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At least 613 records · Page 34Linked to original sources
PubMed2006

Lipoxygenase from banana leaf: purification and characterization of an enzyme that catalyzes linoleic acid oxygenation at the 9-position.

The objective of the present study was to purify and characterize the lipoxygenase (LOX) from banana leaf (Giant Cavendishii, AAA), an unutilized bioresource. LOX was extracted, isolated, and purified 327-fold using 25-50% saturation of ammonium sulfate fractionation, hydroxyapatite column separation, and gel filtration on Superdex 200. The molecular mass of the purified LOX was 85 kDa, K(m) was 0.15 mM, and V(max) was 2.4 microM/min.mg using linoleic acid as substrate. Triton X-100 was required in the extraction medium; otherwise, no LOX activity was detected. LOX activity increased with the concentration of Triton X-100 with an optimum at 0.1%. The optimal pH of the purified LOX from banana leaf was 6.2, and optimal temperature was 40 degrees C. The LOX showed the highest reactivity toward 18:2 followed by 18:3 and 20:4. A very low reaction rate was observed toward 20:5 and 22:6. On the basis of retention time in normal phase HPLC, the products of 18:2 or 18:3 catalyzed by purified LOX were hydroperoxyoctadecadienoic acid or hydroperoxyoctadecatrienoic acid. It seems that 9-LOX is the predominant enzyme in banana leaf. Banada leaf dried at 110 degrees C for 2 h developed algal aroma. Banana leaf extract stored at 10 degrees C for 12 h formed an oolong tea-like flavor. Banana leaf extract reacted with 18:2 or soybean oil pretreated with bacterial lipase produced green and melon-like aroma, whereas the same reaction with 18:3 produced a sweet, fruity, cucumber-like flavor note.

Binding Sites↗
PubMed2006

Molecular cloning and characterization of an alpha-amylase occurring in the pulp of ripening bananas and its expression in Pichia pastoris.

Alpha-amylases (EC 3.2.1.1) are glycosyl hydrolases with endoglycolytic activity on the alpha-1,4-d-glucosidic linkages in starch. In bananas, the mobilization of starch accounts for sugar accumulation during ripening, and among several hydrolytic enzymes, alpha-amylase is the only enzyme argued to be able to attack the intact granules, indicating a pivotal role for this enzyme. A 1953 bp full-length banana alpha-amylase cDNA (MAmy), encoded for a sequence of 416 amino acids, was cloned and used for heterologous expression in Pichia pastoris. The cloned MAmy presented the highly conserved motifs common to alpha-amylases, and the amylolytic activity of the extracts from yeast transformed with MAmy demonstrated that it encodes for a functional alpha-amylase, suggesting a putative role for this gene in starch degradation during fruit ripening.

Amino Acid Sequence↗
PubMed2006

Quantitation of fatty acids, sterols, and tocopherols in turpentine (Pistacia terebinthus Chia) growing wild in Turkey.

The chemical composition (fatty acids, tocopherols, and sterols) of the oil from 14 samples of turpentine (Pistacia terebinthus L.) fruits is presented in this study. The oil content of the samples varied in a relatively small range between 38.4 g/100 g and 45.1 g/100 g. The dominating fatty acid of the oil is oleic acid, which accounted for 43.0 to 51.3% of the total fatty acids. The total content of vitamin E active compounds in the oils ranged between 396.8 and 517.7 mg/kg. The predominant isomers were alpha- and gamma-tocopherol, with approximate equal amounts between about 110 and 150 mg/kg. The seed oil of P. terebinthus also contained different tocotrienols, with gamma-tocotrienol as the dominate compound of this group, which amounted to between 79 and 114 mg/kg. The total content of sterols of the oils was determined to be between 1341.3 and 1802.5 mg/kg, with beta-sitosterol as the predominent sterol that accounted for more than 80% of the total amount of sterols. Other sterols in noteworthy amounts were campesterol, Delta5-avenasterol, and stigmasterol, which came to about 3-5% of the total sterols.

