What are the ideal systolic and diastolic blood pressure which do not injure the intima of iliac and coronary arteries?

 

For patients with coronary artery disease, hypertension (HTN) is a major risk factor. How could uncontrolled HTN start atherosclerosis? In our prior research, laminar flow in coronary arteries prevented the formation of plaques while turbulent flow injured the intima and triggered atherosclerosis. In this present study our question was: Which blood pressure (BP) level is optimal in not producing turbulence and so not injuring the intima?

Methods

At first, a systolic BP<120mmHg and diastolic BP<75mmHg) were arbitrarily set as controlled (group A) while a BP of >160/105mmHg as uncontrolled (group B). All patients underwent a dynamic coronary angiogram recorded at 15 images/second or 0.06 seconds per image. The first image was of the index artery completely filled with contrast. In subsequent images the blood in white color moved in over a background of black contrast (Figure 1A). In 1B, 0.06 seconds later, the blood arrived at the mid segment (white arrow). In 1C, the flood moved forward, however there was darker contrast hanging at the mid segment, marking the location of collision from the retrograde against the antegrade flow (white arrow). The reason was that in uncontrolled BP the contraction of the left ventricle was stronger so in systole, the coronary blood could reverse its course, run on a retrograde direction, collide against the antegrade flow and create turbulence (1C).

At the end, before deploying a vascular closure device, an iliac angiogram was performed. In Figure 2, on a black background of contrast, the blood in white color moved forward with a pointed tip of laminar flow. 0.06 seconds later, the laminar tip was stopped abruptly with all the layers recoiling on each other like a falling stack of dominoes. In the next image. a large swirl of disorganized mixing of blood and contrast suggested the presence of turbulence caused by the collision.

The data to be collected were (1) the duration of the antegrade and retrograde flow, (2) duration of the collision (turbulence at the collision site)

Results

In the group A (BP <120/75 mmHg), 90% of 20 patients had no retrograde flow nor collision in the iliac and short collision in coronary arteries (<0.12 secs). In 30 patients of group B (BP >160/105 mmHg), the duration of retrograde flow and collision in the iliac artery were prolonged at >0.24 msecs. In the coronary arteries, the duration was prolonged at 0.18 msecs (all p<0.05 compared with group A). These locations of turbulence correlated with the location of plaques in our prior studies.

Conclusion

In patients with uncontrolled HTN, the retrograde flow was prolonged, and the turbulence was intense. In contrary, for patients with controlled BP, there was no retrograde flow and weaker collision in coronary arteries. The results suggest that a BP of <120/75 mmHg may not trigger the atherosclerotic process. New clinical trials with larger number of patients should be performed in search for the lowest ideal blood pressure.

Funding Acknowledgement

Type of funding sources: None.

Brain injury and inflammation genes common to a number of neurological diseases and the genes involved in the genesis of GABAnergic neurons are altered in monoamine oxidase B knockout mice

Monoamine oxidase B (MAO B) oxidizes trace amine phenylethylamine (PEA), and neurotransmitters serotonin and dopamine in the brain. We reported previously that PEA levels increased significantly in all brain regions, but serotonin and dopamine levels were unchanged in MAO B knockout (KO) mice. PEA and dopamine are both synthesized from phenylalanine by aromatic L-amino acid decarboxylase in dopaminergic neurons in the striatum. A high concentration of PEA in the striatum may cause dopaminergic neuronal death in the absence of MAO B. We isolated the RNA from brain tissue of MAO B KO mice (2-month old) and age-matched wild type (WT) male mice and analyzed the altered genes by Affymetrix microarray. Differentially expressed genes (DEGs) in MAO B KO compared to WT mice were analyzed by Partek Genomics Suite, followed by Ingenuity Pathway Analysis (IPA) to assess their functional relationships. DEGs in MAO B KO mice are involved in brain inflammation and the genesis of GABAnergic neurons. The significant DEGs include four brain injury or inflammation genes (upregulated: Ido1, TSPO, AVP, Tdo2), five gamma-aminobutyric acid (GABA) receptors (down-regulated: GABRA2, GABRA3, GABRB1, GABRB3, GABRG3), five transcription factors related to adult neurogenesis (upregulated: Wnt7b, Hes5; down-regulated: Pax6, Tcf4, Dtna). Altered brain injury and inflammation genes in MAO B knockout mice are involved in various neurological disorders: attention deficit hyperactive disorder, panic disorder, obsessive compulsive disorder, autism, amyotrophic lateral sclerosis, Parkinson's diseases, Alzheimer's disease, bipolar affective disorder. Many were commonly involved in these disorders, indicating that there are overlapping molecular pathways.

