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Biomedical subjects

M Wein

Publications and source records attributed to M Wein.

15 recordsLinked to original sources
PubMed2001

Metabolic fate of isotopes during the biological transformation of carbohydrates to 2,5-dimethyl-4-hydroxy-3(2h)-furanone in strawberry fruits.

Isotopically labeled D-glucose, D-fructose, 1-deoxy-D-fructose, and 6-deoxyhexoses were applied to detached ripening strawberry (Fragaria x ananassa) fruits, and the incorporation of the isotopes into the key strawberry aroma compounds 2,5-dimethyl-4-hydroxy-3(2H)-furanone (DMHF, 1) and 2,5-dimethyl-4-methoxy-3(2H)-furanone (DMMF, 2) was determined by gas chromatography-mass spectrometry. In contrast to previous reports the data clearly showed that 6-deoxy-D-fructose/6-deoxy-D-glucose and 1-deoxy-D-fructose are not natural precursors of the furanones. However, isotopically labeled 1 and 2 were observed after the application of [1-(2)H]-, [2-(2)H]-, and [6,6-(2)H(2)]-D-glucose as well as [U-(13)C(6)]-, [1-(13)C]-, [1-(2)H]-, [6,6-(2)H(2)]-D-fructose. The isotope label of [4-(2)H]-D-glucose was not recovered in the furanones. In contrast, [2-(2)H]-D-glucose was converted to [1- or 6-(2)H]-1 and [1- or 6-(2)H]-2 by the strawberry fruits. The observed isotope shift can be explained by the catalysis of phosphohexose isomerase in the course of the biogenesis of the hydroxyfuranone (1) and the methoxyfuranone (2) from D-glucose. Thus, the applied D-glucose is metabolized to D-fructose-6-phosphate prior to the transformation into the furanones.

Fruit↗
PubMed2001

The strawberry FaMYB1 transcription factor suppresses anthocyanin and flavonol accumulation in transgenic tobacco.

Fruit ripening is characterized by dramatic changes in gene expression, enzymatic activities and metabolism. Although the process of ripening has been studied extensively, we still lack valuable information on how the numerous metabolic pathways are regulated and co-ordinated. In this paper we describe the characterization of FaMYB1, a ripening regulated strawberry gene member of the MYB family of transcription factors. Flowers of transgenic tobacco lines overexpressing FaMYB1 showed a severe reduction in pigmentation. A reduction in the level of cyanidin 3-rutinoside (an anthocyanin) and of quercetin-glycosides (flavonols) was observed. Expression of late flavonoid biosynthesis genes and their enzyme activities were adversely affected by FaMYB1 overexpression. Two-hybrid assays in yeast showed that FaMYB1 could interact with other known anthocyanin regulators, but it does not act as a transcriptional activator. Interestingly, the C-terminus of FaMYB1 contains the motif pdLNL(D)/(E)Lxi(G)/S. This motif is contained in a region recently proposed to be involved in the repression of transcription by AtMYB4, an Arabidopsis MYB protein. Our results suggest that FaMYB1 may play a key role in regulating the biosynthesis of anthocyanins and flavonols in strawberry. It may act to repress transcription in order to balance the levels of anthocyanin pigments produced at the latter stages of strawberry fruit maturation, and/or to regulate metabolite levels in various branches of the flavonoid biosynthetic pathway.

Amino Acid Sequence↗
PubMed2001

Rapid progression of bacterial aortitis to an ascending aortic mycotic aneurysm documented by transesophageal echocardiography.

A case of bacterial aortitis of the ascending aorta caused by Staphylococcus aureus progressed to an aortic mycotic aneurysm. Transesophageal echocardiography was the diagnostic approach of choice. The different stages of the disease from the initial aortic wall infection to formation of an abscess that communicated with the aortic lumen were documented by transesophageal echocardiography.

Aneurysm, Infected↗
PubMed2001

2,5-Dimethyl-4-hydroxy-3(2H)-furanone as a secondary metabolite from D-fructose-1,6-diphosphate metabolism by Zygosaccharomyces rouxii.

