Adenosine A2A receptor-mediated modulation of GABA and glutamate release in the output regions of the basal ganglia in a rodent model of Parkinson's disease

A target neuron of adenosine A(2A) receptor antagonists to exert anti-parkinsonian activities has been currently identified to be, at least in part, striatopallidal medium spiny neurons (MSNs). In the present study, we determine whether A(2A) receptor-mediated modulation is associated with changes in the release of GABA and glutamate in the substantia nigra pars reticulata (SNr), an output structure of the whole basal ganglia network, using in vivo microdialysis in a rat Parkinson's disease (PD) model. In 6-hydroxydopamine (OHDA)-lesioned rats compared with normal rats, basal extracellular GABA levels in the SNr show no change, whereas basal glutamate levels are significantly increased. Oral administration of the A(2A) receptor-selective antagonist (E-1,3-diethyl-8-(3,4-dimethoxystyryl)-7-methyl-3,7-dihydro-1-H-purine-2,6-dion (KW-6002) to 6-OHDA-lesioned rats at 1 mg/kg caused a marked and sustained increase of GABA and glutamate levels in the SNr. The increase of nigral glutamate by KW-6002 was abolished by a kainic acid-induced lesion of the globus pallidus (GP) or subthalamic nucleus (STN) in 6-OHDA-lesioned rats, whereas the increase of nigral GABA was completely blocked by the GP-lesion but only partially blocked by the STN-lesion. These results indicate that changes in neurotransmitter release in the SNr brought about by KW-6002 are largely attributable to blockade of A(2A) receptor-mediated modulation of striatopallidal MSNs. Thus, these actions of KW-6002 on striatopallidal MSNs may be the main mechanism for ameliorating PD by A(2A) antagonists.

Industry forum: Progress in pursuit of therapeutic A2A antagonists: The adenosine A2A receptor selective antagonist KW6002: Research and development toward a novel nondopaminergic therapy for Parkinson's disease

Research and development of the adenosine A2A receptor selective antagonist KW6002 have focused on developing a novel nondopaminergic therapy for Parkinson's disease (PD). Salient pharmacologic features of KW6002 were investigated in several animal models of PD. In rodent and primate models, KW6002 provides symptomatic relief from parkinsonian motor deficits without provoking dyskinesia or exacerbating existing dyskinesias. The major target neurons of the A2A receptor antagonist were identified as GABAergic striatopallidal medium spiny neurons. A possible mechanism of A2A receptor antagonist action in PD has been proposed based on the involvement of striatal and pallidal presynaptic A2A receptors in the "dual" modulation of GABAergic synaptic transmission. Experiments with dopamine D2 receptor knockout mice showed that A2A receptors can function and anti-PD activities of A2A antagonists can occur independent of the dopaminergic system. Clinical studies of KW6002 in patients with advanced PD with L-dopa-related motor complications yielded promising results with regard to motor symptom relief without motor side effects. The development of KW6002 represents the first time that a concept gleaned from A2A biologic research has been applied successfully to "proof of concept" clinical studies. The selective A2A antagonist should provide a novel nondopaminergic approach to PD therapy.

[A case of recurrent gastric cancer successfully treated with TS-1]

A patient with recurrent gastric cancer which infiltrated the pelvic muscle after the treatment of paraaortic lymph node and ovarian metastases was successfully managed by a novel oral anticancer drug, TS-1. TS-1 was administered at a dose of 80 mg/day. One course consisted of two repetitions of consecutive administration of TS-1 for 14 days and withdrawal of TS-1 for 14 days. Adverse reactions were mild and the patient did not request hospitalization after two courses had been completed. Subjective symptoms such as difficulty in walking improved after one week and a partial response was obtained after 2 weeks of treatment. At the end of 4 courses we could remove an indwelling pyelocatheter for the ureter stricture. As of 14 months after the beginning of administration of TS-1, the patient is being treated as an outpatient and has attained a better QOL than before.

