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1.
Sleep ; 11(3): 233-41, 1988 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-3399777

RESUMO

Experiments were done to determine the influence of arousal from sleep and lung inflation on heart rate following upper airway obstruction in lambs. Ten lambs were anesthetized and instrumented for recordings of electrocorticogram, electro-oculogram, nuchal and diaphragm electromyograms, and measurements of systemic arterial blood pressure and arterial hemoglobin oxygen saturation (fiberoptic catheter oximeter). A tracheotomy was done and a fenestrated tracheostomy tube was placed in the trachea. A 5F balloon-tipped catheter was inserted into the tube so that the airway could be obstructed by inflating the balloon. No sooner than 3 days after surgery, measurements were made during a control period of normal tidal respiration, during upper airway obstruction immediately before arousal, during upper airway obstruction immediately after arousal, and following the first lung inflation. A total of 39 epochs of quiet sleep and 33 epochs of active sleep were obtained. Heart rate and oxygen saturation decreased (p less than 0.05) during upper airway obstruction in quiet sleep and active sleep. Arousal from sleep did not significantly alter heart rate during continued upper airway obstruction. However, heart rate quickly returned toward control levels following the first lung inflation despite continued oxygen desaturation. These results provide evidence that the abrupt tachycardia following an apneic episode is related to lung inflation rather than to the arousal response per se.


Assuntos
Obstrução das Vias Respiratórias/fisiopatologia , Nível de Alerta/fisiologia , Frequência Cardíaca , Pulmão/fisiopatologia , Síndromes da Apneia do Sono/fisiopatologia , Animais , Oxigênio/sangue , Ovinos , Fases do Sono/fisiologia
2.
Sleep ; 8(3): 254-60, 1985.
Artigo em Inglês | MEDLINE | ID: mdl-4048741

RESUMO

We investigated the effect of sleep on blood pressure control in seven lambs aged 10-14 days. Each lamb had previously been anesthetized and instrumented for measurements of electrocorticogram, electron-oculogram, nuchal and diaphragm electromyograms, pulmonary blood flow (electromagnetic flow transducer), and aortic and pulmonic blood pressure. The lambs were allowed to recover from surgery at least 3 days before they were studied. Measurements were made at the highest and lowest mean aortic pressure during quiet wakefulness, quiet sleep, and active sleep. The lowest values of mean aortic pressure progressively decreased as the animals went from quiet wakefulness to quiet sleep to active sleep. Mean aortic pressure was most variable during active sleep. During active sleep, transient hypertensive episodes were superimposed upon a tonic hypotensive phase. During the transient hypertensive episodes in active sleep, changes in mean aortic pressure were primarily caused by an increase in systemic vascular resistance rather than by changes in cardiac output. Heart rate was always lower during active sleep than during quiet wakefulness or quiet sleep. These results provide evidence that sleep state has a marked influence on blood pressure control in lambs.


Assuntos
Pressão Sanguínea , Sono/fisiologia , Animais , Débito Cardíaco , Frequência Cardíaca , Ovinos , Fases do Sono/fisiologia , Resistência Vascular , Vigília/fisiologia
3.
Sleep ; 18(6): 439-45, 1995 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-7481415

RESUMO

The study of sleep is an important and rapidly expanding area of research that generates large bodies of data. Manual scoring of sleep states from polygraph recordings is a laborious and often subjective task. Even when care is taken, the opportunity for disagreement between investigators and between laboratories remains great. To avoid this difficulty and to reduce the subjectivity of sleep state scoring we have designed a computer-based algorithm for scoring sleep state in the lamb. The algorithm underlying the system relies upon spectral analysis of the electrocorticogram and upon amplitude analysis of the electrooculogram and nuchal electromyogram. Partitioning the spectral power observed within the electrocorticogram (1-4 Hz frequency range) reliably identifies deep quiet sleep. Wakefulness and active sleep are then identified based upon threshold crossings of the electrooculogram and of the electromyogram of the nuchal muscles. We compared the sleep states returned by the algorithm to those scored visually by trained personnel for 1 hour of data collected from each of five 19-day-old lambs. There was good agreement between the two methods of scoring sleep. The percents agreement between the algorithm-derived scores and visual scores were as follows: active wakefulness 97%, quiet wakefulness 87%, quite sleep 85% and phasic active sleep 82%. As such, our algorithm provides a fast, reliable and objective method for scoring sleep state in the young lamb.


