Better Late Than Never

Symptomatic bradycardia may be iatrogenic or from a conduction system abnormality. Here we show an interesting case of iatrogenic symptomatic bradycardia that may be confused with a conduction system abnormality. (Level of Difficulty: Advanced.).

Study and modulation of cardiac electroporation with a novel model utilizing human induced pluripotent stem cells

Background

Cardiac electroporation is a promising novel non-thermal ablation method, gaining significant interest with recent first-in-man data suggesting effective cardiac lesion generation with no collateral damage. Nevertheless, significant knowledge gaps exist regarding its electrophysiological consequences in cardiomyocytes, including; cell specificity, protocol optimization, irreversibility threshold, recovery time-constants, and the mechanistic nature of its cytolytic and anti-arrhythmic properties.

Purpose

Establishing an innovative in-vitro model for the study of cardiac electroporation-ablation, utilizing human induced pluripotent stem cells (hiPSCs).

Methods and results

Healthy-control hiPSC-derived cardiomyocytes were enzymatically dissociated and seeded as circular cell sheets (hiPSC-CCSs). Electroporation-ablation experiments were performed using a custom designed high-frequency electroporation (HF-EP) generator. Two needle-shaped electrodes were used for HF-EP delivery (Figure 1). Subsequently, detailed voltage- and Ca2+-mapping studies of the hiPSC-CCSs were conducted (Figure 2). HF-EP application resulted in the generation of electrically isolated lesions within the hiPSC-CCSs (Figure 3). Further characterization of the temporal changes and electrophysiological properties following electroporation revealed that; (1) lesions persisted over prolonged periods of time (days), indicating irreversible electroporation, (2) a temporal decrease in lesion dimensions was noted, consistent with a significant reversible electroporation component (Figures 3–5), (3) most tissue recovery had occurred within the first 15 minutes following electroporation, with little recovery beyond that time-frame, (4) increasing pulse-number augmented lesion area as well as the proportion of irreversible damage, and (5) electroporation sensitization was achieved by increasing extracellular Ca2+, indicating its crucial role in electroporation cytolysis, potentially via direct cellular toxicity and apoptosis facilitation (Figures 5–6). Finally, evaluating for HF-EP anti-arrhythmic properties, we targeted multiple rotors or focal triggered-activity generated in the hiPSC-CCSs. HF-EP application generated sustained line-blocks, isolating arrhythmogenic substrates within the hiPSC-CCSs while blocking the propagation of arrhythmic wavefronts (Figure 7).

Conclusion

Our results demonstrate the ability to study cardiac electroporation utilizing hiPSC-derived cardiomyocytes, provide novel insights into its temporal and electrophysiological characteristics, facilitate electroporation protocol optimization, screen for potential electroporation sensitizers, and to study its mechanistic nature and anti-arrhythmic properties.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Division of Cardiology, and Tamman Cardiovascular Research Institute, Leviev Heart Center, Sheba Medical Center - Tel Hashomer, Ramat-Gan, Israel Figures 1–4Figures 5–7

Isolated superfused rats atrial model for the investigation of atrial fibrillation mechanisms and treatment

Background

One of the major barriers to an improved mechanistic understanding of atrial fibrillation (AF), and thus in the pipeline of drug development, has been a lack of appropriate tissue models, especially in small animals.

Aim

We propose an advanced anatomical ex-vivo model based on rat atria for acute assessment of AF susceptibility. This novel model could yield a better understanding of arrhythmia mechanisms as well as the development of potential therapeutic strategies for the prevention or termination of atrial arrhythmias.

Methods

Wistar rats atria (N=25) were isolated, flattened and pinned to a custom-made silicon plate. Atria were superfused with an oxygenized Tyrode's solution. Tissues were then loaded with a voltage-sensitive dye and mapped using a high-resolution optical mapping system. AF was induced with 1uM carbamylcholine (N=23) coupled with pacing maneuvers and treated with 30uM Vernakalant (N=10) or 10uM Flecainide (N=10). Finally, the feasibility of a new ablation technique (electroporation) was evaluated.

Results

Optical mapping results suggested that the superfusion procedure led to a fast atrial recovery. Sinus activity was conserved for all atria for a long period. All the anatomical landmarks were clearly visualized. The acquired optical signals were analyzed during sinus rhythm and pacing, which allowed the creation of detailed activation maps and measurements of action potential duration (APD) and conduction velocity (CV) at different pacing rates. The resulting APD restitution curves revealed electrical excitation at high pacing rates (cycle length between 50ms and 300ms) with a relatively flattened curve. AF was successfully induced and optically mapping confirmed the presence of reentrant activity. AF was successfully treated using Vernacalant and Flecainide. Finally, we demonstrated the feasibility of a new ablation approach (electroporation) for creation of a continuous linear lesion serving as a functional block.

Conclusion

The isolated superfused atria model, coupled with voltage-sensitive dyes, can be utilized for long-term high-resolution functional imaging of the atria during sinus rhythm, pacing and arrhythmogenic activity. This allows the study of the atrial electrophysiological properties, the mechanisms involved in AF initiation, perpetuation, and termination as well as the study of drug and new ablation modalities.

