PubMed Health⌕ Search

Biomedical subjects

P Donoso

Publications and source records attributed to P Donoso.

At least 19 recordsLinked to original sources
PubMed2007

Effect of oral administration of dydrogestrone versus vaginal administration of natural micronized progesterone on the secretory transformation of endometrium and luteal endocrine profile in patients with premature ovarian failure: a proof of concept.

BACKGROUND: We aimed to explore the endometrial histology and endocrine profiles on day 21 of an artificial cycle in patients with premature ovarian failure (POF) treated with oral dydrogesterone (DG) or vaginal micronized progesterone. METHODS: The study was designed as a prospective pilot study at an academic reproductive medicine unit. Six POF patients were included in the study. After estrogen endometrial priming, patients were randomized to receive DG or progesterone in two subsequent cycles. The main outcome measure was the endometrial histology and the endocrine profiles on day 21 of the cycle. RESULTS: Development of endometrial glands corresponded to an early secretory phase in five out of six cases supplemented with DG (out-phase). In contrast, five out of six cases treated with micronized progesterone showed an endometrium corresponding to a mid-luteal phase (in-phase) (P = 0.021 versus DG). There was a significant difference in the mean progesterone value [8.6 versus 0.3 microg l(-1) (P = 0.013)], the mean LH value [12.9 versus 22.5 IU l(-1) (P = 0.049)] and the mean FSH value [13.0 versus 23.9 IU l(-1) (P = 0.047)] between the progesterone and DG group, respectively, on day 21 of the cycle. CONCLUSIONS: After estrogen endometrial priming in POF patients, exogenous vaginal micronized progesterone is more effective than oral DG in creating an 'in-phase' secretory endometrium and induces significantly higher progesterone and lower LH and FSH serum concentrations on day 21 of the cycle.

Administration, Intravaginal↗
PubMed2007

Single embryo transfer in preimplantation genetic diagnosis cycles for women <36 years does not reduce delivery rate.

BACKGROUND: The Belgian legislation imposes single embryo transfer (SET) on women of <36 years in their first treatment cycle to avoid multiple pregnancies. The aim of this study is to assess the impact of this legislation on the outcome of preimplantation genetic diagnosis (PGD) for inherited diseases in young women undergoing SET. METHODS: A retrospective analysis of PGD cycles for monogenic disorders and translocations in women <36 years on their first treatment cycle. Two groups of patients were defined according to the implementation of the Belgian legislation: (i) double embryo transfer (DET), January 2001-June 2003 (ii) SET, July 2003-June 2005. The primary and secondary outcome measures were delivery per embryo transfer and multiple pregnancy rates, respectively. A subgroup analysis for monogenic disorders and translocations was performed. RESULTS: 62 cycles were included in the DET group and 73 cycles in the SET group. The mean age, number of cumulus-oocyte complexes, number of fertilized oocytes, number of biopsied and cryopreserved embryos were comparable between both groups. There was no significant difference in the delivery rates between the DET and the SET groups (33.9% versus 27.4%, respectively). Multiple pregnancies were avoided when SET was performed. When monogenic disorders and chromosomal translocations were separately evaluated, no significant difference in the delivery rate after SET was observed. CONCLUSIONS: The implementation of a SET policy in young women undergoing PGD for monogenic disorders and translocations enables a significant reduction of multiple pregnancies without significantly affecting the delivery rate.

Adult↗
PubMed2006

Current value of preimplantation genetic aneuploidy screening in IVF.

Preimplantation genetic aneuploidy screening (PGS) has been performed during the last decade as a way of enhancing embryo selection in patients with an increased incidence of embryonic numerical chromosome abnormalities (advanced maternal age, recurrent miscarriage and recurrent implantation failure). It has been proposed that the replacement of euploid embryos in these patients would result in a higher implantation and pregnancy rate and a reduced miscarriage rate. Additionally, the transfer of fewer embryos could reduce the chances for multiple pregnancies in all IVF patients. Although, to date, multiple studies have addressed this issue, contradictory results have been encountered. As a result, the effectiveness of aneuploidy screening remains to be established. Moreover, child outcome studies documenting the safety of this procedure are needed. The aim of this review is to summarize the available evidence concerning the use of PGS to determine the current value of the technique.

Aneuploidy↗
PubMed2006

Addition of estradiol to progesterone for luteal supplementation in patients stimulated with GnRH antagonist/rFSH for IVF: a randomized controlled trial.

