Irradiated yeast

Later, Patrick and Haynes (1964) made similar observations on UV-irradiated yeast cells, showing that survival was enhanced if, after irradiation, cells were... 

Korogodin, V.I. Malumina, T.S. (1959). Recovery of viability of irradiated yeast cells. Priroda 48, 82-85 (in Russian). 

Unrau, P., Wheatcroft, R., Cox, B.S. (1971). The excision of pyrimidine dimers from DNA of ultraviolet-irradiated yeast. Molec. Gen. Genetics 113, 359-362. 

Martin-Bertram 1981,1982 Martin-Bertram et al. 1983 for DNA isolated from y-irradiated yeast cells see Andrews et al. 1984). While such lesions, detected by SI nuclease ( Sl-nuclease-sensitive sites ), are not observed with A phage DNA y-irradiated in aqueous solutions (Martin-Bertram et al. 1984), they become prominent when the solutions is highly scavenged (Junker et al. 1984). Under such conditions, the damage caused by the direct effect plays a role because the indirect effect is largely suppressed (Ward 1981). 

The vitamin D potency of milk can be increased in several ways by feeding cows substances that are high in vitamin D activity, such as irradiated yeast by irradiating milk and by adding vitamin D concentrates. The latter method is now the only commonly used procedure. The practice of irradiating milk to increase the vitamin D potency has been discontinued, undoubtedly because of the deteriorative action of the radiation on other milk components. Vitamin D is added to milk to provide a concentration of 400 IU... 

Cholesterol can be converted to vitamin D photochemically from 7-dehydrocholes-terol (provitamin D) (Special Topic 6.4) and this procedure is still used in industry.616 Vitamin D can also be made by irradiating yeasts rich in ergosterol. In addition, vitamin A (retinol) (see Special Topic 6.1) is synthesized by E Z photoisomerization (Section 6.1.1), sensitized by chlorophyll or other chromophores (Section 6.8) of its 11 -cis isomer, which is produced industrially by conventional synthetic steps.1310... 

Dried irradiated yeast. See Yeast, dried irradiated... 

Regulatory FDA 21CFR 137.260, 139.122, 139.155, 139.115, 172.842, 172.896 Yeast, dried irradiated CAS 977052-70-2 Synonyms Dried irradiated yeast Uses Vitamin D source in enriched farina Regulatory FDA 21 CFR 137.305 Yeast extract... 

Yeast that has been irradiated. Yeast contains considerable ergosterol, which, when exposed to ultraviolet light, produces vitamin D. 

Mutation. For industrial appHcations, mutations are induced by x-rays, uv irradiation or chemicals (iiitrosoguanidine, EMS, MMS, etc). Mutant selections based on amino acid or nucleotide base analogue resistance or treatment with Nystatin or 2-deoxyglucose to select auxotrophs or temperature-sensitive mutations are easily carried out. Examples of useful mutants are strains of Candida membranefaciens, which produce L-threonine Hansenu/a anomala, which produces tryptophan or strains of Candida lipolytica that produce citric acid. An auxotrophic mutant of S. cerevisiae that requires leucine for growth has been produced for use in wine fermentations (see also Wine). This yeast produces only minimal quantities of isoamyl alcohol, a fusel oil fraction derived from leucine by the Ehrlich reaction (10,11). A mutant strain of bakers yeast with cold-sensitive metaboHsm shows increased stabiUty and has been marketed in Japan for use in doughs stored in the refrigerator (12). 

Mg or Ca in MeOH, " baker s yeast, Sm/l2, LiMe2NBH3, and tin complexes prepared from SnCl2 or Sn(SR)2. This reaction, combined with RX —+ RN3 (10-65), is an important way of converting alkyl halides RX to primary amines RNH2 in some cases the two procedures have been combined into one laboratory step. Sulfonyl azides (RSO2N3) have been reduced to sulfonamides (RSO2NH2) by irradiation in isopropyl alcohol and with NaH. ... 

Ergosterol occurs in plants and yeast and is important as a precursor of vitamin D (Figure 14—18). When irradiated with ultraviolet Hght, it acquires antirachitic properties consequent to the opening of ring B. 

Studies on the active agent of the yeast extract have shown it to be nondialyzable, heat labile, and inactivated by trypsin and chymotrypsin as well as silver ions and p-hydroxymercuribenzoate.(7l) These and other properties suggest that the active agent is an enzyme. Sedimentation studies have shown that the yeast photoreactivating enzyme combines with UV-irradiated DNA, in which condition it is more resistant to heat inactivation and inactivation due to silver ions and p-hydroxymercuribenzoate.<75) The... 

It would be interesting to know if the mutational consequences of DNA lesions in mammalian cells were the same as those which obtain in bacteria. Methods for retrieving and sequencing mutations in mammalian cells and their viruses are now being developed (81-83) If yeast, a eukaryotic microorganism, can be considered representative of higher eukaryotes, then judging from the observations that the mutational spectra for UV-irradiation and 4-nitroquinoline-l-oxide treatment are identical for yeast (84) and bacteria (85), the spectrum of mutations induced by BPDE in mammalian cells could well resemble those induced in E. coli. 

A second family of MAPKs is referred to as stress-activated protein kinases (SAPKs) [3,14,15]. This includes JNKs, or Jun kinases, named originally for their phosphorylation of the transcription factor c-Jun. SAPKs were first identified in peripheral tissues on the basis of their activation in response to cellular forms of stress, which include X-ray irradiation and osmotic stress. More recently, they have been demonstrated to be activated in brain by several cytokines as well as by synaptic activity [16]. As shown in Figure 23-3, SAPKs are activated by SAPK kinases (SEKs), which are in turn activated by SEK kinases. The Ras-like small G proteins implicated in SEK kinase activation are Rac and Cdc-42. In this case, it appears that Rac/Cdc-42 triggers activation of SEK kinase by stimulating its phosphorylation by still another protein kinase termed p21-activated kinase (PAK). Thus, PAK can be considered a MAPK kinase kinase kinase, which is analogous to the cascade of protein kinases found in yeast (Fig. 23-4). 

Ergosterol CjgH OH, a trebly unsaturated alcohol, is derived from the same ring system. It is produced in relatively large amounts by fungi, in particular by yeast, and on irradiation it is isomerised to the anti-rachitic vitamin, vitamin-D (Windaus). 

Although CSN is not essential in yeast, the csnl and csn2 S. pombe deletion mutants display slow growth and sensitivity to UV- and y-irradiation [52]. Other csn mutants did not show significant phenotypes apart from the loss of culhn s dened-... 

Vitamin Dj, UV-irradiated ergocalcHerol from yeast is added to milk and other dairy products.)... 

Figure 4 (a) Lethal effect and (b) induction of genetic changes in yeast cells irradiated with x-rays tuned to resonance absorption peak [2.153 keV (triangle)] and both sides of the peak [2.147 eV (square) and 2.160 keV (circle)]. (From Ref. 18.)... 

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