Assuntos
Animais Recém-Nascidos/fisiologia , Polissonografia/instrumentação , Ovinos/fisiologia , Sono/fisiologia , Algoritmos , Animais , Eletroencefalografia , Eletromiografia , Eletroculografia , Ratos , Fases do Sono/fisiologia , Software , Vigília/fisiologia
4.
Chest ; 94(2): 325-8, 1988 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-3396411

RESUMO

Respiratory inductive plethysmography (RIP) can measure breathing patterns noninvasively. Calibration is required for rib cage and abdomen transducers utilizing breaths with different compartment contribution correlated with tidal volume measured by integrated pneumotachography (PNT). This study was performed to determine if RIP remains accurate during sleep states following calibration in the quietly awake state. We used our single position graphic calibration technique (SPG) to calculate gain factors in seven tracheostomized lambs. Validation of gain factors was accomplished by comparing tidal volume obtained simultaneously by RIP and PNT during quiet wakefulness (QW), quiet sleep (QS) and active sleep (AS). Results of the study showed that RIP was accurately calibrated during QW. Accuracy was decreased during QS and AS.


Assuntos
Medidas de Volume Pulmonar , Pletismografia/normas , Respiração , Sono/fisiologia , Volume de Ventilação Pulmonar , Animais , Calibragem , Pletismografia/métodos , Ventilação Pulmonar , Ovinos
5.
J Thorac Cardiovasc Surg ; 89(1): 63-70, 1985 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-3965817

RESUMO

Man's response to clinical doses of protamine is highly variable. We investigated the influence of circulating heparin in nine swine (mean age 6 weeks, weight 10 kg). Through a sternotomy we implanted an electromagnetic flow probe around the pulmonary artery for cardiac output determination and catheters into the ascending aorta, pulmonary artery, right atrium, and left atrium for pressure monitoring. Each animal was allowed to recover and was studied awake on 3 consecutive days. Protamine, 3 mg/kg, beef lung heparin, 300 U/kg, and pork mucosal heparin, 300 U/kg, followed by protamine, were given in rotation by intravenous bolus. Protamine alone had no effect. Beef lung heparin followed by protamine induced a marked increase in pulmonary artery pressure (mean 38 +/- 3 to 51 +/- 5 mm Hg in 3 minutes). Pulmonary vascular resistance doubled (mean 0.12 +/- 0.01 to 0.23 +/- 0.04 R within 4 minutes), returning to normal within 15 minutes. Cardiac index and aortic pressure changed minimally. Pork mucosal heparin followed by protamine induced a similar but greater increase in mean pulmonary arterial pressure; however, cardiac index fell significantly (p less than 0.05, 207 +/- 16 to 117 +/- 16 ml/kg/min-1 at 1 minute) despite a regular rhythm and adequate left atrial filling pressure. Thus cardiac contractility was depressed. Systemic hypotension occurred in three of nine pigs. Both mean pulmonary vascular resistance and systemic vascular resistance increased (0.12 +/- 0.01 to 0.67 +/- 0.25 R and 0.40 +/- 0.04 to 1.09 +/- 0.25 R, respectively), significantly (p less than 0.05) more with pork than beef heparin. These data demonstrate that cardiovascular response to protamine neutralization varies significantly in regard to the type of heparin used. Furthermore, circulating heparin is required to produce those effects previously attributed to protamine alone.


Assuntos
Hemodinâmica/efeitos dos fármacos , Heparina/sangue , Protaminas/farmacologia , Animais , Pressão Sanguínea/efeitos dos fármacos , Débito Cardíaco/efeitos dos fármacos , Bovinos , Pulmão/irrigação sanguínea , Pressão Propulsora Pulmonar/efeitos dos fármacos , Suínos , Fatores de Tempo , Resistência Vascular/efeitos dos fármacos
6.
J Appl Physiol (1985) ; 82(5): 1406-10, 1997 May.
Artigo em Inglês | MEDLINE | ID: mdl-9134885

