Integration of an aberrant retrotransposon in Saccharomyces cerevisiae.

We describe an atypical composite Ty1 element that apparently resulted from the concurrent integration of two complete elements. A portion of the central region of one of these elements was inverted between two long terminal repeats. Inversions of this type have been detected among unintegrated retroviral circles. It now appears that such intermediates can be incorporated into the genome.     

By-product inhibition effects on ethanolic fermentation by Saccharomyces cerevisiae

Inhibition by secondary fermentation products may limit the ultimate productivity of new glucose to ethanol fermentation processes. New processes are under development whereby ethanol is selectively removed from the fermenting broth to eliminate ethanol inhibition effects. These processes can concentrate minor secondary products to the point where they become toxic to the yeast. Vacuum fermentation selectively concentrates nonvolatile products in the fermentation broth. Membrane fermentation systems may concentrate large molecules which are sterically blocked from membrane transport. Extractive fermentation systems, employing nonpolar solvents, may concentrate small organic acids. By-product production rates and inhibition levels in continuous fermentation with Saccharomyces cerevisiae have been determined for acetaldehyde, glycerol, formic, lactic, and acetic acids, 1-propanol, 2-methyl-1-butanol, and 2,3-butanediol to assess the potential effects of these by-products on new fermentation processes. Mechanisms are proposed for the various inhibition effects observed.     

Formalin fixation strongly influences biomechanical properties of the spine

As fresh human cadaveric spine specimens for in vitro testing are hard to obtain and carry a potential risk of infection, the possibility of using embalmed spine specimens has been considered. The cross-linking effect of formalin fixation, however, raises uncertainties regarding the biomechanical likeness of preserved specimens. They have been reported to be stiffer, but no quantitative data exist.

The purpose of this study was to determine the biomechanical differences between fresh and formalin-fixed spine specimens, using L1–2 motion segments from six 16-week-old calf spines. The range of motion and neutral zone were determined in flexion-/extension, left/right axial rotation, and right/left lateral bending.

The range of motion decreased in the formalin fixed specimens by as much as 80%, and the neutral zone by as much as 96%. The results of this study therefore imply that, for biomechanical testing, formalin-fixed specimens are not representative of the in vivo conditions.     

Comparison of voice stress reactivity under psychological stress test and simulated Mir docking manoeuvre

The relation between the results of laboratory tests and results of the interesting professional work is a very difficult one. The same is true for the relation between training and real performance. The pilot controlled MIR-docking manoeuvre is in reality a very seldom but very important one. The training of this manoeuvre is a very special professional work and only for cosmonauts available. But the objective estimation of the performance and the used objective and subjective needs is nevertheless necessary. Even for the subjective "stress"-feelings during task solving it is often impossible to get reliable data without any physiological measurements. The use of electrodes, cables and equipments is hardly limited during real work. Sometimes only the voice is available over more or less quality communication channels. So it is the case during the training and the real pilot controlled MIR-docking manoeuvre. Based on findings in the literature and own experiments analyzing the relation between fundamental voice frequency (F0) and subjective stress feelings we tested the hypothesis that a on-line measurement of F0 can be used for stress evaluation during standardised training sessions of MIR-docking manoeuvres.     

The Biochemical Response of Electrical Signaling in the Reproductive System of Hibiscus Plants

Stimulation of the stigma of Hibiscus flowers by pollen, wounding (heat), or cold shock (4[deg]C) evokes electrical potential changes in the style, which propagate toward the ovary with a speed of 1.3 to 3.5 cm s-1. Potential changes were measured intracellularly by microelectrodes inserted in the style. The resting potential ranged from -90 to -112 mV (n = 20) in cells of the vascular tissue and from -184 to -220 mV (n = 22) in cells of the pollen-transmitting tissue. The amplitude of the potential changes was between 40 and 150 mV, depending on the kind of stimulus. Self- as well as cross-pollination hyperpolarized the resting potential after 50 to 100 s, followed by a series of 10 to 15 action potentials. In contrast, cooling of the stigma caused a single action potential with a different shape and duration, whereas wounding generated a strong depolarization of the membrane potential with an irregular form and a lower transmission rate. To determine the physiological function of the different signals measured in the style, the gas exchange and metabolite concentrations were measured in the ovary before and 10 min after stimulation of the stigma. Self- and cross-pollination caused a transient increase of the ovarian respiration rate by 12%, which was measured 3 to 5 min after the stigma was stimulated. Simultaneously, the levels of ATP, ADP, and starch increased significantly. In contrast, both cold shock and wounding of the stigma caused a spontaneous decrease of the CO2 content in the measuring chamber, as well as reduced metabolite concentrations in the ovary. Since the transport of labeled auxin from the top to the base of the style lasts at least 45 min, the influence of a chemical substance transmitted within 10 min is unlikely. Thus, our results strongly support the view that different, stimulus-dependent electrical signals cause specific responses of the ovarian metabolism.     