Impact of COVID-19 pandemic on fecal immunochemical test screening uptake and compliance to diagnostic colonoscopy

BACKGROUND AND AIM

During this COVID-19 pandemic, Taiwan is one of the few countries where fecal immunochemical test and endoscopic activity for colorectal cancer screening keeps ongoing. We aimed to investigate how screening uptake and colonoscopy rate were affected in one of the biggest screening hubs in Northern Taiwan.

METHODS

We conducted a prospective observational study tracing and analyzing the screening uptake and the trend of compliance to diagnostic colonoscopy in fecal immunochemical test-positive subjects in the National Taiwan University Hospital screening hub since the outbreak of COVID-19 and compared it with that of the corresponding periods in the past 3 years. Cancellation and rescheduling rates of colonoscopy and related reasons were also explored.

RESULTS

Screening uptake during December 2019 to April 2020 was 88.8%, which was significantly lower than that in the corresponding period of the past 3 years (91.2-92.7%, P for trend < 0.0001). Colonoscopy rate in this period was 66.1%, which was also significantly lower than that in the past 3 years (70.2-77.5%, P for trend = 0.017). Rescheduling or cancellation rate was up to 10.9%, which was significantly higher than that in the past 3 years (P for trend = 0.023), and half of them was due to the fear of being infected.

CONCLUSION

Fecal immunochemical test screening was significantly affected by COVID-19 pandemic. In order to resume the practice in COVID-19 era, screening organizers should consider various approaches to secure timely diagnosis of colorectal cancer.

Oxidative Stress and Cardiovascular Risk in Type 1 Diabetes Mellitus: Insights From the DCCT/EDIC Study

Background

Hyperglycemia leading to increased oxidative stress is implicated in the increased risk for the development of macrovascular and microvascular complications in patients with type 1 diabetes mellitus.

Methods and Results

A random subcohort of 349 participants was selected from the DCCT / EDIC (Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications) cohort. This included 320 controls and 29 cardiovascular disease cases that were augmented with 98 additional known cases to yield a case cohort of 447 participants (320 controls, 127 cases). Biosamples from DCCT baseline, year 1, and closeout of DCCT , and 1 to 2 years post‐ DCCT ( EDIC years 1 and 2) were measured for markers of oxidative stress, including plasma myeloperoxidase, paraoxonase activity, urinary F 2α isoprostanes, and its metabolite, 2,3 dinor‐8 iso prostaglandin F 2α . Following adjustment for glycated hemoblobin and weighting the observations inversely proportional to the sampling selection probabilities, higher paraoxonase activity, reflective of antioxidant activity, and 2,3 dinor‐8 iso prostaglandin F 2α , an oxidative marker, were significantly associated with lower risk of cardiovascular disease (−4.5% risk for 10% higher paraoxonase, P <0.003; −5.3% risk for 10% higher 2,3 dinor‐8 iso prostaglandin F 2α , P =0.0092). In contrast, the oxidative markers myeloperoxidase and F 2α isoprostanes were not significantly associated with cardiovascular disease after adjustment for glycated hemoblobin. There were no significant differences between DCCT intensive and conventional treatment groups in the change in all biomarkers across time segments.

Conclusions

Heightened antioxidant activity (rather than diminished oxidative stress markers) is associated with lower cardiovascular disease risk in type 1 diabetes mellitus, but these biomarkers did not change over time with intensification of glycemic control.

Clinical Trial Registration

URL : https://www.clinicaltrials.gov . Unique identifiers: NCT 00360815 and NCT 00360893.

Sensor, Signal, and Imaging Informatics

Objective: To summarize significant contributions to sensor, signal, and imaging informatics published in 2016. Methods: We conducted an extensive search using PubMed® and Web of Science® to identify the scientific contributions published in 2016 that addressed sensors, signals, and imaging in medical informatics. The three section editors selected 15 candidate best papers by consensus. Each candidate article was reviewed by the section editors and at least two other external reviewers. The final selection of the six best papers was conducted by the editorial board of the Yearbook. Results: The selected papers of 2016 demonstrate the important scientific advances in management and analysis of sensor, signal, and imaging information. Conclusion: The growing volume of signal and imaging data provides exciting new challenges and opportunities for research in medical informatics. Evolving technologies provide faster and more effective approaches for pattern recognition and diagnostic evaluation. The papers selected here offer a small glimpse of the high-quality scientific work published in 2016 in the domain of sensor, signal, and imaging informatics.

