Average phase difference theory and 1∶1 phase entrainment in interlimb coordination

The dynamics of coupled biological oscillators can be modeled by averaging the effects of coupling over each oscillatory cycle so that the coupling depends on the phase difference between the two oscillators and not on their specific states. Average phase difference theory claims that mode locking phenomena can be predicted by the average effects of the coupling influences. As a starting point for both empirical and theoretical investigations, Rand et al. (1988) have proposed d/dt= — K sin ), with phase-locked solutions =arcsin( /K), where is the difference between the uncoupled frequencies and K is the coupling strength. Phase-locking was evaluated in three experiments using an interlimb coordination paradigm in which a person oscillates hand-held pendulums. was controlled through length differences in the left and right pendulums. The coupled frequency _c was varied by a metronome, and scaled to the eigenfrequency _v of the coupled system K was assumed to vary inversely with _c. The results indicate that: (1) and K contribute multiplicatively to (2) =0 or = regardless of K when =0; (3) 0 or regardless of when K is large (relative to ); (4) results (1) to (3) hold identically for both in phase and antiphase coordination. The results also indicate that the relevant frequency is _c/_v rather than _c. Discussion high-lighted the significance of confirming =arcsin(/K) for more general treatments of phase-locking, such as circle map dynamics, and for the 11 phase-entrainment which characterizes biological movement systems.     

Isolation and characterization of an ω3-desaturation-defective mutant of an arachidonic acid-producing fungus,Mortierella alpina 1S-4

A mutant considered to be defective in the conversion of n-6 to n-3 fatty acids (3-desaturation) was derived from a 5-desaturation-defective mutant (Mut44) of Mortierella alpina 1S-4, after treating its spores with N-methyl-N-nitro-N-nitrosoguanidine. This mutant cannot produce 8(Z),11(Z),14(Z),17(Z)-eicosatetraenoic acid or any other n-3 fatty acids, of which about 10% was found in its parental strain upon cultivation at 12°C. The mutant's growth rate was comparable to that of the parental strain when grown at 28°C, but it became much slower when the mutant grew at 12°C, at which the lag phase for Mut44 was about 2 d but 5 d for the mutant.Abbreviations 18:33 9(Z),12(Z),15(Z)-octadecatrienoic acid - 18:43 6(Z),9(Z),12(Z),15(Z)-octadecatetraenoic acid - 20:43 8(Z),11(Z),14(Z),17(Z)-eicosatetraenoic acid - AA arachidonic acid - DHGA dihomo--linolenic acid - EPA 5(Z),8(Z),11(Z),14(Z),17(Z)-eicosapentaenoic acid - GLC gas-liquid chromatography - MNNG N-methyl-N-nitro-N-nitrosoguanidine - PC phosphatidylcholine     

A neural net capable of competitive and cooperative computation

An algorithm of learning in multilayer threshold nets without feedbacks is proposed. The net is. built of threshold elements with binary inputs. During a learning process each input vector x is accompanied by a teacher's decision ({1,...,M}). The pairs (x[n], [n]) appear in successive steps independently according to some unknown stationary distribution p(x,). The problem of learning of a threshold net has been decomposed to a series of problems of learning of the threshold elements. The proposed learning algorithm of the threshold elements has a perceptron-like form. It was proven that a decision rule of the threshold net stabilizes after a finite number of steps. For definite classes {p(x, )} _* ^K of distributions p(x,), an optimal decision rule stabilizes after a finite number of steps. These classes {p(x, )} _* ^K also contain distributions describing learning processes with perturbations.     

A frequency-time domain 3D COSY-J technique for measurement of1H−31P coupling constants in oligonucleotides

Summary A frequency-time domain 3D NMR technique has been developed for measurement of heteronuclear coupling constants in oligonucleotides employing a combination of COSY andJ-resolved techniques. The method employs frequency-selective excitation to generate the ₁ axis and 2D FT to generate the ₂ and ₃ axes. The procedure yields high resolution, especially along the ₁ axis. The technique is demonstrated on a dinucleotide.     