RESUMO

Exposure of a rat to a novel environment (e.g., a simulated open field) induces a transient increase in body-core temperature, which is often called stress-induced hyperthermia. Although pregnancy is known to influence thermoregulatory control, its effect on stress-induced hyperthermia is unknown. Therefore, 24 Sprague-Dawley rats (8 nonpregnant and 16 pregnant) were studied to test the hypothesis that pregnancy would alter the development of stress-induced hyperthermia after exposure to a simulated open field. Body-core temperature index increased significantly after exposure to a simulated open field in nonpregnant and gestation day-10 rats but not in gestation day-15 and day-20 rats. Thus our data provide evidence that pregnancy influences the body-core temperature response of rats exposed to a simulated open field in a gestation-dependent fashion. The functional consequences as well as the mechanisms involved remain to be determined.


Assuntos
Regulação da Temperatura Corporal/fisiologia , Prenhez/fisiologia , Estresse Psicológico/fisiopatologia , Animais , Feminino , Febre/fisiopatologia , Análise Multivariada , Gravidez , Ratos , Ratos Sprague-Dawley
7.
J Appl Physiol (1985) ; 82(5): 1453-8, 1997 May.
Artigo em Inglês | MEDLINE | ID: mdl-9134892

RESUMO

Rats near term of pregnancy have an attenuated febrile response to intracerebroventricular (ICV) injection of prostaglandin E1 (PGE1) when they are studied at an ambient temperature below their thermoneutral zone. Given that nonshivering thermogenesis in brown adipose tissue is impaired in rodents near term of pregnancy, it is possible that the attenuated febrile response is forced by impairment of this component of the autonomic thermoregulatory response. If this were the case, then near-term pregnant rats should develop a "normal" fever after PGE1 administration if they were studied in a thermocline where they could utilize behavioral as well as autonomic thermoregulatory effectors to increase their body core temperature (Tbc). Experiments were, therefore, carried out on 13 nonpregnant and 14 pregnant chronically instrumented rats in a thermocline (temperature gradient 10-40 degrees C) to investigate their Tbc responses to ICV injection of PGE1. ICV injection of 0.2 microgram PGE1 produced significant increases in Tbc and fever index in both nonpregnant and pregnant animals (day 19 of gestation); the increases, however, were significantly attenuated in the pregnant compared with the nonpregnant rats. Behavioral (e.g., selected ambient temperature) and autonomic (e.g., oxygen consumption) thermoregulatory effectors were activated to increase Tbc after ICV PGE1 in both groups of animals, but the duration of activation was shortened in pregnant compared with nonpregnant rats. The abbreviated thermoregulatory effector responses and the resulting attenuated febrile response to PGE1 in the pregnant rats may have resulted from a pregnancy-related activation of an endogenous antipyretic system.


Assuntos
Alprostadil/farmacologia , Regulação da Temperatura Corporal/fisiologia , Febre/fisiopatologia , Prenhez/fisiologia , Vasodilatadores/farmacologia , Animais , Sistema Nervoso Autônomo/fisiologia , Regulação da Temperatura Corporal/efeitos dos fármacos , Feminino , Febre/induzido quimicamente , Injeções Intraventriculares , Consumo de Oxigênio/fisiologia , Gravidez , Ratos , Ratos Sprague-Dawley
8.
J Appl Physiol (1985) ; 83(5): 1612-6, 1997 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-9375328

RESUMO

Exposure of a male or nonpregnant female rat to a novel environment, such as a simulated open field, induces a transient increase in core temperature, which is often called stress-induced hyperthermia. Pregnancy alters this response such that the core temperature index increases significantly during exposure to a simulated open field on day 10 but not on days 15 and 20 of gestation in rats. The present experiments were carried to investigate the effect of chronic administration of nicotine (0, 1, 2, 4, or 8 mg.kg-1.24 h-1 for 13-15 days) on the core temperature response to a simulated open field in chronically instrumented pregnant (day 20 or 21 of gestation) and nonpregnant Sprague-Dawley rats. In nonpregnant rats, the core temperature index increased more during exposure to a simulated open field after chronic administration of nicotine at all doses than after chronic administration of vehicle; the core temperature response was not dependent on the dose of nicotine. In pregnant rats, significant increases in core temperature as well as in the core temperature index occurred only during exposure to a simulated open field after chronic administration of nicotine in doses of 2, 4, or 8 mg.kg-1.24 h-1; the core temperature response was dependent on the dose of nicotine. Our data provide evidence that chronic exposure to nicotine enhances the core temperature response to a simulated open field in nonpregnant rats and unmasks a maternal thermogenic response that is not seen to the same stimulus near term of pregnancy. The possible physiological consequences for the fetus are presently unknown and require investigation.