Lactase production in continuous culture by Trichoderma reesei Rut-C30

Summary Trichoderma reesei Rut-C30 was found to produce extracellular lactase when grown on lactose medium. Maximum enzyme levels in continuous culture were observed at dilution rates (D) between 0.02 and 0.027 hr^-1. The enzyme productivity reached 27.3 U/L hr at D = 0.027 hr^-1. Lactase synthesis appears to be inducible and subject to catabolite repression. Optimal growth temperature and pH for enzyme production were 28°C and pH 5. Maximum enzyme activity was observed at 63°C and pH 4.6. The apparent K_m, based on the nitrophenyl-galactopyranoside assay was estimated as 0.4 mM. The enzyme is suitable for lactose hydrolysis in acid whey.     

Studies on the (pro) insulin biosynthesis of islets of Langerhans of sand rats (Psammomys obesus).

By feeding a regular laboratory chow, sand rats (Psammomys obesus) from our breeding colony gained different body weights, though they received approximately the same quantity of calories. Sand rats, reaching a body weight above 160 g (group B) showed significantly increased blood glucose values in contrast to the animals with a body weight under 160 g (group A). Isolated pancreatic islets of these two groups of sand rats were incubated with [3H]-leucine to study the incorporation of this amino acid into proinsulin and insulin. The incorporation into proteins of pancreatic islets of sand rats of group B was stimulated by 0.45 mg and 3.0 mg/ml glucose. In group A there was no further stimulation from 0.45 mg to 3.0 mg/ml glucose. Insulin secretion could be stimulated by glucose in both groups, but the stimulation was stronger in group B than in group A.     

Computation of the fraction of induced cells in enzyme induction systems

A theoretical model is developed for continuous multistage enzyme production systems, which consist of a growth fermentor used for growing microorganisms rapidly without enzyme production and a subsequent system of induction reactors in which enzymes induction and production occurs. The model allows the computation of the fraction of induced cells residing in the induction reactor for organisms exhibiting a lag phase in enzyme induction. For this model a general analytical solution was obtained for the cumulative internal residence time distribution of a series of n well-stirred vessels with a recycle. The theoretical results are compared in a preliminary way with experimentally measured cellulase productivities of continuous multistage cellulose fermentations with Trichoderma viride QM 9414.     

Functional and morphological characteristics of isolated pancreatic islets in tissue culture

Islets were isolated from the pancreas of female rats by using the collagenase technique. After culturing for 4 days, the islets were taken for measurement of insulin release biosynthesis as well as glucose utilization in subsequent short-time incubations. A low glucose concentration was insufficient to maintain a glucose-stimulated insulin release in vitro. A high glucose concentration had a protecting and restoring effect on the insulin release: ultrastructurally, such islets showed signs of an active biosynthesis in the electron micrograph. The enhancement of Mg++ in the culture medium resulted in an improvement of insulin storage in the islets, accompanied by a well-preserved action of glucose in a subsequent incubation.     

Apoplastic expression of yeast-derived invertase in potato : effects on photosynthesis, leaf solute composition, water relations, and tuber composition

In potato plants (Solanum tuberosum), a chimeric yeast-derived invertase gene fused to a 35S cauliflower mosaic virus promoter has been expressed. The protein was targeted to the cell wall by using the signal peptide of proteinase inhibitor II fused to the amino terminus of the yeast invertase. The transformed plants had crinkled leaves, showed a reduced growth rate, and produced fewer tubers. Although in the apoplast of the leaves of the transformed plants the content of glucose and fructose rose by a factor of 20, and that of sucrose declined 20-fold, 98% of the carbohydrate in the phloem sap consisted of sucrose, demonstrating the strong specificity of phloem loading. In the leaf cells of the transformed plants, glucose, fructose, and amino acids, especially proline, were accumulated. Consequently, the osmolality of the cell sap rose from 250 to 350 mosmol/kg. Our results show that the observed 75% decrease of photosynthesis is not caused by a feedback regulation of sucrose synthesis and is accompanied by an increase in the osmotic pressure in the leaf cells. In the transformed plants, not only the amino acid to sucrose ratio in the phloem sap, but also the amino acid and protein contents in the tubers were found to be elevated. In the tubers of the transformed plants, the protein to starch ratio increased.