Biomedical subjects

A Berg

Publications and source records attributed to A Berg.

At least 145 records · Page 8Linked to original sources

PubMed1997

The race-specific elicitor AVR9 of the tomato pathogen Cladosporium fulvum: a cystine knot protein. Sequence-specific 1H NMR assignments, secondary structure and global fold of the protein.

The secondary structure and global fold of the AVR9 elicitor protein of Cladosporium fulvum has been determined by 2D NMR and distance-geometry protocols. The protein consists of three anti-parallel strands forming a rigid region of beta-sheet. On the basis of the NMR-derived parameters and distance geometry calculations, it is evident that the AVR9 protein is structurally very homologuous to carboxy peptidase inhibitor (CPI) of which the X-ray structure is known. The AVR9 protein reveals the presence of a cystine knot, which consists of a ring formed by two disulfide bridges and the interconnecting backbone through which the third disulfide bridge penetrates. This structural motif is found in several small proteins such as proteinase inhibitors, ion channel blockers and growth factors. The implications of the structural relationship between AVR9 and other biologically active proteins are discussed.

Amino Acid Sequence↗

PubMed1997

Three-dimensional structure in solution of the N-terminal lipoyl domain of the pyruvate dehydrogenase complex from Azotobacter vinelandii.

The three-dimensional structure of the N-terminal lipoyl domain of the acetyltransferase component of the pyruvate dehydrogenase complex from Azotobacter vinelandii has been determined using heteronuclear multidimensional NMR spectroscopy and dynamical simulated annealing. The structure is compared with the solution structure of the lipoyl domain of the A. vinelandii 2-oxoglutarate dehydrogenase complex. The overall fold of the two structures, described as a beta-barrel-sandwich hybrid, is very similar. This agrees well with the high similarity of NMR-derived parameters, e.g. chemical shifts, between the two lipoyl domains. The main structural differences between the two lipoyl domains occur in a solvent-exposed loop close in space to the lipoylation site. Despite their high structural similarity, these lipoyl domains show a high preference for being reductively acylated by their parent 2-oxo acid dehydrogenase. Potential residues of the lipoyl domain involved in this process of molecular recognition are discussed.

Acylation↗

PubMed1997

Mechanism of photosystem II photoinactivation and D1 protein degradation at low light: the role of back electron flow.

Light intensities that limit electron flow induce rapid degradation of the photosystem II (PSII) reaction center D1 protein. The mechanism of this phenomenon is not known. We propose that at low excitation rates back electron flow and charge recombination between the QB*- or QA*- semiquinone acceptors and the oxidized S(2,3) states of the PSII donor side may cause oxidative damage via generation of active oxygen species. Therefore, damage per photochemical event should increase with decreasing rates of PSII excitation. To test this hypothesis, the effect of the dark interval between single turnover flashes on the inactivation of water oxidation, charge separation and recombination, and the degradation of D1 protein were determined in spinach thylakoids. PSII inactivation per flash increases as the dark interval between the flashes increases, and a plateau is reached at dark intervals, allowing complete charge recombination of the QB*-/S2,3 or QA*-/S2 states (about 200 and 40 s, respectively). At these excitation rates: (i) 0.7% and 0.4% of PSII is inactivated and 0.4% and 0.2% of the D1 protein is degraded per flash, respectively, and (ii) the damage per flash is about 2 orders of magnitude higher than that induced by equal amount of energy delivered by excess continuous light. No PSII damage occurs if flashes are given in anaerobic conditions. These results demonstrate that charge recombination in active PSII is promoted by low rates of excitation and may account for a the high quantum efficiency of the rapid turnover of the D1 protein induced by limiting light.

Journal Article↗

PubMed1997

Relationship of serum ferritin concentrations with metabolic cardiovascular risk factors in men without evidence for coronary artery disease.

Elevated serum ferritin concentrations between 200 and 500 microg/l have been found to be a strong risk factor for acute myocardial infarction in Finnish men, but the reason for this association is still uncertain. In the Finnish population ferritin concentrations correlated with factors of insulin resistance syndrome. As these factors have been found to be associated with an LDL subfraction phenotype of increased concentrations of small, dense LDL particles, we hypothesized an association between ferritin and an atherogenic LDL subfraction profile, a finding which could be an explanation for the observed relationship between ferritin and atherosclerosis. Therefore we determined serum ferritin levels, metabolic cardiovascular risk factors, and the LDL subfraction phenotype in 93 healthy men without signs for infection or coronary heart disease. We found that men with moderately elevated ferritin levels (200-500 microg/l; n = 31) had a significantly worse coronary risk profile than men with lower levels ( < 200 microg/l; n = 62). Elevated ferritin concentrations were associated with significantly higher values for serum triglycerides, VLDL cholesterol, VLDL apolipoprotein B (P < 0.01), IDL cholesterol, fasting glucose (P < 0.05) and uric acid (P < 0.01), and lower levels for HDL2b and HDL2a cholesterol and apolipoprotein A-I (P < 0.05), and lipoprotein(a) (P < 0.01). Elevated ferritin levels were, however, not associated with an unfavourable LDL subfraction profile of increased concentrations of small, dense LDL particles.