Number of glomeruli is increased in the kidney of transgenic mice expressing the truncated type II activin receptor

Histological analyses of the kidney were performed in transgenic mice expressing the truncated type II activin receptor. In these mice, signaling through the activin receptor was attenuated. Size and wet weight of the kidneys were identical to those of normal mice. Histologically, the number of glomeruli was approximately 180% of that in normal mice. The sizes and shapes of the glomeruli were variable, but many of them were smaller than those in normal mice. Morphometrically, the total glomerular area was 130% of that of the normal mice. Abnormality of the epithelia in Bowman's capsule was observed and the number of tubular epithelial cells was increased in the transgenic mice. The serum levels of blood urea nitrogen, creatinine, and creatinine clearance were identical to those in normal mice. These results suggest that the action of activin or related ligands is critical for determination of the nephron number.

Actions of adenosine A2A receptor antagonist KW-6002 on drug-induced catalepsy and hypokinesia caused by reserpine or MPTP

RATIONALE

Current treatment of Parkinson's disease (PD) is based on dopamine replacement therapy, but this leads to long term complications, including dyskinesia. Adenosine A2A receptors are particularly abundant in the striatum and would be a target for an alternative approach to the treatment of PD.

OBJECTIVES

The purpose of this study is to examine the efficacy and potency of the novel selective adenosine A2A receptor antagonist (E)-1,3-diethyl-8-(3,4-dimethoxystyryl)-7-methyl-3,7-dhydro- 1H-purine-2,6- dione (KW-6002) in ameliorating the motor deficits in various mouse models of Parkinson's disease.

METHODS

We evaluated the efficacy and potency of KW-6002 and other reference compounds in the selective adenosine A2A receptor agonist 2-[p-(2-carboxyethyl)phenethylamino]-5'-N-ethylcarboxamidoadenosin e (CGS 21680)-, haloperidol- or reserpine-induced catalepsy models. The effect of KW-6002 on reserpine or 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine hydrochloride(MPTP)-induced hypolocomotion was also examined.

RESULTS

The ED50s of KW-6002 in the reversal of CGS21680-induced and reserpine-induced catalepsy were 0.05 mg/kg, PO and 0.26 mg/kg, PO, respectively. Compared to the ED50 of other adenosine antagonists and dopamine agonist drugs, KW-6002 is over 10 times as potent in these models. KW-6002 also ameliorated the hypolocomotion (minimum effective dose; 0.16 mg/kg) induced by nigral dopaminergic dysfunction with MPTP or reserpine treatment. Combined administrations of subthreshold doses of KW-6002 and L-dopa (50 mg/kg, PO) exerted prominent effects on haloperidol-induced and reserpine-induced catalepsy, suggesting that there may be a synergism between the adenosine A2A receptor antagonist KW-6002 and dopaminergic agents.

CONCLUSIONS

To our knowledge, KW-6002 is the most potent and orally active adenosine A2A receptor antagonist in experimental models of Parkinson's disease, and may offer a new therapeutic approach to the treatment of Parkinson's disease.

Impaired differentiation of endocrine and exocrine cells of the pancreas in transgenic mouse expressing the truncated type II activin receptor

Activin A is expressed in endocrine precursor cells of the fetal pancreatic anlage. To determine the physiological significance of activins in the pancreas, a transgenic mouse line expressing the truncated type II activin receptor under the control of beta-actin promoter was developed. Histological analyses of the pancreas revealed that the pancreatic islets of the transgenic mouse were small in size and were located mainly along the pancreatic ducts. Immunoreactive insulin was detected in islets, some acinar cells, and in some epithelial cells in the duct. In addition, there were abnormal endocrine cells outside the islets. The shape and the size of the endocrine cells varied and some of them were larger than islets. These cells expressed immunoreactive insulin and glucagon. In the exocrine portion, there were morphologically abnormal exocrine cells, which did not form a typical acinar structure. The cells lacked spatial polarity characteristics of acinar cells but expressed immunoreactive amylase, which was distributed diffusely in the cytoplasm. Plasma glucose concentration was normal in the transgenic mouse before and after the administration of glucose. The insulin content of the pancreas in transgenic and normal mice was nearly identical. These results suggest that activins or related ligands regulate the differentiation of the pancreatic endocrine and exocrine cells.

