Insulin resistance and reduced cardiac autonomic function in older adults: the Atherosclerosis Risk in Communities study

Background: Prior studies have shown insulin resistance is associated with reduced cardiac autonomic function measured at rest, but few studies have determined whether insulin resistance is associated with reduced cardiac autonomic function measured during daily activities. Methods: We examined older adults without diabetes with 48-h ambulatory electrocardiography (n = 759) in an ancillary study of the Atherosclerosis Risk in Communities Study. Insulin resistance, the exposure, was defined by quartiles for three indexes: 1) the homeostatic model assessment of insulin resistance (HOMA-IR), 2) the triglyceride and glucose index (TyG), and 3) the triglyceride to high-density lipoprotein cholesterol ratio (TG/HDL-C). Low heart rate variability, the outcome, was defined by <25th percentile for four measures: 1) standard deviation of normal-to-normal R-R intervals (SDNN), a measure of total variability; 2) root mean square of successive differences in normal-to-normal R-R intervals (RMSSD), a measure of vagal activity; 3) low frequency spectral component (LF), a measure of sympathetic and vagal activity; and 4) high frequency spectral component (HF), a measure of vagal activity. Logistic regression was used to estimate odds ratios (OR) and 95% confidence intervals weighted for sampling/non-response, adjusted for age at ancillary visit, sex, and race/study-site. Insulin resistance quartiles 4, 3, and 2 were compared to quartile 1; high indexes refer to quartile 4 versus quartile 1. Results: The average age was 78 years, 66% (n = 497) were women, and 58% (n = 438) were African American. Estimates of association were not robust at all levels of HOMA-IR, TyG, and TG/HDL-C, but suggest that high indexes were associated consistently with indicators of vagal activity. High HOMA-IR, high TyG, and high TG/HDL-C were consistently associated with low RMSSD (OR: 1.68 (1.00, 2.81), OR: 2.03 (1.21, 3.39), and OR: 1.73 (1.01, 2.91), respectively). High HOMA-IR, high TyG, and high TG/HDL-C were consistently associated with low HF (OR: 1.90 (1.14, 3.18), OR: 1.98 (1.21, 3.25), and OR: 1.76 (1.07, 2.90), respectively). Conclusions: In older adults without diabetes, insulin resistance was associated with reduced cardiac autonomic function - specifically and consistently for indicators of vagal activity - measured during daily activities. Primary prevention of insulin resistance may reduce the related risk of cardiac autonomic dysfunction

Repeatability of Central and Peripheral Pulse Wave Velocity Measures: The Atherosclerosis Risk in Communities (ARIC) Study

Arterial stiffness measures are emerging tools for risk assessment and stratification for hypertension and cardiovascular disease (CVD). Carotid-femoral pulse wave velocity (cfPWV) is an established measure of central arterial stiffness. Other measures of PWV include femoral-ankle (faPWV), a measure of peripheral stiffness, and brachial-ankle PWV (baPWV), a composite measure of central and peripheral stiffness. Repeatability of central, peripheral, and composite PWV measures has not been adequately examined or compared

Hyperk\"ahler torsion structures invariant by nilpotent Lie groups

We study HKT structures on nilpotent Lie groups and on associated nilmanifolds. We exhibit three weak HKT structures on $\R^8$ which are homogeneous with respect to extensions of Heisenberg type Lie groups. The corresponding hypercomplex structures are of a special kind, called abelian. We prove that on any 2-step nilpotent Lie group all invariant HKT structures arise from abelian hypercomplex structures. Furthermore, we use a correspondence between abelian hypercomplex structures and subspaces of ${\frak sp}(n)$ to produce continuous families of compact and noncompact of manifolds carrying non isometric HKT structures. Finally, geometrical properties of invariant HKT structures on 2-step nilpotent Lie groups are obtained.Comment: LateX, 12 page

Prediabetes and Diabetes Are Associated With Arterial Stiffness in Older Adults: The ARIC Study

To determine whether prediabetes and diabetes in older adults are associated with arterial stiffness measured in central and peripheral arteries and to examine characteristics that modify these associations

More questions than answers to the diagnosis and management of cauda equina syndrome-Authors' reply

No abstract available

Impact of COVID-19 pandemic on surgical neuro-oncology multi-disciplinary team decision making: a national survey (COVID-CNSMDT Study).

