Biomedical subjects

W W Mullins

Publications and source records attributed to W W Mullins.

3 recordsLinked to original sources

PubMed1987

Soluble immune complexes in lupus mice: clearance from blood and estimation of formation rates.

Elevated levels of circulating immune complexes (IC) occur in patients with systemic lupus erythematosus (SLE) and in several strains of mice that spontaneously develop a lupus-like illness. An increase in circulating IC might occur as a result of increased IC formation or decreased IC clearance. Previous work with one murine lupus strain, NZB/W, demonstrated normal clearance of soluble IC. We studied the in vivo behavior of stable model IgG IC in two murine lupus strains. MRL/l and BXSB, and in two normal strains, C3H/HeN and BALB/c. IC were injected intravenously, and blood radioactivity was measured over 3 hr. A clearance curve was derived for each mouse using the Marquardt-Levenberg curve-fitting method. A formula is derived which predicts the formation rate of IC in each animal from the blood level of IC and the clearance curve parameters. All mice exhibited biphasic exponential clearance of IC over 3 hr. Clearance of IC was significantly slower in MRL/l mice than in normal strains (P less than 0.02), and clearance in BXSB mice was significantly faster than in normals (P less than 0.02). However, the derived formula suggests that the observed differences in IC clearance have only a small effect on the blood levels of IC in the mice studied, and therefore suggests that the major factor which accounts for increased blood levels of IC in lupus mice is an increase in the IC formation rate.

Albumins↗

PubMed1978

Spatial summation effects on two-component grating thresholds.

Some experimental studies of subthreshold summation between sinusoidal grating components have been interpreted as showing very narrow channel bandwidths in human visions. This paper discusses an alternative interpretation of these experiments based on consideration of probability-summation effects among spatially distributed detectors. We conclude that frequency-selective channels must still be hypothesized in order to fit the data, but the channel bandwidth may be much wider than earlier interpretations suggest.

Humans↗

PubMed1978

Convexity theorem for subthreshold stimuli in linear models of visual contrast detection.

Under the general assumption that visual contrast detection occurs by a parallel array of linear detectors, either without probability summation or with probability summation of a commonly assumed type, it is shown that the set of functions representing subthreshold stimuli must be convex. Thus, for example, a planar plot of the threshold locus using multiples of any two functions as axes, must be convex (cannot bulge inward). If experimental evidence to the contrary were discovered, it would rule out detection by parallel linear detectors of the above type. One possible kind of such evidence would be an inward cusp of the threshold locus corresponding to one of a special class of stimuli to which the visual system might be specifically sensitive.

Humans↗