ABSTRACTAlthough mice are a very instrumental model in islet beta cell research, possible phenoty... more ABSTRACTAlthough mice are a very instrumental model in islet beta cell research, possible phenotypic differences between strains and substrains are largely neglected in the scientific community. In this study, we show important phenotypic differences in beta cell responses to glucose between NMRI, C57BL/6J, and C57BL/6N mice, i.e., the three most commonly used strains. High-resolution multicellular confocal imaging of beta cells in acute pancreas tissue slices was used to measure and quantitatively compare the calcium dynamics in response to a wide range of glucose concentrations. Strain- and substrain-specific features were found in all three phases of beta cell responses to glucose: a shift in the dose-response curve characterizing the delay to activation and deactivation in response to stimulus onset and termination, respectively, and distinct concentration-encoding principles during the plateau phase in terms of frequency, duration, and active time changes with increasing glucos...
Network science has provided new promising tools for studying the structure and function of vario... more Network science has provided new promising tools for studying the structure and function of various complex systems. In the present contribution we demonstrate how network concepts can be used to describe the collective activity of pancreatic β cell populations in islets of Langerhans. In this microorgan, electrically coupled β cells produce and secrete insulin that plays a pivotal role in normal and pathological whole-body nutrient homeostasis. We construct functional networks from correlations between calcium dynamics of individual cells, which is recorded by means of confocal laser-scanning calcium imaging. The extracted connectivity patterns share many similarities with other real-life networks, such as small-worldness, heterogeneity, and modularity. Moreover, by applying the multilayer network formalism, we give particular emphasis to the dynamical evolution of the β cell network after stimulation. By this means, an even deeper insight into the intercellular communication mechanisms in islets is attained.
DOAJ (DOAJ: Directory of Open Access Journals), Sep 1, 2007
Background: The selection of embryos with largest implantation potential is an important part in ... more Background: The selection of embryos with largest implantation potential is an important part in assisted reproduction. Besides the embryo or blastocyst morphology, selection criteria such as position and orientation of pronuclei (PN) in relation to polar body positioning and the number, size and distribution of nucleolar precursor bodies (NPB) have been proposed. In our study, a correlation between PN and NBP morphology with the development of early embryos (day 2 of cultivation) and blastocysts (day 5) was investigated. Methods: 653 zygotes from 113 IVF (in vitro fertilization) and ICSI (intracytoplasmic sperm injection) patients, younger than 40 years, were assessed 18–20 hours post-insemination. Optimal zygotes (Z1) had thouching centrally located PN with equall numbers of alligned NPB. Other zygote types differred from Z1 in having scattered NPB in both PN (Z2) or alligned NPB in one PN (Z3) or in PN beeing distant from one another (Z4). For each zygote type a percentage of normal early embryos and blastocysts was calculated. Results: Among 653 assessed zygotes 21.8 % were Z1; 29.1 % Z2, 34.6 % Z3 and 14.5 % Z4. The percentage of normal early embryos decreased from Z1 to Z4 zygote type (70.4 % vs. 55.3 % vs. 59.7 % vs.45.3 %; p < 0.05) as well as the percentage of developed blastocysts (63.4 % vs. 55.3 % vs. 58.8 % vs. 43.2 %). However, the percentages of optimal blastocysts in the four groups did not differ (11.3 % vs. 11.1 % vs. 8.4 % vs. 6.3 %). Conclusions: Best grade zygotes result in batter early embryo and blastocyst development suggesting that zygote morphology can be used in combination with embryo and/or blastocyst evaluation as a method for embryo selection prior to embryo transfer.
American Journal of Physiology-endocrinology and Metabolism, 2023
The release of peptide hormones is predominantly regulated by a transient increase in cytosolic C... more The release of peptide hormones is predominantly regulated by a transient increase in cytosolic Ca2+ concentration ([Ca2+]c). To trigger exocytosis, Ca2+ ions enter the cytosol from intracellular Ca2+ stores or from the extracellular space. The molecular events of late stages of exocytosis, and their dependence on [Ca2+]c, were extensively described in isolated single cells from various endocrine glands. Notably, less work has been done on endocrine cells in situ to address the heterogeneity of [Ca2+]c events contributing to a collective functional response of a gland. For this, β cell collectives in a pancreatic islet are particularly well suited as they are the smallest, experimentally manageable functional unit, where [Ca2+]c dynamics can be simultaneously assessed on both cellular and collective level. Here, we measured [Ca2+]c transients across all relevant timescales, from a subsecond to a minute time range, using high-resolution imaging with a low-affinity Ca2+ sensor. We quantified the recordings with a novel computational framework for automatic image segmentation and [Ca2+]c event identification. Our results demonstrate that under physiological conditions the duration of [Ca2+]c events is variable, and segregated into three reproducible modes, subsecond, second, and tens of seconds time range, and are a result of a progressive temporal summation of the shortest events. Using pharmacological tools we show that activation of intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in β cell collectives, and that a subset of [Ca2+]c events could be triggered even in the absence of Ca2+ influx across the plasma membrane. In aggregate, our experimental and analytical platform was able to readily address the involvement of intracellular Ca2+ receptors in shaping the heterogeneity of [Ca2+]c responses in collectives of endocrine cells in situ.NEW & NOTEWORTHY Physiological glucose or ryanodine stimulation of β cell collectives generates a large number of [Ca2+]c events, which can be rapidly assessed with our newly developed automatic image segmentation and [Ca2+]c event identification pipeline. The event durations segregate into three reproducible modes produced by a progressive temporal summation. Using pharmacological tools, we show that activation of ryanodine intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in β cell collectives.
