The effects of catecholamines on electrical activity of neurons in the guinea pig supraoptic nucleus in vitro

The role of the central noradrenergic system in the supraoptic neuroendocrine regulation was investigated using slices of the guinea pig hypothalamus. Noradrenaline produced a complex membrane effect comprising two distinct depolarizations: one, associated with a moderate increase in input resistance and resulting in an augmentation of the spontaneous firing rate; the other, unaccompanied by a detectable change in input resistance and resulting in depression of the firing rate. The former depolarization was reproducible by applying specific alpha-agonist, phenylephrine, whereas the latter was induced by a beta-adrenergic agonist, isoproterenol. The actions of phenylephrine and isoproterenol were blocked by phentolamine and propranolol, respectively. Amplitude of the phenylephrine-induced depolarization was voltage-dependent with the estimated reversal potential of about - 115 mV and changed as a function of [K+]o. On the contrary, amplitude of the isoproterenol-induced depolarization was voltage-independent and was insensitive to changes in external concentrations of K+, Na+, Cl- and Ca2+. We conclude that catecholamines directly modulate the activity of supraoptic neurons through two functionally distinct adrenoceptive sites on neurosecretory cells. The activation of alpha-receptors may increase cellular excitability through suppression of membrane K+ conductance while the activation of beta-receptors would depress neuronal firings, possibly through some mechanism which is not directly linked to ionic channels.

Effect of microstructure of poly(propylene-oxide)-segmented polyamides on platelet adhesion

The relationship between microstructure and platelet adhesivity of six types of poly(propylene oxide) (PPO)-segmented polyamides based on the polyamide segments nylon 210, 310, 410, 510, 610, and 710 were investigated. These multiblock PPO-segmented copolymers were prepared by interfacial polycondensation. Physical characterization of these copolymers was by means of thermal analysis, transmission electron microscope, wide-angle X-ray diffraction (WAXD), and small-angle X-ray scattering (SAXS). The WAXD and SAXS measurements showed that the copolymers had microstructures containing crystalline and amorphous phases and that these microstructures, represented by means of crystallite thickness and long period, varied with incorporation of PPO segments. Blood compatibility of these copolymers was evaluated by estimating the amount of adhering platelets on the copolymer surfaces. The amount of adhering platelets was minimum for the surfaces of the copolymers having a crystallite thickness of 6.0-6.5 nm and a long period of 12-13 nm. This result suggests that the particular size and distribution of the crystalline and amorphous phases in the copolymer could be determining factors for suppressing platelet adhesion on the copolymer surface, and that the control of these factors could lead to ideal antithrombogenic polymers.

Potent depressant action of baclofen on hippocampal epileptiform activity in vitro: possible use in the treatment of epilepsy

Effects of baclofen on the cortical electrical paroxysm were examined using slices of the guinea pig hippocampus. A very low concentration of baclofen (10(-8) M) readily suppressed spontaneous epileptiform discharges of CA3 pyramidal cells, whereas synaptic transmission between mossy fibers and CA3 pyramidal cells were not affected even by 10(-4) M of this drug. Such a strikingly selective depressant action of baclofen on the epileptiform activity raises a possibility that this drug may be effective in the treatment of epilepsy.

[Anti-cancer treatment with prostaglandin synthetase inhibitor in animal models]

Carcinomas produce elevated quantities of prostaglandins (PGs), particularly the E series, which can play an important role in the suppression of the cellular immune reaction in tumor-bearing individuals. These findings have raised the possibility that PG synthetase inhibitor can restore the immune activity against tumors. The anti-tumor activity of indomethacin, a potent PG synthetase inhibitor, was investigated in mice implanted with colon carcinoma 38, colon carcinoma 26 and Lewis lung carcinoma in a series of model studies for cancer treatment in man. Treatment with indomethacin substantially reduced the levels of PGs, particularly PGE2 in tumor tissue, inhibited the tumor growth, particularly the early stage of cell proliferation, prolonged the survival time, eliminated tumors in the abdominal cavity, and inhibited metastatic tumor recurrence after surgery. Also, the treatment reduced the growth of human gastric and colon carcinomas transplanted into nude mice. Thus, indomethacin might also be effective against human carcinomas. It is postulated that PG synthetase inhibitor may prove to be a good therapeutic tool effective against human cancer when used in combination with chemotherapeutic and other immunotherapeutic drugs as well as with low-dose radiation therapy.

