[Growth inhibition and mechanism of cetyltrimethyl ammonium chloride on Chlorella vulgaris]

Growth inhibition of cetyltrimethyl ammonium chloride (CTAC), a cationic surfactants, on Chlorella vulgaris was investigated at batch culture in laboratory. Furthermore, the corresponding mechanisms were studied by the determination of absorption capacity, Zeta potential, activity of acid phosphatase and ultrastructure of algae. Results show that the growth inhibition by CATC is enhanced with its concentration increasing from 0.1 mg/L to 1 mg/L, and 96 h-EC50 of CTAC is 0.18 mg/L. In the presence of 0.3 mg/L CTAC in 8 d, the inhibition efficiency of biomass reaches 70.7%. Meanwhile, the absorption of nitrogen and iron is inhibited 83.9% and 86.2% respectively with Zeta potential of algae cell increasing from -12.5 mV to -6.7 mV. Furthermore, the relative activity of acid phosphatase declines to 23.1% at the same time. Plasmolysis, distortion of pyrenoid and swelling of lysosome is observed in the cell. Above phenomena indicates that CTAC increases the Zeta potential of algae cell and thus inhibites the absorption of nitrogen and iron. In addition, CTAC may affect the metabolism of phosphorus and change the ultrastructure of algae cell.

Triethylcholine compared with other substances affecting neuromuscular transmission

Triethylcholine (triethyl-2-hydroxyethyl ammonium) has been compared, in its actions on neuromuscular transmission, with the motor end-plate blocking drugs tubocurarine and decamethonium, with the anticholinesterase neostigmine, and with the closely related drug tetraethylammonium. The experiments were carried out on conscious rabbits and mice, on the tibialis anterior muscle of cats under chloralose anaesthesia and on the isolated phrenic nerve-diaphragm preparation of the rat. Anticholinesterase activity was determined manometrically using the Warburg apparatus. Triethylcholine possessed a slight curare-like action, but this effect was shown to be too weak and transient to contribute to the slowly developing and long-lasting transmission failure which occurs selectively in frequently excited nervemuscle preparations and in exercised conscious animals. It was confirmed that the site of the blocking action of triethylcholine was pre-junctional. Triethylcholine often produced a slight potentiation of the contractions before blocking them. This effect was not due to a depolarizing or an anticholinesterase action, and it was concluded that the slight initial facilitating action of triethylcholine on neuromuscular transmission was due to an increase in the quantity of acetylcholine released by the nerve impulse. Tetraethylammonium was much more powerful than triethylcholine in this respect. The pre-junctional transmission failure produced by triethylcholine could not be explained simply on the basis that an initial excessive release led to exhaustion of transmitter.

[A nondepolarizing muscle relaxant with rapidly developing and short-term action]

The pharmacological properties of the new nondepolarizing myorelaxant IEM-1213 and of its mixture with tercuronium were studied in experiments on anesthetized cats. Intravenous infusion of a blocking dose of IEM-1213 did not cause a change in the level of arterial pressure and blockade of the sympathetic ganglia but induced blockade of the heart muscarine receptors. The effect of IEM-1213 develops more rapidly and lasts for a shorter time than that of dithylin. Intravenous infusion of a mixture of IEM-1213 and tercuronium constituting 35 and 60% of the blocking dose of the former and, respectively, 35 and 20% of the blocking dose of the latter causes an effect similar in the time of its development to that of intravenous infusion of a total dose of IEM-1213 alone.

Dimensions of neuronal nicotinic acetylcholine receptor channel as estimated from the analysis of the channel-blocking effects

Acetylcholine-induced membrane currents and excitatory postsynaptic currents (EPSCs) were recorded from the neurons of rat superior cervical ganglion (SCG) using the whole-cell patch clamp and the two-electrode voltage clamp techniques, correspondingly. The EPSC decay was bi-exponential, with fast and slow components characterized by time constants 5.5 +/- 0.5 msec and 20.4 +/- 1.2 msec (mean +/- SEM; n = 23), respectively. Blocking of these currents by a series of newly synthesized bis-cationic ammonium compounds, the pentamethonium and pentaethonium derivatives, was analyzed. Blocking effects were due to a block of nicotinic acetylcholine receptor (nAChR) open channel, with mean blocker binding rate constants for the fast component three to five times higher than those for the slow component. Dimensions of a nAChR ionic channel were deduced from a relationship between blocking activity of the compounds and the size of the projections of their three-dimensional molecular models on the neuronal membrane plane. The results suggest that there are two populations of nAChRs in rat SCG neurons; while these polulations differ in the rate constants of the binding by the blocker to their open channels, they exhibit similar channel diameter, 11.8 A, at the level at which the blockers bind to the channel.

The channel-blocking action of methonium compounds on rat submandibular ganglion cells. 1983

The effects of drugs of the polymethylene bis-trimethylammonium (methonium) series on the characteristics of the synaptic currents (e.s.cs) recorded from voltage-clamped rat submandibular ganglion cells have been studied. The drugs studied were from C4 to C10 (decamethonium).

All of the drugs except C4 shortened the initial decay phase of the e.s.c.; C9 and C10 produced an additional slowly decaying component. These effects were interpreted in terms of an open channel block mechanism, the calculated rate constants for association with the open channel at − 80 mV being fairly similar (5.9 × 10⁶ to 18.1 × 10⁶M⁻¹ s⁻¹) for all of the compounds except C4, which had no effect on the e.s.c. decay.

All of the compounds produced use-dependent block when tested with short trains of stimuli at 10 Hz, or with trains of ionophoretic pulses of acetylcholine, consistent with their channel blocking property. Tubocurarine had a similar effect, but not trimetaphan or mecamylamine.

