Biomedical subjects

S Sebille

Publications and source records attributed to S Sebille.

13 recordsLinked to original sources

PubMed2005

Regulation of store-operated calcium entries and mitochondrial uptake by minidystrophin expression in cultured myotubes.

Defective expression of dystrophin in muscle cells is the primary feature of Duchenne muscular dystrophy (DMD), which is accompanied by fiber necrosis and intracellular calcium mishandling. These features led to the hypothesis that dystrophin could control calcium movements. Calcium mishandling in human DMD myotubes is dependent on contraction and/or calcium release activity, suggesting the involvement of channels being activated during these processes. Forced expression of minidystrophin at the plasma membrane of dystrophin-deficient Sol8 myotubes reactivates appropriate sarcolemmal expression of dystrophin-associated proteins and results in normal calcium homeostasis. In active dystrophic myotubes, store-operated calcium channels could be responsible for a sustained calcium influx in muscle cells. We show here that depletion of calcium stores (sarcoplasmic reticulum) by repetitive activation of calcium release and blockade of SERCA leads to a calcium influx. In myotubes expressing recombinant minidystrophin, these store-dependent influxes were reduced to a level similar to that observed in myotubes expressing native dystrophin. High store-dependent calcium influxes in dystrophin-deficient myotubes were associated with sustained cytosolic calcium transients and high intramitochondrial entries, while lower store-dependent calcium influx in myotubes expressing minidystrophin resulted in shorter calcium transients and reduced calcium uptake into mitochondria. We propose that minidystrophin negatively regulates sarcolemmal store-dependent calcium channels, which reduces store-dependent calcium influx, as well as its mitochondrial uptake. Forced expression of minidystrophin in dystrophic cells might restore the regulation of sarcolemmal store-dependent channels, which could protect against calcium mishandling.

Boron Compounds↗

PubMed2005

Calcium sparks in muscle cells: interactive procedures for automatic detection and measurements on line-scan confocal images series.

In muscle cells, force development is controlled by Ca2+ ions, which are rapidly released from the sarcoplasmic reticulum (SR) during sarcolemmal depolarization. In addition to this synchronized spatially homogeneous calcium signal, localized quantal Ca2+ release events (sparks) have been recorded using laser scanning confocal fluorescence microscopy. Previously, algorithms without user intervention have been developed to automatically detect and analyse sparks on confocal line-scan (space-time: 512 x 512 pixels) single images. Here we present a computer program that we called "HARVest of Elementary Events" (HARVELE) developed to both analyse events on series of confocal images and follow sparks morphology from one site during several seconds. HARVELE, coded in the image-processing language IDL 5.3., can be applied on series of n images (512 x 512 x n) obtained from the same scanning line. Computing simultaneously entire series of images allows to measure, for each release site, the frequency and the morphology of release with the conventional amplitude, size, time and duration parameters defined for sparks analysis. The use of these procedures rapidly provides much information about the properties of calcium release sites in muscle cells population and can be applied on any elementary calcium events whatever the type of cell.

Animals↗

PubMed2004

Recent developments in the chemistry of potassium channel activators: the cromakalim analogs.

Potassium channels play a crucial role in controlling the cell membrane potential. Among the different varieties of K(+) channels, the ATP-sensitive potassium channels (K(ATP) channels) have been characterized in numerous cell types, such as skeletal and smooth muscle cells, endocrine cells, cardiac cells and central neurons. Several molecules are known to activate K(ATP) channels and have been named "potassium channel openers" (PCOs). Such compounds may have a wide therapeutic potential and a few drugs are currently used as antihypertensive agents. Different chemical series of PCOs have been explored. This heterogeneous group of organic compounds comprises the benzopyran series including potent vasorelaxant drugs, such as cromakalim. The latter compound, a typical example of potassium channel opener, exerts its biological effect by activating K(ATP) channels. This review presents recent developments in the chemistry of cromakalim analoges and reports chemical aspects governing their potency and tissue selectivity.

