Investigation of an unexpected addition reaction that occurs when 2,3:4,5-di-O-isopropylidene-D-ribose diethyl dithioacetal is treated with mercuric oxide and mercuric chloride.
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Alkenes↗
Biomedical subjects
M Cushman
Publications and source records attributed to M Cushman.
19F NMR ligand perturbation studies on 6,7-bis(trifluoromethyl)-8-ribityllumazine-7-hydrates and the lumazine synthase complex of Bacillus subtilis. Site-directed mutagenesis changes the mechanism and the stereoselectivity of the catalyzed haloform-type reaction.
The riboflavin synthase/lumazine synthase complex of Bacillus subtilis catalyzes the last two steps in riboflavin biosynthesis. The protein comprises a capsid of 60 beta subunits with lumazine synthase activity and a core of three alpha subunits with riboflavin synthase activity. The beta subunits catalyze the formation of 6,7-dimethyl-8-ribityllumazine (3) from 5-amino-6-ribitylamino-2,4(1H,3H)-pyrimidinedione (1) and 3,4-dihydroxy-2-butanone 4-phosphate (2). Complexes of recombinant lumazine synthase (beta(60) capsids) with 6-trifluoromethyl-7-oxo-8-ribityllumazine (10) as well as 7S- or 7R-6,7-bistrifluoromethyl-8-ribityllumazine hydrate (11) were studied by (19)F NMR spectroscopy. Despite the large molecular weight of approximately 960 kDa of the protein, spectra with separated signals of free and bound ligand could be obtained. An unusually large shift difference of 8 ppm was observed between the 7-trifluoromethyl signals of free and bound ligand for epimer B of 11 and the enzyme. The signal is sensitive to the replacement of amino acid residues F22 and H88. Lumazine synthase catalyzes the elimination of the 7-trifluoromethyl group of R-diastereomer epimer A in a haloform-like reaction. The elimination reaction is also catalyzed by F22 mutants. The H88R mutant displays an opposite stereoselectivity for epimer B and a greatly enhanced reaction rate. From a model of the epimers in the active site of the protein, the main function of the side chain of F22 seems to be to keep the substrate ring in the correct position. H88 is in a position suited to act as proton acceptor in both the physiological as well as the haloform reaction. A different mechanism of the haloform-reaction is proposed in the case of the H88R mutant, initiated by hydrogen bonding of the 7-trifluorormethyl group and the guanidinium group of the arginine residue.
Bacillus subtilis↗
Serum levels of C-reactive protein are associated with obesity, weight gain, and hormone replacement therapy in healthy postmenopausal women.
The authors evaluated the cross-sectional and prospective associations between the serum concentration of C-reactive protein and measures of obesity and fat distribution, hormone replacement therapy (HRT) use, and serum sex hormones in postmenopausal women from the Healthy Women Study (Allegheny County, Pennsylvania, 1998). The authors tested the hypothesis that C-reactive protein levels would be higher among HRT users and among women with greater body mass index, waist circumference, or visceral fat. There were 207 women in the study who were > or =8 years postmenopausal (101 HRT users and 106 HRT nonusers). The median levels of C-reactive protein were 3.01 mg/liter in HRT users compared with 1.74 mg/liter in nonusers (p = 0.002). C-reactive protein levels were strongly positively correlated with measures of body size, fatness, fat distribution, and weight gain among HRT users and nonusers. C-reactive protein was also positively correlated with serum estrone levels (r(s) = 0.38) among HRT nonusers. The highest level of C-reactive protein was found among HRT users in the highest quartile of visceral fat (4.29 mg/liter) compared with women not on HRT and in the lowest quartile of visceral fat (0.96 mg/liter). The use of HRT and measures of overall body fatness are important correlates of C-reactive protein among postmenopausal women.
Adipose Tissue↗
Association between blood pressure level and the risk of myocardial infarction, stroke, and total mortality: the cardiovascular health study.