Recovery from use-dependent block with short chain methonium compounds, up to C8, was very slow in the absence of agonist, being incomplete even after several minutes. With C9 or C10 or tubocurarine, recovery from use-dependent block was complete within a few seconds. With C6 recovery in the absence of agonist was unaffected by membrane potential, but could be accelerated by applying acetylcholine with the cell depolarized to − 40 mV. This persistent block was ascribed to the ability of the blocking molecule to become trapped by closure of the channel. With C9 and C10 it is assumed that their presence inhibits channel closure, so they can escape without the help of agonist.

When use-dependent block is avoided by leaving the ganglion unstimulated during equilibration with the blocking drug, the first e.s.c. elicited shows no appreciable reduction of amplitude, though with C6, C7 or C8 subsequent responses elicited at 0.1 Hz become progressively more blocked.

Even at 1 Mm, C6 does not prevent acetylcholine from opening ionic channels.

It is concluded that all of the effects on e.s.c. amplitude can be interpreted in terms of channel block, there being no evidence of any receptor blocking action.

Interactions of agonists with an allosteric antagonist at muscarinic acetylcholine M2 receptors

The interaction of heptane-1,7-bis(dimethyl-3'-phthalimidopropylammonium bromide) (C7/3'-phth), with several agonists, was investigated at the muscarinic M2 receptor in guinea-pig left atria. C7/3'-phth shifted concentration-response curves for the agonists, carbachol, oxotremorine-M and (+)-cis-dioxolane, to the right in a parallel fashion. Arunlakshana-Schild regressions of the data yielded slopes significantly different to unity, suggesting non-competitive antagonism. Non-linear regression analysis, using an equation based on allosteric modulation, gave quantitative estimates of co-operativity (alpha values) and the dissociation constant of C7/3'-phth (KB). In all cases, the KB estimates for C7/3'-phth were not significantly different. Increasing the carbachol contact time 10-fold did not significantly influence the KB or the alpha value obtained with C7/3'-phth. Changing from Krebs to Tyrode solution did not significantly alter the KB for C7/3'-phth, although alpha values obtained were consistently lower in Tyrode solution, suggesting that the allosteric action may be sensitive to buffer composition. A 4-fold higher degree of negative, heterotropic co-operativity between C7/3'-phth and agonists than between C7/3'-phth and competitive antagonists was also found.

Architecture of the neuronal nicotinic acetylcholine receptor ion channel at the binding site of bis-ammonium blockers

Structure-activity relationships of 56 pentamethylenbis-ammonium compounds, the blockers of the neuronal nicotinic acetylcholine receptor (nAChR) ion channel, have been studied to estimate the cross-sectional dimensions of the channel pore. The cat superior cervical sympathetic ganglion in situ and isolated guinea pig ileum were used to evaluate the potency of the compounds to block ganglionic transmission. Minimum-energy conformations of each compound were calculated by the molecular mechanics method. A topographic model of the binding site of the blockers was proposed. It incorporates two narrowings, a large and a small one. The small narrowing is located between the large one and the cytoplasmic end of the pore. The cross-sectional dimensions of the large and small narrowings estimated from the dimensions of the blockers are 6.1 x 8.3 A and 5.5 x 6.4 A, respectively, the distance between the narrowings along the pore being approximately 7 A. Most potent blockers would occlude the pore via binding to the channel at the levels of both narrowings. Less potent blockers are either too large or too small to bind to both narrowings simultaneously: large blockers would occlude the pore at the level of large narrowing, while small blockers would pass the large narrowing and occlude the pore at the level of small narrowing only. A comparison of the topographic model with a molecular five-helix bundle model of nAChR pore predicts Serine and Threonine rings to be the most probable candidates for the large and small narrowings, respectively.

An angiotensin-independent, hypotension-induced, sodium appetite in the rat

We have investigated the role of peripheral angiotensin II in the generation of hypotension (without hypovolaemia)-induced salt intake in rats treated with an IV infusion of the quaternary ammonium peripheral ganglion blocker Penthonium. At a dose of 15.4 mg/ml this compound induces a significant decrease in blood pressure from the beginning of the infusion. Intake of 3% NaCl was significantly increased only on the first day (1.7 +/- 0.3 ml, n = 7, p < 0.01 vs. the day before) and this induced salt appetite was not altered (2.3 +/- 0.9 ml, n = 7, p < 0.05 vs. the day before) by intracerebroventricular administration of a nonpeptide AII-type 1 receptor specific antagonist, Losartan, at a dose known to block AII-induced drinking (250 ng). We conclude from these results that AII liberated in response to the hypovolaemia is probably not responsible for the subsequent induced intake of NaCl which may be the result of a direct barosensitive input to the salt appetite centers of the brain.

Assessment of the allosteric interactions of the bisquaternary heptane-1,7-bis(dimethyl-3'-phthalimidopropyl)ammonium bromide at M1 and M2 muscarine receptors

The interaction of the allosteric muscarine receptor antagonist heptane-1,7-bis(dimethyl-3'-phthalimidopropyl)ammonium bromide (C7/3-phth) with M1 muscarine receptors in rat cerebral cortex and rabbit vas deferens and M2 muscarine receptors in guinea pig atria was investigated. In atria, C7/3-phth completely inhibited the dissociation of N-[3H]methylscopolamine ([3H]NMS) in the presence of excess unlabeled NMS and slowed the washout of NMS in functional experiments. C7/3-phth also produced supra-additive inhibition of the negative inotropic effects of carbachol when combined with NMS. This latter phenomenon was less pronounced when pirenzepine (PZP) was used in place of NMS. Cooperativity factors for the interaction of C7/3-phth with other antagonists were obtained by fitting the data to a theoretical model for interaction between an agonist, a competitive antagonist, and an allosteric antagonist. The values obtained indicate that C7/3-phth exhibits a greater degree of negative heterotropic cooperativity with PZP than with NMS at the M2 muscarine receptor. In the rat cerebral cortex, C7/3-phth slowed the dissociation of [3H]NMS and [3H]quinuclidinyl benzilate from the M1 receptor to the same extent but appeared not to affect the dissociation of [3H]PZP. In rabbit vas deferens, the inhibitory effect of the combination of C7/3-phth and atropine on the responses to McN-A-343 at the M1 receptor was more pronounced than that of the combination of C7/3-phth and PZP. Comparison of the findings for both central and peripheral M1 receptors with those obtained for the cardiac M2 receptor suggests that the allosteric interaction of C7/3-phth is less evident at the M1 receptor, particularly in the case of PZP.

