Sodium current expression during postnatal development of rat outer hair cells

Outer hair cells of the cultured organ of Corti from newborn rats (0-11 days after birth) were studied in the whole-cell patch-clamp configuration. A voltage-activated sodium current was detected in 97% (n = 109) of the cells at 0-9 days after birth. The properties of this current were: (1) its activation and inactivation kinetics were fast and voltage-dependent, (2) the voltage at half-maximum activation was -45.0 mV, (3) its steady-state inactivation was temperature-sensitive (the half-inactivating voltage was -92.6 mV at 23 degrees C and -84.8 mV at 37 degrees C), (4) the reversal potential (80 mV) was close to the sodium equilibrium potential and currents could be abolished by the removal of extracellular sodium, and (5) tetrodotoxin blocked the current with a Kd of 474 nmol/l. Current amplitudes were up to 1.7 nA at room temperature. Mean current amplitudes showed a developmental time course with a maximum at postnatal days 3 and 7 for outer hair cells from the basal and apical part of the cochlea, respectively. In current-clamp mode cells had membrane potentials of -59.7 +/- 11.7 mV (n = 9). When cells were hyperpolarized by constant current injection, depolarizing currents were able to trigger action potentials. At 18 days after birth, sodium currents were greatly reduced and barely detectable. The results show that, unlike adult outer hair cells, immature outer hair cells regularly express voltage-gated sodium channels. However, due to mismatching of the sodium current inactivation range and membrane potential in vitro, a physiological function appears questionable.     

Acetylcholine-induced potassium current of guinea pig outer hair cells: its dependence on a calcium influx through nicotinic-like receptors

The cholinergic efferent inhibition of mammalian outer hair cells (OHCs) is mediated by a hyperpolarizing K+ current. We have made whole-cell tight-seal recordings from single OHCs isolated from the guinea pig cochlea to characterize the mechanism by which acetylcholine (ACh) activates K+ channels. After ACh application, OHCs exhibited a biphasic response: an early depolarizing current preceding the predominant hyperpolarizing K+ current. The current-voltage (I-V) relationship of the ACh-induced response displayed an N-shape, suggesting the involvement of Ca2+ influx. When whole-cell recording was combined with confocal calcium imaging, we simultaneously observed the ACh-induced K+ current (IK(ACh)) and a Ca2+ response restricted to the synaptic area of the cell. This IK(ACh) could be prevented by loading OHCs with 10 mM of the fast Ca2+ buffer bis(2-aminophenoxy)ethane-N,N,N',N'-tetra-acetic acid (or BAPTA), therefore allowing the observation of the ACh-induced early current in isolation. This early current revealed nicotinic features because it activated with an intrinsic delay in the millisecond range, reversed nearly in between potassium and sodium equilibrium potentials, and was blocked by curare. However, it was strongly reduced in the absence of external Ca2+, and its I-V relationship displayed an unusual outward rectification at positive membrane potentials and an inward rectification below -60 mV. The results indicate that the cholinergic response of mammalian OHCs involves a "nicotinic-like" nonspecific cation channel through which Ca2+ enters and triggers activation of nearby Ca2+-dependent K+ channels.     

Expression of Shaker-type voltage-gated potassium channel genes in the guinea-pig