BACKGROUND: The role of progesterone for luteal support in stimulated cycles for IVF is well established. However, controversy still surrounds the benefit of additional supplementation with estradiol (E2) in GnRH agonist (GnRHa) cycles, while no such data are available for GnRH antagonists. The aim of this randomized controlled trial (RCT) was to compare ongoing pregnancy rates in patients stimulated with recombinant FSH (rFSH) and GnRH antagonist for IVF, who received micronized progesterone for luteal phase supplementation, with or without the addition of E2. METHODS: Two hundred and one patients underwent ovarian stimulation with a fixed dose of 200 IU rFSH and GnRH antagonist. Patients were randomized to receive, for luteal phase supplementation, either 600 mg of micronized progesterone vaginally (n=100, progesterone group) or 600 mg of micronized progesterone and 4 mg of E2 valerate orally (n=101, progesterone/E2 group). The main outcome measure was ongoing pregnancy at 12 weeks per patient randomized. RESULTS: Demographics, stimulation parameters and embryological data were comparable for the two groups compared. Twenty-six ongoing pregnancies were achieved in the progesterone (26%) and 30 in the progesterone/E2 group (29.7%). (Difference: 3.7 and 95%, CI: -15.8 to 8.6%). CONCLUSION: It appears that the addition of E2 to progesterone in the luteal phase after stimulation with rFSH and GnRH antagonist does not enhance the probability of pregnancy.

Chorionic Gonadotropin↗
PubMed2006

Does PGD for aneuploidy screening change the selection of embryos derived from testicular sperm extraction in obstructive and non-obstructive azoospermic men?

BACKGROUND: An increased incidence of aneuploid embryos has been recently described from azoospermic men. The aim of this study was to assess if embryo selection on day 5, based on morphological criteria, would be different from the selection based on PGD for aneuploidy screening (AS) in couples undergoing ICSI for male azoospermia. METHODS: Sixty-two cycles of testicular sperm extraction (TESE)-ICSI with PGD-AS were included in the analysis. Two embryologists, blinded to the PGD-AS results, retrospectively reviewed the available embryology data from day 5 embryos and selected one, two or three embryos to be transferred. These results were compared with the selected embryos based on PGD-AS. RESULTS: A total of 39 cycles from non-obstructive azoospermia (NOA) and 23 cycles from obstructive azoospermia (OA) were retrospectively analysed. If single embryo transfer (SET) had been performed, in 64.8% of the NOA cycles and 54.5% of the OA cycles, no difference in embryo choice would have occurred compared to PGD-AS and in 10.8 and 36.6% of the cycles, respectively, an aneuploid embryo would have been chosen. If double ET (DET) had been performed, in 72.9% of the NOA cycles and 86.5% of the OA cycles, no difference in embryo choice would have occurred compared to PGD-AS and in 2.7 and 4.5% of the cycles, respectively, an aneuploid embryo would have been chosen. If triple ET (TET) had been performed, the outcome would have been the same as for DET. DISCUSSION: Our results suggest that under the terms of an SET policy, the performance of PGD-AS in azoospermia would result in a higher chance of success, as the possibility of selecting a euploid embryo is enhanced.

Adult↗
PubMed2002

Sodium transport in triads isolated from rabbit skeletal muscle.

Triads and transverse tubules isolated from mammalian skeletal muscle actively accumulated Na+ in the presence of K+ and Mg-ATP. Active Na+ transport exhibited a fast single-exponential phase, lasting 2 min, followed by slower linear uptake that continued for 10 minutes. Valinomycin stimulated Na+ uptake, suggesting it decreased a pump-generated membrane potential gradient (Vm) that prevented further Na+ accumulation. At the end of the fast uptake phase transverse tubule vesicles incubated in 30 mM external [Na+] attained a ratio [Na+]in/[Na+]out=13.4. From this ratio and the transverse tubule volume of 0.35 microl/mg protein measured in this work, [Na+]in=400 mM was calculated. Determinations of active K+ transport in triads, using 86Rb+ as tracer, showed a 30% decrease in vesicular 86Rb+ content two minutes after initiating the reaction, followed by a slower uptake phase during which vesicles regained their initial 86Rb+ content after 10 minutes. Transverse tubule volume increase during active Na+ transport-as shown by light scattering changes of isolated vesicles--presumably accounted for the secondary Na+ and 86Rb+ uptake phases. These combined results indicate that isolated triads have highly sealed transverse tubules that can be polarized effectively by the Na+ pump through the generation of significant Na+ gradients.

Animals↗
PubMed2000

Sulfhydryl oxidation overrides Mg(2+) inhibition of calcium-induced calcium release in skeletal muscle triads.

