Interactions at human ether-à-go-go-related gene channels.

Several noncardiovascular drugs have the potential to induce Torsades de Pointes cardiac arrhythmias via blockade of the rapid component of the cardiac delayed rectifier K(+) current (I(Kr)), which is encoded by human ether-à-go-go-related gene (hERG). The aim of the present study was to characterize possible interactions between terfenadine, binding to a site located inside the central cavity, and the following substances with various binding sites: dofetilide, fluvoxamine, chlorobutanol, and a hERG-specific toxin isolated from scorpion venom (CnErg1). The whole-cell configuration of the patch-clamp technique was employed on hERG channels stably expressed in human embryonic kidney 293 cells. Terfenadine does not interact with dofetilide or fluvoxamine at hERG channels. Slight subadditive inhibitory effects on hERG peak tail currents were observed when terfenadine and CnErg1 were administered in combination. Terfenadine and chlorobutanol synergistically inhibit hERG peak tail currents and enhance each other's inhibitory effect in a concentration-dependent way. In conclusion, terfenadine interacts with CnErg1 and chlorobutanol, but not with dofetilide or fluvoxamine, at hERG channels. It is shown that interactions between chlorobutanol and a hERG channel blocker binding inside the central cavity (terfenadine) produce synergistic effects on hERG currents.

Effects of chlorobutanol on primary and secondary endings of isolated cat muscle spindles.

The effects of the preservative chlorobutanol on primary and secondary endings of muscle spindles isolated from the tenuissimus muscle of the cat were investigated in this study. Chlorobutanol was applied to the bathing solution in final concentrations of between 10 and 100 microg/ml. It induced a reversible and dose dependent decrease in the discharge frequency of both types of ending without any visible length change in the sensory region of the receptor. The initial activity, the peak dynamic discharge, the maximum static discharge value and the final static discharge value were evaluated from an ending's discharge pattern obtained during ramp-and-hold stretches. These four basic discharge frequencies decreased in parallel with increasing concentrations of chlorobutanol. Their sensitivities to chlorobutanol were similar (mean values: -0.11 to -0.29 imp/s per microg/ml chlorobutanol) and were independent of the amplitude of stretch. The dynamic response and the static response of both primary and secondary endings remained unchanged, indicating that the sensitivity of the spindle to stretch was not influenced by chlorobutanol. Chlorobutanol also reduced the discharge activity of the muscle spindle afferents during sinusoidal stretches. The amplitude of the receptor potential (AC component) remained unchanged under chlorobutanol. With the available recording technique it was not possible to measure slow shifts of the membrane potential. However, a hyperpolarization of the ending's membrane might explain why the afferent discharge frequency is reduced by chlorobutanol. The calcium dynamics of the spindle do not appear to be altered by CB, as the effect exerted on the afferent discharge by a change in the extracellular calcium concentration and a blockage of calcium channels was different from the CB effect. As the inhibitory effect of CB was reduced by ouabain, it is possible that CB activates the electrogenic Na/K pump or affects a mechanism that is closely related to the activity of the pump. The properties of the axonal membrane appear not to be altered, as chlorobutanol did not change the shape of action potentials.

The survival of herpes simplex virus in multidose office ophthalmic solutions.

PURPOSE: To determine the survival of herpes simplex virus type 1 (HSV-1) in several multidose ophthalmic solutions. METHODS: In three separate trials, 10 aliquots of 5 ml each of three common multidose topical ophthalmic solutions, sodium fluorescein, proparacaine, and nonpreserved artificial tears, were inoculated with 10(5), 10(4), and 10(3) pfu per ml of HSV-1. All samples were titered on A549 cells at various time points for surviving HSV-1. RESULTS: Herpes simplex virus type 1 was not recovered from the fluorescein and proparacaine solutions at 1 hour or any time thereafter, regardless of inoculation titer. Herpes simplex virus type 1 was recovered from the artificial tears up to 7 days. CONCLUSION: Unlike adenovirus, HSV-1 does not survive in preserved fluorescein and proparacaine multidose solutions; therefore, office transmission is highly unlikely.