PROBLEM: Inhibin A concentrations in serum may reflect the ovarian granulosa cell compartment. To characterize the correlation between ovarian function after gonadotoxic chemotherapy for Hodgkin's or non-Hodgkin's lymphoma in young women, the immunoreactive inhibin A concentrations in the sera of these patients was measured before, during, and after the gonadotoxic chemotherapy. METHOD OF STUDY: A prospective clinical protocol was undertaken in 20 cycling women with lymphoma, aged 15-40 years. A monthly injection of depot D-TRP6-GnRH-a (Decapeptyl CR, Ferring) was administered from before starting the chemotherapy until its conclusion, up to a maximum of six monthly injections. Most of the patients were treated with the mustargen-oncovin-procarbazine-prednisone (MOPP)/actinomycin D-bleomycin-vincristine (ABV) chemotherapy combination; 13 with and 7 without radiotherapy. A hormonal profile [follicle-stimulating hormone (FSH), luteinizing hormone (LH), 17-beta-estradiol (E2), testosterone (T), progesterone (P4), insulin-like growth factor (IGF)-1, IGF-BP3, and prolactin (PRL)] was taken before starting the gonadotropin-releasing hormone agonist (GnRH-a)/chemotherapy co-treatment and monthly thereafter until resuming spontaneous ovulation and menstrual cyclicity. This group of prospectively treated lymphoma patients was compared with a control group of 22 regularly cycling women who had been treated with chemotherapy (mostly MOPP/ABV) with or without radiotherapy for Hodgkin's or non-Hodgkin's lymphoma. Inhibin A immunoactivity developed by Nigel Groome was measured by an enzyme-linked immunoadsorbent assay (ELISA) commercial kit (Serotec). RESULTS: Whereas all but one (40 years of age) of the surviving patients in the GnRH-a/chemotherapy co-treatment group resumed spontaneous ovulation and menses within 6 months, only one half of the patients in the "control" group (chemotherapy without GnRH-a co-treatment) resumed ovarian function and regular cyclic activity (P < 0.05). The remaining 50% experienced premature ovarian failure (POF). Temporarily increased FSH concentrations were experienced by approximately one third of the patients resuming cyclic ovarian function, suggesting a reversible ovarian damage in a larger proportion of women than those experiencing POF. The inhibin A immunoactive concentrations decreased during the GnRH-a/chemotherapy co-treatment but increased to normal levels in patients who resumed regular ovarian cyclicity, and/or spontaneously conceived, as compared to low levels in menopausal women and those who had developed POF. CONCLUSIONS: If these preliminary data are consistent in a larger group of patients, inhibin A concentration may serve as a prognostic factor for predicting the resumption of ovarian function, in addition to the levels of FSH, LH, and E2.     

Modifications of current properties by expression of a foreign potassium channel gene in Xenopus embryonic cells

The development of excitable cells is characterized by highly organized patterns of expression of ion channels. During the terminal differentiation of Xenopus muscle somites, potassium currents are expressed first just after Stage 15 (early-mid neurula), following a long period during which no voltage-dependent currents can be detected in any cell in the dorsal embryo. We have investigated whether early expression of a foreign delayed rectifier potassium channel may affect this endogenous pattern of electrical development. We injected the purified cRNA of the mammalian brain Shaker-like potassium channel, Kv1.1, into fertilized Xenopus eggs. The resulting currents were analyzed in blastomeres during a 12-hr period prior to Stage 15 and in differentiating muscle cells after Stage 15. In injected embryos, a high fraction of blastomeres expressed a delayed rectifier-type current. The Kv1.1 current could be distinguished from the endogenous muscle delayed potassium current (IK,X) by its very different voltage dependence. Separation of currents based on this difference indicated that, in injected embryos, IK,X appeared much earlier in development than in control embryos. Furthermore, even in cells which expressed solely Kv1.1-type current, the sensitivity of the current to dendrotoxin declined dramatically during development, approaching that of IK,X. These data suggest an interaction between Kv1.1 and endogenous channel subunits, and/or modification of the Kv1.1 protein by the embryonic cells in ways not seen in Xenopus oocytes or mammalian cell lines.     

Motility of isolated vestibular hair cells induced by potassium

Many studies of the outer hair cells in cochlea have demonstrated active motility. However, very few studies have been done on vestibular hair cells. This study was designed to demonstrate the motile responses of isolated vestibular hair cells of the chick, induced by potassium promoting contraction. Reversible cell shape changes were observed in 4 of 6 type I hair cells and 3 of 5 type II hair cells by applying the contraction solution. The cell shape changes were revealed mainly in the cuticular plate and infracuticular region. It was suggested that contraction in the cuticular plate of the isolated hair cells might be converted into tension which increases the stiffness of the sensory hairs and restricts their motions, based on the results of the present study, and the structure of contractile proteins and hair behaviors reported by previous investigators.     

