Increased yield of fructose from glucose employing thermophilic xylose isomerase in water-ethanol mixtures

Summary The isomerization of D-glucose in mixed ethanol-water was studied at various reaction temperatures (40–70 °C), employing glucose isomerase fromStreptomyces phaeochromogenes andClostridium thermohydrosulfuricum, respectively. The thermophilicClostridium enzyme was considerably, more stable towards the combination of organic cosolvent and increased temperature and with this enzyme a 55% yield of fructose from glucose was obtained at relatively low concentration of ethanol (40 %).     

A comparison of net and gross rates of oxygen production as a function of light intensity in some natural plankton populations and in a Synechococcus culture

In vitrorates of gross and net oxygen production were measuredas a function of light intensity in some plankton communitiescollected from Bedford Basin, Nova Scotia, and in a monoclonalculture of Synechococcus. The rate of gross oxygen productionwas measured by a technique in which the stable oxygen isotope,¹⁸O, serves as a photosynthetic tracer Net oxygen productionwas measured by automated Winkler technique. The rate of communityrespiration in the light was then determined by the differencebetween gross and net rates of oxygen production. In the naturalpopulations examined, neither gross nor net oxygen productionrates were significantly inhibited at the highest light intensitymeasured (500–800 µE m^–2 s^–1) In a samplein which the dark respiration rate was small relative to themaximal rate of production [P_max;sensu Platt et al (1980) JMar. Res., 38, 687–701] the rates of ‘light’respiration were 3 times greater. In two other communities,with high rates of dark respiration relative to P_maxthe ratesof ‘light’ respiration were closer to rates of darkrespiration. In the Synechococcus clone, both gross and netoxygen production rates were inhibited at high light intensities.Rates of ‘light’ respiration were found to varyas a function of light intensity. The greatest rates of respirationwere measured in samples incubated at light intensities thatwere just saturating (100 µE m^–2 s^–1). Therates of ¹⁴C production were also measured as a function oflight intensity The photosynthetic quotients, based on ¹⁴C productionrates and gross oxygen production rates, average 1 9     

Structural features of the plastid ribosomal RNA operons of two red algae: Antithamnion sp. and Cyanidium caldarium

The nucleotide sequences of the plastid 16S rDNA of the multicellular red alga Antithamnion sp. and the 16S rDNA/23S rDNA intergenic spacers of the plastid DNAs of the unicellular red alga Cyanidium caldarium and of Antithamnion sp. were determined. Sequence comparisons support the idea of a polyphyletic origin of the red algal and the higher-plant chloroplasts. Both spacer regions include the unsplit tRNA^Ile (GAU) and tRNA^Ala (UGC) genes and so the plastids of both algae form a homogeneous group with those of chromophytic algae and Cyanophora paradoxa characterized by small-sized rDNA spacers in contrast to green algae and higher plants. Nevertheless, remarkable sequence differences within the rRNA and the tRNA genes give the plastids of Cyanidium caldarium a rather isolated position.     

Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products.

Mutations in genes of the Polycomb (Pc) group cause abnormal segmental development due to ectopic expression of the homeotic products of the Antennapedia and bithorax complexes. Here the requirements for Pc group genes in controlling the abdA and AbdB products of the bithorax complex are described. Embryos containing mutations in the genes Polycomb (Pc), extra sex combs (esc), Enhancer of zeste [E(z)], polyhomeotic (ph), Sex comb on midleg (Scm), Polycomb-like (Pcl), Sex comb extra (Sce), Additional sex combs (Asx), Posterior sex combs (Psc) and pleiohomeotic (pho) were examined. In every case, both abdA and AbdB are expressed outside of their normal domains along the anterior-posterior (A-P) axis, consistent with these Pc group products acting in a single pathway or molecular complex. The earliest detectable ectopic expression is highest in the parasegments immediately adjacent to the normal expression boundary. Surprisingly, in the most severe Pc group mutants, the earliest ectopic AbdB is distributed in a pair-rule pattern. At all stages, ectopic abdA in the epidermis is highest along the anterior edges of the parasegments, in a pattern that mimics the normal abdA cell-specific pattern. These examples of highly patterned mis-expression show that Pc group mutations do not cause indiscriminate activation of homeotic products. We suggest that the ectopic expression patterns result from factors that normally activate abdA and AbdB only in certain parasegments, but that in Pc group mutants these factors gain access to regulatory DNA in all parasegments.     

