Neural coding of speech sound in the telencephalic auditory area of the mynah bird

Summary The responses of neurons in field L in the auditory neostriatum of the mynah bird, Gracula religiosa, were recorded during presentation of intact or manipulated mimic voices. A typical mimic voice konnichiwa elicited responses in most of the neurons. Neurons in the input layer (L2) of field L showed many peaks on peristimulus time histograms while those in other layers (L1 and L3) exhibited only one or two peaks. Several neurons in L1 and L3 responded only to the affricative consonant /t/ in the intact mimic voices. They did not respond to the affricative consonant in the isolated segment or to the one in the playbacked voice in reverse. Forty-five percent of the neurons (33/ 73) decreased in firing rates at the affricative consonant in the isolated segment compared with in the intact voice. Some of these neurons, in which neither the affricative consonant in the isolated segment nor bursts of noise alone elicited responses, exhibited clear phasic responses to /t/ in the case when bursts of noise with particular central frequencies preceded the affricative consonant. The responsiveness of these neurons appears to receive temporal facilitation. These results suggest that these neurons code the temporal relationship of speech sound.Abbreviations HVc hyperstriatum ventrale, pars caudale - TFN temporally facilitated neuron - TSN temporally suppressed neuron     

Differences in the release of cholesterol from taurocholate versus taurochenodeoxycholate micellar solutions

The maximal micellar solubility, distribution and apparent monomer activity of cholesterol in taurine-conjugated cholate and chenodeoxycholate micellar solutions were studied to clarify the different modulating effect of these bile salt species on cholesterol uptake in an intestinal lumen. The maximal micellar solubility was significantly greater in taurochenodeoxycholate. The intermicellar cholesterol monomer concentration was not significantly different between the two kinds of micellar solution. However, the apparent cholesterol monomer activity determined using an artificial organic phase (polyethylene disc) was significantly higher in taurocholate than that in taurochenodeoxycholate. A linear relationship between the intermicellar cholesterol concentration and the apparent cholesterol monomer activity was found, with the slope depending upon the bile salt species. It is concluded that the difference in partitioning of cholesterol from taurocholate and taurochenodeoxycholate micelles into a fixed organic phase may contribute in part to the different regulating effects of these bile salts on the uptake of cholesterol in the intraluminal phase.     

Fast and easy detection of mouse sex chimeras using electrophoretic polymorphism of phosphoglycerate kinase-1, an X chromosome-linked enzyme

About half of the chimeras produced by aggregation of two mouse embryos are sex chimeras composed of both XX and XY cells. We developed a fast and easy method to identify sex chimeras by using electrophoretic bimorphism of an X-linked enzyme, phosphoglycerate kinase-1 (PGK-1), as a marker. When embryos resulting from the crossing of a Pgk-1b/Pgk-1b female and a Pgk-1a/Y male are aggregated, the genotype of sex chimeras is Pgk-1b/Pgk-1a----Pgk-1b/Y. Most of these were identifiable from the PGK-1 electrophoretic pattern of blood cells (i.e., AB type) and the appearance of genitalia (male type or apparently abnormal). Genotypes of functional sperm in the testes of the male-type sex chimeras were also identifiable from the PGK-1 electrophoretic pattern of progenies. Examination of gonads of the sex chimeras revealed that a considerable proportion was hermaphorditic. With this method, reasonable numbers of male-type sex chimeras and hermaphrodites may be selected and used as material for investigating sexual differentiation.     

Tissue distribution of rat angiotensinogen mRNA and structural analysis of its heterogeneity

The tissue distribution and the structural heterogeneity of the rat angiotensinogen mRNA have been investigated with the aid of a previously cloned cDNA as well as a genomic DNA for rat angiotensinogen as analytical probes. The angiotensinogen mRNA is expressed not only in the liver but also in various tissues including the brain, kidney, adrenal gland, ovary, and lung. The relative levels of the mRNA in the above tissues have been estimated to be 3-4, 20-30 (for the next three tissues), and around 100 times less than that in the liver, respectively. The mRNAs in both hepatic and extrahepatic tissues are encoded by a single gene in the rat genome. At least four different size classes of the angiotensinogen mRNA that start with a single 5' terminus and differ only in the lengths of their 3'-untranslated regions have been identified, and these multiple mRNA species are most likely generated by using the polyadenylation signals AAUAAA and AUUAAA found 10-30 nucleotides upstream from the four polyadenylation sites. Because the structures of these multiple mRNA species do not vary among the tissues of the liver, brain, and kidney, angiotensinogen synthesized locally is structurally identical to that produced in the liver and may have some biological roles independent of the circulating angiotensinogen, mainly derived from the liver. In addition, the sequence of the 5'-flanking region of the angiotensinogen gene has been determined, and some features common to other steroid hormone-responsive genes have been discussed.     

Estrogen-mediated induction of a vitellogenin-specific nonhistone chromatin protein in the male chicken liver

Summary Non-histone chromatin proteins prepared from the livers of estrogen-treated and nontreated male chickens were compared by reverse-phase high performance liquid chromatography (RP-HPLC), followed by sodium dodecylsulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The results revealed that the hormone-treated male liver chromatin contained a specific protein corresponding to the vitellogenin-specific protein previously purified from the liver of egg-laying hens (Nakayama 1985). The chicken protein, purified further by gel-filtration high performance liquid chromatography (GF-HPLC), showed specific binding activity to DNA fragments carrying a part of the vitellogenin gene. On the basis of similarities in the elution patterns from GF-HPLC and RP-HPLC as well as in the mobility on SDS-PAGE, we concluded that this hormone-induced protein in the male chicken liver was identical to the vitellogenin-specific protein identified in the hen liver, and assumed it to be a specific regulatory protein for the vitellogenin gene expression. The amino acid composition of this chicken protein has been determined.     