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) is an important aroma compound found in many fruits such as strawberries and pineapples and it is also produced by the soy-sauce-fermenting yeast Zygosaccharomyces rouxii after the addition of d-fructose-1,6-diphosphate to yeast-peptone-dextrose nutrient media. Dilute DMHF solutions exhibit a strawberry-like flavor while DMHF concentrates have a caramel-like aroma. In media containing D-fructose-1,6-diphosphate as the sole carbon source, growth of Z. rouxii and formation of DMHF were not observed. Although Z. rouxii cells grew in media with D-glucose as the sole carbon source, DMHF was only produced when media were supplemented with D-fructose-1,6-diphosphate. The DMHF concentration always correlated with the yeast cell count and D-fructose-1,6-diphosphate concentration. Addition of CaCl2 (up to 50 g.l(-1)) led to a higher DMHF concentration. Addition of Na2SO3 reduced the growth of Z. rouxii and inhibited DMHF formation. The amount of DMHF formed by Z. rouxii was not significantly affected by the addition of KH2PO4. DMHF concentrations of 5 and 10 g.l(-1) partially and completely inhibited the growth of Z. rouxii cells, respectively. Only the singly labeled furanone was formed after the addition of 1-13C-D-fructose-1,6-diphosphate to the medium. However, unlabeled DMHF was formed in the presence of (13)C(6)-D-glucose. Therefore, the carbons of the furanone originate exclusively from exogenously supplied D-fructose-1,6-diphosphate as no exchange with the internal pool of D-fructose-1,6-diphosphate occurs. This implies that DMHF is a secondary metabolite of Z. rouxii formed from D-fructose-1,6-diphosphate. We assume that at least the first step of the metabolism of D-fructose-1,6-diphosphate takes place in the cell wall or membrane of the yeast.

Journal Article↗
PubMed1999

Novel 1,3-dioxanes from apple juice and cider.

Extracts obtained by XAD solid-phase extraction of apple juice and cider were separated by liquid chromatography on silica gel. Several new 1,3-dioxanes including the known 2-methyl-4-pentyl-1,3-dioxane and 2-methyl-4-[2'(Z)-pentenyl]-1,3-dioxane, were identified in the nonpolar fractions by GC/MS analysis and confirmed by chemical synthesis. The enantioselective synthesis of the stereoisomers of the 1,3-dioxanes was performed using (R)- and (R,S)-octane-1,3-diol and (R)- and (R,S)-5(Z)-octene-1,3-diol as starting material. Comparison with the isolated products indicated that the natural products consisted of a mixture of (2S,4R) and (2R,4R) stereoisomers in the ratio of approximately 10:1, except for 1,3-dioxanes generated from acetone and 2-butanone. It is assumed that the 1, 3-dioxanes are chemically formed in the apples and cider from the natural apple ingredients (R)-octane-1,3-diol, (R)-5(Z)-octene-1, 3-diol, (3R,7R)- and (3R,7S)-octane-1,3,7-triol, and the appropriate aldehydes and ketones, which are produced either by the apples or by yeast during fermentation of the apple juice.

Beverages↗
PubMed1997

A fatty acid alpha-ketol, a product of the plant lipoxygenase pathway, is oxidized to 3(Z)-dodecendioic acid by a bacterial monooxygenase.

The fatty acid alpha-ketol 13-hydroxy-12-oxo-9(Z)-octadecenoic acid (methyl ester) was incubated with a bacterial culture isolated from soil. The bacteria (tentatively identified as Ralstonia sp.) exhibited strong monooxygenase activity growing on 2-tridecanone as sole source of carbon. They catalyzed a Baeyer-Villiger type of oxidation and converted the alpha-ketol to 3(Z)-dodecendioic acid. 3(Z)-Dodecendioic acid was isolated from the incubation mixture and identified by comparison with an authentic reference compound. These findings offer both a physiological role for alpha-ketol fatty acids in plant lipid hydroperoxide metabolism and new insights into an alternative biosynthetic pathway leading to traumatic acid (2(E)-dodecendioic acid).

