Genetic analysis of the yeastCandida maltosa by means of induced parasexual processes

The usefulness of hybridization by protoplast fusion and mitotic segregation for the genetic analysis of the imperfect fodder yeastCandida maltosa was tested. Mitotically stable fusion hybrids were obtained with frequencies between 10^–6 and 10^–7. Complementation tests were performed by protoplast fusion. Substances that are known to induce frequent mitotic segregation in other yeast species such as benomyl, p-fluorophenylalanine, and acriflavine were ineffective inC. maltosa. UV irradiation induced mitotic segregation in up to 10%. This agent induced mainly mitotic crossing over inC. maltosa. Our data enabled the construction of the linkage group I with the sequenceCEN-ade-26-pro-1.     

The effective diffusion coefficient and the distribution constant for small molecules in calcium-alginate gel beads

The effective diffusion coefficient, D(e), and the distribution constant, K(i), for selected mono- and disaccharides and organic acids were determined in homogeneous calcium-alginate gel with and without entrapped bacteria. Results were obtained from transient concentration changes in well-stirred solutions of limited volume, in which the gel beads were suspended. The effective diffusioncoefficients and the distribution constants were estimated by fitting mathematical model predictions to the experimental data using a nonlinear model fitting program (MODFIT). Both single solute diffusion and multiple solute diffusion were performed. A small positive effect was obtained onthe values of D(e) for the system of multiple solute diffusion; however, the values of K(i) were not significantly influenced. For the nine solutes tested, D(e) for 2% Ca-alginate gel beads was found to be approximately 85% of the diffusivity measured in water. The effects on D(e) and K(i), for lactose and lactic acid were determined for variations of alginate concentration, pH, temperature, and biomass content in the beads. D(e) decreased linearly for both lactose and lactic acid with increasing cell concentration in the Ca-alginate gel. K(i), was constant for both lactose and lactic acid with increasing cell concentration. D(e) was significantly lower at pH 4.5 than at pH 5.5 and 6.5 for both lactose and lactic acid. Furthermore, D(e) seemed to decrease with increased alginate concentration in the range of 1% to 4%. The diffusion rate increased with increasing temperature, and the activation energy for the diffusion process for both lactose and lactic acid was constant in the temperature range tested. (c) 1995 John Wiley & Sons Inc.     

Pretreatment Antibiotic Resistance in Helicobacter pylori Infection: Results of Three Randomized Controlled Studies

Background. Although combinations of antibiotics and antisecretory drugs are useful for treatment of Helicobacter pylori infection, treatment failure is common. The aim of this study was to evaluate the relation between pretreatment antibiotic resistance and outcome by using six different treatment regimens for H. pylori infection. Patients and Methods. Three hundred sixty-nine consecutive H. pylori–infected patients with dyspeptic symptoms were enrolled in three consecutive randomized, controlled, single-center clinical trials: trial A, 128 patients; trial B, 125 patients; trial C, 116 patients. Treatments consisted of (A) a 15-day course of dual therapy (omeprazole, 20 mg bid, and amoxicillin, 1 gm bid, or clarithromycin, 500 mg tid) (OA vs OC); (B) a 7-day triple therapy of omeprazole, 20 mg bid, plus metronidazole, 500 mg bid, and amoxicillin, 1,000 mg bid, or clarithromycin, 500 mg tid (OMA vs OMC); or (C) omeprazole, 20 mg bid, plus metronidazole, 500 mg bid, plus tetracycline, 500 mg qid, or doxycycline, 100 mg tid (OMT vs OMD). Diagnostic endoscopy was made in all patients before and 5 to 6 weeks after therapy. Six biopsies were taken from each patient for histology, rapid urease test, and H. pylori culture; antibiotic susceptibility testing was performed using the E-test method. Results. Overall cure rates were poor for both dual therapies OA and OC (38% and 37%, respectively) and for triple therapies OMA, OMC, and OMD (57%, 55%, and 58%, respectively). The OMT combination was successful in 91% (95% confidence interval [CI], 80.4%–97%). Metronidazole resistance was present in 29.7% (95% CI, 24%–35%), amoxicillin resistance was present in 26% (95% CI, 21%–32%), clarithromycin resistance was present in 23.1% (95% CI, 18%–29%), tetracycline resistance was present in 14% (95% CI, 10%–20%), and doxycycline resistance was present in 33.3% (95% CI, 21%–47%). Antibiotic resistance markedly reduced the cure rates and accounted for most of the poor results with the triple therapies: 89% versus 23%; 77% versus 26%; 100% versus 60%; and 67% versus 23% for OMC, OMA, OMT, and OMD, respectively. OMT appeared to be the best because of the high success rate with metronidazole-resistant H. pylori (71%) and in low-level tetracycline resistance. Conclusions. Pretreatment antibiotic-resistant H. pylori can, in part, explain the low cure rate of the infection and the variability in outcome in reported trials.     