We studied the effect of oxidation of sulfhydryl (SH) residues on the inhibition by Mg(2+) of calcium-induced calcium release (CICR) in triad-enriched sarcoplasmic reticulum vesicles isolated from rabbit skeletal muscle. Vesicles were either passively or actively loaded with calcium before eliciting CICR by dilution at pCa 4.6-4.4 in the presence of 1.2 mM free [ATP] and variable free [Mg(2+)]. Native triads exhibited a significant inhibition of CICR by Mg(2+), with a K(0.5) approximately 50 microM. Partial oxidation of vesicles with thimerosal produced a significant increase of release rate constants and initial release rates at all [Mg(2+)] tested (up to 1 mM), and shifted the K(0.5) value for Mg(2+) inhibition to 101 or 137 microM in triads actively or passively loaded with calcium, respectively. Further oxidation of vesicles with thimerosal completely suppressed the inhibitory effect of [Mg(2+)] on CICR, yielding initial rates of CICR of 2 micromol/(mg x s) in the presence of 1 mM free [Mg(2+)]. These effects of oxidation on CICR were fully reversed by SH reducing agents. We propose that oxidation of calcium release channels, by decreasing markedly the affinity of the channel inhibitory site for Mg(2+), makes CICR possible in skeletal muscle.

Adenosine Triphosphate↗
PubMed2000

SH oxidation stimulates calcium release channels (ryanodine receptors) from excitable cells.

The effects of redox reagents on the activity of the intracellular calcium release channels (ryanodine receptors) of skeletal and cardiac muscle, or brain cortex neurons, was examined. In lipid bilayer experiments, oxidizing agents (2,2'-dithiodipyridine or thimerosal) modified the calcium dependence of all single channels studied. After controlled oxidation channels became active at sub microM calcium concentrations and were not inhibited by increasing the calcium concentration to 0.5 mM. Subsequent reduction reversed these effects. Channels purified from amphibian skeletal muscle exhibited the same behavior, indicating that the SH groups responsible for modifying the calcium dependence belong to the channel protein. Parallel experiments that measured calcium release through these channels in sarcoplasmic reticulum vesicles showed that following oxidation, the channels were no longer inhibited by sub mM concentrations of Mg2+. It is proposed that channel redox state controls the high affinity sites responsible for calcium activation as well as the low affinity sites involved in Mg2+ inhibition of channel activity. The possible physiological and pathological implications of these results are discussed.

Animals↗
PubMed1998

Changes in luminal pH caused by calcium release in sarcoplasmic reticulum vesicles.

Fast (milliseconds) Ca2+ release from sarcoplasmic reticulum is an essential step in muscle contraction. To electrically compensate the charge deficit generated by calcium release, concomitant fluxes of other ions are required. In this study we investigated the possible participation of protons as counterions during calcium release. Triad-enriched sarcoplasmic reticulum vesicles, isolated from rabbit fast skeletal muscle, were passively loaded with 1 mM CaCl2 and release was induced at pCa = 5.0 and pH = 7.0 in a stopped-flow fluorimeter. Accompanying changes in vesicular lumen pH were measured with a trapped fluorescent pH indicator (pyranin). Significant acidification (approximately 0.2 pH units) of the lumen occurred within the same time scale (t(1/2) = 0.75 s) as calcium release. Enhancing calcium release with ATP or the ATP analog 5'-adenylylimidodiphosphate (AMPPNP) produced >20-fold faster acidification rates. In contrast, when calcium release induced with calcium with or without AMPPNP was blocked by Mg2+, no acidification of the lumen was observed. In all cases, rate constants of luminal acidification corresponded with reported values of calcium release rate constants. We conclude that proton fluxes account for part (5-10%) of the necessary charge compensation during calcium release. The possible relevance of these findings to the physiology of muscle cells is discussed.

Adenosine Triphosphate↗
PubMed1997

Rapid kinetic studies of SH oxidation-induced calcium release from sarcoplasmic reticulum vesicles.

We studied the kinetics of calcium release induced by SH oxidation in triads isolated from frog and rabbit skeletal muscle by measuring calcium fluxes by a fast filtration method. In both species SH oxidation induced release of 70-80% of the passively loaded calcium with a rate constant of 1 s-1. This rate constant is 3 times higher than the rate constant of calcium-induced calcium release and 15 times lower than the rate constant of ATP-induced release. Calcium release induced by SH oxidation exhibited the same calcium dependence of calcium-induced calcium release and was also inhibited by physiological [MG2+]. Neither SH oxidation-induced calcium release nor calcium-induced calcium release were regulated by luminal calcium. The redox state of thiol groups does not seem to control ATP-induced calcium release since the rate constant of calcium release after SH oxidation was not different from the rate constant measured in the presence of the reducing agent dithiothreitol. Our results do not support a role for SH oxidation, per se, as an essential step for the release of calcium from sarcoplasmic reticulum.

