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PubMed1997

Electromyographic (EMG) study of cold shivering in the chronic spinal dog.

Cold shivering in six chronic spinal dogs (T9-10), which became capable of weight-bearing standing and/or walking with their hindlimbs, was studied by electromyography (EMG). In the forequarters, EMG activities in the form of grouping discharges (GD) accompanied by visible tremor (VT) were induced at an ambient temperature of 15 degrees C in all the dogs. In the hindquarters, GD with VT were induced at 3 degrees C in one dog. Although GD with VT were not induced in in the remaining dogs, GD without VT were produced by additional cutaneous stimuli to the hindquarters at 3 degrees C. These stimuli never produced GD in the hindquarters at room temperature. Though the mean frequency of GD in the hindquarters was lower than that in the forequarters, the range of the frequency in the hindquarters was much the same as that in the forequarters. During the experiment, the drop in rectal temperature was less than 0.6 degrees C in all of the dogs. These findings suggest that the chronically isolated spinal cord is responsible for cold shivering, while its excitability to cold exposure is less than that of the spinal cord governed by the supraspinal center.

Animals↗

PubMed1982

[Thermogenic shivering in the anesthetized rat].

In normal pentobarbital-anaesthetized rats (20 mg/kg, i.p.), Ketanserine (2.5 to 10 mg/kg, i.v.) increases the temperature of the paw skin and decreases the central one. A strong thermogenetic shivering appears when central temperature falls below 35 degrees C. This shivering is a specific characteristics of Ketanserine activity, probably related to its fixation on 5-HT2 central receptors.

Animals↗

PubMed1999

Postnatal changes in regional blood flow during cold-induced shivering in sow-reared piglets.

To determine whether newborn pigs are able to display adequate cardiovascular adjustments favouring shivering thermogenesis in skeletal muscles soon after birth, regional blood flow and fractional distribution of cardiac output were determined in 1-day-old (n = 6) and 5-day-old (n = 6) conscious piglets at thermal neutrality and during cold exposure, using coloured microspheres. Five-day-old piglets stayed with the sow before the experiment. The cold challenge was designed to induce a similar increase (approximately +90%) in heat production at both ages. Skeletal muscle blood flow increased with both age (p < 0.05) and cold exposure (p < 0.001), with the effect of cold being more pronounced in 5-day-old piglets than in 1-day-old piglets (+60%, p < 0.05). The difference between individual muscles increased with age, with fractional blood flow being 41% higher in rhomboideus than in longissimus thoracis muscle during cold exposure in 5-day-old piglets (p < 0.05). Cardiac output was similar at both ages and increased by 23% in the cold (p < 0.001). At 1 day of age, there was no redistribution of cardiac output among the internal organs during the cold challenge, while at 5 days of age, the increase in muscle fractional blood flow was associated with a reduction (p < 0.05) in the fraction of cardiac output reaching the skin (-24%), the small intestine (-21%), and the liver (-20%). In conclusion, these results suggest that there is a rapid postnatal improvement of cardiovascular adjustments favouring blood perfusion and probably heat production during cold-induced shivering in the most oxidative muscles studied. This cardiovascular response may play a role in the postnatal enhancement of thermoregulation in piglets.

Adipose Tissue↗

PubMed1976

[The effect of 5-hydroxytryptophan on shivering thermogenesis].

Studies carried out on ground squirrels showed active warming of these animals during arousal from hibernation to be closely connected with intensification of the shivering thermogenesis. The intraabdominal administration of 5-oxytryptophane, a precursor of serotonin clearly suppressed the shivering thermogenesis in arising ground squirrels and slowed down their warming.

5-Hydroxytryptophan↗

PubMed1991

The shivering response in animals and man.

The physiological response to body cooling may be regarded as a homeostatic response embracing the concept of negative feedback. The metabolic response to falling body temperature is normally both appropriate and adequate. However, there are reports of inadequate or absent responses to body cooling and of non-febrile animals shivering at elevated body temperature. The reasons for these paradoxical findings are not fully understood, particularly since the controller of body temperature receives the largest proportion of its thermal afferent information from temperature sensors located within the body core. During anaesthesia and certain phases of sleep the shivering response to hypothermia may be impaired. It also appears that other factors such as the rate of cooling and disturbances of the circadian machinery (altered light conditions, phase shifting of activity patterns) may be of importance. These factors are relevant for people working in the arctic, especially since many of them are shift workers.