The effect of oxytocin on the contractile force of human atrial trabeculae.

UNLABELLED: We performed an in vitro examination of the inotropic effect of oxytocin, chlorobutanol, and their combination to assess the effect of these drugs on the contractile force of human atrial trabeculae. Right atrial tissue samples were obtained during cardiac surgery with cardiopulmonary bypass. Trabeculae of the atrial appendage were dissected and mounted on muscle stands in a modified Krebs-Henseleit buffer bath. This isometric atrial trabecula preparation was subjected to a cumulative pharmacological protocol of either pure oxytocin, pure chlorobutanol, or a combination of the two drugs until no further change occurred in either developed force or resting force of the atrial trabeculae. A "no drug" buffer solution was used to assess the effect of time on the natural decay of the atrial preparation. The relative developed force of oxytocin plus chlorobutanol solution and pure chlorobutanol were similar in magnitude and lower than that in control experiments (P < 0.001) Pure oxytocin did not change the contractile force of atrial tissue. We conclude that pure oxytocin does not have a cardiodepressive effect in this human atrial preparation. Chlorobutanol has a negative inotropic effect, which is of a magnitude similar to a combined solution of chlorobutanol and oxytocin. Therefore, chlorobutanol added as a preservative to the commercial synthetic oxytocin solution may contribute to hypotension observed in patients after an intravenous bolus injection. IMPLICATIONS: We obtained specimens of heart tissue from patients undergoing cardiac surgery and conducted a laboratory study of the effects of oxytocin and its preservative (chlorobutanol) on these tissue samples. Chlorobutanol decreased the ability of the heart to contract, while as pure oxytocin had no effect. This explains why maternal blood pressure may decrease and provides impetus to produce oxytocin with another, safer preservative.

Chlorobutanol, a preservative of desmopressin, inhibits human platelet aggregation and release in vitro.

Therapeutic preparations of desmopressin for parenteral use contain the preservative chlorobutanol (5 mg/ml). We show here that chlorobutanol is a potent inhibitor of platelet aggregation and release. It exhibited a significant inhibitory activity toward several aggregation inducers in a concentration- and time-dependent manner. Thromboxane B2 formation, ATP release, and elevation of cytosolic free calcium caused by collagen, ADP, epinephrine, arachidonic acid and thrombin respectively were markedly inhibited by chlorobutanol. Chlorobutanol had no effect on elastase-treated platelets and its antiplatelet effect could be reversed. It is concluded that the antiplatelet effect of chlorobutanol is mainly due to its inhibition on the arachidonic acid pathway but it is unlikely to have a nonspecific toxic effect. This antiplatelet effect of chlorobutanol suggests that desmopressin, when administered for improving hemostasis, should not contain chlorobutanol as a preservative.

The mechanism of ceruminolysis.

In a previous study comparing the efficacy of a selection of commonly used ceruminolytics, the authors noted that aqueous-based preparations, and in particular solutions of sodium bicarbonate, were more effective in disintegrating cerumen than most organic-based preparations. In that study, the authors also observed that not only had the wax truly disintegrated following exposure to the aqueous-based preparations, but also that a marked degree of swelling of the wax spheres had occurred with these preparations. In this paper the mechanism of ceruminolysis was investigated by means of a number of commonly available histological techniques. Our findings show that desquamated sheets of corneocytes are the major constituent of cerumen plugs and provide the structural framework of the wax bolus. Ceruminolytics work by hydrating the keratin cells of these sheets of desquamated stratum corneum and subsequently inducing keratolysis, with disintegration of the wax.

A new radio-opaque injection technique for tissue preservation.

