 haploinsufficient mice are not. These findings demonstrate that loss of Bub1 below a critical threshold drives spontaneous tumorigenesis and suggest that in addition to ensuring proper chromosome segregation, Bub1 is important for mediating cell death when chromosomes missegregate.

Background Reappearance of low-frequency (LF) (±0.10 Hz) oscillations in RR interval (RR) after cardiac transplantation is indicative of sympathetic efferent reinnervation. We hypothesized that restored LF oscillations in RR in heart transplant recipients (HTRs) are linked to oscillations in muscle sympathetic nerve traffic (MSNA). Methods and Results RR, RR variability, and MSNA were recorded 5±2 months (n=7, short-term HTRs) and 138±8 months (n=7, long-term HTRs) after heart transplantation and compared with matched hypertensive patients (n=7). A coherence function determined the coupling between LF oscillations in MSNA and RR. RR variance did not differ between short-term and long-term HTRs. However, LF variability was only 1±0.5 ms 2 in the short-term HTRs but was 15±8 ms 2 in the long-term HTRs ( P <0.05). Normalized LF variability was also higher in the long-term HTRs (40±14 normalized unites) versus the short-term HTRs (6±3 normalized united, P <0.05) but did not differ from the LF variability of the hypertensive patients. Long-term HTRs were taking less cyclosporine ( P <0.01) but had higher MSNA than the short-term HTRs (62±7 versus 31±7 burst/min, respectively, P <0.05). Coherence between LF oscillations in MSNA and RR was similar in the long-term HTRs (0.59±0.11) and the hypertensive patients (0.60±0.07) and was 3-fold greater than in the short-term HTRs (0.20±0.06, P <0.05). Conclusions Cardiac reinnervation after long-term heart transplantation is characterized by a restoration of the coherence between LF oscillations in RR and MSNA. Higher MSNA in long-term than in short-term HTRs suggests that time elapsed after cardiac transplantation may be a major determinant of sympathetic excitation in heart transplant recipients.

Background Leptin, the protein product of the ob gene, has been linked to a faster heart rate in animal and human studies. The interaction between leptin and heart rate in the denervated heart is not known. Therefore, we studied the relationship between plasma leptin levels and heart rate in heart transplant recipients. Methods and Results We studied 32 male patients (mean age, 56.5±9.3 years; range, 41 to 74 years) after orthotopic heart transplantation. All subjects underwent a physical examination, anthropometric measurements, blood chemistry analysis, and office blood pressure measurements. A blood sample was collected from each subject while fasting. In univariate analysis, heart rate was related to leptin levels ( r =0.47, P =0.007) but heart rate was not related to systolic or diastolic blood pressure, mean arterial pressure, body mass index, or catecholamines. Leptin levels were only strongly associated with heart rate and body mass index ( r =0.73, P <0.0001). In multivariate analysis, heart rate was independently and positively associated with leptin levels (F=2.61, P =0.017). We also observed a strong, independent association between leptin levels and body mass index (F=5.8, P <0.00001). Conclusions We show an independent association between leptin levels and heart rate in heart transplant recipients. We speculate that this may be due, in part, to a direct effect of leptin on heart rate, conceivably mediated through cardiac leptin receptors.

Background —With the best prophylactics now available, venous thromboembolism after total knee replacement remains substantial (25% to 27%). Recombinant nematode anticoagulant protein c2 (rNAPc2) is a potent inhibitor of factor VIIa/tissue factor complex that has the potential to reduce this risk. The present study was performed to determine an efficacious and safe dose of rNAPc2 for prevention of venous thromboembolism after elective, unilateral total knee replacement. Methods and Results —This open-label, sequential dose-ranging study was conducted in 11 centers in Canada, Europe, and the United States. Five regimens were tested. Injections were administered subcutaneously on the day of surgery (day 1) and days 3, 5, and optionally, day 7. Primary efficacy outcome was a composite of overall deep vein thrombosis based on mandatory unilateral venography (day 7±2) and confirmed symptomatic venous thromboembolism recorded ≤48 hours after the last dose of rNAPc2. Primary safety outcome was major bleeding ≤72 hours after the last dose. An independent, blinded Central Adjudication Committee assessed all outcome events. Of 293 patients studied, 251 (86%) could be evaluated for primary efficacy analysis. A dosage of 3.0 μg/kg administered within 1 hour after surgery provided the best observed results, with an overall deep vein thrombosis rate of 12.2%, a proximal deep vein thrombosis rate of 1.3%, and a major bleeding rate of 2.3%. Conclusions —A randomized, double-blind trial that compared rNAPc2 with current best prophylactics is warranted based on encouraging, first-reported clinical results for a factor VIIa/tissue factor inhibitor evaluated for thrombosis prophylaxis.

