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At least 1,531 records · Page 85Linked to original sources
PubMed1978

Assessment of ether anesthesia in normal and spinal cats using gas--liquid chromatographic analysis of blood.

A new gas-liquid chromatographic method was developed for the determination of diethylether in whole blood. Ether was quantitated by peak area ratio analysis with n-propanol as the internal standard using a flame ionization detector. Blood ether concentrations were determined in cats undergoing inhalational anesthesia by ether in oxygen. In normal spontaneously breathing cats, anesthesia began at ether concentrations of about 0.6 g/l, and respiratory arrest occurred at 2.4 g/l and above. Mean arterial blood pressure was well maintained throughout the entire anesthetic range. In spinal artificially respired animals, mean arterial blood pressure correlated inversely with blood ether concentration. The data suggest that decline in blood pressure may be a useful sign of ether toxicity in spinal cats.

Anesthesia↗
PubMed1977

Protein transport across cerebral vessels during metrazole-induced convulsions.

The effects of pentylenetetrazole-induced convulsions on cerebrovascular permeability for horseradish peroxidase were studied in locally anesthetized, artificially respired, paralyzed cats. Horseradish peroxidase circulated for 1, 2.5, 5, 10, 30, and 60 min and accumulated in medium-size, i.e., arterial or venous, blood vessel walls. Cerebral neuropil was permeated earliest in thalamic nuclei including medial and lateral geniculate nuclei. No tight junctions containing horseradish peroxidase were found. With 1.0 and 2.5 min circulation of horseradish peroxidase, arterial adventitia and basement membranes contained more peroxidase than surrounding interstitial space in contrast to veins and capillaries. Convulsions increased the number of endothelial vesicles containing horseradish peroxidase in arteries, veins, and capillaries but total number (stained plus unstained) of endothelial vesicles was increased slightly only in capillaries. We conclude that increased permeability is initially at the arterial level, although veins may also become permeable. The role of the endothelial vesicles in transit or protein in and out of the nervous system is not clear.

Animals↗
PubMed1982

NAD/NADH: redox state changes on cat brain cortex during stimulation and hypercapnia.

The redox state of the anterior suprasylvian gyrus of cats was measured during electrical stimulation and under hypercapnia on cast immobilized and artificially respirated. The state of the nicotinamide adenine dinucleotide-reduced nicotinamide adenine dinucleotide (NAD/NADH) redox system was monitored by in vivo fluorometry. Hypercapnia was produced by inhalation of 10, 15, and 30% CO2, respectively. Hypercapnic acidosis led to NADH oxidation. The NADH oxidation under 30% CO2 inhalation was significantly larger (-14.9 +/- 2.9%) than that observed under 10% (-6.5 +/- 1.9%) and 15% CO2 (-7.0 +/- 1.6%) inhalation. Under normocapnic conditions, stimulation induced NAD reduction to NADH (5.5 +/- 0.8%). The magnitude of the NAD reductive response to stimulation was unaffected by 10% CO2 inhalation, but it was decreased by 15 and 30% CO2 inhalation. The increased concentration of NADH upon stimulation is interpreted as resulting from an increased rate of substrate mobilization. The cause of the oxidation of the NADH pool of the cell during hypercapnia is partly due to the direct inhibitory effect of CO2 on the carbohydrate metabolism, but the role of other mechanisms cannot be neglected either.

Animals↗
PubMed1975

Pathway mediating hypotension elicited by stimulation of the amygdala in the rat.

Cardiovascular responses were elicited from 372 histologically verified sites in the amygdala and closely adjacent structures in 82 rats under urethan or chloralose anesthesia. Arterial hypotension was elicited at low current intensities from the medial, central, lateral, and basal nuclei of rats under either anesthetic; the hypotension was still elicited in artificially respired paralyzed rats. Stimulation of the cortical nucleus produced variable changes in arterial pressure. The hypotension elicited under urethan was not found to be correlated with changes in the frequency of electrical activity of hippocampus, amygdala, or septum or to be associated with electrical seizures. Hypertension was usually elicited from the medial nucleus at high current intensities and was attributed to current spread to the cortex ventral to the medial nucleus from which hypertension was elicited at low current intensities. Stimulation of the central, basal, and lateral nuclei under chloralose elicited bradycardia. Lesions of the stria terminalis had no effect on the hypotension, whereas lesions of the ipsilateral medial forebrain bundle abolished this response.