Bacterial Proteins↗
PubMed1996

Sex- and age-related antihypertensive effects of amlodipine. The Amlodipine Cardiovascular Community Trial Study Group.

This community-based study assessed whether there were age, sex, or racial differences in response to amlodipine 5 to 10 mg once daily in patients with mild to moderate essential hypertension. This prospective, open-label trial had a 2-week placebo period, a 4-week upward drug titration/efficacy period, and a 12-week drug maintenance period. There were 1,084 evaluable patients (mean age 55.5 years; 65% men and 35% women; 79% white and 21% black; 75% <65 and 25% > or = 65 years old). At the end of the titration/efficacy phase, the mean +/- SD blood pressure (BP) decreased by -16.3 +/- 12.3/-12.5 +/- 5.9 mm Hg, (p < or = 0.0001). Amlodipine produced a goal BP response (sitting diastolic BP < or = 90 mm Hg, or a 10 mm Hg decrease) in 86.0% of patients overall. The BP response was greater in women (91.4%) than in men (83.0%, p < or = 0.001), and greater in those > or = 65 years old (91.5%) than in those < 65 years old (84.1%, p < or = 0.01); however, it was similar between whites and blacks (86.0% vs 85.9%, respectively, p = NS). The sex difference in BP response could not be fully explained by differences in age, weight, dose (mg/kg), race, baseline BP, or compliance, and there were no differences among women based on use of hormone replacement therapy. Amlodipine was well tolerated; mild to moderate edema was the most common adverse effect. Thus, amlodipine was effective and safe as once-a-day monotherapy in the treatment of mild to moderate hypertension in a community-based population. Women had a greater BP response to amlodipine.

Adult↗
PubMed1995

Effect of amlodipine on left ventricular mass in the Amlodipine Cardiovascular Community Trial.

As part of the Amlodipine Cardiovascular Community Trial (ACCT), which was a large multicenter study designed to assess the effects of the calcium channel blocker amlodipine besylate (Norvasc) as monotherapy for treatment of mild to moderate hypertension, we sought to determine the effects of amlodipine on regression of left ventricular (LV) hypertrophy (LVH). The study began with a 2-week placebo run-in period (baseline), before which antihypertensive drugs had been discontinued. Amlodipine was then administered at 5-10 mg/day during a 4-week titration/efficacy period. Patients achieving a goal diastolic blood pressure (DBP) of < or = 90 mm Hg or a decrease in DBP of > or = 10 mm Hg entered a 12-week maintenance phase and had the option to continue long-term therapy thereafter. Echocardiograms were obtained in a subset of patients at the end of the baseline period. In patients with LVH at baseline, echocardiograms were repeated at the end of 16 weeks of therapy (week 18), and at 42 weeks in patients continuing long-term therapy. Thirty-seven percent of 124 hypertensive patients screened for LVH at baseline had LVH detected on echocardiograms. Blacks had a higher incidence of LVH (64%) as compared with whites (34%, p < 0.05). Patients with LVH were more likely to have a higher baseline systolic BP (SBP) and DBP. Their sitting SBP and DBP decreased significantly from a mean of 163/102 mm Hg at baseline to 139/86 mm Hg with amlodipine therapy at week 18 (p < 0.0001).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1995

Comparison of human eosinophil and neutrophil ligands for P-selectin: ligands for P-selectin differ from those for E-selectin.