Restriction fragment analysis of the secalin loci of rye

Analyses of wheat/rye addition lines by Southern blotting confirmed the presence of sequences related to theSec 1, Sec 2, andSec 3 loci on chromosomes 1R and 2R. Comparison of the 1R and 2R addition lines allowed the identification of -secalin genes atSec 1 andSec 2, respectively, while -secalin and -secalin genes atSec 1 were discriminated by comparative hybridization with three probes: -secalin, total -secalin, and 3 -secalin. The high molecular weight (HMW) secalin genes atSec 3 were identified using a homologous HMW subunit probe from wheat. Gene copy numbers were estimated as about 40–60 for -secalins, 5–10 for -secalins, and 2 for HMW secalins. Comparison of individual plants of cv. Gazelle showed a high degree of polymorphism, particularly for sequences related to -secalins and HMW secalins.     

Role of ω-3 fatty acid desaturases in the regulation of the level of trienoic fatty acids during leaf cell maturation

Trienoic fatty acids, namely -linolenic acid and hexadecatrienoic acid, present in leaf lipids are produced by -3 fatty acid desaturases located in the endoplasmic reticulum and plastid membranes. The changes in the level of trienoic fatty acids during leaf maturation were investigated in wild-type plants of Arabidopsis thaliana (L.) Heynh. and in the fad7 mutant deficient in the activity of a plastid -3 desaturase. The levels of trienoic fatty acids increased in 26 °C- and 15 °C-grown wild-type plants with maturation of leaves. The increase in trienoic fatty acids was mainly due to galactolipids enriched in plastid membranes. In addition, the relative levels of trienoic fatty acids in major glycerolipids, including phospholipids enriched in the endoplasmic reticulum membranes, also increased with leaf maturation. By contrast, when the fad7 mutant was grown at 26 °C, the relative levels of trienoic fatty acids in individual lipids decreased with leaf maturation. The decreases in the levels of trienoic fatty acids, however, were alleviated when the fad7 mutant was grown at 15 °C. These results suggest that the plastid -3 desaturase plays a major role in increasing the levels of trienoic fatty acids with leaf maturation.Abbreviations 163 hexadecatrienoic acid - 183 -linolenic acid - DGD digalactosyldiacylglycerol - MGD monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - TA trienoic fatty acid - WT wild type - -3 refers to the position of the double bond from the methyl end of a fatty acid This research was supported in part by Grants-in-Aid for Scientific research (#07251214 and #06804050 to K.I.) from the Ministry of Education, Science and Culture, Japan, and by the research grant from Shorai Foundation.     

Biogenesis of mitochondria. 52

Summary The characteristics of recombination of several petite (rho ^-) mutants of S. cerevisiae that retain the -influenced region of the mitochondrial genome, identified by the markers cap1-r, ery1-r and tsr1, are described. The petites were derived from an ^– grande (rho ⁺) strain and those petites which retain all three markers show recombination properties similar to those of the ^- parental strain. However, other rho ^- mutants that retain the cap1 and ery1 loci but have lost the tsr1 locus, which is located between cap1 and ery1, show markedly different properties of mitochondrial transmission and recombination, consistent with the presence of ⁺ alleles. The association of an internal deletion between the cap1 and ery1 loci with a change in phenotype provides additional evidence for the location of between these two loci.Although the petites deleted for the tsr1 locus exhibited the recombination properties of ⁺ strains, it was not possible to transmit this characteristic to rho ⁺ recombinant cells. Experiments on the kinetics of elimination by ethidium bromide of the cap1 and eryl markers from the petites and measurements of the buoyant densities of their mtDNA species did not indicate major changes (such as selective sequence repetition) in the sequences of the mtDNAs. The possible nature of the changes in the mtDNAs of these petites is discussed in light of recent studies on the physical nature of the alleles.     

