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Biomedical subjects

R A Jaffe

Publications and source records attributed to R A Jaffe.

14 recordsLinked to original sources
PubMed1992

Difficulty in extubation. A cause for concern.

Difficulties in removing the tracheal tube from the trachea are relatively uncommon. We report here a case of difficult extubation which was precipitated by pulling off the pilot balloon and valve assembly in order to deflate the cuff.

Adult↗
PubMed1992

Aspects of mechanical ventilation affecting interatrial shunt flow during general anesthesia.

Intraoperative transesophageal echocardiography was used to study the incidence of flow-patent foramen ovale in 33 normal, healthy patients (ASA physical status I) undergoing general anesthesia in the supine position for nonthoracic surgical procedures. Echocardiographic contrast was injected intravenously during mechanical ventilation in the presence of 0, 5, 10, 15, or 19 cm H2O positive end-expiratory pressure (PEEP). A final test was performed during the release of 19 cm H2O PEEP. The presence of a flow-patent foramen ovale was detected when the injected echo targets were observed crossing the interatrial septum from right to left. Most interesting, 3 of 33 patients developed a right-to-left shunt that was first detected with the steady application of 10 (1 patient) or 15 cm H2O PEEP (2 patients). In all three cases, the shunt flow was accentuated on the release of PEEP; however, no additional cases were detected using this respiratory maneuver. These cases represent the first demonstration of right-to-left interatrial shunting evoked as the result of the sustained application of PEEP. This study also revealed a lower than expected incidence of flow-patent foramen ovale (9%) when measured during general anesthesia and positive pressure ventilation with or without PEEP.

Adult↗
PubMed1978

Effects of droperidol on activity of carotid body chemoreceptors in cat.

1 The effect of droperidol on the spontaneous activity of carotid body chemoreceptors and on their response to various stimuli was studied in 21 anaesthetized, paralyzed and artificially ventilated cats. Carotid body blood flow was controlled with a perfusion pump, and drugs were injected into the perfusion circuit. 2 In low doses, droperidol transiently increased the rate of spontaneous chemoreceptor activity, but in higher doses it depressed chemoreceptor activity after an initial stimulation. 3 Droperidol reduced or abolished the normal increase in chemoreceptor activity produced by stagnant asphyxia. This effect did not depend solely on the ability of droperidol to suppress spontaneously occurring impulses. Chemoreceptor responses to sodium cyanide, and to dopamine were also inhibited. 4 Dopamine antagonists other than droperidol were also studied for their effect on chemocreceptor activity. Chlorpromazine depressed spontaneous chemoreceptor activity and also reduced the chemoreceptor responses to sodium cyanide and dopamine, as did pimozide. The effects of these dopamine antagonists were much briefer and less marked than those of droperiodol. 5 Although the influence that we have shown droperidol to have on peripheral chemoreceptor activity has an uncertain basis, it may have important implications in human and veterinary medicine.

Animals↗
PubMed1976

Analysis of inhibitory effect of dopamine on carotid body chemoreceptors in cats.

The inhibitory effect of dopamine on carotid body chemoreceptors was studied in anesthetized cats to determine whether it was dependent on changes in blood flow in the vicinity of the receptors. The blood supply to the carotid body was isolated, and flow was controlled with a perfusion pump. Single- or few-fiber recordings were made from the peripheral end of the cut carotid sinus nerve in seven cats. The rate of discharge of 68 chemoreceptor strands increased when flow through the carotid body was stopped. This response was reduced or abolished by dopamine in animals ventilated with either room air (15 strands) or a gas mixture of 95% O2 and 5% CO2 (53 strands). These results suggest that dopamine exerts its inhibitory effect primarily through a direct action on the chemoreceptors rather than by a vasomotor effect in the carotid body.

Animals↗
PubMed1976

Analysis of passive and active electrophysiologic properties of neurons in mammalian nodose ganglia maintained in vitro.

1. We studied the passive and active electrical properties of the soma membrane of neurons in nodose ganglia removed from cats and rabbits and maintained in vitro. The ganglia were superfused at 37 degrees C with a solution formulated to approximate the extracellular fluid of each species. The solution was buffered to pH 7.34, continuously equilibrated with 95% O2 and 5% CO2, and contained dialyzed calf serum and glucose. We also examined these properties in nodose ganglion neurons in vivo. Intracellular recordings were obtained with glass micropipettes filled with either 3 M KCl or 5 M K acetate. 2. We determined mean values for a variety of passive and active electrophysiologic properties. Values obtained in vitro did not differ significantly from those obtained in vivo. Based on the passive electrical properties of the soma membrane, neurons in the nodose ganglion appear to be a uniform population, despite the different sensory modalities conveyed by the afferent fibers. 3. Cell bodies of neurons generated action potentials in response to impulses in their afferent fibers. Somatic spikes could be evoked by stimulation of either the supranodose or infranodose vagus nerve, and an inflection point could be seen on their rising phase. When the vagus nerve was stimulated at frequencies greater than 10-20 Hz, the generation of somatic spikes often became progressively delayed and then failed completely, leaving a smaller potential (IS spike) which was apparently generated in the initial complex. The afterhyperpolarization was associated only with the somatic spike. 4. Many neurons, both in vitro and in vivo, developed a persistent hyperpolarization when repetitive action potentials occurred in the soma. This hyperpolarization was apparent at frequencies as low as 1-2 Hz, persisted for up to 5 s after the occurrence of the last somatic spike, and sometimes caused failure of somatic spikes to be generated. 5. Neurons in both species differed in their responses to suprathreshold depolarization applied through the recording electrode. Some neurons produced a train of action potentials which lasted for the duration of the depolarizing pulse, the frequency of the train being related to the magnitude of depolarization. The trains were characterized by gradually decreasing spike amplitudes and increasing interspike intervals. Other neurons responded with only a single spike or brief burst of action potentials at the beginning of depolarization to threshold. 6. It is suggested that the adaptive properties of the soma membrane of a peripheral sensory neuron are similar to those of its sensory ending, and that electrophysiological studies of the soma membrane may provide an opportunity to examine mechanisms of receptor adaptation.

