Location of functional regions of acetylcholine receptor alpha-subunit by site-directed mutagenesis

The availability of cloned cDNAs encoding the four subunits of the Torpedo acetylcholine receptor, which can be expressed to make functional receptors in Xenopus oocytes, has made possible a detailed investigation of the functions of the different structural components of the receptor. The functional analysis of receptors with alpha-subunits altered at specific sites by site-directed mutagenesis of the cDNA has allowed the location of specific regions of the alpha-subunit molecule involved in acetylcholine binding and forming a transmembrane ionic channel.

Mitomycin C carrying microspheres as a novel method of drug delivery

Biodegradable albumin microspheres containing about 5% mitomycin C (MMC) were prepared in an average diameter of 45 +/- 8 microns by heat denaturation in oil at 120 degrees C and/or cross-linking with glutaraldehyde. These MMC microspheres released, in vitro, about 20% of the contained MMC for over 3 days, and they were intra-arterially infused into albino rabbits and Wistar rats, as a preclinical model of intra-arterial infusion treatment for patients with inoperable hepatic tumor. We infused these microspheres into the femoral artery of rabbits with a VX-2 tumor implanted into the flank of the hindleg. High levels of MMC were maintained for several hours in the tumor and the entrapped MMC microspheres were detected within arterioles in the VX-2 tumors. The growth of VX-2 tumor was inhibited considerably, compared to findings in the control rabbits given conventional MMC. In the next studies, MMC microspheres were infused into the rat hepatic artery, and the levels of MMC in the hepatic vein blood were maintained at much the same concentration for over 2 hours after the infusion, in marked contrast to rapid decreases in the conventional MMC. Histologic findings revealed that MMC micro-spheres were entrapped within the hepatic arterioles for over 2 weeks and released biologically active MMC into the neighboring tissues for prolonged periods of time.

[Effects of nizofenone on ischemic cerebral edema in Mongolian gerbils]

The effects of nizofenone on ischemic cerebral edema in Mongolian gerbils were compared with those of pentobarbital (PBT). Water content, used as an index of cerebral edema, was calculated from the wet and dry weights of each hemisphere. In the sensitive gerbils subjected to permanent occlusion of the right common carotid artery, water content of the right hemisphere increased by about 6% at 24 hr after ischemia. In the animals treated with nizofenone (30 mg/kg i.p.) and PBT (60 mg/kg i.p.), water content was significantly lower than that of the control group at 24 hr and 1.5-24 hr after ischemia, respectively. In the sensitive gerbils subjected to temporary occlusion of the right common carotid artery for 60 min, water content of the right hemisphere increased gradually by about 5% at 72 hr after recirculation. In the animals treated with nizofenone (30 mg/kg i.p.) and PBT (60 mg/kg i.p.), water content was significantly lower than that of the control group at 24-72 hr and 1.5-72 hr after recirculation, respectively. Nizofenone became effective in lowering brain water content after 24 hr following ischemia. On the other hand, PBT was effective from an early stage of ischemic cerebral edema. Brain edema following an ischemic injury is considered to be initially of the cytotoxic type, subsequently changing into the vasogenic type. The above results suggest that nizofenone may be effective in ameliorating ischemic cerebral edema, particularly vasogenic edema, and that this may be partially related to its cerebral protective action.

Antitumor agent poly (amino acid) conjugates as a drug carrier in cancer chemotherapy

Antitumor agent melphalan was conjugated through a carbodiimide-catalyzed reaction to poly (L-lysine) (71.3K and 2K) and poly (L-glutamic acid) (60K and 14K) at a ratio of approximately one molecule per 7-lysyl and 23-glutamate residues, respectively. These conjugates had 40-70% of alkylating activities by themselves in vitro as compared with free melphalan. Poly (glutamic acid) conjugates showed the antitumor activity in vivo against Yoshida sarcoma in rats. In addition, poly (glutamic acid) conjugates containing 3H-phenylalanine which was used as a model compound instead of melphalan had a sustained release property of radioactivity and the release rates could be regulated by exopeptidases. After subcutaneous injection as the first choice of routes of administration, moreover, the conjugates were found to be absorbed through the lymphatic transport system, probably due to the macromolecularity. These results suggest that the melphalan-poly (amino acid) conjugates are one of good candidates to attain the sustained release and targeting of drugs in cancer chemotherapy.

