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At least 1,513 records · Page 84Linked to original sources
PubMed1988

Multi- and single-fibre mesenteric and renal sympathetic responses to chemical stimulation of intestinal receptors in cats.

1. In cats anaesthetized with alpha-chloralose and artificially respired, stimulation of intestinal receptors with bradykinin caused greater reflex excitation of mesenteric than of renal efferent multifibre nerve activity and significant pressor responses. 2. Activity of all nerve bundles used in this study was inhibited by stimulation of pressoreceptors. Increases in systemic arterial pressure caused inhibition of activity of renal nerves which was significantly greater than that of mesenteric nerves. 3. Spinal transection caused significant decreases in tonic renal nerve activity without altering the ongoing discharge rate of mesenteric nerves. Stimulation of intestinal receptors in spinal cats still caused significant increases is discharge of mesenteric and renal nerves, indicating that this reflex contains a spinal component. 4. Recordings of activity of individual fibres within mesenteric (21) and renal (23) nerves provided information regarding the basis for the multifibre responses to stimulation of intestinal receptors. The same proportion of fibres from both nerves was excited, but the increase in activity of mesenteric fibres was significantly greater than that of renal fibres. 5. Mesenteric fibres could be classified into two groups, based on their sensitivity to pressoreceptor influences. Fibres that exhibited pressoreceptor-independent discharge had the greatest responses to stimulation of intestinal receptors. 6. Following spinal transection the majority of mesenteric fibres continued to fire, whereas most renal fibres became quiescent. 7. The non-uniform pattern of neuronal excitation to chemical stimulation of intestinal receptors was manifest after spinal transection, demonstrating that exclusively spinal pathways can mediate this differential response pattern. 8. These results support the hypothesis that viscero-sympathetic reflexes may be organized to cause preferential excitation of neural activity directed to the organ from which the reflex originates.

Action Potentials↗
PubMed1988

Lateral interactions at direction-selective striate neurones in the cat demonstrated by local cortical inactivation.

1. Single neurones were recorded with glass-coated tungsten electrodes from area 17 of the cat's visual cortex. The cats were anaesthetized and artificially respirated with a mixture of halothane, nitrous oxide and oxygen. 2. For local cortical inactivation a multibarrel pipette was placed 0.5-2.5 mm posterior (or anterior) to the recording site, at a depth of 400-600 micron. Four separate barrels of the pipette were filled with gamma-aminobutyric acid (GABA); the fifth was filled with Pontamine Sky Blue for labelling of the centre of the inactivation site. 3. Direction-selective cells, of differing optimal orientations and preferred directions of motion, were classified as simple or complex and tested with computer-controlled stimuli presented on an oscilloscope. 4. During continuous recording GABA was microionophoretically applied for different durations and with different ejection currents. The effectiveness of GABA microionophoresis was evident from the direct GABAergic effects (strong overall inhibition of the recorded cells) observed with high ejection currents and prolonged application. 5. Two discrete effects could be observed during local inactivation distant from the cortical cell under study: an increase of the response in either the non-preferred or the preferred direction; or a decrease of the response in the preferred direction. All GABA-induced changes were reversible. 6. The depressant action of GABA was independent of the relative topography between recording and inactivation site and affected mainly the response to the preferred direction of stimulus motion. 7. Disinhibition was only observed when the stimulus-evoked response moved on the cortical map in a direction from the GABA pipette towards the recording electrode. It is concluded that GABA reversibly silences inhibitory interneurones that are situated in the vicinity of the micropipette tip and are involved in generation of direction selectivity. 8. No fundamental differences between cells from different cortical layers were observed. The disinhibitory effects of GABA inactivation were more pronounced and more frequently seen in simple cells (61%) than in complex cells (38%), while the opposite was true for reduced excitation during lateral GABA inactivation (observed in 62% of the complex vs. 39% of the simple cells). Accordingly, lateral inhibition statistically prevails in simple cells and lateral excitation in complex cells. 9. Among the inhibitory and excitatory mechanisms affected by lateral GABA inactivation, inhibition is organized with a higher topographic specificity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1989

Ventrolateral medullary neurones: effects on magnitude and rhythm of discharge of mesenteric and renal nerves in cats.

