Effects of acetaldehyde on electrical activity during neuroeffector transmission in guinea-pig vas deferens

The effects of acetaldehyde on electrical activity during sympathetic neuroeffector transmission were studied in the guinea-pig vas deferens. Application of 1 mM acetaldehyde produced a slow depolarization of the smooth muscle membrane. The amplitudes of facilitated excitatory junction potentials (EJPs) evoked by nerve stimulation were slightly decreased. A higher concentration of acetaldehyde (5 mM) initially hyperpolarized and later depolarized the membrane. The decrease in EJP amplitudes was more pronounced during hyperpolarization. Acetaldehyde (5 mM) increased the frequency of the spontaneous EJPs and reduced their amplitudes, whereas action potentials in postganglionic nerves were unaffected. Acetaldehyde (1-5 mM) decreased the amplitudes of EJPs in vasa pretreated with reserpine but did not alter the resting membrane potentials. The decrease in the EJP amplitudes together with the hyperpolarization of the membrane could be responsible for the early inhibitory effect of acetaldehyde on neuroeffector transmission. The slow depolarization, which is presumably mediated by endogenous noradrenaline, may cause the late facilitatory effect.

Effects of acetaldehyde on contractile response to nerve stimulation in guinea-pig vas deferens

Twitch contractions of the isolated guinea-pig vas deferens induced by sympathetic nerve stimulation were augmented by acetaldehyde (0.1-10 mM). With high concentrations (5-10 mM), acetaldehyde produced a biphasic response consisting of an initial brief depression and a subsequent potentiation of the contraction. The late effect was associated with repetitive contractions that were not prevented by tetrodotoxin. A low concentration of phentolamine (27 microM) increased and a high concentration (1.3 mM) suppressed the potentiating action of acetaldehyde. Acetaldehyde did not induce contractions in surgically sympathectomized vasa or vasa pretreated with reserpine. Acetaldehyde caused a dose-dependent increase in noradrenaline release into the bathing fluid. The study shows that acetaldehyde has a dual effect on sympathetic neuroeffector transmission, and that an increase in noradrenaline secretion appears to contribute to the late facilitatory effect in the isolated vas deferens.

[Effects of ketamine on voltage-dependent Ca2+ current in single smooth muscle cells from rabbit portal vein]

The effects of ketamine on membrane potentials and voltage-dependent Ca2+ current were studied in dispersed single smooth muscle cells from rabbit portal vein. The resting membrane potential (-56.2 +/- 1.5mV) was not affected by ketamine (10(-5)-10(-3)M). The duration and the amplitude of the action potential evoked by intracellular stimulation were significantly decreased by ketamine in the concentrations of 10(-4)M and 10(-3)M. Voltage-gated Ca2+ current in single smooth muscle cells was apparently decreased by ketamine at concentrations of between 10(-5)M to 10(-3)M. The activation threshold of Ca2+ current (approx. -30mV) was also decreased by ketamine. Therefore, these results suggest that inhibition of the contractile response by ketamine in vascular smooth muscle from rabbit portal vein may be attributable to the inhibition of the Ca2+ current.

Effect of OPC-8490 on the membrane potentials and membrane currents of single guinea-pig myocytes

The direct actions of OPC-8490 on mammalian myocardium were examined by determination of the drug's effects on the action potentials of isolated guinea-pig single ventricular cells and on the underlying ionic currents. OPC-8490 (10(-6) to 10(-4) M) did not alter the resting membrane potential, but rather produced a dose-dependent prolongation of the duration of the action potential. The amplitude of the action-potential plateau was also increased by OPC-8490. Whole-cell voltage clamp experiments revealed that OPC-8490 blocks myocardial delayed outward K+ current (IK), which regulates repolarization of the action potentials. However Ik1, which regulates the resting membrane potential, was not changed by OPC-8490. Ca current (ICa) was increased by OPC-8490 in a dose-dependent and reversible manner. These results suggest that OPC-8490 augments the plateau amplitude and increases the duration of the action potentials by not only increasing ICa, but also by decreasing delayed outward K+ currents. Moreover, OPC-8490 did not affect the intracellular concentration of cyclic AMP in single cells. The OPC-8490 increase in ICa was thus unlikely to be mediated by a process involving cyclic AMP.

