Biochemical characteristics, metabolism, and antitumor activity of several acetylated hexosamines

We have synthesized several potential inhibitors and/or modifiers of the carbohydrate portion of plasma membrane glycoconjugates. These include fluorinated and actylated analogs of D-glucosamine, D-galactosamine, and D-mannosamine. These compounds have been tested to determine their effects on both[14C] glucosamine and [3H] leucine incorporation into glycoconjugate and on cell growth and viability using P-288 murine lymphoma cells maintained in tissue culture. The most cytotoxic agent tested was 2-acetamido-2-deoxy-1,3,4,6-tetra-O-acetyl-beta-D-glucopyranose or simply beta-pentaacetylglucosamine which prevented cell growth at 10(-4)-10(-3) M. beta-Pentaacetylglucosamine cytotoxicity was correlated with its high lipid solubility, having an octanol/water partition coefficient of 0.424 as compared with 0.278 for the alpha-anomer and 0.017 for N-acetylglucosamine. In vitro metabolism studies with [4C]- and/or [3H]-labeled pentaacetylglucosamine have indicated intracellular de-O-acetylation leading to the biosynthesis of UDP-N-acetylglucosamine, followed by the incorporation of this sugar into cellular glycoprotein. Concomitant with the formation of increased amounts of this nucleotide sugar, intracellular UTP and CTP pools fell to one third normal within 3 h after the administration of 1 mM pentaacetylglucosamine. At present it is unclear whether the cytotoxicity of beta-pentaacetylglucosamine or other similar agents is due to alterations in nucleotide and nucleotide-sugar pools causing a decrease in energy charge and polynucleotide biosynthesis or is due to a direct effect on membrane glycoconjugate biosynthesis.     

Different phase-stable relationships of the upper lip and jaw for production of vowels and diphthongs.

Relational invariants have been reported in the timing of articulatory gestures across suprasegmental changes, such as rate and stress. In the current study, the relative timing of the upper lip and jaw was investigated across changes in both suprasegmental and segmental characteristics of speech. The onset of upper lip movement relative to the vowel-to-vowel jaw cycle during intervocalic bilabial production was represented as a phase angle, and analyzed across changes in stress, vowel height, and vowel/diphthong identity. Results indicated that the relative timing of the upper lip and jaw varied systematically with changes in stress and vowel/diphthong identity, while remaining constant across changes in vowel height. It appears that modifications in relative timing may be due to adjustments in the jaw cycle as a result of the compound nature of jaw movement for diphthongs as compared to vowels, with further modifications due to the effect of stress on these compound movements.     

Structural reassignment of the dehydration product of 2′-Hydroxywarfarin

The base catalyzed condensation reaction between 4-hydroxycoumarin and o-hydroxybenzal-acetone yields 6-methyl-6,12-methano-6H,12H,13H-[1]benzopyran[4,3-d][1,3]benzodioxocin-13-one as the product rather than 6-oxo-7-(2-oxopropyl)-6H, 7H-[1]benzopyrano[4,3-b][1]-benzopyran as had been previously postulated.     

Nonlinear Dynamical Systems in Speech Perception and Production

Research examining the nonlinear, dynamical-systems aspects of speech production and perception is reviewed. Examples are provided from studies of phonation, speech respiration, vocal tract acoustics, speech gestures, and auditory-phonetic perception. Results support a conclusion that nonlinear, dynamical system behaviors and principles are represented in speech production and perception at several levels of system behavior. The results are interpreted as suggesting that the communicative distinctions in speech are represented in task-relevant, order parameters which are preserved over a wide range of sets of task-irrelevant, control parameters. The control parameters, in turn, define the domains of behavior for each of the relevant acoustic, biological, or psychological systems. More specifically, it is proposed that speech order parameters may be understood in terms of collective variables defined, in production, over the degrees of, and opening/closing rates of, the vocal tract and, in perception, over the rates, amounts, and relative phases of the broad-band temporal modulations in speech signals.     

A latent entanglement model for the draw of semicrystalline polymers

A novel molecular model, the latent entanglement, is proposed to explain the relationships between ductilities of polyethylene reactor powders and different conditions of synthesis. According to Hoffman's variable cluster model, irregularities in the crystallite fold surface increase as the synthesis temperature is decreased. The concept of latent entanglement stems from the potentiality of these defects to convert into active entanglements when the involved chain segments are drawn out of the crystals.