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Biomedical subjects

K Anderson

Publications and source records attributed to K Anderson.

At least 397 records · Page 22Linked to original sources
PubMed1983

Quality assurance in radiographic imaging included in the film marking procedure.

Quality assurance for the radiographic processing can only be obtained by the aid of a continuous densitometric control. A method is described which uses a densitometric step wedge included in the marker equipment. It gives a constant radiation dose to the marking area. The step wedge is exposed simultaneously with the film marking. Disturbances in the radiographic procedure can thus immediately be detected.

Methods↗
PubMed1983

Effects of obesity on estradiol metabolism: decreased formation of nonuterotropic metabolites.

Obesity is associated with an increased incidence of reproductive dysfunction and estrogen-linked diseases. In the present study, we have examined the principal oxidative biotransformations of estradiol in 13 obese premenopausal females and 10 obese males compared to those in 9 premenopausal female and 15 male controls. These studies were carried out using a recently devised, sensitive radiometric method which permits the assessment of the total in vivo oxidative metabolism of estradiol at specific sites (i.e. 17 alpha, 16 alpha, or C-2) on the steroid molecule. Our results indicate that obesity (greater than 60% above ideal body weight) is associated with significant decreases in hydroxylation at C-2 in both sexes (P less than 0.001 for females and P less than 0.02 for males) and in oxidation at 17 alpha in premenopausal females (P less than 0.05) compared to that in age-matched, normal weight controls. Analysis of the plasma 3H2O specific activity curves suggested a slight decrease in the rate of 17-oxidation in obese subjects. The extent of hydroxylation at 16 alpha was not significantly affected by obesity. These metabolic alterations documented in obesity could result in a relative hyperestrogenic state, since, unlike the other estrogen metabolites, the 2-hydroxyestrogen compounds display relatively little peripheral estrogenic activity. This metabolic alteration on a prolonged basis might be contributory to the prevalence of certain hormonally related diseases in obese individuals.

Adult↗
PubMed1982

Regression analysis of cytopathological data.

Epithelial cells from the human body are frequently labelled according to one of several ordered levels of abnormality, ranging from normal to malignant. The label of the most abnormal cell in a specimen determines the score for the specimen. This paper presents a model for the regression of specimen scores against continuous and discrete variables, as in host exposure to carcinogens. Application to data and tests for adequacy of model fit are illustrated using sputum specimens obtained from a cohort of former asbestos workers.

Adult↗
PubMed1981

Treatment of stage D prostatic carcinoma with megestrol acetate.

Nine previously untreated patients with stage D prostatic carcinoma received megestrol acetate 40 mg orally three times daily. Responses included five partial regressions, two stabilizations, and two progressions. Duration of response ranged from 3+ to 33+ months, with a mean of 11.7 months and a median of 12 months. Three of five patients who had failed prior hormonal therapy remained objectively stable while receiving megestrol acetate. No gastrointestinal toxicity, gynecomastia, fluid retention, or thromboembolic complications were observed during treatment. Weight gain of 5 to 51 pounds occurred in seven of 14 patients.

Aged↗
PubMed1981

Fast stopped-flow microcalorimeter.

A fast stopped-flow microcalorimeter using a thermistor and an a.c. bridge is described. Time resolution, limited by the response of the thermistor, is 3 ms for t 1/2 while sensitivity is 100 mu degree C in this bandpass. A reaction requires 0.3 ml of each reactant. The microcalorimeter is adiabatic to within 2% for 2 s and mixing may be repeated every 5 min. Computer finite element simulation techniques (FEST) are used to correct for the thermistor response time and heat losses. Results of tests with reactions of NaOH and HCl, NaHCO3, and HCl, and glyclyglycine and CO2 agree with published kinetic and thermodynamic values to within an experimental error of less than 2%.

Bicarbonates↗
PubMed1981

Synthesis and pharmacological evaluation of sulfonium analogues of dopamine: nonclassical dopamine agonists.

In order to test whether the nitrogen/ammonium moiety in the dopamine molecule is required for dopaminergic activity, we have synthesized two sulfonium analogues of dopamine and tested them for biological activity in an in vivo and in an in vitro system. These analogues have provided a means of investigating (1) the ability of the sulfonium function to serve as a bioisostere for the dopamine amino group and (2) whether charged molecules have the ability to bind to dopamine receptors. Both sulfonium analogues, 1 and 2, as well as dopamine, when injected directly into the striatum of rats, previously lesioned unilaterally with 6-hydroxydopamine (6-OHDA), produced circling behavior. The potency of the sulfonium analogues was approximately one-tenth that of dopamine. The effects of all three compounds on circling were inhibited by the dopamine antagonist haloperidol. In addition, both sulfonium analogues inhibited the high affinity binding of radiolabeled dopamine to a crude membrane fraction prepared from the striatum. This study suggests that the nitrogen atom found in th dopamine molecule is not essential for dopaminergic activity, since the nitrogen can be replaced by a sulfonium functional group for this activity.

Animals↗
PubMed1980

A light scattering study on the ion permeabilities of dark-adapted bovine rod outer segment disk membranes.

The ion permeability properties of dark adapted bovine rod outer segment disk membranes were studied using light scattering to monitor osmotic responses of disks to various salts and ionophores. A preparation procedure is presented which provides very fresh rod outer segment material with mostly intact stacked disks, but with perforated plasma membrane. It is shown that in this preparation the disks (or rod sacs) are the only osmotically responding compartments and that these responses can be readily monitored by means of light-scattering techniques. The disk membrane is found under the conditions tested, to possess no measurable permeability to cations Na+, Ca2+, Mg2+ nor the the anions Cl-, Br-, NO3-, SO4(2-), H2PO4- and HPO4(2-). There is a considerable K+ permeability, which can be completely abolished by millimolar amounts of divalent cations. The proton permeability of the disk membrane is found to depend dramatically upon the preparation procedure and duration. The fresher the material used the lower is the proton permeability measured. In our freshest preparations, even after freeze-thawing in liquid nitrogen, the disks exhibit an H+ permeability which is so low that it cannot be measured with the techniques used in this study. Even in mitochondrial or chloroplast membmranes, in which proton gradients and therefore a low proton conductance play an essential role, such low proton permeabilities have not been found. This would suggest that proton gradients across the disk membrane could play an important role in the physiological function of the photoreceptor cell. In summary it can be said that the disk membrane, apparently more than any other natural membrane system studied so far, is capable of retaining ion gradients for extended periods of time.

Animals↗