Caste-specific modulation of juvenile hormone III content and ecdysteroid titer in postembryonic development of the stingless bee,Scaptotrigona postica depilis

Summary Juvenile hormone III content and ecdysteroid titer were analyzed for larval and pupal development of the stingless bee,Scaptotrigona postica depilis. Castespecific differences in juvenile hormone III content were detected at three developmental phases: at the transition from the fourth to the fifth larval stadium, in the spinning phase of the fifth larval stadium, and shortly after the imaginal moult. During the fifth larval stadium, juvenile hormone content closely reflects corpora allata activity. Juvenile hormone synthesis may thus be responsible for the elevated hormone titer in spinning-phase queen larvae, a phase of known sensitivity for induction of queen characters by exogenous juvenile hormone. For ecdysteroids, two phases of caste-specific differences were found: in the pre-pupal phase, and shortly after the imaginal moult. In both periods the titer in queens is distinctly higher compared to workers.Abbreviations Im imago 1 day after eclosion - L3, L4, L5 larval instars 3, 4, and 5 - L5F1, L5F2 substages of feeding phase in fifth larval instar - L5S1, L5S2, L5S3 substages of spinning phase in fifth larval instar - PP1, PP2 substages of prepupal phase - Pw white eyed pupa - Pp pink eyed pupa - Pr red eyed pupa - Pd dark eyed pupa - Pdl, Pdm, Pdd dark eyed pupa with progressive tanning of cuticle - RIA radioimmunoassay     

Structure-activity relationships of cyclic β-casomorphin-5 analogues

Cyclic analogues of the β-casein-derived opioid peptide β-casomorphin-5 (H-Tyr-Pro-Phe-Pro-Gly-OH) were prepared through substitution of the Pro² residue with various ,ω-diamino acid residues (lysine, ornithine, 2,4-diaminobutyric acid) and cyclization of the ω-amino group to the C-terminal carboxyl function. Compounds of this type, with D-configuration at the 2-position residue, showed high opioid receptor affinity with some preference for μ receptors over δ receptors, high potency in the guinea pig ileum assay and considerable activity in the mouse vas deferens assay. Configurational inversion at the 4-position in these cyclic analogues resulted in enhanced affinity for both μ and δ receptors, whereas N-methylation of the Phe³ residue produced a potency decrease.     

Rat model of the human "Triton" tumor: direct genetic evidence for the myogenic differentiation capacity of schwannoma cells using the mutant neu gene as a cell lineage marker

Spontaneous myogenic differentiation was observed in 2 out of 15 cases when cells from schwannomas induced in the offspring of BDIX rats by transplacental exposure to N-ethyl-N-nitrosourea (EtNU) were grown in monolayer culture following fluorescence-activated cell sorting with monoclonal antibody (Mab) 217c. Myotubes and numerous mononucleated cells no longer expressed the Schwann cell antigens 217c and S-100 protein, but rather revealed the presence of desmin, the alpha-sarcomeric form (alpha-sr) of actin, and the cell surface antigen specified by Mab RB21-7, a 250 kD glycoprotein sharing an epitope with the neural cell adhesion molecule (N-CAM). Subcutaneous reimplantation of such cells into syngeneic animals led to the appearance of tumors composed of both S-100 positive Schwann cells and desmin and alpha-sr-actin positive rhabdomyoblasts, thus closely resembling the human "Triton" tumor. With the use of the polymerase chain reaction and allele-specific oligonucleotide hybridization, DNA isolated from individual myotubes was analyzed for the presence of a T----A transversion mutation at nucleotide 2012 of the neu gene, which is diagnostic of EtNU-induced rat schwannomas. All of the amplified DNA isolates contained the mutant neu allele, thus providing direct genetic proof for the capacity of mammalian neuroectodermal cells for myogenic differentiation.     

Characterization of different forms of yeast acid trehalase in the secretory pathway

The biosynthesis and processing of the vacuolar (lysosomal) acid trehalase (molecular mass about 220 kDa) was followed in vivo using mutants conditionally defective in the secretory pathway. A precursor of 41 kDa was found in sec61 mutant cells deficient in translocation of secretory protein precursors into the lumen of the endoplasmic reticulum. Endoglycosidase H and N-glycosidase F treatment of purified acid trehalase in vitro resulted in a 41 kDa band, indicating that the precursor form found in sec61 mutant cells corresponds to the carbohydrate-free form of the enzyme. sec 18 mutant cells, blocked in the delivery of secretory proteins from the endoplasmic reticulum to the Golgi body accumulate a form with a molecular mass of 76 kDa which probably corresponds to a partially glycosylated precursor of the mature acid trehalase. This precursor partially disappears in favour of the appearance of a higher molecular weight component of 180 kDa in sec7 mutants which are blocked in the delivery step of secretory proteins from the Golgi body to the vacuole. In wild-type cells the fully glycosylated mature form of acid trehalase of about 220 kDa was observed accompanied by some 180 kDa and 76 kDa material.