Regulatory effects of gastrin and secretin on carcinomas of the stomach and colon

Gastrin (10 micrograms/ml) enhanced 14C-leucine uptake in cultured tissue of stomach and colon carcinomas and content of 14C-labelled protein in the medium was increased. One of 2 stomach and one of 3 colon carcinomas transplanted into nude mice were enhanced in growth by pentagastrin injected in a dose of 250 micrograms/kg every day. On the other hand, secretin (100 U/kg) inhibited the trophic action of pentagastrin.

Pulmonary defence mechanism in mice. A comparative role of alveolar macrophages and polymorphonuclear cells against infection with Candida albicans

The protective roles of alveolar macrophages and polymorphonuclear cells were analyzed against intratracheal challenge with Candida albicans in mice. When mice were treated with carrageenan, a known cytotoxic agent for macrophages, there was no change in susceptibilities to the challenge in terms of the survival and the progressive elimination of fungi from the lung and kidney, in spite of a decreased in vitro phagocytosis of Candida albicans by their alveolar macrophages. On the other hand, irradiated mice (whole body irradiation with 800 rads) showed an enhanced mortality and a progressive growth of Candida albicans in their lungs and kidneys, although no change was observed in the in vitro phagocytic activity of alveolar macrophages until day 6 after irradiation. In normal and carrageenan treated mice, there was a progressive increase in the recruitment of polymorphonuclear cells into the lung after the challenge as shown by bronchoalveolar lavage and histological examination. In irradiated mice, on the other hand, there was a decreased recruitment of polymorphonuclear cells at 24 hr after the challenge, and a complete impairment at a late stage. When phagocytes were obtained from normal mice and examined for in vitro phagocytic activity to Candida albicans, polymorphonuclear cells showed higher activity than that of alveolar macrophages. These results suggest that polymorphonuclear cells play a very important role in the protection against intratracheal infection with Candida albicans.

Reversibility of granulocyte adhesion using polyamine-grafted nylon-6 as a new column substrate for granulocyte separation

Reversibility of leucocytes adhered onto the surface of polyamine-grafted nylon-6 was investigated to estimate its feasibility as a new column substrate for granulocyte separation from whole blood. Polyamine-grafted nylon-6 was synthesized by a radical polymerization of 2-diethylaminoethyl methacrylate monomer onto nylon-6. The surfaces of these graft copolymers were found to show a microphase-separated structure composed of island-like phases of cationic polyamine and continuous phases of nonionic nylon-6. Interaction between leucocytes and these copolymer surfaces was studied by passing rabbit heparinized blood through a column packed with glass beads precoated with these copolymers. Columns of these copolymers showed a selective adhesion of granulocytes among leucocyte populations. Also, the adhering granulocytes were able to be recovered from the column by a gentle elution procedure. From these results, it was concluded that polyamine-grafted nylon-6 having a microphase-separated structure is suitable for use as a column substrate in granulocyte separation from whole blood.

Possible involvement of K+-conductance in the action of gamma-aminobutyric acid in the guinea-pig hippocampus

The mechanism underlying the action of gamma-aminobutyric acid (GABA) in the hippocampus was investigated using guinea-pig brain slices. GABA either superfused or applied directly by microiontophoresis produced a biphasic response in pyramidal cells, comprising hyperpolarizing and depolarizing components. When different concentrations of GABA were applied to the same neurone, the lower concentrations generally produced a hyperpolarization-predominant response, while higher concentrations resulted in a depolarization-predominant response. The depolarizing component of the response to GABA was augmented in a medium containing a low concentration of Cl-, relatively unaffected by a change in external K+ concentration, and blocked by picrotoxin (2 X 10(-5) M). The depolarizing response to GABA persisted in a Ca2+-free medium in which the concentration of Na+ was reduced to 13 mM. Combined application of low doses of picrotoxin and bicuculline eliminated the major part of the depolarizing component of the biphasic response to GABA and produced a relatively pure hyperpolarizing response. The reversal potential of this pharmacologically 'isolated' hyperpolarizing response to GABA was estimated, from the current-voltage relationships, to be about -90 mV and was the same as that of the hyperpolarization induced by baclofen. When the membrane was successively hyperpolarized by inward direct current (d.c.) injections, the reversal point of the 'pharmacologically isolated' hyperpolarizing response to GABA coincided with that of the post-burst hyperpolarization. Low concentrations of Cl- in the bathing medium had no noticeable effect on the hyperpolarizing component of the response to GABA, whereas it markedly increased the amplitude of the depolarizing component. These results suggest that the action of GABA in the hippocampus may involve an activation of K+ conductance.

