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Biomedical subjects

R Dean

Publications and source records attributed to R Dean.

At least 19 recordsLinked to original sources
PubMed1992

Bilateral atrial appendectomy abolishes increased plasma atrial natriuretic peptide release and blunts sodium and water excretion during volume loading in conscious dogs.

The atrial appendages contain most of the atrial natriuretic factor (ANF) in the mammalian heart, and atrial appendage mechanical function predicts ANF secretion during volume loading. To demonstrate the crucial role of the atrial appendages in ANF release, we first measured hemodynamics and changes in plasma ANF after injection of 1,000 ml i.v. normal saline in conscious dogs and again after bilateral atrial appendectomy; we next measured changes in renal function using infusions of atriopeptin 24 to achieve plasma levels corresponding to levels achieved during volume loading; and we lastly measured renal function during acute volume expansion and also after atrial appendectomy. Plasma ANF increased from 65 +/- 11 to 246 +/- 54 pg/ml after volume loading but did not increase after atrial appendectomy. Atrial appendectomy did not alter the tachycardia or hemodynamic effects of volume loading. Infusion of 10 ng/kg/min atriopeptin 24 increased plasma ANF from 50 +/- 9 to 234 +/- 54 pg/ml, increased urine output 34 +/- 10%, and increased sodium excretion 62 +/- 10% in dogs with intact atrial appendages. Renal function was compared in dogs before atrial appendectomy: 20, 40, and 60 minutes after volume loading, urine flow rate increased by 5.9 +/- 0.5, 6.9 +/- 0.4, and 4.4 +/- 0.8 ml/min, while sodium excretion increased by 717 +/- 60, 839 +/- 84, and 582 +/- 57 mueq/min. After atrial appendectomy urine flow rate increased 2.1 +/- 0.7, 2.7 +/- 0.7, and 2.0 +/- 0.6 ml/min, and sodium excretion increased only by 327 +/- 110, 324 +/- 77, and 340 +/- 92 mueq/min (p less than 0.01) during volume loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

T.A.C.

Explore the source record for details and available documents.

Anesthesia, Local↗
PubMed1991

Effect of dietary manipulation on c-myc RNA expression in adipose tissue, muscle and liver of broiler chickens.

The effects of dietary restriction on the relative steady state levels of cellular myc (c-myc) mRNA in abdominal adipose tissue, breast muscle and liver of chickens were determined. Fasting was found to increase c-myc RNA expression in adipose tissue (p less than 0.01). This increase returned to normal levels after refeeding. Muscle and liver in fasted birds did not show changes in c-myc that differed from controls. Serum concentrations of glucose, triglyceride (TG), free fatty acids (FFA) and insulin-like growth factor (IGF-I) were compared to levels of c-myc found in control birds. In adipose tissue, c-myc levels were negatively correlated with serum glucose, TG and IGF-I, while in muscle a positive correlation with serum glucose and TG was found. Data suggest that c-myc is involved in the metabolic changes occurring in fat cells under fasting conditions.

Adipose Tissue↗
PubMed1991

Isolation of DNA from blood.

A rapid, economical method of DNA isolation from blood was developed that yields DNA suitable for Southern analysis and polymerase chain reactions without organic solvent extractions. Bovine DNA was prepared from peripheral leukocytes and nuclei using pronase E digestion and ethanol precipitation. This isolation method readily adapts to multiple samples. The DNA is characterized by high yield, solubility, lack of protein contamination, and ease of restriction endonuclease digestion.

Animals↗
PubMed1991

Prediction of free phenytoin levels based on [total phenytoin]/[albumin] ratios. Potential errors with hypoalbuminemia.

Therapeutic monitoring of the pharmacologically active (free drug) fraction of protein-bound medications (e.g., phenytoin) represents a major diagnostic challenge in clinical and laboratory medicine. While free drug levels may be beneficial in many clinical situations, current methods for predicting free phenytoin concentrations are unreliable and not recommended for general use. The authors have demonstrated a linear relationship (r2 = 0.98) between serum levels of total and bound phenytoin in 56 patients with seizure disorders. No significant correlations were observed when total phenytoin and albumin levels were compared independently to measured concentrations of free phenytoin or percent free phenytoin. A good correlation (r2 = 0.89) existed between free phenytoin levels and [total phenytoin]/[albumin] ratios in patients with normal or elevated albumin levels, but significantly weaker correlations were found in patients with hypoalbuminemia. Thus, [total phenytoin]/[albumin] ratios may have clinical value in predicting free phenytoin levels in uncomplicated patients without hypoalbuminemia.

