Experimental analysis of the relationship between charge movement components in skeletal muscle of Rana temporaria

Experiments were performed to ascertain whether the monotonic (q beta) and delayed (q gamma) components of non-linear charge in skeletal muscle membranes form a sequential system, or are the result of separate, independent processes. The non-linear capacitance studied in a large number of fibres increased with fibre diameter. This dependence was attributable to tetracaine-sensitive (q gamma) but not to tetracaine-resistant (q beta and q alpha) charge. The kinetics and total quantity of q gamma charge moving in response to voltage steps from varying pre-pulse potentials to a fixed probe potential remained constant despite variations in the size of the early q beta decay. The kinetics of the delayed (q gamma) charging current obtained from a single 20 mV depolarizing step were compared with the sum of the responses to two 10 mV steps adding to the same voltage excursion. The respective transients superimposed only if one of the 10 mV steps did not reach the voltage at which q gamma first appears. In the two preceding experiments, total charge was conserved. These results are consistent with separate and functionally independent q beta and q gamma systems of potential-dependent charge, with q gamma residing in the transverse tubules and q beta on surface membrane. The findings can be discussed in terms of a contractile 'activator' with a steep sensitivity to voltage that begins only with depolarization beyond a level close to the actual mechanical threshold.

Iatrogenic hiatal and diaphragmatic hernias

Seven patients with hernias occurring after Belsey hiatal hernia repair are described. These hernias were of two types. Four occurred through the hiatus, had the appearance of a parahiatal hernia, and were attributed to the failure to correct a shortened esophagus. In three patients the hernia occurred through a disrupted counterincision in the diaphragm. In the second group postoperative abdominal distension and possibly technical faults were incriminated. In the first group satisfactory repair was achieved by a Collis-Belsey gastroplasty and an antireflux procedure. In the second group reduction of the hernia and resuture of the diaphragm incision encompassing all layers corrected these life threatening hernias.

Charge movements near the mechanical threshold in skeletal muscle of Rana temporaria

Charge movement was investigated over a range of potentials close to the mechanical threshold in voltage-clamped frog skeletal muscle. The delayed (q gamma) component of the charging currents appeared with a time course lasting well over 100 ms at around -50 to -40 mV, but the currents became larger and faster with further depolarization. The slow charging current was investigated using a 10 mV probe step intercepting the time course of these currents. This procedure showed that the charging currents could last as long as 100-300 ms. The total charge was conserved when the charging current was small and prolonged. The results can be related directly to earlier findings concerning contractile activation of muscle by applied voltage steps to potentials near threshold ( Adrian , Chandler & Hodgkin, 1969).

Terminal sprouting of mouse motor nerves when the post-synaptic membrane degenerates

Injection of echothiophate, 4-aminopyridine and caffeine into the mouse calf produced necrosis in the endplate region of approximately 40% of soleus muscle fibres. Within two days terminal sprouting, as seen by zinc iodide/osmium tetroxide staining, had occurred at nearly a quarter of such endplates, but not at neighbouring intact ones. Almost half of these sprouts were greater than 50 microns in length. Terminal sprouting at degenerating endplates was also seen in identically treated silver-stained gluteus maximus muscles. Muscle degeneration caused by mechanical damage produced similar effects. In transverse sections of the gluteus maximus preparation, the terminals could be found within the necrotic muscle fibres, having penetrated the synaptic basal lamina. It is concluded that motor nerve terminals have an intrinsic tendency to grow, and are normally prevented from doing so by their formation of synapses with muscle fibres. Destruction of this relationship alone can cause terminal sprouting.

