Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 60
Filtrar
Mais filtros

Base de dados
Tipo de documento
Intervalo de ano de publicação
1.
Acta Radiol ; 59(11): 1277-1284, 2018 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-29490465

RESUMO

Background During transarterial chemoembolization (TACE), cone-beam computed tomography (CBCT) can be used for tumor and feeding vessel detection as well as postembolization CT imaging. However, there will be additional radiation exposure from CBCT. Purpose To evaluate the additional dose raised through CBCT-assisted guidance in comparison to TACE procedures guided with pulsed digital subtraction angiography (DSA) alone. Material and Methods In 70 of 140 consecutive patients undergoing TACE for liver cancer, CBCT was used to facilitate the TACE. Cumulative dose area product (DAP), cumulative kerma(air), DAP values of DSA, total and cine specific fluoroscopy times (FT) of 1375 DSA runs, and DAP of 91 CBCTs were recorded and analyzed using Spearman's correlation, Mann-Whitney U-test, and Kruskal-Wallis test. P values < 0.05 were considered significant. Results Additional CBCT increased DAP by 2% ( P = 0.737), kerma(air) by 24.6% ( P = 0.206), and FT by 0.02% ( P = 0.453). Subgroup analysis revealed that postembolization CBCT for detection of ethiodized oil deposits added more DAP to the procedure. Performing CBCT-assisted TACE, DSA until first CBCT contributed about 38% to the total DAP. Guidance CBCT acquisitions conduced to 6% of the procedure's DAP. Additional DSA for guidance after CBCT acquisition required approximately 46% of the mean DAP. The last DSA run for documentation purposes contributed about 10% of the DAP. Conclusion CBCT adds radiation exposure in TACE. However, the capability of CBCT to detect vessels and overlay in real-time during fluoroscopy facilitates TACE with resultant reduction of DAPs up to 46%.


Assuntos
Carcinoma Hepatocelular/terapia , Quimioembolização Terapêutica/métodos , Tomografia Computadorizada de Feixe Cônico/métodos , Neoplasias Hepáticas/terapia , Exposição à Radiação/estatística & dados numéricos , Radiografia Intervencionista/métodos , Idoso , Angiografia Digital/métodos , Carcinoma Hepatocelular/diagnóstico por imagem , Feminino , Humanos , Fígado/diagnóstico por imagem , Neoplasias Hepáticas/diagnóstico por imagem , Masculino , Doses de Radiação , Estudos Retrospectivos
2.
Gynecol Oncol ; 146(2): 279-284, 2017 08.
Artigo em Inglês | MEDLINE | ID: mdl-28528917

RESUMO

PURPOSE: The prognosis is poor for patients with recurrent, platinum-resistant epithelial ovarian cancer (EOC). Evidence suggests that antiangiogenic treatment modalities could play a major role in EOC. A combined therapy consisting of the investigational oral antiangiogenic agent pazopanib and metronomic oral cyclophosphamide may offer a well-tolerable treatment option to patients with recurrent, previously treated EOC. PATIENTS AND METHODS: This study was designed as a multicenter phase I trial evaluating the optimal dose as well as activity and tolerability of pazopanib with metronomic cyclophosphamide in the treatment of patients with recurrent, platinum-resistant, previously treated ovarian, peritoneal, or fallopian tube cancer. Here, 50mg cyclophosphamide were combined with 400 to 800mg pazopanib daily. RESULTS: Sixteen patients were treated; mean age was 66years. At dose levels (DL) I and II, one instance of dose-limiting toxicity (DLT) was seen in one of 6 patients. At DL III, two of four patients showed a DLT, leading to a maximum tolerated dose (MTD) of 600mg pazopanib daily. Median number of administered cycles was 6 (2-13), with three patients being treated for at least 13months. Median progression-free survival (PFS) and overall survival (OS) were 8.35months and 24.95months, respectively. 155 adverse events (AE) occurred, most frequently elevation of liver enzymes, leukopenia, diarrhea and fatigue. Altogether, five serious adverse events (SAE) developed in four patients. CONCLUSION: Pazopanib 600mg daily p.o. and metronomic cyclophosphamide 50mg daily p.o. is a feasible regimen for patients with recurrent platinum-resistant EOC and showed promising activity in this previously treated patient population. TRIAL REGISTRATION: Clin.trial.gov registry no.: NCT01238770.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/uso terapêutico , Recidiva Local de Neoplasia/tratamento farmacológico , Neoplasias Císticas, Mucinosas e Serosas/tratamento farmacológico , Neoplasias Epiteliais e Glandulares/tratamento farmacológico , Neoplasias Ovarianas/tratamento farmacológico , Idoso , Carcinoma Epitelial do Ovário , Ciclofosfamida/administração & dosagem , Diarreia/induzido quimicamente , Intervalo Livre de Doença , Resistencia a Medicamentos Antineoplásicos , Fadiga/induzido quimicamente , Feminino , Humanos , Indazóis , Leucopenia/induzido quimicamente , Testes de Função Hepática , Dose Máxima Tolerável , Pessoa de Meia-Idade , Gradação de Tumores , Recidiva Local de Neoplasia/patologia , Neoplasias Císticas, Mucinosas e Serosas/patologia , Neoplasias Epiteliais e Glandulares/patologia , Neoplasias Ovarianas/patologia , Compostos de Platina , Pirimidinas/administração & dosagem , Sulfonamidas/administração & dosagem
3.
Ann Oncol ; 23(9): 2271-2277, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22383680