Fatty acid content in wild type and WZSL mutant of Euglena gracilis

The effects of growth conditions on fatty acid profilewere examined in the photosynthetic wild type and inthe spontaneous non-photosynthetic WZSL mutant of theunicellular flagellate Euglena gracilis. Inthe light, the amount of polyunsaturated fatty acids(PUFAs) is higher in the wild type than in the mutant,independent of the carbon source. Among importantPUFAs, linolenic acid (18:3 3) is present inhigh amount only in wild type cells grown in the lightwith any of the tested carbon sources. The content ofother PUFAs, such as arachidonic acid (20:46), EPA (20:5 3) and DHA (22:63), is not correlated with the presence oflight or chloroplasts.The main effect of the dark in both strains is tolower the content of PUFAs and mono-unsaturated fattyacids and to increase the content of saturated fattyacids with all the carbon sources.     

A novel fungal ω3-desaturase with wide substrate specificity from arachidonic acid-producing Mortierella alpina 1S-4

A filamentous fungus, Mortierella alpina 1S-4, is capable of producing not only arachidonic acid (AA; 20:4n-6) but also eicosapentaenoic acid (EPA; 20:5n-3) below a cultural temperature of 20°C. Here, we describe the isolation and characterization of a gene (maw3) that encodes a novel 3-desaturase from M. alpina 1S-4. Based on the conserved sequence information for M. alpina 1S-4 12-desaturase and Saccharomyces kluyveri 3-desaturase, the 3-desaturase gene from M. alpina 1S-4 was cloned. Homology analysis of protein databases revealed that the amino acid sequence showed 51% identity, at the highest, with M. alpina 1S-4 12-desaturase, whereas it exhibited 36% identity with Sac. kluyveri 3-desaturase. The cloned cDNA was confirmed to encode the 3-desaturase by its expression in the yeast Sac. cerevisiae. Analysis of the fatty acid composition of the yeast transformant demonstrated that 18-carbon and 20-carbon n-3 polyunsaturated fatty acids (PUFAs) were accumulated through conversion of exogenous 18-carbon and 20-carbon n-6 PUFAs. The substrate specificity of the M. alpina 1S-4 3-desaturase differs from those of the known fungal 3-desaturases from Sac. kluyveri and Saprolegnia diclina. Plant, cyanobacterial and Sac. kluyveri 3-desaturases desaturate 18-carbon n-6 PUFAs, Spr. diclina 3-desaturase desaturates 20-carbon n-6 PUFAs and Caenorhabditis elegans 3-desaturase prefers 18-carbon n-6 PUFAs as substrates rather than 20-carbon n-6 PUFAs. The substrate specificity of M. alpina 1S-4 3-desaturase is rather similar to that of C. elegans 3-desaturase, but the M. alpina 3-desaturase can more effectively convert AA into EPA when expressed in yeast. The M. alpina 1S-4 3-desaturase is the first known fungal desaturase that uses both 18-carbon and 20-carbon n-6 PUFAs as substrates.     

Formation ofα,ω-dodecanedioic acid andα,ω-tridecanedioic acid from different substrates by immobilized cells of a mutant ofCandida tropicalis

Summary The metabolic formation of either,-dodecanedioic acid or,-tridecanedioic acid from the individual n-alkane, n-alcohol, n-monoacid and,-diol with corresponding carbon chain length using K-carrageenan entrapped mutants S76 ofCandida tropicalis was studied. The immobilized cells of S76 could also directly produce-hydroxy acid and,-dioic acid from,-diol. With n-alcohol and n-monoacid as substrate, the amount of-hydroxy acid and,-dioic acid produced was also a function of the incubation time.The results demonstrated that in the immobilized cells of S76 the formation of,-dioic acid from n-alcohol can also run both via n-monoacid and via,-diol as well as in the normal cells of S76.     