Funding Acknowledgement

Type of funding sources: Public grant(s) – EU funding. Main funding source(s): European Research Council (ERC) Spontaneous activation of isolated atria

Thermoreflectance Imaging of (Ultra)wide Band-Gap Devices with MoS2 Enhancement Coatings

Measuring the maximum operating temperature within the channel of ultrawide band-gap transistors is critically important since the temperature dependence of the device reliability sets operational limits such as maximum operational power. Thermoreflectance imaging (TTI) is an optimal choice to measure the junction temperature due to its submicrometer spatial resolution and submicrosecond temporal resolution. Since TTI is an imaging technique, data acquisition is orders of magnitude faster than point measurement techniques such as Raman thermometry. Unfortunately, commercially available LED light sources used in thermoreflectance systems are limited to energies less than ∼3.9 eV, which is below the band gap of many ultrawide band-gap semiconductors (>4.0 eV). Therefore, the semiconductors are transparent to the probing light sources, prohibiting the application of TTI. To address this thermal imaging challenge, we utilize an MoS₂ coating as a thermoreflectance enhancement coating that allows for the measurement of the surface temperature of (ultra)wide band-gap materials. The coating consists of a network of MoS₂ nanoflakes with the c axis aligned normal to the surface and is easily removable via sonication. The method is validated using electrical and thermal characterization of GaN and AlGaN devices. We demonstrate that this coating does not measurably influence the electrical performance or the measured operating temperature. A maximum temperature rise of 49 K at 0.59 W was measured within the channel of the AlGaN device, which is over double the maximum temperature rise obtained by measuring the thermoreflectance of the gate metal. The importance of accurately measuring the peak operational temperature is discussed in the context of accelerated stress testing.

Comparative Effectiveness of Rivaroxaban, Apixaban, and Warfarin in Atrial Fibrillation Patients With Polypharmacy

BACKGROUND AND PURPOSE

Comparative effectiveness and safety of oral anticoagulants in patients with atrial fibrillation and high polypharmacy are unknown.

METHODS

We used Medicare administrative data to evaluate patients with new atrial fibrillation diagnosis from 2015 to 2017, who initiated an oral anticoagulant within 90 days of diagnosis. Patients taking ≤3, 4 to 8, or ≥9 other prescription medications were categorized as having low, moderate, or high polypharmacy, respectively. Within polypharmacy categories, patients receiving apixaban 5 mg twice daily, rivaroxaban 20 mg once daily, or warfarin were matched using a 3-way propensity score matching. Study outcomes included ischemic stroke, bleeding, and all-cause mortality.

RESULTS

The study cohort included 6985 patients using apixaban, 3838 using rivaroxaban, and 6639 using warfarin. In the propensity-matched cohorts there was no difference in risk of ischemic stroke between the 3 drugs in patients with low and moderate polypharmacy. However, among patients with high polypharmacy, the risk of ischemic stroke was higher with apixaban compared with warfarin (adjusted hazard ratio 2.34 [95% CI, 1.01-5.42]; P=0.05) and similar to rivaroxaban (adjusted hazard ratio, 1.38 [95% CI, 0.67-2.84]; P=0.4). There was no difference in risk of death between the 3 drugs in patients with low and moderate polypharmacy, but apixaban was associated with a higher risk of death compared with rivaroxaban (adjusted hazard ratio, 2.03 [95% CI, 1.01-4.08]; P=0.05) in the high polypharmacy group. Apixaban had lower bleeding risk compared with warfarin in the low polypharmacy group (adjusted hazard ratio, 0.54 [95% CI, 0.32-0.90]; P=0.02), but there was no difference in bleeding between the 3 drugs in the moderate and high polypharmacy groups.

CONCLUSIONS

Our study suggests that among patients with significant polypharmacy (>8 drugs), there may be a higher stroke and mortality risk with apixaban compared with warfarin and rivaroxaban. However, differences were of borderline significance.

Transferrable AlGaN/GaN High-Electron Mobility Transistors to Arbitrary Substrates via a Two-Dimensional Boron Nitride Release Layer

Mechanical transfer of high-performing thin-film devices onto arbitrary substrates represents an exciting opportunity to improve device performance, explore nontraditional manufacturing approaches, and paves the way for soft, conformal, and flexible electronics. Using a two-dimensional boron nitride release layer, we demonstrate the transfer of AlGaN/GaN high-electron mobility transistors (HEMTs) to arbitrary substrates through both direct van der Waals bonding and with a polymer adhesive interlayer. No device degradation was observed because of the transfer process, and a significant reduction in device temperature (327-132 °C at 600 mW) was observed when directly bonded to a silicon carbide (SiC) wafer relative to the starting wafer. With the use of a benzocyclobutene (BCB) adhesion interlayer, devices were easily transferred and characterized on Kapton and ceramic films, representing an exciting opportunity for integration onto arbitrary substrates. Upon reduction of this polymer adhesive layer thickness, the AlGaN/GaN HEMTs transferred onto a BCB/SiC substrate resulted in comparable peak temperatures during operation at powers as high as 600 mW to the as-grown wafer, revealing that by optimizing interlayer characteristics such as thickness and thermal conductivity, transferrable devices on polymer layers can still improve performance outputs.