Fatty Acids↗
PubMed2006

Effects of ethylene and 1-methylcyclopropene (1-MCP) on gene expression and activity profile of alpha-1,4-glucan-phosphorylase during banana ripening.

Starch phosphorylases are enzymes that can use starch as substrate, and they are supposed to act in both in starch synthesis and degradation. This paper reports the effects of ethylene and 1-methylcyclopropene (1-MCP) on the degradation of starch and phosphorylase activity and gene expression. The results indicate that phosphorylase activity is induced during ripening and that it is associated with the onset of starch degradation. The regulation of banana phosphorylase activity is mainly dependent on gene expression, and the absence of ethylene perception by 1-MCP had a positive effect. However, this effect can be precluded by increased levels of ethylene, both autocatalytic and exogenous.

Cyclopropanes↗
PubMed2006

N,N-bond-forming heterocyclization: synthesis of 3-alkoxy-2H-indazoles.

A one-step heterocyclization of o-nitrobenzylamines to 3-alkoxy-2H-indazoles is reported. The electronic nature of the nitrophenyl group, the steric and electronic nature of the R1-functionalized benzylic amine, and the nature of the alcoholic solvent affect the efficiency of this heterocyclization reaction (approximately 40-90%).

Cyclization↗
PubMed1997

Lewis Acid Activation and Catalysis of Dialkylaminyl Radical Reactions.

Lewis acid activation and catalysis of dialkylaminyl radical reactions is demonstrated both qualitatively and quantitatively. Cyclization of the N-butyl-4-pentenaminyl radical (1) in the presence of a wide range of Lewis acids was shown to be efficient with good to excellent yields of cyclic products obtained in reactions conducted even at -78 degrees C. Rate constants for fragmentation of the N-ethyl-2,2-diphenylethylaminyl radical (6), 6-exo cyclization of the N-methyl-6,6-diphenyl-5-hexenaminyl radical (7), and 5-exo cyclization of the N-methyl-5,5-diphenyl-4-pentenaminyl radical (8) in the presence of the Lewis acids LiBF(4), MgBr(2), and BF(3) were measured by laser flash photolysis (LFP) methods. The LFP studies demonstrated saturation kinetic behavior with respect to the Lewis acids. Equilibrium binding constants for the Lewis acids with the dialkylaminyl radicals and rate constants for reactions of the Lewis acid complexed dialkylaminyl radicals were obtained from nonlinear regression analysis of the observed rate constants.

Journal Article↗
PubMed1998

Absolute Rate Constants for alpha-Amide Radical Reactions.

The 1-(diethylcarbamoyl)-6,6-diphenyl-5-hexenyl radical (4a), the 1-(diethylcarbamoyl)-7,7-diphenyl-6-heptenyl radical (4b), and the 1-(diethylcarbamoyl)-1-methyl-6,6-diphenyl-5-hexenyl radical (4c) were produced from the corresponding PTOC esters (anhydrides of the carboxylic acid and N-hydroxypyridine-2-thione) by laser flash photolysis methods. The kinetics of cyclizations of radicals 4a and 4b were measured at various temperatures, and that of cyclization of 4c was measured at ambient temperature. Radicals 4a and 4b were employed as radical clocks in indirect kinetic studies to determine rate constants for reaction of secondary alpha-amide radicals with Bu(3)SnH. The calibrated tin hydride trapping reaction was then employed to determine rate constants for cyclization of the 1-(diethylcarbamoyl)-5-hexenyl radical (12). The rate constants for 5-exo cyclizations of secondary alpha-amide radicals are similar to those of their isostructural alkyl radical analogues. The rate constants for the 5-exo cyclization of tertiary alpha-amide radical 4c and the 6-exo cyclization of the secondary alpha-amide radical 4b are smaller than those of the analogous alkyl radicals and alpha-ester substituted radicals, apparently due to steric effects. The rate constants for tin hydride trapping of secondary alpha-amide radicals are similar to those for reactions with secondary alpha-ester radicals.

Journal Article↗
PubMed2005

Stacking structure of concentrated shear ordered dispersions by two scattering methods.