A comparison between treatment outcomes of stage III and stage IV esophageal squamous cell carcinoma without visceral or bone metastases

e15659

Background: Although classified as end-stage, patients of stage IV esophageal squamous cell carcinoma (SCC) without visceral or bone metastases (nodal stage IV) often have good performance status and are medically fit for curative treatment. The objective of this study was to compare the prognosis of patients of stage III and nodal stage IV. Methods: The retrospective study included patients who were diagnosed esophageal squamous cell carcinoma at Tzu Chi General Hospital from Jan, 2005 to Aug, 2008. Eligible patients must meet the following criteria: (1) stage III or nodal stage IV; (2) underwent esophagectomy or chemoradiation with curative intent; (3) Eastern Cooperative Oncology Group performance status ≤2. The standard order-set of chemotherapy was two monthly cycles of fluorouracil (1,000 mg/m2/24 hours for 4 days) and cisplatin (75 mg/m2 bolus day 1). Radiotherapy dose was 59.4 Gy for concurrent chemoradiation (CCRT) or 54 Gy for adjuvant setting after esophagectomy. Results: Patients characteristics were listed in Table . The median follow-up was 8 months (range: 1∼42 months). In 38 patients underwent definitive CCRT, ten achieved complete response (CR) and 13 achieved partial response. Two-year disease-free survival rate in 28 patients who achieved CR or underwent esophagectomy was 29.9%. Median survival of stage III and nodal IV were 11.5 and 8 months. Two-year overall survival (OS) rate of stage III and nodal IV were 23.9% and 33% (p=0.814). The only significant poor prognostic factor in both univariate and multivariate analyses was tumor length longer than 5 cm. Conclusions: In our study, medically fit patients of nodal stage IV esophageal SCC could achieve OS similar to those of stage III after intensive treatment. The result may indicate the necessity of developing a selection criterion in deciding which nodal stage IV patient should undergo curative treatment. [Table: see text]

No significant financial relationships to disclose.

Clinical characteristics and course of chronic lymphocytic leukemia patients with the combination favorable and unfavorable cytogenetics

8086

Background: Patients with CLL have a highly variable clinical course. Genomic aberrations detected by FISH have been shown to correlate with survival and treatment free interval (TFI). Patients with the presence of 17p or 11q deletions (del) either alone or in combination with other cytogenetic abnormalities have the worst prognosis while patients with 13q del as a sole abnormality have the best prognosis. Our objective was to further investigate poor prognosis CLL patients with either del 17p or 11q to determine if the addition of the favorable 13q del influences the predicted clinical course and survival. Methods: We performed a retrospective chart review on 22 patients (pts) who had been identified by FISH as having either the combination of del 17p and 13q or del 11q and 13q. Results: 128 CLL FISH panels were performed from April of 2003 through October of 2006. Twenty-two pts (17%) had either del 17p and 13q (9%) or del 11q and 13q (9%). Historical data notes a frequency of 7% and 8% for deletions 17p and 11q, respectively, and 55% for 13q as a sole aberration. The median age was 66 yrs, the majority of whom were male (73%). Two of 22 pts (9%) presented with advanced stage disease. Splenomegaly was seen more often in the 17p/13q pts (36%) vs 11q/13q pts (9%). With a median follow up of 46 months since diagnosis, the median TFI for all patients (20 known) was 56 months. TFI was 13 months for patients with 17p/13q del; whereas TFI was not reached for patients with 11q/13q. Historical data noted a TFI for patients with deletions 17p, 11q, and 13q (as a sole aberration) as 9, 13, and 92 months respectively. The median survival from diagnosis was not reached for the group overall or for either combination of genetic abnormalities. Historical data noted, with 70 months follow up, a median survival of 108 months overall and 32, 79, and 133 months for 17p, 11q, and 13q (as a sole aberration) respectively. Conclusions: The addition of favorable cytogenetics, del 13q, in a CLL patient with an unfavorable cytogenetic pattern (either del 17p or del 11q) appears to improve the predicted clinical outcome and survival. Additional follow up and prospective studies are needed to further define which genetic subgroups help to prognosticate CLL patients.

