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PubMed1989

Reappearance of miniature endplate potentials in frog neuromuscular junctions "silenced" by lanthanum ions.

Miniature endplate potentials and currents were recorded from frog sartorius muscle fibres. As expected from previous work, La3+ caused a very large increase in miniature endplate potential frequency, followed by a progressive decrease, ending in the virtually complete disappearance of miniature endplate potentials. Soon after its application, La3+ caused an increase in the amplitude of miniature endplate potentials due to a lengthening of the underlying miniature endplate currents. Analysis of membrane current fluctuations produced by acetylcholine showed that La3+ caused an increase in the lifetime of the channels opened by acetylcholine. After miniature endplate potentials had vanished following La3+ treatment, the muscles were placed in organ culture conditions to see if miniature endplate potentials would reappear. After several hours miniature endplate potential activity was resumed in about 25% of the endplates, and disappeared again a few hours later, presumably because of accelerated nerve terminal degeneration. Preliminary electron microscopic observations suggest that the recovery of miniature endplate potential activity was accompanied by re-formation of synaptic vesicles in the motor endings.

Animals↗
PubMed1983

Changes in acetylcholine concentration, miniature end-plate potentials and synaptic vesicles in frog neuromuscular preparations during lanthanum treatment.

ACh content and synaptic ultrastructure were compared in neuromuscular preparations (sartorius muscle of Rana esculenta) incubated in control saline and in saline containing 1 mM LaCl3. ACh concentrations remained constant for 6 hr in control preparations. La3+ caused a 38% depletion of ACh within the first 30 min with subsequent recovery to 120% of control values within 3-4 hr. Recovery was prevented by hemicholinium-3. At 23 degrees C La3+ caused complete loss of synaptic vesicles: no depletion was seen at 4 degrees C. Initially MEPP frequency increased 300- to 700-fold (23 degrees C), then declined. Mean vesicle diameter did not change, but SD increased. As the frequency of MEPPs declined, the percentage of s-MEPPs greatly increased. La3+ had a postsynaptic effect which increased the amplitudes of both s-MEPPs and bell-MEPPs within a few seconds. The s-MEPP mean did not change during the course of La3+ treatment although the bell-MEPP mean usually decreased. How the decrease in synaptic vesicles, decrease in MEPP frequencies, and changes in ACh levels relate to changes in the percentage of different classes of quanta is discussed.

Acetylcholine↗
PubMed1990

The effects of pentachlorophenol (PCP) at the toad neuromuscular junction.

1. Effects of PCP at the frog neuromuscular junction were studied in vitro in sciatic nerve sartorius muscle of the toad Pleurodema-thaul. 2. Within the concentration 0.003-0.1 mM, PCP caused a dose-time-dependent block of evoked transmitter release acompanied by an increase in the rate of spontaneous quantal release. 3. PCP induced an increase in miniature endplate potential (MEPP) frequency and it was not antagonized in a Ca2(+)-free medium, indicating that it does not depend upon Ca2+ influx from the external medium, but may act by releasing Ca2+ from intraterminal stores. 4. The present data, together with previous results concerning PCP at eighth sympathetic ganglia indicate that 3,4-diaminopyridine (3,4-DAP) counteracts the effects of PCP on synaptic transmission. This result suggests that PCP interfering Ca2+ influx occurs during depolarization of motor nerve terminals.

4-Aminopyridine↗
PubMed1995

Modified ilioinguinal node dissection for metastatic melanoma.

BACKGROUND: Standard ilioinguinal node dissection for melanoma has substantial cost and morbidity. Beginning in 1988, we modified the procedure in hopes of reducing side effects without compromising survival. PATIENTS AND METHODS: Dissection was standard except for preservation of saphenous vein and femoral sheath and omission of sartorius muscle transfer. To date, 19 patients with recurrent melanoma in the groin have had the procedure, 6 for N1 disease and 13 for N2, M1 metastases. RESULTS: Average hospital stay was 4.5 days (range 3 to 7). Postoperative edema occurred in 1 (5%) patient. Disease-free survival at 40 months was 66% for N1 disease and 26% for N2, M1 metastases. CONCLUSION: Modified ilioinguinal node dissection appears to reduce cost and morbidity of treating recurrent melanoma in the groin without compromising survival.