Assuntos
Temperatura Corporal/efeitos dos fármacos , Nicotina/farmacologia , Agonistas Nicotínicos/farmacologia , Prenhez/fisiologia , Estresse Psicológico/fisiopatologia , Animais , Temperatura Corporal/fisiologia , Meio Ambiente , Feminino , Masculino , Gravidez , Ratos , Ratos Sprague-Dawley
9.
J Appl Physiol (1985) ; 83(3): 837-44, 1997 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-9292471

RESUMO

Although the mechanisms remain unknown, maternal core temperature (Tc) decreases near term of pregnancy and is increased throughout lactation in rats. The purpose of our present experiments was to determine whether pregnancy and lactation shift the thermoneutral zone of rats and to investigate whether the changes in maternal Tc during pregnancy and lactation result from "forced" or "regulated" thermoregulatory responses. Conscious, chronically instrumented nonpregnant and pregnant and lactating rats were studied both in a thermocline (a chamber with a linear temperature gradient from 12 to 36 degrees C) and in a metabolic chamber to determine the influence of pregnancy and lactation on selected ambient temperature as well as the thermoregulatory response to changes in ambient temperature. We found that selected ambient temperature, oxygen consumption, and thermal conductance did not change in rats studied in a thermocline as Tc decreased near term of pregnancy. There was, however, a downward shift in the thermoneutral zone of rats studied in a metabolic chamber near term of pregnancy. During lactation, selected ambient temperature decreased in rats studied in a thermocline as oxygen consumption and Tc increased. The thermoneutral zone of lactating rats was not different from that of nonpregnant animals. Thus our data provide evidence that the decrease in Tc near term of pregnancy in rats results from a regulated thermoregulatory response, whereas the increase in Tc during lactation results from a forced thermoregulatory response.


Assuntos
Regulação da Temperatura Corporal/fisiologia , Lactação/fisiologia , Prenhez/fisiologia , Animais , Sistema Nervoso Autônomo/fisiologia , Feminino , Consumo de Oxigênio/fisiologia , Gravidez , Ratos , Ratos Sprague-Dawley , Temperatura
10.
J Appl Physiol (1985) ; 85(3): 1150-9, 1998 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-9729594

RESUMO

In newborns and adults of a number of species, exposure to acute hypoxemia produces a "regulated" decrease in core temperature, the mechanism of which is unknown. The present experiments were carried out in chronically instrumented newborn (5-10 days of age; n = 59) and older (25-30 days of age; n = 61) guinea pigs to test the hypothesis that the endogenous opioids mediate this regulated decrease in core temperature. During an experiment, core temperature, oxygen consumption, and selected ambient temperature were measured in a thermocline (linear temperature gradient of 10-40 degreesC) during a control period of normoxemia, an experimental period of normoxemia or hypoxemia (inspired oxygen fraction 0.10), and during a recovery period of normoxemia following an intraperitoneal injection of naloxone hydrochloride (a nonspecific opioid antagonist; 1, 2, or 4 mg/kg) or vehicle. Naloxone did not significantly alter basal core temperature or the core temperature response to acute hypoxemia in newborn or older guinea pigs. Naloxone did, however, decrease basal oxygen consumption in newborn and older guinea pigs and altered the thermoregulatory effector mechanism used to decrease core temperature during hypoxemia in the newborn guinea pigs. Our data do not support the hypothesis that the endogenous opioids mediate the regulated decrease in core temperature that occurs in newborn and older guinea pigs during exposure to acute hypoxemia.