Thermal characterization of gallium oxide Schottky barrier diodes

The higher critical electric field of β-gallium oxide (Ga₂O₃) gives promise to the development of next generation power electronic devices with improved size, weight, power, and efficiency over current state-of-the-art wide bandgap devices based on 4H-silicon carbide (SiC) and gallium nitride (GaN). However, it is expected that Ga₂O₃ devices will encounter serious thermal issues due to the poor thermal conductivity of the material. In this work, self-heating in Ga₂O₃ Schottky barrier diodes under different regimes of the diode operation was investigated using diverse optical thermography techniques including thermoreflectance thermal imaging, micro-Raman thermography, and infrared thermal microscopy. 3D coupled electro-thermal modeling was used to validate experimental results and to understand the mechanism of heat generation for the diode structures. Measured top-side and cross-sectional temperature fields suggest that device and circuit engineers should account for the concentrated heat generation that occurs near the anode/Ga₂O₃ interface and/or the lightly doped drift layer under both forward and high voltage reverse bias conditions. Results of this study suggest that electro-thermal co-design techniques and top-side thermal management solutions are necessary to exploit the full potential of the Ga₂O₃ material system.

In situ transmission electron microscopy of transistor operation and failure

Microscopy is typically used as a post-mortem analytical tool in performance and reliability studies on nanoscale materials and devices. In this study, we demonstrate real time microscopy of the operation and failure of AlGaN/GaN high electron mobility transistors inside the transmission electron microscope. Loading until failure was performed on the electron transparent transistors to visualize the failure mechanisms caused by self-heating. At lower drain voltages, thermo-mechanical stresses induce irreversible microstructural deformation, mostly along the AlGaN/GaN interface, to initiate the damage process. At higher biasing, the self-heating deteriorates the gate and catastrophic failure takes place through metal/semiconductor inter-diffusion and/or buffer layer breakdown. This study indicates that the current trend of recreating the events, from damage nucleation to catastrophic failure, can be replaced by in situ microscopy for a quick and accurate account of the failure mechanisms.

Imaging Cyclotron Orbits of Electrons in Graphene

Electrons in graphene can travel for several microns without scattering at low temperatures, and their motion becomes ballistic, following classical trajectories. When a magnetic field B is applied perpendicular to the plane, electrons follow cyclotron orbits. Magnetic focusing occurs when electrons injected from one narrow contact focus onto a second contact located an integer number of cyclotron diameters away. By tuning the magnetic field B and electron density n in the graphene layer, we observe magnetic focusing peaks. We use a cooled scanning gate microscope to image cyclotron trajectories in graphene at 4.2 K. The tip creates a local change in density that casts a shadow by deflecting electrons flowing nearby; an image of flow can be obtained by measuring the transmission between contacts as the tip is raster scanned across the sample. On the first magnetic focusing peak, we image a cyclotron orbit that extends from one contact to the other. In addition, we study the geometry of orbits deflected into the second point contact by the tip.

[Focal liver lesions in patients with malignant haematological disease: value of B-mode ultrasound in comparison to contrast-enhanced ultrasound--a retrospective study with N = 61 patients]

PURPOSE

The aim of the retrospective study is to illustrate the role of contrast-enhanced ultrasound (CEUS) in the dignity assessment of focal liver lesions compared to B-mode ultrasound (US) in patients with malignant haematological diseases (MHD).

PATIENTS AND METHODS

Focal liver lesions were diagnosed in n = 61 patients (24 female, 37 male) with MHD via US within the period from November 2005 to February 2009. After the presentation of a not clearly cystic liver lesion (n = 48), CEUS was performed and documented in addition to US. The underlying diagnoses were stem cell diseases (n = 31) and malignant lymphomas (n = 30). The detection of a lesion was documented in n = 17 patients with at this time point primary diagnosed haematological disease, n = 13 patients were in relapse and n = 31 in complete remission (CR). The diagnoses of the liver pathology were confirmed through sonographic follow-up studies and clinical courses (n = 22), CT/MRI (n = 18) and histology (n = 21).

RESULTS

In total 67 % of the cases were diagnosed as benign and 33 % as malignant liver lesions. Regarding the therapeutic state, the numbers of benign lesions differ from those of malignant lesions: primary diagnosis 53 vs. 47 %, relapse 69 vs. 31 %, CR 90 vs. 10 %. The frequency distributions of benign versus malignant lesions were 94 vs. 6 % in patients with stem cell diseases and 40 vs. 60 % in patients with malignant lymphomas. Regarding dignity assessment of focal liver lesions, CEUS showed a sensitivity of 90 vs. 45 % and specificity of 96 vs. 18 % (p < 0.0001) compared to US.

CONCLUSION

CEUS possesses a significant diagnostic value in the characterization of focal liver lesions and should be used in the context of staging procedures in patients with MHD.

Sesamoid complex disruption as a cause of hallux valgus: report of three cases

Hallux valgus is perhaps the most common forefoot deformity, usually related to genetic factors, gender and footwear habits. The current cases represent an unusual etiology of the syndrome due to sesamoid ligamentary damage and inter-sesamoid ligament rupture. One of the cases was treated surgically by excision of the non-united lateral sesamoid and reconstruction of the intermetatarsal ligament. Another one was treated by a Wilson-like osteotomy. The third one was conservatively treated by casting. In these cases the hallux valgus angle declined following treatment.