This study has investigated the action of two commonly available preservatives, chlorbutol and chlorocresol, on fresh cadaver tissue. If the arterial system of the subject is perfused first with either preservative then the progression of tissue necrosis can be delayed for up to 1 month. The preservative can be combined with the lead oxide-gelatin mixture described by Rees and Taylor without compromising the results of radiographic studies. Both chlorocresol and chlorbutol have the advantage over formalin of retaining the normal colour and texture of the tissues. A regimen is suggested which has all of the advantages of the mixture originally described by Salmon, but is much simpler and cheaper to produce. It has proved successful when used in whole cadavers but the visceral contents must be removed at an early stage.

The effect of oxytocin on porcine malignant hyperpyrexia susceptible skeletal muscle.

1. Certain commercial preparations of oxytocin have been reported to reverse the development of pale soft exudative meat and malignant hyperpyrexia (MH) in pigs in vitro. 2. In this study it is shown that preservative-free oxytocin has no significant effect on the characteristic contractures of MH susceptible (MHS) muscle to halothane, caffeine, succinylcholine and KCl in vitro. 3. Whilst a commercial preparation of oxytocin, Syntocinon (containing chlorbutol as preservative), reversed and prevented the MHS characteristic responses, this study demonstrates conclusively that this was entirely due to the preservative chlorbutol.

The effects of chlorbutol on skeletal muscle sarcoplasmic reticulum function in porcine malignant hyperpyrexia.

1. Chlorbutol, a muscle relaxant, inhibits the in vitro muscle hypercontractility which is characteristic of the anaesthetic complication, malignant hyperpyrexia (MH). 2. Studies on isolated sarcoplasmic reticulum vesicles have shown that this effect of chlorbutol in MH is not due to a modification of Ca2+-transport mechanisms.

Hormonal responsiveness of liver cells during the liver regeneration process induced by carbon tetrachloride administration.

In control rats most of the ureagenic effect of adrenaline is mediated through alpha1-adrenoceptors with little participation of beta-adrenoceptors. Administration of carbon tetrachloride to rats induces significant changes in the adrenergic responsiveness of their hepatocytes. In rats intoxicated 3-5 days before the experiments were performed there is a marked increase in the beta-adrenergic and a decrease in the alpha-adrenergic responsiveness of the hepatocytes. The alpha1-adrenergic responsiveness increased with time reaching its basal level 15 days after the administration of carbon tetrachloride; simultaneously, the betal-adrenergic responsiveness was decreased. No change in the responsiveness to vasopressin and angiotensin II was observed in intoxicated animals as compared to the controls. In contrast, the responsiveness to glucagon was increased. Increased ability of local anesthetics to decrease urea production was observed in cells from intoxicated animals. It is suggested that changes at the plasma membrane level (lipids, receptors and transducing proteins) might participate in producing these effects.

Effects of glucagon, Arg-vasopressin, and angiotensin II on rat hepatic zinc thionein levels.

Rat hepatic zinc thionein levels can be modulated by a variety of external and internal stimuli. Metals, such as zinc or copper, induce levels 20 to 50 fold over controls. Catecholamines can increase levels 10 to 20 fold, while glucocorticoids, such as dexamethasone, can increase levels modestly by 2-6 fold. We have investigated the ability of additional hormones, which have receptors on hepatocytes, to modulate the levels of hepatic zinc thionein. Glucagon, angiotensin II, and Arg-vasopressin were administered intravenously and intraperitoneally, one time and three times, over an 11 hour period. Zinc thionein levels in rat liver were increased 1.7 to 5.6 fold by glucagon and 1.7 to 3.6 fold by angiotensin II, but not at all by Arg-vasopressin, as compared to appropriate controls. Glucagon and angiotensin II, when administered in vivo, can modulate zinc thionein levels in rat liver to an extent similar to glucocorticoids. Hepatic zinc thionein levels must now be recognized to be affected in vivo by metals, glucocorticoids, catecholamines, and polypeptide hormones.

Two latent period processes in Limulus ventral photoreceptors.