1. Discharge of whole mesenteric and renal nerves was recorded in eighteen chloralose-anaesthetized, artificially respired cats. 2. Inhibition of tonic activity of neurones within the rostral ventrolateral medulla (RVLM blockade) by bilateral application of glycine caused significant reductions in discharge of renal and mesenteric nerves, arterial blood pressure and heart rate. The decrease in discharge of renal nerves was significantly greater than that of mesenteric nerves. 3. During the response to glycine application, the spinal cord was transected at the first cervical segment. The magnitude of renal nerve discharge after transection was not different from that during blockade of the RVLM. On the other hand, mesenteric nerve activity increased following spinal cord transection, returning to control levels. 4. Power spectral analysis revealed that mesenteric and renal nerves discharged with periodicities ranging from 1 to 6 Hz. Application of glycine to the RVLM reduced the slow rhythm in firing of mesenteric and renal nerves similarly. Transection of the spinal cord resulted in further reduction in the rhythmicity in discharge of both nerves. 5. The results indicate that excitatory drive from the RVLM is crucial for the maintenance of on-going discharge of renal, but not of mesenteric nerves. However, such inputs are apparently essential to maintain the slow rhythm in firing of both nerves.

Action Potentials↗
PubMed1989

Differential modulation by pulmonary stretch afferents of some reflex cardioinhibitory responses in the cat.

1. Cats were anaesthetized with a mixture of chloralose and urethane, and were artificially ventilated, the thorax being opened via a medial sternotomy. 2. Various cardiovascular receptors were stimulated during reflex inhibition of the central inspiratory neurones produced by electrical stimulation of both superior laryngeal nerves simultaneously, while the afferent input from the lungs was held constant by temporarily interrupting artificial respiration, the lungs being held static in their expiratory position. 3. Reflex cardioinhibitory responses were elicited by stimulation of (a) the carotid body chemoreceptors by intracarotid injections of cyanide; (b) the arterial baroreflex by controlled elevations of the blood pressure; (c) the carotid sinus baroreceptors by raising the pressure in isolated perfused carotid sinus preparations; (d) cardiac receptors by left atrial injections of veratridine, and (e) pulmonary C fibres (including J receptors) by right atrial injections of phenyl biguanide. 4. The effects of single inflations of the lungs on these reflex cardioinhibitory responses were studied and compared with the effects of the various inputs alone. 5. Stepwise increases in lung volume, while having no consistent effect on arterial blood pressure, progressively diminished the arterial chemoreceptor-induced bradycardia to a value of about 7% of the control response without lung inflation. The pulmonary afferents were less effective on reflex responses from other inputs, the corresponding values being: arterial baroreflex, 66%; carotid baroreceptors, 66%, and cardiac receptors, 70%. These effects of lung inflation were abolished by selective denervation of the lungs. 6. In contrast, the size of the bradycardia evoked by pulmonary C fibre stimulation was, on average, unaffected by inflation of the lungs. In some tests the response was actually increased. 7. The differential modulation by lung inflation of these reflex cardioinhibitory responses were the same after upper thoracic sympathectomy indicating that pulmonary afferents and cardiac efferents involved fibres in the vagus nerves. 8. The possible central mechanisms responsible for the differential modulation by lung inflation of cardioinhibitory reflexes are discussed.

Animals↗
PubMed1990

Selective control of sympathetic pathways to the kidney, spleen and intestine by the ventrolateral medulla in rats.

1. Electrical activity of multifibre renal, splenic, mesenteric and greater splanchnic nerves and 13th thoracic white rami was recorded in artificially respired, urethane-anaesthetized rats. Discharge of neurones in the rostral ventrolateral medulla was blocked by unilateral microinjections of the inhibitory amino acid glycine and effects on the electrical activity of these sympathetic nerves were compared. 2. Blockade of the rostral ventrolateral medulla caused greater decreases in discharge of renal than splenic nerves and had no consistent effect on mesenteric nerves. This blockade also decreased the discharge of the preganglionic white rami more than that of the preganglionic splanchnic nerves. 3. Postganglionic responses to rostral ventrolateral medulla blockade were always greater than preganglionic responses. 4. The arterial pressure and renal nerve responses to rostral ventrolateral medulla blockade in urethane-anaesthetized rats were not different from those in rats anaesthetized with alpha-chloralose. 5. These findings demonstrate that pre- and postganglionic sympathetic pathways to the kidney are more dependent upon excitatory drive from the rostral ventrolateral medulla than pathways directed to the spleen and intestine.

Animals↗
PubMed1991

Evidence for descending tonic inhibition specifically affecting sympathetic pathways to the kidney in rats.

