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Biomedical subjects

G Raymond

Publications and source records attributed to G Raymond.

At least 37 records · Page 2Linked to original sources
PubMed1990

The direct depressant effect of LCB29 (idrocilamide) on mechanical tension of rat soleus muscle fibers.

The effect of LCB29 was tested on twitch characteristics, tetanic tension, and K+ and voltage-clamp contractures of rat soleus muscle fibers. In concentrations ranging from 10(-6) to 5 x 10(-4) M, LCB29 simultaneously inhibited the twitch amplitude, the maximum rate of tension development, and the maximum rate of relaxation. In concentrations ranging from 10(-5) to 10(-4) M, tetanic tension (100 Hz, 1 s) was inhibited by the same amount. The effect of 5 x 10(-5) M LCB29 was studied on K+ contractures and contractures induced, under voltage-clamp conditions, by long-lasting depolarizations. Its effect was significantly stronger than those on twitch and tetanic tension. In addition, LCB29 had a dual effect on strength--duration curves for mechanical threshold. It increased both the rheobasic potential and the steepness of the curve. It is concluded that LCB29 exerts a direct myorelaxant effect on rat soleus muscle; two sites of action are probably involved.

Animals↗
PubMed1990

[Intraprostatic spiral for the treatment of benign prostatic hypertrophy. A new method of insertion with sonographic monitoring. Apropos of 35 patients].

The treatment of subvesical obstruction with a spiral endoprostatic prosthesis is now well-known since Fabian's initial work (1980). A new method of insertion of the spiral with a releasable catheter and under sonographic monitoring has been proposed recently. This article is a report of a series of 35 patients. These patients presented with an adenoma of the prostate and were fitted with a permanent urethral catheter due to an absolute contraindication for anesthesia. The spiral was inserted with US monitoring in 25 patients. In 5 patients, the spiral had to be inserted under classical endoscopic control. The average follow-up period is 7.2 months. In 25 patients (75%), the spiral remained in place; the maximum flow rate of urine after the insertion averages 12.8 ml/s and 76% of these patients report an improvement of their comfort during urination. The position of the spiral had to be changed in 8 cases. No infectious complication was noted. Hematuric complications are reported in 2 cases. The spiral endoprostatic prosthesis seems to be an elegant alternative to the permanent catheter in patients at high anesthetic risk.

Aged↗
PubMed1990

[Urethrostenosis from Dupuytren to Guyon: "the tools and the men"].

Great progress has been made in the management of urethral narrowing during the second half of the 20th century owing to the appearance of urology as a specialty, to the spinoff of lithotripsy, to the motivation provided by the Argenteuil award and to the refinement of surgical tools. Progress was made in the exploration (impression dilatators, ball exploration) and treatment: permanent or progressive dilatation, cauterization, internal or external urethrotomy. Biographical notes are then given about the surgeons who made this progress possible: Amussat, Benique, Civiale, Desormeaux, Ducamp, Guillon, Heurteloup, Lallemand, Leroy D'Etioles, Maisonneuve, Reybard and Segalas.

Cautery↗
PubMed1989

The depressant effects of some amiloride analogues on the slow outward K+ current and contraction of voltage-clamped frog muscle fibres.

The effects of 4 derivatives of amiloride, which are known to block the Na+/H+ antiporter, were studied on the slow outward current (Iso) and on tension development of voltage-clamped single muscle fibres of the frog Rana ridibunda. Each compound tested induced a strong depressant effect on tension and Iso in a voltage-, time- and dose-dependent (10(-8) to 10(-5) M) manner at physiological pH. The effects exhibited a strong pH dependence (the greater the pH in the range between 6.6 and 8.0, the greater the depressant action). This seems to exclude the involvement of the Na+/H+ antiport and alterations of surface membrane charges as mediators. The current block was not observed after the release of calcium from the sarcoplasmic reticulum was blocked with 75 microM tetracaine. It is concluded that the primary effect of the 4 compounds used was to inhibit the internal release of Ca2+ from the sarcoplasmic reticulum, and that this inhibition blocked the Ca2+-dependent slow outward current.

Amiloride↗
PubMed1989

The slow inward calcium current is responsible for a part of the contraction of patch-clamped rat myoballs.

The slow inward calcium current and the contractile response were simultaneously recorded in voltage clamped (whole cell patch clamp recording) rat myoballs in primary culture. The shape of the contraction(T)/potential(V) relationship and the application of the inorganic calcium channel blocker cadmium (1.5 mM), which suppresses a part of the contractile activity, demonstrate the existence of two components of contraction. One of them is related to the slow calcium current.

Animals↗
PubMed1989

Are Ba2+ and Sr2+ ions transported by the Na+-Ca2+ exchanger in frog atrial cells?

