Mammalian rod terminal: Architecture of a binary synapse

AbstractThe mammalian rod synapse transmits a binary signal (one photon or none) using tonic, rapid exocytosis. We constructed a quantitative, physical model of the synapse. Presynaptically, a single, linear active zone provides docking sites for ∼130 vesicles, and a “ribbon” anchored to the active zone provides a depot for ∼640 vesicles. Postsynaptically, 4 processes invaginate the terminal: 2 (known to have low affinity glutamate receptors) lie near the active zone (16 nm), and 2 (known to have high affinity glutamate receptors) lie at a distance (130–640 nm). The presynaptic structure seems designed to minimize fluctuations in tonic rate owing to empty docking sites, whereas the postsynaptic geometry may permit 1 vesicle to evoke an all-or-none response at all 4 postsynaptic processes

Predictors of Employee Involvement in a Worksite Health Promotion Program

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/67001/2/10.1177_109019819001700404.pd

Generalized Analysis of Stability and Numerical Dispersion in the Discrete-Convolution FDTD Method

Abstract-

In vitro calibration of a system for measurement of in vivo convective heat transfer coefficient in animals

BACKGROUND: We need a sensor to measure the convective heat transfer coefficient during ablation of the heart or liver. METHODS: We built a minimally invasive instrument to measure the in vivo convective heat transfer coefficient, h in animals, using a Wheatstone-bridge circuit, similar to a hot-wire anemometer circuit. One arm is connected to a steerable catheter sensor whose tip is a 1.9 mm × 3.2 mm thin film resistive temperature detector (RTD) sensor. We used a circulation system to simulate different flow rates at 39°C for in vitro experiments using distilled water, tap water and saline. We heated the sensor approximately 5°C above the fluid temperature. We measured the power consumed by the sensor and the resistance of the sensor during the experiments and analyzed these data to determine the value of the convective heat transfer coefficient at various flow rates. RESULTS: From 0 to 5 L/min, experimental values of h in W/(m(2)·K) were for distilled water 5100 to 13000, for tap water 5500 to 12300, and for saline 5400 to 13600. Theoretical values were 1900 to 10700. CONCLUSION: We believe this system is the smallest, most accurate method of minimally invasive measurement of in vivo h in animals and provides the least disturbance of flow

‘Fractional Recovery’ Analysis of a Presynaptic Synaptotagmin 1-Anchored Endocytic Protein Complex

BACKGROUND: The integral synaptic vesicle protein and putative calcium sensor, synaptotagmin 1 (STG), has also been implicated in synaptic vesicle (SV) recovery. However, proteins with which STG interacts during SV endocytosis remain poorly understood. We have isolated an STG-associated endocytic complex (SAE) from presynaptic nerve terminals and have used a novel fractional recovery (FR) assay based on electrostatic dissociation to identify SAE components and map the complex structure. The location of SAE in the presynaptic terminal was determined by high-resolution quantitative immunocytochemistry at the chick ciliary ganglion giant calyx-type synapse. METHODOLOGY/PRINCIPLE FINDINGS: The first step in FR analysis was to immunoprecipitate (IP) the complex with an antibody against one protein component (the IP-protein). The immobilized complex was then exposed to a high salt (1150 mM) stress-test that caused shedding of co-immunoprecipitated proteins (co-IP-proteins). A Fractional Recovery ratio (FR: recovery after high salt/recovery with control salt as assayed by Western blot) was calculated for each co-IP-protein. These FR values reflect complex structure since an easily dissociated protein, with a low FR value, cannot be intermediary between the IP-protein and a salt-resistant protein. The structure of the complex was mapped and a blueprint generated with a pair of FR analyses generated using two different IP-proteins. The blueprint of SAE contains an AP180/X/STG/stonin 2/intersectin/epsin core (X is unknown and epsin is hypothesized), and an AP2 adaptor, H-/L-clathrin coat and dynamin scission protein perimeter. Quantitative immunocytochemistry (ICA/ICQ method) at an isolated calyx-type presynaptic terminal indicates that this complex is associated with STG at the presynaptic transmitter release face but not with STG on intracellular synaptic vesicles. CONCLUSIONS/SIGNIFICANCE: We hypothesize that the SAE serves as a recognition site and also as a seed complex for clathrin-mediated synaptic vesicle recovery. The combination of FR analysis with quantitative immunocytochemistry provides a novel and effective strategy for the identification and characterization of biologically-relevant multi-molecular complexes