No significant financial relationships to disclose.

Promoter methylation and protein expression of the Slit2 and Robo1 genes in resected esophageal squamous cell carcinoma

10032

Background: Recent epigenetic studies suggest that the slit-robo pathway is involved in tumorigenesis of a number of human cancers and a role of SLIT2 as a tumor suppressor gene. In view of lack of epigenetic studies of SLIT2 and ROBO1 genes in squamous cell esophageal carcinoma (ESCC), we investigate whether promoter methylation is responsible for aberrant protien expression of SLIT2 and ROBO1 and whether promoter methylation and aberrant protein expression of these two genes are related to prognosis after resection for ESCC. Methods: We analyzed promoter methylation of SLIT2 and ROBO1 using methylation-specific polymerase chain reaction (MSP) and their protein expression using immunohistochemistry in 60 resected tumor specimens. The Pearson χ2 test was used to compare promoter methylation and protein expression of SLIT2 and ROBO1 among patients with different clinicopathological parameters. Concordance analysis was performed between promoter methylation and protein expression of these two genes. Results: Promoter methylation of SLIT2 and ROBO1 was observed in 43 (71.6%) and 16 (26.6%) of the 60 resected specimens, respectively (P = 0.002). Aberrant protein expression of SLIT2 and ROBO1 was observed in 51 (85%) and 23 (38.3%), respectively (P < 0.001). Promoter methylation of SLIT2 correlated well with smoking (P = 0.046), betel nut chewing (P = 0.032), staging (P = 0.018) and tumor (T) factor (P < 0.001) of the TNM system and its aberrant protein expression correlated well with betel nut chewing (P = 0.038), staging (P = 0.025) and nodal (N) involvement (P = 0.004). Promoter methylation and protein expression of ROBO1 did not correlate with any of these clinicopathologic parameters. A concordance rate of 88.2% and 74.2% was present between expression of SLIT2 and ROBO1 protein and their promoter methylation (P < 0.001) and (P = 0.004), respectively. Conclusions: Aberrant expression of SLIT2 and ROBO1 protein is frequently associated with the presence of ESCC, with SLIT2 a more predominant one. Promoter methylation is one of the major mechanisms responsible for aberrant protein expression of these two genes in resected ESCC. Promoter methylation and aberrant protein expression of SLIT2 may predict prognosis after resection for ESCC.

No significant financial relationships to disclose.

Arsenic trioxide in patients with hepatocellular carcinoma: A phase II trial

14129

Background: Arsenic trioxide induces growth inhibition and apoptosis in human hepatocellular carcinoma (HCC) cell lines. A phase II trial was conducted to evaluate the efficacy and toxicity of single-agent arsenic trioxide in patients with HCC. Methods: Inclusion criteria included advanced HCC patients to whom no standard palliative treatment can be offered, good organ function and liver function reserve. Patients received arsenic trioxide 0.16–0.24 mg/kg/day for 5–6 days per week for 3–4 weeks followed by one-week rest. Tumor response was accessed every 2 months. Primary endpoint was percentage of patients with 6-month disease stabilization. Results: Twenty-nine patients (M/F = 24:5; median age: 59) with locally advanced or metastatic HCC received a total of 61 cycles (median, 2; range, 1–6). One patient had partial remission. Three patients had disease stabilization for at least six months. The 6-month tumor stabilization rate was 14% (95% CI, 1–27). The median overall survival was 4.8 months (95% CI, 1.4–8.2) and one-year survival estimated by Kaplan-Meier methodology was 30%. Conclusions: Single-agent arsenic trioxide using this dose schedule is not active against advanced HCC patients.

No significant financial relationships to disclose.

