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J Pavelková

Publications and source records attributed to J Pavelková.

9 recordsLinked to original sources
PubMed2001

[Evaluation of success in assisted reproduction].

OBJECTIVE: Summarize different ways of assisted reproduction performance evaluation. DESIGN: Review. SETTING: Centre for Assisted Reproduction, Department of Gynaecology and Obstetrics, 1st Faculty of Medicine, Charles University, Prague. METHODS: In databases of assisted reproduction centres, in national and international registers we evaluate data concerning in vitro fertilisation and related methods. Target of this evaluation is, first of all, to increase efficiency. RESULTS: Outputs of all the registers inform about absolute numbers of cycles, deliveries, born babies and about relative parameters (implantation rate, pregnancy rate), describing the efficiency of the treatment. CONCLUSION: The output evaluation must consider the influence of the age of female, number of transferred embryos and other factors.

Czech Republic↗
PubMed2000

[Treatment of infertility using oocytes without the zona pellucida].

OBJECTIVE: The study of zona free oocytes fertilization using intracytoplasmic sperm injection (ICSI) with the aim to increase the pregnancy rate in the assisted reproduction. DESIGN: Pilot study. SETTING: Assisted Reproduction Centre, Gynecology Obstetrics Department of the 1st Medical Faculty and General Faculty Hospital, Charles University, Prague. METHODS: Zona free oocytes were fertilized using ICSI and cultured in standard conditions in vitro for 5 days until the blastocyst stage. Blastocysts were cryopreserved using 8% glycerol. RESULTS: The fertilization process of zona free oocyte was physiological, oocytes expulsed the polar body and in standard time, i.e. 18 hour post insemination, two distinct, morphologically normal pronuclei were apparent in cytoplasm. During early cleavage, from the first to the third day of in vitro culture, the dynamics of cell division was normal, the three-dimensional arrangement of cells was more flattened than in normal, zona intact embryo. The fourth and fifth day of culture, the morphological appearance of embryo corresponded to normal development. CONCLUSION: The fertilization of zona free oocytes using ICSI can give morphologically normal zygote and after 5 days culture in vitro these zygotes can develop into blastocyst stage. This method can increase the pregnancy rate in patients with repeatedly low number of oocytes or with defects of zona pellucida.

Adult↗
PubMed1993

Characterization of tension decline in different types of fatigue-resistant skeletal muscle fibres of the frog. Low extracellular calcium effects.

Twitch and tetanic tension have been measured in single skeletal muscle fibres (m.ileofibularis, Rana esculenta and Rana temporaria). On the basis of resistance to fatigue produced by repetitive tetanic stable frequency stimulation with various numbers of stimulation trains, twitch fibers were subdivided in three groups (resembling those as described by Westerblad and Lännergren 1986 in Xenopus), that is fatigue-resistant (FR), moderately fatigued (MF) and easily fatiguing (EF). It was found further that the fibres differ in tetanic tension decline resistance i.e. fatiguability relating to some basic contractile parameters including the amplitude, the rates parameters of twitch and tetanus tension as well as the tetanus/twitch tension ratio. The main differences observed concern: 1) The inability to maintain the maximum tetanic tension plateau (IMT) during single tetanus. IMT was 18 times higher in EF fibres and 4 times higher in MF fibres, respectively, in comparison with FR fibres. IMT is the first parameter to change significantly during repetitive tetanic stimulation. 2) The different fibre types show pronounced differences in twitch contraction and tetanus tension during repetitive tetanic stimulation. There is a conspicuous facilitation of twitch tension during and after cessation of repetitive stimulation in FR fibres; the MF and EF fibres show, on the contrary, a depression of twitches. 3) Recovery to original (prefatigue) values is rapid in FR fibres, but slow, however, in EF fibres. 4) Removal of extracellular Ca2+ intensified the inability to maintain the maximum tetanic tension (IMT) and the tetanic tension decline, especially in fibres with an initial high fatigue-resistance. We assume that the results might be explained by a different refractoriness of transmission between the T-tubules and the sarcoplasmic reticulum in examined fibres and/or by a different dependency of the T-SR transmission on the extracellular calcium ions. A possible cause of the failure may be an intensification of the inactivation process.