1. The present study investigated the possibility that pre- and postganglionic neurones innervating the kidney and spleen in rats are affected by descending inhibitory as well as descending excitatory influences. This hypothesis was tested by comparing the effects of cervical spinal cord transection to the effects of blockade of tonic activity of excitatory neurones in the rostral ventrolateral medulla (RVLM). 2. Electrical discharge of multifibre postganglionic renal and splenic and preganglionic greater splanchnic nerves and 13th thoracic (T13) white rami was recorded in artificially respired, urethane-anaesthetized rats. In one group of rats, descending supraspinal pathways were interrupted by cervical spinal cord transection. In another group, tonic activity of rostral ventrolateral medulla (RVLM) neurones was blocked by bilateral microinjections of the inhibitory amino acid glycine. The effects of spinal cord transection were compared to effects of this bilateral RVLM blockade and to effects of unilateral RVLM blockade described in a previous study. 3. Spinal cord transection caused decreases in preganglionic greater splanchnic and postganglionic splenic nerves which were of the same magnitude as those caused by bilateral blockade of the RVLM. 4. In contrast, discharge of renal nerves was decreased more by bilateral RVLM blockade than by cervical spinal cord transection. Similarly, even unilateral RVLM blockade caused greater decreases in discharge of T13 white rami than were caused by spinal cord transection. 5. These findings suggest that renal nerves and their preganglionic inputs (T13 white rami) are controlled in part by tonic sympathoinhibitory influences which can be unmasked by blockade of the RVLM. These sympathoinhibitory influences do not appear to affect the activity of splanchnic and splenic nerves.

Adrenergic Fibers↗
PubMed1991

Some reflex cardioinhibitory responses in the cat and their modulation by central inspiratory neuronal activity.

1. Cats were anaesthetized with a mixture of chloralose and urethane, and were artifically ventilated. 2. An open pneumothorax was provided by two large-bore tubes which were sealed in the sixth intercostal space on each side. They were connected to a Fleisch pneumotachograph. Phasic changes in central inspiratory neuronal activity were measured quantitatively as changes in the volume of the pneumothorax during temporary interruption of artificial respiration, the volume of the lungs being held constant at their end-expiratory level. In this way the activity of slowly adapting pulmonary stretch receptors was maintained constant. 3. Reflex cardioinhibitory responses were elicited by stimulation of (a) the carotid body chemoreceptors by intracarotid injections of cyanide; (b) the arterial baroreflex by controlled elevations of the blood pressure; (c) cardiac receptors by left atrial injections of veratridine; and (d) pulmonary C fibres (including J receptors) by right atrial injections of phenylbiguanide. 4. The effects of central inspiratory neuronal activity on pulse interval were assessed by comparing the values observed during the inspiratory and expiratory phases of the respiratory cycle in the control state and during stimulation of each cardiovascular receptor group. 5. The carotid chemoreceptor-induced bradycardia measured during the expiratory phase of respiration was reduced during inspiration to a value of about 15% of control. The central inspiratory drive was less effective in altering the reflex responses from the arterial baroreceptors and cardiac receptors, the corresponding values being 42 and 51% respectively. 6. In contrast, the bradycardia evoked by pulmonary C fibre stimulation was not significantly affected by the central inspiratory drive. 7. The differential nature of the modulation by the central inspiratory drive occurred independently of the integrity of the sympathetic nerve supply to the heart indicating that the cardiac efferents involved were largely fibres in the vagus nerves. 8. The possible explanation of these results in terms of central mechanisms is discussed.

Animals↗
PubMed1995

Sensory origin of lobeline-induced sensations: a correlative study in man and cat.

1. Intravenous injections of lobeline HCl into twenty-six normal young male human volunteers produced sensations of choking, pressure or fumes in the throat and upper chest at a mean threshold dose of 12 micrograms kg-1. 2. Reflex changes in breathing pattern usually appeared just before the sensations. Increasing the dose of lobeline increased the intensity of the sensations gradually until a dry cough appeared at a mean threshold dose of 24.3 micrograms kg-1. At these doses there was a mean difference of 0.3s in the latencies for sensation and respiratory reflex; in four subjects there was no difference at all. 3. In cats anaesthetized with 35 mg kg-1 sodium pentobarbitone, injecting 25-67 micrograms kg-1 lobeline into the right atrium sensitized thirteen out of seventeen rapidly adapting receptors (RARs). In three out of four cats lobeline had no excitatory effect on the RARs in the absence of normal activity (i.e. when it was injected while artificial respiration was suspended), but on restarting the respiration the activity increased greatly. After injecting lobeline, the activity increased during inflation or deflation or in both phases of the respiratory cycle. It also increased greatly during deflation produced by suction of air from the lungs after lobeline. Such presumed increased activity in the RARs of man produced by forced expiration to residual volume at the time lobeline-induced sensations were expected did not enhance the sensations in any subject. 4. In all the subjects tested, forced expiration alone, which should stimulate RARs, never produced a dry cough or sensations similar to those produced by lobeline.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Inhalation↗
PubMed1991

[Hospital spread of scabies from an immunocompromised patient with Norwegian scabies].