Assuntos
Temperatura Corporal/efeitos dos fármacos , Hipóxia/fisiopatologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Animais , Animais Recém-Nascidos , Cobaias , Consumo de Oxigênio/efeitos dos fármacos , Consumo de Oxigênio/fisiologia
11.
J Appl Physiol (1985) ; 85(6): 2066-74, 1998 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-9843527

RESUMO

Failure to autoresuscitate by hypoxic gasping during prolonged sleep apnea has been suggested to play a role in sudden infant death. Furthermore, maternal smoking has been repeatedly shown to be a risk factor for sudden infant death. The present experiments were carried out on newborn rat pups to investigate the influence of perinatal exposure to nicotine (the primary pharmacological and addictive agent in tobacco) on their time to last gasp during a single hypoxic exposure and on their ability to autoresuscitate during repeated exposure to hypoxia. Pregnant rats received either nicotine (6 mg. kg-1. 24 h-1) or vehicle continuously from day 6 of gestation to days 5 or 6 postpartum via an osmotic minipump. On days 5 or 6 postpartum, pups were exposed either to a single period of hypoxia (97% N2-3% CO2) and their time to last gasp was determined, or they were exposed repeatedly to hypoxia and their ability to autoresuscitate from primary apnea was determined. Perinatal exposure to nicotine did not alter the time to last gasp, but it did impair the ability of pups to autoresuscitate from primary apnea. After vehicle, the pups were able to autoresuscitate from 18 +/- 1 (SD) periods of hypoxia, whereas, after nicotine, the pups were able to autoresuscitate from only 12 +/- 2 periods (P < 0.001) of hypoxia. Thus our data provide evidence that perinatal exposure to nicotine impairs the ability of newborn rats to autoresuscitate from primary apnea during repeated exposure to hypoxia, such as may occur during episodes of prolonged sleep apnea.


Assuntos
Hipóxia Fetal/fisiopatologia , Nicotina/toxicidade , Síndromes da Apneia do Sono/fisiopatologia , Animais , Animais Recém-Nascidos , Nível de Alerta/efeitos dos fármacos , Nível de Alerta/fisiologia , Feminino , Humanos , Lactente , Troca Materno-Fetal , Nicotina/administração & dosagem , Gravidez , Ratos , Ratos Sprague-Dawley , Ressuscitação , Fumar/efeitos adversos , Morte Súbita do Lactente/etiologia
12.
J Appl Physiol (1985) ; 87(4): 1346-53, 1999 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-10517762

RESUMO

Failure to autoresuscitate by hypoxic gasping during prolonged sleep apnea has been suggested to play a role in sudden infant death. Furthermore, thermal stress brought about by a contribution of infection, overwrapping, or excessive environmental heating has been shown to be associated with an increased risk of sudden infant death, particularly in prone sleeping infants. The present experiments were carried out on newborn rat pups to investigate the influence of "forced" changes in core temperature on their time to last gasp during a single hypoxic exposure and on their ability to autoresuscitate during repeated exposure to hypoxia. On day 5 or 6 postpartum the pups were placed in a temperature-controlled chamber regulated to 33, 35, 37, 39, or 41 degrees C and exposed to a single period of hypoxia (97% N(2)-3% CO(2)) and their time to last gasp was determined, or they were exposed repeatedly to hypoxia and their ability to autoresuscitate from primary apnea was determined. Increases in core temperature brought about by changes in ambient temperature from 33 to 41 degrees C decreased the time to last gasp after a single hypoxic exposure and decreased the number of successful autoresuscitations after repeated hypoxic exposures. Thus our data support the hypothesis that forced changes in core temperature brought about by changes in ambient temperature influence protective responses in newborns that may prevent death during hypoxia, as may occur during single or repeated episodes of prolonged sleep apnea.


Assuntos
Animais Recém-Nascidos/fisiologia , Temperatura Corporal , Hipóxia/fisiopatologia , Animais , Frequência Cardíaca , Ratos , Ratos Sprague-Dawley , Respiração , Temperatura , Fatores de Tempo
13.
J Appl Physiol (1985) ; 83(3): 830-6, 1997 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-9292470