Time domain spectroscopy of the membrane capacitance in frog skeletal muscle

Dielectric spectra representing the frequency dependence of the complex permitivity at a range of depolarizations were obtained from voltage-clamped frog skeletal muscle membranes. This employed an analysis that derived the Fourier coefficients defining the capacitative transients to 10 mV steps as continuous functions of frequency, and so could examine closely the relevant frequencies at which non-linear components occurred. Non-linear capacitative components were identified through their appearance at lower frequencies than those of the linear components as obtained at the -85 mV control voltage, from spectra representing a logarithmic scale of frequencies. Permitivities from small depolarizing steps between about -75 and -50 mV gave single q beta dielectric loss peaks; the real permitivities declined monotonically with increasing frequency. Simple arc loci were obtained in the complex plane. With further depolarization, an additional q gamma loss peak at low frequencies and a resonant frequency in the real spectra occurred over a narrow voltage range around -45 mV. The complex loci then showed features implying an increased movement of charge not explicable through the simple effect of an electric field on a dielectric species. Spectra from small hyperpolarizing steps possessed only single dielectric loss peaks and real permitivities that declined monotonically with increasing frequency. However, in the complex plane, the loss tangents at the higher frequencies implied a population of two or more dielectric relaxations. The potential dependence of the frequency at maximum dielectric loss obtained from depolarizing steps showed a discontinuity at the onset of q gamma. In contrast, in hyperpolarizing responses, this dependence was smooth. The q beta relaxations obtained after q gamma was abolished by 1 mM-tetracaine gave dielectric spectra that were similar whether to depolarizing or hyperpolarizing potential steps. They gave single dielectric loss peaks and semicircular complex plane loci. The singularities in the dielectric spectra thus result from the q gamma charge movement component. They may reflect co-operative mechanisms that might also produce its steep voltage dependence and kinetics, and consequently those of the physiological processes it may control. These are discussed in terms of the mechanisms expected in allosteric proteins.

Experimental analysis of alternative models of charge movement in frog skeletal muscle

A series of pulse procedures was used to distinguish experimentally between a 'capacitative' (Schneider & Chandler, 1973) and a 'resistive' (Matthias, Levis & Eisenberg, 1980) model of 'charge movements' in skeletal muscle. A general condition describing the conservation of charge in a non-linear capacitor that was used as the basis for the experiments is derived in the Appendix. It was shown that earlier criteria concerning equality of 'on' and 'off' charge in response to large steps are insufficient to exclude resistive models. However, the capacitative, but not the resistive model successfully explained results bearing on charge conservation assessed through pulse procedures involving: (i) small, 10 mV voltage steps from a series of prepulse voltages, (ii) voltage steps to a fixed potential from a series of hyperpolarized voltages, (iii) pulse sequences incorporating a 'staircase' of voltage steps. It is concluded that the earlier use of 'on' and 'off' equality in response to large voltage steps is insufficient to exclude a resistive basis for the non-linear transient. However pulse procedures explicitly designed to distinguish the two models give results consistent with a capacitative model for the non-linear charge and at variance with a resistive one.

A quantitative description of the voltage-dependent capacitance in frog skeletal muscle in terms of equilibrium statistical mechanics

We present an analysis of experimental steady-state properties of charge movements in voltage-clamped frog skeletal muscle; by adopting an approach based on equilibrium statistical mechanics, detailed assumptions about the dynamics of the charge movement were avoided. Different components of the charge movements, as characterized by their sensitivities to local anaesthetics, were taken to correspond to different types of independent subsystem (integral membrane proteins). Quantitative agreement with the data for the q beta and q gamma components was obtained for the simplest subsystems, having two energy levels; however, q alpha required three (or more) energy levels. Each of the subsystems can be interpreted as having a charged group, minimum valency z, able to occupy two or more positions within the membrane. The tetracaine-sensitive q gamma charge can be described in terms of an ensemble of subsystems having z = 4.5, each occupying one of two levels whose free energies at zero applied voltage differ by 1.7 x 10(-1) eV. Likewise, the lidocaine-sensitive q beta has z = 1.0, free energy difference 1.9 x 10(-2) eV. However, the simplest model for the lidocaine-resistant q alpha involves a charge of valency 1.7 moving between three levels having relative free energies at zero applied voltage -9.7 x 10(-2), 0, and 2.1 x 10(-2) eV respectively, where the intermediate level 'sees' about 50% of the applied voltage.

