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  • 1
    Electronic Resource
    Electronic Resource
    Upconversion-pumped infrared erbium laser (1986)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 60 (1986), S. 4077-4086 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A study of upconversion processes in Er3+ ions in CaF2 has led to an unambiguous demonstration of IR lasing produced by upconversion pumping alone. The study has shown: (1) strong upconversion lines originating from the 4I11/2 state; (2) the existence of both two-photon and three-photon upconversion processes; (3) an optimum concentration of 5–10 mol % for Er3+; and (4) upconversion efficiencies for the visible bands as high as 10% at 77 K and 1% at 300 K. Measurements of lasing between the 4I11/2 and 4I13/2 levels show that even though the lifetime of the upper (4I11/2) state is only half that of the lower state, self-quenching does not occur. Upconversion is implicated for this transition both by the nonpersistence of a "red shift'' during a lasing pulse, and by the opposite dependence on concentration of laser threshold energy and upconversion-produced fluorescent intensity. A simple theoretical model shows that a 2.8-μm laser operating between the 4I11/2 and 4I13/2 levels can be pumped solely by upconversion of ions in the excited 4I13/2 state produced by absorption of a 1.54-μm pulse. In addition, (1) a minimum of 1.54-μm pump energy is required; (2) lasing occurs with a delay inversely proportional to the pump energy; and (3) lasing can persist for as long as the lifetime of the lower (4I13/2) state. These predictions have been experimentally verified. The lasing experiments give a lower limit for the upconversion coefficient of α=10−16 cm3 s−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.337486
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  • 2
    Electronic Resource
    Electronic Resource
    Phenylephrine-Induced Ventricular Arrhythmias in Dogs with Inherited Sudden Death (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 7 (1996), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Dogs with Inherited Sudden Death. Introduction: Dogs with an inherited predisposition to sudden death display ventricular arrhythmias having certain characteristics, such as pause dependence, that are suggestive of early afterdepolarization-induced triggered activity. We hypothesized that α-adrenergic stimulation may facilitate the development of these arrhythmias by inducing a reflex bradycardia and by exerting a direct myocardial effect. Methods and Results: Twenty affected dogs and 7 unaffected dogs were studied. The incidence and severity of ventricular arrhythmias were determined after administration of phenylephrine (0.01 mg/kg IV), with or without pretreatment with propranolol (0.1 to 0.3 mg/kg IV), atropine (0.04 mg/kg IV), or prazosin (0.5 mg/kg IV). Third-degree heart block was induced by AV nodal ablation in 4 affected dogs. Phenylephrine increased ventricular arrhythmias in affected dogs, with or without pretreatment with propranolol, but did not induce ventricular arrhythmias in unaffected dogs. In dogs with intact AV nodal conduction, atropine increased sinus rate, which suppressed baseline and phenylephrine-induced arrhythmias. In dogs with heart block, arrhythmias were increased during baseline and after phenylephrine with or without pretreatment with atropine. Prazosin and overdrive ventricular pacing suppressed phenylephrine-induced arrhythmias. Conclusion: Phenylephrine increases ventricular arrhythmias in dogs with inherited sudden death via both an induction of reflex bradycardia and a direct myocardial effect. Superimposition of heightened α-adrenergic and vagal tone may facilitate the development of sudden death in these animals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1996.tb00519.x
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  • 3
    Electronic Resource
    Electronic Resource
    Decreased Density of Ito in Left Ventricular Myocytes from German Shepherd Dogs with Inherited Arrhythmias (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Decreased Ito in Dogs with Inherited Arrhythmias. Introduction: A colony of inbred German shepherd dogs with inherited ventricular arrhythmias has been established. Methods and Results: The inward rectifier (IKI), the slow delayed rectifier (IKs), and the transient outward current (IKI) were recorded from epicardial myocytes, and IKI, was recorded from Purkinje myocytes isolated from the left ventricles of dogs mildly or severely affected with arrhythmias, and unaffected relatives. There were no differences between unaffected and severely affected dogs in the densities of either IKI or IKI. Peak Ito density at +1–40 mV was reduced by 49% in epicardial myocytes from severely affected dogs. Ito density was also reduced in a subset of Purkinje myocytes. Boltzmann analysis of steady-state inactivation showed no differences between groups in slope factor. V1/2 the half-inactivation voltage, was shifted by +6.2 mV in epicardial cells from severely affected versus unaffected dogs. In addition, the time constant for Ito decay was reduced in mildly and severely affected dogs compared to unaffected dogs. Conclusion: Altered density and inactivation of Ito are associated with the presence of severe ventricular arrhythmias in inbred dogs at risk for sudden death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb00848.x
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  • 4
    Electronic Resource