In search of new neuromuscular blocking drugs with quick onset and short duration of effect

In experiments using cats the neuromuscular blocking effect of bis-trimethylammonium derivatives having a non-depolarizing mode of action had an onset of action shorter than that of their triethylammonium analogs. The difference in equieffective doses of neuromuscular blocking agents administered intravenously or intraarterially was less in the case of compounds with rigid molecules than that with flexible molecules. Results indicate that a more considerable portion of flexible substance absorbs on the 'site of loss' in blood vessels than for rigid compounds. This suggests that rigid molecules promote a faster achievement of effective concentration of a neuromuscular blocking agent at synapses. Proceeding from these data a bis-trimethylammonium derivative with a rigid molecule, IEM-1213, was synthesized and studied in cats.

[The conformational aspects of the interaction of the cholinesterases of Pacific Ocean squid and vertebrates with derivatives of polymethylene bis(trimethylammonium)]

Conformational properties of a series of polymethylenebis (trimethylammonium) derivatives [formula: see text] (n = 4-10), cholinesterase reversible inhibitors, were studied by molecular mechanics method. Conformation-activity relationships between these inhibitors and human erythrocyte acetylcholinesterase, horse plasma butyrylcholinesterase, cholinesterases from the brain of the frog Rana temporaria and from visual ganglia of the squid Todarodes pacificus were investigated by correlational methods. Differences in mechanisms of antienzyme actions were determined.

Characterization of the muscarine receptor subtype on sympathetic nerve endings in the rat caudal artery

The prejunctional muscarine receptor on sympathetic nerves in the rat caudal artery was characterized using several selective antagonists. The inhibitory response of carbachol on vasoconstriction elicited by sympathetic nerve stimulation was antagonized by benzhexol (trihexyphenidyl; pKB 7.1), heptane-1,7-bis(dimethyl-3'-phthalimidopropyl ammonium bromide) (C7/3-phth; pKB 6.5) and hexahydrosiladifenidol (HHSiD; apparent pKB 6.0). These pKB values suggest that the receptor most closely resembles the muscarine M2 receptor subtype rather than the muscarine M1, M3 or M4 receptor subtypes.

Actions of a series of bisquaternary compounds on nicotinic acetylcholine receptors in insects: ligand binding and electrophysiological studies

A series of bisquaternary ammoniums, with chain lengths of between 4-12 carbon atoms (C4-C12), have been tested for their ability to block acetylcholine-induced responses in the fast coxal depressor motor neurone (Df) of the cockroach (Periplaneta americana) and to displace [125I]alpha-bungarotoxin from membrane preparations of the CNS of the cockroach. The physiological studies showed that tetramethonium was inactive, whereas hexa-, octa- and dodecamethonium showed an enhanced ability to block acetylcholine-induced responses as the chain length increased. Decamethonium resulted in a slight increase in acetylcholine-induced depolarizations. Ligand binding studies showed that the ability of the compounds to inhibit the specific binding of [125I]alpha-bungarotoxin increased with size from C4-C12. The results show that neuronal nicotinic receptors in insects differ in aspects of their pharmacology from both the major subclasses of nicotinic receptors of vertebrates.

Ionic control of the size of the vesicle matrix of beige mouse mast cells

Isolated matrices of the giant secretory vesicles of mast cells of the beige mouse were reliably produced by the osmotic lysis of isolated vesicles. These matrices maintained their form, and their sizes were easily measured using Nomarski optics. The size of the matrix depended on the ionic composition of the bathing solution. The physiologically relevant ions, histamine and serotonin, contracted the matrix. Multivalent cations condensed the matrix relative to univalents. Ag+, acid pH (below 5), and basic pH (above 9) expanded the matrix. In the presence of 10 mM histamine, lowering the pH from 9 to 5 contracted the matrix more than can be attributed to the pH-dependent matrix contraction in zero histamine. The nontitratable organic cation, dimethonium, contracts the matrix with little effect of pH in the range of 5-9. These results suggest that histamine acts as a matrix contractor in the divalent form. The dose-response (contraction) relation for histamine was gradual from micromolar to 316 mM (millimolar) histamine. Experiments with mixtures of histamine and sodium show antagonistic effects on the matrix but are inconsistent with either a model where ions compete for identical sites or a parallel model where ions interact with separate independent sites. In vigorous histamine washoff experiments, the half time for vesicle expansion in 10(-4) M pH buffer was approximately 4 s; in isotonic NaCl solution, it was 0.5 s. When 1 M histamine was presented to closely apposed matrices, fusion resulted. The matrix material returned to its initial shape after being mechanically deformed with a glass probe. These results suggest that the matrix size is controlled by its ion exchange properties. The matrix expansion can quantitatively account for the vesicular size increase observed upon exocytosis (as a postfusional event) and the osmotic nonideality of intact vesicles. The mechanical expansion is probably significant in the widening of the exocytotic pore and the dispersal of the vesicular contents.

A simple spectroscopic method for studying erythrocyte ghost resealing

A novel spectroscopic method is described for following the kinetics of resealing of hemolysed erythrocyte ghosts. The procedure is based on the broadening of the EPR spectrum of nitroxyl radicals by paramagnetic ions. The method is used to study the effect of Ca2+, Mg2+ and dimethonium ion on the kinetics of resealing.

