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Biomedical subjects

F M Johnson

Publications and source records attributed to F M Johnson.

68 records · Page 4Linked to original sources
PubMed1971

Esterase polymorphism in the butterfly Hemiargus isola: stability in a variable environment.

A dimeric esterase of a lycaenid butterfly shows rich, electrophoretically-detectable variation in natural populations in Texas. This isozyme variation is controlled by multiple alleles at an autosomal locus (Es-d). In each population sampled there are 9-14 alleles, two of which (Es-d(100) and Es-d(80)) predominate and form about 84% of the gene pool. Against the background of numerous rarer alleles, their frequencies are notably stable (about 65% and 19%, respectively) in ecologically variable space and time. Although adults (especially females) are capable of genetically effective dispersal, environmental heterogeneity within each locality is thought to be the prime factor maintaining the polymorphism.

Alleles↗
PubMed1967

Esterase polymorphism in natural populations of a sulfur butterfly, Colias eurytheme.

Starch-gel electrophoresis of esterases of wild and laboratoryreared individuals of Colias eurytheme indicates that populations in central Texas are exceedingly variable, consisting almost entirely of heterozygotes formed from a large number of alleles at an autosomal locus controlling the production of an esterase designated EST E. Few wild individuals are genetically identical at this locus. The commonest member of the allelic series is an apparent null allele that results in no EST E activity.

Animals↗
PubMed1965

The laser as a potential tool for cell research.

Freshly prepared hemoglobin solutions were successively irradiated up to five times with 1 MW (monochromatic wavelength) of green (530 mmicro) laser power. Oxygenated hemoglobin showed no detectable change, but the spectral absorption of reduced hemoglobin showed a shift toward the characteristic curve for the oxygenated form. Intact human erythrocytes exposed to a power density of 110 MW/cm(2) of green laser radiation showed no appreciable change in diameter or mass, but they became transparent to a wavelength range from 400 to 600 mmicro. A similar power density from a ruby laser failed to produce this bleaching effect. This response in the erythrocyte demonstrates a principle which suggests the laser as a tool for cell research: specific molecular components within a cell may be selectively altered by laser irradiation when an appropriate wavelength and a suitable power density are applied.

Cell Biology↗