In vivo regulation of acetylcholine release via adenosine A1 receptor in rat cerebral cortex

The roles of the endogenous adenosine on acetylcholine release via adenosine A1 receptor were investigated in rat cerebral cortex using brain microdialysis. Oral administration of KF15372 (8-dicyclopropylmethyl-1,3-dipropylxanthine), a novel selective adenosine A1 receptor antagonist, at doses of 1.25, 5, and 20 mg/kg, significantly increased the extracellular levels of acetylcholine in rat cerebral cortex. Selective A1 agonist N6-((R)-phenylisopropyl) adenosine (R-PIA) did not affect the extracellular level of acetylcholine by both oral (1.25 mg/kg) and intracortical administrations (0.3 microM) via dialysis probe. These results suggest that the extracellular level of acetylcholine is under tonic inhibitory control of endogenous adenosine via the A1 receptor.

Calcium as a second messenger of the action of transforming growth factor-beta on insulin secretion

In MIN6 insulinoma cells, transforming growth factor-beta (TGF-beta) induced the oscillatory elevation of the cytoplasmic free calcium concentration, [Ca2+]c, in the presence of 5.5 mM glucose. The increase in [Ca2+]c induced by TGF-beta was totally dependent on calcium entry and attenuated by nifedipine or nickel chloride. In contrast, carbachol elevated [Ca2+]c in the presence of nickel chloride. When the plasma membrane was hyperpolarized by diazoxide, TGF-beta did not raise [Ca2+]c, whereas both carbachol and depolarizing concentration of potassium elevated [Ca2+]c under the same conditions. TGF-beta did not affect either the cellular cyclic AMP or inositol trisphosphate levels. In the presence of 5.5 mM glucose, TGF-beta induced a 3-fold increase in insulin secretion and the effect of TGF-beta was blocked by either nifedipine or nickel chloride. TGF-beta did not stimulate insulin secretion in the presence of 100 microM diazoxide, whereas both carbachol and 40 mM potassium chloride significantly increased insulin secretion. These results suggest that TGF-beta induces the oscillatory elevation of [Ca2+]c in MIN6 cells by stimulating calcium entry via voltage-dependent calcium channels. Calcium is an intracellular messenger of the action of TGF-beta on insulin secretion.

KF17837: a novel selective adenosine A2A receptor antagonist with anticataleptic activity

KF17837 is a novel selective adenosine A2A receptor antagonist. Oral administration of KF17837 (2.5, 10.0 and 30.0 mg/kg) significantly ameliorated the cataleptic responses induced by intracerebroventricular administration of an adenosine A2A receptor agonist, CGS 21680 (10 micrograms), in a dose-dependent manner. KF17837 also reduced the catalepsy induced by haloperidol (1 mg/kg i.p.) and by reserpine (5 mg/kg i.p.). These anticataleptic effects were exhibited dose dependently at doses from 0.625 and 2.5 mg/kg p.o., respectively. Moreover, KF17837 (0.625 mg/kg p.o.) potentiated the anticataleptic effects of a subthreshold dose of L-3,4-dihydroxyphenylalanine (L-DOPA; 25 mg/kg i.p.) plus benserazide (6.25 mg/kg i.p.). These results suggested that KF17837 is a centrally active adenosine A2A receptor antagonist and that the dopaminergic function of the nigrostriatal pathway is potentiated by adenosine A2A receptor antagonists. Furthermore, KF17837 may be a useful drug in the treatment of parkinsonism.

Adenosine A1 antagonists. 3. Structure-activity relationships on amelioration against scopolamine- or N6-((R)-phenylisopropyl)adenosine-induced cognitive disturbance