Animals↗

PubMed1991

[Use of magnesium sulfate for controlling postoperative shivering].

In intravenous administration of magnesium sulphate, the postoperative shivering was cupped off in 87.8% of the patients. The mean effective dosage of the preparation was 32.2 mg/kg of body weight. In rapid intravenous administration of the preparation, in 3% of the patients, the nausea and vomiting+ occurred. Hypotension (3% of cases) and ++re-curarization of the mandibular muscles (3%) were eliminated by means of the intravenous administration of calcium chloride. Cupping off the shivering permitted to prevent the hypothermal reaction after the operation and narcosis.

Adult↗

PubMed1990

Shivering. A clinical nursing problem.

Shivering is a common but complex phenomenon that occurs in many patient care situations. Its metabolic costs and cardiorespiratory consequences should not be underestimated, particularly for the seriously ill, debilitated, or elderly patient. Using a conceptual frame of reference for assessment and action, independent and collaborative actions can be planned to reduce the energy expenditure, distress, and loss of control imposed by severe shivering.

Humans↗

PubMed1986

Intravenous fluid temperature, shivering, and the parturient.

The effect of warmed vs room-temperature intravenous fluids is examined for decreasing shivering in parturients undergoing epidural anesthesia for elective cesarean sections. Forty-four women were studied, 22 receiving warmed and 22 receiving room-temperature fluid therapy for preblock prophylaxis of hypotension and intraoperative maintenance and replacement. Of those given room-temperature balanced salt solutions, 64% shivered, as opposed to 14% in the warm fluid group, an observation significant at less than a P of 0.005 by chi 2-analysis.

Adult↗

PubMed1980

[Bioelectrical activity of limb muscles during shivering while stimulating the vestibular apparatus].

The effects of caloric and electric stimulation of the vestibular receptors on the EMG activity of limb muscles in anesthetized cats during cold-induced shivering involved flexor muscles alone. Both types of stimulation suppressed bioelectrical activity, more effectivey in the ipsilateral muscles. The suppression of shivering activity seems to be due to the increased inhibitory effect of descending labyrinth pathways on the function of flexor motoneurons.

Animals↗

PubMed1981

Postoperative hypothermia in adults: relationship of age, anesthesia, and shivering to rewarming.

Frequency, magnitude, and duration of hypothermia (core body temperature less than 36.0 C) in the recovery room (RR) were determined in 198 adults. In addition, the influence of age, anesthetic technique, and shivering on the rewarming process was assessed. Tympanic membrane temperatures were recorded on admission to the RR and every 15 minutes thereafter until discharge from the RR. Sixty percent of the subjects had temperatures less than 36.0 C on admission to the RR. Elderly subjects (greater than or equal to 60 yr) had lower RR admission and discharge temperatures and experienced longer duration of hypothermia than did younger patients. General anesthesia was associated with a significantly more rapid rate of increase in postoperative temperature and a shorter duration of hypothermia than was regional anesthesia. The incidence of shivering and the incidence of hypothermia were significantly related 30 and 45 minutes after admission to the RR. Duration of hypothermia varied with different operative procedures.

Adolescent↗

PubMedDate not supplied

Postoperative shivering.

Shivering is common during recovery from anaesthesia. Factors in the aetiology include the use of volatile anaesthetic agents, prolonged anaesthesia, gender and age. The relationship between postoperative shivering and thermoregulation is not clear. Management should include measurement of the patient's temperature.

Anesthesia, General↗

PubMed1998

A minimal human MBP promoter-lacZ transgene is appropriately regulated in developing brain and after optic enucleation, but not in shiverer mutant mice.