RESUMO

BACKGROUND: The presence of disseminated tumor cells (DTCs) in bone marrow of patients with early breast cancer (EBC) has been correlated with increased risk of metastatic disease or locoregional relapse. Zoledronic acid (ZOL) treatment has reduced DTCs in the bone marrow of patients with EBC in several studies. This controlled study sought to confirm these observations. PATIENTS AND METHODS: Patients with EBC and DTC-positive bone marrow were randomized (N = 96) to treatment with ZOL plus adjuvant systemic therapy or adjuvant systemic therapy alone. The change in DTC numbers at 12 months versus baseline was measured. RESULTS: DTC-positive patients treated with ZOL were more likely to become DTC-negative after 12 months of treatment compared with the controls (67% versus 35%; P = 0.009). At 12 months, DTC counts decreased to a mean of 0.5 ± 0.8 DTCs in the ZOL group and to 0.9 ± 0.8 DTCs in the control group. In addition, ZOL was generally well tolerated. CONCLUSIONS: Treatment with ZOL improves elimination of DTCs. Further studies are needed to determine whether the reduction in DTCs by ZOL provides clinical benefit.


Assuntos
Antineoplásicos/uso terapêutico , Células da Medula Óssea/patologia , Neoplasias Ósseas/prevenção & controle , Neoplasias da Mama/tratamento farmacológico , Difosfonatos/uso terapêutico , Imidazóis/uso terapêutico , Recidiva Local de Neoplasia/prevenção & controle , Células Neoplásicas Circulantes/patologia , Adulto , Idoso , Antineoplásicos/efeitos adversos , Antineoplásicos/farmacologia , Artralgia/induzido quimicamente , Neoplasias Ósseas/secundário , Neoplasias da Mama/patologia , Difosfonatos/efeitos adversos , Difosfonatos/farmacologia , Feminino , Humanos , Imidazóis/efeitos adversos , Imidazóis/farmacologia , Pessoa de Meia-Idade , Resultado do Tratamento , Ácido Zoledrônico
5.
J Clin Oncol ; 19(16): 3669-74, 2001 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-11504748