BACKGROUND: Recent reports have drawn attention to the importance of pulse pressure as a predictor of cardiovascular events. Pulse pressure is used neither by clinicians nor by guidelines to define treatable levels of blood pressure. METHODS: In the Cardiovascular Health Study, 5888 adults 65 years and older were recruited from 4 US centers. At baseline in 1989-1990, participants underwent an extensive examination, and all subsequent cardiovascular events were ascertained and classified. RESULTS: At baseline, 1961 men and 2941 women were at risk for an incident myocardial infarction or stroke. During follow-up that averaged 6.7 years, 572 subjects had a coronary event, 385 had a stroke, and 896 died. After adjustment for potential confounders, systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure were directly associated with the risk of incident myocardial infarction and stroke. Only SBP was associated with total mortality. Importantly, SBP was a better predictor of cardiovascular events than DBP or pulse pressure. In the adjusted model for myocardial infarction, a 1-SD change in SBP, DBP, and pulse pressure was associated with hazard ratios (95% confidence intervals) of 1.24 (1.15-1.35), 1.13 (1.04-1.22), and 1.21 (1.12-1.31), respectively; and adding pulse pressure or DBP to the model did not improve the fit. For stroke, the hazard ratios (95% confidence intervals) were 1.34 (1.21-1.47) with SBP, 1.29 (1.17-1.42) with DBP, and 1.21 (1.10-1.34) with pulse pressure. The association between blood pressure level and cardiovascular disease risk was generally linear; specifically, there was no evidence of a J-shaped relationship. In those with treated hypertension, the hazard ratios for the association of SBP with the risks for myocardial infarction and stroke were less pronounced than in those without treated hypertension. CONCLUSION: In this population-based study of older adults, although all measures of blood pressure were strongly and directly related to the risk of coronary and cerebrovascular events, SBP was the best single predictor of cardiovascular events.
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Correlation of anti-HIV activity with anion spacing in a series of cosalane analogues with extended polycarboxylate pharmacophores.
Cosalane and its synthetic derivatives inhibit the binding of gp120 to CD4 as well as the fusion of the viral envelope with the cell membrane. The binding of the cosalanes to CD4 is proposed to involve ionic interactions of the negatively charged carboxylates of the ligands with positively charged arginine and lysine amino acid side chains of the protein. To investigate the effect of anion spacing on anti-HIV activity in the cosalane system, a series of cosalane tetracarboxylates was synthesized in which the two proximal and two distal carboxylates are separated by 6--12 atoms. Maximum activity was observed when the proximal and distal carboxylates are separated by 8 atoms. In a series of cosalane amino acid derivatives containing glutamic acid, glycine, aspartic acid, beta-alanine, leucine, and phenylalanine residues, maximum activity was displayed by the di(glutamic acid) analogue. A hypothetical model has been devised for the binding of the cosalane di(glutamic acid) conjugate to CD4. In general, the compounds in this series are more potent against HIV-1(RF) in CEM-SS cells than they are vs HIV-1(IIIB) in MT-4 cells, and they are least potent vs HIV-2(ROD) in MT-4 cells.
Anions↗
Importance of heart failure with preserved systolic function in patients > or = 65 years of age. CHS Research Group. Cardiovascular Health Study.
Although congestive heart failure (CHF) is a common syndrome among the elderly, there is a relative paucity of population-based data, particularly regarding CHF with normal systolic left ventricular function. A total of 4,842 independent living, community-dwelling subjects aged 66 to 103 years received questionnaires on medical history, family history, personal habits, physical activity, and socioeconomic status, confirmation of pre-existing cardiovascular and cerebrovascular disease, anthropometric measurements, casual seated random-zero blood pressure, forced vital capacity and expiratory volume in 1 second, 12-lead supine electrocardiogram, fasting glucose, creatinine, plasma lipids, carotid artery wall thickness by ultrasonography, and echocardiography-Doppler examinations. Participants with at least 1 confirmed episode of CHF by Cardiovascular Health Study criteria were considered prevalent for CHF. The prevalence of CHF was 8.8% and was associated with increased age, particularly for women, in whom it increased more than twofold from age 65 to 69 years (6.6%) to age > or = 85 years (14%). In multivariate analysis, subjects with CHF were more likely to be older (odds ratio [OR] 1.2 for 5-year difference, men OR 1.1), and more often had a history of myocardial infarction (OR 7.3), atrial fibrillation (OR 3.0), diabetes mellitus (OR 2.1), renal dysfunction (OR 2.0 for creatinine < or = 1.5 mg/ dl), and chronic pulmonary disease (OR 1.8; women only). The echocardiographic correlates of CHF were increased left atrial and ventricular dimensions. Importantly, 55% of subjects with CHF had normal left ventricular systolic function and 80% had either normal or only mildly reduced systolic function. Among subjects with CHF, women had normal systolic function more frequently than men (67% vs 42%; p < 0.001). Thus, CHF is common among community-dwelling elderly. It increases with age and is usually associated with normal systolic LV function, particularly among women. The finding that a large proportion of elderly with CHF have preserved LV systolic function is important because there is a paucity of data to guide management in this dominant subset.
