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Biomedical subjects

A C Hansen

Publications and source records attributed to A C Hansen.

At least 55 records · Page 3Linked to original sources
PubMed1979

Balance of net base in the rat: adaptation to and recovery from sustained hypercapnia.

Net base and mineral balances were evaluated in a group of male 350 g Wistar rats exposed to 10% carbon dioxide in air for 10 days with a view to identifying the source of net base subject to retention during renal compensation of sustained respiratory acidosis. In response to hypercapnia, the rate of renal net acid excretion rose but insignificantly. However, a rise in whole body net base concentration from about 215 mmol/kg to about 250 mmol/kg came about by ongoing gastrointestinal absorption in the weight-losing animal, absorbed net base being distributed to extracellular and non-extracellular compartments of the body, presumably including bone. During an 8-day recovery period, a small decrement in whole body net base concentration was observed.

Acid-Base Equilibrium↗
PubMed1978

Balance of net base in the rat. III. Effects of oral sodium bicarbonate and sodium citrate loading.

The balance of net base in groups of male weanling Wistar rats exposed to sustained oral loads of net base were studied. In response to dietary loads of sodium bicarbonate (approx. 50 mmol.kg-1.day-1) an average increment in the mean rate of retention of net base of 21.8 mmol.kg-1.day-1 was observed in the absence of significant changes in the blood 'base excess'. Following withdrawal of sodium bicarbonate, mean rates of gastrointestinal absorption, renal excretion, and retention of net base promptly returned to control values, accumulated net base being retained in the body, presumably as skeletal sodium carbonate. In response to equimolar loads of net base in the form of trisodium citrate, a similar, albeit less pronounced, rise in the rate of retention of net base occurred.

Acid-Base Equilibrium↗
PubMed1978

Balance of net base in the rat. IV. Effects of oral calcium and phosphate loading.

Mineral and net base balances were studied in groups of male weanling Wistar rats given oral loads of calcium chloride, monocalcium phosphate plus monosodium phosphate, and disodium phosphate plus monopotassium phosphate, respectively. A group of adult nongrowing rats loaded with calcium chloride was included for comparison. In response to CaCl2 loading, gastrointestinal net base absorption was inhibited due, largely, to luminal precipitation of tertiary phosphates of calcium and magnesium. In the weanling animal, however, a rise in the rate of renal net acid excretion matched the concomitant decrement in the rate of net base absorption, permitting of continued skeletal net base storage. Similarly, in the adult animals augmented renal net acid excretion offset a positive rate of gastrointestinal net acid absorption with a resultant (normal) zero net base balance. Loading with monocalcium phosphate and disodium phosphate at a constant oral net base intake did not influence the overall net base balance, but disodium phosphate loading caused significant sodium retention.

Acid-Base Equilibrium↗
PubMed1968

Norrie's disease.

Explore the source record for details and available documents.

Blindness↗
PubMedDate not supplied

A blood pump with an interatrial shunt for use as an electrohydraulic total artificial heart.

A recently designed blood pump subsystem for the completely implantable electrohydraulic total artificial heart (EHTAH) has been developed and is under evaluation. The subsystem consists of joined left and right ventricles, atrial cuffs with an interatrial shunt (IAS), and two outflow grafts. The ventricles were developed to fit within the pericardial space based on the results of anatomic fit trials. An optimized configuration for animal use, which was adaptable for human use with minimal modification, was identified. The core dimensions of the ventricles with an energy converter are approximately 10 x 11 x 7 cm. Maximum output and stroke volume are 9.2 L/min and 81 ml, respectively. The IAS is used to balance the volumetrically coupled EHTAH, and is made by forming an orifice in the common septum of the left and right atrial cuffs. Performance and durability of the IAS were examined in animal experiments for up to 9 days. The diameter of the IAS was 3.4-5.5 mm, and the left-right atrial pressure difference ranged from 2 to 10 mmHg, with 0.57-1.48 L/min of theoretically calculated shunt flow. No evidence of thrombus formation was found in or around the IAS at autopsy. The entire EHTAH system with a new blood pump is being assembled for long-term animal studies.

Animals↗
PubMedDate not supplied

Development of a totally implantable artificial heart.

The first generation of an integrated, totally implantable electrohydraulic total artificial heart was designed for long-term cardiac replacement. The system consists of an elliptical blood pump with an interatrial shunt, Medtronic-Hall 27 mm and 25 mm inflow and outflow valves, respectively, an energy converter consisting of an axial-flow, hydraulic pump driven by a brushless DC motor, and an electronics system with transcutaneous energy transmission and telemetry. Energy is supplied by internal nickel-cadmium rechargeable batteries that supply power for 20 min and external silver-zinc batteries that are designed to supply energy to run the system for 5 hr. The blood pump consists of a single layer diaphragm cast from Biolon, with joined right and left ventricles sharing a common base. The dynamic stroke volume is 84 ml, and maximum cardiac output is 9.2 L/min at a heart rate of 110 beats/min on the mock circulation. A 4.3 mm diameter interatrial shunt is used to balance the volumetrically coupled ventricles. The energy converter pumps hydraulic fluid alternately between ventricles, with controlled, active filling in one ventricle during the systolic phase of the other ventricle. Internal or external controllers adjust the heart rate and motor speed to maintain normal atrial filling pressures and full stroke. Electromagnetic induction is used to transfer energy through the skin and a bidirectional infrared data link incorporated within the transcutaneous energy transmission coils is used to transmit information. The entire system is being assembled and refined for long-term animal implant studies.

Algorithms↗
PubMedDate not supplied

Electrohydraulic ventricular assist device development.

A 64 ml (effective stroke volume) in vitro electrohydraulic ventricular assist device (VAD) prototype has been built. The energy converter is an axial flow pump driven by a brushless direct current (DC) motor. Systole begins as silicone oil is pumped from the volume displacement chamber (VDC) into the ventricle, displacing the flexing diaphragm separating the oil and the blood. In diastole, the motor reverses, providing active filling by pumping oil from the ventricle into the VDC. The surface mount electronic internal controller provides motor commutator, energy management, telemetry, and physiologic control functions. Energy is supplied externally by either a 12 V DC power supply or a 12 V DC rechargeable battery and is transmitted through the skin by a transcutaneous energy transformer (TET). Energy can also be supplied by a 12 V DC rechargeable internal battery. Bidirectional infrared telemetry is used to transmit information between the internal and external controllers.

Blood Pressure↗