Calcium uptake during the cell cycle of Saccharomyces cerevisiae.

Synchronous culture of the budding yeast Saccharomyces cerevisiae was obtained by sucrose density gradient selection with 90-100% of yeast synchronized by using the cells in the bottom. In these adult cells bud emergence is coincident with an increase in calcium uptake at 100 min of the culture, followed by a return to basal values which are maintained until the end of the first cell cycle of study. The phenothiazine derivatives, trifluoperazine and chlorpromazine inhibit bud emergence and trifluoperazine also increases calcium uptake.

Prevalencia y características clínicas de la apnea del sueño en una población de mujeres diagnosticadas de cáncer de mama / Prevalence and clinical characteristics of sleep apnea in a population of women diagnosed with breast cancer

Objetivo: a pesar del interés creciente en la asociación entre apnea de sueño (AS) y cáncer, apenas existen estudios que investiguen tumores concretos. Nuestro objetivo fue analizar la prevalencia y características clínicas de la AS en mujeres con cáncer de mama (CM). Métodos: estudio piloto transversal. Se incluyen consecutivamente 83 mujeres entre 18 - 65, años diagnosticadas por primera vez de CM. En todos los casos se realizó un cuestionario clínico y una poligrafía respiratoria domiciliaria. La AS se definió como un índice de apneas-hipopneas (IAH) ≥5, y el síndrome de apneas-hipopneas del sueño (SAHS) como la asociación de un IAH ≥5 y excesiva somnolencia diurna (ESD, Epworth >10). Resultados: la media (DE) de edad fue de 48,8 (8,8) años, el índice de masa corporal (IMC) de 27,4 (5,4) y el 50,6% eran postmenopáusicas. La prevalencia de AS fue del 51,8% (43 casos), y la mediana de IAH de 5,1 (RIQ 2 - 9,4). De las 43 pacientes con AS, 32 presentaron un IAH 5 - 14,9 y 11 IAH ≥15. La prevalencia de SAHS fue del 10,8% (9 casos). Comparadas con las mujeres sin AS, aquellas con AS presentaron más ronquido, pero no hubo diferencias en otros síntomas relacionados con el sueño. En el análisis multivariado, la edad y las variables antropométricas, pero no la ESD, se asociaron independientemente a la AS. Conclusión: la prevalencia de AS es elevada en mujeres de mediana edad diagnosticadas de CM, aunque la mayoría no presentan ESD ni otras características diferenciales. La edad y la obesidad fueron predictores de AS en esta población

Objective: Despite growing interest in the association between sleep apnea and cancer, there are hardly any studies that research specific tumors. Our objective was to analyze the prevalence and characteristics of sleep apnea in women with breast cancer. Methods: A transversal pilot study. 83 women between the ages of 18 and 65 diagnosed with breast cancer for the first time were included consecutively. All participants completed a clinical questionnaire and underwent home respiratory polygraphy. Sleep apnea was defined as an apnea-hypopnea index (AHI) ≥5 and sleep apnea-hypopnea syndrome (SAHS) was defined as the association between an AHI ≥5 and excessive daytime sleepiness (EDS, Epworth >10). Results: The average (SD) age was 48.8 (8.8) years old, the body mass index (BMI) was 27.4 (5.4) and 50.6% were postmenopausal. The prevalence of sleep apnea was 51.8% (43 cases) and the average AHI was 5.1 (IQR: 2 - 9.4). Of the 43 patients with sleep apnea, 32 had an AHI between 5 and 14 and 11 had an AHI ≥15. The prevalence of SAHS was 10.8% (9 cases). Compared to women without sleep apnea, those with the disease snored more, but there were no differences in other sleep-related symptoms. In the multivariate analysis, age and anthropometric variables, but not EDS, were independently associated with sleep apnea. Conclusion: The prevalence of sleep apnea is higher in middle-aged women diagnosed with breast cancer, although the majority do not present with EDS or other distinguishing characteristics. Age and obesity were predictors for sleep apnea in this population

Some characteristics of Ca2+ uptake by yeast cells.

Experiments were performed to obtain information on: (i) the specific properties of Ca2+ binding and transport in yeast; (ii) the relationship between both parameters; (iii) similarities to or differences from other biological systems as measured by the effects of inhibitors; and (iv) the effects of mono and divalent cations, in order to get some insight on the specificity and some characteristics of the mechanism of the transport system for divalent cations in yeast. The results obtained gave some kinetic parameters for a high affinity system involved in the transport of Ca2+ in yeast. These were obtained mainly by considering actual concentrations of Ca2+ in the medium after substracting the amounts bound to the cell. A km of 1.9 microM and a Vmax of 1.2 nmol (100 mg.3 min)-1 were calculated. The effects of some inhibitors and other cations on Ca2+ uptake allow one to postulate some independence between binding and transport for this divalent cation. Of the inhibitors tested, only lanthanum seems to be a potent inhibitor of Ca2+ uptake in yeast. The effects of Mg2+ on the uptake of Ca2+ agree with the existence of a single transport system for both divalent cations. The actions of Na+ and K+ on the transport of Ca2+ offer interesting possibilities to study further some of the mechanistic properties of this transport system for divalent cations.

Energetics of sodium efflux from Escherichia coli.

When energy-starved cells of Escherichia coli were passively loaded with 22Na+, efflux of sodium could be initiated by addition of a source of metabolic energy. Conditions were established where the source of energy was phosphate bond energy, an electrochemical proton gradient, or both. Only an electrochemical proton gradient was required for efflux from intact cells. These results are consistent with secondary exchange of Na+ for H+ catalyzed by a sodium/proton antiporter.

A plasmid-encoded arsenite pump produces arsenite resistance in Escherichia coli.

The arsenate resistance operon of R-factor R773, a conjugative resistance plasmid, has two functional regions, a promoter-proximal region encoding resistance to arsenite and antimonate, and a promoter-distal one encoding arsenate resistance. Cells bearing arsenite resistance plasmids exhibited reduced accumulation of 74AsO2-. When resistant cells were depleted of endogenous energy reserves and then loaded with 74AsO2-, active extrusion of the ion was observed when an energy source was supplied. Intracellular ATP was required for extrusion, but a proton motive force was neither necessary nor sufficient. An arsenite-sensitive mutant was unable to extrude arsenite, while an arsenate-sensitive mutant had normal arsenite transport. These results suggest that the action of a plasmid-encoded primary arsenite efflux pump is the mechanism of arsenite resistance.

The use of a cyanine dye in measuring membrane potential in yeast.

An attempt was made to use 3,3'-dipropylthiacarbocyanine as a membrane potential probe in yeast by following both its fluorescence changes and its uptake by the cells under different conditions. It was found that the uptake of the dye into the cytoplasmic compartment was translated into an increased fluorescence, and the uptake by the mitochondria produced a quenching of the fluorescence. The experiments to measure uptake showed that a large amount of the dye was taken up by the cells under "deenergized" conditions. The uptake of the cyanine, however, was significantly reduced by the omission of the substrate, by deenergization of the mitochondria, or by the addition of K+, but not by Na+. This cyanine seems to be a good, qualitative indicator of the potential of the plasma membrane and of the mitochondria of the cells, with a faster response than those probes used before in yeast.