Baclofen activates voltage-dependent and 4-aminopyridine sensitive K+ conductance in guinea-pig hippocampal pyramidal cells maintained in vitro

The ionic mechanism underlying the effect of (-)-baclofen in the hippocampus was investigated using guinea-pig brain slices. (-)-Baclofen either perfused or applied directly by microiontophoresis hyperpolarized the membrane and decreased the membrane input resistance of pyramidal cells in a dose-dependent manner. The value of the reversal potential for the baclofen-induced hyperpolarization, as estimated from the current-voltage relationships, was about -95mV. The reversal potential of the baclofen-induced hyperpolarization measured directly coincided with that for the post-burst hyperpolarization which is known to result from an activation of Ca2+-activated K+ conductance. The amplitude of the baclofen-induced hyperpolarization was increased in low K+ (1.24 mM) medium whereas the hyperpolarization was decreased or abolished in high K+ (12.4 and 25 mM). Low Cl- (10.2 mM) medium had no noticeable effect on the baclofen-induced hyperpolarization. The effect of baclofen was antagonized by a low dose of 4-aminopyridine (5 X 10(-6) M) whereas it was unaffected by picrotoxin (2 X 10(-5) M). These results strongly suggest that the effect of baclofen is mediated by an increase in K+ conductance.

Characterization of pre- and postsynaptic actions of (-)-baclofen in the guinea-pig hippocampus in vitro

The effects of (-)-baclofen on evoked potentials in the hippocampus were examined through intracellular recordings from guinea-pig brain slices. The evoked responses were recorded in two fibre connections within the hippocampus: the Schaffer collateral/commissural-CA1 pyramidal cell, and the mossy fibre-CA3 pyramidal cell. The Schaffer collateral/commissural-CA1 response was suppressed by (-)-baclofen in concentrations over 2 X 10(-5)M, whereas (+)-baclofen, an inactive isomer, in a concentration of 10(-4)M had no effect on the response. A compound action potential of Schaffer collateral/commissural axons was unaffected by (-)-baclofen even at 10(-4)M, a concentration that almost completely depressed the evoked response in the CA1 pyramidal cell. The mossy fibre-CA3 response was not inhibited by (-)-baclofen (10(-4)M). The depressant action of (-)-baclofen on the Schaffer collateral/commissural-CA1 response was unaffected by bicuculline (10(-4)M), whereas the direct membrane effects of (-)-baclofen were antagonized by bicuculline (10(-5)M). It is suggested that (-)-baclofen may modulate neuronal transmission through presynaptic recognition sites possibly by decreasing transmitter release from nerve terminals and also may directly regulate the endogenous neuronal excitability through an activation of the postsynaptic recognition sites.

A simple perfusion system for brain slice electrophysiology

A simple perfusion system for brain slice experiments was designed to improve stability of intracellular recordings and to enable rapid application of drugs. This system can easily be installed in most conventional apparatuses for electrophysiological experiments, with minimal and inexpensive modifications.

Pharmacological characterization of the magnocellular neuroendocrine cells of the guinea pig supraoptic nucleus in vitro

The effects of various agents which have been implicated in the regulation of vasopressin release, on the supraoptic neuroendocrine cells were studied intracellularly. L-glutamate (10(-4)M) and gamma-aminobutyric acid (10(-6) M) had potent excitatory and inhibitory actions, respectively. Acetylcholine (10(-6) M) depolarized the membrane and increased the membrane input resistance. Norepinephrine (10(-5) M) produced either excitatory or inhibitory action on the spontaneous firing rate depending on the cell impaled. Morphine (10(-8)-10(-6) M) strongly depressed the spontaneous firing rate whereas it has no noticeable effect on the membrane potential and input resistance. Angiotensin II (10(-5) M) had no effect on any of the cells tested.