Previous studies, both in vitro and in vivo, suggest that small portions of the mouse myelin basic protein (MBP) promoter are sufficient to activate regulated expression of MBP. To confirm our previous in vitro studies, we prepared transgenic mice with short regions of the human MBP promoter fused to the lacZ reporter gene. We found that 750 nucleotides of the proximal human MBP promoter is sufficient to activate oligodendrocyte-specific, developmentally regulated expression of lacZ in three independent lines. This promoter, however, does not activate expression of lacZ in Schwann cells in peripheral nerve or in adult mouse brain. The relative levels of beta-galactosidase specific activity, mRNA, and transcription parallel those of MBP mRNA during myelinogenesis. Thus, we exploited this transgene as a quantitative tool to evaluate the response to stimuli known to affect myelination. Transgene expression is reduced 75 % after optic enucleation, as previously reported for levels of MBP mRNA, indicating that axons signal to this portion of the proximal MBP promoter to fully activate MBP expression during myelinogenesis. Instead, in adult shiverer mice, another setting in which MBP transcription is modulated, transgene expression is not increased, in contrast to the increased transcriptional activation of MBP previously reported in these mice. These data suggest that the regulatory region that mediates transcriptional activation of the MBP gene is modular, since discrete subregions are required for activation in Schwann cells, during myelinogenesis in oligodendrocytes, during maintenance myelination in adult brain, and in the dysmyelinating mutant shiverer mouse.

Animals↗

PubMed1980

Peripheral myelin in the mouse mutant Shiverer.

The mouse mutant Shiverer has been shown previously to lack myelin basic protein and other myelin proteins in both the peripheral and central nervous systems. Examination by electron microscopy shows that the peripheral nervous system, in contrast to the markedly abnormal central nervous system, is grossly normal. Myelin sheaths are of the usual thickness and exhibit normal periodic structure consisting of alternating major dense and intermediate lines. Subtle abnormalities do occur, however, consisting of increased numbers of cytoplasm-containing lamellae, aberrant terminations of myelin lamellae in internodal regions, invagination of the axon by the inner tongue of the myelin sheath, myelin debris in both axon and Schwann cells, and disruption of outer myelin lamellae. Such changes have been seen previously in various types of neuropathy and are not pathognomonic of the Shiverer mutation. Despite the absence of myelin basic protein, the peripheral manifestations of this gene are relatively minor and probably not severe enough to compromise peripheral nerve function significantly.

Animals↗

PubMed1991

Tracing transplanted oligodendrocytes during migration and maturation in the shiverer mouse brain.

Fragments of neural tissue from normal newborn mouse were stained with Hoechst 33342 dye before transplantation into the newborn shiverer mouse brain. Combination of this technique with immunohistochemistry demonstrated that, after transplantation, these cells are able to survive as long as unstained cells and to myelinate in the shiverer mouse host brain. Stained cells express the normal sequence of differentiation in terms of chronology of differentiation marker expression [04, galactocerebroside (GalC), myelin basic protein (MBP)], as normal cell do in situ. It has thus been possible by this technique to show the migration pathways of transplanted cells and to correlate them with the expression of specific markers: long distance migration along white matter axonal pathways occurs when cells are o4-positive, GalC-negative. By contrast, only GalC-positive cells are able to migrate across the grey matter in the absence of radial glia. Finally, it has been possible to propose a migration and differentiation sequence of these cells, suggesting that MBP-positive oligodendrocytes divide after migration in the target zone.

Animals↗

PubMed1986

Myelin-associated glycoprotein (MAG) in the CNS of adult shiverer (Shi/Shi) mice.

Brain fractions of adult control (+/+) and shiverer (Shi/Shi) mice were investigated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting. Immunostaining with specific antisera against rat brain myelin-associated glycoprotein (MAG) was detected at about the 96-kD region of gels in electrophoresed samples of the total homogenate, low-speed supernatant fraction, and low- and high-speed sedimentable portions of brain from +/+ mice. Reduced immunostaining was observed in the corresponding samples of brain fractions from Shi/Shi mice. The cerebrum, cerebellum, and medulla of +/+ and Shi/Shi mice were examined immunocytochemically for MAG on paraffin-embedded sections. Periaxonal immunostaining for MAG was observed in all the regions and the highest concentrations were in the corpus callosum, in the central cores of cerebellar folia, and in the medulla. Patterns of distribution were similar in +/+ and Shi/Shi mice, although the density of immunostaining around individual axons and the number of immunostained axons were significantly reduced in Shi/Shi mice. In addition, the three brain regions of Shi/Shi mice exhibited oligodendrocyte-like cells that contained immunostaining for MAG in the cytoplasm and periphery of their perikarya. This type of immunostained cell was not observed in +/+ mice. In this study, immunoblotting with brain fractions and immunocytochemistry revealed strong evidence for reduced concentrations of MAG in the CNS of Shi/Shi mice compared to control mice. In addition, there is immunocytochemical evidence for abnormal accumulation of MAG in perikarya of oligodendroglial-like cells, suggesting the possibility of a transport block for myelin proteins in the shiverer mutant.