Two distinct types of inwardly rectifying K+ channels in bull-frog atrial myocytes

1. Single atrial myocytes were enzymatically isolated from the bull-frog as previously described (Hume & Giles, 1981), and patch-clamp techniques were used in an attempt to identify and separate two inwardly rectifying K+ channels in this tissue. 2. Single-channel measurements consistently demonstrated the existence of two different resting K+ channels, which both exhibited strong inward rectification. The unitary conductances of these K+ channels were 34 +/- 4 and 22 +/- 3 pS (mean +/- S.D., at 22-24 degrees C) when measured with 110 mM-K+ in the pipette solution, and their mean open times were 0.87 +/- 0.33 and 129.9 +/- 49.4 ms, respectively. 3. In the absence of acetylcholine (ACh) in the pipette, openings of the larger channels with the shorter open times occurred at a very low frequency. When ACh was present in the patch pipette, the activity of this channel increased significantly, although the single-channel conductance and gating behaviour were very similar either with or without ACh in the pipette. 4. The zero-current voltage (extrapolated from the inward currents through these types of channels) depended on the extracellular K+ concentration. [K+]o, in the fashion expected for a predominantly K(+)-selective channel: it shifted by 58 mV for a tenfold change in [K+]o. Very similar results were obtained from whole-cell voltage-clamp measurements (53 mV for a tenfold change in [K+]o). 5. The conductance of both types of K+ channels depended on [K+]o. The single-channel conductances were 25 +/- 3 and 13 +/- 2 pS with 50 mM [K+]o, and 19 +/- 4 and 9 +/- 2 pS with 20 mM [K+]o, respectively. 6. These results demonstrate that two types of resting inwardly rectifying K+ channels can be identified in single atrial myocytes. One of these is an inwardly rectifying K+ channel (IK1) previously identified in whole-cell voltage-clamp experiments (Hume & Giles, 1983). The second channel is the muscarinic receptor-regulated K+ channel (IK(ACh) which was first described in mammalian nodal and atrial cells. 7. N-Ethylmaleimide (NEM), a reagent which alkylates sulphydryl groups, affects these two types of K+ channels differentially. In the cell-attached patch configuration, bath application of NEM (50 microM) completely abolished the activity of IK(ACh), without affecting the IK1 channel activity. 8. To obtain further evidence that these two currents, IK1 and IK(ACh), were different, the inside-out patch-clamp technique was used.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of the anti-allergic agent tranilast in the urinary bladder of rats as demonstrated by light microscopic radioautography

Tranilast (N-(3,4-dimethoxycinnamoyl)anthranilic acid), an anti-allergic drug, has been developed and used for the treatment of anaphylactic hypersensitivity such as bronchial asthma in Japan. Recently, many cases with eosinophilic cystitis associated with administration of this drug have been reported. In a series of studies to elucidate the pathoetiology of this unusual cystitis, the distribution of tranilast in urinary bladder of rats was investigated. Light microscopic radioautography using tritiated tranilast showed that this drug was localized specifically in the transitional epithelial cells of the mucosa and the endothelial cells of venous vessels for a fairly long time after an oral administration. These results should be taken into consideration in further studies of this drug-associated cystitis.

Studies on antidiabetic agents. Synthesis and hypoglycemic activity of 5-[4-(pyridylalkoxy)benzyl]-2,4-thiazolidinediones

The synthesis of a series of 5-[4-(pyridylalkoxy)benzyl]-2, 4-thiazolidinediones is described. These compounds were evaluated for hypoglycemic and hypolipidemic activities in genetically obese and diabetic mice, yellow KK. 2-(2-Pyridyl)alkoxy derivatives were found to have much better hypoglycemic and hypolipidemic activities than 2-(3-pyridyl)- and 2-(4-pyridyl)alkoxy derivatives or even the previously reported compound, ciglitazone. The introduction of a hydroxyl group at the 2-position of the ethoxy chain potentiated the activities. Among the potent compounds, pioglitazone (AD-4833) was selected as a candidate compound.

Effects of TYB-3823, a new antiarrhythmic drug, on the electrophysiological properties of guinea-pig ventricular muscles

1. The effects of TYB-3823 (B-GYKI 38233), a new antiarrhythmic drug, were electrophysiologically examined in the guinea-pig ventricular muscles. 2. TYB-3823 at concentrations of 1-3 x 10(-7) M significantly prolonged the action potential duration (APD) of the papillary muscle. However, the resting potential, action potential amplitude and maximum rate of depolarization (Vmax) were unaffected by the drug at such concentrations. At a higher concentration (1 x 10(-4) M) TYB-3823 reduced Vmax. 3. Voltage clamp experiments with single ventricular cells revealed that TYB-3823 at concentrations higher than 1 x 10(-7) M reduced the outward potassium currents, especially the time-dependent outward current, but that TYB-3823 failed to affect the calcium current. 4. These results suggested that TYB-3823 at low concentrations reduces the outward potassium current to give rise to a prolongation of APD and that at higher concentrations it additionally inhibits the sodium channels; both the effects may be related to the antiarrhythmic action of this drug.