Purification of Ribulose 5-phosphate Kinase and Minor Polypeptides of Pyrenoid from the Green Alga Bryopsis maxima

Ribulose 5-phosphate (Ru5P) kinase (ATP:D-ribulose 5-phosphate1-phosphotrans- ferase; EC 2.7.1.19 [EC] ), an enzyme in the reductivepentose phosphate cycle, was purified from the green alga Bryopsismaxima and its activity and peptide composition were studied.The specific activity of purified Ru5P kinase was 20 µmoleRuBP formed (mg protein)^–1 min^–1 corresponding toa 490-fold purification from the supernatant of chloroplasts.The K_m values of Ru5P kinase for ATP and Ru5P were 69 µMand 330 µM, respectively. The molecular size of Ru5P kinase was estimated as 90 kDa bygel filtration and that of its polypeptide as 41 kDa by SDS-polyacrylamidegel electrophoresis. A small portion of the Ru5P kinase wasfound in a large molecular state (500 kDa) which was consideredto be an inactive form of the enzyme. Ru5P kinase activity has been reported in the pyrenoid of Eremosphaeraviridis as well as ribulose 1,5-bisphosphate carboxylase-oxygenase(RuBisCO) and ribose 5-phosphate isomerase activity (Holdsworth1971). In Bryopsis maxima, among the pyrenoid polypeptides otherthan that of RuBisCO, we found a polypeptide of 42 kDa, similarto that of Ru5P kinase in molecular size and ratio to RuBisCO.A peptide map of the 42 kDa pyrenoid polypeptide, however, showedthat it differed from that of Ru5P kinase. In conclusion, Ru5Pkinase may be not involved in the pyrenoid of this alga. (Received January 19, 1985; Accepted May 15, 1985)     

Specificity of hydrogen transfer of mammalian and avian carbonyl and aldehyde reductases

Aldehyde reductases from several mammalian and avian tissues transferred the pro-4R hydrogen of NADPH to the substrate, whereas the stereospecificity of carbonyl reductases was not uniform being correlated with the ability to catalyze the oxidoreduction of hydroxysteroids.     

Molecular cloning and nucleotide sequences of cDNAs specific for rat liver ribosomal proteins S17 and L30

cDNA clones coding for rat liver ribosomal proteins S17 and L30 have been isolated by positive hybridization-translation assay from a cDNA library prepared from 8-9S poly(A)+RNA from free polysomes of regenerating rat liver. The cDNA clone specific for S17 protein (pRS17-2) has a 466-bp insert with the poly(A) tail. The complete amino acid (aa) sequence of S17 protein was deduced from the nucleotide sequence of the cDNA. S17 protein consists of 134 aa residues with an Mr of 15 377. The N-terminal aa sequence of S17 protein determined by automatic Edman degradation is consistent with the sequence data. The aa sequence of S17 shows strong homology (76.9%) to that of yeast ribosomal protein 51 [Teem and Rosbash, Proc. Natl. Acad. Sci. USA 80 (1983) 4403-4407] in the two-thirds N-terminal region. The cDNA clone specific for L30 protein (pRL30) has a 394-bp insert. The aa sequence of L30 protein was deduced from the nucleotide sequence of the cDNA. The protein consists of 114 aa residues with an Mr of 12 652. When compared with the N-terminal aa sequence of rat liver L30 protein [Wool, Annu. Rev. Biochem. 48 (1979) 719-754], pRL30 was found not to contain the initiation codon and 5'-noncoding region. The cDNA showed twelve silent changes in the coding region, one point mutation and one base deletion in the 3'-noncoding region, compared with mouse genomic DNA for L30 protein [Wiedemann and Perry, Mol. Cell Biol. 4 (1984) 2518-2528].     

Purification and characterization of a purple acid phosphatase from rat spleen

An acid phosphatase species which is activated by Fe2+ was purified 3,700-fold from rat spleen by chromatography on columns containing Blue-Sepharose, concanavalin A-Sepharose, Sephadex G-100, and CM-Sephadex. The enzyme hydrolyzed aryl phosphates, nucleoside di- and triphosphates, phosphoproteins, and thiamine pyrophosphate with Km values of 10(-4) to 10(-3) M at an optimal pH of 5.0-5.8. Co-purification of the acid phosphatase and acid phosphoprotein phosphatase indicated that they were identical. The purified enzyme was glycoprotein in nature, showing four heterogeneous forms on acid polyacrylamide gel electrophoresis (pI values, 7.8, 8.0, 8.3, and 8.5), but it gave a molecular weight of 33,000 on sodium dodecyl sulfate-gel electrophoresis and gel permeation chromatography. The enzyme had a purple color (lambda max 545 nm) and contained 2 iron atoms per enzyme molecule. Among reductants, ascorbic acid and Fe2+ were the best activators, although their combined effect was not additive. Fe2+ and ascorbic acid both changed the purple enzyme into the same active form (lambda max 515 nm), giving almost the same kinetic constants for substrates and for inhibitors such as molybdate, phosphate and fluoride. However, low concentrations of Fe2+, from 0.01 mM to 1.0 mM, immediately and reversibly activated the enzyme, whereas high concentrations of ascorbic acid over 1 mM were required for maximal activation, which was slow and irreversible.