(n.) One of a series of organic compounds, regarded as anhydrides of certain hydroxy acids. In general, they are colorless liquids, having a weak aromatic odor. They are so called because the typical lactone is derived from lactic acid.
Example Sentences:
(1) These compounds were tentatively identified as two epimers at C-23 of 3 alpha,7 alpha,12 alpha-trihydroxy-5 beta-cholestano-26,23-lactone, which were probably artifacts formed from the corresponding tetrahydroxycholestanoic acids during the procedures for extraction after hydrolysis.
(2) Second, both lovastatin and simvastatin are administered as prodrugs in their lactone forms.
(3) The method involves the selective joining of two synthetic fragments, namely residues 1-65 of the apopeptide with Met65 replaced by homoserine lactone and residues 66-104 of the protein in the presence of fragment 1-25 of the native heme-containing peptide.
(4) Two new isomeric delta-lactones 2 and 3 have been isolated from the marine fungus Helicascus kanaloanus (ATCC 18591).
(5) Our data do not support the possibility of hydrogen bonding between the 16 beta-hydroxyl of gitoxigenin and the lactone ring, previously suggested to account for the decreased activity of gitoxigenin vis à vis digitoxigenin, but, rather, suggest that the decreased activity may be due to an intramolecular hydrogen bond between the hydroxyls on C-14 and C-16 and an unusual D-ring conformation which combine to alter the carbonyl oxygen of the lactone ring away from the putative active position.
(6) Status epilepticus was provoked in 10 rats by embedding coriaria lactone particle into the left cerebral motor cortex.
(7) Preliminary results indicate that chloride is eliminated during subsequent lactonization of the 2,3-dichloro-cis,cis-muconate, followed by hydrolysis to form 5-chloromaleylacetic acid.
(8) This ester, on standing, gradually formed the corresponding lactone.
(9) Studies were made on the ultraviolet difference-spectra of glucoamylase from Rhizopus niveus [EC 3.2.1.3] specifically produced by the substrate maltose and the inhibitors, glucose, glucono-1: 5-lactone (gluconolactone), methyl beta-D-glucoside, cellubiose, and cyclohexa-, and cyclohepta-amyloses.
(10) Pharmacokinetics of digitoxin (DGT) and its derivative hydrogenated at the unsaturated lactone ring have been studied using the 3H-labelled compounds in cats.
(11) The enzyme hydrolyzes aldonate lactones, such as D-galactono-gamma-lactone and L-mannono-gamma-lactone, stereospecifically.
(12) Since furanoses in the envelope form are analogous (in some ways) to half-chair or sofa conformations and since lactones with six-membered rings probably have half-chair or sofa conformations, the results indicate that beta-galactosidase probably destabilizes its substrate into a planar conformation of some type and that the galactose in the transition state may, therefore, also be quite planar.
(13) An unusual change in absorbance from 300 to 310-320 nm, obtained only with the valienamine-derived inhibitors or when D-glucono-1,5-lactone and maltose are combined, is concluded to arise when subsite 2 is occupied in a transition-state-type of complex.
(14) These studies showed that neither the strained trans-fused alpha-methylene lactone 12 nor the hydroxy-alpha-methylene lactones 5 and 6 reacted with cysteine with rates comparable to elephantopin.
(15) Relative to that of glucagon, biological activity and affinity of [des-Asn-28,Thr-29](homoserine lactone-27)-glucagon, prepared by CNBr treatment of glucagon, were reduced equally by 40- to 50-fold.
(16) These data indicate that PGF2alpha, 1-15 lactone decreases menstrual cycle lengths in non-pregnant rhesus monkeys.
(17) The metabolic pathway from 1 alpha,25-dihydroxyvitamin D3 [1 alpha,25-(OH)2D3] to 1 alpha,25-dihydroxyvitamin D3-26,23-lactone includes the formation of 1 alpha,23,25-26-tetrahydroxyvitamin D3 [1 alpha,23,25,26-(OH)4D3].
(18) The macrocyclic lactone ring is necessary for antibiotic activity.
(19) The lactones were treated with benzyl mercaptide anion to form 4-(benzylthio)butyric acid, which, on treatment with trifluoroacetic acid, cyclized to yield thiololactones.