Animals↗

PubMed2003

[Radiographic anomalies and obstructive sleep apnea syndrome].

BACKGROUND: The purpose of this study was to identify the particular cranio-facial pattern observed in patients with obstructive sleep apnea syndrome and to search for possible correlations between morphological anomalies and disease severity. MATERIAL AND METHODS: The study group included 49 dentate patients, mean age 47.7 years suffering from obstructive sleep apnea syndrome. Most of the patients were overweight. RESULTS: Typical features observed in these patients were a short craniospinal field, a retro-maxillary, a retro-mandibula, antero-inferior vertical excess of the face, and class II malocclusion. No correlation between severity of obstructive sleep apnea syndrome and craniofacial morphology could be identified. DISCUSSION: These results are in agreement with data in the literature. The absence of a morphological correlation appears to be related to the type of patients studied (overweight). Indeed, two categories of sleep apnea patients have been identified: obese patients who have few or no anomalies of the facial skeleton and thin patients with characteristic open bite class II malocclusion.

Adult↗

PubMed2001

Excitation-contraction coupling in skeletal muscle of a mouse lacking the dihydropyridine receptor subunit gamma1.

1. In skeletal muscle, dihydropyridine (DHP) receptors control both Ca(2+) entry (L-type current) and internal Ca(2+) release in a voltage-dependent manner. Here we investigated the question of whether elimination of the skeletal muscle-specific DHP receptor subunit gamma1 affects excitation-contraction (E-C) coupling. We studied intracellular Ca(2+) release and force production in muscle preparations of a mouse deficient in the gamma1 subunit (gamma-/-). 2. The rate of internal Ca(2+) release at large depolarization (+20 mV) was determined in voltage-clamped primary-cultured myotubes derived from satellite cells of adult mice by analysing fura-2 fluorescence signals and estimating the concentration of free and bound Ca(2+). On average, gamma-/- cells showed an increase in release of about one-third of the control value and no alterations in the time course. 3. Voltage of half-maximal activation (V(1/2)) and voltage sensitivity (k) were not significantly different in gamma-/- myotubes, either for internal Ca(2+) release activation or for the simultaneously measured L-type Ca(2+) conductance. The same was true for maximal Ca(2+) inward current and conductance. 4. Contractions evoked by electrical stimuli were recorded in isolated extensor digitorum longus (EDL; fast, glycolytic) and soleus (slow, oxidative) muscles under normal conditions and during fatigue induced by repetitive tetanic stimulation. Neither time course nor amplitudes of twitches and tetani nor force-frequency relations showed significant alterations in the gamma1-deficient muscles. 5. In conclusion, the overall results show that the gamma1 subunit is not essential for voltage-controlled Ca(2+) release and force production.

Action Potentials↗

PubMed2001

Effect on insulin release of compounds structurally related to the potassium-channel opener 7-chloro-3-isopropylamino-4H-1,2,4-benzothiadiazine 1,1-dioxide (BPDZ 73): introduction of heteroatoms on the 3-alkylamino side chain of the benzothiadiazine 1,1-dioxide ring.

7-Chloro-3-pyridyl(alkyl)amino-4H-1,2,4-benzothiadiazine 1,1-dioxides and 3-alkylamino-7-chloro-4H-1,2,4-benzothiadiazine 1,1-dioxides containing one or more heteroatoms on the side chain in the 3 position have been synthesized in an attempt to discover new potent KATP-channel openers. The compounds were tested as putative pancreatic B-cells KATP channel openers by measuring their inhibitory activity on the insulin releasing process. The influence on the biological activity of the nature of the side chain in the 3 position is discussed.

Animals↗

PubMed2000

Free and total magnesium in lymphocytes of migraine patients - effect of magnesium-rich mineral water intake.

