Threshold temperatures for shivering in acute and chronic hypercapnia

1976 ◽  
Vol 41 (1) ◽  
pp. 67-70 ◽  
Author(s):  
K. E. Schaefer ◽  
W. Wunnenberg
Keyword(s):  
Oxygen Consumption ◽  
Cold Exposure ◽  
Muscle Activity ◽  
Chronic Exposure ◽  
Time Course ◽  
Acute Exposure ◽  
Metabolic Adaptation ◽  
Cervical Cord ◽  
Threshold Temperatures ◽  
Electrical Muscle

Threshold temperatures for shivering in acute and chronic hypercapnia were determined in guinea pigs by measuring the time course of cervical cord temperature, skin temperature, oxygen consumption (Vo2), and electrical muscle activity during cold exposure (15 degrees C). Prior to acute exposure to CO2, the shivering threshold was determined in each animal during controlconditions breathing air. With increasing CO2 concentrations (5,7.5, and 15% CO2) the shivering thresholds fell to lower temperatures, decreasing by approximately 40 degrees C at 15% CO2. The shift of the shivering threshold to lower values found during acute exposure to 15% CO2 was reversed after chronic exposure to 15% CO2 for 3 days, which marks the time of metabolic adaptation to CO2.

Acclimatization of Scottish Blackface sheep to cold. 2. Skin temperature, heart rate, respiration rate, shivering intensity and skinfold thickness

1968 ◽  
Vol 10 (1) ◽  
pp. 17-35 ◽  
Author(s):  
A. R. Sykes ◽  
J. Slee
Keyword(s):  
Heart Rate ◽  
Skin Temperature ◽  
Cold Exposure ◽  
Chronic Exposure ◽  
Physiological Responses ◽  
Skinfold Thickness ◽  
Acute Exposure ◽  
Heart Rates ◽  
Ambient Temperatures ◽  
Acute Cold Exposure

Closely shorn Scottish Blackface female sheep aged 9–14 months, half on high plane and half on low plane nutrition, were subjected, in climate chambers, to two short acute cold exposures down to −20°C. The acute exposures were separated by two weeks chronic exposure to a moderately subcriticai temperature (+8°C) or to a thermoneutral temperature (+30°C). Most of the sheep showed a greater resistance to body cooling at the second acute exposure (Slee and Sykes, 1967). This increased resistance to hypothermia, defined as acclimatization, was apparently influenced more by acute than by chronic cold exposure. The present paper deals with changes in skin temperature, heart rate, shivering intensity and skinfold thickness which also resulted from cold exposure, and accompanied acclimatization.After acute cold exposure followed by chronic exposure to +8°C the following changes in these parameters were observed:1. Extremity skin temperatures and heart rates were consistently increased at thermoneutral ambient temperatures.2. Vasoconstriction of the extremities and increased heart rate, both of which normally occur during the early stages of cold exposure, were delayed.3. Heart rates at sub-zero ambient temperatures were increased.4. Cold-induced vasodilatation at sub-zero ambient temperatures was increased.After acute cold treatment alone the intensity of shivering during the second acute exposure was reduced. Also the onset of foot vasoconstriction was slightly delayed.A highly significant relationship was observed between shivering intensity and heart rate during cold exposure.Plane of nutrition had less effect on the physiological responses to cooling than did previous cold experience.It was suggested in discussion that the physiological responses associated with acclimatization were: elevated basal metabolic rate, delayed onset of vasoconstriction and delayed metabolic response to cold, and consequent lowering of the critical temperature. Summit metabolism was also increased and shivering intensity reduced during acute cold exposure. Some of these responses could have resulted from either acute or chronic moderate cold exposure. However their persistence, once induced, appeared to depend upon continued exposure to moderate cold.

Association of Dyskalemias with Ischemic Stroke in Advanced Chronic Kidney Disease Patients Transitioning to Dialysis

2021 ◽  
pp. 1-9
Author(s):  
Ankur A. Dashputre ◽  
Keiichi Sumida ◽  
Fridtjof Thomas ◽  
Justin Gatwood ◽  
Oguz Akbilgic ◽  
...  
Keyword(s):  
Chronic Kidney Disease ◽  
Ischemic Stroke ◽  
Kidney Disease ◽  
Lower Risk ◽  
Chronic Exposure ◽  
Cox Regression ◽  
Acute Exposure ◽  
Continuous Exposure ◽  
Advanced Chronic Kidney Disease