Adult↗

PubMed1997

[Rationale for a specific diet from the viewpoint of sports medicine and sports orthopedics. Relation to stress reaction and regeneration].

The relation between nutrition and sport has been studied extensively during recent decades. Nevertheless, research interest was focused mainly on the role of dietary macro- and micronutrients as ergogenic aids. Today, there is increasing support for the hypothesis that the nutrient status also has relevance for the prevention and rehabilitation of systemic and muscular stress induced by intense physical exercise. The increase in muscular stress is indicated by the rise in creatine kinase and myoglobin; the systemic stress is associated with characteristic immunological and hormonal changes and an acute-phase response. During and following exercise, the course of cytokines (especially interleukin 6) and acute-phase proteins (C-reactive protein, fibrinogen) as well as cortisol levels are an indirect measure of the exercise intensity and the individual ability to cope with physical stress. It has been shown that the dietary intake and, consequently, the systemic or intracellular concentrations of minerals such as magnesium and zinc, vitamins with antioxidant capacity (vitamin E, C, E, and beta carotine), and the composition of fatty acids can be related to the exercise-induced stress response. Therefore, this review deals specifically with the impact of these nutritional components on the reduction of sports specific muscular damage and systemic stress, especially under the aspect of increased losses during and following intense physical exercise.

Antioxidants↗

PubMed1997

Relationship between changes in physical activity and plasma insulin during a 2.5-year follow-up study.

The association between changes in physical activity, body weight, and diet and fasting plasma insulin was analyzed in a 2.5-year follow-up study of 146 men aged 50 to 60 years. Physical activity was assessed by a 7-day physical activity recall interview, diet by a 4-day food record, and plasma insulin radioimmunologically. Total physical activity decreased from (mean +/- SD) 45.1 +/- 10.1 to 39.0 +/- 6.1 metabolic equivalent (MET) hours (METh).d-1 and conditioning physical activity (> 5.0 METs) from 8.0 +/- 11.2 to 2.7 +/- 5.0 METh.d-1, whereas plasma insulin increased from 8.2 +/- 5.8 to 9.2 +/- 6.7 mU.L-1 and body weight from 80.5 +/- 12.0 to 81.6 +/- 11.6 kg during the follow-up period (P < or = .001 for all). The change in conditioning physical activity correlated inversely (r = -.34, P < .001) and change in body weight positively (r = .42,P < .001) with the change in plasma insulin level. With data adjusted for the baseline insulin level, cardiovascular health status, alcohol intake, change in body weight, smoking, age, and follow-up time, the odds ratio for an increase in fasting plasma insulin was 8.9 (95% CI, 2.1 to 37.1; P = .003) for men with the greatest decrease in conditioning physical activity (< -7 METh) compared with men who reported an increase in conditioning physical activity. The same logistic regression model showed an odds ratio of 9.9 (95% CI, 2.1 to 45.4; P = .003) for the increase in plasma insulin for subjects who gained more than 3.3 kg body weight compared with subjects who lost at least 0.6 kg. Men who consumed at least 12 g.d-1 alcohol at both examinations had an odds ratio of 12.8 (95% CI, 1.7 to 94.5; P = .012) compared with nondrinkers. These data suggest that in middle-aged men, a reduction in physical activity increases the risk for increased plasma insulin independently of alcohol intake and changes in body weight.

Aging↗

PubMed1997

Differences in the concentration and composition of low-density lipoprotein subfraction particles between sedentary and trained hypercholesterolemic men.