Scabies was first found in a 71-year-old female who had been diagnosed as having leukemic transformation of primary myelofibrosis and had undergone treatment for the disease. She was admitted to the hospital in December 1986, because of abdominal fullness and a generalized subcutaneous tumor that proved to be myeloblastoma. For treatment of the underlying disease, the regimen of the combination of vindesine, cyclophosphamide, 6-mercaptopurine, and prednisolone was selected. She developed cardiac failure and fell into a coma one month after starting the anticancer therapy. She was put on artificial respiration and on additional steroid therapy as well. Dexamethasone was administrated at 16 mg/day. Since the myeloblastomas found on admission regressed, the steroid therapy was continued. She was in coma for a few days before her skin lesions turned red and formed a grayish crust in the lower abdominal region. Several days later, the doctor responsible for the treatment of this patient developed pruritus and exanthema on both arms, and soon many nurses in the same hospital-ward developed similar symptoms. At approximately the same time, the patient with myelofibrosis was diagnosed as having Norwegian scabies: the crusted skin lesions revealing many Sarcoptes scabiei mites. Two doctors (2/18), 17 nurses (17/19) and 3 other patients (3/51) were found to have contracted scabies, and we recognized the hospital spread of the infection. The first patient was isolated in a private room, and we avoided direct contact with her. The persons with scabies were treated with crotamiton liniment. The first scabies patient died of cardiac failure 1 month after falling into a coma.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1997

[Acute respiratory failure associated with G-CSF-induced leukocyte recovery in three patients with preceding infection].

Acute respiratory failure (ARF) occurred at the time of leukocyte recovery promoted by granulocyte colony-stimulating factor (G-CSF) in three patients with the preceding infection (S. aureus pneumonia, varicella zoster, and P. aeruginosa bacteremia, respectively) which had developed during leukopenia after cancer chemotherapy. G-CSF was used for 4 to 6 days, and the leukocyte counts at onset of ARF were 19,300/microliter, 11,300/microliter, and 4,100/microliter, respectively. All of the three patients received high-dose methylprednisolone and the artificial respiration was used in two. Consequently two patients responded well and survived, but one died of respiratory failure 2 weeks after occurrence of ARF. Autopsy of the dead case revealed mild interstitial pneumonia in the both lungs together with bacterial pneumonia in the right lobe. These cases indicate that G-CSF-induced leukocyte recovery can cause severe ARF in patients with precending infection. Therefore, G-CSF should be administered very carefully to granulocytopenic patients with infection.

Acute Disease↗
PubMed1968

Instrumental learning of vasomotor responses by rats: learning to respond differentially in the two ears.

Curarized and artificially respirated rats were rewarded by electrical stimulation of the brain for changes in the balance of vasomotor activity between the two ears. They learned vasomotor responses in one ear that were independent of those in the other ear, in either forepaw, or in the tail, or of changes in heart rate or temperature. In addition to implications for learning theory and psychosomatic medicine, these results indicate a greater specificity of action in the sympathetic nervous system than is usually attributed to it.

Animals↗
PubMed1979

Cortical plasticity in monocularly deprived immobilized kittens depends on eye movement.

A marked reduction of binocular cells in striate cortex is found if 4-week-old kittens are visually stimulated monocularly while anesthetized and held in a stereotaxic apparatus. If the kittens are paralyzed and artificially respirated, changes are not found unless an eye is moved mechanically. It appears that eye movement and visual stimulation are necessary conditions for deactivation of binocular connections, but neither is sufficient to induce such changes alone.

Animals↗
PubMed2006

Pinching, electrocution, ravens' beaks, and positive pressure ventilation: a brief history of neonatal resuscitation.

Since ancient times many different methods have been used to revive newborns. Although subject to the vagaries of fashion for 2000 years, artificial respiration has been accepted as the mainstay of neonatal resuscitation for about the last 40. Formal teaching programmes have evolved over the last 20 years. The last 10 years have seen international collaboration, which has resulted in careful evaluation of the available evidence and publication of recommendations for clinical practice. There is, however, little evidence to support current recommendations, which are largely based on expert opinion. The challenge for neonatologists today is to gather robust evidence to support or refute these recommendations, thereby refining this common and important intervention.