Adolescent↗
PubMed1970

Studies on ion distribution in living cells. II. Cooperative interaction between intracellular potassium and sodium ions.

New steady levels of K(+) and Na(+) ion in frog sartorius muscle were reached in 72 hr at 25 degrees C in environments containing 100-mM Na(+)-ion and K(+)-ion concentrations varying from near zero to 10 mM. These steady levels follow a pattern predicted by a cooperative adsorption isotherm presented in 1964. From a total of 13 sets of experiments carried out over a five year period, the average concentration of adsorption sites is 109 mumoles/g of fresh cells. The average intrinsic equilibrium constant for the Na --> K exchange is 135, and the average free energy of nearest neighbor interaction is 0.54 kcal/mole. These values are in good agreement with those obtained by Jones and Karreman from studies on canine carotid arteries.

Adsorption↗
PubMed1972

Energetics of isometric and isotonic twitches in toad sartorius.

Contractile energetics have been studied in twitches of toad sartorius muscle at 6-7 degrees C. Isometric and isotonic energy production has been measured and plotted against a wide range of developed tensions and tension-time integrals. These parameters were varied by altering the isotonic load or by changing the preset isometric length. The isometric tension-independent heat was 1.12 +/-0.18 (SD) mcal/g. The isometric heat coefficient Pl(0)/H was 12.0 +/-1.4 in muscles having twitch to tetanus ratios ranging from 0.4 to 0.6. Isometric enthalpy increased monotonically with tension or tension-time integral but the correlation between isometric heat and these parameters was poor. Isotonic enthalpy consumption was always higher than isometric enthalpy for any given tension or tension-time integral; however, isotonic heat production was consistently less than isometric heat production. The isotonic heat for the highest load (3 g) was not significantly different from the isometric tension-independent heat. Thus isotonic heat production first decreased and then increased with increasing tension or tension-time integral. In the discussion it is shown that the results conflict with all current interpretations of muscle energetics.

Animals↗
PubMed1982

Numerical analysis of the voltage-clamp technique applied to frog neuromuscular junctions.

The nonlinear cable equation was solved numerically by means of an implicit procedure. The correlation between end-plate length and fiber diameter was determined in frog (Rana pipiens) sartorius muscles stained with gold chloride (Löwit, 1875). The diameter of the fibers stained by the Löwit method was 80 (74-85) micron (median and its 95% confidence interval for 52 fibers), the length of the end plates in the same fibers was 382 (353-417) micron. The fibers simulated were 80 micron in diameter. To solve the equation the muscle fibers were represented by 500 segments 20 micron long, and the equation was solved in steps of 10 microseconds; a double exponential function was incorporated to the first seven segments to represent the neuromuscular junction. The potential of the first segment of the cable was set to the clamping level and the membrane potential of the remaining segments calculated. The current needed to hold the first segment was estimated by adding the current flowing through the first segment to the current flowing from it to the second segment. Our results indicate that the lack of space clamp in the point voltage-clamp studies of the frog neuromuscular junction introduces serious errors in the estimates of the end-plate conductance value, the kinetics of the conductance changes, and the reversal potential of the end-plate currents. The possibility of an efficient voltage-clamp technique is also explored. Our calculations suggest that the study of end-plate current and conductance is possible with little error if the end-plate potential is controlled at both ends of the synaptic area simultaneously.

Animals↗
PubMed1985

Equatorial x-ray diffraction from single skinned rabbit psoas fibers at various degrees of activation. Changes in intensities and lattice spacing.