Abstract Purpose: The prognosis for children with recurrent CD20+ non–Hodgkin's lymphoma is dismal. A radiolabeled anti-CD20 antibody, 90yttrium-ibritumomab-tiuxetan (90Y-IT), is Food and Drug Administration approved for adults with recurrent indolent CD20+ B cell–non–Hodgkin's lymphoma. There is no data on the safety and feasibility of 90Y-IT in refractory childhood CD20+ lymphoma. Experimental Design: Children and adolescents with refractory/relapsed CD20+ lymphoma were eligible for this phase I radioimmunotherapy study. Patients (n = 5) received rituximab (250 mg/m2 i.v.) on days 0 and 7 and indium-111 ibritumomab-tiuxetan (5 mCi i.v.) on day 0. Dosimetry studies were done on days 0, 1, 3, and 6. Immediately after rituximab on day 7, patients received 90Y-IT if dosimetry studies showed &lt;2000 cGy exposure to all solid organs and &lt;300 cGy to marrow, as well as 0.4 mCi/kg in patients with good marrow reserve (n = 3) and 0.1 mCi/kg in patients with poor marrow reserve (after bone marrow transplant; n = 2). Results: No patients experienced nonhematologic or hematologic dose-limiting toxicity. Human antimurine antibody/human antichimeric antibody incidence was 0%. One patient experienced grade II infusion–related chills associated with rituximab. The following are the means of organ radiation exposure (cGy): kidneys 341 (112-515), liver 345 (83-798), lungs 309 (155-519), marrow 46 (20-78), spleen 565 (161-816), and total body 42 (14-68). Conclusions: Based on these findings, an expanded investigator-initiated limited institutional phase II study has been designed to further evaluate the safety, tolerability, and response rate with 90Y-IT dose stratification based on marrow reserve.

Abstract Bone structure, strength, and load-strength ratios contribute to forearm fracture risk independently of areal BMD. Introduction: Technological and conceptual advances provide new opportunities for evaluating the contributions of bone density, structure, and strength to the pathogenesis of distal forearm fractures. Materials and Methods: From an age-stratified random sample of Rochester, MN, women, we compared 18 with a distal forearm fracture (cases) to 18 age-matched women with no osteoporotic fracture (controls). High-resolution pQCT was used to assess volumetric BMD (vBMD), geometry, and microstructure at the ultradistal radius, the site of Colles' fractures. Failure loads in the radius were estimated from microfinite element (μFE) models derived from pQCT. Differences between case and control women were assessed, and the risk of fracture associated with each variable was estimated by logistic regression analysis. Results: Given similar heights, estimated loading in a fall on the outstretched arm was the same in cases and controls. However, women with forearm fractures had inferior vBMD, geometry, microstructure, and estimated bone strength. Relative risks for the strongest determinant of fracture in each of the five main variable categories were as follows: BMD (total vBMD: OR per SD change, 4.2; 95% CI, 1.4–12), geometry (cortical thickness: OR, 4.0; 95% CI, 1.4–11), microstructure (trabecular number: OR, 2.3; 95% CI, 1.02–5.1), and strength (axial rigidity: OR, 3.8; 95% CI, 1.4–10); the factor-of-risk (fall load/μFE failure load) was 24% greater (worse) in cases (OR, 3.0; 95% CI, 1.2–7.5). Areas under ROC curves ranged from 0.72 to 0.82 for these parameters. Conclusions: Bone geometry, microstructure, and strength contribute to forearm fractures, as does BMD, and these additional determinants of risk promise greater insights into fracture pathogenesis.