A new metabolic pathway from n-dodecane to α, ω-dodecanedioic acid in a mutant of Candida tropicalis

Summary The metabolic formation of ,-dodecanedioic acid via ,-dodecanediol from n-dodecane using a mutant S76 of Candida tropicalis was studied.It was found that resting cells of S76 produce ,-dodecanediol from n-dodecane. This intermediate was identified by different analytical methods. With n-dodecanol as substrate the quantitative changes in the concentrations of ,-dodecanediol as well as other intermediates, e.g. monoacid, -hydroxy acid and ,-dioic acid produced by resting cells of S76 for different periods of time were determined. With ,-dodecanediol as the sole carbon source, quantitative changes of -hydroxy acid and ,-dioic acid produced by S76 were also recorded.The results confirm the existence of a new metabolic pathway via ,-diol in the course of ,-dioic acid formation from n-alkane in the mutant S76 of C. tropicalis.     

Similarities of omega gliadins from<Emphasis Type="Italic"> Triticum urartu</Emphasis> to those encoded on chromosome 1A of hexaploid wheat and evidence for their post-translational processing

The -gliadins encoded on chromosome 1 of the A genome were purified from Triticum aestivum L. (2n=6x=42, AABBDD) cv. Butte86, nullisomic 1D-tetrasomic 1A of cv. Chinese Spring (CS N1DT1A), and the diploid T. urartu (2n=2x=14, AA). Reverse-phase high-performance liquid chromatography combined with sodium dodecyl sulfate-polyacrylamide gel electrophoresis of gliadin extracts from CS nullisomic-tetrasomic (NT) lines confirmed the assignment to chromosome 1A. The purified -gliadins were characterized by mass spectrometry and N-terminal sequencing. The 1A-encoded -gliadins were smaller than 1B- or 1D-encoded -gliadins. The N-terminal amino acid sequences for 1A -gliadin mature peptides were nearly identical to those for the T. urartu -gliadins and were more similar to 1D -gliadin sequences than to sequences for T. monococum -gliadins, barley C-hordeins, or rye -secalins. They diverged greatly from the N-terminal sequences for the 1B -gliadins. The data suggest that T. urartu is the A-genome donor, and that post-translational cleavage by an asparaginyl endoprotease produces those -gliadins with N-terminal sequences beginning with KEL.Communicated by J. Dvorak     

Degradation pathways from n-tridecane to α, ω-tridecanedioic acid in a mutant of Candida tropicalis

Summary The metabolic formation of ,-tridecanedioic acid via n-tridecanoic acid and via ,-tridecanediol from n-tridecane in the mutant S 76 of Candida tropicalis was studied. It was found that resting cells of S 76 produced ,-tridecanediol from n-tridecane.With n-tridecanol as substrate, the ,-diol could also be detected. The mutant S 76 was able to produce ,-tridecanedioic acid using either n-tridecanol or n-tridecanoic acid as the sole carbon source. Quantitative changes in the concentration of -hydroxy tridecanoic acid and other intermediates were recorded during the formation of ,-dioic acid.The results confirm the existence of two metabolic pathways mentioned above in the course of ,-dioic acid formation from odd n-alkane in the mutant S 76 of C. tropicalis.     

Purification and characterization of hydroxycinnamoyl-coenzyme A: ω-hydroxypalmitic acid O-hydroxycinnamoyltransferase from tobacco (Nicotiana tabacum L.) cell-suspension cultures