In this paper, the ordering in concentrated charge stabilized colloidal dispersions is considered. Despite the impressive Bragg reflections obtained for shear ordered dispersions by light (LS), small-angle neutron (SANS), and small-angle X-ray scattering (SAXS), a number of open questions remain. Sheared dispersions are usually ordered in layers. For such systems, two questions arise: (1) What is the structure in a layer? (2) What is the stacking structure perpendicular to the layers? The second question requires a method to determine the structure perpendicular to the layers. Although originally interested only in structural aspects, we were forced to consider different methods. Two methods are treated both applicable to neutron and X-ray scattering from concentrated dispersions. One has been used by physicists and chemists for many years to determine the structure of crystals by sample rotation. In colloid science, we have used it previously in neutron and X-ray scattering. A second method is treated here which can be applied in small-angle scattering from a Couette cell. It gives the scattering intensity in a certain direction without sample rotation. Although very useful with the Couette cell, it cannot be found in any of the well-known references on colloid science. A theoretical explanation and experimental examples obtained by synchrotron X-ray scattering from a Couette cell are given in the paper.

Journal Article↗
PubMed2002

Ecdysteroids of Vitex scabra stem bark.

Two new ecdysteroids, 24-epi-pinnatasterone (1) and scabrasterone (2), together with 11 known ecdysteroids, calonysterone, pterosterone, 24-epi-makisterone A, 20-hydroxyecdysone (3), polypodine B, ajugasterone C, pinnatasterone (4), 11alpha-hydroxyecdysone, 24-epi-abutasterone, 20,26-dihydroxyecdysone, and turkesterone (5), were isolated from the stem bark of Vitex scabra. This plant species contained a very high concentration (1.8%) of 3 and thus provided a good source of this parent ecdysteroid and related rare ecdysteroids. Compounds 1 and 2 exhibited very low moulting activity in the Musca bioassay. The low biological activity of these two ecdysteroids was in agreement with those of other 22-deoxyecdysteroids.

Acetylation↗
PubMed1999

Self care for chronic illness: older African Americans and whites.

In-person interviews with two hundred and twenty-one older African Americans and whites in Allegheny County, Pennsylvania on their use of self care activities in the care of one of four chronic illnesses (chronic obstructive pulmonary disease (COPD), heart disease, diabetes mellitus, and arthritis, addressed which types of self care they used for each of these illnesses) the similarities and differences between African Americans and whites in their use of self care and how self care is initiated, modified and integrated into a context that includes help from others. The most common response in each of the illnesses was the use of medications or medical treatments by both African Americans and whites. However, there were some differences in the self care practices used by these two groups by illness type. Whites reported monitoring their illness significantly more than African Americans for diabetes and using assistive devices in the management of COPD significantly more than African Americans. While both African Americans and whites practice self care similarly in the management of heart disease, African Americans reported greater use of exercise in their management of arthritis. The amount of assistance provided by others in support of self care varied by illness and by African American and white. The differences in self care usage may be attributed to many factors, among them, differences in cultural experiences with the illness, health beliefs regarding its efficacy and the amount of assistance received from informal supports.

Journal Article↗
PubMed2000

The meaning of healthy and not healthy: older African Americans and whites with chronic illness.

Qualitative in-person interviews with 114 older African Americans and whites with chronic illness were conducted to assess whether they thought of themselves as healthy or not healthy and the meanings associated with that assessment. The first and most frequently assigned attribute of healthy was the presence of functional capacities; for not healthy it was the presence of medical conditions or physical symptoms. While both African Americans and whites responded similarly regarding the assessment of whether they were healthy or not healthy, African Americans described the attributes associated with healthy or not healthy somewhat differently than whites. Also, both groups reported more varied meanings to the concept of 'healthy' than to 'not healthy', suggesting that 'healthy' may be a multidimensional construct more connected to ones' total life experiences than is 'not healthy'. This study concludes that social and cultural factors such as race, ethnicity or health experiences may influence how individuals perceive and describe their health status and the processes used in making these assessments.

Journal Article↗
PubMed2001

Identification and expression of the Pseudomonas syringae pv. aptata hrpZ(Psa) gene which encodes an harpin elicitor.