Protective mechanisms against infection by Listeria monocytogenes: accumulation and activation of macrophages

The protective mechanisms against Listeria monocytogenes were analysed in mice. Listeria immune mice were rechallenged with viable listeria, and the degree of activation of macrophages, the degree of accumulation of macrophages to the infected sites, and these mechanisms were studied. Enhanced acquired resistance to the reinfection became detectable from the early stage of immunization. It was observed that activation of macrophages was mediated by pretreatment with antigen from the early stage of immunization. Enhanced accumulation of macrophages at the infected sites was observed only in the early stage. Enhanced accumulation and activation of macrophages in the early stage were generated by mediators from listeria antigen sensitized T lymphocytes which were different from classical tuberculin type. Enhanced activation of macrophages in the later stage was generated by MAF and/or MIF from sensitized T lymphocytes of classical tuberculin type. It was suggested that acquired cellular resistance to listeria in the early stage depends on both activation and accumulation of macrophages, and that in the later stage depends on activation of macrophages.

[The effects of gastrointestinal hormones on the growth and protein synthesis of gastric carcinomas]

The effects of gastrointestinal hormones on gastric carcinomas were examined in vitro and in vivo. In five of seventeen cases of human gastric carcinomas, the uptake of 14C-leucine into the tumor tissue in organ culture was enhanced by 10 micrograms/ml of gastrin. Also, in four of thirteen cases of human gastric carcinomas, the production of 14C-labelled proteins in medium was increased by gastrin. All the cases in which protein synthesis was enhanced by gastrin were histologically poorly differentiated adenocarcinomas. The effects of gastrin and secretin on the growth of gastric carcinoma, which was serially transplanted in athymic mice, were examined. The doubling time of the tumor was 7.1 days. The doubling time was shortened to 4.1 days by daily administration of 250 micrograms/kg of gastrin. This topic effect of gastrin on gastric carcinoma was inhibited by 100 U/kg of secretin. These results showed that the growth and protein synthesis of gastrointestinal tumor may be regulated by gastrointestinal hormones.

The effects of vasopressin on electrical activity in the guinea-pig supraoptic nucleus in vitro

Brain slices of the guinea-pig hypothalamus were used to determine the effects of vasopressin on intracellular potentials in neurones of the supraoptic nucleus. Vasopressin (0.05-1 i.u./ml.) depolarized the membrane without apparent change in the input resistance and decreased the spontaneous firing rate. This action of vasopressin was retained in the medium containing 0 mM-Ca2+, 12 mM-Mg2+ and 0.3 mM-EGTA. Amplitude of the vasopressin-induced depolarization was voltage-independent. Ion-substitution experiments showed that the changes in [K+]o, [Cl-]o and [Ca2+]o had little effect upon the amplitude of vasopressin-induced depolarization, whereas the depletion of [Na+]o slightly reduced the amplitude. The vasopressin-induced depolarization was blocked at a temperature of 15 degrees C and by ouabain in a dose of 10(-4) M. Dibutyryl cyclic AMP (2 mM) produced electrophysiological effects similar to those seen with vasopressin, and actions of both agents were potentiated by either papaverine (10(-4) M) or theophylline (10(-2) M). Contents of cyclic AMP in tissues incubated with vasopressin were significantly higher than in cases of incubation with normal Krebs solution. We conclude that vasopressin directly modulates the activity of supraoptic neurones, possibly through activation of adenylate cyclase.

BCG-induced susceptibility of mice to challenge with Pseudomonas aeruginosa

Mice infected with Mycobacterium bovis, BCG, were shown to be highly susceptible to subsequent challenge with Pseudomonas aeruginosa. The susceptibility was characterized by the enhanced mortality and shortened survival after challenge with P. aeruginosa. BCG-treated mice did not show any enhanced susceptibility to challenge with Gram-positive bacteria such as Staphylococcus aureus or Listeria monocytogenes. BCG-treated mice eliminated P. aeruginosa from their organs in a pattern similar to that in untreated mice. There was no significant difference in the bactericidal activities of polymorphonuclear cells and macrophages between BCG-treated and untreated mice. An equal amount of endotoxin was detected by the Limulus lysate assay in the blood of both BCG-treated and untreated mice after challenge with P. aeruginosa. The enhanced susceptibility induced by BCG pretreatment could be decreased when the mice were rendered LPS-tolerant by injections of small amounts of LPS. These results suggest that BCG-induced susceptibility to P. aeruginosa can be ascribed to an enhanced susceptibility to the lethal effect of LPS produced by challenge bacteria, and not to the impairment of the ability to eliminate infected bacteria.