There is evidence that a low-density lipoprotein (LDL) subfraction profile of increased concentrations of small, dense LDL particles is less common among trained than among sedentary normocholesterolemic men, but it is still uncertain whether there is a similar association in hypercholesterolemia also. Therefore, we determined the lipid and apolipoprotein concentration and composition of six LDL subfractions (density gradient ultracentrifugation) in 20 physically fit, regularly exercising (>three times per week) hypercholesterolemic men and 20 sedentary hypercholesterolemic controls. Trained (maximal oxygen consumption [VO2max], 57.3 +/- 7.4 mL/kg/min) and sedentary (VO2max, 37.5 +/- 8.8 mL/kg/min) individuals (aged 35 +/- 11 years; body mass index [BMI], 23.9 +/- 2.7 kg/m2) were matched for LDL apolipoprotein (apo) B levels (108 +/- 23 and 112 +/- 36 mg/dL, respectively). Trained subjects had significantly lower serum triglyceride (P < .05) and very-low-density lipoprotein (VLDL) cholesterol levels (P < .05) and higher high-density lipoprotein 2 (HDL2) cholesterol levels (P < .01) than sedentary controls. LDL particle distribution showed that trained individuals had significantly less small, dense LDL (d = 1.040 to 1.063 g/mL) and more large LDL (d = 1.019 to 1.037 g/mL) subfraction particles than sedentary controls, despite equal total LDL particle number. Analysis of LDL composition showed that LDL particles of hypercholesterolemic trained men had a higher free cholesterol content than LDL of untrained hypercholesterolemic men. Small, dense LDL in hypercholesterolemic trained men were richer in phospholipids than those in sedentary controls. These data demonstrate the significant influence of aerobic fitness on lipoprotein subfraction concentration and composition, thereby emphasizing the role of exercise in the treatment and risk reduction of hypercholesterolemia.

Centrifugation, Density Gradient↗

PubMed1997

Lipoprotein(a) selectively impairs receptor-mediated endothelial vasodilator function of the human coronary circulation.

OBJECTIVES: We investigated the influence of lipoprotein(a) [Lp(a)] serum levels on different endothelium-dependent vasodilator stimuli representing different mechanisms of endothelium-dependent vasodilation. BACKGROUND: Lp(a) is an independent predictor for the development and progression of coronary artery disease. Impairment of endothelium-dependent vasodilation of epicardial arteries has been shown in patients with high levels of Lp(a). METHODS: In 108 patients with angiographically normal or minimally diseased coronary vessels, vasomotor responses to acetylcholine, cold pressor testing, increased blood flow and nitroglycerin were assessed. RESULTS: Lp(a) levels > or = 30 mg/dl were associated with significant dose-dependent enhancement of the vasoconstrictor response to acetylcholine [receptor-mediated vasodilation, p = 0.002; acetylcholine 10(-6) mol/liter, -29 +/- 21% vasoconstriction with Lp(a) levels > or = 30 mg/dl vs, -5.6 +/- 25% with Lp(a) levels < 30 mg/dl]. In addition, vasoconstrictor response to cold pressor test (receptor- and flow-mediated vasodilation) was significantly enhanced in patients with Lp(a) levels > or = 30 mg/dl (-13 +/- 12% vs. 1.2 +/- 16%, p = 0.005). In contrast, strictly endothelium-dependent, but non-receptor-mediated, flow-dependent dilation and endothelium-independent dilation with nitroglycerin were not compromised. Linear regression analysis revealed an inverse relation between Lp(a) and both acetylcholine-induced (r = -0.34, p = 0.0007) and cold pressor test-induced (r = -0.44, p = 0.0001) vasodilation. By multivariate analysis, Lp(a) was a strong and independent predictor of paradoxic vasoconstriction only in response to acetylcholine and cold pressor testing. Impairment of coronary blood flow increase in patients with Lp(a) levels > or = 30 mg/dl did not reach statistical significance. CONCLUSIONS: High Lp(a) levels are associated with a selective impairment of vasodilator capacity of receptor-mediated endothelial stimuli. Impaired dilator capacity of the coronary circulation associated with elevated Lp(a) levels may contribute to the pathogenesis of myocardial ischemia in response to trigger mechanisms involving receptor-mediated stimulation such as sympathetic activation.

Acetylcholine↗

PubMed1997

Effect of exhaustive exercise stress on the cytokine response.