    Electronic Resource
    Vector Quantization of T Wave Abnormalities Associated with a Predisposition to Ventricular Arrhythmias and Sudden Death (1998)
    Oxford, UK : Blackwell Publishing Ltd
    Annals of noninvasive electrocardiology 3 (1998), S. 0 
    Details
    ISSN: 1542-474X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Previous studies have suggested that irregular T wave morphologies are associated with an increased risk of sudden death. However, automated characterization of T wave abnormalities has been hampered by the lack of suitable analysis techniques. In this study, we tested a new method of T wave analysis in German shepherd dogs with inherited ventricular arrhythmias and sudden death.〈section xml:id="abs1-2"〉〈title type="main"〉MethodsSets of 24-hour ambulatory ECG recordings obtained from unaffected (n = 6) and affected (n = 5) dogs were digitized, automatically annotated to label each R wave, and placed into a matrix with the R waves aligned. A vector quantization algorithm separated the QRS-T complexes into classes according to T wave morphology. The existence of notched T waves was determined by assessing the number of zero crossings of the first derivative during the T wave.〈section xml:id="abs1-3"〉〈title type="main"〉ResultsThe duration of the QT interval was similar in affected and unaffected dogs (182 ± 14 ms vs 176 ± 16 ms, respectively). However, T wave morphology differed between the two groups. Specifically, affected dogs had a higher percentage of notched T waves than unaffected dogs (41.6%± 10.8% vs 5.0%± 1.2%, respectively). Notched T waves did not appear at all times of day, nor were they present in all leads.〈section xml:id="abs1-4"〉〈title type="main"〉ConclusionVector quantization and first derivative analyses were feasible and effective methods for detecting T wave abnormalities associated with the development of ventricular arrhythmias These methods ultimately may be useful for risk stratification of patients susceptible to ventricular arrhythmias and sudden death.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1542-474X.1998.tb00029.x
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  • 5
    Electronic Resource
    Electronic Resource
    Temporal Organization of Atrial Activity and Irregular Ventricular Rhythm During Spontaneous Atrial Fibrillation: (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Temporal Organization of Atrial Activity. Introduction: Atrial fibrillation (AF) is common in healthy horses. We studied the temporal organization of AF to test the hypothesis that the arrhythmia is governed by a high degree of periodicity and therefore is not random in the horse. Further, we surmised that concealed conduction of AF impulses in the AV node results in an inverse relationship between AF frequency and ventricular frequency. Methods and Results: Fast Fourier transform (FFT) analysis of atrial activity was done on signal-averaged ECGs (n = 11) and atrial electrograms (n = 3) of horses with AF at control (C), after quinidine sulfate (22 mg/kg by mouth every 2 hours) at 50% time to conversion (T50), and immediately before conversion (T90) to sinus rhythm. FFT always revealed a single dominant frequency peak. The mean dominant frequency decreased until conversion (C = 6.84 ± 0.85 Hz, T50 = 4.87 ± 1.5 Hz, T90 = 3.41 ± 1.18 Hz; P 〈 0.001). Mean AA intervals (n = 5WM gradually increased after quinidine. Mean RR intervals (n = 500), standard deviation of the mean ISDM), Poincaré plots, and serial autocorrelograms (SACs) of 500 RR intervals were measured at C and T90 to determine the ventricular response to AF and quinidine-induced changes in the variability of the ventricular response. Mean RR interval and SDM were reduced after quinidine (C = 1431 ± 266 msec and 695 ± 23 msec; T90 = 974 ± 116 msec and 273 ± 158 msec, respectively: P 〈 0.01). Poincaré plots and SAC at C and at T90 revealed a significant correlation of consecutive RR intervals typical of a system with a deterministic behavior. At T90, the variability of RR intervals was reduced and the overall periodicity of RR intervals was increased after quinidine administration. Conclusion: In the horse, AF is a complex arrhythmia characterized by a high degree of underlying periodicity. The inverse AA-to-RR interval relationship and reduced variability of RR intervals after quinidine suggest that the ventricular response during AF results from rate-dependent concealment of AF wavelets bombarding the AV node, which nevertheless results in a significant degree of short-term predictability of beat-to-beat changes in RR intervals.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.2000.tb00049.x
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  • 6
    Electronic Resource
    Electronic Resource