Comparison of Bivalirudin versus Bivalirudin plus glycoprotein IIb/IIIa inhibitor versus heparin plus glycoprotein IIb/IIIa inhibitor in patients with acute coronary syndromes having percutaneous intervention for narrowed saphenous vein aorto-coronary grafts (the ACUITY trial investigators)

Clinical outcomes in patients with acute coronary syndromes randomized in the Acute Catheterization and Urgent Intervention Triage Strategy (ACUITY) trial who underwent percutaneous coronary intervention (PCI) of saphenous vein grafts (SVGs) were examined. The ACUITY trial assessed the safety and efficacy of bivalirudin alone versus bivalirudin plus a glycoprotein (GP) IIb/IIIa inhibitor versus heparin plus a GP IIb/IIIa inhibitor in 13,819 patients with moderate- and high-risk acute coronary syndromes, 7,789 of whom underwent PCI. A total of 329 patients (4.2%) underwent PCI of SVGs in ACUITY. The primary end points at 30 days were composite ischemia or major adverse cardiac events (death, myocardial infarction, or unplanned target vessel revascularization), major bleeding (unrelated to coronary artery bypass grafting), and net adverse clinical events (composite ischemia or major bleeding). The rates of ischemic, bleeding, and net clinical end points were similar with bivalirudin monotherapy, bivalirudin plus a GP IIb/IIIa inhibitor, and heparin plus a GP IIb/IIIa inhibitor. Net adverse clinical outcome rates at 30 days were 22%, 26%, and 22% (p = 0.67), respectively, for the 3 groups. Major adverse cardiac event rates at 1 year were 37%, 37%, and 43% (p = 0.95), respectively. Minor bleeding unrelated to coronary artery bypass grafting at 30 days was significantly lower with bivalirudin alone compared with heparin plus a GP IIb/IIIa inhibitor (26% vs 38%, p = 0.05). In conclusion, bivalirudin is an effective anticoagulant in PCI of SVGs in acute coronary syndromes, with similar rates of major adverse cardiac events and net adverse cardiac events and lower minor bleeding complications in comparison with heparin plus a GP IIb/IIIa inhibitor or bivalirudin plus a GP IIb/IIIa inhibitor.

Beta cell function, insulin resistance and plasma adiponectin concentrations are predictors for the change of postprandial glucose in non-diabetic subjects at risk for type 2 diabetes

Insulin resistance, impaired insulin secretion, and low adiponectin levels have been shown to be predictors for type 2 diabetes. However, it is not yet clear whether these associations (1) are independent of changes in body weight, or (2) are valid for changes in glucose tolerance in the prediabetic state. Sixty-two non-diabetics (50 with normal glucose tolerance) aged 41 +/- 11 years, BMI 30.5 +/- 5.3 kg/m2 (mean +/- SD) were studied twice with a standard oral glucose tolerance test (oGTT, mean follow-up time 3.0 +/- 1.8 years (mean +/- SD) [range 0.5-6.5 years]). Insulin sensitivity and insulin secretion were estimated from oGTT using validated indices. Two-hour blood glucose during oGTT deteriorated over time (baseline 2 h glucose 6.32 +/- 0.21 VS. follow-up 2 h glucose 7.14 +/- 0.22 mM, p < 0.001) while the percentage body fat did not change (32.7 +/- 1.2 VS. 32.6 +/- 1.2%, p = 0.46). Follow-up 2 h blood glucose was predicted by adiponectin (p = 0.01), baseline insulin sensitivity (p = 0.02) and baseline insulin secretion relative to insulin sensitivity (p = 0.03) independent of sex, age, baseline 2 h blood glucose or change in percentage body fat. Our results suggest that low adiponectin levels, insulin resistance and low beta cell function predict the continuous deterioration of glucose tolerance in early prediabetic states, independent of changes in adiposity. Therefore, the early influence of these parameters should be the subject of future prevention programs to prevent deterioration of glucose tolerance.

Targeted deletion of integrin-linked kinase reveals a role in T-cell chemotaxis and survival

Integrin-linked kinase (ILK) is a serine/threonine kinase that is important in cell-matrix interactions and cell signaling. To examine the role of ILK in leukocyte trafficking and survival, we generated T cell-specific ILK knockouts by breeding ILK(flox/flox) mice to transgenic mice expressing Cre recombinase under control of the Lck proximal promoter. Thymic T cells from Lck-Cre(+)/ILK(flox/flox) mice had a marked reduction (>95%) in ILK protein levels. Thymic cellularity was comparable in 3- to 4-week-old mice, but a threefold diminution of thymic T cells became evident by 6 to 8 weeks of age in the T cell-specific ILK knockout mice due to increased cell death of double-positive (DP) T cells. Analysis of peripheral T cells by quantitative PCR and by breeding Lck-Cre(+)/ILK(flox/flox) mice to a YFP-transgenic reporter strain demonstrated an approximate 20-fold enrichment of ILK-competent cells, suggesting these cells have a competitive advantage in trafficking to and/or survival in peripheral lymphatic organs. We explored mechanisms related to altered cell trafficking and survival that might explain the decreases in thymic cellularity and enrichment for ILK-competent cells in the spleen and lymph nodes. We observed a >50% reduction in chemotaxis of ILK-deficient T cells to the chemokines CXCL12 (stromal cell-derived factor [SDF]-1alpha) and CCL19 (macrophage inflammatory protein [MIP]-3beta), as well as enhanced apoptosis of ILK-deficient cells upon stress. Signaling studies in ILK-deficient T cells demonstrated diminished phosphorylation of Akt on the activating phosphorylation site, Ser 473, and a concordant decrease in Akt kinase activity following stimulation with the chemokine SDF-1. Rac1 activation was also markedly diminished in ILK-deficient T cells following chemokine stimulation. These data extend the role of ILK to immune-cell trafficking and survival via modulation of Akt- and Rac-dependent substrates, and have implications for cell recruitment in both homeostatic and pathological processes.

