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Biomedical subjects

R D Johnson

Publications and source records attributed to R D Johnson.

At least 163 records · Page 9Linked to original sources
PubMed1985

Clinical course of cirrhosis in young adults and therapeutic potential of liver transplantation.

The lack of information on survival in young adults with cirrhosis and the increasing use of liver transplantation in this age group have led us to carry out a retrospective analysis of the clinical course and survival in 83 young adults aged between 15 and 30 years presenting to the Liver Unit between 1970 and 1983. Fifty four (65%) patients had cirrhosis at initial presentation and in the remaining 29 (35%) this developed within the study period. The overall five year survival of the group, excluding 14 cases treated by transplantation, was 70%. When considered according to aetiological groups this was 83% in those with chronic active hepatitis, 60% in those with cryptogenic cirrhosis and 37% in Wilson's disease. When considered in relation to Child's grading, only three deaths occurred in the 45 patients with well-compensated liver disease (Child's grade A and B). Of the 38 patients with Child's grade C, 20 (83%) of the 24 patients not undergoing transplantation have died, whereas eight (57%) of the 14 receiving liver grafts are alive and well.

Adolescent↗
PubMed1985

Percutaneous drainage of pyogenic liver abscesses.

This report summarizes the results of percutaneous catheter drainage in 23 cases of primary or secondary pyogenic liver abscess. The overall success rate was 76%. Only three (60%) of five cases of secondary abscess (infected hematoma or infected tumor) were cured with catheter drainage, but 11 (91%) of the last 12 primary pyogenic abscesses were drained successfully. Six patients with abscesses of less than 4 cm in diameter required catheter drainage for less than 72 hr. Although six abscesses in the series appeared septated or multiloculated, only one required more than a single catheter for curative drainage. Diagnostic and technical considerations for successful drainage of hepatic abscesses are discussed. The differential diagnosis includes echinococcal disease and hepatic amebiasis. Therapeutically, specific measures should be taken to ensure proper catheter position to prevent contamination of the subphrenic, perihepatic, and pleural spaces. Percutaneous catheter drainage should be attempted as a first choice of treatment in all pyogenic hepatic abscesses.

Diagnosis, Differential↗
PubMed1985

Genetic and environmental factors in the individual susceptibility to the development of alcoholic liver disease.

Although there is a dose-response relationship between alcohol consumption and liver damage, less than one-third of alcoholics develop alcoholic liver disease (ALD). This individual susceptibility to the development of ALD may be explained by genetic and environmental factors. Of the genetic factors, female sex is clearly a significant risk factor, HLA status is probably important but further studies are needed, abnormalities in alcohol metabolism have not been shown to be of primary pathogenic importance and the plethora of immunological disturbances reported appear to be mere epiphenomena. Of the environmental factors, no consistent evidence attests to the significance of hepatitis B viral infection in the susceptibility to developing ALD.

Alcohol Dehydrogenase↗
PubMed1985

Sympathetic denervation does not alter the density or properties of alpha-1 adrenergic receptors in rat vas deferens.

Alpha-1 adrenergic receptors in surgically denervated rat vas deferens were studied using radioligand binding assays of [125I] BE 2254 ([125I]BE) and contraction measurements. Scatchard analysis of saturation isotherms of specific [125I]BE binding showed no change in the affinity or density of binding sites 4, 7 or 14 days after denervation of rat vas deferens. The potency of norepinephrine in inhibiting specific [125I]BE binding was also unchanged 7 days after denervation of vas deferens. The potency of phenylephrine in causing contraction in vitro did not change 4, 7 or 14 days after denervation of vas deferens; however, there was a significant increase in the maximum contractile response to phenylephrine at all time points. After partial inactivation of alpha-1 adrenergic receptors in vitro with phenoxybenzamine, there was an equivalent reduction in the number of [125I]BE binding sites in the control and 14-day denervated vas deferens. The equilibrium dissociation constants calculated from contractile measurements for norepinephrine were the same in the control and denervated tissues. However, there was a 2.2-fold increase in contractile sensitivity to norepinephrine 14 days after denervation and a 3.6-fold increase in contractile sensitivity to methacholine 7 days after denervation. These results show that surgical denervation of the rat vas deferens results in an increase in contractile sensitivity to norepinephrine and methacholine and an increase in maximum contraction. However, there is no change in alpha-1 adrenergic receptor density or properties at any time after denervation. Thus, alterations in alpha-1 adrenergic receptors do not contribute to contractile supersensitivity of denervated rat vas deferens.

Animals↗
PubMed1985

Thyroid status and adrenergic receptor subtypes in the rat: comparison of receptor density and responsiveness.