A sequence homologous to an internal fragment 0.75 kb BstXI of the Pseudomonas syringae pv. syringae hrpZ gene was identified in Pseudomonas syringae pv. aptata NCPPB 2664, the causal agent of bacterial blight in sugar beet, lettuce and other plants. and in E. coli DH10B (pCCP1069) containing the P. syringae pv. aptata hrp gene cluster. PCR with oligonucleotides, based on the hrpZ(Pss) gene and used as primers with the total genomic DNA of P. syringae pv. aptata, amplified a 1 kb fragment that hybridized with the probe in highly stringent conditions. The amplicon was cloned into the pGEM-T plasmid vector, amplified in E. coli DH5alpha and sequenced. The sequence showed 95%, 83% and 61% identity with those of hrpZ(Pss), hrpZ(Psg and hrpZ(Pst) genes encoding the harpins of the P. syringae pv. syringae, glycinea and tomato, respectively. The amplicon was cloned into the pMAL expression system. The expressed protein, fused with maltose-binding protein, was cleaved with a specific protease factor Xa, and purified using affinity chromatography. On the basis of the amino acid sequence and its ability to induce HR in tobacco leaves, it was identified as a P. syringae pv. aptata harpin.

Amino Acid Sequence↗
PubMed2002

An attempt to decrease ammonia levels after portacaval anastomosis in dogs: hepatic periarterial neurectomy.

Hepatic encephalopathy and elevated serum ammonia levels occur commonly after portacaval shunt and are hypothesized to be, in part, due to decreased hepatic blood flow. Prior work has demonstrated increased blood flow to the liver following hepatic periarterial neurectomy. In this experimental study, we investigated the functional, hemodynamic, and histopathological changes in the liver and kidney occurring after the addition of hepatic periarterial neurectomy to side-to-side portacaval shunt in dogs. It is our hypothesis that the addition of hepatic periarterial neurectomy to portacaval shunt will decrease postshunt ammonia levels. Side-to-side portacaval shunt was performed in 12 dogs (group I). Hepatic periarterial neurectomy was added to portacaval shunt in 9 dogs (group II). Serum levels of ammonia, urea, creatinine, alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, albumin, and bilirubin together with hepatic blood flow were determined in both groups preoperatively and on postoperative day 21. The pre- and postoperative histopathologic changes of the liver and kidney were evaluated. There was significantly less postoperative elevation of serum ammonia and aspartate aminotransferase when hepatic periarterial neurectomy was added to the portacaval shunt procedure. Hemodynamic studies of hepatic artery and hepatic tissue indicated better blood flow in group II. The histopathologic evaluation of group II showed expansion of sinusoids, portal vessels, and portal areas and increased portal fibrosis as compared to group I. The results of this experimental study show that adding hepatic periarterial neurectomy to the portacaval shunt procedure improves postoperative serum levels of ammonia and aspartate aminotransferase and hepatic artery and tissue blood flow.

Ammonia↗
PubMed2003

Pectate lyase gene expression and enzyme activity in ripening banana fruit.

Two distinct cDNA clones showing sequence homology to higher-plant pectate lyase (Pel) genes were isolated from ripening banana fruits. The transcripts were detected only in fruit tissue and both were strongly ripening-related. Yeast transformation with the most highly expressed Pel clone produced a recombinant protein with pectate lyase activity, demonstrating that this sequence was likely to encode a pectate lyase protein in planta. An assay developed for measuring the action of the endogenous enzyme from banana pulp tissue revealed a significant increase in calcium-dependent pectate lyase activity during ripening. The enhanced levels of enzyme activity corresponded with an increase in soluble polyuronides from banana pulp.

Blotting, Northern↗
PubMed2003

Pentose phosphate pathway, glutathione-dependent enzymes and antioxidant defense during oxidative stress in diabetic rodent brain and peripheral organs: effects of stobadine and vitamin E.