Equatorial x-ray diffraction patterns were obtained from single skinned rabbit psoas fibers during various degrees of activation under isometric conditions at ionic strength 170 mM and 6-9 degrees C. By direct calcium activation, contraction was homogeneous throughout the preparation, and by using a cycling technique (Brenner, 1983) integrity of the fiber was maintained even during prolonged steady activation. The intensity ratio of the two innermost reflections I11/I10, and the normalized intensities I*10 and I*11 varied linearly with increasing force. Thus the result agreed qualitatively with an earlier finding, obtained from the whole sartorius muscle, that intensity changes in 10 and 11 are directly correlated with isometric force level (Yu et al., 1979). Spacing of the myofilament lattice (d10) was found to decrease with increasing isometric tension. With the filaments in full overlap, maximum shrinkage was 14%. The lattice spacing started to level off when the degree of calcium activation was greater than or equal to 50%, approaching a limit approximately at 380-360 A. This decrease of the lattice spacing indicates that there is a radial force produced by force generating cross-bridges, but the net radial force appears to become insignificant as lattice spacing approaches 380-360 A.

Animals↗
PubMed1989

The cost of departure from optimal radii in microvascular networks.

In the Murray optimality model of branching vasculatures, the radii of vessels are related to blood viscosity, vascular metabolic rate, and blood flow rate, in such a way as to minimize the total work (hydraulic and metabolic) of the system. The model predicts that flow is proportional to the cube of a vessel radius, and that at junctions the cube of the radius of the parent vessel equals the sum of the cubes of the daughter radii. In comparing real vasculatures to the Murray model, we have previously had no expressions for evaluating the apparent energy cost for departures from the optimal junction exponent of 3. Such expressions are derived here. They show that junction exponents, from about 1.5 to large positive values, are within 5% of the energy minimum. With the new equations, observed individual junctions or entire vascular trees can be compared, energy-wise, with the Murray optimum. Junctions in the transverse arteriolar trees of cat sartorius muscle were compared to the Murray optimality model, using these new expressions. The junction exponents for these small pre-capillary vessels had a broad range, with a median value greater than the Murray optimum of 3. The exponents were restricted, however, to values requiring, at individual junctions, little increase in energy. The majority of junctions had energy costs less than 1% above the Murray minimum. For entire trees involving many junctions the departures from optimality averaged less than 10%. Thus, while the branching geometry for these microvascular trees deviates significantly from the Murray optimum in the direction of larger daughter to parent ratios, the departures are small in energy terms.

Animals↗
PubMed2003

Primary skin closure of large groin defects after inguinal lymphadenectomy for penile cancer using an abdominal cutaneous advancement flap.

PURPOSE Large groin defects may be created after inguinal lymphadenectomy for bulky metastatic penile cancer. We describe a new method of primary closure of a large groin skin defect. MATERIALS AND METHODS In 3 patients with large volume inguinal lymph node metastases with skin breakdown and secondary infection extensive inguinal lymphadenectomy was done with wide surgical excision of skin and subcutaneous tissue. The procedures resulted in a large groin defect. Sartorius muscle was transferred to cover the femoral vessels. An abdominal advancement cutaneous flap was placed for soft tissue and skin coverage of the wound. RESULTS Primary closure of a large skin defect was possible using an abdominal advancement flap. In all patients the wound healed primarily with good cosmesis. A single patient underwent postoperative external beam radiation therapy to the flap site with no untoward effect on graft survival. CONCLUSIONS Large groin skin defects can be closed primarily using an abdominal advancement flap. This technique may also be used for bilateral groin defects. Compared with other types of flaps advocated for this purpose the main advantages of the procedure are simplicity, lower morbidity and superior cosmetic results.

Adult↗
PubMed1984

Electrophysiological analysis of the cholinergic effects of cimetidine and ranitidine.