OBJECTIVES: Pressures on healthcare systems due to COVID-19 has impacted patients without COVID-19 with surgery disproportionally affected. This study aims to understand the impact on the initial management of patients with brain tumours by measuring changes to normal multidisciplinary team (MDT) decision making. DESIGN: A prospective survey performed in UK neurosurgical units performed from 23 March 2020 until 24 April 2020. SETTING: Regional neurosurgical units outside London (as the pandemic was more advanced at time of study). PARTICIPANTS: Representatives from all units were invited to collect data on new patients discussed at their MDT meetings during the study period. Each unit decided if management decision for each patient had changed due to COVID-19. PRIMARY AND SECONDARY OUTCOME MEASURES: Primary outcome measures included number of patients where the decision to undergo surgery changed compared with standard management usually offered by that MDT. Secondary outcome measures included changes in surgical extent, numbers referred to MDT, number of patients denied surgery not receiving any treatment and reasons for any variation across the UK. RESULTS: 18 units (75%) provided information from 80 MDT meetings that discussed 1221 patients. 10.7% of patients had their management changed-the majority (68%) did not undergo surgery and more than half of this group not undergoing surgery had no active treatment. There was marked variation across the UK (0%-28% change in management). Units that did not change management could maintain capacity with dedicated oncology lists. Low volume units were less affected. CONCLUSION: COVID-19 has had an impact on patients requiring surgery for malignant brain tumours, with patients receiving different treatments-most commonly not receiving surgery or any treatment at all. The variations show dedicated cancer operating lists may mitigate these pressures. STUDY REGISTRATION: This study was registered with the Royal College of Surgeons of England's COVID-19 Research Group (https://www.rcseng.ac.uk/coronavirus/rcs-covid-research-group/)

Scanning tunneling microscopy and atomic force microscopy in the characterization of activated graphite electrodes

Sir: To date there have been many methods described to activate carbon electrodes, including electrochemical treatment (1-1 7), laser irradiation (18-21), radio-frequency (RF) plasma (22), and heat treatment (23-26). These methods were developed empirically, and only now is an understanding of parameters controlling surface activity beginning to emerge (20,27). Electrochemical treatment and laser irradiation are particularly attractive treatments because they are relatively inexpensive, are quick, and can be performed without removing the electrode from solution. Activation, common to these procedures, may be attributable to an increase in the exposed edge plane density, which has been associated with faster kinetics (14,20). Copper deposition in conjunction with scanning electron microscopy (SEM) has shown an increase in the density of localized defects on active surfaces (15); an increase in surface activity is associated with an increase in the density of the localized defects (15). Scanning tunneling microscopy (STM), phase detection microscopy, and SEM have also been used to study the effects of electrochemical treatment of highly oriented pyrolytic graphite (HOPG) (13) and glassy carbon (GC) (16,17). These studies have suggested an increase in surface roughness consistent with an increase in the density of exposed edge planes

Feasibility study of an internally cooled bipolar applicator for RF coagulation of hepatic tissue: Experimental and computational study