RESUMO

Serial experiments were carried out on seven chronically instrumented Hartley-strain guinea pigs at 1, 3, and 5 wk of age to define their autonomic and behavioral thermoregulatory profiles and to test the hypothesis that they have the mechanisms in place shortly after birth that allow them to optimize their energy expenditure for thermoregulation by selecting a thermal environment that requires the lowest metabolic oxygen requirements. Each animal was studied in both a thermocline to determine selected ambient temperature and in a metabolic chamber to determine the thermoregulatory response to forced changes in ambient temperature. In the thermocline, the guinea pigs at all postnatal ages selected an ambient temperature that placed core temperature, oxygen consumption, thermal conductance, heart rate, and respiratory rate at levels comparable to those observed at ambient temperatures in which minimal oxygen consumption occurred in the metabolic chamber. Thus our experiments provide evidence that guinea pigs have the neurophysiological mechanisms in place shortly after birth that allow them to optimize their energy expenditure for thermoregulation by selecting a thermal environment that corresponds to the lowest metabolic oxygen requirements.


Assuntos
Envelhecimento/fisiologia , Animais Recém-Nascidos/fisiologia , Sistema Nervoso Autônomo/fisiologia , Comportamento Animal/fisiologia , Regulação da Temperatura Corporal/fisiologia , Animais , Metabolismo Energético/fisiologia , Cobaias , Frequência Cardíaca/fisiologia , Consumo de Oxigênio/fisiologia , Mecânica Respiratória/fisiologia , Temperatura
14.
J Appl Physiol (1985) ; 81(3): 1312-5, 1996 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-8889768

RESUMO

Rats have an attenuated or absent febrile response to exogenous pyrogen (e.g., bacterial endotoxin) and endogenous pyrogen (e.g., interleukin-1 beta) near term of pregnancy. The present experiments have been carried out on 19 nonpregnant and 18 time-bred pregnant Long-Evans rats to investigate the febrile response to intracerebroventricular (ICV) administration of prostaglandin E1 (PGE1). Each rat was anesthetized, a biotelemetry device was placed in the peritoneal cavity for measurement of body core temperature (Tbc), and guide cannulas were placed above the lateral cerebral ventricles for ICV injection of PGE1. At least 6 days were allowed to lapse between surgery and the experiments. ICV injection of 0.2 micrograms PGE1 produced significant increases in Tbc in both nonpregnant and pregnant animals (day 19 of gestation). The increase in Tbc as well as the fever index, however, were significantly attenuated in the pregnant compared with the nonpregnant rats. Vehicle had no effect on Tbc or fever index in either group of animals. The attenuated febrile response to PGE1 in the pregnant rats may have resulted from a pregnancy-related activation of endogenous antipyretics and/or impaired thermoregulatory effector mechanisms.


Assuntos
Alprostadil/farmacologia , Temperatura Corporal/efeitos dos fármacos , Febre/induzido quimicamente , Prenhez/efeitos dos fármacos , Animais , Feminino , Gravidez , Ratos
15.
J Appl Physiol (1985) ; 90(5): 1968-76, 2001 May.
Artigo em Inglês | MEDLINE | ID: mdl-11299291

RESUMO

Experiments were carried out to determine the threshold level of maternal nicotine that impairs protective responses of rat pups to hypoxia. From days 6 or 7 of gestation, pregnant rats received either vehicle or nicotine (1.50, 3.00, or 6.00 mg of nicotine tartrate. kg body wt(-1).day(-1)) or vehicle continuously via a subcutaneous osmotic minipump. On postnatal days 5 or 6, pups were exposed to a single period of hypoxia produced by breathing an anoxic gas mixture (97% N(2) or 3% CO(2)) and their time to last gasp was determined, or they were exposed to intermittent hypoxia and their ability to autoresuscitate from hypoxic-induced primary apnea was determined. Perinatal exposure to nicotine did not alter the time to last gasp or the total number of gasps when the pups were exposed to a single period of hypoxia. The number of successful autoresuscitations on repeated exposure to hypoxia was, however, decreased in pups whose dams had received either 3.00 or 6.00 mg of nicotine tartrate/kg body wt; these dosage regimens produced maternal serum nicotine concentrations of 19 +/- 6 and 35 +/- 8 ng/ml, respectively. Thus our experiments define the threshold level of maternal nicotine that significantly impairs protective responses of 5- to 6-day-old rat pups to intermittent hypoxia such as may occur in human infants during episodes of prolonged sleep apnea or positional asphyxia.