European Journal of Obstetrics & Gynecology and Reproductive Biology, Oct 1, 2007
To evaluate the rate and type of aneuploidies of chromosomes 13, 16, 18, 21 and 22, with respect ... more To evaluate the rate and type of aneuploidies of chromosomes 13, 16, 18, 21 and 22, with respect to the length of in vitro maturation (IVM) period, and to compare the results to previously published studies on aneuploidy rates of unfertilized, uninseminated mature oocytes and first polar bodies. Two hundred and twelve immature germinal vesicle stage oocytes were assigned to two groups. After successful IVM, depending on their maturational period of 24h (Group A) or 36h (Group B), chromosomal analysis was performed by five color fluorescence in situ hybridization (FISH). In Groups A and B the rates of aneuploid oocytes were calculated and compared by chi-square test. Also the rates of hyperhaploidy, hypohaploidy, disomy and nullisomy were determined and compared by chi-square test. The difference was considered statistically significant at p-value of &amp;amp;amp;amp;amp;amp;lt;0.05. The prolonged IVM did not significantly affect the aneuploidy rate compared to the shorter maturation period (48.1% and 45.0%, respectively). Regarding the unbalanced premature chromatid separation, no statistically significant difference was found between hyperhaploidy and hypohaploidy (14.8% versus 8.3%). For chromosome nondisjunction, higher frequency of disomy than nullisomy was observed (30.6% versus 14.8%; p&amp;amp;amp;amp;amp;amp;lt;0.05). The estimated global aneuploidy rate was between 42% and 63%. The aneuploidy rate of IVM GV-oocytes is comparable to the aneuploidy rate of in vivo matured oocytes and first polar bodies, regardless of the length of maturation period. This suggests that the immature oocytes can be used in infertility treatment after they complete maturation.
Knjiga Izbrana poglavja iz fiziologije za študente medicine z navodili za vaje so strukturirana t... more Knjiga Izbrana poglavja iz fiziologije za študente medicine z navodili za vaje so strukturirana tako, da študent skozi prvi dve poglavji osvoji fiziologijo vzdražnih celic. Sledijo poglavja, ki obravnavajo fiziologijo nekaterih notranjih organov. Več poglavij je namenjenih kardiovaskularni fiziologiji, kjer študent usvoji koncepte arterijskega pritiska, načine merjenja električne aktivnosti srca z elektrokardiografijo ter dejavnike in spremembe minutnega volumna srca. Zadnja tri poglavja postavijo posamezne organe v kontekst celotnega telesa. V njih se študent seznani z delovanjem organov v medsebojni interakciji ter odzivom telesa na različne zunanje stresorje. V vsakem poglavju so podani primeri različnih patoloških stanj, ki so primerni za poglobljen študij obravnavane tematike in predstavljajo uvod v klinične predmete na študiju medicine. Teoretičnemu delu vsakega poglavja sledi navodilo za izvedbo praktične vaje, s pomočjo katerega lahko študent samostojno ali ob pomoči kolegov izvede meritve, jih analizira in tako poglablja svoje znanje.
Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterize... more Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterized by structural changes involving sarcomere, cytoskeletal, and membrane damage, with an increased permeability of sarcolemma for proteins. From a functional point of view, disrupted force transmission, altered calcium homeostasis, disruption of excitation-contraction coupling, as well as metabolic changes bring about loss of strength. Importantly, the trauma also invokes an inflammatory response and clinically presents itself by swelling, decreased range of motion, increased passive tension, soreness, and a transient decrease in insulin sensitivity. While being damaging and influencing heavily the ability to perform repeated bouts of exercise, changes produced by exercise-induced muscle damage seem to play a crucial role in myofibrillar adaptation. Additionally, eccentric exercise yields greater hypertrophy than isometric or concentric contractions and requires less in terms of metabolic...