An acyltransferase hydroxycinnamoyl-Coenzyme A: -hydroxypalmitic acid O-hydroxycinnamoyltransferase (HHT; EC 2.3.1.-), which transfers hydroxycinnamic acids from hydroxycinnamoyl-CoA thioesters to several hydroxylated fatty acid derivatives, was characterized from tobacco (Nicotiana tabacum L. cv. Xanthi nc) cell-suspension cultures. It exhibited the same properties as the enzyme previously detected in wound-healing potato tuber discs (Lotfy et al., 1994, Phytochemistry 35: 1419–1424), and especially a marked specificity for -hydroxypalmitic acid and feruloyl-CoA. It was purified 300-fold to near homogeneity from late logarithmic-phase cell suspensions. The apparent molecular mass of the native protein was 55 kDa and its isoelectric point, estimated by electrofocusing, was 4.6. The purified enzyme conjugated ferulic acid to -hydroxypalmitic acid and to 1-tetradecanol, its main lipidic substrates, suggesting that the same enzyme probably synthesizes the different esters of 1-alkanols and of -hydroxy fatty acids which are formed in vitro.Abbreviations ABA abscisic acid - IEF isoelectric focusing - HHT hydroxycinnamoyl-Coenzyme A: -hydroxypalmitic acid O-hydroxycinnamoyltransferase - pI isoelectric point     

Cultivation of the agarophyte Gelidium pristoides in Algoa Bay,South Africa

Biofilms were allowed to develop on wooden slides of the River Red Gum (Eucalyptus camaldulensis Dehnh., Myrtaceae) submerged in two billabongs of south-eastern Australia. The slides were placed in the photic zone and the aphotic zone, and the biofilms sampled after eight week's growth over the summer of 1989–1990 and winter of 1990. Bacterial numbers, estimated with epifluorescence microscopy, ranged from 4–78 × 10⁶ cells cm^–2. Bacteria were more abundant in the photic zone than the aphotic zone, and more abundant in summer than winter. Fewer than 0.5% of the bacteria could be cultivated on nutrient agar plates. Concentrations of phospholipids ranged from 8–79 ng cm^–2, which corresponded to bacterial abundances of 2–17 × 10⁶ cells cm^–2. Fifty five phospholipid fatty acids (PLFA) were identified, of which 16:0 (13–29% of total PFLA) was the most common. Other abundant PFLA included 16:17c (6–28%), 18:26 (3–16%), 18:33 (4–12%), 18:19c (3–5%), 18:l7c (5–11%) and 18:0 (2–8%). Minor PLFA included 14:0, i and a 15:0, 15:0, 16:l5c, 16:113c, 18:36, 18:43, 20:46 and 20:53. The PLFA profiles of the biofilms were quite different from those of the sediments and plankton. There was a clear distinction between the PLFA profiles of summer and winter biofilms, but less evidence for unequivocal site or light-regime effects.     

Characterization of<Emphasis Type="Italic"> Pseudomonas</Emphasis> sp. HK-6 cells responding to explosive RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine)

The cellular responses of Pseudomonas sp. HK-6 to explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) have been extensively analyzed in this study. The stress shock proteins, which might contribute to enhancing the cellular resistance to the cytotoxic effect of RDX, were induced at different concentrations of RDX used as a substrate for cell culture of Pseudomonas sp. HK-6. The proteins were identified as 70-kDa DnaK and 60-kDa GroEL by SDS-PAGE and Western blot using the anti-DnaK and anti-GroEL monoclonal antibodies. The stress shock proteins induced by RDX were found to increase in proportion to the RDX concentration used for this work. Analysis of membrane fatty acids of strain HK-6 following exposure to RDX showed that the amounts of dominant lipids 16:1 7c/15:0 iso 2OH, 16:0 and 18:1 7c/9t/12t decreased substantially or were not detected in the cells exposed to RDX, while amounts of lipids 10:0 iso, 14:1 5c/5t and 16:10 methyl increased dramatically. Scanning electron microcopy analyses revealed the presence of perforations and irregular rod shapes with wrinkled surfaces for cells treated with 0.135 mM RDX for 12 h, suggesting that RDX has a substantial cytotoxic impact on cells of strain HK-6.     