Expression of a potassium current in inner hair cells during development of hearing in mice

Excitable cells use ion channels to tailor their biophysical properties to the functional demands made upon them. During development, these demands may alter considerably, often associated with a change in the cells' complement of ion channels. Here we present evidence for such a change in inner hair cells, the primary sensory receptors in the mammalian cochlea. In mice, responses to sound can first be recorded from the auditory nerve and observed behaviourally from 10-12 days after birth; these responses mature rapidly over the next 4 days. Before this time, mouse inner hair cells have slow voltage responses and fire spontaneous and evoked action potentials. During development of auditory responsiveness a large, fast potassium conductance is expressed, greatly speeding up the membrane time constant and preventing action potentials. This change in potassium channel expression turns the inner hair cell from a regenerative, spiking pacemaker into a high-frequency signal transducer.     

Energy metabolism in cochlear outer hair cells in vitro

ATP levels in outer hair cells in vitro were measured using the luciferin/luciferase method. Hair cells were isolated from the guinea pig cochlea and maintained for 2 h in a balanced salt solution with 5.5 mM glucose. Ten to 20 cells sufficed for a robust and reproducible luminescence signal, indicating an ATP content of 6.2 +/- 0.4 fmol/cell. This ATP concentration is similar to that found in cultures of other cell types and agrees well with the classical measurements in freeze-dried preparations. The ATP levels were reduced by the following treatments: (1) the omission of glucose in the culture medium lowered ATP levels by 28%; (2) the inhibition of glycolysis by 2-deoxyglucose lowered ATP levels by 66%; (3) the inhibition of oxidative phosphorylation by carbonyl cyanide m-chlorophenylhydrazine (CCCP) lowered ATP levels by 75%, and (4) the inhibition of both pathways reduced the ATP content to non-detectable levels. Acetoacetate was able to restore ATP levels partially when glycolysis was inhibited. These results suggest that (1) the major pathway of ATP synthesis in outer hair cells is the aerobic metabolism of glucose; (2) endogenous energy stores (e.g. glycogen) can maintain ATP levels in the absence of glucose; and (3) ketone bodies may be alternative energy sources.     

Dihydropyridines and verapamil inhibit voltage-dependent K+ current in isolated outer hair cells of the guinea pig

Dihydropyridines and verapamil are widely used as blockers of voltage-dependent Ca++ channels. In this work we show that these compounds can have a direct blocking action on a class of voltage-activated potassium channels. Voltage-dependent whole-cell currents were recorded from isolated guinea-pig outer hair cells (OHCs) under conditions such that the free Ca++ concentration in both the internal and external solutions was minimized. A substantial Ca(++)-independent K+ current was revealed by this procedure. Both conventional K+ and Ca++ channel ligands inhibited this current. The order of potency (in terms of the half inhibitory concentrations (IC50) of channel inhibitors) was: nimodipine (6 microM) > Bay K 8644 (8 microM) > verapamil (11 microM) > 4-aminopyridine (22 microM) > nifedipine (32 microM) > quinine (49 microM) > TEA (10236 microM). Except for verapamil, these channel ligands reduced the size of the K+ currents without much alteration of the time course of the currents. In contrast, verapamil caused a more than 10-fold increase in the apparent inactivation rate of the K+ currents without significantly altering the activation of the currents. The observation that relatively low concentrations of calcium channel ligands can directly inhibit potassium currents in isolated OHCs indicates that caution should be taken when these pharmacological agents are used as tools for studying cochlear hair cell physiology.     