2,2'-Dipyridyl↗
PubMed1996

Luminal pH regulated calcium release kinetics in sarcoplasmic reticulum vesicles.

Calcium binding to triads isolated from rabbit skeletal muscle followed a single hyperbolic function in the pH range 5.5-8.0. Maximal binding was obtained at pH 8.0; decreasing the pH decreased the binding capacity and, at pH < or = 6.0, increased Kd 2-fold. These results indicate that lowering the pH diminished calcium binding to calsequestrin, since this protein is the primary source of calcium binding sites in triads. Luminal pH had a marked effect on calcium release induced by 2 mM ATP, at pCa 5.0, pH 6.8. At a constant luminal [Ca2+] of 0.1 mM, release rate constants (k) and initial rates of release increased steadily as a function of decreasing luminal pH; at luminal pH 7.5, values of k < 0.4 s-1 were found, whereas at pH 5.5 values of k approximately 10 S-1 were obtained. Increasing luminal [Ca2+] from 0.05 mM to 0.7 mM had no effect on the k values measured at luminal pH 5.5. In contrast, at pH 6.8, increasing luminal [Ca2+] produced a marked increase in k values, that reached maximal values of k approximately 10 S-1 at 0.7 mM luminal [Ca2+]. Control experiments using fluorescent pH indicators showed that luminal pH did not change significantly during calcium release. It is proposed that luminal protons or calcium induces conformational changes in calsequestrin that in turn promote activation of the calcium release channels.

Animals↗
PubMed1996

Protons induce calsequestrin conformational changes.

Calsequestrin, a high-capacity, intermediate-affinity, calcium-binding protein present in the lumen of sarcoplasmic reticulum, undergoes extensive calcium-induced conformational changes at neutral pH that cause distinct intrinsic fluorescence changes. The results reported in this work indicate that pH has a marked effect on these calcium-induced intrinsic fluorescence changes, as well as on calorimetric changes produced by the addition of Ca(2+) to calsequestrin. The addition of Ca(2+) at neutral pH produced a marked and cooperative increase in calsequestrin intrinsic fluorescence. In contrast, at pH 6.0 calsequestrin's intrinsic fluorescence was not affected by the addition of Ca(2+), and the same intrinsic fluorescence as that measured in millimolar calcium at neutral pH was obtained. The magnitude and the cooperativity of the calcium-induced intrinsic fluorescence changes decreased as either [H+] or [K+] increased. The evolution of heat production, determined by microcalorimetry, observed upon increasing the molar ratio of Ca(2+) to calsequestrin in 0.15 M KCl, decreased markedly as the pH decreased from pH 8.0 to pH 6.0, indicating that pH modifies the total heat content changes produced by Ca(2+). We propose that protons bind to calsequestrin and induce protein conformational changes that are responsible for the observed proton-induced intrinsic fluorescence and calorimetric changes.

Animals↗
PubMed1996

Ca(2+)- and pH-dependent halothane stimulation of Ca2+ release in sarcoplasmic reticulum from frog muscle.

The effect of halothane on calcium release kinetics was studied in triad-enriched sarcoplasmic reticulum vesicles from frog skeletal muscle. Release from vesicles passively equilibrated with 3 mM 45CaCl2 was measured in the millisecond time range by use of a fast-filtration system. Halothane (400 microM) increased release rate constants at pH 7.1 and 7.4 as a function of extravesicular pCa. In contrast, halothane at pH 6.8 produced the same stimulation of release from pCa 7.0 to 3.0; no release took place in these conditions in the absence of halothane. Halothane shifted the calcium activation curve at pH 7.1, but not at pH 7.4, to the left and increased channel open probability at pH 7.1 in the cis pCa range of 7.0 to 5.0. These results indicate that cytosolic pCa and pH modulate the stimulatory effects of halothane on calcium release. Furthermore, halothane stimulated release in frog skeletal muscle at low pH and resting calcium concentration, indicating that in frog muscle halothane can override the closing of the release channels produced by these conditions, as it does in malignant hyperthermia-susceptible porcine muscle.

Animals↗
PubMed1995

Luminal calcium regulation of calcium release from sarcoplasmic reticulum.