Association of serum phosphate levels with glucose tolerance, insulin sensitivity and insulin secretion in non-diabetic subjects

BACKGROUND

Hypophosphatemia is associated with impaired glucose tolerance and insulin resistance in primary hyperparathyroidism. However, little is known about the association between serum phosphate and glucose metabolism in healthy subjects.

METHODS

We measured fasting serum phosphate levels (SP, normal range 2.6-4.5 mg/dl) and serum calcium (S-Ca, normal range 2.1-2.6 mmol/l) in 881 non-diabetic subjects (341 male/540 female, age: 38+/-1 years, body mass index 25.9+/-0.2 kg/m(2) (mean+/-standard error of the mean). An oral glucose tolerance test (OGTT) with determination of glucose and insulin every 30 min was performed in all subjects. Insulin secretion and insulin sensitivity (IS) were estimated from the OGTT using validated indices. Furthermore, we tested whether serum phosphate predicts glucose tolerance in 115 subjects during a lifestyle intervention program (LIP).

RESULTS

Serum phosphate was negatively correlated with 2-h blood glucose levels independent of age, gender and percent body fat (r=-0.13, P<0.0001). This association remained significant after additional adjustment for S-Ca, creatinine and parathyroid hormone. Serum phosphate was positively correlated with IS (r=0.10, P=0.0006), but not with insulin secretion. This was independent of age, gender, percent body fat, S-Ca and serum creatinine. In the subjects taking part in the LIP low serum phosphate levels at baseline were associated with higher postprandial glucose levels.

CONCLUSIONS

In non-diabetic subjects, low serum phosphate levels are associated with high 2-h blood glucose levels and reduced IS. Whether low serum phosphate levels are a cause or a consequence of low IS and impairment of glucose tolerance needs to be tested in further studies.

Metabolomic identification of novel biomarkers of myocardial ischemia

BACKGROUND

Recognition of myocardial ischemia is critical both for the diagnosis of coronary artery disease and the selection and evaluation of therapy. Recent advances in proteomic and metabolic profiling technologies may offer the possibility of identifying novel biomarkers and pathways activated in myocardial ischemia.

METHODS AND RESULTS

Blood samples were obtained before and after exercise stress testing from 36 patients, 18 of whom demonstrated inducible ischemia (cases) and 18 of whom did not (controls). Plasma was fractionated by liquid chromatography, and profiling of analytes was performed with a high-sensitivity electrospray triple-quadrupole mass spectrometer under selected reaction monitoring conditions. Lactic acid and metabolites involved in skeletal muscle AMP catabolism increased after exercise in both cases and controls. In contrast, there was significant discordant regulation of multiple metabolites that either increased or decreased in cases but remained unchanged in controls. Functional pathway trend analysis with the use of novel software revealed that 6 members of the citric acid pathway were among the 23 most changed metabolites in cases (adjusted P=0.04). Furthermore, changes in 6 metabolites, including citric acid, differentiated cases from controls with a high degree of accuracy (P<0.0001; cross-validated c-statistic=0.83).

CONCLUSIONS

We report the novel application of metabolomics to acute myocardial ischemia, in which we identified novel biomarkers of ischemia, and from pathway trend analysis, coordinate changes in groups of functionally related metabolites.

Angiogenesis inhibitors endostatin or TNP-470 reduce intimal neovascularization and plaque growth in apolipoprotein E-deficient mice

BACKGROUND

Neovascularization within the intima of human atherosclerotic lesions is well described, but its role in the progression of atherosclerosis is unknown. In this report, we first demonstrate that intimal vessels occur in advanced lesions of apolipoprotein E-deficient (apoE -/-) mice. To test the hypothesis that intimal vessels promote atherosclerosis, we investigated the effect of angiogenesis inhibitors on plaque growth in apoE -/- mice.

METHODS AND RESULTS

ApoE -/- mice were fed a 0.15% cholesterol diet. At age 20 weeks, mice were divided into 3 groups and treated for 16 weeks as follows: group 1, recombinant mouse endostatin, 20 mg. kg-1. d-1; group 2, fumagillin analogue TNP-470, 30 mg/kg every other day; and group 3, control animals that received a similar volume of buffer. Average cholesterol levels were similar in all groups. Plaque areas were quantified at the aortic origin. Median plaque area before treatment was 0.250 mm2 (range, 0.170 to 0.348; n=10). Median plaque areas were 0.321 (0.238 to 0.412; n=10), 0.402 (0.248 to 0.533; n=15), and 0.751 mm2 (0.503 to 0.838; n=12) for the endostatin, TNP-470, and control groups, respectively (P</=0.0001). Therefore, endostatin and TNP-470 inhibited plaque growth during the treatment period by 85% and 70%. Intimal smooth muscle cell contents of plaques from control and treated mice were similar.