ABSTRACTAlthough mice are a very instrumental model in islet beta cell research, possible phenoty... more ABSTRACTAlthough mice are a very instrumental model in islet beta cell research, possible phenotypic differences between strains and substrains are largely neglected in the scientific community. In this study, we show important phenotypic differences in beta cell responses to glucose between NMRI, C57BL/6J, and C57BL/6N mice, i.e., the three most commonly used strains. High-resolution multicellular confocal imaging of beta cells in acute pancreas tissue slices was used to measure and quantitatively compare the calcium dynamics in response to a wide range of glucose concentrations. Strain- and substrain-specific features were found in all three phases of beta cell responses to glucose: a shift in the dose-response curve characterizing the delay to activation and deactivation in response to stimulus onset and termination, respectively, and distinct concentration-encoding principles during the plateau phase in terms of frequency, duration, and active time changes with increasing glucos...
Network science has provided new promising tools for studying the structure and function of vario... more Network science has provided new promising tools for studying the structure and function of various complex systems. In the present contribution we demonstrate how network concepts can be used to describe the collective activity of pancreatic β cell populations in islets of Langerhans. In this microorgan, electrically coupled β cells produce and secrete insulin that plays a pivotal role in normal and pathological whole-body nutrient homeostasis. We construct functional networks from correlations between calcium dynamics of individual cells, which is recorded by means of confocal laser-scanning calcium imaging. The extracted connectivity patterns share many similarities with other real-life networks, such as small-worldness, heterogeneity, and modularity. Moreover, by applying the multilayer network formalism, we give particular emphasis to the dynamical evolution of the β cell network after stimulation. By this means, an even deeper insight into the intercellular communication mechanisms in islets is attained.
DOAJ (DOAJ: Directory of Open Access Journals), Sep 1, 2007
Background: The selection of embryos with largest implantation potential is an important part in ... more Background: The selection of embryos with largest implantation potential is an important part in assisted reproduction. Besides the embryo or blastocyst morphology, selection criteria such as position and orientation of pronuclei (PN) in relation to polar body positioning and the number, size and distribution of nucleolar precursor bodies (NPB) have been proposed. In our study, a correlation between PN and NBP morphology with the development of early embryos (day 2 of cultivation) and blastocysts (day 5) was investigated. Methods: 653 zygotes from 113 IVF (in vitro fertilization) and ICSI (intracytoplasmic sperm injection) patients, younger than 40 years, were assessed 18–20 hours post-insemination. Optimal zygotes (Z1) had thouching centrally located PN with equall numbers of alligned NPB. Other zygote types differred from Z1 in having scattered NPB in both PN (Z2) or alligned NPB in one PN (Z3) or in PN beeing distant from one another (Z4). For each zygote type a percentage of normal early embryos and blastocysts was calculated. Results: Among 653 assessed zygotes 21.8 % were Z1; 29.1 % Z2, 34.6 % Z3 and 14.5 % Z4. The percentage of normal early embryos decreased from Z1 to Z4 zygote type (70.4 % vs. 55.3 % vs. 59.7 % vs.45.3 %; p < 0.05) as well as the percentage of developed blastocysts (63.4 % vs. 55.3 % vs. 58.8 % vs. 43.2 %). However, the percentages of optimal blastocysts in the four groups did not differ (11.3 % vs. 11.1 % vs. 8.4 % vs. 6.3 %). Conclusions: Best grade zygotes result in batter early embryo and blastocyst development suggesting that zygote morphology can be used in combination with embryo and/or blastocyst evaluation as a method for embryo selection prior to embryo transfer.
American Journal of Physiology-endocrinology and Metabolism, 2023
The release of peptide hormones is predominantly regulated by a transient increase in cytosolic C... more The release of peptide hormones is predominantly regulated by a transient increase in cytosolic Ca2+ concentration ([Ca2+]c). To trigger exocytosis, Ca2+ ions enter the cytosol from intracellular Ca2+ stores or from the extracellular space. The molecular events of late stages of exocytosis, and their dependence on [Ca2+]c, were extensively described in isolated single cells from various endocrine glands. Notably, less work has been done on endocrine cells in situ to address the heterogeneity of [Ca2+]c events contributing to a collective functional response of a gland. For this, β cell collectives in a pancreatic islet are particularly well suited as they are the smallest, experimentally manageable functional unit, where [Ca2+]c dynamics can be simultaneously assessed on both cellular and collective level. Here, we measured [Ca2+]c transients across all relevant timescales, from a subsecond to a minute time range, using high-resolution imaging with a low-affinity Ca2+ sensor. We quantified the recordings with a novel computational framework for automatic image segmentation and [Ca2+]c event identification. Our results demonstrate that under physiological conditions the duration of [Ca2+]c events is variable, and segregated into three reproducible modes, subsecond, second, and tens of seconds time range, and are a result of a progressive temporal summation of the shortest events. Using pharmacological tools we show that activation of intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in β cell collectives, and that a subset of [Ca2+]c events could be triggered even in the absence of Ca2+ influx across the plasma membrane. In aggregate, our experimental and analytical platform was able to readily address the involvement of intracellular Ca2+ receptors in shaping the heterogeneity of [Ca2+]c responses in collectives of endocrine cells in situ.NEW & NOTEWORTHY Physiological glucose or ryanodine stimulation of β cell collectives generates a large number of [Ca2+]c events, which can be rapidly assessed with our newly developed automatic image segmentation and [Ca2+]c event identification pipeline. The event durations segregate into three reproducible modes produced by a progressive temporal summation. Using pharmacological tools, we show that activation of ryanodine intracellular Ca2+ receptors is both sufficient and necessary for glucose-dependent [Ca2+]c oscillations in β cell collectives.