Animals↗
PubMed1993

The effect of Pb2+ ions on calcium currents and contractility in single muscle fibres of the crayfish.

Muscle fibres of crustaceans represent an useful model for studying the mode of action of substances influencing calcium channels as the membrane generates the active responses on a pure calcium principle and the excitation-contraction link is dependent on external calcium. We followed the effect of Pb2+ ions (1-300 mumol/l) on contractile responses in single muscle fibres of the crayfish evoked by massive or intracellular electrical stimulation, by potassium depolarization and caffeine application, as well as on action potential in single intact muscle fibres and on calcium currents in voltage clamp conditions (vaseline gap) in internally perfused muscle fibre segments. All types of contractile responses, single twitches, tetanus, potassium and caffeine contractures were blocked. The strontium action potential was blocked very effectively by Pb2+ ions. The total calcium currents which can be split by means of Hodgkin-Huxley equations into two components (fast and slow respectively) differing in the rate of activation and inactivation were suppressed after addition of Pb(NO3)2 (50-300 mumol/l). The effect of Pb2+ was concentration and time dependent. At lower concentrations (100 mumol/l) the blocking effect was more pronounced on the fast inactivating Ca current component. The Pb2+ ions prolonged the time constant of inactivation tau h of the slow channel, while leaving that of the fast channel intact.

Action Potentials↗
PubMed1990

Effects of local anesthetics on mechanical characteristics of lipid bilayers and on the ion transport dynamics.

Bilayer lipid membranes (BLM) of various composition were used to study the effects of local anesthetics (LA) carbisocaine and lidocaine on mechanical membrane characteristics and on the transport dynamics of ions across gramicidin D ionic channels. Carbisocaine concentrations of 20 mumols/l-0.1 mmol/l caused a considerable decrease (by 15-40%) in modulus of elasticity E1 in direction perpendicular to membrane surface. The effect of lidocaine was approx. one order of magnitude weaker. LA-induced changes in E1 were shown to depend on both the lipid composition of the membrane and the electrolyte pH. Neutral forms of LA induce marked changes in E1. An analysis of current-voltage (I-V) characteristics of BLM modified by the channel forming agent gramicidin D revealed that carbisocaine significantly affects the superlinear segment of the I-V relationship; this suggests a strong effect on the transport dynamics of ions through the internal channel region. The results of the study suggest that the action of both carbisocaine and lidocaine may be non-specific. The effectivity of the non-specific action of LA is determined by the hydrophobic moiety of the local anesthetic molecule.

Anesthetics, Local↗
PubMed1990

Effects of ruthenium red on excitation and contraction in muscle fibres with Ca2+ electrogenesis.

The effect of ruthenium red (RR) on the electrical and contractile responses, membrane Ca currents, staining patterns of the external and internal membrane system were tested in intact and mechanically skinned muscle fibres of the crayfish Astacus fluviatilis. The following results were obtained: 1. Depression of the contractile responses following membrane depolarization (twitch, tetanus, potassium contractures). 2. Caffeine contractures were unaffected in intact (100 mumol/l - 1 mmol/l RR) and blocked in skinned fibres (30 mumol/l RR). 3. Mechanical threshold and mechanical latency were increased and/or prolonged. 4. The rate of depolarization of the action potentials (AP) was decreased and decremental spread of AP was recorded. 5. Both fast and slowly inactivating Ca ionic currents were decreased and the time constants of activation (tau(m] and inactivation (tau(h] were prolonged after RR (100 mumol/l) pretreatment. 6. The penetration of RR into the T-system was inversely related to its binding to the sarcolemma. The depression of depolarization-induced contractions was most pronounced in fibres with unstained sarcolemma and stained T-tubules. In intact fibres, neither terminal cisternae nor other elements of SR were stained. On the contrary, all internal membrane structures were stained in skinned fibres. There was a gradient of staining intensity from surface toward the interior.

Animals↗