The initial heat production of stimulated nerve

1958 ◽  
Vol 149 (935) ◽  
pp. 167-175 ◽  
Keyword(s):  
Heat Production ◽  
Room Temperature ◽  
Repetitive Stimulation ◽  
Short Delay ◽  
Nodal Region ◽  
Probable Interpretation ◽  
Two Phases ◽  
Initial Heat

Non-medullated nerve . In a single impulse at 0 °C the heat production occurs in two phases, positive and negative. Records were made of the heat during repetitive stimulation at various frequencies. With 5 shocks/s the diphasic character of the heat was evident, with 10 shocks/s the instruments were too slow to show it, as they are above about 12 °C at any frequency. But the two phases probably occur under all conditions. Medullated nerve . No indication was obtained that the heat production in medullated nerve is diphasic : but this may well be due to the instruments being too slow to separate the phases. During a short tetanus at 0 °C the rate of heat production rises apparently abruptly at the start, and falls equally suddenly at the end, of the stimulus. This is the most probable interpretation of the records, but it remains possible that a short delay (0.02 to 0.04 s) may occur between an impulse and the corresponding heat production: at room temperature this could not be more than about 0.01 s. The magnitude of the heat production is considered in relation to the possibility that activity during an impulse occurs only in the nodal region.

scholarly journals A closer analysis of the heat production of nerve

1932 ◽  
Vol 111 (770) ◽  
pp. 106-164 ◽  
Keyword(s):  
Heat Production ◽  
The Other ◽  
Strict Sense ◽  
Initial State ◽  
Chemical Changes ◽  
Two Phases ◽  
The One ◽  
Physical And Chemical ◽  
Initial Heat

The heat production of nerve is believed to occur in two phases, “initial” and “recovery”; the former is presumably an accompaniment of the physical and chemical changes which take place during the propagation of the nerve restored to its initial state. It is not easy to separate the one from the other ; indeed, during the earlier part of this research it was realised that in a strict sense, and on the evidence available, there might really be no “initial” heat at all. This is made clear by the following discussion.

scholarly journals The three phases of nerve heat production

1933 ◽  
Vol 113 (784) ◽  
pp. 345-356 ◽  
Keyword(s):  
Heat Production ◽  
Recording System ◽  
Stimulating Electrodes ◽  
Two Phases ◽  
Initial Heat ◽  
Three Phases

The heat production of stimulated nerve occurs in two main stages, initial and recovery. The first object of this paper is to define and distinguish the initial heat more clearly; the second is to present fresh evidence that the recovery heat occurs in two phases, the first complete in a few seconds, the second only in 30 minutes. Since an earlier paper (Hill, 1932, a ) was written, various attempts have been made to quicken up the recording system of thermopile and galvanometer, so as to secure a sharper analysis of the heat. A new thermopile has been constructed by Mr. A. C. Downing, with soldered constantan-iron couples and bakelite insulation. It is no more sensitive than the old one, but possesses the great advantage for some purposes that it is so well shielded from heat leaking from the stimulating electrodes that a correction is seldom necessary.

Human pituitary chronoendocrinology: repetitive stimulation with LRH/TRH at different times of the day

1983 ◽  
Vol 102 (3) ◽  
pp. 327-331 ◽  
Author(s):  
F. R. Pérez-López ◽  
A. Legido ◽  
M. D. Abós ◽  
L. Lafarga
Keyword(s):  
Healthy Subjects ◽  
Repetitive Stimulation ◽  
Hormonal Changes ◽  
Human Pituitary ◽  
Single Bolus ◽  
The Third ◽  
Hypothalamic Hormones ◽  
The Mean ◽  
Two Phases ◽  
Tsh Levels

Abstract. To determine whether human pituitary is characterized by a circadian periodicity in response to repetitive injection of hypothalamic hormones, 8 healthy subjects were challenged iv with a triple stimulation with 50 μg of LRH and 100 μg of TRH in a single bolus at 0, 90 and 180 min, receiving the first pulse of hypothalamic hormones either at 02.00 h (02.00 h test) or at 09.00 h (09.00 h test). In addition, a placebo was injected instead of LRH/TRH to evaluate the spontaneous hormonal changes during the 02.00 h test. The LH, FSH, Prl and TSH basal levels were similar in the two phases studied. The mean LH, FSH and TSH peaks after each injection of LRH/TRH were similar among them. The mean Prl peak responses to the third pulse of LRH/TRH, in both the 02.00 h and the 09.00 h tests, were lower (P < 0.05) than those after the first pulse of LRH/TRH. Placebo did not significantly change circulating LH, FSH, Prl or TSH during nocturnal sampling. The mean LH, FSH and Prl levels after LRH/TRH during the 02.00 h test were similar to those during the 09.00 h test. The mean TSH levels 15 min after the second and third pulses of LRH/TRH during the 02.00 h test were higher (P < 0.05) than those of the 09.00 h test. Thus, thyrotropes responsiveness to pulsatile stimulation with LRH/TRH is greater during the night than in the morning, while LH, FSH and Prl responses remain constant at the two phases studied.