Assuntos
Hipóxia/fisiopatologia , Nicotina/farmacologia , Efeitos Tardios da Exposição Pré-Natal , Análise de Variância , Animais , Animais Recém-Nascidos , Relação Dose-Resposta a Droga , Feminino , Infusões Parenterais , Nicotina/administração & dosagem , Nicotina/sangue , Gravidez , Ratos , Ratos Sprague-Dawley , Ressuscitação
16.
J Appl Physiol (1985) ; 89(1): 259-64, 2000 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10904060

RESUMO

Experiments were carried out on chronically instrumented newborn and older rabbits to characterize their core temperature (T(c)) responses to acute hypoxemia and to differentiate "forced" vs. "regulated" thermoregulatory responses. Three age ranges of kits were studied: 4-6, 9-11, and 28-30 days of age. During an experiment, T(c), selected ambient temperature (T(a)), and oxygen consumption were measured from kits studied in a thermocline during a control period of normoxemia, an experimental period of normoxemia or hypoxemia (fraction of inspired oxygen 0.10), and a recovery period of normoxemia. We reasoned that no change or a decrease in T(a) while T(c) decreased during hypoxemia would indicate a regulated thermoregulatory response, whereas an increase in T(a) while T(c) decreased during hypoxemia would indicate a forced thermoregulatory response. T(c) decreased during acute hypoxemia in the older kits but not in the 4- to 6-day-old kits; the decrease in T(c) was accentuated on postnatal days 28-30 compared with postnatal days 9-11. T(a) decreased or stayed the same during exposure to acute hypoxemia. Our data provide evidence that postnatal maturation influences the T(c) response of rabbits to acute hypoxemia and that the decrease in T(c) during hypoxemia in the older kits results from a regulated thermoregulatory response.


Assuntos
Envelhecimento/fisiologia , Temperatura Corporal/fisiologia , Hipóxia/fisiopatologia , Doença Aguda , Fatores Etários , Animais , Animais Recém-Nascidos , Comportamento Animal/fisiologia , Regulação da Temperatura Corporal/fisiologia , Estado de Consciência/fisiologia , Hematócrito , Consumo de Oxigênio/fisiologia , Coelhos
17.
J Appl Physiol (1985) ; 87(1): 170-4, 1999 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10409571

RESUMO

Near the term of pregnancy, rats have an attenuated core temperature response on exposure to a novel environment (e.g., a simulated open field) compared with that observed early in pregnancy or in nonpregnant rats. The present experiments were carried out on 26 nonpregnant and 26 pregnant rats to test the hypothesis that arginine vasopressin, functioning as an endogenous antipyretic substance in the central nervous system, mediates this attenuated core temperature response. Exposure to a simulated open field after intracerebroventricular (ICV) vehicle produced a significant increase in core temperature in both nonpregnant and pregnant animals, the magnitude and duration of which were greater in the nonpregnant rats. In nonpregnant rats, exposure to a simulated open field after ICV vasopressin V(1)-receptor antagonist altered the pattern of the core temperature response but not the core temperature index compared with that observed on exposure to a simulated open field after ICV vehicle. In pregnant animals, ICV vasopressin V(1)-receptor antagonist did not alter the core temperature response to a simulated open field compared with that observed after ICV vehicle. Thus our data do not support the hypothesis that a pregnancy-related activation of arginine vasopressin attenuates the core temperature response to a simulated open field in rats near the term of pregnancy.


Assuntos
Arginina Vasopressina/fisiologia , Regulação da Temperatura Corporal/fisiologia , Prenhez/fisiologia , Animais , Antagonistas dos Receptores de Hormônios Antidiuréticos , Arginina Vasopressina/análogos & derivados , Arginina Vasopressina/farmacologia , Regulação da Temperatura Corporal/efeitos dos fármacos , Meio Ambiente , Feminino , Febre/etiologia , Febre/fisiopatologia , Antagonistas de Hormônios/farmacologia , Gravidez , Complicações na Gravidez/fisiopatologia , Ratos , Ratos Sprague-Dawley , Estresse Fisiológico/complicações , Estresse Fisiológico/fisiopatologia
18.
J Appl Physiol (1985) ; 77(2): 726-30, 1994 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-8002520