[Effect of nizofenone (Y-9179) on experimental cerebral ischemia in Mongolian gerbils]

The cerebral protective action of nizofenone was compared with that of pentobarbital (PBT) in Mongolian gerbils in which an incomplete circle of Willis causes the development of ischemic damage in the cerebral hemispheres following common carotid arteries occlusion. The mean survival time following occlusion of both common carotid arteries which induced a mortality rate of 100% was 2.3 hr for the control group and 3.3 hr (P less than 0.05) and 4.1 hr (P less than 0.01) for the animals pretreated with nizofenone (10 mg/kg) and PBT (60 mg/kg), respectively. The mortality rate during a 1 month period following transient bilateral occlusion of the carotid arteries for 30 min was 100% for the control group and 41% (P less than 0.01) and 40% (P less than 0.01) for the animals pretreated with nizofenone (30 mg/kg) and PBT (60 mg/kg), respectively. No significant protective action was observed when administration of the drugs was carried out immediately after the onset of recirculation. These results suggest that nizofenone may be an effective cerebral protective agent.

Intra-arterial administration of heated albumin microspheres containing mitomycin C to rabbits with VX-2 tumor

In an attempt to enhance antitumor effects, we prepared heated albumin microspheres containing mitomycin C (MMC). These MMC microspheres have an average diameter of 45 +/- 8 micrometers and contain about 5 per cent of MMC. The intra-arterial MMC microsphere treatment, for albino rabbits with implanted VX-2 tumor, increased remarkably the tissue MMC levels, compared to that with conventional MMC, and resulted in conspicuous antitumor efficacy. This approach to antitumor chemotherapy should be effective for selected patients with malignant tumor receiving a blood supply from an end-artery.

Opioid activity of enkephalin analogues containing the kyotorphin-related structure in the N-terminus

The pharmacological activity of eight analogues of enkephalin containing L-Arg or D-Arg in position 2 were examined. All peptides showed weaker inhibitory effects than those of naturally-occurring enkephalins on the isolated guinea-pig ileal longitudinal muscle and the mouse vas deferens. On the contrary, these eight peptides were more potent than enkephalins in the analgesic test involving intracisternal administration to mice. By the intravenous route, only D- Arg2 -Met5-enkephalin, which induced a most potent analgesia by intracisternal injection, was effective. D- Arg2 -Met5-enkephalin showed a similar binding affinity to that of Met5-enkephalin in the opioid mu-receptor binding assay, but had a lower delta-receptor binding affinity than did Leu5-enkephalin. Administration of thiorphan , an enkephalin dipeptidyl carboxypeptidase inhibitor, did not potentiate the analgesic effect of D- Arg2 -Met5-enkephalin, whereas it dramatically enhanced the effect of D-Ala2-Met5-enkephalin, when both drugs were administered concomitantly into the cisterna magna of mice.

Expression of functional acetylcholine receptor from cloned cDNAs

The cloned cDNAs encoding the four subunits of the Torpedo californica acetylcholine receptor, each carried by a simian virus 40 vector, direct the synthesis of the functional receptor in a combined expression system consisting of COS monkey cells and Xenopus oocytes. Our results suggest that all four subunits are required to elicit a normal nicotinic response to acetylcholine, whereas only the alpha-subunit is indispensable for alpha-bungarotoxin binding activity.

Continued in vitro and in vivo release of an antitumor drug from albumin microspheres

Heated albumin microspheres with an average diameter of 45 +/- 8 microns and containing mitomycin C, released, in vitro, about 20% of this antibiotic over a 3-day period. VX-2 tumors were implanted into the hind leg of rabbits and the drug-containing microspheres were injected into the femoral artery of these animals. High levels of the drug were maintained for several hours in the tumor and growth of the tumor was inhibited considerably, compared to findings in control rabbits given the conventional mitomycin C. Half the number of the rabbits treated with our new method are alive with no evidence of tumor.