Amygdala↗
PubMed1981

Pre- and postganglionic sympathetic activity in splanchnic nerves of rats.

Integrated sympathetic activity was recorded on anterior or posterior divisions of the greater splanchnic nerve (GSN) in anesthetized, acutely spinalized, artificially respired Wistar rats before and after ganglionic blockade by hexamethonium. Focal electrical stimulation of spinal sympathoexcitatory pathways elicited large increases in splanchnic sympathetic activity. Ganglionic blockade showed that the anterior and posterior divisions of the GSN are predominantly preganglionic and postganglionic, respectively. Histological examination of excised splanchnic nerves and sympathetic chains indicated that splanchnic postganglionic cell bodies must lie in the chain ganglia rather than within the GSN. Postganglionic responses were calculated for each rat by subtracting responses recorded after ganglionic blockade from responses recorded before ganglionic blockade. As expected, postganglionic responses exhibited longer onset latencies than preganglionic responses. However, evoked activity increased and decreased more rapidly in postganglionic fibers than in preganglionic fibers. Responses to stimulus trains were also better maintained in postganglionic than in preganglionic fibers.

Animals↗
PubMed1982

Sympathetic activity in spontaneously hypertensive rats after spinal transection.

To test the hypothesis that sympathetic hyperactivity and hyperexcitability in spontaneously hypertensive rats (SHR) is generated at spinal and/or ganglionic levels, we measured integrated renal nerve activity (before ganglionic blockade) and adrenal nerve activity (after ganglionic blockade) in 12- to 14-wk-old SHR and normotensive Wistar-Kyoto rats (WKY). Rats were anesthetized with alpha-chloralose, artificially respired, and paralyzed. Spinal cords were transected at C1 to eliminate normal supraspinal control of sympathetic activity. The effectiveness of descending sympathoexcitatory and sympathoinhibitory pathways was tested by measuring changes in nerve activity elicited by graded spinal stimulation. Spontaneous renal nerve activity was elevated in SHR, but stimulation of descending excitatory pathways caused similar responses in SHR and WKY. Spontaneous adrenal preganglionic nerve activity was similar in SHR and WKY, but excitatory stimulation elicited larger adrenal nerve responses in SHR. We conclude that spinal and/or ganglionic mechanisms may generate a component of the sympathetic hyperactivity exhibited by SHR. The larger adrenal preganglionic nerve responses to excitatory stimulation in SHR suggest that spinal systems may be partially responsible for adrenomedullary hyperexcitability in spontaneous hypertension.

Adrenal Glands↗
PubMed1987

Differential effects of spinal transection on sympathetic nerve activities in rats.

We measured renal, splenogastric, and lumbar multiunit sympathetic activities in chloralose-anesthetized, paralyzed, and artificially respired Sprague-Dawley rats. Acute spinal transection reduced arterial pressure and lumbar sympathetic activity. However, renal and splenogastric activities were doubled after transection. We conclude that spinal systems exist in the rat that are capable of maintaining renal and splenogastric, but not lumbar, sympathetic activities after spinal transection. Cross-correlation and power spectral analysis of simultaneously recorded sympathetic activities indicated that renal and splenogastric activities often, but not always, shared periodicities near the respiratory rate. These shared periodicities were responsible for high correlations between renal and splenogastric activities. After spinal transection, the shared periodicities usually disappeared, and correlations were reduced. Renal and lumbar activities were rarely strongly correlated, and they rarely shared major periodicities. We conclude that brain stem systems often provide synchronization of abdominal sympathetic activities. However, these activities can be independently generated in both intact and spinally transected rats.

Animals↗
PubMed1987

Elevated renal nerve activity after spinal transection: effects on renal function.

Spinal transection approximately doubles renal sympathetic activity (RSA) in rats. These experiments localized spinal pathways inhibiting RSA and determined the effects of transection-elicited renal sympathetic hyperactivity on renal circulation and renal function. Experiments were conducted in chloralose-anesthetized, paralyzed, artificially respired, male Sprague-Dawley rats. RSA was measured from an electrode on the left renal nerve. Renal arterial blood flow (RABF), glomerular filtration rate, urine flow rate, and renal sodium and potassium excretions were also measured. Localized lesions of the cervical spinal cord indicated that spinal generators of RSA were inhibited by pathways descending in the dorsal cervical cord. Autoregulation of RABF prevented transection-elicited increases in RSA from affecting renal vascular resistance. Renal sodium and potassium excretions were dramatically reduced after spinal transection, although these reductions were ameliorated somewhat by fixing posttransection renal arterial pressure at pretransection levels. We conclude that the vascular effects of transection-elicited elevations in RSA are minimized by autoregulation of RABF and that posttransection changes in renal function result from changes in both arterial pressure and RSA.

