Energetics of the budding cycle of Saccharomyces cerevisiae during glucose limited aerobic growth

Summary A method for the estimation of the yield on energy (Y _ATP) and of the efficiency of oxidative phosphorylation, in vivo (P/O ratio) is described, which is based on the measurement of effective gas exchange values ( and ) and of the yield coefficient Y of continuously growing populations of baker's yeast which vary in the degree of fermentation and respiration. For Y _ATP a value of 12.0±0.5 and for P/O ratio one of 1.1±0.05 was found and seems to be independent of the type of glucose catabolism (under glucose limitation).The gas exchange of populations of Saccharomyces cerevisiae synchronized at different growth rates was determined. The specific oxygen uptake and carbon dioxide formation rate, Q _{O 2}, and Q _{CO 2}, are shown to depend on the state of the cells in the budding cycle. Increase in gas metabolism and therefore increased energy generation coincides with the initiation of budding. The longer the generation time g the more expressed are these oscillations of energy formation over the budding cycle. The relationship between the course of energy generation and energy storage and the sequence of budding and single cell phase over the division cycle is discussed.     

Genetic identification of non-specific esterases of the mouse cauda epididymidis and description of esterase-28, a new carboxylesterase isoenzyme (EC 3.1.1.1)

Twenty-five (25) electrophoretic bands with esterase activity were distinguished in supernatants of cauda epididymidis of DBA/2J mice. Twenty (20) of these were assigned to 10 genetically defined esterases (ES-1, ES-2, ES-3, ES-6, ES-7, ES-11, ES-14, ES-17, ES-19, ES-22) which were already known from investigations of other mouse tissues. Furthermore, ES-10 was identified in cauda supernatants after isoelectric focussing. A hitherto genetically undefined esterase was assigned to locus Es-28 which was expressed solely in the epididymis. Three phenotypes were distinguished: ES-28A was present in the majority of the inbred strains examined. ES-28B was observed in AKR/Han mice and ES-28C was found in SEG/1 mice.     

Pituitary and ovarian responses of post-partum acyclic beef cows to continuous long-term GnRH and GnRH agonist treatment

Post-partum acyclic beef cows received continuous long-term treatment with GnRH (200 or 400 ng/kg body wt/h) or the GnRH agonist buserelin (5.5 or 11 ng/kg body wt/h) using s.c. osmotic minipumps which were designed to remain active for 28 days. All treatments increased circulating LH concentrations whereas FSH remained unchanged. Ovulation and corpus luteum (CL) formation as judged by progesterone concentrations greater than or equal to 1 ng/ml occurred in 0/5 control, 4/5 200 ng GnRH, 4/4 400 ng GnRH, 4/5 5.5 ng buserelin and 3/5 11 ng buserelin cows. The outstanding features of the progesterone profiles were the synchrony, both within and across groups, in values greater than or equal to 1 ng/ml around Day 6, and the fact that most CL were short-lived (4-6 days). Only 3 cows, one each from the 400 ng GnRH, 5.5 ng buserelin and 11 ng buserelin groups, showed evidence of extended CL function. Cows failed to show a second ovulation which was anticipated around Day 10 and this could have been due to insufficient FSH to stimulate early follicular development, or the absence of an endogenously driven LH surge. The highest LH concentrations for the respective groups were observed on Days 2 and 6 and by Day 10 LH was declining, although concentrations did remain higher than in controls up to Day 20.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of abscisic acid on somatic embryo maturation of hybrid larch

Somatic embryos of hybrid larch (Larixleptoeuropaea) whichhad been matured for 4 weeks on maturation medium, developednormally on medium supplemented with 60 µM ABA, but abnormallyon medium with no ABA. A comparative structural and histochemicalinvestigation was carried out on these two types of mature embryos.At the light microscope level, differences between both treatmentswere visible only after 2–3 weeks of maturation. At aroundthis time, abnormal development becomes evident macroscopically:ABA-minus embryos remain rather stubby as opposed to the morecylindrically shaped ABA-plus embryos. Whereas somatic embryosmatured with ABA consist of densely cytoplasmic cells showinga high rate of cell division, ABA-minus embryos are largelymade up of expanded and highly vacuolate cells, indicating thatgrowth in the latter is mainly due to cell expansion and notdivision. After 4 weeks of maturation, ABA-minus embryos beginto elongate in the hypocotyl region, and precocious germinationwas observed frequently. Again, these morphogenetic events werelargely due to abnormal timing of cell expansion. Histochemically,storage proteins were found only in somatic embryos maturedfor 4 weeks with ABA. This observation is in line with resultsobtained by total protein analysis, yielding significantly lowertotal protein contents in ABA-minus embryos both on a freshweight and a per embryo basis after 4–5 weeks of maturation.Deposition of starch grains mainly in the cortex tissue of thehypocotyl region was observed within 2 weeks of maturation invarying amounts regardless of ABA supply. Polyphenols, in particularcatechins and proanthocyanidins, were present in all embryosfrom the very onset of development. They were localized preferentiallyin the proximal suspensor cells and the basal region of theembryo. However, accumulation of polyphenols was generally muchmore pronounced in embryos matured without ABA, indicating alack of biochemical regulatory competence in those embryos. Key words: Abscisic acid, embryonal development, somatic embryo, storage protein, polyphenols     

The possible roles of residues 79 and 80 of the Trp repressor from Escherichia coli K-12 in trp operator recognition

We constructed mutants of the Trp repressor from Escherichia coli K-12 with all possible single amino acid exchanges at positions 79 and 80 (residues 1 and 2 of the recognition helix). We tested these mutants in vivo by measuring the repression of synthesis of β-galactosidase with symmetric variants of α- and β-centered trp operators, which replace the lac operator in a synthetic lac system. The Trp repressor carrying a substitution of isoleucine 79 by lysine, showed a marked specificity change with respect to base pair 7 of the α-centered trp operator. Gel retardation experiments confirmed this result. Trp repressor mutant IR79 specifically recognizes a trp operator variant with substitutions in positions 7 and 8. Another mutant, with glycine in position 79, exhibited loss of contact at base pair 7. We speculate that the side chain of Ile79 interacts with the AT base pairs 7 and 8 of the α-centered trp operator, possibly with the methyl groups of thymines. Replacement of thymine in position 7 or 8 by uracil confirms the involvement of the methyl group of thymine 8 in repressor binding. Several Trp repressor mutants in position 80 (i.e. AI80, AL80, AM80 and AP80) broaden the specificity of the Trp repressor for α-centered trp operator variants with exchanges in positions 3, 4 and 5.     

An on-line advisory control system for the lactic acid fermentation process

A fuzzy expert system was developed for online diagnosing and controlling of bioprocesses. The system was constructed in object-oriented Smalltalk/V for diagnosing and controlling of bioprocesses. Lactic acid fermentation with an industrial strain ofLactobacillus casei was chosen as the model system. The performance of the fuzzy expert system and the knowledge base utilizing experts' knowledge and several facts obtained from the experiments were successfully validated with on-line fermentations. The fuzzy expert system could diagnose a fault on-line and give reasonable advice to the process operator. In order to achieve the diagnosing faculty, a database, a knowledge base, and both backward and forward chaining procedures were implemented employing the object-oriented programming environment. A defuzzifier was implemented in the system to achieve on-line control. In order to realize a decision-making system with a human operator and a fuzzy expert system, a new control strategy namedAdvice was also introduced. Several cultivations were carried out in order to collect knowledge on the effects concerned with inoculum properties to the process and to construct a database including standard time-course profiles. The performance of the fuzzy expert control system was successfully tested with on-line experiments.Visiting scientist from HUT at RIKEN