<b><i>Introduction:</i></b> Hypo- and hyperkalemia are associated with a higher risk of ischemic stroke. However, this association has not been examined in an advanced chronic kidney disease (CKD) population. <b><i>Methods:</i></b> From among 102,477 US veterans transitioning to dialysis between 2007 and 2015, 21,357 patients with 2 pre-dialysis outpatient estimated glomerular filtration rates &#x3c;30 mL/min/1.73 m<sup>2</sup> 90–365 days apart and at least 1 potassium (K) each in the baseline and follow-up period were identified. We separately examined the association of both baseline time-averaged K (chronic exposure) and time-updated K (acute exposure) treated as categorized (hypokalemia [K &#x3c;3.5 mEq/L] and hyperkalemia [K &#x3e;5.5 mEq/L] vs. referent [3.5–5.5 mEq/L]) and continuous exposure with time to the first ischemic stroke event prior to dialysis initiation using multivariable-adjusted Cox regression models. <b><i>Results:</i></b> A total of 2,638 (12.4%) ischemic stroke events (crude event rate 41.9 per 1,000 patient years; 95% confidence interval [CI] 40.4–43.6) over a median (Q<sub>1</sub>–Q<sub>3</sub>) follow-up time of 2.56 (1.59–3.89) years were observed. The baseline time-averaged K category of hypokalemia (adjusted hazard ratio [aHR], 95% CI: 1.35, 1.01–1.81) was marginally associated with a significantly higher risk of ischemic stroke. However, time-updated hyperkalemia was associated with a significantly lower risk of ischemic stroke (aHR, 95% CI: 0.82, 0.68–0.98). The exposure-outcome relationship remained consistent when using continuous K levels for both the exposures. <b><i>Discussion/Conclusion:</i></b> In patients with advanced CKD, hypokalemia (chronic exposure) was associated with a higher risk of ischemic stroke, whereas hyperkalemia (acute exposure) was associated with a lower risk of ischemic stroke. Further studies in this population are needed to explore the mechanisms underlying these associations.

scholarly journals Vasoactive Effects of Acute Ergot Exposure in Sheep

Toxins ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 291
Author(s):  
Rossalin Yonpiam ◽  
Jair Gobbet ◽  
Ashok Jadhav ◽  
Kaushik Desai ◽  
Barry Blakley ◽  
...  
Keyword(s):  
Single Dose ◽  
Chronic Exposure ◽  
Contractile Response ◽  
Ergot Alkaloids ◽  
Acute Exposure ◽  
Control Group ◽  
Vascular Effects ◽  
Adrenergic Antagonist ◽  
Vascular Sensitivity ◽  
Dose Dependent

Ergotism is a common and increasing problem in Saskatchewan’s livestock. Chronic exposure to low concentrations of ergot alkaloids is known to cause severe arterial vasoconstriction and gangrene through the activation of adrenergic and serotonergic receptors on vascular smooth muscles. The acute vascular effects of a single oral dose with high-level exposure to ergot alkaloids remain unknown and are examined in this study. This study had two main objectives; the first was to evaluate the role of α1-adrenergic receptors in mediating the acute vasocontractile response after single-dose exposure in sheep. The second was to examine whether terazosin (TE) could abolish the vascular contractile effects of ergot alkaloids. Twelve adult female sheep were randomly placed into control and exposure groups (n = 6/group). Ergot sclerotia were collected and finely ground. The concentrations of six ergot alkaloids (ergocornine, ergocristine, ergocryptine, ergometrine, ergosine, and ergotamine) were determined using HPLC/MS at Prairie Diagnostic Services Inc., (Saskatoon, SK, Canada). Each ewe within the treatment group received a single oral treatment of ground ergot sclerotia at a dose of 600 µg/kg BW (total ergot) while each ewe in the control group received water. Animals were euthanized 12 h after the treatment, and the pedal artery (dorsal metatarsal III artery) from the left hind limb from each animal was carefully dissected and mounted in an isolated tissue bath. The vascular contractile response to phenylephrine (PE) (α1-adrenergic agonist) was compared between the two groups before and after TE (α1-adrenergic antagonist) treatment. Acute exposure to ergot alkaloids resulted in a 38% increase in vascular sensitivity to PE compared to control (Ctl EC50 = 1.74 × 10−6 M; Exp EC50 = 1.079 × 10−6 M, p = 0.046). TE treatment resulted in a significant dose-dependent increase in EC50 in both exposure and control groups (p < 0.05 for all treatments). Surprisingly, TE effect was significantly more pronounced in the ergot exposed group compared to the control group at two of the three concentrations of TE (TE 30 nM, p = 0.36; TE 100 nM, p < 0.001; TE 300 nM, p < 0.001). Similar to chronic exposure, acute exposure to ergot alkaloids results in increased vascular sensitivity to PE. TE is a more potent dose-dependent antagonist for the PE contractile response in sheep exposed to ergot compared to the control group. This study may indicate that the dry gangrene seen in sheep, and likely other species, might be related to the activation of α1-adrenergic receptor. This effect may be reversed using TE, especially at early stages of the disease before cell death occurs. This study may also indicate that acute-single dose exposure scenario may be useful in the study of vascular effects of ergot alkaloids.