Ba2+ and Sr2+ ions are widely used to replace Ca2+ ions for the study of Ca2+ channel currents in electrophysiological experiments. Using the double sucrose gap technique, we investigated the effects of Sr2+ and Ba2+ ions on the Na+ Ca2+ exchange activity in frog atrial fibres where it is the major relaxation mechanism. With either Sr2+ or Ba2+ ions instead of Ca2+ in the extracellular bath, Na-free contractures reversibly developed but with different kinetics. Voltage clamp experiments showed that the tonic tension recorded in the presence of Sr2+ or Ba2+ was markedly increased following the addition of monensin, a Na+ ionophore known to increase the intracellular Na+ activity. In Na-free solutions (Li-substituted), it was possible to induce contractures by substituting Sr2+ or Ba2+ ions for extracellular Ca2+. These contractures could be relaxed by reintroducing Na+ or Ca2+ ions in the extracellular medium. Taken together, these results suggest that Sr2+ and Ba2+ ions can interact with the Na+-Ca2+ exchange mechanism and potentially participate not only in Na+-cation but also in Ca2+-cation exchanges on either side of the sarcolemmal membrane.

Action Potentials↗
PubMed1989

Genetic switching in the flagellar gene hierarchy of Caulobacter requires negative as well as positive regulation of transcription.

Caulobacter crescentus flagellar (fla, flb, or flg) genes are periodically expressed in the cell cycle and they are organized in a regulatory hierarchy. We have analyzed the genetic interactions required for fla gene expression by determining the effect of mutations in 30 known fla genes on transcription from four operons in the hook gene cluster. These results show that the flaO (transcription unit III) and flbF (transcription unit IV) operons are located at or near the top of the hierarchy. They also reveal an extensive network of negative transcriptional controls that are superimposed on the positive regulatory cascade described previously. The strong negative autoregulation observed for the flaN (transcription unit I), flbG (transcription unit II), and flaO (transcription unit III) promoters provides one possible mechanism for turning off fla gene expression at the end of the respective synthetic periods. We suggest that these positive and negative transcriptional interactions are components of genetic switches that determine the sequence in which fla genes are turned on and off in the C. crescentus cell cycle.

Bacteria↗
PubMed1989

[Mechanisms of excitation-contraction coupling and calcium liberation in striated muscles of vertebrates].

In vertebrate skeletal muscle, the main part of excitation-contraction coupling occurs at the level of the triad, where membranes of T-system and of junctional SR are facing each other. From place to place, the junctional gap is bridged by "feet" structures which include the SR Ca2+ channel. Half of them are closely apposed to tubular intramembranous structures assumed to be DHP-sensitive voltage-sensors which are similar to tubular Ca2+ channels and act by controlling Ca2+ release from SR. During a twitch, the release of Ca2+ activator from SR is controlled both by voltage-sensors via the feet structures and by a tubular Na+ current via a Na+-induced Ca2+ release mechanism. During long-duration mechanical responses, additional mechanisms are involved: a Ca2+-induced Ca2+ release which can be activated by ICa; the release of Ca2+ from membrane, controlled by the operation of a Na+/Ca2+ exchanger and/or new arrangements of surface membrane charges. An IP3-mediated Ca2+ release could be involved too. All these mechanisms can be regulated by intracellular biochemical or ionic processes.

Animals↗
PubMed1988

[1987: the 100th anniversary of transvesical prostatic adenomectomy].

The present study is an attempt to outline the views held with the passage of time on the pathology of prostatic hypertrophy and upon the numerous palliative operations that have been used. As a natural limit, the author close to end the investigation at the beginning of the 20th century, when the principles of radical therapy were defined and accepted. It is demonstrated that a similar limit applies to the question of pathology, as the role of periurethral glands the ffue seat of prostatic hypertrophy was not definitely worked until the studies of Albarran (1900), Motz and Pérearnau (1905).

Europe↗
PubMed1988

A new porcine bioprosthesis: design rationale and early clinical experience.

The Medtronic Intact valve is a third-generation porcine bioprosthesis produced using a leaflet fixation process which imposes virtually zero hydrostatic pressure. This fixation method provides optimal preservation of the original leaflet structure and integrity and should result in an improvement in durability compared to conventional preservation techniques. The biomechanical basis for this hypothesis is presented along with early experience with 118 patients (125 valves). There have been no complications related to primary valve failure and the incidence of other valve related events is acceptable.

Aortic Valve↗
PubMed1987

Antamanide antagonizes the phalloidin-induced negative inotropic effect and blocks voltage dependently the fast outward K+ current in voltage-clamped frog muscle fibres.

The effects of antamanide (10(-14)-10(-5) M) and N-acetyl-secophalloidin (10(-7)-5 X 10(-3) M) a neutral non-toxic derivative of phalloidin, were tested on voltage-clamped single frog muscle fibres. Antamanide protected muscle fibres against the negative inotropic effect of phalloidin but blocked the fast potassium permeability in the same concentration range and the same voltage-dependent manner as did phalloidin. N-Acetyl-secophalloidin exhibited a strongly attenuated blocking effect on K+ permeability in a 1,000-fold higher concentration range than phalloidin. Neither antamanide nor N-acetyl-secophalloidin affected the contractile properties. These results suggest the existence in the frog muscle membrane of a receptor with two sites for phalloidin and antamanide which acts on potassium conductance.

Animals↗
PubMed1987

Tension activation and relaxation in frog atrial fibres. Evidence for direct effects of divalent cations (Ca2+, Sr2+, Ba2+) on contractile proteins and Na-Ca exchange.

The effect of alkali-earth cations (Ca2+, Sr2+, Ba2+) on the excitation-contraction coupling events of the frog atrial fibres were studied using a double mannitol gap voltage clamp technique coupled with a mechano-electric transducer. Photoremoval of the suppressive effect of nifedipine on the calcium channels allowed to obtain rapid transient Ca2+, Sr2+ or Ba2+ ions current jumps. The effect on the amplitude of the associated contraction was proportional to the current jumps. These results together with the correlation established between the estimated increase in the internal concentration of divalent cations and the amplitude of the phasic tension suggest that the essential source of divalent cations for activation of contraction is the extracellular space. Also Ba2+ ions reduced the tonic tension and strongly slowed the relaxation of the phasic component whereas Sr2+ exhibited smaller effects. Sr2+ ions could be more efficient than Ba2+ ions in substituting for Ca2+ ions in the Na+-Ca2+ exchange mechanism known to regulate these two mechanical events. The conclusions are that the order of effectiveness of these ions (Ca2+ greater than Sr2+ greater than Ba2+) is the same with regard to transarcolemmal exchange for Na+ ions, presumed uptake by a "second relaxing system", activation of contraction, and inactivation of the slow inward current.

Action Potentials↗
PubMed1987

Stimulation frequency and external ionic composition control the repriming of caffeine-induced contractures in frog skeletal muscle.

The effect of stimulation rate and of external ionic composition on the repriming period of contractures induced by 6 mM caffeine was tested on isolated skeletal muscle fibres of the frog (Rana ridibunda). The repriming period, which was 11.2 +/- 0.1 min (mean +/- SEM, n = 9) on quiescent fibres, was shortened in fibres stimulated at a frequency ranging from 3 to 12 min-1 (optimal rate, 8 min-1; full repriming 5.7 +/- 0.2 min; n = 10). A 10-fold increase in the extracellular calcium concentration shortened the repriming period on both stimulated and quiescent fibres, whereas decreasing external calcium (1/10) delayed it. In a Na+-free solution (Li+ substituted) the repriming period of stimulated fibres was markedly delayed (14 min), whereas quiescent fibres never recover more than 10% of their ability to develop subsequent caffeine contractures. In contrast, with a 35% Na solution, the repriming period was greatly shortened (stimulated, 5.4 +/- 0.2 min, n = 7; quiescent, 6.2 +/- 0.5 min, n = 8). It is concluded that repriming depends on three mechanisms that seem to refill a calcium store and trigger recovery: the slow inward calcium current, a Na+-Ca2+ exchange, and perhaps a passive Ca2 influx.

Animals↗
PubMed1987

[Two components of calcium-dependent potassium permeability coexist in the membrane of frog skeletal muscle].

Two components of Ca-dependent K permeabilities were demonstrated in the membrane of voltage-clamped muscles fibres by raising the internal calcium concentration with 3 mM caffeine or 0.1 microM Bay K 8644. One, which is TEA-sensitive, is enhanced by an increase of intracellular calcium and the other, which is apamin-sensitive, is inhibited by high levels of internal calcium concentration.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1987

[Value of urinary time in bone scintigraphy in the evaluation of renal function. Apropos of 57 cases of cancer of the prostate].

Intravenous urography (IVU) and bone scintiscan imaging (BSI) are essential investigations during initial evaluation of prostate cancer. A study compared data provided by these two exploratory procedures in evaluation of renal function. Concordance was high (86%) between IVU and urinary images during BSI. The latter examination is non-invasive and has no contraindications. It produces indispensable oncologic information in patients with cancer of prostate and a result of the urinary secretion phase can avoid repetition of IVU during follow up.

Bone and Bones↗