[Studies on biodegradable microspheres containing mitomycin C]

For the purpose of enhancing antitumor effects, we prepared heated albumin microspheres containing an antitumor drug, mitomycin C. The biodegradable MMC microspheres which have an average diameter of 45 +/- 8 mum contain approximately 10% of MMC and release in vitro approximately 20% of the MMC over 3-day period. The microspheres were injected into albino rabbit femoral artery of the hind leg into which a VX-2 tumor had been implanted. Peripheral blood levels of MMC were reduced as compared to the conventional MMC group, within 60 minutes after injection. Subsequently in the MMC-microsphere administered rabbits, the level was higher than in the conventional MMC administered group. The survival of VX-2 tumor-bearing rabbits prolonged markedly with MMC microspheres.

Cloning and sequence analysis of cDNA for ovine corticotropin-releasing factor precursor

Previously, Guillemin and Rosenberg and Saffran and Schally demonstrated the presence of hypothalamic factors that stimulated the secretion of adrenocorticotropic hormone (ACTH) by the pituitary gland. Recently, Vale et al. have isolated and sequenced an ovine hypothalamic peptide of 41 amino acids, which is believed to represent the major physiological corticotropin-releasing factor (CRF) (reviewed in refs 5, 6). Available data suggest that hypothalamic CRF enhances both the synthesis and secretion of ACTH and related peptides such as beta-endorphin and beta-lipotropin (beta-LPH) (reviewed in ref. 6), which are all derived from the common precursor, termed ACTH-beta-LPH precursor or preproopiomelanocortin (reviewed in ref. 7). Because CRF mediates the neural control of the pituitary-adrenocortical system, the characterization of its biosynthetic precursor and the gene encoding it is essential for understanding the molecular mechanism underlying the endocrine response to stress. We have now cloned DNA sequences complementary to the ovine hypothalamic mRNA encoding the CRF precursor (referred to hereafter as prepro-CRF). The nucleotide sequence of the cloned cDNA, reported here, has revealed the primary structure of prepro-CRF. The carboxyl end represents the CRF sequence preceded by the tetrapeptide, Arg-Lys-Arg-Arg, and followed by the dipeptide, Gly-Lys. Comparison of the amino acid sequence of prepro-CRF with those of the ACTH-beta-LPH precursor and the arginine vasopressin-neurophysin II precursor suggests that these precursor proteins may be evolutionarily related.

Use of magnetic emulsion as a novel drug carrier for chemotherapeutic agents

Magnetic guidance of magnetic emulsion for site specific delivery was investigated in vitro and in vivo. The magnetic emulsion was characterized in vitro for its magnetic responsiveness using a constant flow apparatus, and its high retention by magnetic field was confirmed. After intravenous injection in rat, magnetic emulsions were localized to the predetermined site (lungs) by application of an electromagnet to the lungs. Similarly, 1-(2-chloroethyl)-3-(trans-4-methylcyclohexyl)-1-nitrosourea (methyl-CCNU) contained in the dispersed oily phase of the emulsions, was also concentrated at the target-site. Such preferential localization by magnetic means suggested that magnetic emulsions could become effective drug carriers with site specificity for the delivery of chemotherapeutic agents in cancer chemotherapy.

Isolation and sequence analysis of the human corticotropin-releasing factor precursor gene

A human genomic DNA segment containing the gene for the corticotropin-releasing factor precursor has been isolated by screening a gene library with an ovine cDNA probe. The cloned DNA segment has been subjected to restriction endonuclease mapping and nucleotide sequence analysis. Comparison of the nucleotide sequence of the gene with that of the ovine cDNA indicates that an intron of 800 bp is inserted in the segment encoding the 5'-untranslated region of the mRNA. The segment corresponding to the protein-coding and the 3'-untranslated region of the mRNA is uninterrupted. The mRNA and amino acid sequences of the human corticotropin-releasing factor precursor have been deduced from the corresponding gene sequence. The deduced amino acid sequence of human corticotropin-releasing factor exhibits seven amino acid substitutions in comparison with the ovine counterpart.

