Donald C. Jackson

The effects of temperature and carbon dioxide breathing on ventilation and acid-base status of turtles

Abstract Respiratory minute volume (V e ) and oxygen consumption (V O 2 ) of freshwater turtles, Pseudemys scripta elegans , were measured at 10, 20 and 30 °C while the turtles breathed either air, 2, 4 or 6% CO 2 . In one series of animals arterial pH and P CO 2 , were measured as well and correlated with the ventilation. Inspired CO 2 caused hyperventilation which increased in proportion to either % inspired CO 2 or Pa CO 2 , and which reached about ten times the air-breathing ventilation when 6% CO 2 was breathed. The response was similar at each temperature. Ventilation (V e /V O 2 decreased with temperature with each breathing mixture, and, consequently, Pa CO 2 increased with temperature. The influence of temperature on the ventilatory control of Pa CO 2 when the turtles breathed air was the physiological mechanism responsible for the inverse relationship between blood pH and temperature.

Thermal response patterns of septal and preoptic neurons in cats

The thermosensitivities of preoptic and septal neurons were studied in Urethan-anesthetized or decerebrated cats. Local brain temperature was varied over an 8 C range using water-perfused thermodes while single unit activity was recorded with steel microelectrodes. The thermosensitivities of neurons showing a smooth, continuous relationship of firing rate to temperature were characterized by their Q10. The slopes of the thermal response curves for all such units were positive. The Q101 and Q102 units were distributed widely through the septum and preoptic area, and are assumed to be unspecialized in their thermosensitivity. Units with Q10 > 2 were localized in the dorsal preoptic area and ventral septum, and are considered to be the central thermosensors responsible for monitoring brain or core temperature. The Q101 units showed a marked decrease in firing rate or a change in response pattern following injection of barbiturate (Methohexital Sodium, “Brevital”), while units of Q102 or greater were relatively insensitive to anesthetic depression. Another class of responses was characterized by a sharp change in slope of the thermal response curve at some set temperature. Both units which fired at higher rates when cooled and units with higher firing rates when warm were found. These were distributed through the septum and rostral preoptic area. Units with this type of response were very sensitive to barbiturate anesthetic. Based on their thermoresponsiveness, distribution, and anesthetic sensitivity they are considered to be interneurons in the thermoregulatory pathways. In a given preparation, whether anesthetized or decerebrated, several of these classes of response could be recorded, although all were not obtained from any one animal.

Ventilatory response to hypoxia in turtles at various temperatures

Abstract Respiratory minute volume (/.V e ) and respiratory gas exchange (/.V o 2 and /.V co 2 ) of fresh water turtles, Pseudemys scripta elegans , were measured at 10°, 20° and 30 °C while the turtles breathed either air, 10%, 5% or 3% O 2 . The Pi o 2 , values at 10 °C were 155, 73, 38 and 23 torr, respectively. Hyperventilation was evaluated by 1) the peak increase in /.V e over the air-breathing value and by 2) the increase in the /.V e //.V co 2 ratio when the response to the hypoxic gas reached a steady-state level. By both criteria, hypoxia-induced hyperventilation was observed at a higher Pl o 2 when body temperature was higher. At 30 °C, turtles hyperventilated breathing 10% O 2 , at 20 °C breathing 5% O 2 , while at 10 °C, only slight hyperventilation occurred even when turtles breathed 3% O 2 . When hyperventilation was observed, it was due to increases both in f and Vt. Three factors are suggested to account for the greater response at high temperature: 1) increased /.V o 2 due to Q 10 effect, 2) lower relative ventilation, /.V e //.V o 2 , of air breathing turtles which amounts to hypoventilation with increased temperature, and 3) reduced affinity of hemoglobin for O 2 .

Buoyancy Control in the Freshwater Turtle, Pseudemys scripta elegans

Freshwater turtles (Pseudemys scripta elegans) significantly corrected experimental displacements of their specific gravity. By reciprocally changing the volumes of lung air and stored water, they set their buoyancy and maintained their body volume. The cloacal bursae may be the active site for water storage and exchange in this mechanism.

Late complications of abdominal aortic reconstructive surgery: roentgen evaluation.

During a 5-year period from 1969 to 1974, 53 (8.5%) of 631 patients developed late complications following abdominal aortic reconstructive surgery. Occlusion was the most frequent complication and occurred in 4%. Others included stenosis, false aneurysm, enteric fistula and infection. Late complications were demonstrated by roentgenographic methods. Angiography was the most valuable roentgen study. It is indicated in all patients suspected of having delayed complications except those with unstable life-threatening hemorrhage. Additional roentgenographic studies including the barium enema and barium meal may help make the diagnosis and exclude other entities. In any patient with an abdominal aortic graft and gastrointestinal bleeding, the diagnosis of an aorto-enteric fistula should be considered until otherwise proven.

The effect of temperature on ventilation in the green iguana (Iguana iguana).

Abstract 1. 1. Respiratory minute volume ( V E ) and oxygen consumption ( V O 2 ) were measured simultaneously in the green iguana, Iguana iguana , at 20, 30 and 35°C. The volume of air the iguanas breathed per unit of oxygen consumed ( V E V O 2 ) decreased with temperature. 2. 2. These results are similar to those of Jackson (1971) for the turtle and support the hypothesis that reptiles adjust their breathing at different temperatures in order to maintain constant relative alkalinity of their blood.

Experimental Closure of Arteriovenous Fistula by Transcatheter Electrocoagulation

Introduction of a small electric current by way of a catheter-placed electrode can completely occlude experimentally produced arteriovenous fistula. The occlusion appears permanent and without morbidity in experimental animals. This technique might be clinically useful in obliterating an arteriovenous fistula and controlling gastrointestinal hemorrhage.

Vessel Occlusion with Transcatheter Electrocoagulation: Initial Clinical Experience

Transcatheter electrocoagulation (TCEC) was used for vessel occlusion in combination with embolization by Gelfoam and/or Ivalon in six patients in whom other interventional or surgical techniques were considered dangerous or unfeasible. The technique was effective in decreasing or obliterating the blood supply to variously located lesions in all cases. The only complications were small skin burns in one patient and a small ulceration of the upper lip in another.

Transcatheter electrocoagulation: a therapeutic angiographic technique for vessel occlusion.

Previous work has shown that localized electrocoagulation of blood vessels using direct current applied by catheter placed electrodes is feasible. In vitro and in vivo experiments showed that clot size and thrombosis of vessels are directly related to the product of the amount and duration of the current. Surgically created splenic hemorrhage was well controlled in 9 of 10 animals. The vessels remained permanently occluded after electrocoagulation in 8 of 9 animals. Pathological studies of all the vessels showed intimal damage at the sites of occlusion. These experiments indicate that clot formation may be a product of both intimal damage and platelet attraction to the positive electrode. The technique has advantages over embolization since no foreign material is injected and a localized clot is produced at the tip of the guidewire. There are certain disadvantages and further refinements must be developed to establish transcatheter electrocoagulation as a useful clinical technique for vessel occlusion.

Clinical Use of Transcatheter Electrocoagulation

Transcatheter electrocoagulation is an effective method of experimental vessel occlusion even in the presence of thrombocytopenia and heparinization. This technique was used to occlude 13 arteries in 3 patients. In vitro testing suggests that intra-arterial bipolar platinum electrodes may achieve the therapeutic objectives more rapidly and with less risk, but more investigative work is required.