Animals↗
PubMed1991

Splanchnic sympathetic nerve activity and circulating catecholamines in the hyperthermic rat.

The mechanisms responsible for the initial rise in splanchnic vascular resistance with environmental heating are controversial, and those responsible for the subsequent fall in splanchnic resistance in the severely hyperthermic animal are unknown. Thus we examined the effect of environmental heating on plasma catecholamine concentration, splanchnic sympathetic nerve activity (SNA), and select blood chemistries. In one study, 25 male Sprague-Dawley rats (270-300 g) were assigned to one of five groups on the basis of their core temperature (Tc, 37, 39, 41, 43, or 44 degrees C) at death. Heart rate (HR), mean arterial pressure (MAP), and Tc were monitored during heat stress under alpha-chloralose anesthesia (12.5 mg.ml-1.h-1). At each predetermined Tc, an aortic blood sample was drawn and analyzed for mean plasma concentration of norepinephrine (NE), epinephrine (E), Na+, K+, and lactate. From 41 to 43 degrees C, NE and E rose significantly, and the animals became hyperkalemic and lactacidemic. In a separate study, we quantitated SNA from the greater splanchnic nerve during heat exposure of artificially respired animals anesthetized with pentobarbital sodium (50 mg/kg). MAP, splanchnic SNA, and Tc were recorded. Tc was elevated from 37.0 +/- 0.12 to 41.3 +/- 0.18 degrees C in 70 min by increase of ambient temperature to 38 degrees C in an environmental chamber. Splanchnic SNA was 54 +/- 8 spikes/s at a Tc of 37 degrees C and increased significantly as Tc exceeded 39 degrees C (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

New perfluorocarbon emulsion improves tissue oxygenation in cat retina.

We have studied the conditions under which a perfluorocarbon emulsion of perfluorooctyl bromide (PFOB; Alliance Pharmaceutical, San Diego, CA) enhances tissue O2 delivery. Measurements of retinal tissue O2 tension (PO2) were made in anesthetized, artificially respirated, dark-adapted, normovolemic cats before, during, and after the infusion of three successive doses of 1 g PFOB/kg body wt each. There was little immediate effect of the infusion on the tissue PO2 when the cats were breathing room air, but the mean increase in tissue PO2 during 100% O2 breathing was 60 +/- 9% (SE; n = 8 cats) greater after infusion of 1 g PFOB/kg and approximately 136% greater after 3 g PFOB/kg. Similar infusions of the emulsifying medium alone had negligible effects on tissue PO2. These results suggest that PFOB emulsion may be clinically useful in treating tissue hypoxia in normovolemic patients breathing O2-enriched air.

Animals↗
PubMed2000

Ongoing and stimulus-evoked activity of sympathetically correlated neurons in the intermediate zone and dorsal horn of acutely spinalized rats.