European Journal of Obstetrics & Gynecology and Reproductive Biology, Oct 1, 2007
To evaluate the rate and type of aneuploidies of chromosomes 13, 16, 18, 21 and 22, with respect ... more To evaluate the rate and type of aneuploidies of chromosomes 13, 16, 18, 21 and 22, with respect to the length of in vitro maturation (IVM) period, and to compare the results to previously published studies on aneuploidy rates of unfertilized, uninseminated mature oocytes and first polar bodies. Two hundred and twelve immature germinal vesicle stage oocytes were assigned to two groups. After successful IVM, depending on their maturational period of 24h (Group A) or 36h (Group B), chromosomal analysis was performed by five color fluorescence in situ hybridization (FISH). In Groups A and B the rates of aneuploid oocytes were calculated and compared by chi-square test. Also the rates of hyperhaploidy, hypohaploidy, disomy and nullisomy were determined and compared by chi-square test. The difference was considered statistically significant at p-value of &amp;amp;amp;amp;amp;amp;lt;0.05. The prolonged IVM did not significantly affect the aneuploidy rate compared to the shorter maturation period (48.1% and 45.0%, respectively). Regarding the unbalanced premature chromatid separation, no statistically significant difference was found between hyperhaploidy and hypohaploidy (14.8% versus 8.3%). For chromosome nondisjunction, higher frequency of disomy than nullisomy was observed (30.6% versus 14.8%; p&amp;amp;amp;amp;amp;amp;lt;0.05). The estimated global aneuploidy rate was between 42% and 63%. The aneuploidy rate of IVM GV-oocytes is comparable to the aneuploidy rate of in vivo matured oocytes and first polar bodies, regardless of the length of maturation period. This suggests that the immature oocytes can be used in infertility treatment after they complete maturation.
Knjiga Izbrana poglavja iz fiziologije za študente medicine z navodili za vaje so strukturirana t... more Knjiga Izbrana poglavja iz fiziologije za študente medicine z navodili za vaje so strukturirana tako, da študent skozi prvi dve poglavji osvoji fiziologijo vzdražnih celic. Sledijo poglavja, ki obravnavajo fiziologijo nekaterih notranjih organov. Več poglavij je namenjenih kardiovaskularni fiziologiji, kjer študent usvoji koncepte arterijskega pritiska, načine merjenja električne aktivnosti srca z elektrokardiografijo ter dejavnike in spremembe minutnega volumna srca. Zadnja tri poglavja postavijo posamezne organe v kontekst celotnega telesa. V njih se študent seznani z delovanjem organov v medsebojni interakciji ter odzivom telesa na različne zunanje stresorje. V vsakem poglavju so podani primeri različnih patoloških stanj, ki so primerni za poglobljen študij obravnavane tematike in predstavljajo uvod v klinične predmete na študiju medicine. Teoretičnemu delu vsakega poglavja sledi navodilo za izvedbo praktične vaje, s pomočjo katerega lahko študent samostojno ali ob pomoči kolegov izvede meritve, jih analizira in tako poglablja svoje znanje.
Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterize... more Extreme or unaccustomed eccentric exercise can cause exercise-induced muscle damage, characterized by structural changes involving sarcomere, cytoskeletal, and membrane damage, with an increased permeability of sarcolemma for proteins. From a functional point of view, disrupted force transmission, altered calcium homeostasis, disruption of excitation-contraction coupling, as well as metabolic changes bring about loss of strength. Importantly, the trauma also invokes an inflammatory response and clinically presents itself by swelling, decreased range of motion, increased passive tension, soreness, and a transient decrease in insulin sensitivity. While being damaging and influencing heavily the ability to perform repeated bouts of exercise, changes produced by exercise-induced muscle damage seem to play a crucial role in myofibrillar adaptation. Additionally, eccentric exercise yields greater hypertrophy than isometric or concentric contractions and requires less in terms of metabolic...
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Papers by Lidija K Bombek