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Familial and genetic determinants of systemic markers of inflammation: the NHLBI family heart study.
Inflammation is thought to play a central role in the etiology and outcome of atherosclerosis. Animal studies as well as in vitro and in vivo human studies suggest that host factors modulate the magnitude and extent of inflammatory responses. We investigated familial aggregation of three systemic markers of inflammation (C-reactive protein (CRP), white blood cell count (WBC), and albumin) in a large, cross-sectional study conducted in four US communities. We found evidence of substantial heritability (35-40%) for CRP levels as well as for WBC and albumin levels. Negligible spouse correlations suggested little influence of shared household environment on these traits. The combination of sociodemographic factors (age, center, education), behavioral and lifestyle factors (cigarette smoking, alcohol intake, hormone replacement therapy), obesity and fat patterning, and prevalent diabetes explained 13-30% the interindividual variability of these traits. There was no evidence that these inflammation phenotypes were linked to a microsatellite marker in the interleukin-1 gene cluster on chromosome 2q, a region that includes several candidate genes for chronic inflammatory diseases. Our findings suggest that CRP levels, albumin levels, and WBC are determined at least partially by genetic factors. Further efforts to identify gene loci affecting these traits are warranted.
Adult↗
Frequency and predictors of stroke death in 5,888 participants in the Cardiovascular Health Study.
BACKGROUND: Few population-based studies have examined in detail issues of stroke-related deaths in elderly people. METHODS: Participants in the Cardiovascular Health Study (CHS) are 65 years of age or older, have had extensive baseline evaluations, and have been followed-up for fatal and nonfatal cardiovascular and cerebrovascular disease outcomes. Investigators adjudicated these outcomes and classified strokes by types and subtypes. RESULTS: Over 7 years, 1,310 (22.2%) of 5,888 participants died, and 455 (7.7%) experienced incident stroke. For the 5,888, stroke mortality was 3.2 per 1,000 person-years. For the 455, it was 36.1 per 1,000 person-years, with the most lethal type being hemorrhagic and the ischemic subtype being cardioembolic. After controlling for age and stroke type, the only other independent predictor of death after any stroke was poor performance on a timed walk measured before the incident stroke. Considering only ischemic stroke, the independent predictors of death were African American race and poor performance on timed walk. CONCLUSION: In CHS, death attributable to stroke is common. As in other studies, the most lethal stroke type was hemorrhagic, and ischemic stroke subtype, cardioembolic. Slow walking, possibly a measure of frailty, was associated with an increased risk of death of stroke. Finally, African Americans faced a greater risk of death than others after an ischemic stroke.
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Design, synthesis, and biological evaluation of a series of lavendustin A analogues that inhibit EGFR and Syk tyrosine kinases, as well as tubulin polymerization.
A series of N-alkylamide analogues of the lavendustin A pharmacophore were synthesized and tested for inhibition of the epidermal growth factor receptor (EGFR) protein tyrosine kinase and the nonreceptor protein tyrosine kinase Syk. Although several compounds in the series were effective inhibitors of both kinases, it seemed questionable whether their inhibitory effects on these kinases were responsible for the cytotoxic properties observed in a variety of human cancer cell cultures. Accordingly, a COMPARE analysis of the cytotoxicity profile of the most cytotoxic member of the series was performed, and the results indicated that its cytotoxicity profile was similar to that of antitubulin agents. This mechanism of action was supported by demonstrating that most compounds in the series were moderately effective as inhibitors of tubulin polymerization. This suggests that the lavendustin A analogues reported here, as well as some of the previously reported lavendustin A analogues, may be acting as cytotoxic agents by a mechanism involving the inhibition of tubulin polymerization.
Animals↗
Association between physical activity and markers of inflammation in a healthy elderly population.
Higher levels of physical activity are associated with lower risk of cardiovascular disease. There is growing evidence that the development of the atherosclerotic plaque is associated with inflammation. In this study, the authors investigated the cross-sectional association between physical activity and markers of inflammation in a healthy elderly population. Data obtained in 1989-1990 and 1992-1993 from the Cardiovascular Health Study, a cohort of 5,888 men and women aged >/=65 years, were analyzed. Concentrations of the inflammation markers-C-reactive protein, fibrinogen, Factor VIII activity, white blood cells, and albumin-were compared cross-sectionally by quartile of self-reported physical activity. Compared with persons in the lowest quartile, those in the highest quartile of physical activity had 19%, 6%, 4%, and 3% lower concentrations of C-reactive protein, white blood cells, fibrinogen, and Factor VIII activity, respectively, after adjustment for gender, the presence of cardiovascular disease, age, race, smoking, body mass index, diabetes, and hypertension. Multivariate regression models suggested that the association of higher levels of physical activity with lower levels of inflammation markers may be mediated by body mass index and glucose. There was no association between physical activity and albumin. Higher levels of physical activity were associated with lower concentrations of four out of five inflammation markers in this elderly cohort. These data suggest that increased exercise is associated with reduced inflammation. Prospective studies will be required for verification of these findings.