Selective inhibition of responses to carbachol and McN-A-343 in the rabbit vas deferens

1. The effect of several selective muscarine receptor antagonists were evaluated on the responses of carbachol (CCh) and McN-A-343 (McN) during sympathetic nerve stimulation in the rabbit vas deferens. 2. The muscarine M1 receptor antagonist pirenzepine exhibited similar apparent pKB values for antagonism of the prejunctional inhibitory response of either CCh (pKB, 8.2) or McN (pKB, 8.5) on sympathetic nerve stimulation. 3. The muscarine M2 receptor antagonists, pancuronium and the bisalkyl ammonium compound 'C7/3-phth' were selective inhibitors of the postjunctional facilitatory response produced by CCh on sympathetic nerve stimulation. They were also 17- and three-fold, respectively, less potent against the inhibitory responses of McN on sympathetic nerve stimulation. The apparent pKB value of pancuronium on the inhibitory response produced by CCh did not differ significantly (P greater than 0.05) from that using McN. A similar finding was made for C7/3-phth. 4. Selective blockade of the inhibitory response to CCh with pirenzepine (0.03 or 0.5 mumol/L) did not significantly (P greater than 0.05) modify the apparent pKB value for pancuronium on the facilitatory response of CCh. 5. Selective blockade of the facilitatory response to CCh with a low concentration of pancuronium (0.5 mumol/L) did not significantly (P greater than 0.05) modify the apparent pKB value for pancuronium (30 mumol/L) on the inhibitory response of CCh. 6. It is suggested that CCh and McN activate the same prejunctional M1 muscarine receptor and that pancuronium is the most selective of the muscarine M2 receptor antagonists presently tested in this preparation for distinguishing between muscarine M1 and M2 receptors.

Sialic acid and the surface charge associated with hyperpolarization-activated, inward rectifying channels

The whole-cell configuration of the patch-clamp technique was used with cultured pacemaker cells from the rabbit sinoatrial node to test the hypothesis that sialic acid residues (NANA) constitute much of the negative surface charge associated with hyperpolarization-activated, inward rectifying channels. Activation-voltage relationships (between -70 and -140 mV) were determined for hyperpolarization-activated (inward rectifying) current (i(f)). Addition of 10 mM Ca2+ shifted the half-activation potential (V 1/2) from -89.5 +/- 0.9 mV to -77.9 +/- 2.6 mV (P less than 0.01), confirming the presence of negative fixed charges on the myocytes after 3 to 5 days in culture. Addition of 20 mM dimethonium, an organic divalent cation that "screens" but does not bind to negative surface charge, shifted V 1/2 from -86.8 +/- 1.4 mV to -75.0 +/- 1.7 mV (P less than 0.001) without affecting the amplitude of the current. In contrast, 10 mM Ca2+ reduced the amplitude of i(f) significantly. Incubation of cells with a highly purified preparation of neuraminidase (0.1-2.0 U/ml, 1 hr, 37 degrees C), an enzyme that selectively removes NANA from glycoproteins and glycolipids, failed to alter V 1/2 or the amplitude of i(f) significantly. Pretreatment of cells with neuraminidase (1.0 U/ml, 1 hr, 37 degrees C) failed to alter the positive shift of V 1/2 produced by dimethonium. The results suggest that NANA does not constitute the negative surface charge associated with hyperpolarization-activated, inward rectifying channels.

Characterization of the antimuscarinic effect of heptane-1,7-bis-(dimethyl-3'-phthalimidopropyl ammonium bromide)

The effect of heptane-1,7-bis-(dimethyl-3'-phthalimidopropyl ammonium bromide) (C7/3'-phthalimidopropyl), an alkane bisquaternary compound with muscarinic receptor blocking activity was studied in guinea-pig atria and ileal longitudinal muscle. C7/3'-phthalimidopropyl was a more potent inhibitor of atrial muscarinic receptors, the cardioselectivity being ca. 32-fold. Previous studies in guinea-pig atria have shown that its antimuscarinic effect was of an allosteric nature. In ileal longitudinal muscle C7/3'-phthalimidopropyl (3 to 100 microM) appeared to behave in a competitive manner towards carbachol but the combination of atropine or homatropine with C7/3'-phthalimidopropyl produced a supra-additive inhibitory effect on the responses to carbachol. In both atria and ileal longitudinal muscle homogenates, C7/3'-phthalimidopropyl also slowed the dissociation rate of [3H]QNB suggesting an allosteric mechanism. In binding studies using either [3H]QNB or [3H]oxo-M, C7/3'-phthalimidopropyl recognized two binding sites in atria and ileum. In both tissues, C7/3'-phthalimidopropyl bound with high affinity (ca. 30-70 nM) to 60-85% of the sites and with low affinity (ca. 1-9 microM) to the remaining sites. Correlation of these affinity constants with the dissociation constants obtained in functional studies in the two tissues is discussed.

Cationic interactions with Na+-H+ exchange and passive Na+ flux in cardiac sarcolemmal vesicles

Na+-H+ exchange and passive Na+ flux were investigated in cardiac sarcolemmal vesicles as a function of changing the ionic composition of the reaction media. The inclusion of EGTA in the reaction medium resulted in a potent stimulation of Na+ uptake by Na+-H+ exchange. It was found that millimolar concentrations of Mg2+ and Li+ were capable of inhibiting Na+-H+ exchange by 80%. One mechanism by which these ions may inhibit intravesicular Na+ accumulation by Na+-H+ exchange is via an increase in Na+ efflux. An examination of Na+ efflux kinetics from vesicles pre-loaded with Na+ revealed that Na+, Ca2+, Mg2+ and Li+ could stimulate Na+ efflux. Na+-H+ exchange was potently inhibited by an organic divalent cation, dimenthonium, which screens membrane surface charge. This would suggest that Na+-H+ exchange occurs in the diffuse double layer region of cardiac sarcolemma and this phenomenon is distinctly different from other Na+ transport processes. The results in this study indicate that in addition to a stimulation of Na+ efflux, the inhibitory effects of Mg2+, Ca2+ and Li+ on Na+-H+ exchange may also involve a charge dependent screening of Na+ interactions with the membrane.