Animals↗

PubMed1991

Oligodendrocytes and myelin sheaths in normal, quaking and shiverer brains are enriched in iron.

Early studies employing iron histochemical techniques found a spatially restricted distribution of oligodendrocytes and myelin enriched in iron. In particular, oligodendrocytes and myelin positively stained for iron were found in sparsely myelinated brain regions but not in densely myelinated tracts. Subsequent studies modified the iron histochemical technique and demonstrated that oligodendrocytes and myelin were stained in densely myelinated brain regions but the staining occurred in patches rather than uniformly throughout densely myelinated tracts. This study further modified the iron histochemistry technique to establish that oligodendrocytes and myelin are enriched in iron throughout densely myelinated tracts. This finding supports biochemical studies that detected high levels of iron in white matter (Hallgren and Sourander, J Neurochem 3:41-51, 1958) and myelin fractions of brain homogenates (Rajan et al., Life Sci 18:423-432, 1976). Thus, this histochemical study and earlier biochemical studies indicate that white matter is a major site of iron concentration within the brain. The present study also examined the distribution of iron in oligodendrocytes and myelin from the dysmyelinating mutant mice quaking and shiverer. Results from these studies demonstrate that oligodendrocytes and myelin are enriched in iron in both quaking and shiverer brains. An unexpected finding was an intense staining of oval structures within the oligodendrocyte cytoplasm. This result indicates a concentration of iron in these structures and may be important for understanding how high concentrations of iron are processed by oligodendrocytes.

Animals↗

PubMed1987

(Na+ + K+)-adenosinetriphosphatase in the brain of Shiverer (Shi/Shi) mice.

The myelin-deficient Shiverer (Shi/Shi) mutant mouse may be a useful model in assessing the dependence of brain (Na+ + K+)-ATPase concentration and composition on myelin membrane formation. Brain microsomal membranes from age-matched control (+/+) and Shiverer (Shi/Shi) mice were fractionated by differential centrifugation and sucrose gradient sedimentation. No reduction in (Na+ + K+)-ATPase specific activity was measured in whole homogenates, high- and low-speed fractions or gradient fractions from brains of Shi/Shi mice as compared to those of +/+ mice. In addition, sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting with antisera specific for mouse brain (Na+ + K+)-ATPase revealed no significant difference in catalytic subunit composition between fractions of +/+ and Shi/Shi brains. The similar results obtained for both +/+ and myelin-deficient Shi/Shi mice suggest that myelin contributes little to total brain (Na+ + K+)-ATPase.

Animals↗

PubMed1987

Reduced S-adenosylmethionine:protein-lysine N-methyltransferase activity (protein methylase III) in shiverer mutant mouse brain.

Mice with the dysmyelinating mutation shiverer were studied by measuring the activity of two protein methylases and myelin marker enzymes in the brain. It was observed that S-adenosylmethionine:protein-lysine N-methyltransferase (protein methylase III, EC. 2.1.1.43) activity is significantly reduced in phenotypically affected homozygous shiverer (shi/shi) mutant mouse brain compared to the unaffected heterozygous littermate brain. This reduction in enzyme activity is manifested mainly by reduced formation of trimethyllysine during the in vitro methylation of histone. In contrast, myelin marker enzymes such as 2',3'-cyclic nucleotide 3'-phosphohydrolase and 5'-nucleotidase as well as S-adenosyl-methionine:protein-carboxyl O-methyltransferase (protein methylase II, EC. 2.1.1.24) activities were not significantly affected in these strains of mice.

5'-Nucleotidase↗