FACTORS INFLUENCING THE AMOUNT OF INSULIN EXTRACTABLE FROM BEEF PANCREAS: I. EFFECTS OF AGING FRESH PANCREAS AT ROOM TEMPERATURE

1957 ◽  
Vol 35 (7) ◽  
pp. 527-535 ◽  
Author(s):  
Gerald A. Wrenshall ◽  
Charles H. Best ◽  
W. Stanley Hartroft
Keyword(s):  
Experimental Evidence ◽  
Beta Cells ◽  
Room Temperature ◽  
Second Phase ◽  
Structural Components ◽  
Factors Influencing ◽  
Two Phases ◽  
Early Rise ◽  
Effects Of Aging ◽  
New Formation

Effects on the concentration of extractable insulin of aging fresh beef pancreas at temperatures in the 22–26 °C. range have been described. Two phases of change with time of aging have been observed, describable as a transient increase superimposed on a progressive fall toward zero in the concentration of insulin extractable from the pancreas. In two of the eight experiments reported only the second phase was detected.Various hypotheses concerning the cause of the first phase are considered. The available experimental evidence is considered to support the hypothesis that the early rise in extractable insulin resulted from the continuing new formation of insulin from structural components already present in the cytoplasm of the beta cells at time of exsanguination, or diffusing into it thereafter. The progressive fall in the extractable insulin during the second phase must have resulted from destruction or inactivation of insulin within the pancreas.The bearing of these recent findings on the usage of the term "The insulin content of the pancreas" has been discussed.

Recovery heat production of mammalian fast- and slow-twitch muscles

1976 ◽  
Vol 230 (6) ◽  
pp. 1637-1643 ◽  
Author(s):  
IR Wendt ◽  
CL Gibbs
Keyword(s):  
Heat Production ◽  
Total Heat ◽  
Anaerobic Conditions ◽  
A Value ◽  
Glycolytic Activity ◽  
Slow Twitch ◽  
Initial Recovery ◽  
Fast Twitch ◽  
Mitochondrial Oxidative Metabolism ◽  
Initial Heat

Relationships between initial heat and recovery heat in fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles of the rat have been investigated by estimating the ratio of total heat (initial + recovery) to estimated initial heat. Results obtained from SOL agreed well with earlier data from amphibian skeletal muscle and indicated that in tetanic contractions of SOL the ratio,total heat/initial heat, was slightly greater than 2. Experiments on EDL revealed complexities not previously reported for amphibian muscle. Anaerobic total heat production by EDL was as much as 75% of aerobic heat production. When the initial heat was estimated under anaerobic conditions and with iodacetate present, the apparent ratio of total heat/initial heat in tetanic contractions of EDL approached a value of 2. The results are discussed in relation to the enzymatic characteristics of these muscles, and it is suggested that the recovery heat of SOL arises mainly from mitochondrial oxidative metabolism while that of EDL arises, to a large extent, from glycolytic activity.

scholarly journals The two phases of heat production of nerve

1927 ◽  
Vol 62 (4) ◽  
pp. 349-363 ◽  
Author(s):  
R. W. Gerard
Keyword(s):  
Heat Production ◽  
Two Phases

scholarly journals The heat production in isometric and isotonic twitches

1930 ◽  
Vol 107 (749) ◽  
pp. 115-131 ◽  
Keyword(s):  
Lactic Acid ◽  
Heat Production ◽  
Isometric Contraction ◽  
Room Temperature ◽  
Probable Error ◽  
Isotonic Contraction ◽  
Complete Relaxation ◽  
Initial Load ◽  
The Difference ◽  
Isotonic Contractions

In a recent paper from Meyerhof's laboratory P. Rothschild (1930) has shown that in a series of isometric twitches of a frog's gastrocnemius or semi-membranosus considerably more lactic acid may be liberated than in the same number of isotonic twitches with the same initial load: while with sartorius there may be little or no difference. 90 to 150 shocks were applied, at intervals of 5 to 10 seconds, at room temperature (11° C. to 17° C.), and either directly or to the nerve: the intervals were sufficient to allow complete relaxation between twitches and the number of twitches was not so great as to cause appreciable fatigue. With semi-membranosus, with an initial load of 10 or 20 g. the lactic acid in the isotonic averaged about 35 per cent. less than in the isometric twitches: with gastrocnemius stimulated through its nerve following six results were obtained at 15° to 17° C. in 92 to 102 twitches: Initial load: g. ............ 25 20 20 20 10 10 After-load (isotonic): g. ............. 13 50 50 50 140 140 Deficit due to shortening: p. c. ............. 70 49 64 76 34 25 Thus in an isotonic contraction with considerable shortening the lactic acid may be ½ to ⅓ of the amount in an isometric contraction with the same initial load: while when the shortening is smaller (greater after-load) the difference may be less (last two experiments). With sartorius, however, in 110 to 150 contractions at 12° C. to 17° C., there was a slight excess of lactic acid in the isotonic contractions, averaging about 8 per cent. The smallness of the difference was regarded by Rothschild as insignificant, in view of the probable error of his estimations: in this, as will be seen, he unduly depreciated the accuracy of his own observations: his difference was probably genuine.