Action Potentials↗
PubMed1976

A pharmacological analysis of neurally induced inhibition of carotid body chemoreceptor activity in cats.

Experiments were performed to determine the mechanism by which centrifugal impulses in the carotid sinus nerve (CSN) reduce the frequency of impulse traffic in afferent chemoreceptor fibers from the carotid body in cats. Recordings of chemoreceptor activity were made from single- or few-fiber preparations dissected off the CSN, while the remainder of the CSN was stimulated electrically to produce neurally induced inhibition of chemoreceptor activity. Various drugs were injected either intravenously or directly into the arterial blood supply to the carotid body. We found that catecholamines (dopamine, norepinephrine and epinephrine) inhibited spontaneous chemoreceptor activity, and that alpha adrenergic antagonists abolished both this inhibition and that produced by electrical stimulation of the CSN in the same preparation. Atropine, but not nicotinic antagonists of acetylcholine, consistently blocked neurally induced inhibition but not that produced by catecholamines. Muscarinic agonists had no effect on spontaneous chemoreceptor activity. We conclude that centrifugal activity in the CSN causes release of endogenous catecholamines in the carotid body, and that these catecholamines mediate neurally induced inhibition of chemoreceptor activity is due to the vasomotor effects of acetylcholine.

Acetylcholine↗
PubMed1975

Influence of centrifugal sinus nerve activity on carotid body catecholamines: microphotometric analysis of formaldehyde-induced fluorescence.

The effects of centrifugal activity in the carotid sinus nerve (CSN) on the intensity of formaldehyde-induced fluorescence of carotid body were examined in cat. Measurements of intensity were obtained from 21 to 56 sections of each carotid body with a microscope photometer attached to a fluorescence microscope. Comparisons were made between the two carotid bodies removed from each cat. In one series of experiments, one carotid body (CSN intact) served as control, while the experimental carotid body was on the side on which centrifugal activity was increased by electrical stimulation of the peripheral end of the cut CSN. In a second series, centrifugal CSN activity was increased by hypoxemia; one CSN was transected (control) and the other was left intact (experimental). In untreated cats, fluorescence intensity was significantly higher on the side with increased centrifugal CSN activity. In cats treated with either MK486, which inhibits conversion of L-DOPA to dopamine, or reserpine, increased centrifugal CSN activity caused a significant decrease in intensity of type I cells. These findings indicate that centrifugal discharges regulate, in part, the synthesis and release of catecholamines by type I cells of the carotid body.

Carbidopa↗
PubMed1975

Dynamics of venous-arterial testosterone transfer in the pampiniform plexus of the rat.

The dynamics of venous-arterial testosterone transfer in the pampiniform plexus of the rat have been studied using [3-H] testosterone in controlled perfusion in the pampiniform plexus isolated from its testicle in vivo. The rate of transfer of testosterone increased in direct proportion to the testosterone concentration in spermatic vein blood over the range 0-100 ng/ml. When the venous-arterial concentration gradient was reversed by infusing [14-C] testosterone into the spermatic artery proximal to the pampiniform plexus, the label was transferred from the artery to the adjacent spermatic vein. Transfer of [3-H] methoxy-inulin infused concomitantly with the [14-C] testosterone was relatively insignificant in either direction. The testosterone transfer rate generally increased with increasing blood flow over the range 0.01-0.36 ml/min. However, transfer rate became less dependent on blood flow at the high end of the range. A comparison of transfer rates from whole blood and dextran (6% in saline) each containing 24-27 ng [1,2-3-H] testosterone/ml and flowing at 0.36 ml/min for one hour resulted in a maximum of 6.1% transfer from blood and 46% transfer from dextran. Transfer from blood reached plateau levels in less than 10 min, whereas transfers from dextran peaked between 30 and 40 min. At lower rates testosterone transfer from dextran reached equilibration levels, whereas transfer from blood rarely exceeded 5% of spermatic venous levels. We concluded that venous-arterial steroid transfer in the pampiniform plexus behaves like a passive countercurrent diffusion system that is concentration limited, depending principally on the concentration gradient of diffusible steroid between the closely juxtaposed spermatic vein and artery.

Animals↗