The study takes the form of an analysis of the effects of cimetidine and ranitidine (2 x 10(-4) M) on 9 electrophysiological parameters, using a single frog sciatic nerve-sartorius muscle preparation. The parameters evaluated were: (i) mean end-plate potential (e.p.p.) amplitude, and mean 50%-corrected e.p.p. amplitude, (ii) mean rise time (RT), (iii) mean half-decay (HD), (iv) mean miniature end-plate potential (m.e.p.p.) amplitude, (v) mean resting membrane potential (RMP), (vi) mean m.e.p.p. frequency (f), (vii) mean quantal content (m), (viii) quantum release probability (p), and (ix) number of active sites (n) in the nerve terminal. Marquardt analysiswas used in order to determine the effects of cimetidine and raniditine on end-plate potential kinetics. At the concentration assayed only ranitidine showed a marked blocking effect at postsynaptic level as well as a less pronounced presynaptic effect. The time course of the e.p.p.'s is also more affected by raniditine, though the kinetic behaviour observed is not a unique feature of this drug alone.

Animals↗
PubMed2001

The role of desensitisation in decay time of miniature endplate currents in frogs Rana ridibunda and Rana temporaria.

A new comparative characteristic of endplate microphysiology has been introduced. It is the feasibility of receptors to become desensitised as demonstrated on two frog species, Rana temporaria and Rana ridibunda: the decay times (tau(MEPC)) of single quantum miniature endplate currents (MEPCs) in the sartorius muscles of both species were about 1 ms and were not affected by the desensitisation-promoting agent proadifen when AChE was active. However, when the desensitisation was induced by anticholinesterase neostigmine and promoted by proadifen, the prolongation of tau(MEPC) from 1 ms was almost twice as great in Rana temporaria (tau(MEPC) = 4.4 ms) than in Rana ridibunda (tau(MEPC) = 3.1). This indicates that desensitisation reduces the number of available receptors and lowers the number of available ACh molecules for repetitive binding by trapping them by desensitised, high-affinity receptors significantly more in Rana ridibunda than in Rana temporaria. The application of proadifen, a promoter of desensitisation, decreased the prolongation of MEPCs in both species, but this shortening was more rapid in Rana ridibunda than in Rana temporaria. It is concluded that the desensitisation-induced reduction in the density, and the number of postsynaptic receptors is significantly higher at Rana ridibunda than in Rana temporaria endplates.

Animals↗
PubMed1999

Fractal dimensions in the occurrence of miniature end-plate potential in a vertebrate neuromuscular junction.

1. Occurrence of miniature endplate potentials (MEPP) in the sartorius muscle of Rana catesbiana in high Mg2+ Ringer solution were observed in standard intracellular recording. Intervals and amplitudes of sequentially occurring MEPP were registered and analyzed. 2. Interval histograms of a time series of MEPP showed exponential-like pattern as reported in the classical study by Fatt and Katz (1952). The cumulative distribution of the intervals plotted in logarithmic axes showed two distinct phases. In shorter intervals (< 1s), curve along exponential decay was observed, and in longer intervals (> or = 1s) linear decay can be seen. The latter power-law relation gave dimensions of 4.111 +/- 0.812 (mean and S.D.). Self-similarity in longer range implies a time-scale invariant nature and may suggest fractal nature in restoration process of synaptic vesicles, while exponential decay in the short time interval range implies random release of transmitter packet from the readily releasable pool. 3. Fluctuation of amplitudes in sequentially occurred MEPP were analyzed according to Higuchi's cumulative route-length analysis. The estimates for sequential amplitude curve showed the power-law relation in a logarithmic plot whose inclination (= D) estimated with linear regression analysis was 1.996 +/- 0.007 (mean and S.D.). This results indicate that fluctuation in the amplitude of MEPP shows possible maximum complexity as a graphic curve in 2-D plane. Similar result was obtained for fluctuation of intervals of successively occurring MEPP.

