[Clinical practice protocol update in peritoneal dialysis-2004].
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Clinical Protocols↗
Biomedical subjects
L Alegre
Publications and source records attributed to L Alegre.
Plant aging increases oxidative stress in chloroplasts.
Aging has received considerable attention in biomedicine, but little is known about the regulatory mechanisms responsible for the aging not associated with senescence in plants. This study provides new insights into the relationship between oxidative stress and plant aging, and points out chloroplasts as one of the target organelles of age-associated oxidative stress in plants. We simultaneously analyzed lipid oxidation, photosynthesis, chlorophyll content, de-epoxidation state of the xanthophyll cycle, and levels of chloroplastic antioxidant defenses such as beta-carotene and alpha-tocopherol in leaves of the same age in 1-, 3- and 7-year-old Cistus clusii Dunal plants growing under Mediterranean field conditions. Enhanced formation of malondialdehyde in leaves (2.7-fold) and chloroplasts (2.8-fold), decreased photosynthetic activity (25%), and lower chlorophyll (ca. 20%) and chloroplastic antioxidant defense levels (ca. 25%-85%) were observed in 7-year-old plants, when compared with 1- and 3-year-old plants. The differences observed, which were associated with plant aging, were only noticeable in mature nonsenescing plants (7-year-old plants). No differences were observed between pre-reproductive (1-year-old plants) and young plants (3-year-old plants). This study shows that from a certain age, oxidative stress increases progressively in chloroplasts as plants age, whereas photosynthesis is reduced. The results indicate that the oxidative stress associated with the aging in plants accumulates progressively in chloroplasts, and that the contribution of oxidative stress to aging increases as plants age.
Antioxidants↗
Daily time course of whole-shoot gas exchange rates in two drought-exposed Mediterranean shrubs.
Effects of drought on water relations, whole-shoot gas-exchange characteristics, and pigment and zeatin concentrations were investigated in the Mediterranean shrubs rosemary (Rosmarinus officinalis L.) and lavender (Lavandula stoechas L.). Two-year-old, greenhouse-grown plants were placed in a whole-shoot gas-exchange measurement system and subjected to 10 days of drought, resulting in severe water stress, and then re-watered for 5 days in order to study their recovery. Water stress resulted in a significant decline in maximum whole-shoot net CO2 assimilation rates (An) for both species that was associated with reductions in leaf area and stomatal conductance. Because shoot dark respiration rate (Rd) was less sensitive to water stress than An, shoot Rd/An ratio increased from about 15 to 95% during water stress. No major changes in chlorophyll and carotenoid concentrations of rosemary leaves were observed during the experiments, but chlorophyll and carotenoid concentrations fell significantly in water-stressed lavender leaves. Zeatin concentrations were higher in rosemary leaves than in lavender leaves during water stress. After re-watering, whole-shoot An and Rd rapidly recovered to their pre-drought rates.
Carbon Dioxide↗
Subcellular compartmentation of the diterpene carnosic acid and its derivatives in the leaves of rosemary.
The potent antioxidant properties of rosemary (Rosmarinus officinalis) extracts have been attributed to its major diterpene, carnosic acid. Carnosic acid has received considerable attention in food science and biomedicine, but little is known about its function in the plant in vivo. We recently found that highly oxidized diterpenes increase in rosemary plants exposed to drought and high light stress as a result of the antioxidant activity of carnosic acid (S. Munné-Bosch, K. Schwarz, L. Alegre [1999] Plant Physiol 121: 1047-1052). To elucidate the significance of the antioxidant function of carnosic acid in vivo we measured the relative amounts of carnosic acid and its metabolites in different compartments of rosemary leaves. Subcellular localization studies show that carnosic acid protects chloroplasts from oxidative stress in vivo by following a highly regulated compartmentation of oxidation products. Carnosic acid scavenges free radicals within the chloroplasts, giving rise to diterpene alcohols, mainly isorosmanol. This oxidation product is O-methylated within the chloroplasts, and the resulting form, 11,12-di-O-methylisorosmanol, is transferred to the plasma membrane. This appears to represent a mechanism of a way out for free radicals from chloroplasts. Carnosic acid also undergoes direct O-methylation within the chloroplasts, and its derived product, 12-O-methylcarnosic acid, accumulates in the plasma membrane. O-methylated diterpenes do not display antioxidant activity, but they may influence the stability of the plasma membrane. This study shows the relevance of the compartmentation of carnosic acid metabolism to the protection of rosemary plants from oxidative stress in vivo.
Abietanes↗
Supported discharge shortens hospital stay in patients hospitalized because of an exacerbation of COPD.