The effects of a variety of adenosine A1 and A2 antagonists on N6-((R)-phenylisopropyl)adenosine (R-PIA)- and scopolamine-induced amnesias were investigated in rodents in order to clarify the role of adenosine receptors in learning and memory. Some of the selective adenosine A1 antagonists exhibited antiamnesic activities at several doses where they did not induce an increase of spontaneous locomotion. These results suggest that the blockade of A1 receptors is more important than that of A2 receptors in learning and memory. Detailed studies of structure-activity relationships of adenosine A1 antagonists in two amnesia models demonstrated that there were three types of adenosine A1 antagonists: (A) Compounds 3-5 (8-substituted 1,3-dipropylxanthines) ameliorated the shortened latency in both models. (B) Compounds 7-11 (8-substituted 1,3-dialkylxanthines) and 19-21 (imidazo[2,1-i]purin-5(4H)-one derivatives) ameliorated the shortened latency in the (R)-PIA-induced amnesia model but not in the scopolamine-induced amnesia model. (C) Compounds 14-16 ameliorated the shortened latency in the scopolamine model but not in the (R)-PIA model. Aminophenethyl-substituted compounds C did not exhibit adenosine A1 antagonism in vivo presumably due to rapid metabolism. The dramatic change in the activities of A and B could not be explained by their simple pharmacokinetic differences because both types of compounds showed clear blockade of central adenosine A1 receptors in the (R)-PIA model. 8-(3-Dicyclopropylmethyl)-1,3-dipropylxanthine (5) (KF15372) was chosen for further studies and is currently under preclinical development as a cognition enhancer.

[Effects of KW-6055, a novel benzylpyridine derivative, on central cholinergic systems]

We examined the effect of KW-6055 [alpha-(p-butyrylamino-o-nitrobenzyl) pyridine], which has anti-amnesic activity, on the central cholinergic systems of rat frontal cortex using in vivo brain microdialysis. 1) KW-6055 (40, 160 mg/kg, p.o.) increased the extracellular level of ACh in normal rats (257 +/- 23, 202 +/- 24%). The stimulating effect of KW-6055 on ACh release was abolished by tetrodotoxin treatment, supporting that the released ACh was due to neuronal firing. Reserpine pretreatment decreased the effect of KW-6055, indicating that KW-6055 acted on cholinergic neurons through catecholaminergic neurons. 2) In basal forebrain-lesioned rats, KW-6055 (40 mg/kg, p.o.) significantly increased the extracellular level of ACh (251 +/- 22%) for more than 2 hr, which was longer than in normal rats. In conclusion, these results suggest that the stimulating activity on ACh release may be involved in the mechanism of the anti-amnesic effects of KW-6055.

Renal transplantation from HLA-haploidentical living-related donors: the effects of donor-specific blood transfusions and different immunosuppressive regimens

One-hundred-nine HLA-haploidentical living related renal transplants have been retrospectively analysed to compare the effect of donor-specific blood transfusion (DST) and different immunosuppressive regimens on graft survival and acute rejection. The recipients were divided into four groups according to the immunosuppressive therapy. Group 1 (n = 44): conventional therapy with posttransplant azathioprine (AZP) + methylprednisolone (MP). Group 2 (n = 25): pretransplant DST + posttransplant AZP + MP. Group 3 (n = 12): triple-drug therapy with posttransplant AZP + MP + cyclosporine (CS). Group 4 (n = 25): pretransplant DST + posttransplant AZP + MP + CS. The five-year actuarial survival rates for groups 1, 2, 3 and 4 were 48%, 73%, 79%, and 89%, respectively. The graft survival rate in group 3 was significantly (p less than 0.01) better than that in group 1. The transfusion effect was reduced, and appears as a 10% improvement in the graft survival in the cyclosporin era compared with a 25% improvement at pre-cyclosporin era. Furthermore, the incidence of the first rejection episode was decreased in recipients that received DST. The present study revealed that DST, as pretransplant conditioning has a definite impact on rejection-free long-term graft survival in HLA-haploidentical living-related kidney recipients and the most favorable outcome in such patients could be achieved by DST pretreatment in conjunction with posttransplant triple-drug therapy including cyclosporine.

The impact of triple drug immunosuppression on clinical results of cadaveric kidney transplantation: a comparison of conventional immunosuppression

A retrospective study was carried out in 110 cadaveric kidney transplant recipients to compare the effects of low doses of cyclosporine (CsA), azathioprine (AZP) and steroids (triple-drug therapy) with those of higher doses of steroids plus AZP (conventional immunosuppression). Graft survival rate in the triple-drug therapy was 77%, 69%, and 69% at 1, 3, and 5 years, respectively. This was significantly better than 48%, 34%, and 29% in conventional immunosuppression. The incidence of acute rejection episodes was significantly lower in the triple-drug therapy than in conventional immunosuppression (25% vs 58%). In conclusion, our study shows that triple-drug therapy using low-dose cyclosporine is the safest of the immunosuppressive regimens and provides a beneficial effect on the long-term survival of cadaveric kidney transplants.