Enhancement of inflammatory reactions in a non-immunological air pouch model in rats

In a carboxymethyl cellulose (CMC) air pouch inflammation model, accumulation of exudate decreased at a relatively rapid rate and almost disappeared 3 days after a 2% CMC injection into the preformed air pouch. After a second injection of 2% CMC solution into the 1-day-old CMC pouch on the day following the first CMC injection, the decrease in rate of exudate was similar to the change seen after the first CMC injection. In another group of rats, 3 days after the first CMC injection when inflammation had subsided, a second injection of 2% CMC solution into the 3-day-old CMC pouch resulted in a marked increase of exudate accumulation, inflammatory cell infiltration and vascular permeability. Histologically, large numbers of macrophages accumulated in the 3-day-old CMC pouch and fibroblast proliferation and newly formed blood vessels were also visible. The enhanced exudative reaction was significantly inhibited by dexamethasone but not by indomethacin. These results indicate that the enhanced inflammatory reactions appear to be closely correlated with the increase of reactivity at the site of inflammation and the exudative reaction was not mediated by cyclo-oxygenase products.

Renal cell carcinoma: oncocyte type

A case of oncocyte-type renal cell carcinoma was reported. The tumor had developed from the upper posterior portion of the left kidney and was well circumscribed. However, the tumor showed expansion into the intraparenchymal space, invasive growth, and venous invasion. Marked cell atypia was not observed.

Radiorespirometric patterns of 14C-substrates in rats. I. Differences in kinds of 14C-substrates and their structural positions labelled with 14C

Experiments were conducted by radiorespirometry to elucidate the relation between the respiratory 14CO2 wave pattern derived from intravenously injected 14C-substrates and the dispositional partition of these substrates in rats. Two types of 14C-methionine and 4 types of 14C-glucose molecules were used as the 14C-substrates. The respiratory 14CO2 wave patterns obtained in experiments using 14C-methionine substrates revealed different patterns based on differences in the labelled position and the amount of expired 14C-radioactivity as well as the wave height. The experiments using 14C-glucose substrates reveals that the carbon atoms participate equally in forming the respiratory 14CO2 wave pattern, regardless of their position in the glucose molecule. Moreover, differences in wave height as a result of differences in position of the labelled carbon atom were not observed. Results of 90-minute 14CO2 radioactivity recovery rate substantiated the explanation of the above-described relationship. The experiments also clarified that wave height is determined by rate of partition to the CO2 pathway of intermediate metabolites arising in the process of labelled 14C atom disposition.

Effects of halothane on membrane ionic currents in guinea pig atrial and ventricular myocytes

We studied the effects of halothane on membrane potentials and ionic currents in single guinea pig atrial and ventricular cells prepared by an enzymatic dispersion procedure. In both atrial and ventricular cells, action potential overshoot and its plateau phase were significantly decreased by halothane (2%) without change in resting potential. However, the duration of the ventricular action potential measured at 90% repolarization was markedly shortened by halothane (2%) (to 60% of control), whereas that of the atrial action potential did not change significantly. Corresponding voltage clamp experiments demonstrated that in atrial cells halothane (2%) significantly depresses the time- and voltage-dependent outward K+ current (IK) (to 46% of control); and that in ventricular cells IK is then nearly absent. In both atrial and ventricular cells halothane had no effect on the inwardly rectifying K+ current (IK1). On the other hand, halothane (2%) decreased the slow inward Ca2+ current (ICa) in both atrial and ventricular cells (to 36% and 29% of control, respectively). The results suggest that the shortened action potential in ventricular cells by halothane may well be responsible for the decrease of the plateau phase resulting from the depression of ICa; and that in atrial cells the depression of IK and ICa by halothane had no significant effect on the duration of action potential.

Temperature-controlled perfusion apparatus for microscope using transparent conducting film heater

We describe a novel temperature-controlled perfusion apparatus for electrophysiological studies on isolated cells or membrane patches. The apparatus uses a transparent conducting film of indium-tin-oxide as a heating element. The film heater deposited on a glass sheet allows us to construct a structurally simple apparatus that is able not only to heat directly the bath chamber but also to preheat the perfusion solution on the stage of an inverted microscope. The structure ensures a uniform temperature in a bath chamber that has a working area of approximately 6 X 12 mm2 and a capacity of 1 ml. A control unit, designed for operation of the apparatus, regulates the temperature of the bathing solution without introducing electrical noise in a range from ambient temperature to greater than 37 degrees C with an accuracy within +/- 1 degree C. The apparatus is 12 mm in height and designed to fit on the stage of a standard inverted microscope. Since the bath chamber for perfusion experiments is readily interchanged with others, the apparatus can be used widely in microscopic studies of various cells in static solutions.