Digoxin- and monensin-induced changes of intracellular Ca2+ concentration in isolated guinea-pig ventricular myocyte

This study was undertaken to determine the possible mechanisms of actions of monensin and digoxin by using isolated guinea-pig ventricular myocytes. Since Ca2+ is the major signal for triggering contraction of cardiac muscle, the objective of this study was to determine whether monensin and digoxin affect the [Ca2+]i of cardiac myocytes and if so is this effect due to an increase in [Na+]i. Three different concentrations of digoxin (0.3, 1 and 3 micromol/l) and three different concentrations of monensin (0.3, 1 and 3 micromol/l) were used. Each treatment was monitored for two hours by using computerized fluoroscopy. Both digoxin and monensin increased the [Ca2+]i and accelerated the onset time of [Ca2+]i increase in a dose-dependent manner. Normal myocytes (loaded with fura-2 for 30 min before the treatment) were also compared with 'weakened' myocytes (loaded with fura-2 for 3 h before the treatment to create a 'weakened' condition). It was found that although 0.3 micromol/l monensin and digoxin did not change the [Ca2+]i in normal myocytes, they increased the [Ca2 +]i in 'weakened' myocytes. Finally, a Na+-free medium was used to demonstrate the effect of [Na+]o on both monensin- and digoxin-induced increases in [Ca2+]i. It was found that digoxin did not increase the [Ca2+]i in the Na+-free medium. Although monensin increased the [Ca2+]i in the Na+-free solution, this increase was not as large as in the Na+-containing medium. The results of the study led to the conclusion that the positive inotropic effect of digoxin depends on [Na+]o. However, monensin increases [Ca2+]i in Na+-dependent and -independent ways. An addition conclusion was that 'weakened' myocytes are more sensitive to the monensin and digoxin treatment than normal myocytes.

Functional changes in isolated guinea-pig papillary muscle induced by monensin and digoxin

The effects of digoxin and monensin on contraction force (CF), initial contraction velocity (ICV), average contraction velocity (ACV), initial relaxation velocity (IRV) and stimulus to response time (ST) in 'fatigued' (tired) and 'non-fatigued' (fresh) guinea-pig papillary muscles were investigated. 'Fatigued' muscles had lost 30% of their original CF with the elapse of time before they were treated. The 5 h of measurement were divided into five periods (T0 was equilibration, T1, T2, T3 and T4 were, respectively, 1, 2, 3 and 4 h after drug administration). It was found that both monensin and digoxin increased the CF, ICV and ACV at T1 and increased the IRV at T2. Digoxin lost its effect with the elapse of time while monensin did not. Digoxin also decreased the ST at T2, T3 and T4. However, monensin did not change the ST. It was also found that 'fatigued' and 'non-fatigued' guinea-pig papillary muscles did not respond to the drug treatment differently. It was concluded that the initial effects of these two drugs on guinea-pig papillary muscles are similar regarding contractility but in time digoxin loses its effect while monensin does not.

Impaired mammary gland and lymphoid development caused by inducible expression of Axin in transgenic mice

Axin is a component of the canonical Wnt pathway that negatively regulates signal transduction by promoting degradation of beta-catenin. To study the role of Axin in development, we developed strains of transgenic mice in which its expression can be manipulated by the administration of doxycycline (Dox). Animals carrying both mouse mammary tumor virus (MMTV)-reverse tetracycline transactivator and tetracycline response element (TRE)2-Axin-green fluorescent protein (GFP) transgenes exhibited Dox-dependent Axin expression and, when induced from birth, displayed abnormalities in the development of mammary glands and lymphoid tissues, both sites in which the MMTV promoter is active. The transgenic mammary glands underwent normal ductal elongation and side branching during sexual maturation and early pregnancy, but failed to develop lobulo-alveoli, resulting in a defect in lactation. Axin attenuated the expression of cyclin D1, a Wnt target that promotes the growth and differentiation of mammary lobulo-alveoli. Increased apoptosis occurred in the mammary epithelia, consistent with the inhibition of a Wnt/cyclin D1 survival signal by Axin. High levels of programmed cell death also occurred in the thymus and spleen. Immature thymocytes underwent massive apoptosis, indicating that the overexpression of Axin blocks the normal development of T lymphocytes. Our data imply that the Axin tumor suppressor controls cell survival, growth, and differentiation through the regulation of an apoptotic signaling pathway.