Fifteen athletes were investigated 24 h before, 1 h after, and 20 h after an exhaustive exercise stress test (mean duration 68 min). Testing for cytokines was done in serum, urine, and the supernatants of whole blood cell cultures, which were stimulated with lipopolysaccharide (LPS), concanavalin A (Con A), or phythaemagglutinin (PHA). Elevated levels of interleukin 6 (IL-6) and soluble IL-2 receptor (sIL-2R) were found 1 h after the run in both serum and urine samples. TNF-alpha in serum was also increased, whereas IL-2 in urine was decreased after the exercise. All other testings in serum and urine (including IFN-gamma) gave borderline or negative results. In cell cultures, the LPS-induced release of the inflammatory cytokines TNF-alpha, IL-1, and IL-6 was suppressed 1 h after exercise. Also, the Con-A-induced and LPS-induced release of IFN-gamma, and the PHA-induced release of IL-2 were suppressed 1 h after exercise. In contrast, Con-A-induced release of IL-2 was mildly increased after the run. We conclude that exercise of the intensity and duration described here causes an activation of the immune system, which is immediately counter-regulated. Twenty hours after the exercise, most of the observed changes were back to pre-exercise levels, indicating only a short duration for this suppressive counter-regulation.

Adult↗

PubMed1997

Quality assurance in plastic surgery: reduction mammaplasty.

Continuous quality assessment is essential to keep the quality of health care high as well as being a powerful educational tool. Good surgical and aesthetic results and high levels of patient satisfaction are clinical indicators of good quality plastic surgery. Breast surgery, particularly reduction mammaplasty, makes up a considerable part of plastic surgery. We have developed quality indicators of this procedure for objective evaluation of the surgical results in general, the different techniques, and the different surgeons. Consideration was taken of the patient's subjective assessment. Data were collected on the "Reduction mammaplasty quality assurance sheet." We find this form sufficient and easy to handle and we can recommend it for use by other plastic surgeons.

Adolescent↗

PubMed1997

Long-term follow up after sex reassignment surgery.

A long-term follow up of 136 patients operated on for sex reassignment was done to evaluate the surgical outcome. Social and psychological adjustments were also investigated by a questionnaire in 90 of these 136 patients. Optimal results of the operation are essential for a successful outcome. Personal and social instability before operation, unsuitable body build, and age over 30 years at operation correlated with unsatisfactory results. Adequate family and social support is important for postoperative functioning. Sex reassignment had no influence on the person's ability to work.

Adult↗

PubMed1997

Ampullosporin, a new peptaibol-type antibiotic from Sepedonium ampullosporum HKI-0053 with neuroleptic activity in mice.

Ampullosporin (I; Ac-Trp-Ala-Aib-Aib-Leu-Aib-Gln-Aib-Aib-Aib-Gln-Leu-Aib-Gln-Leuol) was isolated from the mycelium of Sepedonium ampullosporum as a new 15-membered peptaibol-type antibiotic. The structure was determined by mass spectrometric and two-dimensional NMR experiments. Ampullosporin displays narrow-spectrum antibacterial and antifungal activity, induces pigment formation by Phoma destructiva, causes hypothermia and decreased spontaneous locomotor activity in mice in dosages > 1 mg/kg.

Animals↗

PubMed1997

Essential fatty acids, immune function, and exercise.

The immunologic response to exercise comprises numerous alterations within the immune system, but how these processes are regulated is still largely unknown. Exercise-related immunological changes include signs of inflammation, such as release of inflammatory mediators, activation of various white blood cell lines and complement, and induction of acute phase proteins. Nevertheless, signs of immunosuppression, such as decreased T and B cell function or impaired cytotoxic or phagocytic activity, can also be observed. Some data suggest that essential fatty acids help regulate inflammatory processes, modulating both cytokine release and the acute phase response. Positive effects of changing dietary essential fatty acids have been demonstrated in chronic inflammatory diseases. In contrast, little is known about the contribution of fatty acids to the exercise-induced immunologic reaction. Essential fatty acids may determine alterations within the immune system following exercise. Therefore, future studies are necessary to evaluate the influence of the fatty acid composition on the inflammatory or immunosuppressive component following heavy exertion.

Acute-Phase Reaction↗

PubMed1997

2-Oxo acid dehydrogenase multienzyme complexes. The central role of the lipoyl domain.

2-Oxo acid dehydrogenase complexes are composed of multiple copies of at least three different enzymes, 2-oxo acid dehydrogenase, dihydrolipoyl acyltransferase and dihydrolipoamide dehydrogenase. The acyltransferase component harbours all properties required for multienzyme catalysis: it forms a large multimeric core, it contains binding sites for the peripheral components, the acyltransferase active site and mobile substrate carrying lipoyl domains that couple the active sites. In the past years these complexes have disclosed many of their secrets, providing currently a wealth of information on macromolecular structure, assembly and symmetry, active-site coupling, conformational mobility, substrate specificity and metabolic regulation. In this review we will discuss developments concerning the structural and mechanistic features of the 2-oxo acid dehydrogenase complexes, with special emphasis on the structure and role of the lipoyl domains in the complex.