RESUMO

PURPOSE: To evaluate the detection of epithelial cells in bone marrow of breast cancer patients as an indicator of metastatic disease. PATIENTS AND METHODS: Between 1989 and 1994, bone marrow biopsies were performed on 393 breast cancer patients during primary surgery. Specimens were stained immunocytochemically for epithelial cells expressing cytokeratins or the epithelial membrane antigen. The long-term outcomes of these patients were analyzed in this study. RESULTS: In 166 of 393 patients, epithelial cells were found in bone marrow (BM) aspirates. These patients were designated BM+. The rate of tumor recurrence or cancer-related death was significantly higher in BM+ patients than in BM- patients. Multivariate analysis using the Cox regression model revealed BM status as a prognostic parameter independent of tumor size and axillary lymph node status. However, tumor size and axillary lymph node status were clearly superior prognostic parameters. CONCLUSION: Disseminated epithelial cells in BM are associated with poor clinical outcome in breast cancer patients. However, the presence of these cells is not a sufficient parameter to predict growing metastases in the majority of patients, suggesting that epithelial cells in the BM of breast cancer patients at the time of surgery have limited metastatic potential. The role of these cells needs to be further evaluated.


Assuntos
Exame de Medula Óssea/normas , Medula Óssea/patologia , Neoplasias da Mama/patologia , Carcinoma Ductal de Mama/secundário , Células Epiteliais/citologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias da Mama/mortalidade , Neoplasias da Mama/cirurgia , Carcinoma Ductal de Mama/mortalidade , Intervalo Livre de Doença , Feminino , Alemanha/epidemiologia , Humanos , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Modelos de Riscos Proporcionais , Análise de Sobrevida
6.
New Phytol ; 160(1): 209-223, 2003 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33873535

RESUMO

• Whereas mycorrhizal fungi are acknowledged to be the sources of nitrogen (N) and carbon (C) in achlorophyllous (myco-heterotrophic) orchids, the sources of these elements in autotrophic orchids are unknown. We have determined the stable isotope abundance of N and C to quantify their gain from different sources in these two functional groups and in non-orchids of distinctive mycorrhizal types. • Leaves of each plant were collected from four forest and four grassland sites in Europe. The N and C isotope abundance, and total N concentrations of their tissues and of associated soils were determined. • Myco-heterotrophic orchids were significantly more enriched in 15 N (ɛMHO-R = 11.5‰) and 13 C (ɛMHO-R = 8.4‰) than co-occurring non-orchids. δ15 N and δ13 C signatures of autotrophic orchids ranged from values typical of non-orchids to those more representative of myco-heterotrophic orchids. • Utilization of fungi-derived N and C probably explains the relative 15 N and 13 C enrichment in the myco-heterotrophs. A linear two-source isotopic mixing model was used to estimate N and C gain of autotrophic orchids from their fungal associates. Of the putatively autotrophic species, Cephalanthera damasonium obtained the most N and C by the fungal route, but several other species also fell into the partially myco-heterotrophic category.

7.
New Phytol ; 164(2): 383-388, 2004 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-33873558

RESUMO

• While it is accepted that many ectomycorrhizal fungi can assimilate organic substrates and facilitate transfer of their elemental components to plants, the fate of the carbon contained in these materials remains uncertain. Here we investigate the compartmentation of carbon and nitrogen in ectomycorrhizal seedlings of Pinus sylvestris fed with double-labelled (15 N and 13 C) glycine as their sole N source. • Using isotope ratio mass spectrometry, the quantities of N and C derived from this glycine were determined in sequentially harvested samples of mycorrhizas, roots and shoots. • Whereas considerable quantities of 15 N were observed in the mycorrhizal tips, roots and shoots, comparable amounts of 13 C were observed only in mycorrhizal tips and roots. • It is clearly important to resolve the role of compound specificity as a factor determining the extent of amino-acid C transfer from roots to shoots. However, from the standpoint of the C budget of the whole plant, wherever heterotrophically acquired C is available as an energy source it will reduce demands on photosynthetically fixed sources of the element.

8.
Int J Oncol ; 16(2): 321-5, 2000 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10639576

RESUMO

Cisplatin has been widely used as a chemotherapeutic agent to treat different types of tumors. However, its use is limited by the ability of the tumor cells to develop cisplatin-resistance. The molecular lesion that produces cisplatin-resistance is poorly understood. In this report, we show that cisplatin activates a robust apoptotic pathway involving the activation of JNK and p38MAPK whereas it fails to elicit such a response in cisplatin-resistant 2008/C13 cells. Analysis of the defective apoptotic pathway in 2008/C13 cells indicates that these cells are deficient in the proteolytic activation of MEKK1 by caspase-3. The blunted activity of caspase-3 appears to be closely related to the increased levels of the anti-apoptotic protein Bcl-xL seen in the resistant cells. These studies, for the first time, demonstrate that inadequate caspase-3 processing and MEKK1 activation can lead to a drug-resistant phenotype.