Poor prognosis acute myelogenous leukemia: 3--biological and molecular biological changes during remission induction therapy

This is the third paper in a series which describes a new remission induction regimen for patients with 'poor prognosis' acute myelogenous leukemia (AML). Twenty-four patients were treated with two one day pulses of chemotherapy separated by 96 h. Each pulse consisted of two doses of cytarabine and a single dose of mitoxantrone. Amifostine was administered three times a week after the second pulse of chemotherapy until treatment outcome became known. The first paper described the outcome of treatment while the second described the relationship of treatment outcome to the pretherapy characteristics of the leukemia. This paper describes the changes in the leukemia cells which occur during remission induction therapy. While only a limited number of specimens were available for each post treatment study, the studies demonstrated a profound fall in blood counts, BM cellularity, and telomerase activity in leukemia cells after pulse #1 of treatment. This fall was usually accompanied by a coordinate rise in IL6, TNFalpha, and IL1beta transcripts within the AML cells which survived chemotherapy. High levels of telomerase activity in the day 5 marrow was correlated with high levels of IL1beta transcripts which in turn were associated with treatment failure ascribable to resistant disease.

Tyrosinase degradation via two pathways during reverse translocation to the cytosol

Previous studies established that after inhibition of proteasome activity, tyrosinase could be detected in the cytosol after initial translation in the endoplasmic reticulum (ER), with a molecular weight consistent with that of a full-length, deglycosylated polypeptide. Here we show that most of these molecules are glycosylated, but have been proteolyzed at the carboxyl terminus by a protease that is insensitive to proteasome inhibitors. We also demonstrate the inhibitor-dependent accumulation of a membrane species that appears structurally homologous to the glycosylated and partially proteolyzed cytosolic form. Under some circumstances, cytosolic tyrosinase that had been deglycosylated and not proteolyzed prior to proteasomal degradation could also be detected. The presence of cytosolic tyrosinase was dependent upon glycosylation of the molecule during synthesis in the ER. These results suggest the existence of at least two alternative pathways for degradation of tyrosinase in the cytosol.

Domains of axin and disheveled required for interaction and function in wnt signaling

Disheveled blocks the degradation of beta-catenin in response to Wnt signal by interacting with the scaffolding protein, Axin. To define this interaction in detail we undertook a mutational and binding analysis of the murine Axin and Disheveled proteins. The DIX domain of Axin was found to be important for association with Disheveled and two other regions of Axin (between residues 1-168 and 600-810) were identified that can promote the association of Axin and Disheveled. We found that the DIX domain of Disheveled is critical for association with Axin in vivo and for Disheveled activity. The Disheveled DIX domain controlled the ability of Disheveled to induce the accumulation of cytosolic beta-catenin whereas the PDZ domain was not essential to this function.

Poor prognosis acute myelogenous leukemia: 1 - response to treatment with high dose cytarabine/mitoxantrone/ethyol @ (Amifostine)

Twenty patients with poor prognosis AML and four patients in the blastic phase of a myeloproliferative disorder were treated with two 'pulses' of therapy each consisting of two doses of high dose araC (separated by 12 h) followed by a single dose of mitoxantrone. The pulses were separated by 96 h. Amifostine was then administered tiw. The median age of the population was 68 years with 88% of patients having had either a prior MDS, MPD or toxic exposure. The acute leukemia of 58% of patients either entered a CR or reverted to preleukemic state. For patients under 70 years of age, treatment produced 62% CRs with a leukemia free decision marrow in 77%. For patients over 70 years the CR rate was 27% with 36% of patients having a leukemia free decision marrow.

Posttransplantation lymphoproliferative disorder of the head and neck: imaging features in seven adults

PURPOSE

To determine the cross-sectional imaging findings of posttransplantation lymphoproliferative disorder (PTLD) of the head and neck.

MATERIALS AND METHODS

Computed tomographic (CT) scans (n = 6) and magnetic resonance (MR) images (n = 2) in seven patients with histopathologically proved PTLD of the Waldeyer (lymphoid) ring or cervical lymph nodes were retrospectively reviewed for abnormalities.

RESULTS

The interval between transplantation and PTLD onset was 3.5-108 months (mean, 30 months). All patients had imaging abnormalities involving the Waldeyer ring, and focal 2.0-4. 5-cm masses were present in six patients (unilateral oropharyngeal tonsil in two, bilateral oropharyngeal tonsils in one, nasopharyngeal adenoids in three, unilateral pharyngeal tonsil and ipsilateral nasopharynx in one). In three patients, the mass was centrally low attenuating at CT or isointense to fluid at MR imaging, with enhancing solid peripheral lymphoid tissue. Three patients also had nodal findings: one with a 7-cm low-attenuating nodal mass in the right neck and two with numerous bilateral lymph nodes (mostly normal sized) in the anterior and posterior cervical lymph chains. One patient also had a small mass in the upper mediastinum.