Metabolic formation of dodecanedioic acid from n-dodecane by a mutant of Candida tropicalis

Summary These experiments studied the metabolic formation of a,-dodecanedioic acid using the mutant S 76 developed from the wild strain Candida tropicalis 1230 (capable of producing large amounts of a,-dodecanedioic acid).Our results show for the first time that 12-hydroxydodecanoic acid was excreted into the medium as a free acid.n-Dodecanol and n-dodecanoic acid were also detected in the n-dodecane medium. The mutant S 76 was able to produce a,-dodecanedioic acid using either n-dodecanol or dodecanoic acid as the sole carbon source. Quantitative cahnges in the concentrations of 12-hydroxy-dodecanoic acid and other intermediates were recorded during the formation of a,-dodecanedioic acid. S 76 was rapidly able to convert large amounts of 12-hydroxy-dodecanoic acid to a,-dodecanedioic acid.The formation of a,-dodecanedioic acid from n-dodecane via the sequence n-dodecanoln-dodecanoic acid 12-hydroxy-dodecanoic acid was confirmed.     

Characteristics of specific125I-ω-conotoxin GVIA binding in rat whole brain

Characteristics of specific¹²⁵I-omega-conotoxin (-CgTX) binding were systematically investigated in crude membranes from rat whole brain. Kd and Bmax Values for the binding were 49.7 pM and 181.5 fmol/mg of protein, respectively. The effects of various types of Ca channel antagonists on the binding were investigated. Dynorphin A (1–13), in particular, specifically inhibited¹²⁵I--CgTX binding, but not that of [³H](+)PN200-110. Spider venom fromPlectreurys tristes did not specifically inhibit specific binding of¹²⁵I--CgTX, because the venom also inhibited the binding of [³H](+)PN200-110 to a similar degree. The amount of specific binding of¹²⁵I--CgTX was less in the cerebellum than that in any other area of whole brain. The cross-linker disuccinimidyl suberate did not label with¹²⁵I--CgTX and its binding sites in rat whole brain, although it did in chick whole brain, which was used as a positive control. These findings suggested that dynorphine A (1–13) was a selective blocker of -CgTX-sensitive Ca channels in crude membranes from rat whole brain and that -CgTX-sensitive Ca channels were mainly present a rat brain except cerebellum.     

Structure and nonlinear optical properties of copper phthalocyanine thin films

This paper describes a joint study of the structure and nonlinear optical properties of vacuum evaporated thin films of copper phthalocyanine (CuPc for brevity). Film thickness ranges from 50 to 500 nm. The anisotropic paramagnetic resonance of Cu⁺⁺ ions reveals that the Pc rings lie almost parallel to the substrate plane with however a large angular distribution (30° FWHM). Third harmonic optical generation measurements performed at 1.064 m and 1.907 m fundamental wavelengths give respectively an average value of the cubic susceptibility ⁽³⁾(-3,)=(4±0.4)·10^–12 e.s.u. and (2.1+-0.2) · 10^-12 These values, although significantly higher than for a common ionic crystal, are about one order of magnitude lower than in conjugated 1-D systems, which shows that the 2-D -electron delocalization is less profitable than the 1-D one. Besides third harmonic, we have also observed second harmonic generation. Its polarization dependence is characteristic of a quadratic susceptibility enhanced in one direction, almost perpendicular to the substrate, withd _eff comprised between 30 and 60 · 10^-9 e.s.u. The possible origins ofd _eff are discussed.     

Inserted sequence in the mitochondrial 23S ribosomal RNA gene of the yeast Saccharomyces cerevisiae.

Summary The sequence organization of the yeast mit-DNA region carrying the large ribosomal RNA gene and the polar locus was examined. Hybridization studies using rho^- deletion mutants and electron microscopy of the heteroduplexes formed between 23S rRNA and the appropriate restriction fragments, lead to the conclusion that the 23S rRNA¹ gene of the ⁺ strains is split by an insertion sequence of 1,000–1,100 bp. In contrast, no detactable insertion was found in the 23S rRNA gene of the ^- strains. The size and the location of the insert found in the 23S rRNA gene of the ⁺ strains appear to be identical to those of the sequence which had previously been found to characterize the difference (at the locus) between the mitDNA of the wild type strains carrying the ⁺ or ^- alleles (Jacq et al., 1977).