Assuntos
Adenocarcinoma/metabolismo , Antineoplásicos/farmacologia , Cisplatino/farmacologia , MAP Quinase Quinase Quinase 1 , Neoplasias Ovarianas/metabolismo , Proteínas Serina-Treonina Quinases/efeitos dos fármacos , Proteínas Quinases Dependentes de Cálcio-Calmodulina/efeitos dos fármacos , Proteínas Quinases Dependentes de Cálcio-Calmodulina/metabolismo , Resistencia a Medicamentos Antineoplásicos/fisiologia , Feminino , Humanos , Proteínas Quinases JNK Ativadas por Mitógeno , Proteínas Quinases Ativadas por Mitógeno/efeitos dos fármacos , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Células Tumorais Cultivadas/efeitos dos fármacos , Proteínas Quinases p38 Ativadas por Mitógeno
9.
Anticancer Res ; 18(2A): 1191-5, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9615787

RESUMO

IGF-1 and 2 are thought to be important growth factors for breast cancer. However, gene expression of IGFs or IGF receptors in breast cancer tissues, and especially in metastatic breast cancer cells, is not well known. Expression of mRNA encoding for IGF-1, IGF-2, IGF-receptor 1 and 2, IGF binding proteins- 1 to -6, insulin receptor and insulin was determined in the NIH MCF-7 breast cancer cell line, in specimens from breast cancer tissues, and in 6 primary breast cancer cell cultures obtained from metastatic breast cancer, using rT-PCR technique. Specific mRNA sequences encoding for IGF-receptor 1 and 2, IGFBP-2, -4 and insulin receptor were identified in all cell cultures and most of the tissue specimens. Though in most of the tissues additional expression of IGF-1 and IGF-2 was detected, there was no mRNA encoding for these proteins in MCF-7 cell cultures as well as in the primary cell cultures of metastatic breast cancers. In none of our specimens mRNA encoding for IGFBP-1, -3, -5, -6 and insulin was detectable. IGF-receptor expression in cancer tissues and metastatic breast cancer cells supports the hypothesis that IGFs increase tumor cell proliferation in vivo. Expression of IGF-1 and IGF-2 in tumor tissues but not in cancer cell cultures indicates an IGF expression located predominantly in stromal parts of cancer tissues.


Assuntos
Neoplasias da Mama/metabolismo , Proteínas de Ligação a Fator de Crescimento Semelhante a Insulina/genética , RNA Mensageiro/análise , Receptor IGF Tipo 1/genética , Receptor IGF Tipo 2/genética , Somatomedinas/genética , Feminino , Humanos , Metástase Neoplásica , Células Tumorais Cultivadas
10.
Anticancer Res ; 17(4A): 2731-4, 1997.
Artigo em Inglês | MEDLINE | ID: mdl-9252706

RESUMO

Tumor markers CEA, CA19-9, CA15-3, CA125, AFP, beta-HCG, SCC were measured quantitatively in serum, tumor tissue and healthy colonic mucosa of patients with colorectal cancer. We wanted to investigate whether there is a difference in concentration between patients with and without recurrence of cancer. During the follow-up period 14 of 38 patients showed tumor recurrence. Patients with cancer relapse had higher preoperative serum levels of CEA and CA19-9 and significantly higher concentrations in their histologically normal colonic mucosa of CEA, CA19-9, SCC and lower ones of CA15-3. The highest values of CEA, CA19-9, and SCC occurred in the mucosa of patients developing local cancer recurrence. Marker concentrations in tumor tissues themselves did not differ between patients with or without tumor relapse. Though this should be confirmed in a larger number of cases we conclude from these results that tumor marker concentrations in healthy colonic mucosa of patients with colorectal cancer may become valuable indicators of the risk of tumor recurrence.