The density and functional responsiveness of adrenergic receptor subtypes were determined in tissues from control, hyperthyroid and hypothyroid rats. There was a decrease in sensitivity to isoproterenol in spontaneously beating right atria, electrically driven left atria and field-stimulated vas deferens associated with hypothyroidism, with no change in maximum response. Hyperthyroidism increased the potency of isoproterenol in right atria, but not in left atria or vas deferens. The maximal response to isoproterenol was greatly reduced in hyperthyroid left atria. The potency of procaterol, a partial agonist at beta adrenergic receptors in right atria, was unaltered in hyper- or hypothyroidism, although the maximum stimulation by procaterol was increased in hyperthyroidism. Scatchard analysis of specific [125I]pindolol binding showed that beta adrenergic receptor density was greater in hyperthyroidism than in hypothyroidism in left atria, right atria, ventricles, vas deferens and cerebral cortex, although the proportions of beta-1 and beta-2 adrenergic receptor subtypes did not change. There was no change in the responsiveness of alpha-1 adrenergic receptors mediating contraction of caudal artery and vas deferens or mediating [3H]inositol phosphate accumulation in cerebral cortex in hyperthyroid or hypothyroid rats, although the maximal contraction of caudal artery was significantly reduced in hyperthyroidism. Scatchard analysis of specific [125I]BE 2254 binding showed that alpha-1 adrenergic receptor density was significantly decreased in the ventricles from hyperthyroid rats and increased in the ventricles of hypothyroid rats, but was unchanged in vas deferens, caudal artery and cerebral cortex. Alpha-2 adrenergic receptor density in cerebral cortex, determined by Scatchard analysis of specific [3H] rauwolscine binding, was not altered in hyperthyroid or hypothyroid rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Microscopic investigation of structure and function in living epithelial tissues.

In this paper we shall illustrate the utility of direct microscopic methods for studying living epithelia. Beginning with an exposition on the available strategies for visualization of unstained biological materials, the rationale that leads to the choice of differential interference-contrast optics for examination of epithelia is illustrated. Findings from toad urinary bladder, Necturus gallbladder, and rabbit cortical collecting tubule are reviewed. Emphasis on renal structures is provided with a report on work in progress on proximal tubule volume regulation and on structural examination of the isolated perfused macula densa. Conclusions are drawn with respect to the advantages and shortcomings of discussed optical methods and with respect to the choice of model epithelia.

Animals↗
PubMed1984

Abscess-fistula association: radiologic recognition and percutaneous management.

Thirty-five patients with postoperative enteric and/or biliary fistulae were diagnosed and treated by percutaneous catheter drainage. All were initially considered to have postoperative abdominal abscesses, and the enteric or biliary communications were unrecognized before radiologic intervention. In addition, at the time of initial catheter insertion, only six of the 35 abscesses were recognized as being associated with an underlying fistula. In the other 29 patients the fistulae were found either by clinical follow-up or contrast sinogram after 24-72 hr of catheter drainage. Percutaneous catheter drainage was the definitive treatment in 28 (80%) of the 35 patients. The seven failures were either from inadequate catheter positioning or inability to treat the primary cause of the fistula (e.g., radiation enteritis, perforated cancer). These data suggest that even abscesses with underlying fistulae, traditionally an indication for surgical intervention, may be successfully managed by percutaneous methods.

Abscess↗
PubMed1984

Characterization of alpha-1 adrenergic receptors linked to [3H]inositol metabolism in rat cerebral cortex.

The properties of alpha-1 adrenergic receptors in rat cerebral cortex were examined by measuring increases in [3H]inositol metabolism in brain slices. Slices of rat cerebral cortex were incubated in the presence of 0.23 microM [3H]inositol in Krebs-Ringer-bicarbonate buffer containing 10 mM lithium chloride, and the production of water-soluble [3H]inositol phosphates was monitored after extraction and anion-exchange chromatography. Norepinephrine caused a 4- to 6-fold increase in [3H]inositol metabolism in cerebral cortical slices, and this response was blocked much more potently by the alpha-1-selective antagonist prazosin than by the alpha-2-selective antagonist yohimbine. Epinephrine and norepinephrine were both full agonists and stimulated [3H]inositol metabolism to the same extent in this system. The synthetic drugs phenylephrine and methoxamine were both partial agonists at these receptors, with intrinsic activities only 56 to 58% of epinephrine and norepinephrine. A variety of imidazoline and other partial agonists caused no measurable stimulation of [3H]inositol metabolism in this preparation. The response to norepinephrine was completely blocked by alpha adrenergic receptor antagonists with the potency order prazosin greater than BE 2254 greater than indoramin = phentolamine greater than azapetine greater than piperoxan greater than yohimbine. In the absence of calcium, basal [3H]inositol metabolism was increased, but norepinephrine caused the same 5-fold stimulation as in the presence of 2.5 mM CaCl2. The potencies of both antagonists and agonists in inhibiting or activating [3H]inositol metabolism in slices of rat cerebral cortex were highly correlated with their ability to displace the alpha-1 adrenergic receptor selective radioligand [125I]BE 2254 from specific binding sites in membrane preparations of rat cerebral cortex.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenergic alpha-Antagonists↗
PubMed1984

Cutaneous innervation of the thorax and abdomen of the dog.