Pharmacological separation of charge movement components in frog skeletal muscle

1. Charge movements to small 10 mV steps superimposed upon a wide range of closely spaced depolarizing voltage-clamp pulses were studied in frog skeletal muscles under different pharmacological conditions in hypertonic solutions.2. In control fibres, capacitance was strongly voltage-dependent, especially between potentials of -60 and -20 mV, confirming earlier work. There was a sharp increase in capacitance at around -50 mV. The dependence of non-linear charge on potential was asymmetrical and saturated at around 25 nC/muF.3. The presence of tetracaine abolished the ;hump' in the non-linear transients, which became simple monotonic decays. The dependence of capacitance upon potential was reduced. The maximum available amount of non-linear charge fell to 10 nC/muF.4. The presence of lidocaine abolished both the ;hump' as well as the monotonic part of the non-linear transients. This resulted in capacitance falling with depolarization from -85 mV.5. Comparing the steady-state properties of the non-linear charge under the different pharmacological conditions made it possible to deduce empirically the following components:(i) A lidocaine-resistant component (q(alpha)), which was responsible for the fall in observed capacitance with depolarization from the control voltage.(ii) A component resistant to tetracaine yet abolished by lidocaine (q(beta)). This possesses quasi-exponential kinetics, and a maximum charge of about 20 nC/muF.(iii) A component abolished by both lidocaine and tetracaine (q(gamma)), which possesses a maximum charge of 15 nC/muF. This has complex kinetics, and its steep dependence upon voltage resembles the potential-dependence of the development of tension in skeletal muscle.

Membrane capacitance in hyperpolarized muscle fibres

1. Voltage clamp experiments on muscle fibres compared transients to 10 mV steps at hyperpolarized voltages between VT = -100 to -185 mV with controls obtained at VC = -85 mV. 2. Membrane capacitance fell by 15%, 13% and 4.5% per 100 mV hyperpolarization fro -85 mV in hypertonic low chloride, hypertonic high chloride and isotonic high chloride-containing solutions respectively. 3. The charge moved by the 'on' and 'off' parts of the applied step was equal over the voltages studied. This suggests that the changes were capacitative rather than ionic in origin. The changes could not be explained in terms of the cable properties of the transverse tubular system. They may therefore reflect non-linear capacitance in the muscle membrane itself. 4. Subtracting control transients at -85 mV from transients obtained at different voltages gave monotonically decaying charge movements. In the frequency domain, these charge movements possessed real and imaginary permittivities resembling those of a 'Debye' particle. 5. It is concluded that muscle membranes have non-linear capacitances even at voltages far hyperpolarized to those in which familiar voltage-dependent processes occur.

Dielectric components of charge movements in skeletal muscle

1. Voltage clamp experiments measured transients from 10 mV steps applied about different membrane potentials, VT. Their analysis employed the Fourier transform relationship between dielectric spectra of permittivity as a function of frequency, and the step transient admittance, as well as established methods. 2. The membrane capacitance measured between -85 mV and about -50 mV rose monotonically and was associated with simple decaying transients in both 'on' and 'off' steps. At more depolarized potentials the capacitance increased sharply and was associated with a charging current of complex form, before falling again beyond the transition potential. 3. Step-transient responses for dielectric analysis were sampled in the above voltage range. Dielectric spectra of the non-linear transients were obtained by subtracting Fourier transforms of transients at VC = -85 mV from test transforms at VT. 4. The imaginary transform coefficients represent a spectrum of dielectric loss against frequency. These showed two non-linear components. The q beta component formed a broad peak, when charge movements were simple monotonic decays. A sharp low-frequency q gamma peak became superimposed at particular voltages when charge-movement kinetics became complex. 5. In contrast, 'off' transients were simple monotonic relaxations. Their transforms showed only one dielectric loss peak, whose frequency was relatively voltage-independent when q gamma occurred in 'on' transforms. 6. Both altering holding potential from VH = -85 to -50 mV and adding 1 mM-tetracaine to the bathing solution reduced the dependence of capacitance on voltage. The non-linear polarization currents became simple monotonic relaxations at both the beginning and end of the voltage step. 7. It is concluded that charge movements are composed of at least two components: q beta, and the tetracaine and voltage-inactivated q gamma. Any causal relationship between q beta and q gamma and the membrane processes they might underlie would be expected to be complex.

