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Biomedical subjects

L Samuelson

Publications and source records attributed to L Samuelson.

At least 19 recordsLinked to original sources
PubMed1999

How costly is the honest signaling of need?

ESS models of biological signaling have shown that costly signals can provide honest information. In the context of parent-offspring conflict over the allocation of resources by parents to their young, the theory explains costly offspring solicitation behavior as an accurate signal of offspring need to parents who cannot assess offspring condition directly. In this paper, we provide a simple but general characterization of the honest signaling of need in models of parent-offspring conflict: the offspring's signaling cost is proportional to the parent's fitness loss from satisfying the offspring's resource requirement. The factor of proportionality is given by a measure of the extent of parent-offspring conflict that depends only on coefficients of relatedness. These results hold for interbrood conflict with uniparental investment even if the relationship between offspring condition and resource requirement is not monotonic, and extend to cases of biparental care, uncertainty concerning the parent's condition, and intra-brood conflict. Copyright 1999 Academic Press.

Journal Article↗
PubMed1998

Optical studies of individual InAs quantum dots in GaAs: few-particle effects

Optical emission from individual strained indium arsenide (InAs) islands buried in gallium arsenide (GaAs) was studied. At low excitation power density, the spectra from these quantum dots consist of a single line. At higher excitation power density, additional emission lines appeared at both higher and lower energies, separated from the main line by about 1 millielectron volt. At even higher excitation power density, this set of lines was replaced by a broad emission peaking below the original line. The splittings were an order of magnitude smaller than the lowest single-electron or single-hole excited state energies, indicating that the fine structure results from few-particle interactions in the dot. Calculations of few-particle effects give splittings of the observed magnitude.

Journal Article↗
PubMed1998

Targeted disruption of the mouse villin gene does not impair the morphogenesis of microvilli.

The small intestine is functionally dependent on the presence of the brush border, a tightly packed array of microvilli that forms the amplified apical surface of absorptive cells. In the core of each microvillus, actin filaments are bundled by two proteins, villin and fimbrin. Previous in vitro studies using antisense approaches indicated that villin plays an important role in the morphogenesis of microvilli. To examine the in vivo consequences of villin deficiency, we disrupted the mouse villin gene by targeted recombination in mouse embryonic stem cells. A beta-galactosidase cDNA was also introduced into the villin locus by the targeting event. Homozygous villin-deficient mice are viable, fertile, and display no gross abnormalities. Intact microvilli are present in the small intestine, colon, kidney proximal tubules, and liver bile canaliculi. Although subtle ultrastructural abnormalities can be detected in the actin cores of small intestinal microvilli, localization of sucrase isomaltase, brush border myosin I, and zonula occludens I to the microvillar surface of the small intestine is normal. Thus, in vivo, villin plays a minor or redundant role in the generation of microvilli in multiple absorptive tissues.

Animals↗
PubMed1989

Problems with tricyclic antidepressant use in patients with panic disorder or agoraphobia: results of a naturalistic follow-up study.

The authors followed up 107 patients with panic disorder or agoraphobia with panic attacks who had been placed on a regimen of tricyclic antidepressant treatment 1 to 4 years earlier. Sixty-three percent reported at least moderate improvement during treatment; however, side effects were often difficult to tolerate, and 35% discontinued tricyclic treatment on this account. Overstimulation, which occurred in 20%, was the most frequent reason for early termination, and weight gain, which occurred in 34%, was the most common reason for stopping the drug later on. Seizures occurred in 2 patients. Even though they were encouraged to discontinue drug use, most of the patients who had responded were still taking their drugs at follow-up. More than half of those who had responded before stopping drug treatment subsequently relapsed. The findings highlight problems with safety, side effects, and patient acceptance resulting from the use of tricyclic antidepressants in patients with anxiety disorders.

Adult↗