Two steps in the generation of acquired cellular resistance against Listeria monocytogenes: accumulation and activation of macrophages

Mice were immunized with 1 X 10(3) viable Listeria monocytogenes, and the mechanism of the acquired resistance against challenge infection with 5 X 10(4) L. monocytogenes was studied by the use of the peritoneal cavity of mice as the site of challenge. An enhanced elimination of bacteria from the peritoneal cavity became detectable on day 5 after immunization, and lasted thereafter. Before day 10 postimmunization, a marked accumulation of macrophages was observed after the challenge but the in vitro listericidal activity of macrophages was not so enhanced. After day 15 postimmunization, peritoneal macrophages did not increase in number after the challenge but the in vitro listericidal activity of macrophages was the stronger. Accumulation of non-activated macrophages seemed to contribute mainly to the expression of acquired resistance against challenge in the early stage of immunization. So-called activated macrophages appeared to be generated only in the later stage of immunization. Thus it was suggested that there may be at least two steps in the expression of acquired listerial resistance.

Substance P decreases membrane conductance in neurons of the guinea pig hypothalamus in vitro

Substance P (SP) depolarized the membrane and increased the spontaneous firing rate of neurons in slices of the guinea pig hypothalamus. These excitatory actions of SP were accompanied by a decrease in membrane conductance, and this reduction was observed even during a perfusion of the medium which was Ca2+ free and in which the concentration of Mg/+ had been increased to 12 mM. Therefore, the contribution of possible presynaptic or indirect effects of SP to the decreased membrane conductance can be ruled out. These observations suggest that SP exerts an excitatory action on neurons in the guinea pig hypothalamus by decreasing the membrane ionic permeability of these neurons.

Ionic mechanism for the osmotically-induced depolarization in neurones of the guinea-pig supraoptic nucleus in vitro

1. Effects of hypertonic solutions prepared by adding NaCl or sucrose to Krebs solution on intracellular potentials were observed in neurones of the supraoptic nucleus using brain slices of the guinea-pig hypothalamus. 2. Hypertonic solutions (306-488 m-osmole/kg) depolarized the membrane, increased the input resistance and augmented the spontaneous firing rate in supraoptic neurones, whereas cells in the hippocampus and anterior or ventromedial hypothalamus were not affected by the hypertonic solutions. 3. The excitatory action of hypertonic solutions on supraoptic neurones was retained in the medium containing 0 mM-Ca2+ and 12 mM-Mg2+. 4. Amplitude of the depolarization induced by superfusion of hypertonic solutions was voltage-dependent. The reversal potential for the depolarization was about -90 mV. 5. The reversal potential for the depolarization induced by hypertonic solution shifted as a function of [K+]0. 6. These results suggest that the supraoptic neurones are themselves osmosensitive and that the local osmotic-related information is transduced to neural signals in these cells by alteration in the membrane ionic permeability, probably due to suppression of K+ conductance.

Effects of penicillin on electrical activities of neurons in guinea-pig hippocampal slices

Epileptogenic action of penicillin (PC) was investigated in thin slices prepared from the guinea-pig hippocampus. Bath-applied PC (1.7 mM) provoked an epileptiform activity. A series of cellular events before during and after application of PC were shown by stable intracellular recording from the same neuron. The effect of PC became progressively pronounced when the temperature of the medium was raised from 30 degrees C to 40 degrees C. PC-induced epileptiform activity showed odd time courses, i.e., recurrent reduction during perfusion of PC and abrupt reversion during washing. Increased potassium concentration in the medium increased the rate of occurrence of the spontaneous epileptiform activity induced by PC. Removal of chloride from the medium converted the PC-induced epileptiform activity to colonic relapsing discharges. In the laminar field potential analysis, 'sink' for the epileptiform activities induced by PC appeared at a broad region of the middle and distal portions of the apical dendrite, whereas 'sink' for potentials considered to reflect mainly synaptic events appeared at a relatively restricted region of the proximal and middle portions of the apical dendrite. Together with other observations, these results led to the conclusion that not only the synaptic but also the non-synaptic process is involved in initiation of the epileptiform activity.