The role of calcium at the sarcolemma in the control of myocardial contractility

The importance of sarcolemmal-bound calcium (Ca) in the control of contraction in mammalian myocardium is indicated by the following results. The curve that relates [Ca]o (from 50 microM to 10 mM) to force development and that which relates [Ca]o to Ca bound to a highly purified sarcolemmal fraction are superimposable. The ability of a series of cations to uncouple excitation from contraction is the same as their relative ability to displace Ca from the sarcolemma. Dimethonium, which specifically displaces cation from the diffuse double layer of the cellular surface, has little effect on contractile force. This indicates that the Ca actually bound to the sarcolemma is the surface Ca important in contractile control. Polymyxin B, a highly charged cationic amphiphilic peptidolipid, specifically competes for Ca-binding sites on anionic and zwitterionic phospholipid. It is a potent displacer of Ca from myocardial cells and purified sarcolemma and a potent uncoupler. Phospholipase D cleaves the nitrogenous base from sarcolemmal phospholipid with production of anionic phosphatidic acid. Phospholipase D treatment increases Ca bound to cells and purified sarcolemma and increases force development of ventricular tissue from both neonatal rat and adult rabbit. Insertion of charged amphiphiles in the sarcolemma as phospholipid analogues modulate interaction of Ca with the sarcolemma, e.g., anionic dodecylsulfate increases Ca bound to sarcolemmal vesicles by more than 80% and increases force development in rabbit papillary muscle by 100%. The effect of pH variation on Ca binding to phospholipid extracted from sarcolemma indicates that phospholipid accounts for at least 75% of the binding. The current model proposes a two-site control of Ca binding.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of dodeconium on carbohydrate metabolism]

It is shown in experiments on albino rats that dodeconium in therapeutic doses stimulates the glycolytic processes and inhibits the aerobic oxidation of glucose in the pentose phosphate cycle as well as the final stages of gluconeogenesis. Such an action of dodeconim leads to hypoglycemia and normalizes many indices of carbohydrate metabolism in alloxane diabetes.

Dopamine, noradrenaline and isoprenaline: secretory and electrophysiological effects in vitro on mouse pancreas

The amylase release from mouse pancreatic fragments was studied after dopamine (DA), and alpha- or beta-sympathomimetic agonist application. The electrical parameters of the acinar cell membrane were also monitored. Both DA (from 5 X 10(-6) to 10(-4) M) and beta-stimulants (isoprenaline from 5 X 10(-6) to 5 X 10(-5) M; noradrenaline from 3 X 10(-4) to 10(-3) M) evoked an increase in amylase release, while noradrenaline in alpha-receptor stimulating doses failed to have any effect. The stimulatory effect of DA was blocked by ganglion blockers (Arfonad 10(-5) M; pentamethonium 3 X 10(-5) M) in a competitive manner and a dual antagonism was observed with atropine (10(-7) M, 10(-9) M). An alpha-receptor antagonist (phentolamine 10(-5) M) and a beta-receptor antagonist (propranolol 10(-5) M) had no influence on the dopamine response. Moreover, the DA-induced stimulation was dependent on the presence of extracellular calcium. Perfusion with 10(-4) and 10(-3) M-DA or local application (from 77 micrograms to 4.3 mg), resulted in marked membrane depolarization with diminution of the input resistance. This effect was blocked by atropine (10(-5) M) and pentamethonium (10(-4) M), but not by propranolol (10(-5) M) or phentolamine (10(-5) M). The isoprenaline- (IP) and noradrenaline- (NA) induced increase in amylase release was competitively blocked by propranolol (10(-5) M) but not by phentolamine (10(-5) M). Atropine caused a dose-dependent (10(-7) M, 10(-6) M) decrease in the maximal response (non-competitive antagonism), while the ganglion blocker pentamethonium (10(-4) M) was without effect. NA caused membrane depolarization accompanied by a decrease in the input resistance after local application (from 77 micrograms to 1.6 mg). This effect persisted in the presence of 10(-5) M-phentolamine but was abolished by 10(-5) M-propranolol. IP perfusion (10(-4) and 10(-3) M) or local application (0.3 M; from 32 to 130 micrograms) caused the same electrical changes as those induced by NA and DA. The effect of IP persisted in the presence of 10(-5) M-phentolamine, 10(-4) M-pentamethonium and 10(-4) M-domperidone, but was abolished by propranolol (10(-5) M) and tetrodotoxin (5 X 10(-6) M) and markedly diminished by atropine (10(-5) M).(ABSTRACT TRUNCATED AT 400 WORDS)

Contribution of myocardial diffuse double-layer calcium to contractile function

The role of diffuse double-layer calcium in cardiac excitation-contraction coupling was examined using rabbit interventricular septa, cultured neonatal rat myocardial cells, and gas-dissected sarcolemmal membranes. The diffuse double layer refers to the space directly adjacent to the sarcolemma where the ionic composition of the media is a direct function of the membrane surface potential. The divalent cation dimethonium was used as a specific probe for the diffuse double layer. According to Gouy-Chapman theory, replacement of sodium with sucrose should increase the amount of calcium located in this compartment. Dimethonium (10 mM) was found to decrease calcium uptake and contractility during low-sodium (33 mM) perfusion when the perfusate contained sucrose but not LiCl. Dimethonium did not decrease calcium uptake or contractility during control perfusion. The results suggest that calcium present in the myocardial diffuse double layer can be augmented or reduced in accordance with Gouy-Chapman theory. Changes in diffuse double-layer calcium are accompanied by small (7.8%) but significant changes in contractility.

The channel-blocking action of methonium compounds on rat submandibular ganglion cells

The effects of drugs of the polymethylene bis-trimethylammonium (methonium) series on the characteristics of the synaptic currents (e.s.cs) recorded from voltage-clamped rat submandibular ganglion cells have been studied. The drugs studied were from C4 to C10 (decamethonium). All of the drugs except C4 shortened the initial decay phase of the e.s.c.; C9 and C10 produced an additional slowly decaying component. These effects were interpreted in terms of an open channel block mechanism, the calculated rate constants for association with the open channel at -80 mV being fairly similar (5.9 X 10(6) to 18.1 X 10(6)M-1S-1) for all of the compounds except C4, which had no effect on the e.s.c. decay. All of the compounds produced use-dependent block when tested with short trains of stimuli at 10 Hz, or with trains of ionophoretic pulses of acetylcholine, consistent with their channel blocking property. Tubocurarine had a similar effect, but not trimetaphan or mecamylamine. Recovery from use-dependent block with short chain methonium compounds, up to C8, was very slow in the absence of agonist, being incomplete even after several minutes. With C9 or C10 or tubocurarine, recovery from use-dependent block was complete within a few seconds. With C6 recovery in the absence of agonist was unaffected by membrane potential, but could be accelerated by applying acetylcholine with the cell depolarized to -40 mV. This persistent block was ascribed to the ability of the blocking molecule to become trapped by closure of the channel. With C9 and C10 it is assumed that their presence inhibits channel closure, so they can escape without the help of agonist. When use-dependent block is avoided by leaving the ganglion unstimulated during equilibration with the blocking drug, the first e.s.c. elicited shows no appreciable reduction of amplitude, though with C6, C7 or C8 subsequent responses elicited at 0.1 Hz become progressively more blocked. Even at 1 mM, C6 does not prevent acetylcholine from opening ionic channels. It is concluded that all of the effects on e.s.c. amplitude can be interpreted in terms of channel block, there being no evidence of any receptor blocking action.

[Ganglionic-blockading action of bis-ammonium compounds]

The actions of bis-ammonium compounds on acetylcholine-activated channels were studied in voltage-clamped neurons of isolated superior cervical ganglion in a rabbit. The kinetics of the compound binding to open channels was estimated from shortening of the decay of fast excitatory postsynaptic current (which is determined by the rate of channels closure). The kinetics of dissociation of the compound from open channels was estimated from the kinetics of the restoration of the second response to double-pulse application of acetylcholine in presence of the blocking compound. The rate constant of bindings of the bis-ammonium compounds to open channels increased while the rate constant of dissociation decreased with membrane hyperpolarization. This voltage-dependence increased with the lengthening of the polymethylene chain in the compound and remained unchanged with the lengthening of nitrogen group radicals. The ganglion-blocking activities of the compounds as determined in the cat ganglion in situ correlated with their rate constants of binding to open channels. It was concluded that ganglion-blocking actions of bis-ammonium compounds is determined by their channel-blocking activities.

Structural requirements of compounds to inhibit pulmonary diamine accumulation

The diamine, putrescine, is accumulated into slices of rat lung by a temperature and energy dependent process similar to that responsible for the uptake of cadaverine, the polyamines spermidine and spermine, and the herbicide paraquat. Structure-activity studies using monoamines and diaminoalkanes, amino acids and guanidino compounds, have shown that in order to inhibit the pulmonary accumulation of putrescine, chemicals should possess at least one but preferably two nitrogen-containing cationic groups. In the series of alpha, w-diaminoalkanes studied, the inhibitory potential increased with increasing chain length, reaching a plateau at 1,7-diaminoheptane. These observations together with the fact that putrescine is a good substrate for the uptake system (Km 15 microM, Vmax 704 nmoles/g wet wt/hr) suggest that effective inhibitors require at least four methylene groups between their cationic centres and that diamines with more methylene groups may fold to give this separation. With both the monoamines and the alpha, w-diaminoalkanes, changes in the free energies of interaction suggest that the observed increases in inhibitory potential with increasing chain length are due to increased hydrophobic bonding, which is a consequence of the addition of methylene groups to the alkyl chain. Furthermore, the ability of compounds to inhibit putrescine uptake appears to be related to their propensity to bind with the appropriate site for putrescine. Steric hindrance of this ionic interaction by the quaternisation of the cationic centres of the inhibitors with methyl groups, results in a total loss of measurable inhibitory activity. Also, the introduction of anionic carboxyl groups into inhibitors result in a loss of inhibitory potential, probably due to ionic repulsion. The antileukaemic drug, methylglyoxal-bis-guanylhydrazone (MeGAG), and its congeners, were some of the most potent inhibitors of putrescine uptake studied. Our findings suggest similarities between the uptake system for putrescine into the lung with other uptake systems described for MeGAG and certain polyamines.

Dimethonium, a divalent cation that exerts only a screening effect on the electrostatic potential adjacent to negatively charged phospholipid bilayer membranes

Calcium and other alkaline earth cations change the electrostatic potential adjacent to negatively charged bilayer membranes both by accumulating in the aqueous diffuse double layer adjacent to the membrane and by adsorbing to the phospholipids. The effects of these cations on the electrostatic potential are described adequately by the Gouy-Chapman-Stern theory. We report the results of experiments with ethane-bis-trimethylammonium, a cation that has been termed "dimethonium" or "ethamethonium" in analogy with hexamethonium (hexane-1,6-bis-trimethylammonium) and decamethonium (decane-1,10-bis-trimethylammonium). We examined the effect of dimethonium on the zeta potential of multilamellar vesicles formed from the negative lipid phosphatidylserine (PS) and from 5:1 phosphatidylcholine/phosphatidylserine mixtures in solutions containing 0.1, 0.01 and 0.001 M sodium, cesium, or tetramethylammonium chloride. We also examined the effect of dimethonium on the conductance of planar PS bilayer membranes and the 31P NMR signal from sonicated PS vesicles formed in 0.1 M NaCl. We found no evidence that dimethonium adsorbs specifically to bilayer membranes. All the results, except for those obtained with vesicles of low charge density formed in a solution with a high salt concentration, are consistent with the predictions of the Gouy-Chapman theory. We conclude that dimethonium, which does not have the pharmacological effects of hexamethonium and decamethonium, is a useful divalent cation for physiologists interested in investigating electrostatic potentials adjacent to biological membranes.

Voltage-dependent actions of short-chain polymethylene bis-trimethylammonium compounds on sympathetic ganglion neurons

Effects of polymethylene bis-trimethylammonium compounds (with 4-7 carbons in the polymethylene chain, C4-C7) on voltage-dependence of fast excitatory postsynaptic current (EPSC) were studied in voltage-clamped neurons of the isolated rabbit superior cervical ganglion. All these compounds shortened the EPSC decay (which remained single-exponential) and decreased (or reversed) the dependence of the EPSC decay on membrane hyperpolarization. All drugs slightly decreased the EPSC amplitude; in addition, C6 and C7 decreased their dependence on membrane hyperpolarization. It is suggested that shortening of the EPSC decay produced by ganglion-blocking agents results from their binding to the open ionic channel (channel-blocking effect). The ratio of channel-blocking activities of these drugs correlates with the well-known ratio of their ganglion-blocking activities. It is suggested that the channel-blocking activities of polymethylene bis-trimethylammonium compounds determine their ganglion-blocking activities. The model of channel-blocking action is discussed.

[Age-related aspects of the reaction of isolated strips of rat rectum and colon to carbacholine, atropine and pentamine]

Experiments in vitro were made to record isotonic contractions of isolated strips of the rectum and colon of rats distributed into 4 age groups. It was shown that in one-week-old rats, the rectal and colonic strips reacted to carbacholine (1 x 10(-10--1 x 10(-5) M) to a far less extent than those in adult rats. In the course of postnatal development the reaction of the colonic strips to carbacholine reached the adult rat level more rapidly. Pretreatment of the colonic strips from one- and two-week-old rats with pentamine solutions (2 x 10(-5)--1 x 10(-4) M) led to the increased carbacholine response rather than to its lowering which was the case in the adult animals. Pretreatment of the strips in question with atropine solutions (1 x 10(-14)--1 x 10(-6) M) decreased the response to the cholinomimetic to a more significant extent than in the adult animals. High concentrations of the cholinomimetic did induce a considerable percentage of contractions.

Shape and volume changes in rat erythrocytes induced by surface-active alkyltrimethylammonium salts and sodium dodecyl sulphate

Surface-active alkyltrimethylammonium salts (C12, C14 and C16) and sodium dodecyl sulphate (SDS) caused shape alterations and a volume increase in rat erythrocytes. The alkyltrimethylammonium salts caused echinocytic shapes at both prelytic and lytic concentrations during the first minutes of incubation at 37 degrees C but as the incubation proceeded some of the echinocytes were transformed into stomatocytes. This transformation developed through the normal discocyte shape and it occurred only above certain concentrations. With C14 and C16 the concentration at which stomatocytic shapes appeared coincided with those at which the volume increase began. With the C12 homologue stomatocytic shapes did not appear until lytic concentrations were reached, whereas the volume increase began at prelytic concentrations. SDS caused only echinocytic shapes at 37 degrees C and these appeared at prelytic concentrations, whereas the volume increase was associated with lytic concentrations. When erythrocytes crenated by SDS were cooled to room temperature they were transformed into stomatocytes and discocytes. Our results indicate that (a) even though ionic surfactants induce both swelling and shape alterations in erythrocytes these two changes are not necessarily connected, and that (b) the different shapes induced by cationic and anionic surfactants cannot be due to differences in the distribution of the surfactant molecules within the lipid bilayer of the erythrocyte membrane alone.

Effects of surface-active alkyltrimethylammonium salts on concanavalin A-mediated agglutination in Acanthamoeba castellanii

Pretreatment of Acanthamoeba castellanii (Neff strain) with sublytic concentrations of surface-active alkyltrimethylammonium salts (C12, C14, C16) enhanced ConA-mediated agglutination of the amoebae. Treatment with the surfactants alone did not affect the "spontaneous" agglutination of the amoebae. Electron microscopic (SEM and TEM) examinations of amoebae treated with sublytic concentrations of the surfactants did not reveal any significant alterations in cell shape or in cell surface morphology in treated cells. The binding of [3H]ConA to the amoebae was not affected by pretreatment with sublytic concentrations of the surfactants. It is suggested that the increase in ConA-mediated agglutination in surfactant-treated amoebae may be due to a fluidizing effect of the surfactants on plasma membrane of the amoebae. Part of the results of this work has previously been published in Eur. J. Cell Biol. 22, 210 (1980). (Abstract M 624).

Voltage fluctuations at the frog sartorius motor endplate produced by a covalently attached activator

The depolarization that develops after covalent attachment of trimethylammonium benzoyl to the dithiothreitol-reduced frog sartorius acetylcholine receptor is accompanied by a small increase in voltage fluctuations. The amplitude of the elementary voltage event produced by the covalently attached activator is about 0.04 microV, almost an order of magnitude below the acetylcholine shot-effect amplitude in the control preparation, and about one-fourth the acetylcholine shot amplitude after disulfide-bond reduction. Spectral density plots of trimethylammonium-benzoyl noise can be analyzed in terms of two relaxation rates that bracket the single rate observed in response to acetylcholine.

Activation of the frog sartorius acetylcholine receptor by a covalently attached group

The frog sartorius motor endplate was treated with the specific disulfide bond reducing agent dithiothreitol and subsequently exposed to a covalently reacting compound (the nitrophenyl ester of p-carboxyphenyltrimethylammonium iodide, NPTMB) known to activate the dithiothreitol-reduced acetylcholine receptor in Electrophorus electroplax. NPTMB causes a maximum depolarization of about 35 mV when applied to the dithiothreitol-treated sartorious motor endplate. It is ineffective on postjunctional membrane prior to disulfide bond reduction and on extrajunctional regions, reduced or unreduced. High concentrations of a competitive antagonist such as (+)-tubocurarine prevent reaction between NPTMB and the reduced receptor and cause a repolarization of the membrane when applied to the already-depolarized preparation. We conclude that in frog muscle, as in electroplax, the attached activator bridges the acetylcholine binding site of the reduced receptor between a sulfhydryl group, to which it is covalently bound, and a negative subsite, with which it forms a reversible ionic band.