Influence of cycloheximide on the lung

1975 ◽  
Vol 38 (4) ◽  
pp. 623-629 ◽  
Author(s):  
D. B. Gail ◽  
G. D. Massaro ◽  
D. Massaro
Keyword(s):  
Oxygen Consumption ◽  
Surface Density ◽  
Time Course ◽  
Lamellar Body ◽  
Lamellar Bodies ◽  
Cytoplasmic Area ◽  
The Right

We examined the time course of the influence of cycloheximide on descending pressure-volume curves of excised lungs and on protein and lecithin synthesis and oxygen consumption by lung slices. We also looked at the influence of cycloheximide on granular pneumocyte ultrastructure. Excised lungs from cycloheximide-treated animals are more compliant than controls. After ventilation with air, lungs from control and cycloheximide animals show increased retractive forces and a shift to the right of the deflation P-V curve. Incubation at 38 degrees C for 30 min reverses these changes in control lungs, but not in lungs from cycloheximide-treated rabbits. There is no change in liquid delfation P-V curves after cycloheximide. Cycloheximide causes an immediate decrease of 50% in incorporation of radioactive leucine into protein by lung slices. Incorporation of radioactive palmitate into lecithin and oxygen consumption are also decreased by 50% 6 h after cycloheximide. Lamellar bodies in granular pneumocytes are smaller after cycloheximide. Cycloheximide causes a significant increase in the surface density of the lamellar body envelope. Cytoplasmic area of granular pneumocytes is increased after cycloheximide.

Effect of exposure to low temperature on normal and iron-deficient subjects

1984 ◽  
Vol 246 (3) ◽  
pp. R380-R383 ◽  
Author(s):  
C. Martinez-Torres ◽  
L. Cubeddu ◽  
E. Dillmann ◽  
G. L. Brengelmann ◽  
I. Leets ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Cold Exposure ◽  
Initial Temperature ◽  
Iron Status ◽  
Hemoglobin Concentration ◽  
Normal Subjects ◽  
Plasma Norepinephrine ◽  
Oral Temperature ◽  
The Third ◽  
Iron Deficient

Twenty-one Venezuelan peasants were segregated into three groups on the basis of measurements of iron status: seven normal subjects, six iron-deficient subjects with normal hemoglobin and eight iron-deficient subjects with a hemoglobin concentration of less than 9 g/dl. All subjects were placed in a water bath at an initial temperature of 36 degrees C. The water temperature was then rapidly lowered to 28 degrees C, and observations were made over the period of 1 h. Mean oral temperature of the first group fell 0.2, the second group 0.5, and the third group 0.9 degrees C. Mean plasma norepinephrine levels in both groups of iron-deficient subjects were significantly higher at 36 degrees C and during cold exposure compared with control subjects. Oxygen consumption was also significantly increased in both groups of iron-deficient subjects after cold exposure.

Body temperature regulation and oxygen consumption in young chicks fed thyroid hormone

1991 ◽  
Vol 69 (7) ◽  
pp. 1842-1847 ◽  
Author(s):  
Gregory K. Snyder ◽  
Joseph R. Coelho ◽  
Dalan R. Jensen
Keyword(s):  
Oxygen Consumption ◽  
Thyroid Hormone ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Cold Exposure ◽  
Elevated Serum ◽  
Body Temperatures ◽  
Serum Thyroid Hormone ◽  
Regulate Body Temperature ◽  
Young Chicks

In chicks the ability to regulate body temperature to adult levels develops during the first 2 weeks of life. We examined whether the ability of young chicks to regulate body temperature is increased by elevated levels of the thyroid hormone 3,3′5-triiodothyronine. By 13 days following hatch, body temperatures of chicks were not significantly different from those expected for adult birds. Furthermore, at an ambient temperature of 10 °C, 13-day-old control chicks were able to maintain body temperature, and elevated serum thyroid hormone levels did not increase rates of oxygen consumption or body temperature above control values. Six-day-old chicks had body temperatures that were significantly lower than those of the 13-day-old chicks and were not able to regulate body temperature when exposed to an ambient temperature of 10 °C. On the other hand, 6-day-old chicks with elevated serum thyroid hormone had significantly higher rates of oxygen consumption than 6-day-old control chicks, and were able to maintain constant body temperatures during cold exposure. The increased oxygen consumption rates and improved ability to regulate body temperature during cold exposure were correlated with increased citrate synthase activity in skeletal muscle. Our results support the argument that thyroid hormones play an important role in the development of thermoregulatory ability in neonate birds by stimulating enzyme activities associated with aerobic metabolism.