[Change of pattern of gastric emptying after selective proximal vagotomy]

The patterns of gastric emptying after selective proximal vagotomy (SPV) and SPV with pyloroplasty (SPV + D) were studed using a liquid labelled with 99mTc-DTPA. By means of on-line computer facility, it was possible to analyse the relative role of the Whole stomach and the antrum within the overall frame work of gastric emptying. In the time/activity curve of the whole stomach, all of 3 groups emptied in exponential curve. Comparing with normal subjects, SPV subjects were tending to empty slowly, while SPV + D subjects were tending to empty rapidly. In the time/activity curve of the antrum, normal and SPV + D subjects had two types of emptying--one was represented in the decreasing curve and another was represented in the increasing-decreasing curve. While SPV subjects had only one type of emptying which was represented in the increasing-decreasing curve. From a consideration of the pattern of gastric emptying curve, SPV subjects had two different emptying states compared with normal subjects--one was the delay of entering the antrum from the fundic side of stomach, and the other was that effective antral emptying did not readily start. While SPV + D kept more neally normal gastric emptying that it of SPV.

Mechanisms of cerebral protection by pentobarbital and nizofenone correlated with the course of local cerebral blood flow changes

The effects of delayed administration of pentobarbital and a novel imidazole derivative (Nizofenone or Y-9179) on the infarction size following the regional cerebral ischemia were studied using the permanent middle cerebral artery (MCA) occlusion model in cats. The courses of local cerebral blood flow (lCBF) before and after drug administration were also studied using the hydrogen clearance method. The extent of infarction one week after MCA occlusion was significantly smaller in the drug-treated groups than in the control group. Regarding the time-course of lCBF, there was no significant differences between the control and the Y-9179 groups. On the other hand, pentobarbital administration caused a significant lCBF increase in low-flow areas where the lCBF following MCA occlusion was below 40 ml/100g/min. In spite of this flow increase, the corresponding cortical areas underwent infarction. Histological examination of the state of vasogenic edema revealed that the perivascular exudation of plasma fluid in the infarcted area was definitely less in the Y-9179 treated group than in the other groups. Results indicate that redistribution of lCBF may not be involved in the mechanism of cerebral protection by pentobarbital or Y-9179.

Cloning and sequence analysis of cDNA for porcine beta-neo-endorphin/dynorphin precursor

The primary structure of a precursor protein that contains beta-neo-endorphin, dynorphin and a third leucine-enkephalin sequence with a carboxyl extension has been deduced from the nucleotide sequence of cloned DNA complementary to the porcine hypothalamic mRNA encoding it. The three peptides are each bounded by Lys-Arg. This precursor protein, like adrenal preproenkephalin and the corticotropin/beta-lipotropin precursor, comprises multiple repetitive units and a cysteine-containing amino-terminal sequence preceded by a signal peptide.

[The influence of pentobarbital and Y-9179 on regional cerebral blood flow and infarction size in the middle cerebral artery occlusion model in cats (author's transl)]

Following permanent occlusion of the middle cerebral artery (MCA) in cats, the effect of delayed administration of pentobarbital (PBT) and a novel imidazole derivative (Nizofenone or Y-9179) on the regional cerebral blood flow (rCBF) was studied. The rCBF was measured for one week by the hydrogen clearance technique without anesthesia. The overall effects of these drugs on histological changes were also assessed. Twenty-four animals, in which platinum electrodes were chronically implanted in the ten predetermined positions, were divided into following three groups. The control, PBT and Y-9179 groups received the vehicle, PBT (25 mg/kg/day) and Y-9179 (6.25 mg/kg/day), respectively. Drug administration was started 30 min after MCA occlusion and continued for three days. In the affected hemisphere of the animals which survived for one week, histological examination revealed ischemic lesions composed of the marginal, reactive and central zones. The infarction ratio calculated as the ratio of the damaged area to the whole hemispheric area was significantly smaller in the drug treated groups than in the control. In the Y-9179 group, the reduction of the area comprizing the central and reactive zones was particularly prominent. There were no apparent differences in the time-course of the rCBFs between the control and Y-9179 groups. Each channel showed reduction of the rCBF following MCA occlusion. Although slight fluctuations of the rCBF were seen during the first three to four hours, the initially dropped rCBF remained stable in both groups. In the PBT group, on the other hand, an increase of the rCBF took place following the administration of the drug in the area where the rCBF was initially reduced less than about 40 ml/100g/min after MCA occlusion. Most of the electrodes showing such an increase in the rCBF topographically corresponded to the reactive or boundary zone. In the control group, vasogenic edema characterized by the perivascular exudation of plasma fluid was prominent in the periphery of the central zone as well as in the inner layer of the reactive zone. Such changes were almost absent in the Y-9179 group, whereas it was more evident and close to the control in the PBT group. So far as the correlation between the course of the rCBF and the final histological outcome was examined, there was no evidence indicating the beneficial effect of the redistribution of the rCBF by PBT. Y-9179 had no significant action on the course of the rCBF but its anti-edema effect might be related to its cerebral protective action. The mechanism of cerebral protection by PBT or Y-9179 needs further clarification.