Assuntos
Biomarcadores Tumorais , Carcinoma/diagnóstico , Neoplasias Colorretais/diagnóstico , Serpinas , Antígenos de Neoplasias/análise , Antígenos Glicosídicos Associados a Tumores/análise , Antígeno CA-19-9/análise , Antígeno Carcinoembrionário/análise , Carcinoma/imunologia , Neoplasias Colorretais/imunologia , Seguimentos , Humanos , Mucosa Intestinal/química , Prognóstico , Recidiva , alfa-Fetoproteínas/análise
11.
Anticancer Res ; 17(4B): 2939-42, 1997.
Artigo em Inglês | MEDLINE | ID: mdl-9329569

RESUMO

Tumor markers CEA, CA19-9, CA15-3, CA125, AFP, beta-HCG, SCC were measured quantitatively in the serum, tumor tissue and healthy colonic mucosa of patients with colorectal cancer. We wanted to investigated whether there is a difference in concentration between patients with and without recurrence of cancer. During the follow-up period 14 of 38 patients showed tumor recurrence. The patients with cancer relapse had higher preoperative serum levels of CEA and CA19-9 and in the histologically normal colonic mucosa they had higher concentrations of CEA, CA19-9, SCC and low CA15-3. The highest values of CEA, CA19-9, and SCC occurred in the mucosa of patients developing local cancer recurrence. Marker concentrations in tumor tissues themselves did not differ between patients with or without tumor relapse. Though confirmation in a larger number of cases is needed we conclude from these results that tumor marker concentrations in the healthy colonic mucosa of patients with colorectal cancer may become valuable indicators of the risk of tumor recurrence.


Assuntos
Biomarcadores Tumorais/análise , Neoplasias Colorretais/química , Antígeno CA-19-9/análise , Antígeno Carcinoembrionário/análise , Colo/química , Humanos , Mucina-1/análise , Recidiva Local de Neoplasia , Prognóstico
12.
Anticancer Res ; 19(4A): 2509-11, 1999.
Artigo em Inglês | MEDLINE | ID: mdl-10470184

RESUMO

Soluble interleukin-2 receptors (sIL-2R) are measurable in the sera of patients with ovarian cancer and several other benign and malignant diseases. However, the function of these sIL-2R is still unclear. Since high levels of sIL-2R are thought to be an indicator of an activated immune system we investigated the correlation of sIL-2R concentration and prognosis of ovarian cancer patients. sIL-2R measurement was performed on the preoperative sera of 130 patients with benign, and 119 patients with malignant ovarian tumors. The IMMULITE sIL-2R assay by DPC Biermann, Bad Nauheim, Germany was used. In ovarian cancer patients sIL-2R concentrations were significantly higher than in those with benign tumors. By defining the 95th percentile of the sIL-2R concentration distribution in patients with benign diseases as the cut-off (1200 U/ml) 35% of the ovarian cancer patients had elevated concentrations. Concentrations of sIL-2R increased with FIGO stage. FIGO-III patients with highly elevated sIL-2R concentrations tended to have better prognosis than those with sIL-2R levels within normal range in contrast to FIGO IV patients. Since sIL-2R concentrations indicate an immunological activation in ovarian cancer patients our data give hints of the possible role of sIL-2R in the assessment of the risk of recurrence in ovarian cancer patients.


Assuntos
Biomarcadores Tumorais/sangue , Neoplasias Ovarianas/diagnóstico , Receptores de Interleucina-2/sangue , Adenofibroma/diagnóstico , Adenofibroma/mortalidade , Adenofibroma/patologia , Adenofibroma/cirurgia , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Cistadenoma/diagnóstico , Cistadenoma/mortalidade , Cistadenoma/patologia , Cistadenoma/cirurgia , Cisto Dermoide/diagnóstico , Cisto Dermoide/mortalidade , Cisto Dermoide/patologia , Cisto Dermoide/cirurgia , Feminino , Humanos , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Cistos Ovarianos/diagnóstico , Cistos Ovarianos/mortalidade , Cistos Ovarianos/patologia , Cistos Ovarianos/cirurgia , Neoplasias Ovarianas/mortalidade , Neoplasias Ovarianas/patologia , Neoplasias Ovarianas/cirurgia , Prognóstico , Kit de Reagentes para Diagnóstico , Reprodutibilidade dos Testes , Análise de Sobrevida , Fatores de Tempo
13.
Anticancer Res ; 19(4A): 2535-6, 1999.
Artigo em Inglês | MEDLINE | ID: mdl-10470190