The latent period of Limulus ventral photoreceptor potentials consists of two contiguous time segments, S1 and S2, which exhibit the following properties: (1) the duration of S1 is inversely dependent on the incident energy provided by the first stimulating light flash; (2) the duration of S1 is prolonged in the presence of GTP-gamma-S [guanosine-5'-0- (3-thiotriphosphate)] or papaverine; (3) the duration of S1 is abbreviated in the presence of sodium vanadate or chlorobutanol; (4) the duration of S2 is abbreviated by light adaptation; and (5) the duration of S2 is prolonged more than S1 in a low temperature environment. The existence of these two components of the Limulus ventral photoreceptor potential latent period is demonstrable both in dark adapted photoreceptors, using single constant intensity light pulses of varying duration, or in partially light adapted photoreceptors, using a stimulating conditioning pulse-test pulse sequence. On the basis of these results it is tentatively concluded that the two segments of the latent period of Limulus ventral photoreceptor potentials are occupied by different processes. The first process, occupying the S1 segment, generates a critical concentration of a photoproduct which, directly or indirectly, eventually alters the conductance of the active photoreceptor membrane. The second process, occupying the S2 segment, is concerned with the initiation of the SPFs which sum to produce the receptor potential. It is possible that the hydrolysis of GTP actively participates in the first process.

Correlation between the sensitivity of the ciliary beat frequency of human adenoid tissue and chicken embryo tracheas for some drugs.

The effects of benzalkonium chloride, chlorbutol,xylometazoline and naphazoline on the ciliary beat frequency of human adenoids and chicken embryo tracheas have been determined and compared. Chlorbutol 0.5% appeared to arrest ciliary motion in both tissues within 5 minutes. Rinsing with Locke Ringer solution (LR) restored the ciliary motion almost completely in both cases. Benzalkonium chloride 0.006% +EDTA 0.1% decreased the ciliary beat frequency 35% for the human tissues and 50% for the chicken tissues after a contact of 20 minutes. In both cases the frequency hardly changed after rinsing with LR. Naphazoline nitrate 0.1% and xylometazoline HCl 0.05% have reversible effects on the ciliary beat frequency of both human adenoids and chicken embryo tracheas. Cilia of human adenoids appeared to be more sensitive for xylometazoline than for naphazoline; whereas cilia of chicken embryo tracheas were more affected by naphazoline than by xylometazoline. The results with human adenoids and chicken embryo tracheas show a correlation (correlation coeff. = 0.82, p less than 0.005). In the initial response the differences in sensitivity to preservatives and drugs were in many cases statistically significant, but the final effects were similar.

Metabolism by rat hepatic microsomes of fluorinated ether anesthetics following isoniazid administration.

The possibility that enflurane defluorination is increased following treatment with isoniazid was investigated in male Fischer 344 rats. The effects of various isoniazid dosage regimens on the hepatic microsomal defluorination rates of enflurane were compared with those of several other ether anesthetics, and the conditions for production of maximal enflurane defluorination rates were determined. Seven to ten days of treatment with 50 mg/kg/day isoniazid (Nydrazid) resulted in maximal rates of defluorination of methoxyflurane, enflurane, isoflurane, and sevoflurane with no overt sign of toxicity. Compared with saline treatment of control rats, isoniazid increased defluorination of enflurane 370 per cent, methoxyflurane 259 per cent, sevoflurane 283 per cent, and isoflurane 168 per cent. Previous studies have shown that while the enzyme inducer phenobarbital increased in vitro rates of methoxyflurane defluorination approximately 1000 per cent, the rate of enflurane defluorination remained unchanged or increased by 100 per cent at most. In this study, enhanced hepatic microsomal defluorination was not associated with an increase in cytochrome P-450 per mg protein. Anesthetic defluorination rates were not altered by treatment with chlorobutanol, the preservative contained in Nydrazid.

Interaction of light and chlorobutanol on Limulus ventral photoreceptor potential latency.