[Effect of acetyllactoylcholine-1,5-naphthalene disulfonate on the motility of stomach]

The effect of TM-723 on the motility of stomach was investigated by using the electromyogram, extraluminal strain gauge force transducer in dog and by measuring the human gastric emptying time. Three mongrel dogs were equipped with two bipolar electrodes on the serosal surface of the antrum and single bipolar electrode and single strain gauge on the surface of the body. Both the peristaltic spike discharge and contractile activity were recorded during 30 minutes before and 60 minutes after administration of TM-723 1 mg/kg, 3 mg/kg and 5 mg/kg, iv. The peristaltic spikes were suddenly disappeared on administration of TM-723 and after then, recurrent peristaltic spikes were recognized with prolonged interval and increased propagation velocity for about four minutes. The contractile activity increased with the administration of TM-723 for a minute. Gastric emptying time were measured on four healthy men by using of the test meal containing 300 muCi of 99mTc-DTPA before and after administration of TM-723 50 mg per os. The following results were obtained that three of four men had accelerated emptying time and one had no remarkable changes after taking TM-723. These studies suggest that TM-723 activates the motility of the stomach.

Biomedical applications of magnetic fluids II. 1) preparation and magnetic guidance of magnetic albumin microsphere for site specific drug delivery in vivo

Magnetic guidance of magnetic albumin microsphere for site specific delivery was investigated in mice and rats. After intravenous injection in mice, magnetic microspheres with 1 and 3 micrometer diameter size were localized and retained in the target-site (lung) by application of two permanent magnets to the lungs. Injection into the renal artery in rats also indicated that the 1-micrometer microspheres were concentrated in the kidney by a magnetic field. When the magnets were not applied, however, the microspheres following intravascular injection were concentrated mainly in the liver, regardless of the route of administration. Such preferential localization by magnetic means suggested that magnetic albumin microspheres could become effective drug carriers with site specificity for the delivery of chemotherapeutic agents in cancer therapy.

Relative potency in acute and chronic suppressive effects of prednisolone and betamethasone on the hypothalamic-pituitary-adrenal axis in man

The relative potency in the hypothalamic-pituitary-adrenal (HPA) suppression of both prednisolone and betamethasone was examined in an acute study with normal volunteers and in a chronic study with glucocorticoid-treated patients. Circadian rhythm of plasma cortisol was studied after a single dose administration of 5 to 30 mg prednisolone or 0.5 to 3.0 mg betamethasone at 8:00 hr. Morning-rise of plasma cortisol occurred on the morning after the administration of 30 mg or less prednisolone but no morning rise was noted after the administration of 1.0 mg or more betamethasone. Plasma ACTH was slightly elevated on the morning after 30 mg prednisolone administration but showed low levels throughout the night after 3.0 mg betamethasone administration. Plasma cortisol responsiveness to ACTH was examined in patients before and during therapy with either prednisolone or betamethasone. The basal cortisol level was not suppressed and the responsiveness to ACTH remained nearly normal during long-term 5 mg prednisolone therapy, but these were completely suppressed during long-term 5 mg betamethasone therapy. The responsiveness to ACTH was nearly normal in patients receiving alternate-day therapy with prednisolone in such large doses as 50 or 60 mg every other day, but was completely suppressed in patients receiving 1.0 mg betamethasone every other day. The relative potency of betamethasone in acute and chronic suppressive effects on the HPA system seems to be much stronger than that of prednisolone in equivalent doses with comparable anti-inflammatory effects. It is also suggested that the alternate-day therapy with such long-acting steroids as betamethasone are useless in preventing HPA suppression.