RESUMO

Measurement of CA125 is well established in the diagnosis and follow-up of ovarian cancer. CA125 determination is usually performed with the monoclonal antibodies OC125 and M11. For the IMMULITE OM-MA chemoluminsence assay (DPC Biermann, Bad Nauheim, Germany) the monoclonal antibody OV185 is used. We analysed CA125 serum concentrations of patients with benign and malignant ovarian tumors with the IMMULITE OM-MA assay by defining a cut-off at 90% specificity level. Sera of 130 patients with benign and 119 patients with malignant ovarian tumors at different FIGO stages were analysed. By calculating a cut-off of 46 U/ml, in 87 ovarian cancer patients, elevated CA125 concentrations were detected (78% sensitivity). There were no significant differences between CA125 concentrations of tumors of different histological type. The measurement of CA125 by IMMULITE OM-MA is a simple and sensitive procedure.


Assuntos
Antígeno Ca-125/sangue , Neoplasias Ovarianas/diagnóstico , Adulto , Idoso , Idoso de 80 Anos ou mais , Anticorpos Monoclonais , Biomarcadores Tumorais/sangue , Diagnóstico Diferencial , Feminino , Humanos , Imunoensaio/métodos , Medições Luminescentes , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Neoplasias Ovarianas/sangue , Neoplasias Ovarianas/patologia , Kit de Reagentes para Diagnóstico , Sensibilidade e Especificidade
14.
Anticancer Res ; 24(6): 4205-10, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15739264

RESUMO

BACKGROUND: Serum HER2 testing allows the determination of the real-time HER2 status of breast cancer patients. The aim of this investigation was to study (i) whether changes of serum HER2 status occur during the clinical course of breast cancer and (ii) to evaluate the prognostic significance of serum HER2 status, at the time of first diagnosis of primary breast cancer and at the onset of metastatic disease, for survival after relapse (SAR). MATERIALS AND METHODS: HER2 serum levels were retrospectively measured in 152 breast cancer patients at the time of first diagnosis of breast cancer and at the onset of metastatic disease by enzyme immunoassay. RESULTS: Twenty-seven out of 152 (18%) patients had elevated HER2 serum levels at the time of first diagnosis of breast cancer. In contrast, 56 out of 152 (37%) patients showed elevated serum HER2 levels when metastases were diagnosed. A change of serum HER2 status during clinical course was observed in 43 out of 152 (28%) patients. Serum HER2 status at the time of first diagnosis of breast cancer had no impact on survival after relapse (SAR) (p = 0.4). However, the median SAR for serum HER2-positive patients at the onset of metastatic disease was significantly shorter (8 months, 95% CI: 3-12) compared to patients serum HER2-negative at this time (18 months, 95% CI: 14-22) (p < 0.01). CONCLUSION: Serum HER2 status can change during the course of disease. Therefore, the serum HER2 status should be re-evaluated at the time of diagnosis of metastatic disease to optimize treatment decisions.