Exposure of Limulus ventral photoreceptors to light or to chlorobutanol produces a shortening of the latent period of the receptor potential. The latency shortening effect of chlorobutanol (0.5 mM) is maximal in dark adapted photoreceptors and decreases progressively as the level of light adaptation increases. At the highest usable levels of light adaptation, the latencies of receptor potentials from cells exposed only to sea water containing chlorobutanol were virtually identical. This confluence of the latent periods suggests that light and chlorobutanol may affect the same component of the latent period.

Fluress, fluorescein and benoxinate: recovery from bacterial contamination.

The ability to recover from bacterial contaminations with Staphylococcus auresus and Pseudomonas aeruginosa was determined for three optometric DPAs: Fluress, fluorescein and benoxinate. Results show that Fluress recovers from contamination more rapidly than benoxinate or fluorescein. This ability to recover from contamination and the relative ease of use of Fluress may make it the DPA choice for a number of optometric procedures including applanation tonometry.

Effect of chlorobutanol on Limulus ventral photoreceptor latency: a model of a two component latent period.

Chlorobutanol (1,1,1-trichlor-2-methyl-2-propanol) decreases the duration of the latent period of Limulus ventral eye receptor potentials. This effect is both concentration and intensity dependent. Between 0.05 and 1 mM chlorobutanol in sea water the extent of latency shortening effect of chlorobutanol linear function of the logarithm of the chlorobutanol concentration. The latency shortening effect of chlorobutanol diminishes with decreasing intensity of stimulation and virtually disappears at intensities just exceeding threshold. These results are explained by postulating that the latent period is composed of two processes only one of which is sensitive to chlorobutanol and, further, that the duration of the chlorobutanol-sensitive process is not appreciably affected by the stimulating intensity. This model of a two component latent period may be tested experimentally. In several experiments prolonged exposure of ventral photoreceptor cells to chlorobutanol coupled with a short exposure to calcium deficient sea water produced a collapse of the receptor potential followed by a slow recovery after returning to perfusion with normal sea water. During the recovery a slow, low amplitude positive wave exists which has been tentatively called a prepotential.

Partial voltage clamping of Limulus ventral photoreceptor potentials: evidence of programmed conductance changes.

Light-initiated currents elicited by brief light stimuli from Limulus ventral photoreceptors bathed in normal sea water generally exhibit a smooth contour, although the unclamped receptor potential elicited by an identical light stimulus usually exhibits distinct C1 and C2 components. However, light-initiated currents obtained from cells exposed to chlorobutanol often exhibit two components. Data from such experiments indicate that peak C2 current is more strongly voltage dependent than peak C1 current, as in Limulus lateral eye retinular cells. The results of partial voltage clamp experiments with ventral photoreceptors in which the clamping episode terminated at different times during the receptor potential reveal relatively minor perturbations of the rebound receptor potential when compared with the unclamped control response. These findings suggest that the temporal pattern of the membrane conductance changes which underlie the receptor potential is determined prior to the occurrence of the receptor potential. It is likely that the program for these conductance changes is developed during the latent period of the receptor potential.

Electrophysiologic and morphologic effects of ophthalmic preparations on rabbit cornea epithelium.

The effects of several components of ophthalmic preparations on isolated rabbit cornea were studied by continuous electrophysiologic monitoring followed by fixation for scanning electron microscopy (SEM). Benzalkonium chloride (0.001 percent), thimerosal (0.0004 percent), and amphotericin B (0.0025 percent) all briefly increased ion transport, then greatly decreased epithelial resistance. Severe disruption of surface cell layers occurred simultaneously with resistance decrease. Silver nitrate (0.00017 percent) stimulated transport with less accompanying morphologic damage. Tetracaine (0.05 percent) disrupted epithelial function and caused exfoliation of several cell layers. Chlorobutanol (0.1 percent) produced a nearly complete loss of the squamous cell layer. Chloramphenicol, epinephrine, and pilocarpine produced minor changes in structure and electrophysiology at full clinical concentration. It was concluded that low concentrations of preservatives in ophthalmic preparations disrupt the barrier and transport properties of the corneal epithelium.