Autoradiographic characterization of newly developed melanoic cell group different from the melanoic tumor piece embedded into a liver lobe of mice

Secondary proliferous melanoic tumors grew at 100% of probability in a liver lobe of C57BL/6 mouse with a piece of B16 melanoma tumor embedded successfully in the lobe. Clear border between host liver tissues and the embedded tumor piece was observed 14 days after embedding. No division image was noted in cells of the embedded tumor piece. In all regions surrounding the embedded tumor piece, there were few accumulations of leucocytes, lymphocytes, or giant cells, indicating a strong likelihood of immune reaction or antigen-antibody reaction, although there was active formation of fibroblast bunds and production of lysosomal enzymes. Secondary proliferous melanoic tumors developed in the environment of liver tissue separately from the embedded tumor location. Results of 14C-thymidine-nuclear labeling of embedded tumor cells showed that the majority of the labeled cells did not migrate or divide. In the case of 14C-thymidine-labeling of host liver tissue cells, results indicated no transfer of 14C-radioactivity into nuclei of embedded tumor cells, although there was positive distribution of 14C-radioactivity into nuclei of proliferous cells in the secondary tumor, a newly developed melanoic cell group. When prelabeling was performed the average density of autoradiographic image over the secondary tumor was equivalent to that over the normal liver tissue at the early stage such as 7 days after embedding and decreased with time after that. The newly developed melanoic cells were particularly exciting and proliferous, because they received much more labeling of 14C-thymidine as compared to liver tissue cells that was provided by one shot labeling of the radioactive tracer 1 h. before sacrifice of tumor embedded mice. There was no development of secondary melanoic cells in the liver lobe in case of embedding of a tumor piece previously by wrapping with a membranefilter, less 5 microns in pore size.

Effects of halothane on membrane potentials and membrane ionic currents in single bullfrog atrial cells

Halothane exerts negative inotropic and negative chronotropic actions on the isolated heart in experimental animals. In order to assess directly the actions of halothane in myocardium, we studied the effects of halothane on membrane potentials and transmembrane ionic currents in single isolated frog atrial cells obtained by the enzymatic dissociation method. The results show: (a) that the action potential is prolonged and its plateau phase and overshoot are depressed, but the resting potential remains unchanged; (b) that there is a significant inhibition of a time- and voltage-dependent outward K+ current and a slow inward Ca2+ current, with a slight decrease of a fast inward Na+ current following halothane (1.0-4.0%) application; and that halothane has no effect on another K+ current, time-independent current.

Ultrastructural study on the meninx of the goldfish brain

The cranial meninges of the goldfish were studied by means of transmission electron microscopy combined with the freeze-fracturing technique. The goldfish has three cranial meninges. The outer layer consists of flattened cells, which are stratified in 3 to 7 layers and are packed densely with many interdigitations of cell processes. The constituent cells in the outer layer have copious smooth endoplasmic reticulum and are joined by gap junctions but have no desmosomes. The intermediate layer is thin, continuous, and single cell. In the replicas, both the upper and the lower surfaces of the intermediate layer cells have numerous openings of pinocytotic vesicles, but the upper surface is characterized by round gap junctions, whereas the lower surface is identified by a linear continuation of a combination of tight junctions and gap junctions and by desmosomes. The lateral surface has a hexagonal network of tight junctions and gap junctions with internally located desmosomes, which functions as a barrier to intercellular movement of lanthanum. The inner layer consists of a meshwork of reticular cells and large intercellular spaces, in which fine granular material, capillaries, and different types of blood-derived free cells can be found. Cells in the inner layer contain rough endoplasmic reticulum stacked in lamellae and have irregular processes joined by desmosomes. The goldfish meninges are compared with the meninges of mammals.

Light microscopic radioautographic study of the localization of an anti-allergic agent, Tranilast, in rat mast cells

In order to demonstrate the localization of an anti-allergic agent, Tranilast, in the mast cells, light microscopic radioautography was performed. The mast cells collected from rat peritoneal cavity were incubated for 0 to 60 min in a medium containing 3H-Tranilast. After the incubation, they were fixed, embedded and processed for light microscopic radioautography. The radioautographic silver grains were frequently localized around and over the cytoplasmic granules and their number increased according to the prolongation of incubation time. From the results obtained at present it was demonstrated that Tranilast was rapidly taken into the cytoplasm of mast cells. This phenomenon may suggest an important role of this agent in the inhibition of allergic reactions of mast cells.

Prolongation of the action potential and reduction of the delayed outward K+ current by halothane in single frog atrial cells

Halothane has been shown to produce significant changes in heart rate and strength of contraction. We have studied the mechanism(s) of these effects by recording action potentials and transmembrane ionic currents in single cardiac cells from bullfrog atrium. Our results show that the action potential was prolonged and its plateau was depressed; and that there was a significant inhibition of a potassium current, Ik, and a Ca2+ current, Isi, following halothane (2%) application.

Comparison of the in vitro development of mouse single blastomeres with and without the zona pellucida

No difference was observed during in vitro development between mouse single blastomeres with and without the zona pellucida, isolated from 2- and 4-cell stage eggs.