Humans↗
PubMed1991

Displacement of phenytoin from serum protein carriers by antibiotics: studies with ceftriaxone, nafcillin, and sulfamethoxazole.

Increased concentrations of free phenytoin in serum, attributable to the displacement of this anticonvulsant by other drugs, e.g., valproic acid and salicylic acid, have been reported. We observed in vitro and in vivo displacement of phenytoin by the antibiotics ceftriaxone, nafcillin, and sulfamethoxazole. In vitro studies demonstrated statistically significant (P less than 0.05) increases in free phenytoin after the addition of specific antibiotics to patients' sera and to phenytoin-supplemented sera from controls. Concentrations of free phenytoin in vivo, predicted by an equation we have found to be accurate for albumin concentrations greater than or equal to 32 g/L, were consistently underestimated in patients receiving concomitant therapy with the antibiotics studied. The concentrations of free phenytoin decreased towards the predicted values when the antibiotic therapy was discontinued. We conclude that ceftriaxone, nafcillin, and sulfamethoxazole can displace phenytoin from the usual protein carriers found in serum, in vitro and in vivo.

Carrier Proteins↗
PubMed1990

Post-operative urinary tract infection and wound infection in women undergoing caesarean section: a comparison of two study periods in 1985 and 1987.

In 1985 and 1987 women undergoing Caesarean section were studied for the development of post-catheterization bacteriuria, urinary tract infection and wound infection. In 1985, 34% developed bacteriuria compared to 25% in 1987. Post-catheterization bacteriuria within two days was reduced by improved catheterization techniques. Late urinary tract infection after 5 days occurred in 2% of women in 1985 and 6% in 1987. The commonest bacteria were Escherichia coli and enterococci. Post-catheterization bacteriuria was only confirmed in a second urine specimen in 53%. The incidence of wound infection was 20% in 1985 and 15.8% in 1987 but bacterial pathogens were only isolated from 12.5% and 5.1% respectively. Staphylococcus aureus was isolated in 60% of infected women. Antimicrobial usage was high in this group of women at 41% in 1985 and 27% in 1987. A significant reduction of usage from 37% to 16% was seen in bacteriologically confirmed infections where the laboratory reports were only issued after examination of a second specimen. However most symptomatic women received treatment. The incidence of post-operative infective complications is high in women having Caesarean section. Careful urethral catheterization techniques are necessary to prevent bacteriuria.

Adolescent↗
PubMed1990

Foci of increased T2 signal intensity in MR images of healthy elderly subjects. A follow-up study.

An 18-month follow-up study was conducted on 26 healthy elderly subjects with and without foci of increased T2 signal intensity on MR imaging. The subjects did not differ with respect to health status or cognitive performance as measured by the Cognitive Subscale of the Cambridge Mental Disorders of the Elderly Examination and the Mini Mental State Examination at follow-up. There was a significant decline in performance on the Digit Symbol Substitution Test in subjects who had evidence of T2 foci compared to the performance of subjects without T2 foci. This may indicate that the presence of T2 foci is correlated with subtle difficulties in learning and memory.

Aged↗
PubMed1990

Dynamics of atrial peptide secretion in the coronary circulation of the conscious dog.

