Response properties of macaque monkey chorda tympani fibers

Many of the chorda tympani fibers of crab-eating monkeys respond to more than one of the four basic stimuli (NaCl, sucrose, HCl, and quinine hydrochloride) as well as cooling or warming of the tongue. Fibers could be classified into four categories depending on their best sensitivity to any one of the four basic stimuli. Sucrose-best and quinine-best fibers are rather specifically sensitive to sucrose and quinine, respectively, while salt-best and acid-best fibers respond relatively well to HCl and NaCl, respectively. Saccharin, dulcin, and Pb acetate produce a good response in sucrose-best fibers, but quinine-best and salt-best fibers also respond to saccharin. Highly significant positive correlations exist between amounts of responses to sucrose and those to saccharin, dulcin, and Pb acetate, indicating that these substances produce in the monkey a taste quality similar to that produced by sucrose. Compared with chroda tympani fibers of rats, hamsters, and squirrel monkeys, macaque monkey taste fibers are more narrowly tuned to one of the four basic taste stimuli and more highly developed in sensitivity to various sweet-tasting substances. Also LiCl and NaCl are more effective stimuli for gustatory receptors in macaque monkeys than NH4Cl and KCl. This contrasts with a higher sensitivity to KCl and NH4Cl than to NaCl in chorda tympani fibers of squirrel monkeys.

Partial purification, properties, and subcellulsr distribution of rat liver phosphatidate phosphatase

Phosphatidate phosphatase (EC 3.1.3.4Y was purified 15- to 20-fold from the soluble fraction of rat liver. The purification procedure involved calcium phosphate gel adsorption and elution, ammonium sulfact precipitation, and molecular-sieve chromatography. For the enzyme assay, and aqueous dispersion of phosphatidate, rather than "membrane-bound" phosphatidate, was used as substrate. The partially purified enzyme depends almost entirely on the presence of Mg2+ for its activity. Morover, the activity of the enzyme is stimulated by phosphatidylcholine. The enzyme exhibits a high substrate specificity for phosphatidate. The apparent Km for phosphatidate is approximately 0.05 mM. The optimum pH is between 7.4 and 7.6. The enzyme is inhibited by fluoride and by p-chloromercuribenzoate. The subcellular distribution of phosphatidate phosphatase in rat liver was studied by assaying the activity of the enzyme in the presence of Mg2+ and phosphatidylcholine. In contrast ot the results of previous studies, most of the enzyme activity was found in the soluble fraction.

Conformation of high-molecular-weight poly(L-valine) in solid state

Poly(L-valine) in various degrees of polymerization was prepared from the N-carboxyanhydride of L-valine. The high-molecular-weight polymer was fibrous and capable of forming an oriented film when cast from trifluoroacetic acid solution. The comformations were examined by Raman spectroscopy. The Raman and infrared spectra of high-molecular-weight polymer were quite different from those of low-molecular-weight and tri-fluoroacetic-acid-treated high-molecular-weight polymers. The spectral data in the amide A, I, II, III, and V regions indicated that high-molecular-weight poly(L-valine) is possibly in the alpha-helical conformation, while low-molecular-weight poly(L-valine) and high--molecular-weight poly(L-valine) treated with trifluoroacetic acid are in the beta-conformation.

Separation of 1-acylglycerolphosphate acyltransferase and 1-acylglycerolphosphorylcholine acyltransferase of rat liver microsomes

1-Acylglycerolphosphate acyltransferase (Ec 2.3.1-) and 1-acylglycerolphosphorylcholine acyltransferase (EC 2.3.1.23) of rat liver microsomes were separated from each other. The separation was achieved by sucrose density gradient centrifugation of the enzyme preparation that was obtained by solubilizing microsomes with a nonionic detergent, Triton X-100, and subjecting the solubilized microsomes to molecular-sieve chromatography. The two acyltransferases are distinguishable from each other also with respect to their stabilities to heat and to Triton X-100. Hence, it is concluded that these acyltransferases are distinct enzymes. These results, together with our previous finding that glycerolphosphate acyltransferase is also a separate enzyme, demonstrate the presence of distinct acyltransferases responsible for the acylation of the different acyl acceptors. Furthermore, the acyl-donor specificities of these acyltransferases provide the enzymatic basis for the nonrandom distribution of fatty acids in naturally occurring glycerolipids.

Quantitative analysis of radioisotopic angiography in trophoblastic neoplasia

The diagnostic significance of radioisotopic angiography in the clinical management of trophoblastic neoplasia was studied by analyzing the patterns of radioisotope (RI)-dynamic curve obtained by processing sequential image with a computer, and an attempt was made to express numerically the size of tumors present in vivo. It was demonstrated that the total activities of RI in the abnormal phase of RI-dynamic curves in trophoblastic neoplasia were closely correlated with the sizes of the intrauterine tumors actually resected.