Augmentation of antitumor effect on syngeneic murine solid tumors by an interleukin 2 slow delivery system, the IL-2 mini-pellet

We evaluated the antitumor effect of an interleukin 2 (IL-2) slow delivery system, the IL-2 mini-pellet, in two murine solid tumor models, and also investigated the enhancement of its therapeutic effect by serial administration. The IL-2 mini-pellet contains 1 x 10(6) units of IL-2 and releases it slowly in vivo. In our experiment, the IL-2 mini-pellet was administered subcutaneously near the tumor site in combination with the intravenous injection of lymphokine-activated killer (LAK) cells. When this regimen was given on days 8 and 11 after the subcutaneous inoculation of Meth A fibrosarcoma into BALB/c mice, tumor growth was significantly inhibited (p less than 0.05) compared to tumor growth in untreated controls. Moreover, the IL-2 mini-pellet alone was also effective in inhibiting tumor growth. In another experiment, MH134 hepatoma was inoculated into C3H/He mice. Both administration of the IL-2 mini-pellet alone and in combination with LAK cells resulted in complete tumor regression in four of five mice. In a third experiment, serial administration of the IL-2 mini-pellet at 3- or 5-day intervals prolonged the suppression of Meth A fibrosarcoma growth in BALB/c mice. These results suggested that the IL-2 mini-pellet could be applied to cancer immunotherapy and that its antitumor effect could be prolonged by serial administration.

[Effect of Euro-Collins' or UW solution on the early graft function following cadaveric kidney transplantation]

From November 1985 to March 1990, 55 cadaveric kidney transplants were performed under cyclosporine therapy. All kidneys were harvested from non-heart beating donors and cold stored after being flushed with EC solution (Group I, n = 27) or UW solution (Group II, n = 28). Warm ischemic time (min) in groups I and II were 7.1 +/- 3.3 and 6.9 +/- 2.3, respectively. Cold ischemic times (hr) in groups I and II were 6.9 +/- 2.4 and 8.4 +/- 2.8, respectively. Mean numbers of days for postoperative dialysis were 14.0 +/- 7.9 in group I and 7.9 +/- 5.8 in group II (p less than 0.05). One-month creatinine (mg/dl) was 2.9 +/- 2.8 in group I and 1.75 +/- 1.0 in group II (NS). One-month graft survivals (%) in groups I and II were 81.4% and 92.8%, respectively. In conclusion, UW solution has provided beneficial effect of preservation on ischemic damaged kidney and appears to be method of choice in non-heart beating cadaveric kidney transplantation.

Application of an interleukin 2 slow delivery system to the immunotherapy of established murine colon 26 adenocarcinoma liver metastases

We evaluated the antitumor effect of an interleukin 2 (IL-2) slow delivery system, the IL-2 minipellet, using a murine hepatic metastasis model. The IL-2 minipellet consists of atelocollagen derived from natural bovine skin together with 1 x 10(6) units of recombinant IL-2. Administration of the IL-2 minipellet was performed into the spleens of BALB/c mice after translocation of the spleens to the s.c. position. Administration produced detectable serum IL-2 levels for 72 h. The IL-2 minipellet was evaluated for its efficacy against hepatic metastases from colon 26 adenocarcinoma in the BALB/c mice. Both the administration of the IL-2 minipellet alone and its combination with the injection of 5 x 10(7) lymphokine-activated killer cells resulted in significant reductions of the number of metastatic nodules. Moreover, increased survival of mice bearing colon 26 adenocarcinoma was noted in these two treatment groups. To investigate the mechanism of the IL-2 minipellet activity, we tested the lytic potential of splenocytes obtained after administration of the IL-2 minipellet in a 51Cr release assay. Cytotoxicity against YAC-1 cells and colon 26 cells was significantly augmented on Day 2 after minipellet administration. These results demonstrated that local administration of the IL-2 minipellet into the hepatic circulation was extremely effective against metastatic liver cancer.