Myocardial ischemia/reperfusion protection using monophosphoryl lipid A is abrogated by the ATP-sensitive potassium channel blocker, glibenclamide

OBJECTIVES: Monophosphoryl lipid A (MLA), a detoxified derivative of the lipid A portion of the endotoxin molecule, given as a pretreatment 24 h prior to cardiac ischemia/reperfusion reduces myocardial stunning and infarction in dogs. This study was undertaken to evaluate the ability of MLA pretreatment to reduce infarct size in a rabbit model of in situ regional myocardial ischemia and reperfusion. Secondly, the potential role of modulation of ATP-sensitive potassium (KATP) channel in MLA's cardioprotection was evaluated using in vivo pharmacologic antagonism with a KATP channel blocker, as was the role of tumor necrosis factor using an enzyme-linked immunosorbent assay method of serum cytokine analysis. METHODS: Rabbits were pretreated intravenously with MLA or vehicle injection 24 h prior to initiation of 30 min in situ left anterior descending coronary artery occlusion followed by 3 h reperfusion. In animals receiving glibenclamide, the potassium channel antagonist was administered 30 min prior to inducing ischemia. Animals receiving glibenclamide, which possesses hypoglycemic effects, underwent serial blood glucose evaluation prior to drug and throughout the ischemia and reperfusion periods. Hemodynamics were monitored; infarct size and area at risk were assessed by contrast dye staining (triphenyltetrazolium chloride). Serum tumor necrosis factor was measured by enzyme-linked immunosorbent method in animals administered cardioprotective doses of MLA as well as pyrogenic doses of MLA and endotoxin (positive control) to determine if elaboration of this cytokine could be associated with the cardioprotective effect of MLA. RESULTS: MLA administered as a single intravenous dose 24 h prior to ischemia reduced infarct size, expressed as a percent of the area at risk, 64 and 71% at doses of 35 and 10 micrograms/kg, respectively. Lower doses of MLA (2.5 and 5 micrograms/kg) did not significantly reduce infarct size. Administration of glibenclamide (300 micrograms/kg) 30 min prior to ischemia completely blocked the ability of MLA pretreatment to limit infarct size, while MLA vehicle-glibenclamide-treated control rabbits displayed infarcts not significantly different from MLA-vehicle-treated control rabbits. A cardioprotective dose of MLA (35 micrograms/kg) did not induce the elaboration of tumor necrosis factor into rabbit serum (within the limits of assay sensitivity). CONCLUSIONS: Single-dose pretreatment with MLA administered intravenously to rabbits substantially reduces infarct size when administered 24 h prior to ischemia. Pharmacologic preconditioning with MLA appears to be mediated through KATP channels as the channel blocker, glibenclamide, reversed the cardioprotective activity of MLA when administered 1 day following MLA pretreatment, yet 30 min prior to ischemia. In this model the cardioprotective does not appear to be associated with increases in serum tumor necrosis factor.     

Gadolinium blocks the delayed rectifier potassium current in isolated guinea-pig ventricular myocytes

The effect of Gd3+ on the delayed rectifier potassium current (IK) in single guinea-pig ventricular myocytes was tested using whole-cell patch-clamp techniques. It was found that Gd3+ blocked 70% of the IK tail current at a concentration of 100 microM. The EC50 was 24 microM. Action potential durations were, however, reduced, consistent with a predominant effect on depolarizing L-type Ca2+ current (Ica.L). In the presence of 5 microM nifedipine Gd3+ prolonged the action potential. Using carbon fibres to stretch cells we observed that 10 microM Gd3+ was not effective in reducing a large stretch-activated increase in resting calcium. Modelling studies using the OXSOFT HEART program suggest that this lack of response is influenced by blockade of repolarizing current but is best reproduced by additional blockade of Ca2+ extrusion via the Na(+)-Ca2+ exchanger. When Gd3+ is used as a blocker of stretch-activated channels its actions upon both Ica.L and IK must therefore be accounted for.     