Ecosystem-level effects of re-oligotrophication and N:P imbalances in rivers and estuaries on a global scale

Trends and ecological consequences of phosphorus (P) decline and increasing nitrogen (N) to phosphorus (N:P) ratios in rivers and estuaries are reviewed and discussed. Results suggest that re-oligotrophication is a dominant trend in rivers and estuaries of high-income countries in the last two–three decades, while in low-income countries widespread eutrophication occurs. The decline in P is well documented in hundreds of rivers of United States and the European Union, but the biotic response of rivers and estuaries besides phytoplankton decline such as trends in phytoplankton composition, changes in primary production, ecosystem shifts, cascading effects, changes in ecosystem metabolism, etc., have not been sufficiently monitored and investigated, neither the effects of N:P imbalance. N:P imbalance has significant ecological effects that need to be further investigated. There is a growing number of cases in which phytoplankton biomass have been shown to decrease due to re-oligotrophication, but the potential regime shift from phytoplankton to macrophyte dominance described in shallow lakes has been documented only in a few rivers and estuaries yet. The main reasons why regime shifts are rarely described in rivers and estuaries are, from one hand the scarcity of data on macrophyte cover trends, and from the other hand physical factors such as peak flows or high turbidity that could prevent a general spread of submerged macrophytes as observed in shallow lakes. Moreover, re-oligotrophication effects on rivers may be different compared to lakes (e.g., lower dominance of macrophytes) or estuaries (e.g., limitation of primary production by N instead of P) or may be dependent on river/estuary type. We conclude that river and estuary re-oligotrophication effects are complex, diverse and still little known, and in some cases are equivalent to those described in shallow lakes, but the regime shift is more likely to occur in mid to high-order rivers and shallow estuaries.     

ATP competitive protein kinase C inhibitors demonstrate distinct state-dependent inhibition

We previously reported that some ATP competitive protein kinase C (PKC) inhibitors are either competitive or uncompetitive inhibitors with respect to substrate peptides. In this report, we demonstrate how the interactions between PKC and inhibitors change PKC activation kinetics. A substrate competitive inhibitor, bisindolylmaleimide I, targets activated PKC and stabilizes PKC in the activated conformation. This leads to transient activation and prolonged deactivation of PKC in the presence of bisindolylmaleimide I. In contrast, an uncompetitive substrate inhibitor, bisindolylmaleimide IV, targets quiescent PKC and stabilizes PKC in the quiescent conformation, which generates slower activation and suppressed translocation upon activation of PKC.     

Survival and Adaptation of the Thermophilic Species <Emphasis Type="Italic">Geobacillus thermantarcticus</Emphasis> in Simulated Spatial Conditions

Astrobiology studies the origin and evolution of life on Earth and in the universe. According to the panspermia theory, life on Earth could have emerged from bacterial species transported by meteorites, that were able to adapt and proliferate on our planet. Therefore, the study of extremophiles, i.e. bacterial species able to live in extreme terrestrial environments, can be relevant to Astrobiology studies. In this work we described the ability of the thermophilic species Geobacillus thermantarcticus to survive after exposition to simulated spatial conditions including temperature’s variation, desiccation, X-rays and UVC irradiation. The response to the exposition to the space conditions was assessed at a molecular level by studying the changes in the morphology, the lipid and protein patterns, the nucleic acids. G. thermantarcticus survived to the exposition to all the stressing conditions examined, since it was able to restart cellular growth in comparable levels to control experiments carried out in the optimal growth conditions. Survival was elicited by changing proteins and lipids distribution, and by protecting the DNA’s integrity.