Clinical application of cascade filtration combined with glassbead adsorbents in cancer patients

Cascade filtration (CF) was applied to patients with advanced cancers. To selectively remove immunosuppressive factors with molecular weight lower than albumin, adsorbents combined with CF were examined. Among 11 kinds of adsorbents, glassbead adsorbents with pore size 100A were the most effective in adsorbing such substances. Clinically, a column packed with glassbead adsorbents was concomitantly used with CF. The second filtrate was passed through the column and returned to the patient. The removal rate of immunosuppressive substances with molecular weight lower than albumin was only 20% by CF alone, but more than 50% by CF combined with glassbead adsorbents. Clinical symptoms such as severe back pain and general malaise were drastically improved during and after therapy. These results suggest that CF combined with glassbead adsorbents is an effective adjunctive modality to cancer therapy.

Clinical Application of Cascade Filtration Combined with Glassbead Adsorbents in Cancer Patients

Cascade filtration (CF) was applied to patients with advanced cancers. To selectively remove immunosuppressive factors with molecular weight lower than albumin, adsbor-bents combined with CF were examined. Among 11 kinds of adsorbents, glassbead adsorbents with pore size 100A were the most effective in adsorbing such substances. Clinically, a column packed with glassbead adsorbents was concomitantly used with CF. The second filtrate was passed through the column and returned to the patient. The removal rate of immunosuppressive substances with molecular weight lower than albumin was only 20% by CF alone, but more than 50% by CF combined with glassbead adsorbents. Clinical symptoms such as severe back pain and general malaise were drastically improved during and after therapy. These results suggest that CF combined with glassbead adsorbents is an effective adjunctive modality to cancer therapy.

Development of an interleukin-2 slow delivery system

The authors developed a slow delivery system for interleukin-2 (IL-2) using highly purified bovine collagen to overcome the rapid clearance and side effects of IL-2; 1 X 10(6) microns of recombinant human IL-2 was successfully infused into needle-shaped "IL-2 mini-pellets". Pharmacokinetic study in C57BL/6 mice revealed that a single subcutaneous injection of an IL-2 mini-pellet could prolong IL-2 retention and decrease maximal concentration in the serum. Elimination half-life was 360 min for subcutaneously injected IL-2 mini-pellets, while it was 8 and 15 min, respectively, for intravenous and subcutaneous injections of aqueous IL-2. No side effects were observed throughout the experiment. This slow delivery system using collagen as a carrier proved to be effective and may be applicable to other kinds of drugs.

Effects of flunarizine on induced nystagmus and cochlear blood flow

The effects of flunarizine on induced nystagmus and cochlear blood flow were compared with those of cinnarizine and diphenidol. Flunarizine significantly inhibited caloric (cool water)-induced nystagmus frequency and duration of nystagmus in rabbits at 5 mg/kg i.v., whereas cinnarizine and diphenidol only slightly decreased the frequency of nystagmus at 5 mg/kg, i.v. As for optokinetic stimuli-induced nystagmus in rabbits, flunarizine significantly decreased the amplitude of nystagmus at 2.5 mg/kg i.v., and cinnarizine and diphenidol inhibited nystagmus at 5 mg/kg, i.v. Flunarizine had no effect on nystagmus induced by electrical stimulation of the lateral geniculate body in rabbits at doses up to 5 mg/kg, i.v. Flunarizine increased the cochlear blood flow in anesthetized guinea pigs dose-dependently (0.312-1.25 mg/kg i.v.) On the other hand, cinnarizine (0.625-2.5 mg/kg i.v.) and diphenidol (0.625-2.5 mg/kg i.v.) increased cochlear blood flow, but the duration of action of both cinnarizine and diphenidol was shorter than that of flunarizine at the same dose. As stated above, flunarizine inhibited nystagmus experimentally induced by caloric or optokinetic stimuli. Increased cochlear blood flow suggested that the enhancement of vestibular blood flow might play an important role in the treatment of vestibular dysfunctions with this drug.

