Biomedical subjects

R A Furilla

Publications and source records attributed to R A Furilla.

7 recordsLinked to original sources

PubMed1992

Tissue distribution, elimination, and metabolism of [3H]leukotriene C4 by the conscious marine toad, Bufo marinus.

Tissue distribution, elimination, and metabolism of 3H-labelled leukotriene (LT) C4 were studied in ureter-catheterized conscious marine toads, Bufo marinus. Six and 24 h after injection, organs containing the highest percent of injected radioactivity were small intestine, liver, and kidney. Radioactivity declined in these organs at 24 h by approximately threefold. Peak elimination time for radioactivity in the urine was between 2 and 4 h after the injection. During the 24-h collection period, 55.2 +/- 0.2% of the injected radioactivity was eliminated in the urine. Polar metabolites represented 40.3 +/- 1.1, 57.3 +/- 5.6, and 62.8 +/- 1.6% of the radioactivity at 2, 4, and 6 h, respectively. The primary urinary polar metabolite was 20-carboxy-LTE4, with 18-carboxydinor-LTE4 and 20-hydroxy-LTE4 also present. [3H]LTE4 decreased from 37.2 +/- 1.8% at 2 h to 15.8 +/- 3.3 and 15.0 +/- 2.1% of the radioactivity at 4 and 6 h, respectively. Bile radioactivity was low. N-Acetyl-LTE4 was not detected in urine or bile samples. Radioactivity in the pan water was 14.3 +/- 2.4 and 15.8 +/- 2.5% of the injected radioactivity, at 6 and 24 h, respectively, suggesting that the skin was a route for excretion of leukotrienes. The marine toad is an interesting model demonstrating both similarities and differences from mammals in distribution, elimination, and metabolism of peptide leukotrienes.

Animals↗

PubMed1991

A decrease in nasal CO2 stimulates breathing in the tegu lizard.

Tegu lizards decrease ventilatory frequency (f) when constant CO2, as low as 0.4%, is delivered to the nasal cavities. In contrast, CO2, as high as 6%, pulsed into the nasal cavities during the expiratory phase of the breathing cycle does not alter f. The purpose of the present study was to investigate further the effect of nasal CO2 pattern on f in tegu lizards. Specifically, we tested: (1) whether f was affected by CO2 delivered to the nasal cavities during the inspiratory phase of the breathing cycle, and (2) whether pulsed decreases in nasal CO2 from 4% to 2% and from 4% to 0% would remove the f inhibition caused by constant nasal CO2. Ventilation was measured using a pneumotachograph and pressure transducer in-line with an endotracheal T-tube inserted through the glottis. CO2 was delivered to the nasal cavities through small tubes inserted into the external nares. Ventilatory frequency was not significantly altered when 4% CO2 was pulsed into the nasal cavities during inspiration. Dropping the CO2 in the nasal cavities from 4% to 0% at either 15 cycles/min (0.25 Hz) or for one cycle stimulated breathing. There was no significant difference between the f response to a drop in CO2 from 4% to 0% and that to a drop in CO2 from 4% to 2%. The failure to link the phasic CO2 ventilatory response to a phase in the respiratory cycle indicates that the nasal CO2 receptors do not participate in the breath-by-breath regulation of breathing in these lizards. The observation that small decreases in nasal CO2 abolished the f inhibition caused by constant nasal CO2 provides further evidence for the ability of the nasal CO2 receptors to distinguish between pulsed and constant CO2.

Animals↗

PubMed1991

The influence of venous CO2 on ventilation in garter snakes.

Garter snakes were used to study the effects of venous CO2 loading using the skin as an exchanger. The gaseous environment surrounding the snake's body was isolated by placing the body in a plethysmograph with the head out. While the animal breathed room air, the carbon dioxide concentration within the plethysmograph was varied between 0 and 80%. Room air was drawn through a funnel placed over the snake's head, thus collecting the exhaled gases, and this gas was analyzed by O2 and CO2 analyzers. The descending aorta was cannulated to measure blood gases. Expired CO2 flow rose linearly with increasing cutaneous CO2. Ventilation increased 3.5-fold at 80% cutaneous CO2 compared with no cutaneous CO2 load. Neither the mean CO2 concentration in exhaled air nor arterial PCO2 changed when the snake was exposed to high levels of CO2 at the skin. Thus ventilation increased in proportion to the CO2 load, and was not driven by arterial hypercapnia. Bilateral vagotomy eliminated arterial CO2 homeostasis during cutaneous CO2 loading, and ventilation increased with increasing arterial PCO2. Therefore, these snakes respond to extra-arterial elevations in CO2 or to a changing CO2 signal. Furthermore, receptors responsible for the increase in ventilation when venous CO2 is elevated have neurons in the vagus nerves.

Animals↗

PubMed1991

Rate of rise of intrapulmonary CO2 drives breathing frequency in garter snakes.