Relationship between Microstructure and Tensile Strength in the Directionally Solidified (23-27) at. % Al-Ni Alloys

2006 ◽  
Vol 510-511 ◽  
pp. 458-461 ◽  
Author(s):  
Y. Lu ◽  
H.C. Kim ◽  
Je Hyun Lee ◽  
Myung Hoon Oh ◽  
Dang Moon Wee ◽  
...  
Keyword(s):  
Room Temperature ◽  
Eutectic Composition ◽  
Volume Fraction ◽  
Solidification Rate ◽  
Transgranular Fracture ◽  
Hypoeutectic Alloy ◽  
Directionally Solidified ◽  
Dendritic Microstructure ◽  
Ni Alloys ◽  
Two Phases

Directional or single crystal technique was applied to enhance the ductility, and two phases of γ (Ni) phase or β (NiAl) phase in γ‘(Ni3Al) matrix were also considered to increase the strength and ductility. In this study, directionally solidified rods were prepared at the solidification rate of 50µm/s in 23-27 at.% Al-Ni alloys, and tensile strengths of these rods were analyzed at room temperature. Directionally solidified samples showed the γ dendrite fibers formed in the Ni3Al matrix in the hypo eutectic composition of 23 at.% Al, the γ‘ single phase in the eutectic composition of 24.5 at. % Al, and the β dendrite fibers in the γ‘ matrix in the hyper eutectic compositions of 25, 26, 27 at.% Al. The hypoeutectic alloy including γ dendrites with γ‘ matrix exhibited a large elongation of over 70% with ductile transgranular fracture at room temperature. With increasing Al contents, the γ dendritic microstructure changed to the β dendrite in the γ‘ matrix, which resulted in decreasing the elongation by increasing the volume fraction of the brittle β dendrites in the ductile γ’ matrix.

Effects of phentolamine on thermoregulatory functions of rats to different ambient temperatures

1979 ◽  
Vol 57 (12) ◽  
pp. 1401-1406 ◽  
Author(s):  
M. T. Lin ◽  
Andi Chandra ◽  
T. C. Fung
Keyword(s):  
Heat Loss ◽  
Rectal Temperature ◽  
Heat Production ◽  
Room Temperature ◽  
Metabolic Heat Production ◽  
Central Component ◽  
Evaporative Heat Loss ◽  
Central Administration ◽  
Ambient Temperatures ◽  
Metabolic Heat

The effects of both systemic and central administration of phentolamine on the thermoregulatory functions of conscious rats to various ambient temperatures were assessed. Injection of phentolamine intraperitoneally or into a lateral cerebral ventricle both produced a dose-dependent fall in rectal temperature at room temperature and below it. At a cold environmental temperature (8 °C) the hypothermia in response to phentolamine was due to a decrease in metabolic heat production, but at room temperature (22 °C) the hypothermia was due to cutaneous vasodilatation (as indicated by an increase in foot and tail skin temperatures) and decreased metabolic heat production. There were no changes in respiratory evaporative heat loss. However, in the hot environment (30 °C), phentolamine administration produced no changes in rectal temperature or other thermoregulatory responses. A central component of action is indicated by the fact that a much smaller intraventricular dose of phentolamine was required to exert the same effect as intraperitoneal injection. The data indicate that phentolamine decreases heat production and (or) increases heat loss which leads to hypothermia, probably via central nervous system actions.

scholarly journals Light Adaptation in the Ventral Photoreceptor of Limulus

1974 ◽  
Vol 64 (2) ◽  
pp. 166-185 ◽  
Author(s):  
Richard Srebro ◽  
Michael Behbehani
Keyword(s):  
Time Course ◽  
Light Adaptation ◽  
Light Response ◽  
Slow Phase ◽  
Rapid Phase ◽  
Short Delay ◽  
Light Intensities ◽  
Lateral Eye ◽  
Complex Process ◽  
Two Phases

Light adaptation in both the ventral photoreceptor and the lateral eye photoreceptor is a complex process consisting of at least two phases. One phase, which we call the rapid phase of adaptation, occurs whenever there is temporal overlap of the discrete waves that compose a light response. The recovery from the rapid phase of adaptation follows an exponential time-course with a time constant of approximately 75 ms at 21°C. The rapid phase of adaptation occurs at light intensities barely above discrete wave threshold as well as at substantially higher light intensities with the same recovery time-course at all intensities. It occurs in voltage-clamped and unclamped photoreceptors. The kinetics of the rapid phase of adaptation is closely correlated to the photocurrent which appears to initiate it after a short delay. The rapid phase of adaptation is probably identical to what is called the "adapting bump" process. At light intensities greater than about 10 times discrete wave threshold another phase of light adaptation occurs. It develops slowly over a period of ½ s or so, and decays even more slowly over a period of several seconds. It is graded with light intensity and occurs in both voltage-clamped and unclamped photoreceptors. We call this the slow phase of light adaptation.

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