Insulin’s effect on the synthesis of liver proteins remains to be fully defined. Previous studies using various surrogate measures of amino acyl–tRNA have reported variable results of insulin’s effect on liver protein synthesis. We determined the effect of insulin with or without amino acid supplementation on the synthesis rates of liver proteins (tissue, albumin, and fibrinogen) using l-[1-13C]Leu as a tracer in 24 male miniature swine. In addition, we compared the isotopic enrichment of different precursors of liver proteins with that of amino acyl−tRNA using l-[1-13C]Leu and l-[15N]Phe as tracers. Although liver tissue fluid enrichment of [13C]Leu and [15N]Phe and that of plasma [13C]ketoisocaproatic acid (KIC) were very similar to that of tRNA, plasma isotopic enrichment of both Leu and Phe were substantially higher (P &lt; 0.01) and VLDL apolipoprotein-B100 enrichment was lower (P &lt; 0.01) than the respective amino acyl−tRNA enrichment. Plasma KIC enrichment most accurately predicted leucyl-tRNA enrichment, whereas plasma Leu enrichment was best correlated with that of tRNA. Neither insulin alone nor insulin plus amino acid infusion had an effect on liver tissue protein synthesis. In contrast, insulin alone decreased the albumin synthesis rate, and insulin with amino acids maintained the albumin synthesis rate. Insulin with or without amino acids inhibited the fibrinogen synthesis rate. These results, based on synthetic rates using amino acyl–tRNA, were consistent with those obtained using KIC or tissue fluid Leu or Phe as precursor pools. These studies demonstrated that plasma KIC enrichment is a convenient and reliable surrogate measure of leucyl-tRNA in liver. We also concluded that insulin has differential effects on the synthesis rates of liver proteins. Whereas insulin with or without amino acid supplement has no acute effect on the synthesis of liver tissue protein, insulin has a substantial inhibitory effect on fibrinogen synthesis. In contrast, insulin administration along with amino supplement is necessary to maintain albumin synthesis rate.

Fasting hypoglycemia, which persisted for 3 days after insulin treatment was stopped,occurred in a patient with non-insulin-dependent diabetes mellitus who had inappropriate plasma free-insulin levels (18–25 μU/ml) and extremely high antibody-bound insulin (&gt;20,000 μU/ml) but normal counterregulatory hormone secretion and plasma C-peptide levels. The amount of antibody-bound insulin decreased in a biphasic pattern over13 mo of observation with an initial half-life of 35 days and a more gradual decrease with a half-life of 160 days. The number of high-affinity antibody binding sites was virtually identical to the amount of antibody-bound insulin in the patient's plasma. We conclude that the patient's fasting hyperinsulinemia and hypoglycemia were due to release of antibody-bound insulin.

Abstract Percutaneous cholecystostomy offers a potentially important therapeutic modality for critically ill patients with acute cholecystitis who represent a high risk for general anaesthesia. The aim of the study was to assess experience with percutaneous cholecystostomy in resolving the acute episode of cholecystitis without operative intervention. Twenty-two consecutive patients with a clinical diagnosis of acute cholecystitis underwent the procedure. All were at high risk for general anaesthesia, and all but one developed cholecystitis while hospitalized for another co-morbid condition; 14 were in an intensive care unit. Twenty-one of the 22 patients proved to have acute cholecystitis (11 acalculous, ten cholelithiasis). There were no acute technical complications. Toxaemia resolved in 17 of the 21 patients with acute cholecystitis. Acute cholecystitis failed to resolve in three patients; all died within 48 h from overwhelming generalized sepsis. One patient required emergency cholecystectomy for bile peritonitis when the cholecystostomy catheter became dislodged 24 h after placement. The 60-day mortality rate for the acalculous and calculous patient groups was 55 and 20 per cent, respectively. Only three interval cholecystectomies have been performed at a mean follow-up of 19 months. In conclusion, percutaneous cholecystostomy may be the procedure of choice for the management of acute cholecystitis in the very high-risk critically ill patient. If symptoms fail to resolve quickly, ongoing sepsis, cholangitis or gallbladder necrosis should be suspected.