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Riboflavin synthase of Escherichia coli. Effect of single amino acid substitutions on reaction rate and ligand binding properties.
Conserved amino acid residues of riboflavin synthase from Escherichia coli were modified by site-directed mutagenesis. Replacement or deletion of phenylalanine 2 afforded catalytically inactive proteins. S41A and H102Q mutants had substantially reduced reaction velocities. Replacements of various other conserved polar residues had little impact on catalytic activity. (19)F NMR protein perturbation experiments using a fluorinated intermediate analog suggest that the N-terminal sequence motif MFTG is part of one of the substrate-binding sites of the protein.
Amino Acid Sequence↗
Inhibition of RANTES/CCR1-mediated chemotaxis by cosalane and related compounds.
The anti-HIV agent cosalane and several of its analogues inhibited RANTES-induced migration of human monocytes, but they did not inhibit migration induced by MIP1alpha or MIP1beta. RANTES-induced migration of single receptor CCRI-HEK transfectants was also inhibited by the cosalanes. Acetylation of the reactive amino groups of RANTES abrogated the inhibitory activity of cosalane. The data suggest that cosalane and its structural analogues may interfere with the RANTES/CCR1 interaction by binding to RANTES.
Acetylation↗
Synthesis and anti-HIV activity of cosalane analogues incorporating two dichlorodisalicylmethane pharmacophore fragments.
A new series of cosalane analogues incorporating two fragments of the dichlorodisalicylmethane pharmacophore has been synthesized. In order to identify the position for the attachment of the pharmacophore fragments to the steroid ring that results in the most potent analogues, two types of compounds were designed. In the first type, the two pharmacophore fragments were attached at C-3 and C-17 of the steroid ring by using appropriate linker units. In the second type, both pharmacophore groups were connected to C-3 of the steroid through an alkenyl chain containing an amide moiety. All of the new compounds displayed antiviral activity versus HIV-1(RF), HIV-1(IIIB), and HIV-2(ROD) in cell culture. The relative potencies of the compounds resulting from the two attachment strategies were found to depend on the viral strain as well as the cell type. Overall, the attachment of the second pharmacophore did not result in either a large gain or a large loss in anti-HIV activity, and the results are therefore consistent with the hypothesis that the two pharmacophores act independently, and one at a time, with positively charged amino acid side chains present on the surface of gp120 and CD4.
Anti-HIV Agents↗
Trousseau's syndrome treated with long-term subcutaneous lepirudin (case report and review of the literature).
We report here a case of recurrent venous and arterial thromboembolism, Trousseau's syndrome, in a cancer patient who developed heparin-induced thrombocytopenia. She was treated with lepirudin and after establishing the patient-specific half-life for subcutaneous lepirudin, she was successfully maintained on this therapy for more than eight months. To our knowledge this case represents the longest reported use of subcutaneous lepirudin.
Anticoagulants↗
The association of vitamin K status with warfarin sensitivity at the onset of treatment.
We investigated the association of vitamin K status with warfarin sensitivity among 40 orthopaedic patients beginning perioperative algorithm-dosed warfarin. Baseline vitamin K status was assessed using plasma vitamin K-1 and vitamin K-1 2,3 epoxide concentrations, and a questionnaire-based estimation of usual vitamin K intake. Warfarin sensitivity was assessed as the increase in the International Normalized Ratio (INR) after two doses of 5 mg of warfarin and as the 4-d accumulation of under-gamma-carboxylated prothrombin (PIVKA-II), adjusted for warfarin dose requirement. Multivariate models were used to assess vitamin K variables as predictors of warfarin sensitivity. The mean INR increase was 0.53 U and the mean PIVKA-II increase was 771 ng/ml/mg warfarin. Demographic factors were not associated with warfarin response. For each 1 standard deviation (SD) lower value of plasma vitamin K-1, but not the other vitamin K variables, the INR rose 0.24 U (P < or = 0.01). A higher usual vitamin K intake and plasma vitamin K-1, and lower plasma vitamin K-1 2,3 epoxide, were all associated with a lower PIVKA-II increase over 4 d. Respective differences in PIVKA-II accumulation per SD increase of each variable were -165, -218 and 236 ng/ml/mg warfarin (all P < or = 0.05). We concluded that dietary and biochemical measures of vitamin K status were associated with early warfarin sensitivity.