We have shown previously that in the acutely spinalized anesthetized rat the activities of many dorsal horn interneurons (DHN) at the T(10) level are correlated positively with both ongoing and stimulus-evoked renal sympathetic nerve activity (RSNA) and therefore may belong to networks generating RSNA after acute, cervical, spinal transection. In the present study, we recorded from both DHN and interneurons in the intermediate zone (IZN) of the T(10) spinal segment in acutely C(1)-transected, chloralose-anesthetized, artificially respired rats. The activities of a similar percentage of IZN and DHN were correlated positively with ongoing RSNA, but the peaks of spike-triggered averages of RSNA based on the activity of IZN were larger, relative to dummy averages, than spike-triggered averages of RSNA based on the activity of DHN. Sympathetically correlated DHN and IZN differed in their responses to noxious somatic stimuli. Most correlated DHN had relatively simple somatic fields; they were excited by noxious stimulation of the T(10) and nearby dermatomes and inhibited by stimulation of more distal dermatomes. As we have shown previously, the excitatory and inhibitory fields of these neurons were very similar to fields that, respectively, excited and inhibited RSNA. On the other hand, the somatic fields of 50% of sympathetically correlated IZN were significantly more complex, indicating a difference between either the inputs or the processing properties of IZN and DHN. Sympathetically correlated IZN and DHN also differed in their responses to colorectal distension (CRD), a noxious visceral stimulus. CRD increased RSNA in 11/15 rats and increased the activity of most sympathetically correlated T(10) IZN. On the other hand, CRD decreased the activity of a majority of sympathetically correlated T(10) DHN. These observations suggest that the same stimulus may differentially affect separate, putative, sympathoexcitatory pathways, exciting one and inhibiting the other. Thus the magnitude and even the polarity of responses to a given stimulus may be determined by the modality and location of the stimulus, the degree to which multiple pathways are affected by the stimulus, and the ongoing activity of presympathetic neurons, at multiple rostrocaudal levels, before stimulation. A multipathway system may explain the variability in autonomic responses to visceral and somatic stimuli exhibited in spinally injured patients.

Action Potentials↗
PubMed1998

[Review, present and prospects of obstetrics].

During the last 25 years, the most impressive development in obstetrics has been the reduction of perinatal mortality from approximately 25 to below 6. Contrary to the expectations of those days, this has not been achieved by a decreased rate of premature births but by a better management of prematurely born babies, particularly by the induction of fetal organ maturity by corticosteroids and the antenatal transfer of high-risk pregnant women to a perinatal care centre. A more careful birth management and the corresponding ameliorations in neonatology (e.g. dosing of surfactants, less invasive methods of artificial respiration) have also contributed to the better results. The introduction of the prostaglandins to expel the fetus, the induction of delivery treatment of postpartal atonia were other milestones in the of obstetrics. Apart from these medical developments, sociological trends shaped obstetrics too, and these will influence it future: the increasing importance of the patient's will, paramedical factors in obstetrics and the heightened readiness to go to court in case of supposed damage. In obstetrics, the next few decades will show an uncheckable increase in the frequency of caesarean sections, due to - among other factors - the knowledge that vaginal deliveries cause injuries of the pelvic floor which have mostly been disregarded until now. Because of the expected decrease in birth rates, the increased number of doctors and midwives, the more and more demanding attitude of the population and the relentless readiness of supposedly injured patients to take legal action, the environment for obstetricians well become even more difficult in the future.

Austria↗
PubMed1988

3-Methylhistidine/creatinine ratio in urine from low-birth-weight infants. Clinical approach.

Single urine voidings were collected twice a week in the clinical course of 12 low-birth-weight infants (gestational age: 31.8 +/- 2.8 weeks; birth weight: 1,383 +/- 308 g) and analyzed for 3-methylhistidine and creatinine. The mean 3-methylhistidine/creatinine ratio for 6 healthy, well-fed, growing low-birth-weight infants was 20.2 +/- 1.9 mumol/mmol. In the clinical course of single individuals a rise of urinary 3-methylhistidine/creatinine ratio was observed in cases of acute infection and/or low energy supply (less than 100 kcal/kg/day) frequently coupled with insufficient weight gain. Mean 3-methylhistidine/creatinine ratios in infants with hyaline membrane syndrome under artificial respiration were generally higher than in the controls matched for energy supply.

Body Weight↗
PubMed1978

Oxygen cost of breathing in dogs.

The O2 cost of breathing has been calculated in awake and anesthetized dogs breathing spontaneously. Respiratory variables were measured in tracheostomized dogs in the standing position, while supported in a canvas sling, at room temperatures between 20 and 23 degrees C. Minute ventilation ranged between 3 and 53 liters/min while VO2 ranged from 61 to 686 ml/min. VE, VO2 and f varied considerably from measurement to measurement even though body temperatures and experimental conditions changed very little. VO2 increased with VE: VO2 = 10.2 VE + 58.4 r = 0.94. A cubic polynomial equation was also calculated for these data: VO2 = 11.6 + 19.0 VE-0.42 (VE)2 + 0.0057 (VE)3. Awake dogs showed panting and considerable hyperventilation (PACO2 = 22.5 +/- SD of 4.5 mm Hg). Anesthetized dogs had lower average values of f, VE and VO2; while average PACO2 was 29.1 +/- 4.5 mm Hg. VO2 and VE measured when the dogs were anesthetized, paralyzed and artifically ventilated were related by this equation: VO2 = 5.9 VE + 87.5, r = 0.88. The O2 cost of breathing, calculated by subtracting the regression equation obtained while the dogs were under artificial respiration, from the cubic polynomial equation, increased with increasing VE in a curvilinear fashion. The values for O2 cost of breathing at high levels of ventilation were high because dogs' lungs are small. After correcting for lung size, values for O2 cost of breathing were similar to those in humans.