Effects of local anaesthetics on the relationship between charge movements and contractile thresholds in frog skeletal muscle

1. Charge movements to 10 mV steps at different potentials were studied in voltage-clamped frog skeletal muscle fibres in isotonic solutions that minimized ionic currents, under different pharmacological conditions. The earliest onset of detectable mechanical movement ('threshold') was assessed visually under magnification. 2. Charge movements in isotonic solutions were similar to those reported in hypertonic solutions, under identical pulse procedures. 3. In the absence of local anaesthetics, threshold occurred at a mean membrane potential of -55 mV, after the movement of 4.0 nC/muF of non-linear charge and when the membrane capacitance approximated values that corresponded to the onset of the 'Qgamma' charge movement component. 4. Lidocaine shifted the threshold in the hyperpolarizing direction to -62 mV, and reduced the amount of non-linear charge needed to reach threshold to 1.4 nC/muF. 5. The presence of tetracaine shifted threshold in the depolarizing direction to -39 mV, and more than doubled the amount of non-linear charge that had to move to reach threshold to 10.8 nC/muF. Much of this increase was attributed to the Qgamma component of charge movement. 6. It is concluded that more non-linear charge is required to initiate mechanical movement when calcium release by sarcoplasmic reticulum is inhibited by tetracaine, whereas less charge is so required when calcium re-uptake is being inhibited by lidocaine. Assuming earlier interpretations of the strength duration curve, this is consistent with charge movement preceding, rather than being a consequence of calcium release.

The transmission of leprosy in man

Existing clinical, scientific, and epidemiological knowledge on the mode of transmission of human leprosy is reviewed under the following headings: a. The release of viable organisms from the host into the environment. b. The presence of viable organisms so released into the environment. c. Entry into the new human host and distribution within the body. d. Production of clinical illness. It is concluded that much of the published evidence deals with one, or rather few, parameters, whose relationship to the overall scheme of transmission is uncertain. Although it is beyond doubt that most leprosy bacilli emerge from the nose and nasal secretions, probably entering the environment in droplets, little is known of their mode of survival in the environment or their entry into the new host. Existing data certainly does not provide a full "model" of leprosy transmission, and it is suggested that further work attempting to clarify the relative importance of the component events in transmission may have to rely increasingly on epidemiological methods. It also emerges that consideration of the immunological factors bearing on whether or not infections causes clinical illness is important in elucidating the mechanism of leprosy transmission. Thus even the most "applied" and practical of problems must eventually turn to the realm of "pure" research for a definitive solution.

Thiocardenolides II: synthesis and pharmacological evaluation of 3beta-thioacetyl-14beta-hydroxy-5beta-card-20(22)-enolide

The synthesis of a 3beta-thioacetylcardenolide is described. The thioacetate exhibited effects similar to those seen with digitoxigenin acetate on the isolated frog and guinea pig hearts at 1 X 10(-7) dilution. In the intact rat heart, the lethal dose was 5 mg/kg for the thioacetate and 2.5 mg/kg for digitoxigenin acetate. The thioacetate inhibited sodium- and potassium-activated adenosine triphosphatase to the same extent as digitoxigenin, but it was somewhat less inhibitory than digitoxigenin acetate.

The open jejunum: a patch for large duodenal defects

A practical solution is presented for the difficult problem posed by a large duodenal defect in a very sick patient. A segment of jejunum opened along its antimesenteric border was applied as a mucosally lined patch, with a favorable result.

