Stress-induced expression of the heat shock (hs) genes in eukaryotes is mediated by a transcription factor known as heat shock factor 1 (HSF1). HSF1 is present in a latent, monomeric form in unstressed metazoan cells and upon exposure to heat or other forms of stress is converted to an "active" trimeric form, which binds the promoters of hs genes and induces their transcription. The conversion of HSF1 to its active form is hypothesized to be a multistep process involving (i) oligomerization of HSF1, plus (ii) additional changes in its physical conformation, (iii) changes in its phosphorylation state, and for some species (iv) translocation from the cytoplasm to the nucleus. Oligomerization of HSF appears to be essential for high affinity DNA binding, but it remains unclear whether the other steps occur in all organisms or what their mechanistic roles are. In this study we have examined if heat-induced cytoplasmicnuclear translocation of HSF1 occurs in Xenopus oocytes. We observed that germinal vesicles (nuclei) that were physically dissected from unshocked Xenopus laevis oocytes contain no HSF1 binding activity. Interestingly, in vitro heat shock treatments of isolated nuclei from unshocked oocytes activated HSF1 binding, indicating that HSF1 must have been present in the unshocked nuclei prior to isolation. Induction of HSF1 binding was not observed in enucleated oocytes. Western blot analysis using an affinity-purified polyclonal antibody made against X. laevis HSF1 showed that HSF1 is present in equal amounts in unshocked and shocked oocytes and isolated nuclei. HSF1 was not detected in enucleated oocytes. These results clearly demonstrate that HSF1 is a nuclear protein in oocytes prior to exposure to stress. In Xenopus oocytes, therefore, HSF1 translocation from the cytoplasm to the nucleus is not part of the multistep process of HSF1 activation. These results also imply that the signals and/or factors involved in HSF1 activation must have their effect in the nuclear compartment.

A 450-m(3) multiplate anaerobic reactor (MPAR) has been started-up in April 1992 for treating wastewater (whey permeate and domestic wastewater) at the Nutrinor (Lactel) cheese factory in Chambord (Québec, Canada). The MPAR consists of four superimposed sections. The liquid flows upwards from one section to the next, while the gas is collected below each plate and evacuated through side-outlets. The wastewater is concurrently distributed at the bottom of the first, second, and third sections, as 50%, 33%, and 17% of the total influent stream, respectively. Granular anaerobic sludge at an initial concentration of 30 kg of volatile suspended solids (VSS) per cubic meter of reactor liquid volume was used to inoculate the reactor. Under normal operation of the factory, the chemical oxygen demand (COD) concentration of the influent ranged from 20 to 37 kg COD m(-3). The reactor organic loading rate (OLR) fluctuated between 9 and 14.7 kg COD m(-3) d(-1) for hydraulic retention times (HRT) maintained between 55 and 68 h. At the highest OLR, the MPAR showed an efficiency of 98% and 92% for soluble and total COD removal, respectively, and a methane production rate averaging around 4 m(3) m(-3) d(-1).Biomass-specific activities ranged between 7 and 51, 1.3 and 8.5, 5.3 and 12.2, 60 and 119, and 119 and 211 mmol g(-1) VSS d(-1) for glucose, propionate, acetate, formate, and hydrogen, respectively. Average equivalent-diameter of the granules was around 0.65 mm. The MPAR reactor generally showed a large capacity for solid retention with a biomass content between 32 and 37 kg VSS m(-3).

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