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Biomedical subjects

S Tu

Publications and source records attributed to S Tu.

42 records · Page 3Linked to original sources
PubMed1976

Cortisol modification of HeLa 65 alkaline phosphatase. Decreased phosphate content of the induced enzyme.

Alkaline phosphatase activity of HeLa cells is increased 5-20-fold during growth in medium with cortisol. The increase in enzyme activity is due to an enhanced catalytic efficiency rather than an increase in alkaline phosphatase protein in induced cells. In the present study the chemical composition of control and induced forms of alkaline phosphatase were investigated to determine the enzyme modification that may be responsible for the increased catalytic activity. HeLa alkaline phosphatase is a phosphoprotein and the induced form of the enzyme has approximately one-half of the phosphate residues associated with control enzyme. The decrease in phosphate residues of the enzyme apparently alters its catalytic activity. Other chemical components of purified alkaline phosphatase from control and induced cells are similar; these include sialic acid, hexosamine and sulfhydryl residues.

Alkaline Phosphatase↗
PubMed1975

Differential effects of 8-anilino-1-naphthalenesulfonate upon binding of oxidized and reduced flavines by bacterial luciferase.

Upon binding to bacterial luciferase, both the absorption and the fluorescence excitatiom maxima of 8-anilino-1-naphthalensulfonate (ANS) shift from 353 to 370 nm while the fluorescence emission optimum shifts from 540 to 480 nm, and the fluorescence quantum yield increases from 0.003 to 0.39, indicating that the environment of the ANS binding site is hydrophobic. ANS binds to luciferase with dissociation constants of 1.9 X 10(-5) and 2.3 X 10(-5) M at 5 and 23 degrees, repsectively. As with both oxidized flavine mononucleotide (FMN) and reduced flavine mononucleotide (FMNH2), ANS also binds to luciferase with a stoichiometry of 1 site per dimeric luciferase molecule. ANS acts as a luciferase inhibitor, competitive with FMNH2, with an inhibitor constant of 2.3 X 10(-5) M at 23 degrees. However, the binding of ANS does not significantly displace FMN from binding to luciferase. Interactions of FMN and FMNH2 with luciferase are thus differentially regulated by the ANS binding.

Anilino Naphthalenesulfonates↗
PubMedDate not supplied

Development and regulation of substance P expression in neurons of the tadpole optic tectum.

Activity-dependent synaptic plasticity is characteristic of developing visual systems. Using the frog retinotectal system, we investigated the extent to which afferent input affects neurotransmitter expression in a target structure. We have concentrated on a particular subpopulation of tectal cells that is immunoreactive to substance P (SP). Early in development, SP expression in tectal neurons was restricted to the anterior lateral region of the tectum. As tadpoles developed, this expression expanded into progressively more posterior and medial regions in a manner that closely followed the gradient of tectal maturation. At all times, however, anterior and lateral tectal regions had a greater percent of SP-like immunoreactive (SP-ir) cells than posterior and medial ones. Horseradish peroxidase (HRP) labeling of the retinal ganglion cell projection in conjunction with SP immunocytochemistry demonstrated that innervation by retinal ganglion cell terminals preceded the expression of SP by tectal cells. This suggested that the optic nerve may influence SP differentiation and/or expression. In support of this idea, transection of the optic nerve resulted in a decrease in SP expression in the deafferented tectal lobe of tadpoles. This result, opposite to that seen previously in the adult, also indicates that optic nerve-dependent regulation of SP expression in the developing and mature systems occurs through different pathways.

Animals↗