Dietary surveys performed in Western countries show magnesium intakes lower than the recommended dietary allowances, suggesting a large prevalence of magnesium deficiency. Low brain magnesium as well as impaired magnesium metabolism have also been reported in various diseases such as migraine. To detect these deficiencies, a non-invasive and sensitive test assessing magnesium status is needed. Because magnesium is an intracellular cation, either total or ionized magnesium (Mg(2+)) of blood cells were suggested as the most adequate tests. Total magnesium levels in plasma, erythrocytes and lymphocytes and Mg(2+) in lymphocytes were analyzed in a group of 29 migraine patients and 18 control subjects. Results show significantly lower concentrations of total magnesium in erythrocytes (50.7+/-4.7 vs. 53.5+/-2.9 mg/l; P<0.01) and of Mg(2+) in lymphocytes (12.0+/-3.5 vs. 14.2+/-3.8 mg/l; P<0.05) in migraine patients as compared to controls. While a significant difference of mean values was noted between migraine patients and controls, an overlap of individual values was observed. These analyses were repeated on migraine patients before and after a 2-week intake of a mineral water containing 110 mg/l magnesium, and a significant increase in all intracellular magnesium concentrations with no effect on plasma magnesium was observed. These increased intracellular magnesium concentrations demonstrate the bioavailability of magnesium from this mineral water. Among the analyzed parameters, Mg(2+) in lymphocytes appears to be the most sensitive index of magnesium deficiency with a 15% decrease in migraine patients when compared to controls and a 16% increase after 2 weeks of a magnesium-rich mineral water intake.

Adult↗

PubMed2000

[Growth: responses to pathology. Preliminary study].

Many pathologies involve face. Among them, many have craniofacial growth consequences. The authors' aims are to analyze some of these pathologies, where clinical observations emphasize the role of the different craniofacial growth patterns. Despite a complex relation between the malformative part and the deformative one, untreated observations provide a better understanding of some craniofacial growth defects. Syndromes can be classified in 4 categories, involving the primitive causes of the clinical finding: 1. organic abnormalities of one or many functional matrix, 2. localized abnormalities of the anatomical structures, 3. general abnormalities of the conjunctive tissue, 4. mixed syndromes. Many observations will presented.

Cephalometry↗

PubMed1999

Telemedicine to Iowa's correctional facilities: initial clinical experience and assessment of program costs.

OBJECTIVE: To evaluate the costs and benefits of a prison telemedicine program for the institutions involved and to assess early provider satisfaction. MATERIALS AND METHODS: A survey of primary care and consulting providers from four prisons and an academic tertiary care facility in Iowa was conducted during the first year of telemedicine service linked with the state's correctional facilities, from March, 1997 to February, 1998. Data were evaluated from 247 completed telemedicine encounters. Cost estimates were made for (1) 1997 cost data for the 4,396 Iowa prisoners who were transported to The University of Iowa Hospitals and Clinics (UIHC) for their health care, and (2) the equipment, circuitry, and personnel costs necessary on both ends of the network to provide comparable telemedicine service to remote patients and providers. A formula for estimating the cost of implementing a telemedicine service is presented. It includes a projection for determining at what point the cost of the telemedicine visit approaches the average cost of an on-site visit (breakeven point). There was also a brief survey administered to presenting and consulting physicians to determine their overall satisfaction with the telemedicine system for diagnosis, treatment planning, and follow-up. RESULTS: The average cost to the prisons for an on-site inmate visit to the University of Iowa Hospitals and Clinics (UIHC) was $115 during our study period, from March 1997 to February 1998. Using a formula that specifies a number of fixed and variable costs for implementing telemedicine, we were able to determine that the breakeven point for Iowa's correctional facilities would require 275 teleconsultations per year, per site (total of 1,575 consultations a year). Given the higher equipment investment at the UIHC hub, the breakeven point would be around 2,000 teleconsultations annually. Cost studies did not include medical care, which is assumed to be relatively comparable for both on-site and telemedicine interactions. Overall, referring physicians expressed a higher rate of satisfaction with telemedicine than specialists (4.19 to 3.45, respectively, on a scale of 1 to 5 - 5 representing the highest ranking). Both consulting and referring physicians ranked the quality of transmission the highest among all questions regarding satisfaction with the telemedicine system. CONCLUSIONS: No one should anticipate instantaneous cost-effectiveness with telemedicine. However, with careful planning, implementing a telemedicine program can be "cost-acceptable" initially. Telemedicine ultimately becomes cost-effective as the volume of teleconsults increases.