Asphyxia Neonatorum↗
PubMed1977

Negative-pressure plastic isolator for patients with dangerous infections.

A negative-pressure plastic isolator is effective for dealing with patients suffering from dangerous infections. So far it has been used to treat seven patients suspected of having infections due to Lassa, Marburg, or Ebola viruses. One patient spent 32 days in the isolator. The isolator was proved comfortable and acceptable to patients, and it gives the nursing and medical attendants a high degree of protection. All routine nursing and medical procedures can be carried out with minimal interference by the physical barrier, though it is not practicable to undertake artificial respiration or haemodialysis.

Atmospheric Pressure↗
PubMed1977

Measurement of postoperative pericardial pressure in man.

Pericardial pressure was measured in 18 patients undergoing cardiopulmonary bypass for up to 10 days using a solid state transducer. Mean and phasic pericardial pressure wave forms were similar to those reported in animals. A wide range of mean pressure from 0 to 30 mmHg was recorded, and values of up to 20 mmHg were observed in patients whose postoperative clinical course was uncomplicated. Fluctuations in pericardial pressure during spontaneous and artificial respiration were small, suggesting that concomitant left ventricular diastolic pressure changes were mainly the result of alterations in diastolic filling. Relative ventricular and pericardial distensibilities were estimated from the ratio of the slopes of diastolic pressure with time, which showed that up to 25 per cent of left ventricular diastolic pressure was supported by the pericardium and 75 per cent by the myocardium. Measurement of pericardial pressure had clinical value in 2 patients in confirming and excluding the presence of pericardial tamponade.

Adolescent↗
PubMed1974

Neurological manifestations of organophosphorous insecticide poisoning.

Neurological findings are described in 200 consecutive cases of suicidal ingestion of organophosphorous insecticides. Miosis is almost universal. We found impairment of consciousness in 10%, fasciculations in 27%, convulsions in 1%, toxic delirium in 50%, and paralysis in 26%. Toxic delirium was attributed to treatment with atropine. Paralytic signs were divided into type 1 signs (present on admission) and type 2 signs (appearing later while on atropine treatment). Type 1 signs, chiefly impaired consciousness and bilateral pyramidal tract signs, respond to atropine. The most common type 2 signs are proximal limb weakness, areflexia, and cranial nerve palsies. EMG studies during type 2 paralysis show a myasthenic response in some cases. Of 36 cases with type 2 signs 15 died from respiratory paralysis after a variable period of artificial respiration. Twenty-one recovered and no residual neurological deficit has been noted. Atropine did not influence type 2 paralysis. It is claimed that type 2 signs differ significantly from those described before as `delayed neurotoxicity' and may represent an alternative mode of human toxicity with organophosphorous compounds.

Facial Paralysis↗
PubMed1982

Survival after traumatic ponto-medullary tear.

Two children (aged 10 and 12 years) were admitted unconscious to the neurosurgical department after traffic accidents. Both developed a 6th nerve paralysis on the next day. One patient was able to communicate from the 2nd day and died on the 8th day in an anuric state without major neurological deficit. The second patient remained deeply comatose, tetraplegic, and required intermittent artificial respiration: She died of pneumonia on the 26th day. Neuropathological examination revealed a ponto-medullary rent in each case: additionally there was avulsion of small arteries over the pyramids, haemorrhage and small focal infarcts in the distribution of perforating arteries in the medulla and pons, and abundant retraction balls in longitudinal fibre tracts of the brain stem. The cases show for the first time that traumatic ponto-medullary tears are not always rapidly fatal, and demonstrate that primary focal brain stem trauma may occur in the absence of diffuse trauma of the white substance.

Cerebral Arteries↗
PubMed1976

Brown adipose tissue-a factor in the survival of harp seal pups.

The respiratory characteristics of mitochondria isolated from the subcutaneous brown adipose tissue of newborn harp seals indicate that the tissue is thermogenically active. Temperature recordings in vivo revealed, in fact, that the tissue was maintained at a temperature close to that of the body core during immersion of the pups in ice-water. Beta-adrenergic blockade markedly increased the cooling rates at both locations in ice-water, while curarization, accompanied by artificial respiration did not. We conclude that nonshivering thermogenesis through activated brown adipose tissue plays a decisive role in the defence against cold in the newborn harp seal.

Adipose Tissue, Brown↗