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Biomedical subjects

V E Johnson

Publications and source records attributed to V E Johnson.

17 recordsLinked to original sources
PubMed1999

Twelve years later: adjustment in families who adopted children with developmental disabilities.

In most studies positive outcomes for families who have adopted children with developmental disabilities have been described. In this previous research, however, investigators have examined primarily short-term adjustment. In contrast, in the current longitudinal investigation 9 years after an initial interview, we assessed the adjustment and functioning of families who have adopted children with developmental disabilities. Results indicate that nearly 12 years after their adoptions, families remaining in the study reported generally positive outcomes and good adjustment to their adopted children. Whereas there were changes in these families, especially as the children approached adolescence and early adulthood, these changes were perceived as potential sources of reward as well as sources of stress.

Adaptation, Psychological↗
PubMed1997

Fully Bayesian estimation of Gibbs hyperparameters for emission computed tomography data.

In recent years, many investigators have proposed Gibbs prior models to regularize images reconstructed from emission computed tomography data. Unfortunately, hyperparameters used to specify Gibbs priors can greatly influence the degree of regularity imposed by such priors and, as a result, numerous procedures have been proposed to estimate hyperparameter values from observed image data. Many of these procedures attempt to maximize the joint posterior distribution on the image scene. To implement these methods, approximations to the joint posterior densities are required, because the dependence of the Gibbs partition function on the hyperparameter values is unknown. In this paper, we use recent results in Markov chain Monte Carlo (MCMC) sampling to estimate the relative values of Gibbs partition functions and using these values, sample from joint posterior distributions on image scenes. This allows for a fully Bayesian procedure which does not fix the hyperparameters at some estimated or specified value, but enables uncertainty about these values to be propagated through to the estimated intensities. We utilize realizations from the posterior distribution for determining credible regions for the intensity of the emission source. We consider two different Markov random field (MRF) models-the power model and a line-site model. As applications we estimate the posterior distribution of source intensities from computer simulated data as well as data collected from a physical single photon emission computed tomography (SPECT) phantom.

Algorithms↗
PubMed1985

Frusemide-sensitive sodium and potassium transport by human leucocytes.

Frusemide-sensitive sodium and potassium transport by normal human leucocytes has been studied in vitro by both isotopic and net flux techniques. In physiological media the leucocyte exhibits a frusemide-sensitive influx of sodium and potassium of equal magnitude compatible with a 1:1 co-transport system. Cells exposed to zero external sodium and potassium (osmolality maintained with choline) demonstrated a frusemide-sensitive sodium and potassium efflux. Frusemide-sensitive potassium influx was dependent on the presence of external sodium but frusemide-sensitive sodium influx persisted unchanged in the absence of external potassium. Frusemide-sensitive potassium influx was dependent on external chloride but frusemide-sensitive sodium influx was chloride-independent. These last two observations make it likely that the frusemide-sensitive pathway is capable of operating in modes other than sodium-potassium co-transport.

Biological Transport, Active↗
PubMed1985

Effect of the calcium antagonist verapamil on human leucocyte sodium transport in vitro.

Sodium efflux rate constants and intracellular sodium were measured in leucocytes from healthy volunteers in the presence and absence of the calcium antagonist verapamil hydrochloride. Verapamil stimulated sodium pump activity and this effect was dependent on the presence of external calcium. Verapamil has been reported to reverse the abnormality of sodium transport seen in leucocytes from patients with essential hypertension and the present study demonstrates that sodium pump activity in leucocytes from control subjects is also stimulated by exposure to verapamil in vitro. This direct cellular effect appears to be due to the calcium antagonist properties of the drug.

Biological Transport, Active↗
PubMed1985

The effect of dietary sodium restriction on leucocyte sodium transport in normotensive subjects and in patients with essential hypertension.

Dietary sodium restriction (10 mmol Na/day) for a period of 2 weeks did not result in any change in the blood pressure of 12 healthy young adults (mean age 21). There was also no change in their leucocyte sodium transport investigated immediately before the diet and on the last day. Sodium restriction (10 mmol Na/day) in 12 middle-aged hypertensive subjects (mean age 56) for the same period of time caused a significant fall in both systolic and diastolic blood pressure. The leucocyte total sodium efflux rate constant was initially low, but after the diet significantly increased towards the control value. The results are compatible with the theory that a circulating sodium transport inhibitor is present in patients with essential hypertension, and is related to salt intake.

Adolescent↗
PubMed1984

Sodium transport by leucocytes and erythrocytes in hypertensive subjects and their normotensive relatives.

