Alteman

A1 tern an and low molecular weight alteman fractions from F mesenteroides B-1355 are being studied as hulking agents for reduced calorie foods (124), and dextran oligomers containing a(l — 2)-linkages have been proposed for similar appHcations (211). 

The above chemicals can be obtained by fermentation (qv) of other sugars. However, some compounds require sucrose as a unique feedstock. Examples are the polysaccharides dextran, alteman, andlevan, which are produced by specific strains of bacteria (48,54—56). Dextrans are used to make chromatographic separation media, and sulfated dextran derivatives are used as plasma extenders (41). Levans show promise as sweetness potentiators and, along with alteman, have potential as food thickeners and bulking agents in reduced-caloric foods (55,56) (see Carbohydrates). 

FIG. 6.—Two-site insertion mechanism for the synthesis of Leuc. mesenteroides B-1355 alteman by altemansucrase. The symbols are the same as in Fig. 5 with the addition that the two nucleophiles are X and Y X orients its glucosyl unit so that its 6-hydroxyl group can attack at C-l of the apposed glucosyl unit and Y orients its glucosyl unit so that its 3-hydroxyl group can attack at C-1 of the apposed glucosyl units. 

Little, R.E., Kay, G.N., Cavender, J.B., Epstein, A.E., Plumb, V.J. (1990). Torsade de pointes and T-U wave altemans associated with arsenic poisoning. Pacing Clin. Electrophysiol. 13 164-70. 

Pulsus altemans in association with hjrpercapnia occurred in a study of 120 patients who breathed spontaneously during halothane anesthesia (10). End-tidal... 

B-1254, and B-1299 each gave two dextrans with different structures that were separated from each other dextran and alteman, produced by strain B-1355, were also separated in this way [167]. 

ACUTE HEALTH RISKS convulsions labored breathing vomiting apprehension auditory hallucinations tingling sensations of the nose and face facial numbness twitching pulsus altemans ectopic heartbeats tachycardia ventricular fibrillation respiratory failure hemorrhagic pulmonary edema degeneration of renal tubules unconsciousness may result in death. 

Stachybotrys atra, S. altemans and 5. chartarum are synonymous 238) and S. atra is used. Trichoderma lignorum is equated with T. viride 239). 

Other noninvasive techniques to identify risk, such as baroreflex sensitivity, spectral turbulence (45 7), heart rate variability, T-wave altemans (48-51), QT interval prolongation, QT dispersion (52,53), and late potentials (by the signal averaged ECG) (54-56), have been considered in select patient populations (Table 14.2). AU have failed to live up to initial promises. 

The most novel of the noninvasive techniques involves evaluation of microvolt T-wave altemans (MTWA). This noninvasive diagnostic approach detects minute changes in electrical activity in the T-wave as it alternates in shape, amplitude, and timing beat by beat A positive MTWA test has been linked to inducible (48-51) and spontaneous (57,58) maUgnant ventricular arrhythmias. 

Kaufman, E.S., et al., Indeterminate microvolt T-wave altemans tests predict high risk of death or sustained ventricular arrhythmias in patients with left ventricular dysfunction. J Am Coll Cardiol, 2006. 48(7) p. 1399-404. 

Narayan, S.M. and J.M. Smith, Exploiting rate-related hysteresis in repolarization altemans to improve risk stratification for ventricular tachycardia. J Am Coll Cardiol, 2000. 35(6) p. 1485-92. 

Rozanski, J.J. and M. Kleinfeld, Altemans of the ST segment of T wave. A sign of electrical instability in Prinzmetal s angina. Pacing Clin Electrophysiol, 1982. 5(3) p. 359-65. 

Bloomfield, D.M., et al.. Microvolt T-wave altemans distinguishes between patients likely and patients not likely to benefit from implanted cardiac defibrillator therapy a solution to the Multicenter Automatic Defibrillator Implantation Trial (MADIT) II conundrum. Circulation, 2004.110(14) p. 1885-9. 

Gold, M.R., et al., T-Wave Altemans SCD HeFT Study Primary Endpoint Analysis. Circulation, 2006.114 p. II-428-9. 

Clusin WT (2003) Calcium and cardiac arrhythmias DADs, EADs, and altemans. Crit Rev Clin... 

Class 2 dextrans (altemans) contain a backbone structure of alternating a (1 3)... 

Figure 6.16. (continued) C, S. mutans alternating comb dextran D, L. mesenteroides B-1355 alteman E, S. mutans mutan. 

The complete biosynthesis of xanthan, a water-soluble bacterial polysaccharide with a cellulose backbone (see Chapter 6, Fig. 6.18 for the structure), has been worked out by Dankert et al. [111-114]. The pentasaccharide repeating unit is attached to a polyprenol pyrophosphate lipid carrier [111], and the polymerization takes place by the addition of the repeating pentasaccharide from the polyprenol pyrophosphate pentasaccharide to the reducing end of the growing xanthan chain [114]. The mechanism of xanthan chain elongation is an insertion mechanism similar to those of murein. Salmonella 0-antigen, the dextrans, mutan, and alteman. 

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