Neural Factors and Ventricular Electrical Instability

1980 ◽  
pp. 137-155 ◽  
Author(s):  
R. L. Verrier
Keyword(s):  
Electrical Instability ◽  
Neural Factors

A Superconducting Microscope

1971 ◽  
Vol 29 ◽  
pp. 10-11 ◽  
Author(s):  
R. E. Worsham ◽  
J. E. Mann ◽  
E. G. Richardson
Keyword(s):  
Liquid Helium ◽  
Focal Length ◽  
Vacuum System ◽  
Objective Lens ◽  
Electrical Instability ◽  
Radiation Shields ◽  
And Control ◽  
Thermal Oscillations ◽  
Flux Pump

This superconducting microscope, Figure 1, was first operated in May, 1970. The column, which started life as a Siemens Elmiskop I, was modified by removing the objective and intermediate lenses, the specimen chamber, and the complete vacuum system. The large cryostat contains the objective lens and stage. They are attached to the bottom of the 7-liter helium vessel and are surrounded by two vapor-cooled radiation shields.In the initial operational period 5-mm and 2-mm focal length objective lens pole pieces were used giving magnification up to 45000X. Without a stigmator and precision ground pole pieces, a resolution of about 50-100Å was achieved. The boil-off rate of the liquid helium was reduced to 0.2-0.3ℓ/hour after elimination of thermal oscillations in the cryostat. The calculated boil-off was 0.2ℓ/hour. No effect caused by mechanical or electrical instability was found. Both 4.2°K and 1.7-1.9°K operation were routine. Flux pump excitation and control of the lens were quite smooth, simple, and, apparently highly stable. Alignment of the objective lens proved quite awkward, however, with the long-thin epoxy glass posts used for supporting the lens.

Reproduction

2017 ◽  
Author(s):  
Derek Burton ◽  
Margaret Burton
Keyword(s):  
Reproductive Behaviour ◽  
Life Cycles ◽  
Freshwater Species ◽  
Adult Fish ◽  
Reproductive Patterns ◽  
Cell Divisions ◽  
Early Stages ◽  
External Cues ◽  
Neural Factors

Interspecific fish reproductive patterns, outputs and life cycles display the greatest variability within the vertebrates. Early stages of oogenesis can be repeated in adult fish, contrasting with mammals; the pre-set sequence of cell divisions in gametogenesis is otherwise similar and is described in detail. Most fish deposit much yolk (vitellogenesis) in developing eggs. Migrations, beach-spawning and mouth-brooding are some of the interesting variations. Fertilization is predominantly external but is internal in some groups such as chondrichthyans. The omission of annual reproduction is well established in some freshwater species and the idea that this may also be the case for marine teleosts is gaining acceptance. This should be taken into account for intensively fished species. The possible roles of external cues, hormones, pheromones and neural factors acting as ‘switches’ and coordinators in gametogenesis and reproductive behaviour are discussed.

Chemical and Electrical Instability of Mg$_\rm x$Zn$_{1- \rm x}$O in CdTe Thin Film Solar Cell

2021 ◽  
pp. 1-9
Author(s):  
Dongming Wang ◽  
Guangwei Wang ◽  
Yanbo Cai ◽  
Lingling Wu ◽  
Peng Zhu ◽  
...  
Keyword(s):  
Thin Film ◽  
Solar Cell ◽  
Thin Film Solar Cell ◽  
Cdte Thin Film ◽  
Electrical Instability

scholarly journals Mitochondrial Dysfunction in Atrial Fibrillation—Mechanisms and Pharmacological Interventions

2021 ◽  
Vol 10 (11) ◽  
pp. 2385
Author(s):  
Paweł Muszyński ◽  
Tomasz A. Bonda
Keyword(s):  
Atrial Fibrillation ◽  
Mitochondrial Dysfunction ◽  
Treatment Options ◽  
Therapeutic Interventions ◽  
Energy Deficit ◽  
Functional Changes ◽  
Electrical Instability ◽  
Ionic Fluxes ◽  
Prevention Methods ◽  
Invasive Techniques

Despite the enormous progress in the treatment of atrial fibrillation, mainly with the use of invasive techniques, many questions remain unanswered regarding the pathomechanism of the arrhythmia and its prevention methods. The development of atrial fibrillation requires functional changes in the myocardium that result from disturbed ionic fluxes and altered electrophysiology of the cardiomyocyte. Electrical instability and electrical remodeling underlying the arrhythmia may result from a cellular energy deficit and oxidative stress, which are caused by mitochondrial dysfunction. The significance of mitochondrial dysfunction in the pathogenesis of atrial fibrillation remains not fully elucidated; however, it is emphasized by the reduction of atrial fibrillation burden after therapeutic interventions improving the mitochondrial welfare. This review summarizes the mechanisms of mitochondrial dysfunction related to atrial fibrillation and current pharmacological treatment options targeting mitochondria to prevent or improve the outcome of atrial fibrillation.