RESUMO

Cold exposure elicits several thermoregulatory responses, including an increased metabolic heat production from shivering and nonshivering thermogenesis. The increased metabolism can be in response to body core and/or body cutaneous cooling. Hypoxic hypoxia has been shown to attenuate the metabolic response to cutaneous cooling. We measured metabolic heat production in adult conscious rats during independent cutaneous and core cooling, during normoxia and hypoxia, to 1) test the hypothesis that hypoxia suppresses the metabolic response to independent core cooling and 2) determine whether hypoxia acts preferentially on the response to cutaneous or core cooling. The animals were studied in a temperature-controlled metabolic chamber, and body core temperature was controlled by an abdominal heat exchange coil. Ambient temperature was varied (10, 19, and 28 degrees C) while core temperature was clamped at 37 degrees C or core temperature was varied (33, 35, and 37 degrees C) at a stable ambient temperature of 28 degrees C. Our data indicate that although the sensitivity of the metabolic response to core cooling is about five to six times that to cutaneous cooling. Hypoxia similarly attenuates thermoregulatory responses to both stimuli.


Assuntos
Regulação da Temperatura Corporal , Temperatura Baixa , Hipóxia/metabolismo , Pele/metabolismo , Animais , Hipóxia/fisiopatologia , Masculino , Consumo de Oxigênio , Ratos , Ratos Sprague-Dawley , Estremecimento , Pele/fisiopatologia
19.
Brain Res ; 311(2): 259-65, 1984 Oct 08.
Artigo em Inglês | MEDLINE | ID: mdl-6498484

RESUMO

We did experiments to determine whether or not acute increases in blood pressure would cause arousal from sleep. Nine lambs were studied 3-4 days after a balloon-tipped catheter was inserted via the femoral artery into the descending aorta and electrodes for the following recordings were implanted: electrocorticogram, electro-oculogram, electrocardiogram and diaphragm electromyogram. Balloon inflation increased mean arterial blood pressure 27.9 +/- 6.3 mm Hg (mean +/- 1 S.D.) during quiet sleep (QS) and 24.4 +/- 8.9 mm Hg during active sleep (AS). Behavioral arousal occurred from both sleep states but was significantly (P less than 0.05) delayed during active sleep (21.3 +/- 6.7 s) compared to quiet sleep (10.0 +/- 3.3 s). This occurred despite there being a greater percent change in R-R interval for a percent change in mean blood pressure during active sleep (2.68 +/- 1.08) than during quiet sleep (1.55 +/- 0.62). The increases in blood pressure did not produce any significant changes in respiratory rate of integrated diaphragm activity. Thus, acute increases in blood pressure are capable of causing arousal from sleep. This finding should be considered when one discusses the possible mechanisms of arousal from sleep during rapidly developing hypoxemia.


Assuntos
Nível de Alerta/fisiologia , Pressão Sanguínea , Sono/fisiologia , Envelhecimento , Animais , Animais Recém-Nascidos , Frequência Cardíaca , Balão Intra-Aórtico , Ovinos
20.
Physiol Behav ; 65(4-5): 889-92, 1999.
Artigo em Inglês | MEDLINE | ID: mdl-10073497

RESUMO

The induction of psychological stress is often accompanied by a transient increase in core temperature, commonly referred to as stress induced hyperthermia. Although stress-induced hyperthermia occurs when rats, mice, and pigs are exposed to a novel stimulus (e.g., a simulated open field, restraint, etc.), whether or not it occurs in guinea pigs has not been investigated. The present experiments were therefore carried out to investigate the thermoregulatory responses of both male (n = 7) and female (n = 7) adult guinea pigs when they were exposed to a simulated open field. Unexpectedly, neither the male nor female guinea pigs developed stress-induced hyperthermia. To the contrary, female but not male guinea pigs significantly decreased their core temperature during an open field experiment. The mechanism of the gender-specific thermoregulatory response of the adult guinea pig to psychological stress is presently unknown.


Assuntos
Regulação da Temperatura Corporal/fisiologia , Meio Ambiente , Estresse Psicológico/fisiopatologia , Animais , Feminino , Febre/fisiopatologia , Febre/psicologia , Cobaias , Masculino , Caracteres Sexuais
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