Ring electrode for radio-frequency heating of the cornea: modelling and in vitro experiments

[EN] Radio-frequency thermokeratoplasty (RF-TKP) is a technique used to reshape the cornea curvature by means of thermal lesions using radio-frequency currents. This curvature change allows refractive disorders such as hyperopia to be corrected. A new electrode with ring geometry is proposed for RF-TKP. It was designed to create a single thermal lesion with a full-circle shape. Finite element models were developed, and the temperature distributions in the cornea were analysed for different ring electrode characteristics. The computer results indicated that the maximum temperature in the cornea was located in the vicinity of the ring electrode outer perimeter, and that the lesions had a semi-torus shape. The results also indicated that the electrode thickness, electrode radius and electrode thermal conductivity had a significant influence on the temperature distributions. In addition, in vitro experiments were performed on rabbit eyes. At 5 IN power the lesions were fully circular. Some lesions showed non-uniform characteristics along their circular path. Lesion depth depended on heating duration (60% of corneal thickness for 20s, and 30% for 10s). The results suggest that the critical shrinkage temperature (55-63degreesC) was reached at the central stroma and along the entire circular path in all the cases.Berjano, E.; Saiz Rodríguez, FJ.; Alió, J.; Ferrero, JM. (2003). Ring electrode for radio-frequency heating of the cornea: modelling and in vitro experiments. Medical & Biological Engineering & Computing. 41(6):630-639. https://doi.org/10.1007/BF02349970S630639416Alió, J. L., Ismail, M. M., Artola, A., andPérez-Santonja, J. J. (1997a): ‘Correction of hyperopia induced by photorefractive keratectomy using non-contact Ho: YAG laser thermal keratoplasty’,J. Refract. Surg.,13, pp. 13–16Alió, J. L., Ismail, M. M., andSanchez, J. L. (1997b): ‘Correction of hyperopia with non-contact Ho: YAG laser thermal keratoplasty’,J. Refract. Surg.,13, pp. 17–22Alió, J. L., andPérez-Santonja, J. J. (1999): ‘Correction of hyperopia by laser thermokeratoplasty (LTK)’ inPallikaris, I., andAgarwal, S. (Eds): ‘Refractive Surgery’ (Jaypee Brothers Medical Publishers Ltd, New Delhi, 1999), pp. 583–591Alió, J. L., andPérez-Santonja, J. J. (2002): ‘Correction of hyperopia by laser thermokeratoplasty (LTK)’ inAgarwal, S., Agarwal, A., Apple, D. J., Buratto, L., Alió, J. L., Pandey, S. K., andAgarwal, A. (Eds): ‘Textbook of ophthalmology’ (Lippincott Williams & Wilkins, Philadelphia, 2002), pp. 1331–1337Ayala, M. J., Alió, J. L., Ismail, M. M., andSánchez-Castro, J. M. (2000): ‘Experimental corneal histological study after thermokeratoplasty with holmium laser’,Arch. Soc. Esp. Oftalmol.,75, pp. 619–626Asbell, P. A., Maloney, R. K., Davidorf, J., Hersh, P., McDonald, M., Manche, E., andConductive Keratoplasty Study Group (2001): ‘Conductive keratoplasty for the correction of hyperopia’,Tr. Am. Ophtalmol. Soc.,99, pp. 79–87Avitall, B., Mughal, K., Hare, J., Helms, R., andKrum, D. (1997): ‘The effects of electrode-tissue contact on radiofrequency lesion generation’PACE,20, pp. 2899–2910Avitall, B., Helms, R. W., Koblish, J. B., Sieben, W., Kotov, A. V., andGupta, G. N. (1999): ‘The creation of linear contiguous lesions in the atria with an expandable loop catheter’,J. Am. Coll. Cardiol.,33, pp. 972–984Berjano, E. J., Saiz, J., andFerrero, J. M. (2002): ‘Radio-frequency heating of the cornea: Theoretical model andin vitro experiments’,IEEE Trans. Biomed. Eng.,49, pp. 