This prospective, controlled, but not formally randomized study investigates the feasibility and efficiency of an alternative to standard hospitalization for patients with exacerbated chronic obstructive pulmonary disease (COPD), based upon supported discharge with nurse supervision at home. Over a 12-month period, emergency physicians, not directly involved in the study, admitted 205 patients with exacerbated COPD to the authors' respiratory unit. Patients were included in the supported discharge group (n=105) if they voluntarily chose to participate in the programme and lived in the city of Palma de Mallorca (where adequate home support could be provided). Patients not fulfilling these criteria (mainly residents outside the city) served as controls (n=100). Inpatient treatment was standardized in all patients and included oxygen therapy, bronchodilators, antibiotics and steroids. Both groups were comparable in terms of age (mean +/- SD: 70 +/- 10 versus 65 +/- 11 yr for supported discharge and control group, respectively), severity of airflow obstruction (forced expiratory volume in one second 45 +/- 18% reference versus 46 +/- 19% ref.), comorbidity and socioeconomic status. Length of hospital stay (LOS) in the supported discharge group was shorter (5.9 +/- 2.8 versus 8.0 +/- 5.1 days, p < 0.001). After discharge, a respiratory nurse visited supported discharge patients at home during 7.3 +/- 3.8 days. Only one patient (1%) required hospital readmission during this period of time. The reduced LOS resulted in a lower utilization of hospital beds at any given point in time throughout the study period. Within the framework and potential limitations of this study, the results indicate that the supported discharge programme in Spain: 1) allows a significant reduction in the length of hospital stay of patients hospitalized because of an exacerbation of chronic obstructive pulmonary disease; 2) does not result in an inappropriately increased rate of hospital readmissions; and 3) reduces the utilization of hospital resources.
Aged↗
Changes in carotenoids, tocopherols and diterpenes during drought and recovery, and the biological significance of chlorophyll loss in Rosmarinus officinalis plants.
Two-year-old rosemary (Rosmarinus officinalis L.) plants were subjected to severe stress by exposure to prolonged drought during a Mediterranean summer. Severely stressed plants recovered completely after the autumn rainfalls although the relative water content remained below 35% for 3 months and the chlorophyll content of leaves was reduced by up to 85% during the drought. In severe stress: (i) alpha-tocopherol increased 9-fold per g dry weight and 20-fold per unit of chlorophyll; (ii) lutein and beta-carotene contents decreased on a dry-weight basis, but an 80% increase in lutein and constant levels of beta-carotene were observed on a chlorophyll basis; (iii) there were transient and sustained increases in the de-epoxidation state of the xanthophyll cycle; and (iv) the highly oxidised abietane diterpene isorosmanol increased 8-fold as a result of the oxidation of carnosic acid. With the autumn rainfalls, water status, alpha-tocopherol and violaxanthin recovered first and the levels of photosynthetic pigments and abietane diterpenes increased later. The photoprotection conferred by the xanthophyll cycle and the antioxidant function of tocopherols, lutein and diterpenes may help to avoid irreversible damage in severe drought, making possible the recovery of functional membranes after the autumn rainfalls. Besides, chlorophyll loss reduces the amount of photons absorbed by leaves, which enhances the photoprotective and antioxidant capacity of leaves per amount of photons absorbed, since the ratios of xanthophylls, alpha-tocopherol and abietane diterpenes to chlorophyll increase.
Carotenoids↗
Response of abietane diterpenes to stress in Rosmarinus officinalis L.: new insights into the function of diterpenes in plants.
Abietane diterpenes were measured in field-grown rosemary (Rosmarinus officinalis L.) plants throughout the year. Carnosic acid and carnosol, which were present in high amounts (5 and 1 mg/gDW respectively) in rosemary leaves, decreased by ca. 50% during the Mediterranean summer in response to low precipitation, high radiation and high temperature. In contrast, the highly oxidised diterpenes rosmanol, isorosmanol and dimethyl isorosmanol, which are formed from carnosic acid by enzymatic dehydrogenation and the action of activated oxygen, increased in response to such environmental constraints. Collectively, these data support the contention that abietane diterpenes from R. officinalis function as antioxidants that protect biological membranes from oxidative stress. This is especially important during the Mediterranean summer when there is low precipitation, high light and high temperature.
Abietanes↗
Enhanced Formation of alpha-Tocopherol and Highly Oxidized Abietane Diterpenes in Water-Stressed Rosemary Plants.
The lipid-soluble antioxidants alpha-tocopherol and carnosic acid were studied in field-grown rosemary (Rosmarinus officinalis L.) plants subjected to drought. During summer in the Mediterranean region, the predawn water potential decreased to -3 MPa and the relative water content to 42%, which caused a depletion of the maximum diurnal CO(2) assimilation rate by 80%. Meanwhile, the maximum efficiency of photosystem II photochemistry and the chlorophyll content of leaves remained unaltered, indicative of the absence of photooxidative damage. The concentration of alpha-tocopherol increased by 15-fold and that of carotenoids by approximately 26% in response to water stress. Enhanced formation of the highly oxidized abietane diterpenes isorosmanol (by 25%) and dimethyl isorosmanol (by 40%) was observed during the summer as result of the oxidation of carnosic acid, which decreased by 22%. The large amounts of carnosic acid, alpha-tocopherol, and carotenoids present in rosemary leaves might contribute to the prevention of oxidative damage in plants exposed to drought.
Journal Article↗
[Palmoplantar exanthema in a drug abuser].
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Adult↗