Algorithms↗
PubMed1994

In situ replacement of arterial prosthesis infected by bacterial biofilms: long-term follow-up.

PURPOSE: Bacterial biofilm infections of vascular prostheses are characterized by an absence of systemic sepsis, a fluid-filled cavity surrounding the graft, a draining sinus tract, and microorganisms that must be removed from the fabric prosthesis for bacterial culture. METHODS: Since 1987 we have treated 20 infected grafts with prosthetic excision and in situ replacement in 14 men and 6 women. The time from initial graft implantation to diagnosis of graft infection ranged from 3 months to 14 years (mean 4.5 years). The original graft (Dacron-17, polytetrafluoroethylene-3) was an aortobifemoral in 14, axillofemoral femorofemoral in 3, iliofemoral in 2, and femoropopliteal in 1 patient. Presenting symptoms were groin false aneurysm with perigraft fluid in 10, inflammatory mass in 6, and sinus tract in 4. At surgery all unincorporated graft material and the perigraft capsule were excised from a point where the proximal graft was incorporated, including debridement of vessels at the distal anastomosis. Of the 14 aortobifemoral grafts, only the femoral limbs were excised at the initial presentation of biofilm infection. The conduit was replaced with an in situ polytetrafluoroethylene interposition graft, which was covered with a gracilis or sartorius muscle flap when possible. RESULTS: All surgical sites healed, all grafts remained patent, and there was no limb loss. After ultrasonic oscillation of the explanted graft, bacterial cultures recovered coagulase-negative Staphylococcus species in 14, coagulase-positive Staphylococcus species in one, both species in three, with no growth from two specimens. During follow-up, two patients have had clinical involvement in the proximal intraabdominal portion of the graft that had not been previously resected. In all grafts, the in situ replacement graft remained well incorporated. CONCLUSION: In situ graft replacement is effective treatment for biofilm infections of vascular prostheses. Because of the indolent nature of these infections, subsequent infection of previously uninvolved graft segments may be expected.

Bacterial Adhesion↗
PubMed1982

(+/-)-2-Depentylperhydrohistrionicotoxin: a new probe for a regulatory site on the nicotinic acetylcholine receptor-channel.

(+/-)-2-Depentylperhydrohistrionicotoxin (4), several of its analogues, and N- and O-substituted derivatives were prepared and tested for their effects on the neuromuscular transmission of the frog sartorius muscle. Compound 4, its N-methyl derivative 5, the O-acetyl derivative 9, and the quaternary methiodides 19 and 20 blocked the indirectly elicited twitch. The oxidation of 4 and 5 to ketones 12 and 14 and their reduction to the epimeric alcohols 17 and 18 afforded materials with substantially reduced activity. N-Acetylation of 4 to 11 changed the course of the activity to a transient potentiation of muscle twitch. Both 4 and 5 were not very toxic to mice after subcutaneous administration. (+/-)-7-n-Butyl-1-azaspiro[5,5]undecan-8-one (12) epimerized readily at room temperature to afford the epimer 13, and preparation of the hydrochloride of its N-methylated derivative 14 was accompanied by a retro-Michael reaction, affording the 2-n-butyl-3-[4-(methylamino)butyl]cyclohexene-2-one (22). The strongly hydrogen-bonded alcohol 4 was analyzed as the hydrobromide by a single-crystal X-ray analysis, confirming its structure.

Amphibian Venoms↗
PubMedDate not supplied

Pre- and postsynaptic effects of the calcium channel blocker verapamil at neuromuscular junctions.