Cost Savings↗

PubMed1998

Extracellular Mg2+ inhibits both histamine-stimulated Ca(2+)-signaling and exocytosis in human tracheal secretory gland cells.

The effects of extracellular Mg2+ concentration have been investigated on the histamine-stimulated exocytotic process of human tracheal secretory gland (HTG) cells. The exocytosis of secretory granules (SG) was observed concomitantly with dynamic changes of intracellular Ca2+ ([Ca2+]i) and Mg2+ concentrations ([Mg2+]i). The rate of SG exocytosis was appraised by the decrease of quinacrine fluorescence emission. Dynamic changes of [Mg2+]i and [Ca2+]i in HTG cells were determined by the combined use of UV-microspectrofluorometry with Mag-Indo-1 and Indo-1 probes, respectively. High Mg2+ medium significantly inhibited the histamine-stimulated secretion. The influence of the extracellular and intracellular Mg2+ concentrations on [Ca2+]i was analyzed. Basal [Mg2+]i increased from 0.8 mM in a Mg(2+)-free medium to 1.7 mM in 10 mM Mg2+ medium. Histamine induced a [Mg2+]i increase which is dependent on extracellular Mg2+ concentration. The histamine stimulated [Ca2+]i rise was reduced in the presence of elevated Mg2+ extracellular medium and inhibitory effects of extracellular Mg2+ were concomitant with changes in [Mg2+]i. Our data suggest that the inhibition by extracellular Mg2+ of stimulated exocytosis is dependent on both the increase of [Mg2+]i and the inhibition of cytosolic Ca2+ influx.

Calcium↗

PubMed1998

Resistance to apoptosis induced by topoisomerase I inhibitors in multidrug-resistant HL60 leukemic cells.

The induction of apoptosis by topoisomerase I inhibitors, camptothecin and SN38, was evaluated in drug-sensitive HL60 and multidrug-resistant (MDR) HL60-Vinc leukemic cells. MDR cells displayed a partial resistance to these apoptotic stimuli and this phenomenon was not modulated by verapamil. Basal free calcium concentrations were similar in both cell sublines and were not modified during treatment. Cytoplasmic pH was more acidic in sensitive cells than in MDR cells. Moreover, a significant acidification was obtained during the early stage of apoptosis in sensitive HL60 cells only. Basal Bcl-2 protein expression was found to be greater in MDR than in sensitive cells and was not modulated by apoptosis inducers. This increase of Bcl-2 in MDR cells could be due to the selection process as vincristine enhances Bcl-2 phosphorylation and expression in HL60 sensitive cells. MDR HL60-Vincristine cells therefore display a resistance to apoptosis induced by non-MDR drugs, possibly by Bcl-2 overexpression and inability of these drugs to mediate intracellular pH changes in these drug-resistant cells.

Antineoplastic Agents, Phytogenic↗

PubMed1997

Anthracycline subcellular distribution in human leukemic cells by microspectrofluorometry: factors contributing to drug-induced cell death and reversal of multidrug resistance.