Thiocardenolides I: synthesis and biological actions of 3beta-thiocyanato-14beta-hydroxy-5beta-card-20(22)-enolide

The synthesis of a 3beta-thiocyanatocardenolide is described. The compound exhibited about 0.1 times the cardiotonic effect of digitoxyigenin in the isolated frog heart preparation. At a dosage of 20 mg/kg in the intact rat, it elicited ECG changes similar to those seen with a 10-mg/kg dose of digitoxigenin. Studies also revealed the new cardenolide to be a reversible inhibitor of sodium- and potassium-activated adenosine triphosphatase.

Interactions of tricyclic antidepressants and barbiturates in barbiturate-tolerant and nontolerant rats

Pretreatment of rats with tricyclic antidepressants, imipramine, desipramine, amitriptyline and nortriptyline, at two doses (5 and 25 mg/kg) 20 minutes before administration of barbiturate markedly reduced the latent period of the response to barbital and prolonged the sleeping time induced by pentobarbital (PB) and barbital. The effects were dose-dependent. The prolonged sleeping time produced by PB was associated with decreases in the rates of disappearance of PB from the brain and plasma. The effect of tricyclic antidepressants on PB hypnosis in PB-tolerant and nontolerant rats was apparently not related to change in central nervous system (CNS) sensitivity to PB, since at the time of awakening there were no significant differences in the concentrations of unmetabolized PB in either the plasma or brain of tricyclic antidepressant-treated animals as compared to controls. As barbital is not metabolized, potentiation of barbital hypnosis by tricyclic antidepressants must be attributable to a direct effect on CNS rather than on liver microsomal enzymes. Direct evidence was provided by the findings that amitriptyline accelerated the brain uptake of barbital and that amitriptyline-treated animals lost and recovered the righting reflex at brain barbital levels lower than those of controls. Rats made tolerant to the hypnotic effect of barbital also became tolerant, in varying degrees, to the hyposis-prolonging properties of tricyclic antidepressants. It is concluded that tricyclic antidepressants prolong PB sleeping time in PB-tolerant and nontolerant rats by inhibiting its biotransformation in the liver. The action of tricyclic antidepressants to prolong the hypnotic action of barbital in normal rats is related to their direct effects on CNS sensitivity to barbital, but such effects are makedly diminished after animals become tolerant to barbital.

Effect of acylation with eleostearic acids on the monoamine oxidase inhibitory potency of some hydrazine antidepressants in mice

The effect of incorporation of an eleostearoyl group into molecules of aralkylhydrazines on their monoamine oxidase inhibitory potency was investigated in vitro and in vivo. The results showed that on a molar basis the hydrazides possessed an in vitro potency lower than and an in vivo potency and acute toxicity comparable to those of the corresponding aralkylhydrazines. The sequence of the relative potency of aralkylhydrazines and their hydrazides was similar. The overall pharmacological profile indicated that these aralkylhydrazines retained their monoamine oxidase inhibitory properties when the free hydrazine nitrogen was acylated with an eleostearoyl group.

Collaborative Study of the Spectrophotometric Determination of Phosphatase Activity in Milk Utilizing a New Alkaline Phosphatase Assay System

A quantitative procedure (modified new method) has been studied that employs phenolphthalein monophosphate as the substrate and dialysis of released phenolphthalein followed by subseqvient measurement of the dialysate in a spectrophotometer at 550 nm. Nine collaborators evaluated 6 unknown samples of milk containing various levels of rawmilk, in triplicate, by the modified new method and the Scharer modified spectrophotometric method. Analysis of variance revealed that the random error of the modified new method was almost twice that of the Scharer technique, while the systematic error of the modified new method was only about ¼ that of the latter method. Two-sample charts indicated that the systematic error of the modified new method was less than that of the Scharer method; this was verified by a statistical comparison which showed that the total analytical error was much lower for the modified new method. A linear relationship was found between the 2 methods by 5 of the collaborators; the correlation coefficients ranged from 0.993 to 0.999. Based on these results, the method has been adopted as official first action for the analysis of milk.