CONCLUSIONS

Prolonged treatment with either angiogenesis inhibitor reduced plaque growth and intimal neovascularization in apoE -/- mice. Although the mechanism of plaque inhibition induced by these agents is not established, these results suggest that intimal neovascularization may promote plaque development.

Ikaros DNA-binding proteins direct formation of chromatin remodeling complexes in lymphocytes

The Ikaros gene family encodes zinc finger DNA-binding proteins essential for lineage determination and control of proliferation in the lymphoid system. Here, we report that, in the nucleus of a T cell, a major fraction of Ikaros and Aiolos proteins associate with the DNA-dependent ATPase Mi-2 and histone deacetylases, in a 2 MD complex. This Ikaros-NURD complex is active in chromatin remodeling and histone deacetylation. Upon T cell activation, Ikaros recruits Mi-2/HDAC to regions of heterochromatin. These studies reveal that Ikaros proteins are capable of targeting chromatin remodeling and deacetylation complexes in vivo. We propose that the restructuring of chromatin is a key aspect of Ikaros function in lymphocyte differentiation.

Homologous desensitization of ATP-stimulated mitogenesis: mechanism involves desensitization of arachidonic acid release and cAMP elevation but not the activation of protein kinase A

Prolonged incubation of quiescent 3T3, 3T6, and A431 cells with the P2Y purinoceptor agonists ATP, ADP, or AMPPNP reduced the mitogenic responses of target cells to a further challenge by these agonists, as measured by [3H]thymidine incorporation. The mitogenic desensitization was agonist-specific, for no effect was seen on DNA synthesis stimulated by epidermal growth factor, insulin, bombesin, 12-O-tetradecanoyl-phorbol-12 acetate (TPA), or adenosine. The desensitization was completely reversible, since after a 24 hr incubation in the absence of ATP, the cells responded fully to the mitogenic action of ATP. The presence of a low level of cycloheximide blocked recovery, suggesting that down-regulation of the P2Y receptor may have occurred during desensitization. In Swiss 3T3 cells, stimulation of DNA synthesis occurs predominantly by activation of arachidonic acid release, followed by its oxidation to prostaglandin E2 and stimulation of adenylyl cyclase. Interestingly, prolonged preincubation with ATP produced a similar degree of desensitization of DNA synthesis and of ATP-dependent arachidonic acid release and cAMP accumulation. Furthermore, this was true for both wild type cells and mutants with a defective cAMP-dependent protein kinase (PKA). We conclude that homologous desensitization is likely due to uncoupling of the P2Y purinoceptor from phospholipase A2, and this process does not require activation of protein kinase A.

[Occupational scleroderma due to organic solvent exposure]

Progressive systemic sclerosis (PSS; scleroderma) is a multisystem disease characterized by inflammation, fibrosis and degeneration of the integument, with similar changes and vascular lesions in the heart, lungs, kidneys, gastrointestinal tract and synovia. Its etiology is not clear. Several occupational exposures have been implicated as potential causes of PSS and scleroderma-like diseases. Among them are vinyl chloride monomer, silica dust, epoxy resin, and benzene and other solvents, aromatic and aliphatic, specifically chlorinated (trichloroethylene, perchloroethylene and trichloromethane). We present a patient whose illness was diagnosed as occupationally induced PSS. During 13 years of work renovating carburetors he was heavily exposed to trichloromethane. To the best of our knowledge this is the first reported case of PSS due to exposure to organic solvents in Israel; very few cases have been reported from abroad.

Functional results of operation in osteogenesis imperfecta: elongating and nonelongating rods

Gait capacity, operative intervention, and complications of operation were evaluated in 20 patients with osteogenesis imperfecta (OI). Thirty-two Bailey-Dubow (B-D) rods and 24 nonelongating rods were used. Postoperatively, gait capacity improved in eight patients, regressed in three, and remained unchanged in nine. No preoperative ambulator regressed to a nonambulatory status. The Sillence disease type was not a prognostic indicator of giat capacity. The complication rate was 72% for the B-D rod and 50% for the nonelongating rod, although the percentage requiring reoperation was similar for both types of nails. There was no difference in longevity between the two nails.

Bone marrow transplantation for malignant histiocytosis in childhood

This report describes a girl who was diagnosed with malignant histiocytosis at the age of 5 years. The disease was controlled initially with chemotherapy for 3 years and had then recurred with meningeal involvement on three occasions. Four years and 8 months from diagnosis, bone marrow transplantation (BMT) was undertaken from an HLA-identical and mixed lymphocyte culture (MLC) nonreactive brother after conditioning with VP-16-213 5 mg/kg/day X 2, cyclophosphamide 60 mg/kg/day X 2, and total body irradiation 200 rad twice daily to a total dose of 1000 rad delivered at 7 rad/minute. At the time of transplant, the disease was in remission. Currently, more than 48 months after the transplant, the child remains free of disease, with a normally functioning donor marrow and with no evidence of graft versus host disease. This is the first recorded case of BMT in the treatment of malignant histiocytosis. The outcome in this patient in late-stage disease suggests that BMT could be considered early in management as definitive therapy.