Assuntos
Neoplasias da Mama/sangue , Receptor ErbB-2/sangue , Neoplasias da Mama/patologia , Feminino , Humanos , Metástase Neoplásica , Estudos Retrospectivos
15.
Oecologia ; 75(3): 371-385, 1988 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28312685

RESUMO

48 plant species of the families Asteraceae, Chenopodiaceae, Ericaceae, Fabaceae, Lamiaceae, Polygonaceae and Urticaceae were investigated in 14 natural habitats of Central Europe having different nitrate supplies, with respect to their nitrate content, nitrate reductase activity (NRA) and organic nitrogen content. Plants that were flowering were selected where possible for analysis. The plants were subdivided into flowers, laminae, petioles+shoot axes and below-ground organs. Each organ was analyzed separately. Differences among species were found for the three variables investigated. Apart from the Fabaceae, which had particularly high concentrations of organic N, these differences reflect mainly the ecological behaviour, i.e. high nitrate and organic N contents and NRA values per g dry weight were found in species on sites rich in nitrate, and vice versa. Nitrate content, NRA and organic N content were correlated with "nitrogen figures" of Central European vascular plants defined by Ellenberg (1979). By use of regression equations this correlation was tested with species from other systematic groups. Some species were attributed with calculated "N figures" for the first time.

16.
Oecologia ; 63(1): 136-142, 1984 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28311176

RESUMO

With Rumex obtusifolius L., the influence of some environmental conditions on nitrate uptake and reduction were investigated. Nitrate concentrations of plant material were determined by HPLC, the activity of nitrate reductase by an "in vivo" test. As optimal incubation medium, a buffer containing 0.04 M KNO3; 0.25 M KH2PO4; 1.5% propanol (v/v); pH 8.0 was found. Vacuum infiltration caused an increase of enzyme activity of up to 40%.High nitrate concentrations were found in roots and leaf petioles. Nitrate reductase activity of these organs, however, was low. On the other hand, the highest nitrate reductase activity was observed in leaf laminae, which contained lowest nitrate concentrations.In leaves, nitrate content and nitrate reductase activity exhibited inverse diurnal fluctuations. During darkness, decreasing activities of the enzyme were followed by increasing nitrate concentrations, while during light the contrary was true. In petioles diurnal fluctuations in nitrate content were observed, too. No significant correlations with illumination, however, could be found.Our results prove that Rumex obtusifolius is characterized by an intensive nitrate turnover. Theoretically, internal nitrate content of the plant would be exhausted within a few hours, if a supply via the roots would be excluded.

17.
Oecologia ; 63(3): 380-385, 1984 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28311215

RESUMO

The aim of this work was to investigate the effect of nitrogen starvation and subsequent fentilization with nitrate or ammonium on nitrate content and nitrate reductase activity of Rumex obtusifolius L. under natural conditions.When plants were transplanted to nitrate-poor media, endogenous nitrate was reduced within a few days. In parallel, nitrage reductase activities dropped to about 25% of the initial values. As a consequence of nitrate fertilization (1; 10 or 100 mmol KNO3/l substrate), endogenous nitrate content of the plant abruptly increased within one day. In extreme cases, nitrate concentrations of up to 10% of plant dry weight could be observed without being lethal. High external nitrate concentrations caused an inhibition of nitrate reductase within the leaves, while low external concentrations provoked an increase in the enzyme activity of about 450% within one day. Ammonium fertilization (5 mmol (NH4)2SO4/l substrate) also caused an increase in nitrate reductase activity and nitrate content within leaf blades. This observation indicates a rapid nitrification of ammonium in the substrate. When plants were fertilized with ammonium plus nitrate (2.5 mmol (NH4)2SO4+ 5 mmol KNO3/l substrate), an extremely high and long term increase in nitrate reduction could be observed. Due to an intensive enzymatic nitrate turnover, the nitrate content of leaf blades then remained relatively low. Our observations do not point to an inhibition of nitrate reductase activity in leaves of Rumex obtusifolius by ammonium. Despite temporarily high endogenous nitrate concentrations, Rumex obtusifolius may not be termed as a "nitrate storage" plant, since the accumulation of nitrate is a short term process only.