Intracellular sodium content and ouabain-sensitive sodium efflux rate constant were measured in leucocytes and erythrocytes from subjects with untreated essential hypertension and also in normotensive subjects with and without a family history of hypertension. Leucocytes from hypertensives were again shown to have a higher intracellular sodium content and lower ouabain-sensitive sodium efflux rate constant than normotensive controls but there were no differences between those normotensive subjects with and those without a family history of hypertension. No differences in erythrocyte sodium content or efflux rate constant were seen between any of the three groups.

Adult↗
PubMed1981

The effects of alterations in the external sodium concentration on human leucocyte sodium and potassium transport in vitro.

Human leucocytes incubated in tissue culture fluid of low-sodium concentration (2 mM; iso-osmolarity maintained with choline chloride) reached a new equilibrium within 1 hour and lost approximately 25% of intracellular potassium and 70% of intracellular sodium. The rate constant for ouabain-sensitive sodium efflux fell by more than 50% and the ouabain-insensitive rate constant increased nearly threefold in the low-sodium medium. Total sodium efflux fell in proportion to internal sodium whereas ouabain-insensitive sodium efflux remained unchanged. A reduction in external sodium from 140 to 2 mM was associated with a 75% fall in sodium influx. In the low-sodium medium ouabain-sensitive potassium influx exceeded ouabain-sensitive sodium efflux and no ouabain-sensitive potassium efflux could be demonstrated. Ouabain-insensitive potassium influx and that portion of potassium efflux which is dependent on external potassium fell in parallel in low-sodium cells, suggesting reduced activity of a ouabain-insensitive K:K exchange system.

Biological Transport↗
PubMed1981

Sex and the aging process.

The elderly tend to be victims of "age-ism," a false concept that discourages consideration of sexual activity in old age. Geriatric sexual activity is a vital issue, however, and proper management of attendant problems has great bearing upon mental and physical health. The inevitable processes of aging necessitate adjustments, but these can be accomplished satisfactorily by enlightened understanding between sexual partners.

Aged↗
PubMed1980

Zinc transport in normal human leucocytes: dependence upon media composition.

1. The transport of zinc has been studied in normal human leucocytes incubated in both a tissue culture medium and Krebs buffer. 2. 65Zn influx is characterized by an initial rapid phase followed by a slower influx. 65Zn influx is directly dependent upon the extracellular zinc concentration. 3. Net zinc influx could only be demonstrated in Krebs buffer at zinc concentrations in excess of 4.3 mumol/l and in tissue culture fluid at zinc concentrations in excess of 43.1 mumol/l. 4. A 65Zn efflux rate constant of approximately 1.0 per h was observed in both 4.3 and 15.4 mumol of zinc/l of Krebs buffer or tissue culture fluid. 5. In a zero external zinc Krebs buffer the 65Zn efflux rate constant fell to 0.57 per h and was accompanied by a small net zinc efflux.

Biological Transport↗
PubMed1979

In vivo evaluation of an effervescent intravaginal contraceptive insert by simulated coital activity.

Sixteen women ages 20 to 41 participated in a project to evaluate the in vivo intravaginal spermicidal effectiveness of nonoxynol-9 foaming suppositories. Testing of each subject was done at 18 different time intervals ranging from 5 seconds to 6 hours following insertion of the vaginal contraceptive. Simulated coitus using a latex dildo was incorporated in the test design to simulate dispersal of the spermicide that occurs during coitus. Semen specimens meeting uniform criteria for sperm count, motility, morphology, and volume were injected intravaginally; three vaginal aspirates were then immediately obtained to evaluate sperm motility microscopically. Maximal spermicidal effectiveness was found between 5 minutes and 1 hour after insertion of the vaginal contraceptive.

Adult↗
PubMed1976

Principles of the new sex therapy.

The authors review the development of their rapid treatment dual-sex therapy for sexual dysfunction. The basic tenets of the new sex therapy include 1) sound knowledge of physiology, endocrinology, and metabolic function, 2) institution of psychotherapy only when organic factors have been identified or ruled out, 3) treatment of the couple as a unit by dual-sex therapy teams, 4) a short-term intensive program, and 5) education in techniques of verbal and nonverbal communication. Since its inception in 1958, the new therapy has been adopted, modified, and examined by clinicians and researchers all over the world. The authors suggest that professionals interested in effective treatment for sexual dysfunction should improve techniques, train personnel, and encourage sound research.

Communication↗