The effects of triiodothyronine administration and of hypothyroidism on the rapidly developing enzymes UDP galactose : sphingosine galactosyltransferase and 2' : 3'-nucleotide 3'-phosphohydrolase associated with central nervous system myelination were investigated. The activity of these enzymes in the spinal cords of young rats injected daily with triiodothyronine up to sacrifice on day 5 was significantly increased over control animals. In normal animals, circulating plasma thyroxine increased gradually from the second postnatal day t o a maximum value a t days 15-17. Rats, born of mothers treated with n-propylthiouracil from the thirteenth day of pregnancy, did not exhibit the increase in plasma thyroxine. Determination of the specific activity of these enzymes in central nervous tissue of such hypothyroid rats a t day 12 showed a significant reduction compared with normal animals. Intraperitoneal injection of the hypothyroid rats with triiodothyronine on day 8 resulted in a partial restoration of the activity of the enzymes in brain and of 2' : 3'-nucleotide 3'-phosphohydrolase in spinal cord when assayed on day 12. Restoration of UDPgalactose : sphingosine galactosyltransferase activity did not occur in the spinal cord of such animals. However, when hypothyroid rats were injected with triiodothyronine on days 1,4, and 7, the psychosine-synthesising activity in their spinal cords on day 8 was restored to that of normal animals. This suggests that there is a critical period during the first 8 days of postnatal life when thyroid hormone levels must be adequate in order that spinal cord activity of this enzyme develops normally. It is concluded that the flux in circulating thyroid hormone is a factor in the normal development of these enzymes.

In this paper, we show that a wide variety of common soil bacteria are able to obtain their carbon and energy needs from tholin (a class of complex organic heteropolymers thought to be widely distributed through the solar system; in this case tholin was produced by passage of electrical discharge through a mixture of methane, ammonia, and water vapor). We have isolated aerobic, anaerobic, and facultatively anaerobic bacteria which are able to use tholin as a sole carbon source. Organisms which metabolize tholin represent a variety of bacterial genera including Clostridium, Pseudomonas, Bacillus, Acinetobacter, Paracoccus, Alcaligenes, Micrococcus, Corynebacterium, Aerobacter, Arthrobacter, Flavobacterium, and Actinomyces. Aerobic tholin-using bacteria were first isolated from soils containing unusual or sparse carbon sources. Some of these organisms were found to be facultatively anaerobic. Strictly anaerobic tholin-using bacteria were isolated from both carbon-rich and carbon-poor anaerobic lake muds. In addition, both aerobic and anaerobic tholin-using bacteria were isolated from common soil collected outside the laboratory building. Some, but not all, of the strains that were able to obtain carbon from tholin were also able to obtain their nitrogen requirements from tholin. Bacteria isolated from common soils were tested for their ability to obtain carbon from the water-soluble fraction, the ethanol-soluble fraction, and the water/ethanol-insoluble fraction of the tholin. Of the 3.5 x 10(7) bacteria isolated per gram of common soils, 1.7, 0.5, and 0.2%, respectively, were able to obtain their carbon requirements from the water-soluble fraction, the ethanol-soluble fraction and the water/ethanol-insoluble fraction of the tholin. The palatability of tholins to modern microbes may have implications for the early evolution of microbial life on Earth. Tholins may have formed the base of the food chain for an early heterotrophic biosphere before the evolution of autotrophy on the early Earth. Where tholins are present on other planets, they could possibly be metabolized by contaminant microorganisms transported to these bodies via spacecraft. Thus, the presence of tholins should be taken into account when evaluating the planetary quarantine requirements for probes to other planets.

The bulbous roots of Haemodorum corymbosum Vahl. yield a red crystalline glycoside, haemocorin, which is readily hydrolysed to cellobiose and the purple-red aglycone, C20H14O4. The latter contains one methoxyl group and gives a diacetate and isomeric mono- and dimethyl ethers. The absorption spectra and other properties of these compounds suggest a polycyclic tautomeric enolone structure. Oxidation of a dimethyl ether gives a compound C22H18O7, believed to be a lactol ester, and a compound C20H14O5, which is apparently a polycyclic aromatic anhydride. These results indicate that the aglycone is a polycyclic enolic α-diketone, possibly of the indandione type.

Oxidation of the aglycone dimethyl ether B gives a cyclic anhydride isomeric with that previously obtained from dimethyl ether A. The chemical properties and absorption spectra of the two anhydrides and their derivatives suggest that they are dimethoxyphenylnaphthalic anhydrides with the methoxyl groups attached to the naphthalene ring system. Further degradation of the anhydrides eventually gives diphenyl-2,3,4-tricarboxylic acid. This is proved by decarboxylation to diphenyl and by the formation of an anilide phenylimide identical with a synthetic specimen. These results indicate that the aglycone is a dihydroxymethoxyphenylperinaphthenone, and further support is given by a study of model hydroxyperinaphthenones.

A mechanism for the biosynthesis of fluoroacetic acid is presented. This is based on a correlation of phytochemical and taxonomic data together with the established function of pyridoxal phosphate in general amino acid metabolism. Evidence for this hypothesis is based on the reported incorporation of a wide range of synthetic nucleophiles into corresponding j3-substituted alanines by plant homogenates. Fluoride ion is considered to be an acceptable nucleophile for a non-specific enzyme synthesizing a range of j3-substituted alanines, many of which occur in plants elaborating fluoroacetic acid.It is considered that, initially, fluoride is covalently bound to a C3 entity linked to pyridoxal phosphate and which is derived from cysteine, serine, or derivatives. The mechanism for fluoride incorporation is considered to involve direct attack on a carbonium ion but may occur by an exchange process, as nucleophile exchange occurs in j3-substituted alanines in closely related plants.Fluoroacetic acid is considered to be derived from the fluoro-(Ca-pyridoxal phosphate) unit either by (1) transamination and release of fluoropyruvic acid which may produce fluoroacetic acid by an oxidative decarboxylation process, or (2) by decarboxylation, transamination, and hydrolytic release of fluoroacetaldehyde which may be oxidized to fluoroacetic acid.