    An Animal Model of Spontaneous Arrhythmic Death (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 8 (1997), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Spontaneous Arrhythmic Death. Ventricular arrhythmias and the proclivity for sudden death have been identified in German shepherd dogs. This disorder is inherited, and affected animals can he consistently produced from an established colony. The arrhythmias are most prevalent in young dogs between 22 and 26 weeks of age, with death most frequent at this same age. Death occurs most frequently during presumed sleep or at rest after exercise or excitement. The QT interval is not prolonged; however, more frequent notching of the T wave exists in affected dogs compared to control dogs. Polymorphic rapid nonsustained ventricular tachycardia occurs most frequently following long RR intervals. Accordingly, perturhations that decrease the heart rate or enhance sinus arrhythmia increase the incidence of ventricular arrhythmias. Because the arrhythmias are age, behavior, and heart rate dependent, the autonomic nervous system may play a role in their generation. As determined by metaiodohenzylguanidine scintigraphy and immunocytochemical staining of tyrosine hydroxylase, cardiac sympathetic innervation is regionally deficient in affected dogs. Evidence suggests that initiation of the ventricular arrhythmias is caused by early after depolarization (EAD)-induced triggered activity originating from left ventricular Purkinje fibers. Alpha1-adrenergic stimulation provokes EADs in the Purkinje fibers and ventricular arrhythmias in the dogs. The development of EADs may be related to heterogeneity of repolarizing currents (Ito in particular) in affected dogs. From this canine model of spontaneous ventricular arrhythmias, the opportunity exists to investigate the interplay between abnormal development of cardiac innervation and the genesis of lethal ventricular arrhythmias.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1540-8167.1997.tb00614.x
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  • 7
    Electronic Resource
    Electronic Resource
    Long-Term Monitoring of Animal Models of Sudden Death (2000)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiovascular electrophysiology 11 (2000), S. 0 
    Details
    ISSN: 1540-8167
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1540-8167.2000.01342.x
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  • 8
    Electronic Resource
    Electronic Resource
    RECOMMENDATIONS FOR STANDARDS IN TRANSTHORACIC TWO-DIMENSIONAL ECHOCARDIOGRAPHY IN THE DOG AND CAT (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Veterinary radiology & ultrasound 35 (1994), S. 0 
    Details
    ISSN: 1740-8261
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Recommendations are presented for standardized imaging planes and display conventions for two-dimensional echocardiography in the dog and cat. Three transducer locations (“windows”) provide access to consistent imaging planes: the right parasternal location, the left caudal (apical) parasternal location, and the left cranial parasternal location. Recommendations for image display orientations are very similar to those for comparable human cardiac images, with the heart base or cranial aspect of the heart displayed to the examiner's right on the video display. From the right parasternal location, standard views include a long-axis four-chamber view and a long-axis left ventricular outflow view, and short-axis views at the levels of the left ventricular apex, papillary muscles, chordae tendineae, mitral valve, aortic valve, and pulmonary arteries. From the left caudal (apical) location, standard views include long-axis two-chamber and four-chamber views. From the left cranial parasternal location, standard views include a long-axis view of the left ventricular outflow tract and ascending aorta (with variations to image the right atrium and tricuspid valve, and the pulmonary valve and pulmonary artery), and a short-axis view of the aortic root encircled by the right heart. These images are presented by means of idealized line drawings. Adoption of these standards should facilitate consistent performance, recording, teaching, and communicating results of studies obtained by two-dimensional echocardiography.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1740-8261.1994.tb01588.x
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  • 9
    Electronic Resource
    Electronic Resource
    Detection of astroviruses in feces of a cat with diarrhea (1981)
    Springer
    Archives of virology 70 (1981), S. 373-376 
    Details
    ISSN: 1432-8798
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Astroviruses were detected by electron microscopy in the feces from a 4 month old kitten with diarrhea. The mean diameter of the viral particles was 28.7 nm, and they showed characteristic five- or six-pointed star-shaped surface configurations. The clinical disease manifested by the cat and the observed morphology of the viral particles are consistent with previous reports on astroviruses of other species.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320252
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  • 10
    Electronic Resource
    Electronic Resource
    Imaging Corneal Cells Using Low Power Laser Beams (1998)
    Springer
    Lasers in medical science 13 (1998), S. 148-154 
    Details
    ISSN: 1435-604X
    Keywords: Keywords: Cell dimensions; Corneal endothelium; Corneal epithelium; Laser imaging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract. A simple method of characterising epithelial and endothelial corneal cells using laser light is presented. A continuous wave helium-neon laser emitting at a wavelength of 632.8 nm and a continuous wave argon laser emitting at 488 and 514.5 nm were used. The cell images obtained were used to calculate the dimensions of the endothelial corneal cells, a typical value being 34–36 μm diameter, with overall measurement errors of ±21%. An optical mechanism for obtaining images is proposed and comments are made about the possibility of using this method as a diagnostic tool in corneal disease.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s101030050069
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