Kenkichi Takauchi

Evidence for existence of various homologues and analogues of platelet activating factor in a lipid extract of bovine brain.

Vasodepressor phospholipid with platelet-aggregating activity was highly purified from a lipid extract of bovine brain and subjected to field desorption-mass spectrometry. It was further analyzed by gas-liquid chromatography-mass spectrometry after hydrolysis with phospholipase C and conversion to tert-butyldimethylsilyl derivatives. Results indicated the presence of four species of platelet activating factor (1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine, PAF) and ten acyl analogues of PAF. The acyl analogues of PAF included species having an sn-2-propionyl or sn-2-butyryl group, which have not been previously detected in natural sources. The total amount of acyl analogues of PAF was much higher than that of PAF.

Novel phospholipids with aliphatic dicarboxylic acid residues in a lipid extract from bovine brain

A vasodepressor phospholipid fraction purified from a lipid extract of bovine brain was found to contain novel phospholipids with both a long-chain acyl group and an aliphatic dicarboxylic acid residue. This was shown by analyzing the fraction as tert-butyldimethylsilyl derivatives of glyceride by capillary GC-MS after hydrolysis with phospholipase C. Six molecular species with a palmitoyl group and an aliphatic dicarboxylate (chain length C4-C9), and two species with both a stearoyl group and a succinate or glutarate residue were detected.

A platelet‐aggregating and hypotensive phospholipid isolated from bovine brain

A phospholipid that differs from known active lipids and causes potent platelet aggregation and weak hypotension has been isolated from bovine brain. Its platelet aggregating effect on heparinized platelet‐rich plasma from rabbits, was at a threshold concentration of about 0.2 nmol ml−1 as phosphorus. The effect was inhibited by CV‐3988. The phospholipid was converted by diazomethane treatment to another active lipid that caused short‐term hypotension, but not platelet aggregation, rather it inhibited the aggregation of rabbit heparinized platelets induced by platelet‐activating factor.

Theoretical analysis of a site-specific chemiluminescence reaction and its application to quantitation of lipid hydroperoxides

A system was designed for chemiluminescent measurement of lipid hydroperoxides by their site-specific reaction in sodium dodecylsulfate micelles. Ferrous ion-induced decomposition of lipid hydroperoxides in the sodium dodecylsulfate micelles resulted in strong chemiluminescence of the Cypridina luciferin analog, 2-methyl-6-phenyl-3,7-dihydroimidazo[1,2-alpha]pyrazin-3-one (CLA). After addition of ferrous sulfate to the micelles containing lipid hydroperoxide and luciferin, the chemiluminescence intensity reached a maximum rapidly and then decreased. The sequence of this reaction was elucidated by theoretical analysis, which demonstrated that the maximum chemiluminescence intensity is proportional to the initial concentration of hydroperoxide. Good linear relationships were observed between the maximum counts of chemiluminescence and the amounts of hydroperoxides of linoleic acid, phosphatidylcholine, choresterol (5 alpha), cumene and tert-butyl and hydrogen peroxide. This chemiluminescence method was simple and sensitive enough to detect picomole levels of linoleic acid and phosphatidylcholine hydroperoxides.

Isolation of Diosgenin[(25R)‐Spirost‐5‐en‐3β‐o1] from a Lysate of a New Hypotensive Phospholipid Occurring in Bovine Brain

Abstract: Diosgenin[(25R)‐spirost‐5‐en‐3β‐o1] and cholesterol were detected as trimethylsilyl derivatives by gas chromatography‐mass spectrometry in an alkaline lysate of a new hypotensive phospholipid from the lipid fraction of bovine brain. These steroids seemed to be present in the hypotensive phospholipid fraction in some bound forms.

A hypotensive phospholipid from dog peritoneal dialysate.

The hypotensive effects of lysophosphatidylethanolamines have been reported (Turcotte et al 1973, 1975; Antonello et al 1973). Recently, we have described the vaso-activity of L-a-lysophosphatidic acid (l-acylsn-glycero-3-phosphate) (Tokumura et al 1978 a,b,c), and the occurrence of an acute depressor-active factor in the acetone-soluble fraction of bovine brain (Tsukatani et al 1976). We now report the pharmacological and chemical characteristics of a short-lasting hypotensive phospholipid obtained from dog peritoneal dialysate (PD) designated tentatively PD.D-I. Preparation of the hypotensive phospholipid PD.D-I. Dog PD (Martini et al 1967) was lyophilized, extracted with chloroform-methanol @:I, v/v), washed by Folch’s procedure (Folch et al 1957) and the total lipid fraction was obtained (approximately 300 mg litre-’ of PD). The lipids were fractionated on a silicic acid column eluted with chloroform-methanol mixtures of increasing polarity, and the phosphorus content in each fraction was determined (Chalvardjian & Rudnicki 1970). The hypotensive effect of each fraction on carotid arterial blood pressure of the urethane (1.8 g kg-l i.p.)-anaesthetized rat was evaluated by intrafemoralvenous injection of a sample of the eluate after it had been dried and redissolved in 0.9% w/v NaCI. The activity was recovered mainly in the eluate of the chloroform-methano1 (4:6, v/v). The active material was further purified through cellulose, first on Sephadex LH-20 [eluting with chloroform-methanol (1 : I , v/v)J and second on Sephadex LH-20 [eluting with acetoneethanol (1 :1, v/v)] columns and the hypotensive activities and phosphorus contents of fractions were evaluated as described above. Finally, 1.94mg of purified hypotensive factor litre-’ of PD was obtained which corresponded to approximately 0.65% of the total lipid of dog PD; it contained 92pg of phosphorus. The purified material showed a single spot on t.1.c. in three different solvent systems (Table 1). Pharmacological properties of PD.D-I. The doseresponse relationship (Fig. 1) was examined on urethane-anaesthetized rats. In the range tested the depressor-response was dosedependent and no tachyphylaxis or sensitization was observed. The minimum effective dose of PD.D-I was approximately 35.2pg kg-’ of the purified preparation on a weight basis and it contained approximately 0.054 pmol phosphate. PD.D-I elicited depressor responses in all species examined approximately to the same extent, but we observed two types of profiles of duration of responses. In rats and cats the arterial blood pressure fell sharply and returned to preinjection