The secretion of atrial natriuretic peptide by the heart is not simply the arterial-coronary sinus concentration difference times coronary blood flow, because only a small fraction of total coronary blood flow passes through the atria. We measured coronary sinus and arterial plasma atrial natriuretic factor (ANF) concentrations and blood flow to each part of the heart using the radioactive microsphere technique. Before acute volume expansion, the arterial-coronary sinus ANF difference was 305 +/- 23 pg/ml and rose to 1,009 +/- 220 pg/ml during volume expansion, whereas total coronary blood flow rose from 167 to 465 ml/min. Atrial blood flow rose from 2.9% to 4.6% of total coronary blood flow during volume expansion. ANF secretion rate increased from 51 to 469 ng/min. When divided by atrial weight, ANF secretion rate increased from 4.0 +/- 0.3 to 56 +/- 12 ng/min/g atrial tissue-in other words, from 0.3% to 3.7% of tissue ANF content each minute. Dividing by atrial blood flow indicated that the concentration of ANF leaving atrial tissue was 10,000 to 29,651 pg/ml, and the additional secretion of ANF was determined by the increase in coronary blood flow. Therefore, at least two mechanisms are responsible for altering coronary sinus ANF and circulating ANF: the release rate from atrial myocytes and the washout via changes in atrial blood flow.

Animals↗
PubMed1990

G-protein-linked serotonin receptors in mouse kidney exhibit identical properties to 5-HT1b receptors in brain.

The serotonin 1b (5-HT1b) receptor is thought to mediate both pre- and postsynaptic actions of serotonin. Until recently 5-HT1b sites were thought to be present only in rodent brain. We now report the presence of high-affinity [125I]iodocyanopindolol [( 125I] ICYP) binding sites in the mouse renal medulla with properties identical to those of brain 5-HT1b receptors. In vitro receptor autoradiography demonstrates that [125I]ICYP binding is highly localized to the outer stripe of the renal medulla. Association and dissociation kinetics, saturation analysis and competition displacement analyses indicate that renal medullary [125I]ICYP binding sites exhibit identical properties with brain 5-HT1b receptors. Incubation of renal medullary or brain membranes with guanylimidodiphosphate results in a decreased affinity of 5-HT1b sites for 5-HT and [125I]ICYP; this can be reversed by the addition of a purified mixture of G proteins (Gi/Go). Treatment of brain or kidney membranes with N-ethylmaleimide results in a decrease in 5-HT1b binding which can also be restored by reconstitution with purified G proteins. Adenylyl cyclase from renal medullary homogenates or minces can be stimulated more than 3-fold by forskolin and attenuated by 5-HT. These results indicate that mouse kidney contains high-affinity 5-HT1b receptors with identical properties to those found in brain. These are localized in the outer stripe of the renal medulla and are functionally coupled to adenylyl cyclase inhibitor (Gi) G-proteins.

Alkylation↗
PubMed1989

Metoclopramide promotes enteral feeding in preterm infants with feeding intolerance.

We hypothesized that the feeding difficulties experienced by premature infants are related to immature peristaltic activity and that a bowel accelerant might promote feeding in prematures. We administered metoclopramide (Meto) to 14 infants admitted to the Intensive Care Nursery at The University of Chicago between January 1, 1984, and January 1, 1987. Each infant had failed enteral feeding on at least two separate occasions. At the time of initiation of Meto, the group of infants tolerated only 11.7 +/- (SEM) 3.6 cm3/kg/day enterally. Feeding tolerance improved steadily after Meto was initiated, and by 29 days the infants tolerated 134 +/- 12.6 cm3/kg/day enterally. The average slope of the post-Meto feeding regression lines was +4.21 +/- 0.94 cm3/kg/day/day, significantly greater than -0.67 +/- 0.59 cm3/kg/day/day pre-Meto. The percentage of feedings followed by significant gastric residual volumes was 33.1 +/- 4.6% pre-Meto, compared to 6.9 +/- 2.5% post-Meto. No child receiving Meto developed any extrapyramidal neurologic symptoms, worsening of hepatic function, or necrotizing enterocolitis. Meto may have a role in the treatment of premature infants with enteral feeding intolerance.

Enteral Nutrition↗
PubMed1978

The accuracy of antimicrobial disk sensitivity testing in urinary tract infections.

Fifty bacterial strains shown resistant to ampicillin, cephalothin or tetracycline by Kirby-Bauer disk diffusion susceptibility testing were isolated from patients with urinary infections. Inhibitory activity in urine of volunteers given these antimicrobial agents and tube dilution sensitivity testing indicated that agar disk diffusion gradients do not provide sufficiently high antimicrobial concentrations to predict accurately clinical efficacy.

Ampicillin↗