The aim of the present study was to investigate the effects of treatment with antioxidant stobadine (ST) on the activities of enzymes related with pentose phosphate pathway and glutathione-dependent metabolism and the other markers of oxidative stress in brain and peripheral organs of diabetic rats, and to compare the effects of ST treatment alone with the effects of treatments with another antioxidant vitamin E and ST plus vitamin E. Rats were made diabetic by the injection of streptozotocin (STZ; 55 mg/kg IP), and, 2 days later, some control and diabetic rats were left untreated or treated with ST (24.7 mg/kg/day, orally), vitamin E (400-500 U/kg/day, orally), or both substances together. In the brain, although 6-phosphogluconate dehydrogenase activity (6-PGD) did not change, glucose-6-phosphate dehydrogenase activity (G-6PD) was markedly increased in diabetic rats compared with controls; only combined treatment with ST and vitamin E produced a partial prevention on this alteration. The aorta G-6PD and 6-PGD of diabetic rats were 52% and 36% of control values, respectively. Neither single treatments with each antioxidant nor their combination altered the G-6PD and 6-PGD in aorta of diabetic rats. Glutathione peroxidase (GSHPx) activity was increased by STZ-diabetes in brain, heart, and kidney. In diabetic brain, vitamin E alone or combination with ST kept GSHPx at normal levels. Diabetes-induced stimulation in GSHPx did not decrease in response to the treatment with vitamin E in heart and kidney, but was greatly prevented by ST alone. The activity of glutathione reductase (GR) was decreased in brain and heart of diabetic rats. The treatment with each antioxidant or with a combination of both agents completely prevented this deficiency and resulted in further activation of GR in diabetic tissues. Glutathione S-transferase (GST) activity did not significantly change in diabetic brain and aorta. GST was stimulated by all treatment protocols in the brain of diabetic rats and was depressed in aorta of control rats. Catalase (CAT) was activated in diabetic heart but depressed in diabetic kidney. Diabetes-induced abnormalities in CAT activity did not respond to vitamin E alone in heart, was moderately ameliorated by the treatment with this vitamin in kidney, and was completely prevented by ST alone in both tissues. Superoxide dismutase (SOD) activity of brain and heart was unchanged by the diabetes but inhibited in diabetic kidney after the treatment ST alone or ST plus vitamin E. The lipid peroxidation (MDA) was increased in diabetic brain and heart. ST or vitamin E alone partly prevented diabetes-induced increase in MDA in brain and heart; however, antioxidant combination achieved a completely amelioration in MDA of these tissues of diabetic rats. Kidney MDA levels were similar in control and untreated diabetic animals. ST and vitamin E treatments, when applied separately or together, significantly reduced kidney MDA in both control and diabetic rats; and the combined effect of antioxidants was greater than that of each alone. These results are consistent with the degenerative role of hyperglycemia on cellular reducing equivalent homeostasis and antioxidant defense, and provide further evidence that pharmacological intervention of different antioxidants may have significant implications in the prevention of the prooxidant feature of diabetes and protects redox status of the cells.

Animals↗
PubMed2004

Green banana and pectin improve small intestinal permeability and reduce fluid loss in Bangladeshi children with persistent diarrhea.

To evaluate the effects of green banana and pectin (nondigestible, dietary sources of colonic shortchain fatty acids [SCFA]) on intestinal permeability, 57 boys (5-12 months) with persistent diarrhea (> or = 14 days) were given a week's treatment with a rice-based diet containing either cooked green banana (n = 19), pectin (n = 17), or rice diet alone (n = 21). Intestinal permeability was assessed before and after treatment by giving a lactulose-mannitol (LM) drink and measuring urinary recovery after 5 hr. Treatment with banana significantly (P < 0.05) reduced lactulose recovery, increased mannitol recovery, and decreased the LM ratio, indicating improvement of permeability. Pectin produced similar results. Permeability changes were associated with a 50% reduction in stool weights which correlated strongly (green banana, r2 = 0.84, pectin, r2 = 0.86) with the LM ratio. Green banana-derived and SCFA-mediated stimulation of colonic as well as small bowel absorption is responsible for their antidiarrheal effects. The antidiarrheal effects of green banana and pectin are mediated by improvement of small intestinal permeability in addition to their known colonotrophic effects.

Antidiarrheals↗