The anatomy of the cutaneous nerves innervating the canine thorax and abdomen was investigated by gross dissection of 38 dogs. Additionally, the cutaneous areas innervated by the thoracic and abdominal cutaneous nerves were mapped in a 2nd group of 33 barbiturate-anesthetized male dogs, using electrophysiologic techniques. The skin of the thorax was innervated by dorsal cutaneous branches, lateral cutaneous branches, and ventral cutaneous branches of the spinal nerves. The dorsal cutaneous branches were branches of the dorsal primary branches of spinal nerves C6 and T2 through T11. The lateral cutaneous branches were branches of the ventral primary branches of spinal nerves T2 through T12. The ventral cutaneous branches were branches of the ventral primary branches of spinal nerves T2 through T10. The skin of the abdomen was innervated by dorsal and lateral cutaneous branches of spinal nerves T12 through L3 (and occasionally L4). The cutaneous areas of the dorsal cutaneous branches occupied the dorsal half of the scapular and thoracic regions and the dorsal 2/5 of the abdominal region. The cutaneous areas of the lateral cutaneous branches covered the major portion of the ventral half of the thorax and the ventral 3/5 of the abdomen. The cutaneous areas of the ventral cutaneous branches occupied the axilla and the ventral part of the thoracic wall.

Abdomen↗
PubMed1984

Evaluation of postoperative osteomyelitis of the sternum using tomography and computerized tomography.

Thirty-five patients were evaluated for possible postoperative sternal osteomyelitis by tomography. Frank bone destruction and severe demineralization were the only radiologic signs that helped to distinguish patients with sternal osteomyelitis from those with infections limited to soft tissues. We report a patient in whom sternal osteomyelitis was shown by computerized tomography (CT). This observation suggests that CT may provide added information, especially if the sternum is severely demineralized.

Female↗
PubMed1984

Selected minerals in foods surveys, 1974 to 1981/82.

The levels of 11 essential minerals in food commodity groups and total diets of adult males, infants, and toddlers were summarized from the Selected Minerals in Foods Survey, Fiscal Years (FY) 1974 through mid-1982, of the Food and Drug Administration (FDA) to evaluate the sources and adequacy of those minerals in the diets. The three diets were adequate in calcium, phosphorus, magnesium, potassium, manganese, and selenium; low in copper; and elevated in sodium and iodine. Iron was adequate in adult male but not in infant or toddler diets, and zinc was adequate in infant but somewhat low in adult male and toddler diets. Dairy products; meat, fish, and poultry; grain and cereal products; and fruits and vegetables were the major sources of the 11 minerals. Some statistically significant differences in mineral levels were found among years for total diets and food commodity groups. Regression analysis indicated several linear trends in the mineral content of food commodity groups but no linear trends in the mineral levels of total diets. FDA continues to monitor the levels of minerals in food and diets through the revised Total Diet Study program, which began in mid-FY82.

Adult↗
PubMed1983

Model studies for brain dialysis.

A dialysis cannula suitable for perfusing deep brain structures in animals is described and characterized in a series of model experiments. The effects of flow rate, concentration, variations in cannula construction, barriers to diffusion and pumping technique on the recovery of tryptophan from aqueous solutions at 37 degrees C were examined. The 200 micron diameter dialysis cannula gave good recoveries which varied from about 8% at 6 microliter/min to almost 90% at 0.15 microliter/min. Prepurification of the extracellular fluid by dialysis allows the sample loop of a high performance liquid chromatograph to be incorporated in the outflow line of the cannula for direct injection of dialysates.

Animals↗
PubMed1983

Sensory nerve conduction velocities in forelimb of ponies.

Normal nerve conduction velocity values in 10 ponies were determined for sensory nerve fibers in the median and ulnar nerves. A percutaneous signal-averaging technique was developed and used. Medial and lateral palmar digital nerves on the abaxial surface of the proximal sesamoid bones were used as the sites for percutaneous stimulation, whereas recording sites included the medial and lateral palmar nerves just distal to the carpus and the median and ulnar nerves in the middle of the radius. Sensory nerve conduction velocities can be evaluated simply and clinically in the limbs of horses, using percutaneous signal-averaging techniques.

Action Potentials↗