Tolerance of estrogen-treated rats to acute cold exposure

1979 ◽  
Vol 47 (1) ◽  
pp. 59-66 ◽  
Author(s):  
M. J. Fregly ◽  
D. L. Kelleher ◽  
D. J. Black
Keyword(s):  
Oxygen Consumption ◽  
Cold Exposure ◽  
Previous Experiment ◽  
Female Rats ◽  
Control Group ◽  
Maximal Rate ◽  
Acute Cold Exposure ◽  
Exposure To Cold ◽  
Rate Of Oxygen Consumption ◽  
Rate Of Cooling

Female rats treated chronically with ethynylestradiol (36 micrograms/kg per day) alone, and in combination with the progestational agent, norethynodrel (253 micrograms/kg per day), cooled significantly faster than controls when lightly restrained and exposed to air at 5 degrees C. Rate of cooling of rats given only norethynodrel was similar to that of the control group. In other studies, rate of oxygen consumption was determined for all groups during acute exposure to cold (14 degrees C). All estrogen-treated groups achieved the same maximal rate of oxygen consumption as control and norethynodrel-treated groups during cold exposure, but cooled significantly faster. Two groups of female rats were treated chronically with ethynylestradiol at two separate doses (36 and 61 micrograms/kg per day). An untreated group served as controls. Rate of oxygen consumption of all animals were measured during restraint and exposure to cold (18 degrees C). The estrogen-treated groups again achieved the same maximal rate of oxygen consumption as the control group, but also cooled significantly faster despite the fact that the cold stress was less severe than in the previous experiment. That estrogen-treated rats cooled faster than controls in both studies despite achieving a maximal rate of heat production which did not differ from controls suggests that reduced cold tolerance of estrogen-treated rats may be related to increased heat loss.

Regulation of the Size and Distribution of Agrin-Induced Postsynaptic-like Apparatus in Adult Skeletal Muscle by Electrical Muscle Activity

1999 ◽  
Vol 13 (3) ◽  
pp. 207-217 ◽  
Author(s):  
Iacob Mathiesen ◽  
Mendell Rimer ◽  
Omid Ashtari ◽  
Ilana Cohen ◽  
Uel J. McMahan ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Activity ◽  
Adult Skeletal Muscle ◽  
Electrical Muscle

scholarly journals Genotoxic and Histopathological Effects of Chlorpyrifos on African Catfish, C. gariepinus and Ameliorative Potentials of Ackee Apple, blighia sapida Seed

2018 ◽  
Vol 6 (1) ◽  
pp. 1 ◽  
Author(s):  
Oluyinka Iyiolai ◽  
A. A. Adeagbo ◽  
W. S. Weliange ◽  
S. I. Abdulkareem ◽  
Anifowoshe T. Abass ◽  
...  
Keyword(s):  
Chronic Exposure ◽  
Clarias Gariepinus ◽  
Aquatic Organisms ◽  
Acute Exposure ◽  
Histopathological Analysis ◽  
African Catfish ◽  
Dependent Manner ◽  
Dose Dependent ◽  
Histopathological Effects ◽  
Positive Controls

Chlorpyrifos (CPF) is a very toxic pesticide commonly used for controlling agriculturally important pests. The present study investigates DNA damaging effects of CPF on Clarias gariepinus was assessed using genetic assays. Fish were exposed to varying concentrations of CPF (100ppm, 200ppm and 300ppm) at 96 hours (acute exposure). LC50 of the pesticide was found to be 120ppm and one-tenth of the LC50 (12ppm) was taken for the chronic exposure. Distilled water and colchicine were used as negative and positive controls respectively. After 28 days of chronic exposure, fish were fed with inclusion of B. sapida seed (powder) for 14 days. Liver and gills of the fish were removed following 96h exposure, days 7, 14 and 28 of the chronic exposure as well as after the period of amelioration (14 days) for CA assay and histopathological analysis. The results of CA assay showed statistically significant (p ˂ 0.05) increase in CA in a dose-dependent manner for all the exposed groups after acute exposure and time dependent after chronic exposure. Also, this study showed that CPF can potentially induce genotoxic and histopathological changes in fish and other aquatic organisms.

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