A voltage-sensitive transient potassium current in mouse pancreatic acinar cells

We describe, for the first time, a potassium current in acutely isolated mouse pancreatic acinar cells. This current is activated by depolarization and has many of the characteristics of the fast transient potassium current of neurones where roles in shaping action potential duration and frequency have been proposed. Although acinar cells do not carry action potentials, our experiments indicate that the primary regulator of the current in these cells is the membrane potential. In whole-cell patch-clamped cells we demonstrate an outward current activated by depolarization. This current was transient and inactivated over the duration of the pulse (100-500 ms). The decay of the inactivation was adequately fitted by a single exponential. The time constant of decay, tau, at a membrane potential of +20 mV was 34 +/- 0.6 ms (mean +/- SEM, n = 6) and decreased with more positive pulse potentials. The steady-state inactivation kinetics showed that depolarized holding potentials reduced the amplitude of the current observed with a half-maximal inactivation at a membrane potential of -40.6 +/- 0.33 mV (mean +/- SEM, n = 5). These activation and inactivation characteristics were not affected by low intracellular calcium (10(-10) mol.l-1) or by an increase in calcium (up to 180 nmol.l-1). In addition we found no effect on the current of dibutyryl cyclic adenosine monophosphate (db-cAMP) or the agonist acetylcholine. The current was blocked by 4-aminopyridine (Kd approximately 0.5 mmol.l-1) but not affected by 10 mmol.l-1 tetraethylammonium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Maturation of postsynaptic acetylcholine receptors in cochlear outer hair cells

Sound transduction in the inner ear is controlled by olivocochlear efferents terminating predominantly at outer hair cells (OHC). Development of efferent fibers and thereby of postsynaptic OHC receptors was studied immunohistochemically in 13 cochleae from fetal guinea pigs. The gestational ages of the animals ranged from gestational day (GD) 35 to GD 56. To visualize nicotinic acetylcholine receptors (nAChR), sera were used from myasthenia gravis patients with confirmed nAChR antibodies. At GD 53 no staining was observed, whereas at GD 58 a striking nAChR-immunoreactivity was found. In cochleae from adult animals postsynaptic receptors were visualized at the bases of all three rows of OHCs. The region of the inner hair cells (IHC) was not stained. The present results indicate that nAChRs in guinea pig cochleae develop between GD 53 and GD 58. Maturation of the postsynaptic nAChRs coincides with development of OHC motile properties.     

Epoxyeicosatrienoic acids, potassium channel blockers and endothelium-dependent hyperpolarization in the guinea-pig carotid artery

PURPOSE: To record the on and off responses of the multifocal photopic electroretinogram (ERG) from the human retina and to explore how each ERG component (a-, b-, and d-waves) changes at different retinal eccentricities. METHODS: Multifocal ERGs were recorded with the visual evoked response imaging system. Sixty-one densely packed stimulus elements were square wave-modulated between stimulus on and stimulus off, according to a binary m-sequence at a rate of 4.7 Hz under a constant background illumination. The ERGs were recorded with a bipolar Burian-Allen bipolar contact lens electrode from five normal subjects. Response densities (amplitude per retinal area) were calculated for five different eccentric rings. RESULTS: The response densities for all components (a-, b-, and d-waves) decreased with increasing retinal eccentricities. The ratio of the d-wave to b-wave amplitudes was minimal in the central retina and increased toward the periphery. The ratio of a-wave to b-wave amplitudes also increased toward the peripheral retina. CONCLUSIONS: These results demonstrate that the on and off responses of the human cone ERGs have different spatial distributions across the human retina, and they suggest a change in the photopic retinal circuitry with increasing retinal eccentricities.     

Calcium inflow of hamster Merkel cells in response to hyposmotic stimulation indicate a stretch activated ion channel

The aim of this study was to investigate the existence of the stretch activated ion channels in single Merkel cell using microfluorimetric techniques. Single Merkel cells were dissociated enzymatically from the touch domes in the cheek pouch mucosa of 4-8 week old golden hamsters. They were loaded with calcium (Ca2+) fluorescent indicator fura-2/AM. The increase in intracellular Ca2+ concentration ([Ca2+]i) of a single Merkel cell (quinacrine fluorescent cell) was induced by hyposmotic solution in normal Krebs solution, while it was not induced by Ca2+-free hyposmotic solution in Ca2+-free physiological solution. Gadolinium ion (10 microM) in normal Krebs solution partially blocked the increase in [Ca2+]i of Merkel cells induced by hyposmotic solution. Hence, this study revealed that stretch activated ion channels existed on the Merkel cell membrane.     

A remark on the high-conductance calcium-activated potassium channel in human endothelial cells

Iron plays a central role in the pathogenesis of Mycobacterium tuberculosis, the principal causative agent of tuberculosis. To learn more about iron acquisition by this bacterium, its iron regulated proteins (IRPs) were investigated. Seven IRPs were identified - three increased by high iron concentrations, and four by low iron concentrations. The smallest protein induced by low iron, Irp10, is tightly iron regulated as it is virtually absent in bacteria cultured in the presence of high iron concentrations. The gene (irpA ) encoding this protein and an adjacent open reading frame, mtaA, were cloned and sequenced. The protein encoded by mtaA (Mta72) has striking homology to metal transporting P-type ATPases. This study suggests that Irp10 and Mta72 function as a two-component metal transport system in M. tuberculosis.     

Effects of excitatory neurotransmitters on Ca2+ channel current in smooth muscle cells isolated from guinea-pig urinary bladder

1. A whole-cell voltage clamp technique was used to examine the effects of purinoceptor and muscarinic receptor agonists on voltage-sensitive Ca2+ channels in guinea-pig isolated urinary bladder cells. 2. When the cell membrane was clamped at the holding potential, rapid application of ATP elicited a large inward current in normal solution containing 2.5 mM Ca2+, and reduced the subsequent Ca2+ channel current evoked by a depolarizing pulse (0 mV). Carbachol (CCh) elicited little membrane current, but similarly reduced the Ca2+ current. 3. When purinoceptor agonists were rapidly applied during conditioning depolarizations at +80 mV, an outward current was elicited, and the Ca2+ channel current evoked by the subsequent test potential of 0 mV was not affected. Application of CCh at +80 mV also elicited an outward current, but it reduced the subsequently evoked Ca2+ current. 4. The inhibitory effect of muscarinic agonists on the Ca2+ channel current was attenuated by caffeine (10 mM). 5. In Ca(2+)-free, low-Mg2+ solution, a Na+ current flowing through voltage-dependent Ca2+ channels was evoked by depolarization. This current was not reduced by bath application of purinoceptor agonists (ATP and alpha,beta-methylene ATP). 6. These results suggest that the main effect of purinoceptor stimulation is opening of non-selective cation channels, and that muscarinic stimulation triggers Ca2+ release from intracellular stores. Voltage-sensitive Ca2+ channels are inactivated through an increase in intracellular Ca2+ induced by either activation of purinoceptor or muscarinic receptors.     

Terikalant, an inward-rectifier potassium channel blocker, does not abolish the cardioprotection induced by ischemic preconditioning in the rat