Further support for the postsynaptic action of substance P and its blockade with baclofen in neurons of the guinea-pig hypothalamus in vitro

Effects of substance P on neurons of the guinea-pig hypothalamus in vitro and antagonism between substance P and baclofen were investigated. Substance P increased the firing rate of neurons in the medium containing 0 mM Ca2+ and 12 mM Mg2+. The excitatory action of substance P was antagonized by a low dose of baclofen whereas that of acetylcholine was not antagonized even by much higher doses of baclofen.

Poly(ADP-ribose) synthetase, a main acceptor of poly(ADP-ribose) in isolated nuclei

Poly(ADP-ribose) synthetase was identified as the main acceptor of this polymer produced in isolated nuclei of rat liver. When the nuclei were incubated with [32P]NAD at a limited concentration (2.4 microM) and for a brief period (10 s), a protein with Mr = 110,000 was predominantly poly(ADP-ribosyl)ated, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The modification of this protein increased upon longer incubations or at higher NAD concentrations, and induced a marked increase in the apparent molecular weight. A comparison with poly(ADP-ribose) synthetase (Mr = 110,000) of rat liver under various conditions suggested that the increase in the molecular weight of the acceptor resembled that of the synthetase undergoing multiple auto-poly(ADP-ribosyl)ation. This interpretation was further supported by the following observations: 1) [32P]poly(ADP-ribose) attached to the acceptor co-eluted with the synthetase activity from a hydroxyapatite column; 2) the [32P]poly(ADP-ribose).acceptor complex isolated on the column was converted to a very large complex by further incubation with NAD; and 3) a group of large poly(ADP-ribose).acceptor complexes were reduced to a single molecular species with Mr = 110,000 by extensive digestion with poly(ADP-ribose) glycohydrolase. These findings altogether suggested that poly(ADP-ribose) synthesized in isolated nuclei was principally bound to the synthetase itself.

Electrophysiology of mammalian hypothalamic and interpeduncular neurons in vitro

Electrical activities of the hypothalamic and interpeduncular neurons were studied in vitro in brain slices prepared from the guinea-pig brain stem. Neurons preserved resting membrane potentials comparable to those of neurons in vivo, responded to stimulation of the afferent fibres, and retained stable spontaneous firings for more than several hours.

Characteristics of adrenocortical function, gastrin release and gastric secretion in duodenal ulcer etiology

Measurements of serum cortisol and gastrin along with gastric acid-pepsin secretion in the resting state were carried out in gastric and duodenal ulcer patients. Increased basal corticosteroid concentrations were observed in patients with duodenal ulcer and gastric ulcer. Higher concentrations of the hormone were observed in the former group (P less than 0.05 for the latter). Fasting gastrin levels were significantly higher in gastric ulcer patients where gastric secretion is low than those in duodenal ulcer patients (P less than 0.001). These results suggest that the effect of adrenal cortical hormone on lowering the threshold of oxyntic gland cell reactivity against gastrin is an important factor in duodenal ulcer etiology. Extra-antral control mechanism(s) of gastric acid-pepsin secretion should not be overlooked.

Possible explanation for interictal-ictal transition: evolution of epileptiform activity in hippocampal slice by chloride depletion

In thin hippocampal slices, paroxysmal epileptiform discharge was generated in high potassium medium. Removal of chloride from the high potassium medium caused explosive potentiation of the paroxysmal discharge and emergence of clonic relapsing discharges. Evolution of the paroxysm to regenerative seizure was attributed to the reduction of inhibitory postsynaptic potentials.

Effects of cycloheximide on experimental epilepsy induced by daily amygdaloid stimulation in rabbits

Daily electrical stimulation of the amygdala caused a progressive change in electrographic afterdischarge and behavioral responses that ultimately resulted in generalized convulsions (kindling). Cycloheximide blocked the completion of kindling when administered 4 hours prior to daily electrical stimulations of the amygdala, but exerted no effect when administered shortly before the stimulation. The temporal relation between administration of cycloheximide and stimulation of the amygdala revealed that the blockade of kindling by cycloheximide was due to the suppression of focal afterdischarge rather than to the persistent inhibition of cerebral protein synthesis during the interstimulus periods.