Purpose: To study the capacity of an internally cooled radiofrequency (RF) bipolar applicator to create sufficiently deep thermal lesions in hepatic tissue. Materials and methods: Three complementary methodologies were employed to check the electrical and thermal behaviour of the applicator under test. The experimental studies were based on excised bovine (ex vivo study) and porcine liver (in vivo study) and the theoretical models were solved by means of the finite element method (FEM). Results: Experimental and computational results showed good agreement in terms of impedance progress and lesion depth (4 and 4.5 mm respectively for ex vivo conditions, and approximately 7 and 9 mm respectively for in vivo conditions), although the lesion widths were overestimated by the computer simulations. This could have been due to the method used to assess the thermal lesions; the experimental lesions were assessed by the white coagulation zone, whereas the tissue damage function was used to assess the computational lesions. Conclusions: The experimental results suggest that this applicator could create in vivo lesions to a depth of around 7mm. It was also observed that the thermal lesion is mainly confined to the area between both electrodes, which would allow lesion width to be controlled by selecting a specific applicator design. The comparison between the experimental and computational results suggests that the theoretical model could be usefully applied in further studies of the performance of this device. © 2012 Informa UK Ltd All rights reserved.This work received financial support from the Spanish Plan Nacional de I+D+I del Ministerio de Ciencia e Innovacion TEC2011-27133-C02-(01 and 02), from Universitat Politecnica de Valencia (INNOVA11-01-5502; and PAID-06-11 Ref. 1988). A. Gonzalez-Suarez is the recipient of grant VaLi+D (ACIF/2011/194) from the Generalitat Valenciana. The proof-reading of this paper was funded by the Universitat Politecnica de Valencia, Spain. The authors alone are responsible for the content and writing of the paper.González Suárez, A.; Trujillo Guillen, M.; Burdío Pinilla, F.; Andaluz Martínez, AM.; Berjano Zanón, E. (2012). Feasibility study of an internally cooled bipolar applicator for RF coagulation of hepatic tissue: Experimental and computational study. International Journal of Hyperthermia. 28(7):663-673. https://doi.org/10.3109/02656736.2012.716900S663673287Topp, S. A., McClurken, M., Lipson, D., Upadhya, G. A., Ritter, J. H., Linehan, D., & Strasberg, S. M. (2004). Saline-Linked Surface Radiofrequency Ablation. Annals of Surgery, 239(4), 518-527. doi:10.1097/01.sla.0000118927.83650.a4Gnerlich, J. L., Ritter, J. H., Linehan, D. C., Hawkins, W. G., & Strasberg, S. M. (2009). Saline-Linked Surface Radiofrequency Ablation. Annals of Surgery, 250(1), 96-102. doi:10.1097/sla.0b013e3181ae91afSakamoto, Y., Yamamoto, J., Kokudo, N., Seki, M., Kosuge, T., Yamaguchi, T., … Makuuchi, M. (2004). Bloodless liver resection using the Monopolar Floating Ball plus Ligasure diathermy: Preliminary results of 16 liver resections. World Journal of Surgery, 28(2), 166-172. doi:10.1007/s00268-003-7167-5Poon, R. T., Fan, S. T., & Wong, J. (2005). Liver resection using a saline-linked radiofrequency dissecting sealer for transection of the liver. Journal of the American College of Surgeons, 200(2), 308-313. doi:10.1016/j.jamcollsurg.2004.10.008EVERETT IV, T. H., LEE, K. W., WILSON, E. E., GUERRA, J. M., VAROSY, P. D., & OLGIN, J. E. (2008). Safety Profiles and Lesion Size of Different Radiofrequency Ablation Technologies: A Comparison of Large Tip, Open and Closed Irrigation Catheters. Journal of Cardiovascular Electrophysiology, 20(3), 325-335. doi:10.1111/j.1540-8167.2008.01305.xYokoyama, K., Nakagawa, H., Wittkampf, F. H. M., Pitha, J. V., Lazzara, R., & Jackman, W. M. (2006). Comparison of Electrode Cooling Between Internal and Open Irrigation in Radiofrequency Ablation Lesion Depth and Incidence of Thrombus and Steam Pop. Circulation, 113(1), 11-19. doi:10.1161/circulationaha.105.540062Demazumder, D., Mirotznik, M. S., & Schwartzman, D. (2001). Journal of Interventional Cardiac Electrophysiology, 5(4), 391-400. doi:10.1023/a:1013241927388Cooper, J. M., Sapp, J. L., Tedrow, U., Pellegrini, C. P., Robinson, D., Epstein, L. M., & Stevenson, W. G. (2004). Ablation with an internally irrigated radiofrequency catheter: Learning how to avoid steam pops. Heart Rhythm, 1(3), 329-333. doi:10.1016/j.hrthm.2004.04.019Burdío, F., Grande, L., Berjano, E., Martinez-Serrano, M., Poves, I., Burdío, J. M., … Güemes, A. (2010). A new single-instrument technique for parenchyma division and hemostasis in liver resection: a clinical feasibility study. The American Journal of Surgery, 200(6), e75-e80. doi:10.1016/j.amjsurg.2010.02.020Ríos, J. S., Zalabardo, J. M. S., Burdio, F., Berjano, E., Moros, M., Gonzalez, A., … Güemes, A. (2011). Single Instrument for Hemostatic Control in Laparoscopic Partial Nephrectomy in a Porcine Model Without Renal Vascular Clamping. Journal of Endourology, 25(6), 1005-1011. doi:10.1089/end.2010.0557Dorcaratto, D., Burdío, F., Fondevila, D., Andaluz, A., Poves, I., Martinez, M. A., … Grande, L. (2012). Laparoscopic