Effects of serum fractions obtained from cancer patients by double-filtration plasmapheresis on tumor growth and metastasis in mice

We administered serum fractions obtained from cancer patients by double-filtration plasmapheresis (DFPP) to cancer-bearing mice to examine the effects on tumor growth and metastasis. Fraction 1 (whole plasma), fraction 2 (a plasma fraction containing substances with higher particle size), fraction 3 (a plasma fraction containing substances with smaller particle size) and saline were administered intravenously to cancer-bearing mice for 10 days following the inoculation of tumor cells. The tumor growth and metastasis in mice administered fraction 2 was far more rapid than that in the control mice. On the other hand, tumor growth in mice administered fraction 3 was significantly delayed compared with that in mice injected with fraction 2. These results suggest that factors in the higher particle-size fraction of cancer patients' sera promote the growth and the metastasis of tumors in mice, and that DFPP, which remove these factors, is an effective therapy against cancer.

Artificial liver support for postoperative hepatic failure with anion exchange resin (BR-601)

An artificial liver support system for plasma exchange and plasma perfusion through BR-601 resin using a membrane separator was applied to 5 patients with postoperative liver failure. Percent absorption of total and direct bilirubin, and of bile acids were 77.1 +/- 6.4, 78.4 +/- 6.1, and 93.4 +/- 3.6%, respectively, when 250 ml of plasma was treated. Percent reductions in total and direct bilirubin, and in bile acids were 24.5 +/- 5.8, 25.5 +/- 5.8 and 30.9 +/- 8.5%, respectively. In contrast, percent reductions in total and direct bilirubin, and in bile acids by plasma exchange were 30.9 +/- 13.3, 34.5 +/- 12.5 and 24.2 +/- 8.5%, respectively. The coma grade was improved in 4 out of 5 cases, but unfortunately the patients did not recover. In conclusion, plasma perfusion through BR-601 resin is expected to play a promising role in artificial liver support systems because of its capacity to absorb bilirubin and bile acids.

Occurrence of S-adenosylhomocysteine hydrolase in prokaryote cells. Characterization of the enzyme from Alcaligenes faecalis and role of the enzyme in the activated methyl cycle

The occurrence of S-adenosylhomocysteine hydrolase (EC 3.3.1.1) was found in a variety of prokaryotes. These prokaryotes did not exhibit any activities of S-adenosylhomocysteine nucleosidase (EC 3.2.2.9) and S-ribosyl-homocysteine hydrolase (EC 3.3.1.3), which had been the generally accepted prokaryote enzymes for the regeneration of free homocysteine from S-adenosylhomocysteine in the activated methyl cycle. In these prokaryotes S-adenosylhomocysteine hydrolase was suggested to be the only enzyme functioning for the regeneration of free homocysteine by enzymological and immunochemical studies. S-Adenosylhomocysteine hydrolase was purified and crystallized from cells of a prokaryote, Alcaligenes faecalis. The purified enzyme was found to be homogeneous on ultracentrifugation and gel electrophoresis. Its relative molecular mass is approximately 280 000 and it is composed of six identical subunits with a Mr of approximately 48 000. The NH2-terminal and COOH-terminal amino acids are lysine and tyrosine respectively. The enzyme contains 6 mol NAD/mol. Some nucleosides, such as formycin A, nebularine, adenosine N1-oxide and so on, are able to substitute for adenosine yielding the corresponding S-nucleosidylhomocysteine congeners. Modification of the 5'-hydroxymethyl group in adenosine leads to the most potent inhibition of the thioether formation of homocysteine with adenosine. The enzyme from A. faecalis has some immunological similarities to other prokaryote S-adenosylhomocysteine hydrolases, but is different from the enzymes of animal sources.

