Metabolic epidemiology of large bowel cancer. Fecal mutagens in high- and low-risk population for colon cancer. A preliminary report

Because of potential significance of fecal mutagens in the pathogenesis of colon cancer, the dietary pattern and fecal mutagens of 3 populations with distinct risk for the development of colon cancer, a high-risk population in New York Metropolitan area (non-Seventh-Day Adventists), a low-risk population of vegetarian Seventh-Day Adventists in New York Metropolitan area and a low-risk population in rural Kuopio, Finland were studied. The average daily intake of protein was the same in the 3 groups, but the sources were different, a greater portion coming from meat in the New York non-Seventh-Day Adventists and from vegetables in Seventh-Day Adventists. The intake of fat was lower in Seventh-Day Adventists and higher in Kuopio and in New York non-Seventh-Day Adventists. The intake of dietary fiber was high in Kuopio compared to other groups. Fecal samples collected for 2 days were freeze-dried extracted with peroxide-free diethyl ether, partially purified on a silica-gel column and assayed for mutagenicity using the Salmonella/mammalian microsome mutagenicity test. The mutagenic activity was observed with Salmonella typhimurium tester strain TA98 without microsomal activation and with TA100 with and without microsomal activation in high-risk subjects from New York consuming a high-fat, high-meat diet. The incidence of fecal mutagen activity was higher in volunteers from New York consuming a high-fat, high-meat diet compared to low-risk rural Kuopio population. None of the vegetarian Seventh-Day Adventists showed any mutagenic activity.     

The messenger RNA sequences in human fibroblast cells induced with poly rI.rC to produce interferon

Induction of human fibroblast cells with poly rI.rC induces interferon mRNA which can be translated into interferon precursor in wheat germ cell free system or in Xenopus oocytes into biologically active interferon. The extent of gene expression in the poly rI.rC induced cells was compared to that of the uninduced cells by hybridization of the mRNA to complementary DNA. Homologous template driven hybridization of cDNA revealed the presence of two clearly defined transitions in the total poly A RNA from the induced cells; abundant class and a scarce class comprising approximately 37,000 diverse species of RNA. Heterologus hybridization of the cDNA with total uninduced mRNA showed that the majority of the mRNA sequences are the same in both the induced and uninduced cells. The results of the hybridization using cDNA prepared to the fraction enriched for interferon mRNA, however, showed that about 4% of the sequences present in the interferon enriched fraction are not present in the uninduced cells. These differences may result from the poly rI.rC induced alterations in gene expression.     

Studies on anther cultures of tomato —Lycopersicon esculentum Mill

The anthers of three genotypes ofLycopersicon esculentum, viz. cv. HS-101, cv. HS-102 and an F₁ hybrid (Montfavet 63-4xHS-101) in different stages of development were cultured in various defined nutritive media. Only anthers containing microspores in the early uninucleate stage were found to respond with the culture medium in the formation of androgenic callus. The DGII medium with 2 mg l⁻¹ NAA and 1 mg 1⁻¹ kinetin was found to be best for callus induction but MS medium supplemented with 2 mg l⁻¹ 2,4-D and 0.1 mg 1⁻¹ BAP favoured proliferation and growth of the callus. The androgenic microspores followed the ‘B’ type pathway of androgenesis in the formation of callus. Induction of tracheids in the callus could be achieved by supplementing the basal medium with NAA and kinetin or 2,4-D and BAP. Initiation of vessel elements and cambium were favoured by addition of NAA and kinetin and that of the phloem in the presence of 2,4-D and BAP in the basal medium, suggesting that the hormonal requirements for production of different elements of the vascular system in androgenic callus are different. Although roots could be induced from the callus, shoot differentiation could not be achieved under cultural conditions.     

Fatty acid composition of oil synthesized byaspergillus nidulans

The filamentous fungusAspergillus nidulans Eidam strain 300 was found to be capable of synthesizing 24.9 % oil of remarkably low free fatty acidity, in a chemically defined medium with 34 % glucose as sole carbon source. Although the total content of oil synthesized was less, utilization of the carbon source is better as shown by the high (8.4) fat coefficient. The major component fatty acids of the oil were palmitic, stearic, oleic and linoleic and are influenced by the source of carbon. Palmitoleic acid is present in traces, confirming thereby the general observation that high oil formers produce oil of low hexadecenoic acid content. The relatively high stearic acid content of the oil distinguishes it from those of other microorganisms and resembles the oil produced by certain tropical plants, such asMadhuca latifolia.     

The broad spectrum antiviral agent ribavirin inhibits capping of mRNA.

Ribavirin (1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a broad spectrum antiviral substance active against a wide range of both DNA and RNA viruses. It is, however, virtually inactive against polio virus. Its pharmacological mechanism of action was obscure. A possible common target for a chemotherapeutic agent in both DNA and RNA viruses is the “capping” reaction of mRNAs which $\text{inter}\text{alia}$ involves the formation of a guanine pyrophosphate structure at the 5′ terminus by mRNA guanylyl transferase. We have observed that Ribavirin triphosphate is a potent competitive inhibitor of the capping guanylation of viral mRNA. This finding could account for the antiviral potency of the drug against both DNA and RNA viruses and its ineffectiveness against a virus in which the mRNAs derived from them are not capped.