NEURAL FACTORS IN THE MAINTENANCE OF LACTATION IN THE RAT

1967 ◽  
Vol 38 (1) ◽  
pp. 51-59 ◽  
Author(s):  
J. A. EDWARDSON ◽  
J. T. EAYRS
Keyword(s):  
Litter Size ◽  
Milk Yield ◽  
Quantitative Relationship ◽  
Mammary Tissue ◽  
Single Pair ◽  
Endocrine Response ◽  
Peripheral Innervation ◽  
Lactational Performance ◽  
Neural Factors

SUMMARY The role of the peripheral innervation of mammary tissue in the maintenance of lactation has been investigated by the procedure of selective thelectomy combined with denervation of the posterior thoracic nipples. When suckling is restricted to a single pair of nipples bilateral transection of the three adjacent nerves supplying a nipple arrests lactation completely; partial denervation is associated with a reduced level of lactational performance which is directly related to the concentration of the residual innervation. Increase in litter size is associated with an overall increase in milk-yield up to a limit beyond which the addition of further young to the litter is without effect. It is inferred that there is a quantitative relationship between the neural stimulus of suckling and the endocrine response of the hypothalamopituitary system.

scholarly journals Spontaneous calcium release in tissue from the failing canine heart

2009 ◽  
Vol 297 (4) ◽  
pp. H1235-H1242 ◽  
Author(s):  
Gregory S. Hoeker ◽  
Rodolphe P. Katra ◽  
Lance D. Wilson ◽  
Bradley N. Plummer ◽  
Kenneth R. Laurita
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Tissue Level ◽  
Calcium Handling ◽  
Canine Heart ◽  
Myocardial Cells ◽  
Spontaneous Release ◽  
Adrenergic Stimulation ◽  
Electrical Instability ◽  
Delayed Afterdepolarization

Abnormalities in calcium handling have been implicated as a significant source of electrical instability in heart failure (HF). While these abnormalities have been investigated extensively in isolated myocytes, how they manifest at the tissue level and trigger arrhythmias is not clear. We hypothesize that in HF, triggered activity (TA) is due to spontaneous calcium release from the sarcoplasmic reticulum that occurs in an aggregate of myocardial cells (an SRC) and that peak SCR amplitude is what determines whether TA will occur. Calcium and voltage optical mapping was performed in ventricular wedge preparations from canines with and without tachycardia-induced HF. In HF, steady-state calcium transients have reduced amplitude [135 vs. 170 ratiometric units (RU), P < 0.05] and increased duration (252 vs. 229 s, P < 0.05) compared with those of normal. Under control conditions and during β-adrenergic stimulation, TA was more frequent in HF (53% and 93%, respectively) compared with normal (0% and 55%, respectively, P < 0.025). The mechanism of arrhythmias was SCRs, leading to delayed afterdepolarization-mediated triggered beats. Interestingly, the rate of SCR rise was greater for events that triggered a beat (0.41 RU/ms) compared with those that did not (0.18 RU/ms, P < 0.001). In contrast, there was no difference in SCR amplitude between the two groups. In conclusion, TA in HF tissue is associated with abnormal calcium regulation and mediated by the spontaneous release of calcium from the sarcoplasmic reticulum in aggregates of myocardial cells (i.e., an SCR), but importantly, it is the rate of SCR rise rather than amplitude that was associated with TA.

scholarly journals In-Hospital Electrical Storm in Acute Myocardial Infarction　― Clinical Background and Mechanism of the Electrical Instability ―

2018 ◽  
Vol 83 (1) ◽  
pp. 91-100 ◽  
Author(s):  
Yoshinori Kobayashi ◽  
Kaoru Tanno ◽  
Akira Ueno ◽  
Seiji Fukamizu ◽  
Hiroshige Murata ◽  
...  
Keyword(s):  
Myocardial Infarction ◽  
Acute Myocardial Infarction ◽  
Electrical Storm ◽  
Electrical Instability ◽  
Clinical Background

Mechanistic modeling of vertebrate spatial contrast sensitivity and acuity at low luminance

2012 ◽  
Vol 29 (3) ◽  
pp. 169-181 ◽  
Author(s):  
JOHN R. JARVIS ◽  
CHRISTOPHER M. WATHES
Keyword(s):  
Contrast Sensitivity ◽  
Mechanistic Modeling ◽  
Spatial Integration ◽  
Modulation Transfer ◽  
Neural Noise ◽  
Light Levels ◽  
Low Luminance ◽  
Spatial Contrast Sensitivity ◽  
Neural Factors ◽  
Experimental Values

AbstractThe validity of the Barten theoretical model for describing the vertebrate spatial contrast sensitivity function (CSF) and acuity at scotopic light levels has been examined. Although this model (which has its basis in signal modulation transfer theory) can successfully describe vertebrate CSF, and its relation to underlying visual neurophysiology at photopic light levels, significant discrepancies between theory and experimental data have been found at scotopic levels. It is shown that in order to describe scotopic CSF, the theory must be modified to account for important mechanistic changes, which occur as cone vision switches to rod vision. These changes are divided into photon management factors [changes in optical performance (for a dilated pupil), quantum efficiency, receptor sampling] and neural factors (changes in spatial integration area, neural noise, and lateral inhibition in the retina). Predictions of both scotopic CSF and acuity obtained from the modified theory were found to be in good agreement with experimental values obtained from the human, macaque, cat, and owl monkey. The last two species have rod densities particularly suited for scotopic conditions.

Sign in / Sign up

Export Citation Format

Share Document