Anesthesia↗
PubMed1979

[Pathogenesis of acute hypercapnic hyperammoniaemia (author's transl)].

Alterations in the ammonia concentration in arterial blood due to drug-induced portal vasoconstriction (oxprenolol 1 mg/kg) or vasodilatation (phentolamine 0.5 mg/kg) were studied in anaesthetized and artificially respirated mongrel dogs during normal air ventilation, during hypercapnia induced by ventilation with an appropriate gas mixture, and during episodes. The NH3 values in arterial-blood plasma were in the region of 41 microgram/100 ml and those in portal-blood plasma 3--4 times higher. The induction of progressive levels of hypercapnia opened the portal-to-systemic venous shunt, producing an increase in arterial NH3 and, to a lesser extent, NH3 in the CSF. The portal vasoconstriction caused by oxprenolol 1 mg/kg i.v. resulted in the functional elimination of the shunt during normoxia or hypercapnia, leading to a decrease in the NH3 concentration in the arteral blood and hence also in the CSF. The vasodilating effect of phentolamine 0.5 mg/kg i.v., on the other hand, caused a transient, stastically significant increase in arterial NH3 during normoxia; during hypercapnia the NH3 values did not differ from the controls.

Ammonia↗
PubMed1982

Effects of surgery on airway mechanics in tracheal stenosis.

12 patients suffering from severe extrathoracic tracheal stenosis mainly caused by long-term artificial ventilation were investigated by comparing their airway mechanics before and after tracheal sleeve resection and during long-term follow up. The investigations included body plethysmography, flow-volume relation, effect of bronchodilator, bronchial challenge and endoscopic estimation of the tracheal diameter. Tracheal sleeve resection in stenosis doubles the tracheal diameter from 5.9 to 11.0 mm. Resistance parameters and forced expiratory flow values reflected the significant improvement best. Airway structure remains stable during long-term follow-up, and effort-dependent parameters improve further. Compared to normal volunteers with artificially induced stenosis patients show a higher tolerability for airway narrowing. A tracheal diameter of 5 mm produces severe complaints and distinct functional distortions which are shown in specific airway resistance of 7.5 cm H2O X s, specific airway conductance of 0.02 cm H2O-1 X s-1 and FEV1 of 1 l X s-1. These values are absolute indications for resection. Tracheal stenosis after long-term artificial respiration can be influenced slightly by bronchodilator therapy. Nonspecific bronchial hyperreactivity is present, suggesting increased reagibility of the bronchial smooth muscles.

Acetylcholine↗
PubMed1984

Effects of FPL 55712, ETYA and aminophylline upon Ascaris-induced bronchoconstriction in cynomolgus monkeys.

Dose-related impairment of pulmonary functions was induced in artificially respired, anesthetized cynomolgus monkeys by inhalation of aerosolized Ascaris antigen (AA) in ascending doses. The effects of pharmacologic agents were assessed by increases in threshold Ascaris dose (TAD). TAD were defined as the doses of AA needed for 20% increase in pulmonary resistance and 15% decrease in compliance. Inhaled FPL 55712, an SRS-A antagonist (1.24 mg through-the-valve dose; TTVD), and 5,8,11,14-eicosatetraynoic acid (ETYA), an inhibitor of lipoxygenase and cyclooxygenase (1.0 mg TTVD) resulted in significant increases in the geometric means of TAD for changes in compliance (p less than 0.01). The effects of both agents upon resistance were of borderline significance. Orally administered aminophylline (30 mg/kg) had no significant effect upon mean TAD for resistance or compliance. The activities of FPL 55712 and ETYA suggest that spasmogenic leukotrienes are involved in the pulmonary allergic reactions in cynomolgus monkeys.

5,8,11,14-Eicosatetraynoic Acid↗