There is a large discrepancy between the changes in drug accumulation and the changes in drug cytotoxicity that accompany development of anthracycline in multidrug-resistant cells. Moreover, although different molecular targets for anthracyclines such as DNA, cell membranes, or enzymes like topoisomerases could be involved, mechanisms by which these compounds exert their cytotoxic and differentiating effects remain unclear. Studies of correlation between the biological effects of anthracyclines and drug uptake have given conflicting conclusions. For example, a decrease in drug cytotoxicity for different incubation temperatures has been observed in spite of the same intracellular anthracycline amount, suggesting that temperature-dependent cytotoxic effects may be mediated by drug interaction with the cell membrane. What we propose in this review are results of our laboratory which are in agreement with an action mechanism targeted to the nucleus. In fact, we have shown by using microspectrofluorometry, that identical nuclear anthracycline concentration induces the same degree of cytotoxicity, independent of cellular MDR phenotype and the anthracycline structure. Thus, we could acquire information on the mechanisms of drug resistance related to drug transport. We could also give evidence that this accumulation is increased when MDR modulators, such as verapamil and S9788 and cyclosporin A or anthracyclines are used. For clinical applications, our studies have already dealt with nuclear concentration measurements of doxorubicin in leukocytes of treated patients, and in vitro measurements of drug efflux from nuclei of acute leukemic cells and its correlation with P-glycoprotein expression. However, in these studies, there was no correlation between anthracycline nuclear accumulation in vitro and P-glycoprotein expression. In addition, from preliminary results, we have shown that some modulators such as quinine do not significantly increase nuclear accumulation of anthracyclines in MDR cells but are able to restore anthracycline sensitivity. Other authors have recently shown that quinine has a relatively weak effect on cellular doxorubicin accumulation in MDR cells but is able to completely restore doxorubicin sensitivity. They concluded that quinine has essentially intracellular targets involved in drug distribution (cytoplasm --> nucleus) from sequestration compartments. Our data contradict this and we believe that such modulator modifies the molecular environment of anthracyclines and/or their binding to a possible cytoplasmic target leading to different cell death. Thus, we conclude that mechanisms by which anthracyclines induce cell death, and ways by which chemotherapy fails in resistant cells remain complex and are related to more than one target.

Antibiotics, Antineoplastic↗

PubMedDate not supplied

Effect of S9788, cyclosporin A and verapamil on intracellular distribution of THP-doxorubicin in multidrug-resistant K562 tumor cells, as studied by laser confocal microspectrofluorometry.

S9788 modulating resistance effect has been investigated on the activity of THP-DOX against multidrug-resistant K562R cells and compared to that of cyclosporin A and verapamil. Intracellular THP-DOX distribution and particulary its intranuclear concentration, with or without modulators, has been measured using confocal laser microspectrofluorometry. The kinetics of intranuclear accumulation of THP-DOX (1 microM in the medium), as a function of time, were rapid in K562S and K562R cells. Maximum accumulation of THP-DOX is reached in a few minutes (K562S, 400 microM; K562R, 40 microM). The addition of S9788, cyclosporin A and verapamil (5 microM) after one hour THP-DOX incubation, led to respectively 290, 250 and 114 microM. Uptake of THP-DOX was increased in K562R cells by a factor of 7 when S9788 was added. Results obtained on THP-DOX efflux from nuclei of K562S and K562R cells, after 3 hours of incubation without drug, showed a very short T1/2 (time corresponding to 50% decrease of intranuclear concentration of THP-DOX) in K562R cells (12 min) compared to that in K562S cells (150 min). The addition of S9788, cyclosporin A and verapamil (5 microM) led to a T1/2 of 90, 30 and 20 min respectively. The T1/2 of THP-DOX was increased in K562R cells by a factor of 7.5 when S9788 was added. We tried to correlate these results with those obtained in growth inhibition study. The IC50 (concentration which induces 50% growth inhibition) of THP-DOX, corresponding to one hour THP-DOX treatment and 3 days culture of K562S and K562R cells were respectively 230 and 7000 nM, and the RI (resistance index) value is 30. The addition of S9788, cyclosporin A and verapamil (5 microM), during the one hour treatment, led to an IC50 value of 350, 2000 and 5000 nM respectively. S9788 induced an IC50 value 20 times lower than without the modulator. Our study suggests that the higher activity of THP-DOX against K562R cells in the presence of S9788, compared to cyclosporin A and verapamil, is due to a higher intranuclear THP-DOX accumulation and to a strong decrease of drug efflux from K562R nuclei. This could be explained by a higher affinity of S9788 for membrane P-glycoprotein of K562R cells and/or an additional mechanism of action.

Antineoplastic Agents↗