Distal Pancreatectomy: Feasibility Study of Radiofrequency-Assisted Transection in a Porcine Model. Journal of Laparoendoscopic & Advanced Surgical Techniques, 22(3), 242-248. doi:10.1089/lap.2011.0417Zeh, A., Messer, J., Davis, J., Vasarhelyi, A., & Wohlrab, D. (2010). The Aquamantys System—An Alternative To Reduce Blood Loss in Primary Total Hip Arthroplasty? The Journal of Arthroplasty, 25(7), 1072-1077. doi:10.1016/j.arth.2009.10.008Sprunger, J., & Herrell, S. D. (2005). Partial Laparoscopic Nephrectomy Using Monopolar Saline-Coupled Radiofrequency Device: Animal Model and Tissue Effect Characterization. Journal of Endourology, 19(4), 513-519. doi:10.1089/end.2005.19.513Voeller, R. K., Zierer, A., Lall, S. C., Sakamoto, S., Schuessler, R. B., & Damiano, R. J. (2010). Efficacy of a novel bipolar radiofrequency ablation device on the beating heart for atrial fibrillation ablation: A long-term porcine study. The Journal of Thoracic and Cardiovascular Surgery, 140(1), 203-208. doi:10.1016/j.jtcvs.2009.06.034Pai, M., Spalding, D., Jiao, L., & Habib, N. (2012). Use of Bipolar Radiofrequency in Parenchymal Transection of the Liver, Pancreas and Kidney. Digestive Surgery, 29(1), 43-47. doi:10.1159/000335732Berjano, E. J. (2006). BioMedical Engineering OnLine, 5(1), 24. doi:10.1186/1475-925x-5-24Tungjitkusolmun, S., Staelin, S. T., Haemmerich, D., Jang-Zern Tsai, Hong Cao, Webster, J. G., … Vorperian, V. R. (2002). Three-dimensional finite-element analyses for radio-frequency hepatic tumor ablation. IEEE Transactions on Biomedical Engineering, 49(1), 3-9. doi:10.1109/10.972834Doss, J. D. (1982). Calculation of electric fields in conductive media. Medical Physics, 9(4), 566-573. doi:10.1118/1.595107Abraham, J. P., & Sparrow, E. M. (2007). A thermal-ablation bioheat model including liquid-to-vapor phase change, pressure- and necrosis-dependent perfusion, and moisture-dependent properties. International Journal of Heat and Mass Transfer, 50(13-14), 2537-2544. doi:10.1016/j.ijheatmasstransfer.2006.11.045Jo, B., & Aksan, A. (2010). Prediction of the extent of thermal damage in the cornea during conductive keratoplasty. Journal of Thermal Biology, 35(4), 167-174. doi:10.1016/j.jtherbio.2010.02.004Pearce, J., Panescu, D., & Thomsen, S. (2005). Simulation of diopter changes in radio frequency conductive keratoplasty in the cornea. Modelling in Medicine and Biology VI. doi:10.2495/bio050451Yang, D., Converse, M. C., Mahvi, D. M., & Webster, J. G. (2007). Expanding the Bioheat Equation to Include Tissue Internal Water Evaporation During Heating. IEEE Transactions on Biomedical Engineering, 54(8), 1382-1388. doi:10.1109/tbme.2007.890740Zhao, G., Zhang, H.-F., Guo, X.-J., Luo, D.-W., & Gao, D.-Y. (2007). Effect of blood flow and metabolism on multidimensional heat transfer during cryosurgery. Medical Engineering & Physics, 29(2), 205-215. doi:10.1016/j.medengphy.2006.03.005Pätz T, Körger T, Preusser T, Simulation of radiofrequency ablation including water evaporation. In: IFMBE Proceedings of the World Congress on Medical Physics and Biomedical Engineering 25/IV, 2009, 1287–1290Berjano, E. J., Burdío, F., Navarro, A. C., Burdío, J. M., Güemes, A., Aldana, O., … Gregorio, M. A. de. (2006). Improved perfusion system for bipolar radiofrequency ablation of liver: preliminary findings from a computer modeling study. Physiological Measurement, 27(10), N55-N66. doi:10.1088/0967-3334/27/10/n03Burdío, F., Berjano, E. J., Navarro, A., Burdío, J. M., Grande, L., Gonzalez, A., … Lequerica, J. L. (2009). Research and development of a new RF-assisted device for bloodless rapid transection of the liver: Computational modeling and in vivo experiments. BioMedical Engineering OnLine, 8(1), 6. doi:10.1186/1475-925x-8-6Chang, I. A., & Nguyen, U. D. (2004). BioMedical Engineering OnLine, 3(1), 27. doi:10.1186/1475-925x-3-27Beop-Min Kim, Jacques, S. L., Rastegar, S., Thomsen, S., & Motamedi, M. (1996). Nonlinear finite-element analysis of the role of dynamic changes in blood perfusion and optical properties in laser coagulation of tissue. IEEE Journal of Selected Topics in Quantum Electronics, 2(4), 922-933. doi:10.1109/2944.577317Panescu, D., Whayne, J. G., Fleischman, S. D., Mirotznik, M. S., Swanson, D. K., & Webster, J. G. (1995). Three-dimensional finite element analysis of current density and temperature distributions during radio-frequency ablation. IEEE Transactions on Biomedical Engineering, 42(9), 879-890. doi:10.1109/10.412649González-Suárez A, Alba J, Trujillo M, Berjano E, Experimental and theoretical study of an internally cooled bipolar electrode for RF coagulation of biological tissues. Conf Proc IEEE Eng Med Biol Soc 2011;6878–6881Rosenberg, A. G. (2007). Reducing Blood Loss in Total Joint Surgery With a Saline-Coupled Bipolar Sealing Technology. The Journal of Arthroplasty, 22(4), 82-85. doi:10.1016/j.arth.2007.02.018PETERSEN, H. H., ROMAN-GONZALEZ, J., JOHNSON, S. B., HASTRUP SVENDSEN, J., HAUNSO, S., & PACKER, D. L. (2004). Mechanisms for Enlarging Lesion Size During Irrigated Tip Radiofrequency Ablation:. Is There a Virtual Electrode Effect? Journal of Interventional Cardiology, 17(3), 171-177. doi:10.1111/j.1540-8183.2004.09879.