Experiments on the frog sartorius muscle were used to study the effects of the L-type calcium channel blocker verapamil on endplate currents. Verapamil had no effect on the amplitudes of miniature and multiple-quantum endplate currents, the synchronicity of transmitter secretion, or repeat activity in nerve endings. Verapamil had no effect on the decay of miniature currents, but accelerated that of multiple-quantum currents. This effect was sharply increased after inhibition of cholinesterase activity. In conditions of inhibited cholinesterase activity, verapamil depressed currents during rhythmic stimulation. This depression was more marked in synapses with high quantal compositions and in conditions of membrane depolarization. Thus, the sensitivity of neuromuscular junction calcium channels to verapamil was unrelated to the release of transmitter from the motor nerve ending either at physiological levels of secretion or when secretion was potentiated by potassium channel blockers. At the postsynaptic level, the effect of verapamil was insignificant in relation to cholinoreceptors in the resting and active states, though verapamil could cooperatively enhance the transition of postsynaptic receptors into the desensitized state in conditions of prolonged transmitter action.

Acetylcholinesterase↗
PubMed2001

[Inguinal hernia as a diagnostic error in ruptured groin aneurysm].

Anastomotic aneurysms observed with an incidence of 0.5% to 5.0% are considered a known complication following arterial surgery, especially when fabric grafts in the inguinal region are implanted. An anecdotal report is presented describing a 64-year old male patient, who developed, 10 years following an autologous femoro-tibial vein graft, a huge mass in the left groin. The lesion was considered an incarcerated inguinal hernia and the patient was admitted to the Department of Surgery for emergency repair. Clinical examination, duplexsonography and CT scan clarified the diagnosis of an aneurysm with a diameter of 13 cm. The aneurysm was resected, and a femoro-profundal vein graft was implanted orthotopically, the graft was covered with a sartorius muscle flap. The postoperative course was uneventful. The diagnosis is suspected by clinical examination and usually confirmed by duplexsonography. The exact etiology of suture line aneurysms is unknown; in the present case progression of the underlying arteriosclerotic arterial disease after a follow up of 10 years is likely. For the treatment the usual methods of complicated aneurysm repair and preservation of the arterial circulation--using autologous in situ methods or extraanatomic bypass grafts--with additional biologic coverage are at hand.

Aneurysm, Ruptured↗
PubMed1998

ATP and adenosine inhibit transmitter release at the frog neuromuscular junction through distinct presynaptic receptors.

1. The effects of exogenous ATP or adenosine on end-plate currents (e.p.cs; evoked by simultaneous action of a few hundred quanta of ACh) or on miniature e.p.cs (m.e.p.cs) were studied under voltage clamp conditions on frog sartorius muscle fibres. 2. ATP or adenosine (100 microM(-1) mM) reduced the e.p.c. amplitude but did not affect m.e.p.c. amplitude, decay time constant and voltage-dependence of m.e.p.c., suggesting that e.p.c. depression induced by these purines had presynaptic origin only. 3. The action of ATP, unlike that of adenosine, was prevented by the P2-purinoceptor antagonist suramin (100 microM). The stable ATP analogue alpha,beta-methylene ATP (100 microM), known to be desensitizing agent on P2X receptors, also abolished the depressant effect of ATP while sparing the action of adenosine. Concanavalin A, an inhibitor of ecto-5'-nucleotidase, did not affect the presynaptic action of exogenously applied ATP. 4. The presynaptic action of adenosine was prevented by theophylline (1 mM), a blocker of adenosine receptors, while the effect of ATP was not changed under these conditions. The selective blocker of A1 adenosine receptors, 8-cyclopentyl-1,3,dipropylxanthine (DPCPX; 0.1 microM), abolished the presynaptic action of adenosine but did not prevent the depressant effect of ATP. 5. The effects of ATP and adenosine (at nearly saturating concentration) were additive suggesting that these purines activated not only distinct receptors but also different intracellular signalling mechanisms. 6. In contrast to the hypothesis that at the neuromuscular junction ATP reduces transmitter release via enzymatic degradation to presynaptically active adenosine, our data suggest that ATP (through its own presynaptic receptors) directly inhibits ACh release. Thus, ATP and adenosine might be almost equipotent as endogenous prejunctional neuromodulators at the neuromuscular junction.

Acetylcholine↗