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Biomedical subjects

D B Stephens

Publications and source records attributed to D B Stephens.

At least 37 records · Page 2Linked to original sources
PubMed1982

Effect of albumin and mannitol on organ blood flow, oxygen delivery, water content, and renal function during hypothermic hemodilution cardiopulmonary bypass.

The present study was designed to determine if the addition of albumin or mannitol to the priming solution of the pump oxygenator would diminish edema in organs, without diminishing some of the beneficial effects of hemodilution on blood flow and renal function. Tissue blood flow (15 mu spheres), water content, and renal clearances were determined in 8 animals during cardiopulmonary bypass. A 2(2) factorial, completely fixed experimental design was used. All animals were placed on cardiopulmonary bypass with hemodilution (hematocrit 25 +/- 2%) and hypothermia (25 degrees +/- 1 degree C). Albumin decreased flow to the midmyocardium of the left ventricle and to the spleen, and increased flow to the inner cortex of the kidney. Albumin caused decreased urine flow and decreased urine sodium, and also diminished renal osmolar, sodium, and free-water clearances. both mannitol and albumin decreased lung water. Mannitol decreased water content of the outer renal cortex, and decreased flow to the inner cortex and medulla of the kidney and to the spleen. Mannitol had no significant effect on urine flow, renal plasma flow, or renal clearances. Neither albumin nor mannitol had any effect on water content of the intestine, stomach, liver, or myocardium where the greatest accumulation of water occurs with hemodilution. The effect of albumin on renal function is potentially deleterious during cardiopulmonary bypass because it decreases urine flow, and osmolar and free-water clearance.

Animals↗
PubMed1982

Operative experience with 50 thoracic aortic dissections.

From 1971 to 1981, 46 patients were subjected to 50 operations (graft replacement, 31; patch aortoplasty, ten; suture aortorraphy, six; bypass, one; and nonthoracic vascular procedure, two) for thoracic aortic dissection. Four patients had two separate dissections. Dissections were classified as type A (ascending thoracic aortic, 38) or type B (descending thoracic aortic, 12) and subgrouped as acute (less than 2 weeks) or chronic (greater than 2 weeks). There were seven hospital deaths and an operative mortality of 14%. The operative mortality for acute type A dissections was 20% and for chronic type A, 7%. There was one operative death in the 12 type B dissections. Four of the seven deaths occurred in patients with an iatrogenic dissection. Overall cumulative survival was 70% at four years, but dropped to 45% at six years. Survival was poorest in the acute type A group and was only 38.9% at five years.

Adolescent↗
PubMed1982

Observations on the effects of vibration stress and sound on pregnancy, parturition and respiration in the rabbit.

Rabbits, 5-29 days pregnant, were placed for 2 h either in or near a machine designed to simulate transport, which exposed them to vibration stress and sound. There was no apparent effect on the maintenance of pregnancy, gestation length, litter size, perinatal mortality or condition of the young at birth compared with control rabbits. However, respiration rate, normally 65/min, was increased to 120/min by moving the animals from their cages and to 160/min in the machine; noise alone produced an intermediate response. Respiration returned to normal values after 20 min to 4 h, depending upon the initial level of response.

Acoustic Stimulation↗
PubMed1981

Blood conservation techniques.

Increasing numbers of operations requiring cardiopulmonary bypass have been accompanied by greater demands for blood resources. Improved techniques of blood conservation have diminished the average blood requirements per operation and have increased the percent of operations that can be done without homologous blood. The conservation of blood can be planned according to each patient's requirements. The techniques include preoperative blood donation, intraoperative withdrawal of blood, reinfusion of oxygenator blood, autotransfusion of blood after heparin neutralization, autotransfusion after wound closure, and hemodilution. The availability of techniques for filtration, centrifugation, and washing of blood have improved the safety of autotransfusion. The techniques that gives the best cost/benefit ratio appear to be preoperative withdrawal of blood, reinfusion of centrifuged oxygenator contents, and reinfusion of filtered blood from chest drainage.

Blood Transfusion↗
PubMed1981

Effects of hypothermia, hemodilution, and pump oxygenation on organ water content, blood flow and oxygen delivery, and renal function.

Hypothermia, hemodilution, and the pump-oxygenator each contribute important effects during cardiopulmonary bypass. We studied their separate effects with a 2(3) factorial, completely fixed experimental design in 16 adult male mongrel dogs. Animals undergoing hypothermia were cooled to 25 degrees +/- 1 degree C. In dogs having hemodilution, hematocrit was adjusted to 25 +/- 2%. An analysis of variance was used to determine the effects of hypothermia, hemodilution, and pump oxygenation. The experiments show that hemodilution produces increased water content in tissue and that edema is greatest in heart and gastrointestinal organs. The pump-oxygenator decreased flow to the subendocardium, whereas hemodilution increased subendocardial flow. Both hypothermia and pump oxygenation diminished flow to the outer kidney cortex, and hemodilution augmented flow to this region. Hypothermia and pump oxygenation decreased and hemodilution raised renal free-water clearance. Although none affected glomerular filtration rate, hypothermia increased filtration fraction while hemodilution diminished it. Hypothermia lessened cerebral cortical flow, an effect opposite that of hemodilution. Thus, hemodilution opposes the adverse effect of hypothermia or pump oxygenation on blood flow, oxygen delivery, or renal function. Increased water content in gastrointestinal organs and myocardium accompanies the beneficial vascular and renal effects of hemodilution.