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Post-menopausal hormone therapy and concentrations of protein C and antithrombin in elderly women.
The effects of post-menopausal hormone therapy (HRT) on blood coagulation in elderly women are not well defined. We studied associations of HRT use with levels of natural anticoagulant proteins in a cross-sectional study of 3393 women > or = 65 years of age participating in the Cardiovascular Health Study. Protein C antigen and antithrombin were measured in all users (n = 230 unopposed oestrogen; 60 oestrogen/progestin) and a comparison group of 196 age- and race-matched non-users. Compared with non-users, oestrogen use was associated with higher protein C (4.80 vs. 4.30 microg/ml, P < 0.01). Results were similar for oestrogen/progestin (P > 0.05). In both user groups, antithrombin was lower than in non-users (109% for each vs. 115% in non-users, P < 0.001). Adjustment for factors related to prescription of HRT and to anticoagulant protein levels had little impact on the results. For antithrombin, associations with HRT were larger for thinner Caucasian women and black women. Venous thrombosis from HRT may be mediated partly by alterations in antithrombin, but not protein C concentrations. This study extends previous observations to older women, the group at highest risk of venous thromboembolism. Studies of HRT-induced alterations in anticoagulant function in relation to the occurrence of thrombosis with HRT are required.
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Domain structure of riboflavin synthase.
Riboflavin synthase of Escherichia coli is a homotrimer of 23.4 kDa subunits catalyzing the formation of the carbocyclic ring of the vitamin, riboflavin, by dismutation of 6,7-dimethyl-8-ribityllumazine. Intramolecular sequence similarity suggested that each subunit folds into two topologically similar domains. In order to test this hypothesis, sequence segments comprising amino-acid residues 1-97 or 101-213 were expressed in recombinant E. coli strains. The recombinant N-terminal domain forms a homodimer that can bind riboflavin, 6,7-dimethyl-8-ribityllumazine and trifluoromethyl-substituted 8-ribityllumazine derivatives as shown by absorbance, circular dichroism, and NMR spectroscopy. Most notably, the recombinant domain dimer displays the same diastereoselectivity for ligands as the full length protein. The minimum N-terminal peptide segment required for ligand binding comprises amino-acid residues 1-87. The recombinant C-terminal domain comprising amino-acid residues 101-213 is relatively unstable and was shown not to bind riboflavin but to differentiate between certain diastereomeric trifluoromethyl-8-ribityllumazine derivatives. The data show that a single domain comprises the intact binding site for one substrate molecule. The enzyme-catalyzed dismutation requires two substrate molecules to be bound in close proximity, and each active site of the enzyme appears to be located at the interface of an N-terminal and C-terminal domain.
Amino Acid Sequence↗
Factors associated with healthy aging: the cardiovascular health study.
OBJECTIVES: To identify factors associated with remaining healthy in older adults. DESIGN: Longitudinal cohort study. SETTING: Data were collected at the four Cardiovascular Health Study field centers. PARTICIPANTS: 5,888 participants age 65 years and older in the Cardiovascular Health Study. MEASUREMENTS: Presence of chronic disease was assessed at baseline and over a maximum 7-year follow-up period. Participants who were free of chronic disease (no cardiovascular disease (CVD), chronic obstructive pulmonary disease, or self-reported cancer, except nonmelanoma skin cancer) at the baseline examination were then monitored for the onset of incident cancer, cardiovascular disease, and fatal outcomes. RESULTS: A high proportion of these older adults was healthy at the initial examination and remained healthy over the follow-up period. Numerous behavioral factors were associated with continued health, including physical activity, refraining from cigarette smoking, wine consumption (women), higher educational status, and lower waist circumference. A number of CVD risk factors and subclinical disease measures were associated with continued health, including higher high-density lipoprotein (HDL) cholesterol, lack of diabetes, thinner common carotid intimal nmedial thickness, lower blood pressure, lower C-reactive protein, and higher ankle-arm blood pressure ratio. Among the behavioral factors, exercise, not smoking, and not taking aspirin remained significant predictors of health even after controlling for CVD risk factors and subclinical disease in older adults. CONCLUSIONS: These data suggest that a number of modifiable behavioral factors (physical activity, smoking, and obesity) and cardiovascular risk factors (diabetes, HDL cholesterol, and blood pressure) are associated with maintenance of good health in older adults.
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