CONCLUSION

In the setting of organ transplantation, findings of masses in the Waldeyer ring or an excessive number of cervical nodes should increase the index of suspicion of PTLD.

Can shocks timed to action potentials in low-gradient regions improve both internal and out-of-hospital defibrillation?

During the first minute of fibrillation, circulating wavefronts excite new fibrillation action potentials almost immediately following termination of the preceding action potential. The extension of refractoriness hypothesis states that a successful defibrillating shock must produce a uniform postshock refractoriness of a specific optimal duration throughout the ventricle, which blocks these wavefronts and terminates fibrillation. We hypothesized that, if shocks are appropriately timed early in the fibrillation action potential in low-voltage-gradient regions, postshock refractoriness will already be long and the shock need not be strong enough to further extend it. This will result in a lower defibrillation threshold (DFT). This hypothesis was tested in the isolated rabbit heart model. Shocks were synchronized to monophasic action potentials recorded from a low-intensity region. An up/down protocol was used. I50 for early shocks was 17% lower than that for late shocks (31% decrease in E50). Standard deviation of I50 was reduced from 32% for late shocks to 18% for early shocks. Therefore, shock synchronization improves both DFT and intersubject variability during early fibrillation. As fibrillation duration increases, action potential frequency decreases and periods of diastole occur. Because of these ischemic changes, it is uncertain whether shock timing can produce similar improvements in defibrillation under out-of-hospital conditions.

Shock timing lowers transvenous defibrillation energy requirement

Previous studies suggested that time periods exist during ventricular fibrillation when defibrillation shocks are more effective. However, there is no agreement on the amount of energy that can be saved or whether an implantable defibrillator can time shocks to these time periods. We conducted a study having two parts to investigate if there was any advantage to synchronizing internal defibrillation shocks to morphological patterns in ventricular fibrillation (VF). VF electrograms were recorded from the same three-electrode lead system used for internal defibrillation. In Part 1, we found no difference in the probability of successful defibrillation between shocks that were delivered into coarse and fine VF (48% vs 46%). However, shocks that were delivered to the upslope of coarse VF electrograms were more efficacious than those to the downslope of the waveform (67% vs 39%, P < .001). In the second study, we developed a real time computer system to prospectively deliver shocks on the upslope feature we identified in the first study. We found that the energy requirements at E50 and E80 were significantly lower for shocks delivered on the upslope of coarse VF than those delivered randomly at the end of 10 sec. We estimated a probability of success (POS) defibrillation curve using a maximum likelihood method for the timed and random shocks. The POS curve width was significantly narrower for shocks that were delivered to the upslope feature than the control treatment (7.1 +/- 0.9 vs. 10.8 +/- 1.7 J, P < 0.01). If these findings extend to clinical defibrillation, they may allow programming of internal defibrillators at lower energies. This could reduce potential postshock cardiac dysfunction, allow production of smaller devices, and improve battery life.

Identification of a domain of Axin that binds to the serine/threonine protein phosphatase 2A and a self-binding domain

Axin is a negative regulator of embryonic axis formation in vertebrates, which acts through a Wnt signal transduction pathway involving the serine/threonine kinase GSK-3 and beta-catenin. Axin has been shown to have distinct binding sites for GSK-3 and beta-catenin and to promote the phosphorylation of beta-catenin and its consequent degradation. This provides an explanation for the ability of Axin to inhibit signaling through beta-catenin. In addition, a more N-terminal region of Axin binds to adenomatous polyposis coli (APC), a tumor suppressor protein that also regulates levels of beta-catenin. Here, we report the results of a yeast two-hybrid screen for proteins that interact with the C-terminal third of Axin, a region in which no binding sites for other proteins have previously been identified. We found that Axin can bind to the catalytic subunit of the serine/threonine protein phosphatase 2A through a domain between amino acids 632 and 836. This interaction was confirmed by in vitro binding studies as well as by co-immunoprecipitation of epitope-tagged proteins expressed in cultured cells. Our results suggest that protein phosphatase 2A might interact with the Axin.APC.GSK-3.beta-catenin complex, where it could modulate the effect of GSK-3 on beta-catenin or other proteins in the complex. We also identified a region of Axin that may allow it to form dimers or multimers. Through two-hybrid and co-immunoprecipitation studies, we demonstrated that the C-terminal 100 amino acids of Axin could bind to the same region as other Axin molecules.