Recent results have shown that the sulfonylurea receptor couples to several types of inward-rectifier potassium (KIR) channels, which suggests that sensitivity to blockade of a pathophysiological phenomenon such as ischemic preconditioning (PC) by glibenclamide may not be the result of this compound selectively blocking the ATP-sensitive potassium (KATP) channel. Therefore, to address this possibility, a role for myocardial KIR v KATP channels in ischemic PC was evaluated in the rat. To test this hypothesis, anesthetized, open-chest, male Wistar rats were assigned to one of seven experimental protocols. Animals assigned to group I (control) received 30 min of occlusion and 2 h of reperfusion. Ischemic PC was produced by 3x5-min occlusion and 2-h reperfusion periods (group II). Terikalant (TK), an inward-rectifier potassium channel blocker, was used to test the role of other K+ channels, most notably the KIR, in the cardioprotective effect of ischemic PC in the rat. TK was given at a dose of 3 mg/kg, i.v., 15 min before the prolonged occlusion and reperfusion periods (group III). In groups IV, V, and VI terikalant (1, 3 and 6 mg/kg, i.v.) was given 15 min before ischemic PC (lowTK+PC, medTK+PC and hiTK+PC, respectively). Group VII consisted of glibenclamide (0.3 mg/kg, i.v.) given 30 min prior to ischemic PC (GLY+PC). Infarct size (IS) as a percent of the area at risk (AAR) was measured using the histochemical stain, 2,3, 5-triphenyltetrazolium chloride. The average IS/AAR for the control was 49.9+/-2.1%. Ischemic PC markedly reduced infarct size (8.6+/-1. 8%; * P<0.05 v control). Terikalant (TK; 1, 3 and 6 mg/kg, i.v.) did not abolish the cardioprotective effect of ischemic PC at any dose (15.5+/-6.4, 16.4+/-5.2 and 8.8+/-1.6%, respectively; * P<0.05 v control). TK itself had no effect on infarct size. GLY completely abolished the cardioprotective effect of ischemic PC (48.2+/-6.4%). In addition, the high dose of TK significantly (P<0.05) increased the action potential duration at 50% repolarization from 48+/-3 to 64+/-4 ms and 30 microM of TK, a concentration which produced a 39% decrease in the inward-rectifier potassium channel current in isolated guinea-pig ventricular myocytes in the whole-cell patch-clamp mode did not block the increase in K ATP current produced by the KATP opener bimakalim (3 microM). These results demonstrate that although the myocardial KATP channel belongs to the K IR superfamily, the endogenous myocardial KIR channel does not mediate ischemic PC in the rat heart; however, the K ATP channel does mediate its cardioprotective effect.     

Fibroblast growth factor receptor expression in outer hair cells of rat cochlea

Fibroblast growth factors (FGFs) are critical for normal development of the organ of Corti, and may also protect hair cells from ototoxic damage. Four different fibroblast growth factors are known, three of which have different splice variants in the extracellular immunoglobin-like (Ig) III FGF-binding domain, giving different patterns of sensitivity to the different FGFs. Analysis of a cDNA library of rat outer hair cells by the polymerase chain reaction, using isoform specific primers, showed expression only of FGF receptor 3, splice variant IIIc. This allows us to predict the pattern of sensitivity to applied FGFs, which may be useful in targeting outer hair cells selectively during an FGF-based strategy for cochlear therapy.     

Calcium-dependent chloride current activated by hyposmotic stress in rat lacrimal acinar cells

Pharmacokinetic and clinical studies on DQ-2556, a new cephem antibiotic, in obstetrics and gynecology were performed and following results were obtained. Concentrations of DQ-2556 were determined in serum, internal genital organs and retroperitoneal exudate after single intravenous administration (i.v.) or drip infusion (d.i.v.) of 1.0 g. Serum levels following i.v. were approximately 30 micrograms/ml at 1 hour, 14 micrograms/ml at 3 hours 30 minutes, and concentrations in internal genital organs including oviduct, ovary, endometrium, myometrium, cervix uteri and portio vaginalis reached approximately 50% to 70% levels of serum concentration. The mean concentration (n = 6) in the retroperitoneal exudate after d.i.v. of 1.0 g following radical hysterectomy were about 20 micrograms/ml, 23 micrograms/ml, 14 micrograms/ml and 8 micrograms/ml at 1 hour, 2 hours 30 minutes, 4 hours 30 minutes and 6 hours 30 minutes, respectively. In clinical trials, DQ-2556 (2.0 g b.i.d. for daily dose) was given in 5 patients with gynecological infections such as pyometra (1 case), salpingitis (1), retroperitoneal space infection (2), pelvic peritonitis (1). The clinical results were evaluated as good in 3 cases and poor in 2 cases including a case with salpingitis infected by Pseudomonas aeruginosa and the other with pelvic peritonitis caused by Methicillin-resistant Staphylococcus aureus. Bacteriologically, 11 organisms were isolated from patients, and eradication rate was 54.5%. Neither side effect nor abnormal laboratory test result was observed. Thus, DQ-2556 appears to be effective for gynecological infections, and the good results were supported by good penetration of the compound into tissues of internal genital organs and retroperitoneal exudate after i.v. or d.i.v.