Eosinophils (EOS) and neutrophils (PMN) display different patterns of accumulation during various inflammatory reactions. We hypothesized that EOS and PMN may differ in their ligands for P-selectin, and that these ligands may differ from those previously identified for E-selectin. Recombinant human P-selectin was immobilized on plastic surfaces and adhesion of 51Cr-labeled human EOS or PMN was compared. EOS and PMN adhered in a concentration-dependent fashion, with similar maximal net adhesion. Preincubation with a blocking P-selectin antibody inhibited adhesion of both cell types, whereas a non-blocking antibody did not. To determine if the counterligands were sialylated proteins, cells were treated with various glycosidases and proteases before testing adhesion. Neuraminidase treatment markedly inhibited binding of both cell types, while endo-beta-galactosidase had no significant effect. Pretreatment with several proteases reduced adhesion of both cell types, although they consistently caused a greater inhibition of PMN binding than EOS binding. To determine whether the P-selectin ligands were surface structures whose expression or function may be altered by cell activation, leukocytes were pretreated with various stimuli; only platelet-activating factor (PAF) treatment reduced the capacity of leukocytes to adhere to P-selectin. Thus, the counterligands for P-selectin on EOS and PMN are similar sialylated, protease-sensitive, endo-beta-galactosidase-resistant structures, whose function and/or expression is reduced following treatment with PAF. These characteristics are clearly different than those reported for EOS and PMN ligands for E-selectin, and suggest disparate roles for P-selectin and E-selectin during EOS and PMN recruitment during inflammatory responses in vivo.

Cell Adhesion↗
PubMed1994

Differences between human eosinophils and neutrophils in the function and expression of sialic acid-containing counterligands for E-selectin.

Both neutrophils and eosinophils have been shown to bind to the inducible endothelial cell adhesion molecule E-selectin. For neutrophils, one of the reported ligands for E-selectin is the sialylated Lewis X Ag (sLe(x)). To analyze the counterligands on eosinophils for E-selectin, adhesion assays were performed in which purified leukocytes were allowed to adhere to a soluble recombinant form of the molecule immobilized on plastic plates. Eosinophils, like neutrophils, bound to immobilized E-selectin, but significantly more neutrophils than eosinophils adhered in this assay. Consistent with the greater ability of neutrophils to bind E-selectin was the observation by flow cytometry that neutrophils expressed significant levels of sLe(x) and a sialylated dimeric form of the Le(x) Ag (sialyl-dimeric Le(x), or sialyl-stage-specific embryonic Ag-1, recognized by mAb FH6), whereas the expression of these epitopes on eosinophils was extremely low or undetectable. Expression was similar on eosinophils from allergic and nonallergic donors, and was not altered on eosinophils after induction of L-selectin shedding in vitro by treatment with platelet-activating factor. For both eosinophils and neutrophils, treatment with sialidase was associated with the complete elimination of sLe(x) and sialyl-dimeric Le(x) surface expression, and abolished leukocyte adhesion to E-selectin. Another glycosidase, endo-beta-galactosidase, which specifically cleaves the beta 1-4 galactose linkage to N-acetyl-glucosamine when it exists in an extended chain form such as that found in sialyl-dimeric Le(x), significantly inhibited eosinophil and neutrophil adhesion and expression of sialyl-dimeric Le(x). Such treatment also reduced sLe(x) expression on eosinophils, while having little effect on total neutrophil sLe(x) expression. For both eosinophils and neutrophils the sialylated ligand did not appear to be a glycoprotein because pretreatment of leukocytes with several proteases had no effect on adhesion to E-selectin or on expression of sLe(x) and sialyl-dimeric Le(x). These data suggest that eosinophils, like neutrophils, use sialylated, protease-resistant structures to bind to E-selectin, although the eosinophil expresses much lower levels of these structures on its surface. A major proportion of the sLe(x)-containing E-selectin ligand on the surface of eosinophils appears to be in the form of sialyl-dimeric Le(x), whereas this represents a minor proportion on the surface of neutrophils. Based on results using endo-beta-galactosidase, it appears that these cells may rely disproportionately upon the cell surface sialyl-dimeric Le(x) to bind to E-selectin.(ABSTRACT TRUNCATED AT 400 WORDS)

Antibodies, Monoclonal↗
PubMed1989

Duty to warn.

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Acquired Immunodeficiency Syndrome↗