This article discusses how changes in luminal calcium concentration affect calcium release rates from triad-enriched sarcoplasmic reticulum vesicles, as well as single channel opening probability of the ryanodine receptor/calcium release channels incorporated in bilayers. The possible participation of calsequestrin, or of other luminal proteins of sarcoplasmic reticulum in this regulation is addressed. A comparison with the regulation by luminal calcium of calcium release mediated by the inositol 1,4,5-trisphosphate receptor/calcium channel is presented as well.

Animals↗
PubMed1995

Luminal calcium regulates calcium release in triads isolated from frog and rabbit skeletal muscle.

Triads isolated from frog and rabbit skeletal muscle were equilibrated with different external [Ca2+], ranging from 0.025 to 10 mM. Vesicular calcium increased with external [Ca2+] as the sum of a linear plus a saturable component; the latter, which vanished after calsequestrin removal, displayed Bmax values of 182 and 132 nmol of calcium/mg of protein, with Kd values of 1.21 and 1.14 mM in frog and rabbit vesicles, respectively. The effect of luminal [Ca2+] on release kinetics in triads from frog and rabbit skeletal muscle was investigated, triggering release with 2 mM ATP, pCa 5, pH 6.8. In triads from frog, release rate constant (k) values increased sixfold after increasing luminal [Ca2+] from 0.025 to 3 mM. In triads from rabbit, k values increased 20-fold when luminal [Ca2+] increased from 0.05 to 0.7 mM. In both preparations, k values remained relatively constant (10-12 s-1) at higher luminal [Ca2+], with a small decrease at 10 mM. Initial release rates increased with luminal [Ca2+] in both preparations; in triads from rabbit the increase was hyperbolic, and in triads from frogs the increase was sigmoidal. These results indicate that, although triads from frog and rabbit respond differently, in both preparations luminal [Ca2+] has a distinctive effect on release, presumably by regulating sarcoplasmic reticulum calcium channels.

Animals↗
PubMed1994

Comparison of the effects of caffeine and other methylxanthines on [Ca2+]i in rat ventricular myocytes.

1. The effects of caffeine and other methylxanthines were investigated on intracellular calcium concentration ([Ca2+]i) and contraction in rat isolated ventricular myocytes. The use of the fluorescent indicator, Indo-1, allowed simultaneous measurement of [Ca2+]i and the intracellular concentration of the methylxanthines. 2. Rapid application of caffeine (10 mM) produced a transient rise of [Ca2+]i which decayed to resting levels. This was accompanied by a transient contraction which decayed to a level above baseline. The addition of theophylline also produced a transient increase of [Ca2+]i. However, following the initial transient, contraction decayed before redeveloping to a maintained level. 3. Direct measurements showed that [caffeine]i rose more quickly than did [theophylline]i. The slower rise of [theophylline]i was associated with a delay in the increase of [Ca2+]i. At lower concentrations of the methylxanthines, theophylline was less effective than caffeine at initiating Ca release. The rate of entry of theobromine was similar to that of theophylline. 4. Isocaffeine did not produce a rise of [Ca2+]i. The rate of rise of [isocaffeine]i was much slower than that of either caffeine or theophylline. 5. Measurements of the oil:water partition coefficient showed that the order of relative partitioning into oil was: caffeine > theophylline > theobromine > isocaffeine. This is similar to the order of rate of entry into the cell. 6. We conclude that many of the differences in the effects of these methylxanthines can be attributed to differences in membrane permeability due to differences in oil:water partition.

Animals↗
PubMed1994

[Anemia associated with acute post streptococcal glomerulonephritis].

Thirty-three children with post-streptococcal acute glomerulonephritis, age mean: 8.3 years (range: 6 - 12) were studied prospectively. Mean initial hematocrit (Hct) was 31.6% with 90% showing Hct under the normal lower limit for this age group. Reticulocyte index (RI) was < 0.5 in half of the cases. Serum iron concentration, total iron binding capacity (TIBC) and percentage of transferrin saturation were normal for this age group although 75% of the children had increased serum ferritin levels. At the time of discharge, Hct increased to 35.1% but 44% still had anemia. Hct increased spontaneously for 105 days stabilizing at 38%. Based on Hct changes, 3 groups were defined: Group I (3 individuals): normal upon discharge; Group II (19): partial recovery at discharge, slow recovery stabilizing after 105 days; Group III (11): lower Hct, slower recovery but with RI significantly higher than group II (0.96 vs 0.45 p < 0.01). Our data suggest that although hemodilution is present in all, it may be considered the solely factor only in 3 cases (Group I). In group II, evidence of bone marrow depression was indicated by the low RI. On the other hand, the intense anemia that could not be justified only by hemodilution and marrow depression in group III, suggests other pathogenic factors.

Acute Disease↗