196–205Brickmann, R., Kampmeier, J., Grotehusmann, U., Vogel, A., Koop, N., Asiyo-Vogel, M., Kamm, K., andBirngruber, R. (1996): ‘Corneal collagen denaturation in laserthermokeratoplasty’,SPIE Proc.,2681, pp. 56–63Choi, B., Kim, J., Welch, A. J., andPearce, J. A. (2002): ‘Dynamic impedance measurements during radio-frequency heating of cornea’,IEEE Trans. Biomed. Eng.,49, pp. 1610–1616Curley, M. G., andHamilton, P. S. (1997): ‘Creation of large thermal lesions in liver using saline-enhanced RF ablation’. Proc. 19th Ann. Int. Conf. IEEE Eng. Med. Biol. Soc., Chicago, pp. 2516–2519Doss, J. D., andAlbillar, J. I. (1980): ‘A technique for the selective heating of corneal stroma’,Contact Intraocular Lens Med.,6, pp. 13–17Doss, J. D. (1982): ‘Calculation of electric fields in conductive media’,Med. Phys.,9(4), pp. 566–573Gruenberg, P., Manning, W., Miller, D. andOlson, W. (1981): ‘Increase in rabbit corneal curvature by heated ring application’,Ann. Ophthalmol.,13, pp. 67–70Hata, C., andRaymond Chia, W.-K. (2001): ‘Catheter for circular tissue ablation and methods thereof’. US Patent 2001/0044625 A1Jain, M. K., andWolf, P. D. (1998): ‘Effect of electrode contact on lesion growth during temperature controlled radiofrequency ablation’, Proc. 20th Ann. Int. Conf. IEEE Eng. Med. Biol. Soc. Hong Kong (IEEE, Piscataway NJ) pp. 245–247Jain, M. K., andWolf, P. D. (1999): ‘Temperature controlled and constant power radiofrequency ablation: what affects lesion growth?’,IEEE Trans. Biomed. Eng.,46, pp. 1405–1412Krasteva, V. Tz., andPapazov, S. P. (2002): ‘Estimation of current density distribution under electrodes for external defibrillation’,Biomed. Eng. OnLine,1, 7Labonté, S. (1992): ‘A theoretical study of radio-frequency ablation of the myocardium’,PhD dissertation, Department of Electrical Engineering, University of Ottawa, CanadaLabonté, S. (1994): ‘Numerical model for radio-frequency ablation of the endocardium and its experimental validation’,IEEE Trans. Biomed. Eng.,41, pp. 108–115Mannis, M. J., Segal, W. A., andDarlington, J. K. (2001): ‘Making sense of refractive surgery in 2001: Why, when, for whom, and by whom?’,Mayo Clin. Proc.,76, pp. 823–829McCally, R. L., Bargeron, R. A., andGreen, W. R. (1983): ‘Stromal damage in rabbit corneas exposed to CO2 laser radiation’,Exp. Eye Res.,37, pp. 543–550McDonald, M. B., Hersh, P. S., Manche, E. E., Maloney, R. K., Davidorf, J., andSabry, M. (2002): ‘Conductive keratoplasty for the correction of low to moderate hyperopia: U.S. clinical trial 1-year results on 355 eyes’,Ophthalmol.,109, pp. 1978–1989McRury, I. D., Mitchell, M. A., Panescu, D. andHaines, D. E. (1997): ‘Non-uniform heating during radiofrequency ablation with long electrodes: monitoring the edge effect’,Circ.,96, pp. 4057–4064Méndez-g, A., andMéndez-Noble, A. (1997): ‘Conductive keratoplasty of the correction of hyperopia’ inSher, N. A. (Ed.) ‘Surgery for hyperopia and presbyopia’ (Williams & Wilkins, Baltimore, 1997), pp. 163–171Miller, D., andManning, W.J. (1978): ‘Alterations in curvature of bovine cornea using heated rings’,Invest. Ophthalmol., p. 297Mirotznik, M. S., andSchwartzman, D. (1996): ‘Nonuniform heating patterns of commercial electrodes for radiofrequency catheter ablation’,J. Cardiovasc. Electrophysiol.,7, pp. 1058–1062Nakagawa, H., Yamanashi, W. S., Pitha, J. V., Arruda, M., Wang, X., Ohtomo, K., Beckman, K. J., McClelland, J. H., Lazzara, R., andJackman, W. M. (1995): ‘Comparison ofin vivo tissue temperature profile and lesion geometry for radiofrequency ablation with a saline-irrigated electrode versus