(20) Thapsigargin is a potent skin irritating sesquiterpene lactone isolated from the roots of Thapsia garganica L. (Apiaceae).
Lactose
Definition:
(n.) Sugar of milk or milk sugar; a crystalline sugar present in milk, and separable from the whey by evaporation and crystallization. It has a slightly sweet taste, is dextrorotary, and is much less soluble in water than either cane sugar or glucose. Formerly called lactin.
(n.) See Galactose.
Example Sentences:
(1) Peptide:N-glycosidase F removed both the asparagine-linked oligosaccharide chains of ricin B-chain in the absence of lactose.
(2) A relative net reduction of 47% in lactose malabsorption was produced by adding food, and the peak-rise in breath H2 was delayed by 2 hours.
(3) These swine were compared to four groups fed the medicated diet to determine the effect of duration of treatment and degree of animal isolation on the persistence of resistance in lactose-fermenting enteric organisms.
(4) Preliminary results in humans indicate that 3H-I was absorbed to a much greater extent following oral administration of the drug in sesame oil than when admixed with lactose.
(5) Measurements of the lactose repressor over a tenfold range of cell growth rates were made on protein extracts from Escherichia coli cultures grown in media with various carbon energy sources.
(6) A role of lactose synthetase as the rate-limiting enzyme for lactose biosynthesis and the possible significance of the hydrolytic activities are discussed with respect to lactogenesis.
(7) The site I Mn2+, site II Ca2+-activated enzyme has a maximum velocity similar to that of the Mn2+-activated enzyme, and is the enzyme form that must act in lactose synthesis in vivo.
(8) The ABH(+)Le(a-b-) group had higher lactose contents than the other groups (p less than 0.01).
(9) Within that region there were two sequences, 74 and 100 bp long, that showed 46% and 50% identity, respectively, to sequences in the first 600 bp of lacY, the structural gene for the lactose permease.
(10) To determine the validity of breath H2 measurements in detecting lactase deficiency, capillary blood glucose and breath H2 were measured after ingestion of 50 g lactose in 34 patients with abdominal symptoms or diarrhea.
(11) Stationary-phase cells of Escherichia coli were enumerated by the pour plate method on Trypticase soy agar containing 0.3% yeast extract (TSYA), violet red-bile agar, and desoxycholate-lactose agar, and by the most-probable-number method in Brilliant Green-bile broth and lauryl sulfate broth.
(12) Satisfactory calibrations for lactose were obtained with the 2 Milko-scan 203 models with standard errors of estimate of 0.034 and 0.033%.
(13) In trial 1, part 2, supplementation with 4.8% fish meal increased concentration of milk protein and yields of milk, protein, lactose, and SNF.
(14) However, all of the lectins competed for the same binding sites on rabbit erythrocytes, and could be inhibited by the same saccharide haptens (notably lactose and thiodigalactoside).
(15) Hydrogen breath tests were performed in Gabon (Central Africa) after a loading dose of lactose in 67 well-nourished African children (50 with intestinal parasites and 17 unparasitized) and in 18 unparasitized young adults.
(16) Starting from peracetylated chloro- or bromo-glycosyl donors of N-acetylneuraminic acid, N-acetylglucosamine, glucose and lactose, the corresponding p-formylphenyl glycosides were synthesized stereospecifically under phase transfer catalysed conditions at room temperature in yields of 38-67%.
(17) Lactose H2 breath test seems less reliable for our purposes because of the possible presence of children with lactase deficiences, hardly comparable with the mucosal damage.
(18) While the hemagglutination activity of each of the previously described lactose-binding snake venom lectins is inhibited by reducing agent, the activities of BML and JML are not affected by reducing agent.
(19) Since the latter may lead to avoidance of calcium sources and may exacerbate the bone disease in populations at risk, we studied lactose tolerance and histomorphometrically analyzed undecalcified transiliac bone biopsies in a consecutive group of postmenopausal women with the osteoporotic spinal compression fracture syndrome.
(20) A comparison has been made between the physiology and amino acid sequence of the lactose carriers of Klebsiella pneumoniae M5a1 and Escherichia coli K-12.