Chromosomal assignment of two murine genes controlling susceptibility to spleen focus formation by Rauscher leukemia virus

Two murine genes affecting susceptibility to spleen focus formation by RLV were assigned to chromosomes. The gene Rv-2, which controls susceptibility to spleen focus formation, was assigned to chromosome 9, and closely linked to the Fv-2 gene, by using the two congenic strains B10.C(47N)/Sn and B6.C-H-7b/By. These congenic strains, which were previously shown to carry the BALB/cJ allele for susceptibility to FLV on chromosome 9, were also susceptible to RLV, as determined by number of foci on the spleens of infected mice. A second gene which contributes to the susceptibility to spleen focus formation by RLV was assigned to the X chromosome because hemizygous male offspring of crosses between resistant-strain females and susceptible-strain males (C57BL/6J X CBA/Lac) showed significantly lower numbers of foci/spleen than the female littermates and than the offsprings, males and females, of the reciprocal cross (CBA/Lac X C57BL/6J). We suggest this gene be called Rv-3.

The release of 3-methyladenine from nucleosomal DNA by a 3-methyladenine DNA glycosylase

Nucleosomes from chicken erythrocytes, with DNA containing an average of 144 base pairs, were alkylated with [3H]methylnitrosourea. The level of alkylation of the nucleosomal DNA was 48% of that of free DNA. The histones had approximately one tenth the radioactivity of the DNA. There was no statistically significant difference between alkylation of nucleosome bases in the major vs. minor groove. When the first 50 residues of the alkylated nucleosomal DNA were examined on sequencing gels, the 7-methylguanine and 3-methyladenine (3-MeA) residues were distributed randomly. The 3-MeA DNA glycosylase I of E. coli was used to measure the release of 3-MeA from nucleosomal DNA. Incubation at 37 degrees C resulted in a release which reached a plateau of approximately 33% of the 3-MeA groups of the nucleosomal DNA. A partially purified 3-MeA DNA glycosylase from rat liver gave similar results. The limited enzymatic release is most likely due to steric hindrance of the enzyme by the DNA-histone interactions on the surface of the core particle. An alteration of nucleosomal conformation has been suggested as an explanation for repair of nucleosomal DNA. Two model systems have been examined. The addition of ethidium bromide to alkylated nucleosomes increased the enzymatic release of 3-MeA to approximately 75% and altered the electron microscopic appearance. The chemical alkylation of nucleosomes also increased the enzymatic release of 3-MeA as well as decreased the sedimentation coefficient. All of these experiments indicate a limited availability of 3-MeA residues to the glycosylase and suggest that some conformational change must occur in vivo for complete repair.

Retroviral antigens on gs- chf- leukocytes

It has recently been suggested that the endogenous retroviruses present in many different species might be involved during stimulation of the immune system of their hosts. We have now studied the expression of two avian retroviral antigens p27 and gp85 in chicken lymphoid cells by indirect immunofluorescence (IIF) and by complement-dependent microcytotoxicity (CDM). We have now found that these viral antigens are expressed in peripheral blood leukocytes of adults and embryos and in splenic and bursal lymphocytes of Spafas gs- chf- chickens but they are not expressed in fibroblasts cultured from the feather follicles of the same individual adult birds nor in fibroblasts cultured from embryos of the same flock. The differential expression of viral antigens in leukocytes may be related to a specific property or function of these cells.

Evidence for intracistronic complementation of the product of the influenza virus gene Ptra (P3 of fowl plague virus)

The ts lesion of the fowl plague virus (FPV) mutants ts 18 and ts 236 has been located in RNA segment 2 (Ptra gene, corresponding to P3). After double-infection with these mutants and ts 90 or ts 93, which also carry a ts lesion in segment 2, plaques were formed at the non-permissive temperature (40 degrees C). These plaques cannot be passaged at 40 degrees C and exhibit a morphology which differs from those formed by the wild-type virus. The yield of infectious particles after double-infection shows a non-linear correlation between the plaque number and dilution, indicating that at least two particles are needed for infection of a cell. All experimental evidence points to an intracistronic complementation within the P3 protein.

Purification and primary structure of two neuroactive peptides that cause bag cell afterdischarge and egg-laying in Aplysia