temperature control in a canine thigh muscle preparation’,Circ.,91, pp. 2264–2273Panescu, D., Whayne, J. G., Fleischman, S. D., Mirotznik, M. S., Swanson, D. K., andWebster, J. G. (1995): ‘Three-dimensional finite element analysis of current density and temperature distributions during radio-frequency ablation’,IEEE Trans. Biomed. Eng.,42, pp. 879–890Plonsey, R., andHeppner, D. B. (1967): ‘Considerations of quasistationarity in electrophysiological systems’,Bull. Math. Biophys.,29, pp. 657–664Rowsey, J. J. (1987): ‘Electrosurgical keratoplasty: Update and retraction’,Invest. Ophthalmol. Vis. Sci.,28, p. 224Rutzen, A. R., Roberts, C. W., Driller, J., Gomez, D., Lucas, B. C., Lizzi, F. L., andColeman, D. J. (1990): ‘Production of corneal lesions using high-intensity focused ultrasound’,Cornea,9, pp. 324–330Schwan, H. P., andFoster, K. R. (1980): ‘RF-fields interactions with biological systems: electrical properties and biophysical mechanism’,Proc. IEEE,68, pp. 104–113Seiler, T., Matallana, M., andBende, T. (1990): ‘Laser thermokeratoplasty by means of a pulsed Holmium:YAG Laser for the hyperopic correction’,Refrac. Corneal Surg.,6, pp. 335–339Silvestrini, T. A. (1998): ‘Electrosurgical procedure for the treatment of the cornea’. US Patent 5,766,171Simmons, W. N., Mackey, S., He, D. S. andMarcus, F. L. (1996): ‘Comparison of gold versus platinum electrodes on myocardial lesion size using radiofrequency energy’,PACE,19, pp. 398–402Stringer, H., andParr, J. (1964): ‘Shrinkage temperature of eye collagen’,Nature,204, p. 1307Trembly, B. S., andKeates, R. H. (1991): ‘Combined microwave heating and surface cooling of the cornea’,IEEE Trans. Biomed. Eng.,38, pp. 85–91Trembly, B. S., Hashizume, N., Moodie, K. L., Cohen, K. L., Tripoli, N. K., andHoopes, P. J. (2001): ‘Microwave thermal keratoplasty for myopia: keratoscopic evaluation in porcine eyes’,J. Refract. Surg.,17, pp. 682–688Tungjitkusolmun, S., Woo, E. J., Cao, H., Tsai, J. Z., Vorperian, V. R., andWebster, J. G. (2000): ‘Thermal-electrical finite element modelling for radio frequency cardiac ablation: effects of changes in myocardial properties’,Med. Biol. Eng. Comput.,38, pp. 562–568Wiley, J. D., andWebster, J. G. (1982): ‘Analysis and control of the current distribution under circular dispersive electrodes’,IEEE Trans. Biomed. Eng,29, pp. 381–38

Active zone proteins are dynamically associated with synaptic ribbons in rat pinealocytes

Synaptic ribbons (SRs) are prominent organelles that are abundant in the ribbon synapses of sensory neurons where they represent a specialization of the cytomatrix at the active zone (CAZ). SRs occur not only in neurons, but also in neuroendocrine pinealocytes where their function is still obscure. In this study, we report that pinealocyte SRs are associated with CAZ proteins such as Bassoon, Piccolo, CtBP1, Munc13–1, and the motorprotein KIF3A and, therefore, consist of a protein complex that resembles the ribbon complex of retinal and other sensory ribbon synapses. The pinealocyte ribbon complex is biochemically dynamic. Its protein composition changes in favor of Bassoon, Piccolo, and Munc13–1 at night and in favor of KIF3A during the day, whereas CtBP1 is equally present during the night and day. The diurnal dynamics of the ribbon complex persist under constant darkness and decrease after stimulus deprivation of the pineal gland by constant light. Our findings indicate that neuroendocrine pinealocytes possess a protein complex that resembles the CAZ of ribbon synapses in sensory organs and whose dynamics are under circadian regulation