[Effects of flunarizine on nystagmus and cochlear blood flow]

The effects of flunarizine (1.25-5 mg/kg, i.v.), a cerebral vasodilator, on nystagmus were compared with those of cinnarizine (2.5-5 mg/kg, i.v.) and diphenidol (2.5-5 mg/kg, i.v.) in rabbits. Flunarizine produced significant decrease in the beat number and duration of caloric-induced nystagmus. On the other hand, cinnarizine and diphenidol decreased the beat number, but hardly shortened the duration. In the same way, these three drugs suppressed the amplitude of the corneocortical potential induced by optokinetic stimulation. However, flunarizine up to 5 mg/kg had no effect on central nystagmus induced by unilateral stimulation to the lateral geniculate body. Flunarizine (0.312-1.25 mg/kg, i.v.), cinnarizine (0.625-2.5 mg/kg, i.v.) and diphenidol (0.625-2.5 mg/kg, i.v.) markedly increased the blood flow in the radiating arteriole of cochlea in the anaesthetized guinea pig. The duration of their increasing activities was in the following order: flunarizine greater than or equal to cinnarizine greater than diphenidol. From these results, it is suggested that the suppression of nystagmus by flunarizine may be at least partly due to the favorable effect on microcirculation in the vestibular organ.

Effects of KW-5338 (domperidone) on gastric motility

The effects of KW-5338 (domperidone) on gastric motility were studied by the balloon method in pentobarbital anesthetized mongrel dogs. KW-5338 was found to enhance the antrum motility. Its enhancement pattern showed the following characteristics: (1) The tonus was not affected, (2) the contraction pressure increased, (3) the frequency of contraction decreased slightly, and (4) the enhancement was long lasting. Metoclopramide showed strong but short enhancement of antrum motility. KW-5338 augmented also the gastric body motility, although the enhancement pattern was different from that in the antrum: (1) The action did not last so long, and (2) an increase in tonus was observed. The augmentation of the gastric motility by KW-5338 was observed even after vagotomy and splanchnicotomy, but it was weaker and shorter than in the intact state. THe KW-5338 induced augmentation was diminished by tetrodotoxin treatment. The gastric relaxation response to dopamine was blocked by KW-5338. These results show that KW-5338 activates the gastric motility not only by central mechanism but also by stimulation to intramural neurons. The dopamine blocking activity of KW-5338 might play some role in the enhancement of gastric motility.

[Effects of caerulein on intestinal motility (author's transl)]

Effects of caerulein on intestinal motility have been studied in comparison with those of neostigmine, pantethine, prostaglandin E1 (PGE1) and prostaglandin F2alpha (PGF2alpha). Caerulein facilitated electric discharges in the intestinal tracts of anaesthetized rabbits and exhibited a greater potency than either neostigmine or pantethine. The small intestine was more sensitive to this agent than was the large intestine. PGE1 inhibited while PGF2alpha facilitated electric discharges in the small intestine. A complete inhibitory effect of the excitatory of caerulein was not demonstrated with atropine. Caerulein promoted the transit of charcoal meal through the intestine of the mouse and was approximately 30 times more potent than was neostigmine. At high doses, the promotion was reduced and the reduction was inhibited by reserpine or phentolamine-propranolol. Our observations indicate that caerulein produces a catecholamine releasing action in high doses. Caerulein promoted the transit in the cecectomized mice at doses 30 times larger than given to intact mice. Caerulein, neostigmine, PGE1 and PGF2alpha produced an excitatory effect on the isolated intestine of the rabbit. Minimal effect concentrations were 3 X 10(-10 approximately 10(-9), 10(-8), 10(-9) and 3 x 10(-11) g/ml in the ileum and 3 X 10(-9) approximately 10(-8), 10(-8) approximately 3 x 10(-8), 10(-10) and 10(-11) g/ml in the proximal colon, respectively.

Pharmacological studies of caerulein. II. The possibility of mediation through the central nervous system

With low doses of caerulein given intravenously or subcutaneously, vomiting could be induced. Although vomiting was not inhibited by chlorpromazine or atropine, a strong inhibition was evident when metoclopramide was administered subcutaneously at such doses as inhibit vomiting induced by oral administration of CuSO4. Even high doses of caerulein failed to induced vomiting in vagotomized and splanchnicotomized dogs. With intraventricular injection, no effects were observed on blood pressure, respiration or gastrointestinal motility, and vomiting was not induced. Therefore, a reflex mechanism appears to be involved in vomiting induced by caerulein. It is suggested that the actions of caerulein may not be mediated through the central nervous system.