H.S. Forrest

RNA and DNA Synthesis in Developing Eggs of the Milkweed Bug, Oncopeltus fasciatus (Dallas)

Ribosomal RNA synthesis in developing eggs of the milkweed bug, Oncopeltus fasciatus (Dallas), is turned on at gastrulation and is essentially turned off when organogenesis begins about 72 hours later. The pattern for DNA synthesis is similar although less pronounced.

Dispersity of Repeat DNA Sequences in Oncopeltus fasciatus, an Organism with Diffuse Centromeres

DNA of Oncopeltus fasciatus, an organism with diffuse centromeres, has been characterized by determination of its base composition, buoyant density, thermal stability, and reassociation kinetics; renatured DNA was characterized similarly. We conclude that repeated sequences are primarily short and scattered throughout the genome. This is in contrast to the extensive tandem repeats which are found in DNAs of organisms with discrete centromeres.

Studies on the pteridines in the milkweed bug, Oncopeltus fasciatus (Dallas)☆

Abstract A quantitative re-examination of the pteridines in Oncopeltus has given results at variance with those published previously. The precursors of the red pteridine, erythropterin, are xanthopterin and, probably, oxalacetic acid. Xanthopterin is not present as such in Oncopeltus eggs but exists as 7,8-dihydroxanthopterin. Chrysopterin and biopterin have also been isolated and identified from later growth stages of the bug.

Inhibition of tryptophan pyrrolase by some naturally occurring pteridines

Abstract Pteridines of the biopterin type, but not some closely related compounds, inhibit the activity of tryptophan pyrrolase in preparations from rat liver and from Drosophila melanogaster ; this suggests an in vivo control over the activity of the enzyme which may at least partially account for the phenotype in white mutants of Drosophila .

Inosine, guanosine, uric acid, DNA, and RNA in developing eggs of the milkweed bug Oncopeltus fasciatus (Dallas)☆

Abstract Young Oncopeltus eggs contain relatively large amounts of inosine which disappears during development. The guanosine content similarly decreases but less dramatically. Uric acid, on the other hand, stays relatively constant, a result in contrast to previously published reports. There is a rough correlation between the disappearance of the purine nucleosides and the synthesis of DNA and RNA during development. Thus the nucleosides probably act as stored precursors for the synthesis of one or other or both of these macromolecules.

Pteridine content of some photosynthetic bacteria

Abstract A simple procedure for estimating total 2-amino-4-hydroxypteridinyl compounds in microorganisms has been used to demonstrate that some photosynthetic bacteria contain relatively large amounts of such compounds, and, generally, that their concentration is higher when the organism is grown in the light, anaerobically, as opposed to dark, aerobic growth where this is possible.

Isolation and characterization of a yellow pteridine from the blue-green alga, Anacystis nidulans

Abstract A yellow pteridine has been isolated in relatively large amounts from the blue-green alga Anacystis nidulans. A number of degradative experiments on the pure crystalline material have led to a proposed structure for this compound. Some of its interesting chemical properties have been pointed out, and, largely on the basis of these, suggestions have been made as to its possible biological function.

RNA polymerase activity in isolated nuclei from eggs of Oncopeltus fasciatus

Nuclei, isolated from various developmental stages of the eggs of the milkweed bug Oncopeltus fasciatus, have been assayed for RNA polymerase activity in the presence of Mg2+ ions and in a low salt environment. This activity changes during development. These changes can be correlated with in vivo changes in the rate of RNA synthesis. The base composition of the RNA transcribed in vitro is intermediate between ribosomal RNA and DNA-like RNA.

Photosynthetic Phosphorylation: Stimulation by Pteridines and a Comparison with Phosphodoxin

A number of pteridine derivatives stimulate photosynthetic phosphorylation in spinach chloroplasts. In general, tetrahydro or dihydro compounds are highly active, as is one aromatic, naturally occurring compound, biopterin. The physiological characteristics of this photosynthetic phosphorylation are the same as those described for phosphodoxin. A pteridine-containing fraction from spinach, with the same RF value as phosphodoxin, is also active.

A mechanism for the enzymic oxidation of methanol involving methoxatin.

Summary A novel reaction mechanism, consistent with available experimental evidence, is proposed for the oxidation of methanol and other substrates involving the new coenzyme, methoxatin, and methanol dehydrogenases from methane- and methanol-oxidizing bacteria. It also may be applicable to NADP-independent glucose oxidases.