3-Methyl-2-Oxobutanoate Dehydrogenase (Lipoamide)↗

PubMed1997

[Reducing cholesterol in cardiovascular rehabilitation--exercise versus drug therapy].

Prospective epidemiological studies have proven a close link between the improvement of the lipoprotein profile and reduction of coronary heart mortality in coronary heart disease (CHD) patients. Both, regular physical activity and pharmacological intervention are capable of improving the lipoprotein profile and may independently reduce coronary stenoses and cardiac events in CHD patients. Because of the multifactorial genesis of atherosclerosis, regular physical activity is of major importance for cardiac rehabilitation and improvements of other risk factors besides the lipoprotein profile e.g. rheology, hypercoagulability, hypertension, peripheral insulin resistance and oxidative status may be expected. The combination of life-style changes e.g. physical activity, diet and smoking cessation together with pharmacological intervention, if risk factors remain high, seems to be the best therapy for patients with CHD. A sole pharmacological intervention seems to be insufficient.

Anticholesteremic Agents↗

PubMed1997

Small, dense LDL particle concentration correlates with plasminogen activator inhibitor type-1 (PAI-1) activity.

The relation between LDL subfractions and fibrinolytic activity was studied in 150 men aged 53 to 63 years. Apolipoprotein B (apoB) concentration in the most dense LDL-5 (r = 0.39, p <0.001) and LDL-6 (r = 0.43, p <0.001) subfractions associated with plasminogen activator inhibitor type-1 (PAI-1) activity. Subjects in the highest LDL-6 apoB tertile had higher PAI-1 (24.7 vs. 13.1 AU/ml, p <0.001) and lower t-PA (0.26 vs. 0.54 IU/ml, p <0.001) activities than men in the lowest tertile. The difference in PAI-1 remained after adjusting for either triglycerides (p = 0.039) or insulin (p = 0.015) with cardiorespiratory fitness as an additional covariate, and history of cardiovascular disease and smoking as factors. In a regression analysis, plasma insulin and LDL-6 apoB, but not plasma triglycerides and body mass index, entered the model, and explained 30.6 and 3.9% of the variance in PAI-1 activity, respectively. The novel finding of the present study was the independent association between small, dense LDL particles and PAI-1 activity in middle-aged men.

Analysis of Variance↗

PubMed1996

1H NMR studies of the paramagnetic CuA center of cytochrome oxidase.

The dinuclear paramagnetic center of the soluble CuA domain of the cytochrome c oxidase from Bacillus subtilis has been studied using 1H NMR. The spectrum possesses remarkably sharp shifted resonances. Comparison with the spectrum of the CuA amicyanin variant provides the spin density distribution in the CuA site of cytochrome c oxidase. This represents the first paramagnetic NMR study of the dinuclear CuA center from the soluble domain of subunit II of cytochrome c oxidase.

Bacillus subtilis↗

PubMed1996

Solution structure of the lipoyl domain of the 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii.

The three-dimensional solution structure of the lipoyl domain of the 2-oxoglutarate dehydrogenase complex from Azotobacter vinelandii has been determined from nuclear magnetic resonance data by using distance geometry and dynamical simulated annealing refinement. The structure determination is based on a total of 580 experimentally derived distance constraints and 65 dihedral angle constraints. The solution structure is represented by an ensemble of 25 structures with an average root-mean-square deviation between the individual structures of the ensemble and the mean coordinates of 0.71 A for backbone atoms and 1.08 A for all heavy atoms. The overall fold of the lipoyl domain is that of a beta-barrel-sandwich hybrid. It consists of two almost parallel four-stranded anti-parallel beta-sheets formed around a well-defined hydrophobic core, with a central position of the single tryptophan 21. The lipoylation site, lysine 42, is found in a beta-turn at the far end of one of the sheets, and is close in space to a solvent-exposed loop comprising residues 7 to 15. The lipoyl domain displays a remarkable internal symmetry that projects one beta-sheet onto the other beta-sheet after rotation of approximately 180 degrees about a 2-fold rotational symmetry axis. There is close structural similarity between the structure of this 2-oxoglutarate dehydrogenase complex lipoyl domain and the structures of the lipoyl domains of pyruvate dehydrogenase complexes from Bacillus stearothermophilus and Escherichia coli, and conformational differences occur primarily in a solvent-exposed loop close in space to the lipoylation site. The lipoyl domain structure is discussed in relation to the process of molecular recognition of lipoyl domains by their parent 2-oxo acid dehydrogenase.

Amino Acid Sequence↗