Garter snakes increase ventilation in response to elevated venous PCO2 without a concomitant rise in arterial PCO2 (Furilla et al. Respir. Physiol. 83: 47-60, 1991). Elevating venous PCO2 will increase the PCO2 gradient between pulmonary arterial blood and intrapulmonary gas during inspiration, leading to a greater rate of rise of intrapulmonary CO2 after inspiration. Because the lung contains CO2-sensitive receptors, I assessed the effect of the rate of rise of intrapulmonary CO2 on ventilation in unidirectionally ventilated snakes. CO2 concentration was altered using a digital gas mixer connected to a personal computer. Breathing frequency was highly correlated with the rate of rise intrapulmonary CO2 but only slightly affected by peak intrapulmonary CO2. On the other hand, tidal volume was more closely related to peak intrapulmonary CO2 than to the rate of rise of CO2. Bilateral pulmonary or cervical vagotomy nearly eliminated the ventilatory response associated with altered CO2 rise times but had little influence on the tidal volume response to the rate of rise of CO2. The mechanism whereby breathing frequency is controlled by the rate of rise of intrapulmonary CO2 is likely to originate with intrapulmonary chemoreceptors and may be important in the control of breathing during exercise.

Animals↗

PubMed1989

Intrapulmonary CO2 inhibits inspiration in garter snakes.

This study was undertaken to assess the role of intrapulmonary chemoreceptors in the control of breathing in reptiles. Garter snakes were tracheostomized to remove the influence of upper airway receptors. After recovery from anesthesia, the animals were unidirectionally ventilated or allowed to ventilate normally, but without glottal control of the breath-hold. Breathing movements were recorded by means of a pneumotachograph. When a bidirectionally breathing snake was presented with CO2 at the tracheal tube, inspiratory duration and volume decreased. When CO2 was removed from the inspired air between breaths, inspiratory duration and volume increased. Removing CO2 from the airstream of a unidirectionally ventilated snake during a breath-hold produced apnea, but removing CO2 at the beginning of inspiration caused the duration and volume of the inspiration to increase. This reflex appears to represent a positive feedback mechanism for enhancing inspiration once a breath has been initiated.

Animals↗

PubMed1988

Intrapulmonary receptors in the garter snake (Thamnophis sirtalis).

Receptors in the respiratory system of anesthetized, unidirectionally ventilated garter snakes were analyzed from single-unit vagal recordings. Three types of receptors were found: rapidly adapting mechanoreceptors (RARs), slowly adapting pulmonary stretch receptors (SARs) and intrapulmonary chemoreceptors (IPCs). RARs gave a burst of activity when the lung was inflated or deflated. Discharge frequency of SARs increased during a sustained elevation of intrapulmonary pressure (PIP); a step increase in PIP usually caused an overshoot in receptor activity that slowly adapted to a new tonic level during the sustained inflation. The activity of intrapulmonary chemoreceptors (IPCs) decreased when airway CO2 was raised. A sudden removal of CO2 caused a striking overshoot in activity which slowly adapted. Receptor discharge of SARs and IPCs was studied at 20, 25 and 30 degrees C. Discharge frequency increased with increasing temperature. The Q10 of discharge frequency averaged 3.0 for IPCs and 1.5 for SARs. Temperature clearly had a profound effect on pulmonary receptor activity; however, the relative change of activity of IPCs or SARs to a given stimulus was similar regardless of body temperature, and since the body temperature of snakes varies considerably, this may have important implications regarding the control of breathing in these animals.

Animals↗

PubMed1986

The contribution of nasal receptors to the cardiac response to diving in restrained and unrestrained redhead ducks (Aythya americana).

In restrained redhead ducks, forced submergence caused heart rate to fall from 100 +/- 3 beats min-1 (mean +/- S.E.M., N = 12) to a stable underwater rate of 35 +/- 4 beats min-1 (N = 12) within 5 s after submergence. Bradycardia was unaffected by breathing oxygen before a dive, but was virtually eliminated by local anaesthesia of the narial region. In contrast, in a dabbling duck (Anas platyrhynchos) bradycardia in short dives was eliminated by breathing oxygen before a dive. In unrestrained diving, on a man-made pond, heart rate in redheads diving voluntarily (y) was related to pre-dive heart rate (x) by the equation y = 76 + 0.29 +/- 0.05x +/- 17 (r2 = 0.71). Chasing, to induce submergence, had variable effects on this relationship. Local anaesthesia of the narial region inhibited voluntary diving but heart rates in chase-induced dives after nasal blockade were significantly higher, by 10-30%, than those obtained from untreated ducks in chase-induced dives. Breathing oxygen before voluntary dives had no apparent effect on heart rate after 2-5 s submergence. Voluntary head submersion by dabbling ducks caused no change in heart rate. We conclude that nasal receptors make only a minor contribution to cardiac responses in unrestrained dives, compared with forced dives, in diving ducks. Furthermore, these results show that little can be learned about cardiac responses in free diving ducks from studies of forced dives in dabblers or divers.

Anesthesia, Local↗