Two neuroactive peptides, A and B, have been isolated from the atrial gland in the reproductive tract of Aplysia. Each of the two peptides is able to induce egg-laying behavior in recipient animals. In vitro recordings from the abdominal ganglion show that both peptides also trigger longlasting discharges in the bag cell neurons at concentrations around 0.1 muM. The peptides were purified by a combination of ammonium sulfate precipitation, agarose gel filtration, and cation exchange chromatography. Each peptide has 34 amino acid residues. Microsequencing together with carboxypeptidase Y degradation and analysis of tryptic peptides revealed the following sequence for peptide A: H-Ala-Val-Lys-Leu-Ser-Ser-Asp-Gly-Asn-Tyr-Pro-Phe-Asp-Leu-Ser-Lys-Glu-Asp-Gly -Ala-Gln-Pro-Tyr-Phe-Met-Thr-Pro-Arg-Leu-Arg-Phe-Tyr-Pro-Ile. Peptide B differs from A in only four positions. The first nine residues of B are: Ala-Val-Lys-Ser-Ser-Ser-Tyr-Glu-Lys-, whereas residues 10-34 of B are identical to those of A. The calculated M(r) of A is 3924 and that of B is 4032. The pI of peptide A as determined by isoelectric focusing in polyacrylamide gels is 7.9-8.1 and that of peptide B is 9.0-9.2. It is estimated that each atrial gland contains at least 150 mug of peptide A and 50 mug of B. Neither peptide resembles the egg-laying hormone isolated from bag cell neurons. It is postulated that the atrial gland peptides are released during copulation, and then by interacting with neuronal receptors in the head ganglia and pleuroabdominal connectives they cause the bag cells to afterdischarge, thereby releasing egg-laying hormone.

Purification and primary structure of the neuropeptide egg-laying hormone of Aplysia californica

Egg-laying hormone (ELH), a neuropeptide synthesized by the bag cell neurons, induces egg laying and its correlated behavior in Aplysia californica. In the present study, ELH has been purified to homogeneity and its primary structure has been determined. We find this molecule to have 36 amino acid residues with a M(r) of 4385 and a calculated isoelectric point of 9.7. Direct microsequence analysis revealed a single amino acid sequence that is in agreement with the amino acid composition determined after acid hydrolysis of ELH: H-Ile-Ser-Ile-Asn-Gln-Asp-Leu-Lys-Ala-Ile-Thr-Asp-Met-Leu-Leu-Thr-Glu-Gln- Ile-Arg-Glu-Arg-Gln-Arg-Tyr-Leu-Ala-Asp-Leu-Arg-Gln-Arg-Leu-Leu-Glu-Lys-OH. Enzyme data indicate that the COOH-terminal lysine may be modified but its exact nature remains to be determined. There is no similarity between the amino acid sequence of ELH and that of presently known vertebrate neuropeptides. The two-step purification procedure, starting with a homogenate of bag cell clusters, consisted of cation exchange chromatography on SP C25 (Sephadex) followed by gel filtration on Bio-Gel P-6. Our purification results in a 100-fold enrichment of ELH from bag cell homogenates and a 36% recovery of purified radiolabeled marker ELH. Analysis of purified ELH radiolabeled with [(35)S]methionine or [(3)H]leucine on isoelectric focusing gels and on 8 M urea/sodium dodecyl sulfate gels showed only a single peak containing 90% of the radiolabel. Radiolabeled ELH migrated with a pI of 9.0-9.2 and an apparent M(r) of 3500-5700. ELH retained egg-laying bioactivity when eluted from this segment of the gel. We find that 2.5 nmol of pure ELH consistently induces egg laying at 20 degrees C.

The vitelline envelope of eggs from the giant keyhole limpet Megathura crenulata. I. Chemical composition and structural studies

The egg vitelline envelope of the marine invertebrate Megathura crenulata is a glycoprotein composed of 37.3 mol % protein and 62.7 mol % carbohydrate. Of the total amino acid content, 61 mol % consists of a single amino acid, threonine. The carbohydrate content includes galactosamine, galactose, and fucose. The molar ratio of threonine to galactosamine is about 1:1. Most of the threonine residues are linked to galactosamine residues via O-glycosidic bonds. A single peptide that was purified following alkaline borohydride treatment of the vitelline envelope had the structure: Abu-Pro-Abu-(Abu6, Pro1, Thr1), where Abu is 2-aminobutyric acid. Several sugar residues have been isolated following the alkaline hydrolysis of the vitelline envelope that include an octasaccharide Gal4Fu4, an hexasaccharide Gal3Fu3, a trisaccharide Gal3, fucose, and galactose. It is proposed that the vitelline envelope of Megathura crenulata eggs is composed of polypeptide chains built to a large extent of closely spaced threonine residues. Almost every threonine residue is linked to a saccharide moiety.

The vitelline envelope of eggs from the giant keyhole limpet Megathura crenulata. II. Products formed by lysis with sperm enzymes and dithiothreitol

The egg vitelline envelope of the marine invertebrate, Megathura crenulata, was lyzed either by sperm lysins A, B, C or by dithiothreitol. In each case the lysis mixture consisted of two major fractions, I and II, that could be separated by hydroxylapatite chromatography and had different electrophoretic mobilities on cellulose acetate strips. The amino acid, amino sugar, and neutral sugar compositions of fractions I and II were similar and resembled that of the intact vitelline envelope. Fractions I and II of each lysis mixture emerged in the exclusion volume of a Sepharose 6B column. A vitelline envelope fragment enzymatically formed by lysin was further degraded by dithiothreitol to form smaller fragments. A model of the vitelline envelope of the Megathura crenulata egg is suggested whereby the envelope is composed of polypeptide chains cross-linked by disulfide bonds and built to a large extent of closely spaced threonine residues. Most of the threonine residues are linked to carbohydrate units. Dithiothreitol dissolves the envelope by reducing disulfide bonds, whereas lysins most likely dissolve the envelope by degrading polypeptide chains.