Animals↗
PubMed1981

Cerebral dopamine, apomorphine and oral activity in the neonatal pig.

Neonatal piglets in which oral stimulation associated with feeding was reduced by intragastric tube feeding displayed an increase in stereotyped snout rubbing, licking and chewing behaviour. An investigation of a possible neurochemical basis for this behaviour was made by using sensitive radioenzymatic and microfluorimetric assays to estimate the concentrations of the catecholamines and of the dopamine metabolites homovanillic acid (HVA) and 3,4-dihydroxyphenyl-acetic acid (DOPAC) in different brain regions. These observations revealed that the increased non-nutritive oral activity of such piglets did not appear to be caused by an increased release of dopamine in the brain, since it was not associated with increases in the concentrations of the acidic metabolites of dopamine in either the caudate nucleus, the putamen, the nucleus accumbens, the olfactory tubercle, the hypothalamus, or the substantia nigra. The only neurochemical changes observed were small decreases in the concentration of HVA in the putamen and the nucleus accumbens. A lack of effect on catecholamine concentrations in any of the six brain regions examined suggested that the environmental manipulation caused no changes in the development of catecholamine-containing nerve endings. Subcutaneous injection of apomorphine was found to increase the non-nutritive oral activity of piglets. Apparent conditioning effects of the environment on apomorphine-induced stereotyped behaviour however, prevented any satisfactory testing of possible changes in cerebral dopamine receptor sensitivity following reduced oral stimulation.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1980

Vaginal tubal ligation.

This is a review of 121 cases of interval vaginal tubal ligations done by fimbriectomy between 1971 and 1979. The technic has proved to be effective, economical, rapid, safe, and simple, and requires only a short convalescence. There have been no subsequent pregnancies or serious postoperative febrile complications.

Adult↗
PubMed1980

The effects of alimentary infusions of glucose, amino acids, or neutral fat on meal size in hungry pigs.

1. Young growing pigs trained to press a panel in order to obtain delivery of small quantities of food were adapted to eating all their food during one readily measured meal per day. 2. Twenty-nine pigs were surgically fitted with an exteriorized cannula connected to either (a) the stomach or (b) the duodenum. 3. Two pigs were each fitted with two cannulae in the duodenum which were exteriorized and connected outside the body. Food was then shunted so as to pass along outside the body from the pyloric region of the duodenum to the lower part of the duodenum via the tube connecting the exteriorized cannulae. 4. While feeding, the pigs were given 250 ml. infusions of solutions of (1) 0.9% saline or (2) 15% glucose into either the stomach or the duodenum. Similar volumes of amino acids or 15% neutral fat were infused into the duodenum. 5. The infusions lasted about 3 min and were started 2-3 min after the beginning of a meal. 6. Control meals without infusions took 30-40 min. The 15% intraduodenal glucose infusions consistently produced a suppression of eating 15-20 min after the end of the infusion. 7. Infusions of 0.9% saline, of 10% amino acid or of 15% neutral fat did not reduce significantly the intake of food or the duration of the meal. 8. It was not clear how the glucose solution was able to suppress appetite. The possible existence of a specific glucose receptor is discussed.

Amino Acids↗
PubMed1979

The relative importance of thermal, osmotic and hypovolaemic factors in the control of drinking in the pig.

1. The influence of thermogenic, osmotic or hypovolaemic stimuli on drinking has been measured in young pigs. Temperature changes in the hypothalamus and spinal cord were induced by means of implanted thermodes, while peripheral changes in skin and scrotal temperature were induced by circulating water through a coat. Osmotic stimuli were applied by I.V. injections of NaCl and hypovolaemia was induced by withdrawal of blood. 2. At an ambient temperature of 21--24 degrees C warming the hypothalamus for 10 min increased the water intake approximately 40%, while cooling the hypothalamus for a similar period reduced it by about 70%. 3. At an ambient temperature of 21--24 degrees C warming the scrotum caused the pigs to drink more than controls, and at the higher ambient temperature of 32 degrees C the effect was even greater. 4. Warming or cooling the spinal cord produced effects that were not consistent either within or between animals, thus temperature changes in this region play, at most, a minimal physiological role in the control of drinking in the pig. Warming the skin to 40 degrees C produced a slight increase in water intake, as also did cooling of the skin. 5. Drinking induced by an osmotic stimulus was proportional to the concentration of NaCl ranging from 5 to 30%. 6. Withdrawal of 500 ml. blood did not produce a statistically significant increase in water intake compared with controls.

Animals↗
PubMed1975

Effects of gastric loading on the sucking response and voluntary milk intake in neonatal piglets.

The effects of loading the stomach of piglets with 100 ml of milk after 6 hr of fasting and immediately before allowing them access to the dam were studied. Piglets gained less weight and rested more often on preloaded days. This suggests that gastric receptors exist and signal distension of the stomach. Monitoring sucking responses to a rubber teat revealed that although preloading the stomach substantially reduced voluntary milk intake during the initial 10-min. period of the test, the vigorous oral activity continued largely unabated. Isotonic saline suppressed the voluntary milk intake of the piglets for a shorter period than milk or isotonic glucose solution.

Age Factors↗