Transmembrane electrical potential and transmembrane pH gradient in the acidophile Thiobacillus ferro-oxidans

Thiobacillus ferro-oxidans is capable of using the oxidation of Fe2+ by O2 at pH 2.0 as the sole source of energy for growth and CO2 fixation. The bacterium maintains an intracellular pH of 6.5 over a range of external pH from 1.0 to 8.0, as measured by [14C]acetate and [3H]methylamine distribution. The membrane potential was estimated by the distribution of the lipid-soluble cation dibenzyldimethylammonium and the anion SCN-. At pH 2.0 (the pH of growth) during Fe2+ oxidation the transmembrane pH gradient is 4.5 units with an opposing membrane potential of -10mV, giving a proton electrochemical gradient of +256mV. This gradient is actively maintained.

Effects of catecholamines and their inhibitors on the isolated canine pancreas. II. Dopamine

Dopaminergic agonists (dopamine, 2, 10, 50, and 250 mug; apomorphine, 1 mg; noradrenaline, 2, 20, and 200 mug), and inhibitors (haloperidol, 5 mg; pentamethonium, 500 mg; phenoxybenzamine, 15 mg, and atropine sulfate, 10 mg), were tested on isolated perfused canine pancreas; under basal conditions and under stimulation by a background of secretin (0.1, 0.5, and 10.0 clinical unit per hr), or of caerulein (1200 ng per hr). Low doses of dopamine induced a vasodilation inhibited by haloperidol Large doses induced a vasoconstriction, presumably by stimulation of alpha adrenergic receptors. Dopamine stimulated hydrelatic secretion. The calculated maximal response was about one-half that of secretin. This response was inhibited by haloperidol but not by atropine, pentamethonium, and phenoxybenzamine. No acinar degranulation was observed after stimulation by dopamine. The response to secretin was not altered by haloperidol. It was concluded that blood vessels and pancreatic tissue contain specific receptors to dopamine different from secretin receptors. Secretory response to noradrenaline after phenoxy benzamine was inhibited by haloperidol, suggesting that this effect was mediated by the stimulation of dopamine receptors of the cells. A hypothetical representation of the interrelation between dopamine, secretin, and noradrenaline is discussed.

[Trans-membrane difference of the vascular wall potentials and electrolyte content under the effect of nicotine and pentamine]

In experiments with anesthetized cats the effect of nicotine and pentamine with their intravenous administration into the organism on the transmembraneous difference on the carotid artery potentials and electrolytes exchange in the vascular wall was analyzed. Nicotine (60 and 120 gamma/kg) was found to increase the difference of potentials in the vascular wall of the carotid artery and pentamine (1 and 10 mg/kg)--to reduce it. Nicotine raised the level of potassium and downgraded the sodium concentration in the vascular wall, while changes in the proportion of calcium and magnesium ions proved to be insignificant and were demonstrable only in individual vessels. Pentamine increased the potassium and sodium content in the wall of blood vessels, excercising but little effect on the level of calcium and magnesium ions. A relation between changes in the transmembraneous difference of potentials and variations of the ionic composition in the vascular wall, mostly of potassium and sodium ions, is suggested.

[Role of the autonomic nervous system in the differentiated response of pancreatic enzyme secretion]

In chronic studies on fistular dogs, the basal secretion of pancreas and secretion stimulated by the duodenal perfusion of acid (pH 1.5) solutions of albumen and its poly-peptide hydrolysate was studied. Perfusion of the hydrolysate stimulated the pancreatic release of enzyme more than albumen itself. Pentamin, atropin, and ergotal suppressed basal secretion and secretion stimulated by the duodenal perfusion with the above solutions.

[Functional state of the liver in patients with malignant neoplasms, operated on with the use of ganglionic blockaders and moderate hypotension]

The functional state of the liver studied in 411 patients with malignant neoplasms undergoes the least variations under conditions of surgery with ganglionary blockade and moderate hypotension (not less than 90 mm Hg). These patients showed the best indices of protein metabolism and the status of the blood coagulation system, as well as activation of spontaneous anticoagulation. Complications in these patients were observed, but rather more rarely than in patients operated upon without using ganglionary blockade.

Interaction of competitive antagonists: the anti-curare action of hexamethonium and other antagonists at the skeletal neuromuscular junction

1. In the rat isolated diaphragm preparation hexamethonium and other low potency competitive antagonists of acetylcholine (ACh), including gallamine and hyoscine butylbromide, reverse block by the potent antagonists tubocurarine, pancuronium and alcuronium. 2. In the presence of tubocurarine, hexamethonium increases the amplitude of the end-plate potential without increasing the quantal content. It enhances the response to ACh applied iontophoretically to the end-plate but does not enhance the response to ACh applied in the bath. 3. The anti-curare effect of hexamethonium is abolished in the diaphragm of the rat, guinea-pig and mouse by inhibitors of acetylcholinesterase. The effect is not observed in the indirectly stimulated toad sartorius muscle. 4. The effect is explained if tubocurarine does not dissociate appreciably in the time taken for ACh to achieve high occupancy of receptors, so that a fraction of receptors is completely excluded from occupation by ACh. Equilibration with hexamethonium reduces the fraction excluded by tubocurarine and the transmitter now competes with hexamethonium for more receptors and produces a larger response. 5. On the basis of this explanation the half-time for dissociation of tubocurarine must be about 1 millisecond. It follows that tubocurarine does not act competitively with ACh at synapses when transmitter action is sufficiently brief, and that its binding to the receptor is probably diffusion-limited.