18.
Oecologia ; 87(2): 198-207, 1991 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28313836

RESUMO

Natural carbon and nitrogen isotope ratios were measured in different compartments (needles and twigs of different ages and crown positions, litter, understorey vegetation, roots and soils of different horizons) on 5 plots of a healthy and on 8 plots of a declining Norway spruce (Picea abies (L.) Karst.) forest in the Fichtelgebirge (NE Bavaria, Germany), which has recently been described in detail (Oren et al. 1988a; Schulze et al. 1989). The δ13C values of needles did not differ between sites or change consistently with needle age, but did decrease from the sun-to the shade-crown. This result confirms earlier conclusions from gas exchange measurements that gaseous air pollutants did no long-lasting damage in an area where such damage was expected. Twigs (δ13C between-25.3 and-27.8‰) were significantly less depleted in 13C than needles (δ13C between-27.3 and-29.1‰), and δ13C in twigs increased consistently with age. The δ15N values of needles ranged between-2.5 and-4.1‰ and varied according to stand and age. In young needles δ15N decreased with needle age, but remained constant or increased in needles that were 2 or 3 years old. Needles from the healthy site were more depleted in 15N than those from the declining site. The difference between sites was greater in old needles than in young ones. This differentiation presumably reflects an earlier onset of nitrogen reallocation in needles of the declining stand. δ15N values in twigs were more negative than in needles (-3.5 to-5.2‰) and showed age- and stand-dependent trends that were similar to the needles. δ15N values of roots and soil samples increased at both stands with soil depth from-3.5 in the organic layer to +4‰ in the mineral soil. The δ15N values of roots from the mineral soil were different from those of twigs and needles. Roots from the shallower organic layer had values similar to twigs and needles. Thus, the bulk of the assimilated nitrogen was presumably taken up by the roots from the organic layer. The problem of separation of ammonium or nitrate use by roots from different soil horizons is discussed.

19.
Oecologia ; 100(4): 406-412, 1994 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-28306929

RESUMO

Natural abundances of nitrogen isotopes, δ15N, indicate that, in the same habitat, Alaskan Picea glauca and P. mariana use a different soil nitrogen compartment from the evergreen shrub Vaccinium vitis-idaea or the deciduous grass Calamagrostis canadensis. The very low δ15N values (-7.7 ‰) suggest that (1) Picea mainly uses inorganic nitrogen (probably mainly ammonium) or organic N in fresh litter, (2) Vaccinium (-4.3 ‰) with its ericoid mycorrhizae uses more stable organic matter, and (3) Calamagrostis (+0.9 ‰) exploits deeper soil horizons with higher δ15N values of soil N. We conclude that species limited by the same nutrient may coexist by drawing on different pools of soil N in a nutrient-deficient environment. The differences among life-forms decrease with increasing N availability. The different levels of δ15N are associated with different nitrogen concentrations in leaves, Picea having a lower N concentration (0.62 mmol g-1) than Vaccinium (0.98 mmol g-1) or Calamagrostis (1.33 mmol g-1). An extended vector analysis by Timmer and Armstrong (1987) suggests that N is the most limiting element for Picea in this habitat, causing needle yellowing at N concentrations below 0.5 mmol g-1 or N contents below 2 mmol needle-1. Increasing N supply had an exponential effect on twig and needle growth. Phosphorus, potassium and magnesium are at marginal supply, but no interaction between ammonium supply and needle Mg concentration could be detected. Calcium is in adequate supply on both calcareous and acidic soils. The results are compared with European conditions of excessive N supply from anthropogenic N depositions.

20.
Oecologia ; 82(4): 478-483, 1990 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28311471

RESUMO

Two CAM plant species (Kalanchoe daigremontiana and K. tubiflora) were cultivated in pure cultures with two different levels of nitrogen and water supply. A comparison of the plant dry weight showed that the productivity was severely reduced under low nitrogen or/and water conditions. Additionally the proportion of the different organs contributing to the total biomass, and thus the ratio of root/shoot dry weight shifted substantially. At the same time the production of leaf buds in ratio to leaf biomass was increased. Concentrations of organic nitrogen and nitrate in the shoots were drastically reduced under low nitrogen or/and water conditions, but organic nitrogen concentration in the roots remained relatively high. The leaf conductance over a day was investigated only for K. daigremontiana, and decreased with reduced water and nitrogen supply. The results indicate that CAM plants do not have the predicted high nitrogen use efficiency. Under environmental stress they change from biomass production towards provisions for life preservation.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA