Conditions affecting rate of development of anoxic block in C fibers

1961 ◽  
Vol 200 (1) ◽  
pp. 39-45
Author(s):  
W. J. Crowley ◽  
M. A. Thomson
Keyword(s):  
Initial Period ◽  
Conduction Block ◽  
Irreversible Damage ◽  
Rate Of Development ◽  
C Fibers ◽  
Conduction Failure ◽  
Second Period

The isolated splenic nerve of sheep conducted impulses for an average of 10 minutes in the complete absence of oxygen at 37.5°C. If, immediately following conduction failure, the nerve was allowed to recuperate for 2 hours in oxygen it became able to conduct impulses as long during a repeated period of anoxia as it had initially. If the initial period of anoxia was prolonged beyond 28 minutes the nerve sustained irreversible damage and its ability to conduct impulses during subsequent periods of anoxia was shortened proportionally. For recuperation periods shorter than 2 hours the conduction block during the course of the second period of anoxia appeared earlier. Temperatures below 37.5°C or CO2 concentrations above 10% prolonged the time to conduction block during anoxia; temperatures above 37.5°C or frequencies of stimulation greater than 1/sec. shortened the time to conduction block during anoxia.

scholarly journals Ultrasound-assisted extraction of sunflower oil from the cake after sunflower seed pressing

2018 ◽  
Vol 63 (2) ◽  
pp. 195-204
Author(s):  
Dragan Milenkovic ◽  
Milutin Milosavljevic ◽  
Aleksandar Bojic
Keyword(s):  
Sunflower Seed ◽  
Initial Period ◽  
Extraction Kinetics ◽  
Ultrasound Assisted Extraction ◽  
Stationary Diffusion ◽  
Assisted Extraction ◽  
Soxhlet Apparatus ◽  
Ultrasound Application ◽  
Ultrasound Assisted ◽  
Second Period

The influence of ultrasound application on the extraction (UE) of the cake after sunflower seed pressing was studied. Three different solvents were used for extraction in the Soxhlet apparatus: n-hexane, petroleum ether and extraction petrol. Petrol for extraction showed the highest yield. It has been shown that the using of ultrasound improved the extraction kinetics in the initial period - washing, and in the second period - the diffusion of oil from the mass of the cake. The parameters of the non-stationary diffusion model with and without the use of ultrasound were k' = 0.039 min-1, k' = 0.026 min-1 and b' = 0.713, i.e. b' = 0.589, respectively. Oil yield was also slightly higher in the ultrasonically supported extraction.

Ischemic conduction failure and energy metabolism in experimental diabetic neuropathy

1985 ◽  
Vol 248 (4) ◽  
pp. E457-E462 ◽  
Author(s):  
P. A. Low ◽  
K. Ward ◽  
J. D. Schmelzer ◽  
S. Brimijoin
Keyword(s):  
Diabetic Neuropathy ◽  
Anaerobic Metabolism ◽  
Conduction Block ◽  
Creatine Phosphate ◽  
High Energy ◽  
High Energy Phosphate ◽  
Gradual Decline ◽  
Progressive Decline ◽  
Conduction Failure ◽  
Experimental Diabetic Neuropathy

We examined the effect of ischemia on nerve conduction in experimental diabetic neuropathy (EDN) and related electrophysiological changes to nerve adenosine triphosphate (ATP), creatine phosphate (CP), and lactate under anoxic conditions. Rats rendered diabetic with streptozotocin had a resistance to ischemic conduction block (RICB). Caudal nerve action potential (NAP) was well maintained for 10 min in controls and for 15 min in EDN, after which time NAP declined in both groups but more rapidly in normal rats. Time to 50% reduction in nerve ATP and CP was 10 and 3 min, respectively, in controls and delayed to 20 and 8 min in EDN. Rate of utilization of high-energy phosphate (approximately P) was linear for 5 min in controls to be followed by a progressive decline. In EDN rate of utilization of approximately P was linear to 15 min to be followed by a more gradual decline than in normal nerves. These findings suggest that the maintenance of nerve transmission in anoxic-ischemic states depends on anaerobic metabolism and that RICB in EDN is due in part to the ability of diabetic nerves to maintain a higher level of anaerobic glycolysis and for a longer time than normal nerves.

Pregnancy Does Not Increase Susceptibility to Bupivacaine in Spinal Root Axons

1997 ◽  
Vol 87 (3) ◽  
pp. 610-616 ◽  
Author(s):  
Friederike B. Dietz ◽  
Richard A. Jaffe
Keyword(s):  
Conduction Block ◽  
Late Pregnancy ◽  
Underlying Mechanism ◽  
Ventral Root ◽  
Spinal Root ◽  
Pregnant Rats ◽  
C Fibers ◽  
Antinociceptive Effects ◽  
The Difference

Background The underlying mechanism of enhanced antinociceptive effects and increased susceptibility to local anesthetics during pregnancy is not known. Mechanical, hormonal, biochemical, and neural changes have been suggested. The authors measured the susceptibility of individual spinal root axons to bupivacaine during late pregnancy in rats and compared them with similar measurements in nonpregnant rats. Methods Lumbar dorsal and ventral roots were excised from anesthetized pregnant and nonpregnant rats. Single-fiber dissection and recording techniques were used to isolate activity in individual axons. Supramaximal constant voltage stimuli were delivered to the distal end of the root. During in vitro perfusion, each root was exposed to increasing concentrations of bupivacaine, and the minimum blocking concentration (Cm) and the concentration that increased conduction latency by 50% (EC50) were measured. Results Myelinated and unmyelinated dorsal and ventral root axons of pregnant rats appeared to be less sensitive to steady-state conduction block and to the latency-increasing effects of bupivacaine than were equivalent axons from nonpregnant rats. Although when comparing specific axon types, only the difference in C-fibers was significant (Cm = 29.8 microM for pregnant and Cm = 22.1 microM for nonpregnant rats, P < 0.05; EC50 = 19.9 microM and 13.6 microM, respectively). Conclusions In contrast to clinical expectations, the susceptibility to bupivacaine conduction block in individual dorsal and ventral root axons during late pregnancy in rats was not greater in pregnant animals. Pregnancy-related changes in diffusion barriers and activation of endogenous analgesic systems without changes in the electrophysiologic properties of spinal root axons are suggested as possible explanations for the discrepancy between clinical and experimental observations.

Drivers of Poland’s Successful Transition

2018 ◽  
Author(s):  
Marcin Piatkowski
Keyword(s):  
Transition Economies ◽  
Initial Period ◽  
Shock Therapy ◽  
Lessons Learned ◽  
Economic Recovery ◽  
Ongoing Debate ◽  
Pros And Cons ◽  
Gradual Approach ◽  
Second Period

In this chapter I explain the proximate drivers of Poland’s economic success since 1989. I divide the transition into the initial period of ‘shock therapy’ during 1989 1991 and then the second period of economic recovery after 1992. I discuss the ongoing debate on the pros and cons of ‘shock therapy’ versus a ‘gradual’ approach to post-communist transition. I use the example of Poland’s ‘shock therapy’ to analyze both approaches. I conclude that that the differences in actual policies were smaller than implied by the rhetoric of both sides of the debate. I then explain why Poland was more successful than other transition economies, and discuss whether Poland could have grown even faster. I argue that on the whole the Polish transition was almost ‘as good as it gets’. I draw the lessons learned and policy insights from Poland’s transition for other countries.

Loss of Potassium Homeostasis Underlies Hyperthermic Conduction Failure in Control and Preconditioned Locusts

2009 ◽  
Vol 102 (1) ◽  
pp. 285-293 ◽  
Author(s):  
Tomas G. A. Money ◽  
Corinne I. Rodgers ◽  
Stuart M. K. McGregor ◽  
R. Meldrum Robertson
Keyword(s):  
Action Potential ◽  
Conduction Block ◽  
Extreme Temperature ◽  
Membrane Properties ◽  
Extracellular Potassium ◽  
Movement Detector ◽  
Ion Distribution ◽  
Extracellular Potassium Concentration ◽  
Failure Event ◽  
Conduction Failure

At extreme temperature, neurons cease to function appropriately. Prior exposure to a heat stress (heat shock [HS]) can extend the temperature range for action potential conduction in the axon, but how this occurs is not well understood. Here we use electrophysiological recordings from the axon of a locust visual interneuron, the descending contralateral movement detector (DCMD), to examine what physiological changes result in conduction failure and what modifications allow for the observed plasticity following HS. We show that at high temperature, conduction failure in the DCMD occurred preferentially where the axon passes through the thoracic ganglia rather than in the connective. Although the membrane potential hyperpolarized with increasing temperature, we observed a modest depolarization (3–6 mV) in the period preceding the failure. Prior to the conduction block, action potential amplitude decreased and half-width increased. Both of these failure-associated effects were attenuated following HS. Extracellular potassium concentration ([K+]o) increased sharply at failure and the failure event could be mimicked by the application of high [K+]o. Surges in [K+]o were muted following HS, suggesting that HS may act to stabilize ion distribution. Indeed, experimentally increased [K+]o lowered failure temperature significantly more in control animals than in HS animals and experimentally maintained [K+]o was found to be protective. We suggest that the more attenuated effects of failure on the membrane properties of the DCMD axon in HS animals is consistent with a decrease in the disruptive nature of the [K+]o-dependent failure event following HS and thus represents an adaptive mechanism to cope with thermal stress.

scholarly journals EXPERIMENTAL GLOMERULONEPHRITIS

1964 ◽  
Vol 119 (6) ◽  
pp. 965-982 ◽  
Author(s):  
Emil Unanue ◽  
Frank J. Dixon
Keyword(s):  
Immune Response ◽  
Gamma Globulin ◽  
Fluorescent Antibody ◽  
Initial Period ◽  
Glomerular Lesion ◽  
Nephrotoxic Serum Nephritis ◽  
Chronic Nephritis ◽  
Glomerular Lesions ◽  
Second Period

Rats with nephrotoxic serum nephritis may show fixation of complement (C') in the glomeruli during two periods. The first period occurs immediately after the injection of the antisera and extends until the host response occurs. The second period is related to the deposit of rat gamma globulin in the glomeruli presumably occurring at the time of the immune response to the heterologous nephrotoxic serum (NTS). This second period terminates about 2 to 3 weeks after injection of NTS, presumably at the time the rat stops making antibodies to the nephrotoxic gamma globulin fixed in the glomeruli. After this period, the glomerular lesion is incapable of fixing detectable amounts of circulating C' unless the antibody response to the heterologous globulin is reactivated. The immunological events which take place in the initial 2 to 3 week period appear to produce a permanent and irreparable lesion in the glomeruli leading to chronic nephritis. Rabbit NTS produces fixation of rat C' during both periods. Duck NTS shows no detectable fixation of rat C' until rat gamma globulin fixes in the glomeruli at the time of the host immune response to the heterologous nephrotoxic gamma globulin. Decomplementation of rats injected with rabbit NTS produces an amelioration of the initial period of nephrotoxic serum nephritis. The fixation of C' in the glomerular lesions was studied with the use of fluorescent antibody methods. The detection of host beta-1C globulin and gamma globulin in the glomerulus pointed to an immune reaction but not necessarily an active one. The tissue C' fixation test using kidney slices and guinea pig C' proved to be a more sensitive method of detecting tissue reactants capable of fixing C', but its relationship to in vivo events is not certain.

scholarly journals Pembaruan Hukum Islam di Indonesia

TAJDID ◽  
2019 ◽  
Vol 26 (2) ◽  
pp. 215
Author(s):  
Ismail Ismail
Keyword(s):  
Local Community ◽  
Islamic Law ◽  
Initial Period ◽  
17Th Century ◽  
Legal Aspects ◽  
Historical Record ◽  
Long Time ◽  
Religious Sect ◽  
Second Period

In the early days of the entry of Islam in Indonesia the emphasis of Islamic teachings on legal aspects was not as strong as it is now. From the historical record, Islam that developed in Indonesia in the early days was very oriented towards tasawuf. This is because Islamic tasawuf who came to the archipelago, in certain aspects "fit" with the background of the local community influenced by Hindu-Buddhist asceticism and syncretism of local beliefs. In the next stage, Islam is oriented to Sufism, gradually becoming more oriented towards shari'ah. This change in orientation was partly due to a process of renewal or refinement that began in the 17th century and continues today. The Islamic law developing in Indonesia nowadays  has got much changing from its origin, syafi’iyah to moderate. The modernity of Islamic law that take long time is provable by appearing of the national fiqh mazhab (religious sect). To get the better understanding on the happening process, the writer  will divide into two periods of modernity. First is the initial period indicated by having  ijtihad and self-releasing on taklid or fanatic attitude to a certain mazhab. The Second period load the effort to bear the mazhab that is suitable to the national personality. This is called National mazhab later.

Zagłada jako horror. Kilka uwag o literaturze polskiej 1985–2015

2016 ◽  
pp. 375-394
Author(s):  
Przemysław Czapliński
Keyword(s):  
Initial Period ◽  
Polish Literature ◽  
The Third ◽  
The Poor ◽  
The Holocaust ◽  
Self Knowledge ◽  
Second Period

The author suggests that the depictions of the Holocaust in Polish literature of 1918–2014 should be categorized as horror. From the chronological perspective, Czapliński divides those thirty years into three shorter periods: 1) the initial period (from Claude Lanzmann’s Shoah and Jan Błoński’s essay “The Poor Poles Look at the Ghetto” to Wilhelm Dichter’s and Michał Głowiński’s memoirs) was dominated by white horror, which presented Jews as ghosts demanding a place in the Polish memory; 2) during the second period (from Marek Bieńczyk’s Tworki and Jan Tomasz Gross’ Neighbors until the end of the 2010s) the horror poetics was used to reveal those principles of pre-war and occupation-period normality which helped the Germans conduct the Holocaust and which conditioned the exclusion of Jews from the Polish circle of ‘normal humanity’; 3) during the third period (from Gross’s Golden Harvest until now) Jews return as the undead, violating the rules of distance and obliging Poles to physically touch the disgusting topic of the Holocaust. The contact with the Holocaust as something abhorring becomes a condition for self-knowledge, purging, and establishment of a new imaginary community.

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