Enhanced Platelet Activation Mediates the Accelerated Angiogenic Switch in Mice Lacking Histidine-Rich Glycoprotein

BACKGROUND: The heparin-binding plasma protein histidine-rich glycoprotein (HRG; alternatively, HRGP/HPRG) can suppress tumor angiogenesis and growth in vitro and in vivo. Mice lacking the HRG gene are viable and fertile, but have an enhanced coagulation resulting in decreased bleeding times. In addition, the angiogenic switch is significantly enhanced in HRG-deficient mice. METHODOLOGY/PRINCIPAL FINDINGS: To address whether HRG deficiency affects tumor development, we have crossed HRG knockout mice with the RIP1-Tag2 mouse, a well established orthotopic model of multistage carcinogenesis. RIP1-Tag2 HRG(-/-) mice display significantly larger tumor volume compared to their RIP1-Tag2 HRG(+/+) littermates, supporting a role for HRG as an endogenous regulator of tumor growth. In the present study we also demonstrate that platelet activation is increased in mice lacking HRG. To address whether this elevated platelet activation contributes to the increased pathological angiogenesis in HRG-deficient mice, they were rendered thrombocytopenic before the onset of the angiogenic switch by injection of the anti-platelet antibody GP1bα. Interestingly, this treatment suppressed the increase in angiogenic neoplasias seen in HRG knockout mice. However, if GP1bα treatment was initiated at a later stage, after the onset of the angiogenic switch, no suppression of tumor growth was detected in HRG-deficient mice. CONCLUSIONS: Our data show that increased platelet activation mediates the accelerated angiogenic switch in HRG-deficient mice. Moreover, we conclude that platelets play a crucial role in the early stages of tumor development but are of less significance for tumor growth once angiogenesis has been initiated