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S Linder

Publications and source records attributed to S Linder.

At least 37 records · Page 2Linked to original sources
PubMed2001

Effects of nutrition and soil water availability on water use in a Norway spruce stand.

We investigated effects of nutrition and soil water availability on sap flux density, transpiration per unit leaf area (EL), and canopy stomatal conductance (GS) of Norway spruce (Picea abies L. (Karst.)) in northern Sweden during the 1996 growing season. Our objectives were to determine (1) if artificially imposed drought (65% rain diversion) reduces soil water sufficiently to cause physiological limitations to whole-tree and plot-scale water transport, and (2) whether increased capacity for water transport resulting from fertilization-induced increases in leaf (> 3-fold) and sapwood areas (> 2.3-fold) deplete soil water sufficiently to cause a negative feedback on GS and EL. We monitored soil water content (theta) and soil water potential (PsiS) in control (C), drought (D), fertilized (F) and irrigated + fertilized (IL) treatment plots, along with site meteorological conditions. Ten trees per plot were monitored for sap flow. Although there were significant treatment differences in mean daily EL (C > D > F; P < 0.01) and GS (C > D > F; P < 0.05), variation in absolute magnitudes was small. Therefore, transpiration differences on a unit ground area basis (EC) were nearly proportional to leaf area differences. Precipitation was well distributed throughout the study period and so PsiS remained high, except during short dry periods in Plot F when it declined rapidly. Thus, although soil water was not limiting to GS, EL or EC when precipitation was uniformly distributed throughout the growing season, we cannot conclude that water availability would not limit GS in fertilized stands if the seasonal distribution of precipitation were altered.

Picea↗
PubMed2001

Growth and dry-matter partitioning of young Populus trichocarpa in response to carbon dioxide concentration and mineral nutrient availability.

Young individuals of a single black cottonwood (Populus trichocarpa Torr. & Gray) clone were raised for three growing seasons in whole-tree chambers and exposed to either ambient or elevated atmospheric carbon dioxide concentration ([CO2]), with either a high or a low mineral nutrient supply, in a factorial experimental design. Nutrient availability had a larger effect on growth and dry matter partitioning than did [CO2]. Total biomass did not differ significantly with CO2 treatment when nutrient availability was low. However, elevated [CO2] increased whole-plant biomass by 47% in the high nutrient availability treatment. Carbon dioxide enrichment reduced leaf area ratio and specific leaf area significantly, but had no significant effect on mean leaf size or leaf mass ratio. Root mass ratio was significantly increased by elevated [CO2] at low, but not at high nutrient availability. A modified "demographic harvesting approach" made possible the retrospective estimation of stem and branch dry masses for different years. The relative growth rates of stem and branch were significantly enhanced by elevated [CO2] with high, but not with low nutrient availability. Canopy productivity index (CPI), i.e., the amount of stem and branch wood produced annually per unit leaf area, was raised 12% by elevated [CO2] when nutrient availability was high, but was reduced when nutrient availability was low, because of increased below ground allocation.

Biomass↗
PubMed2001

Carbon dioxide exchange in Norway spruce at the shoot, tree and ecosystem scale.

Net CO2 exchange in a 35-year-old boreal Norway spruce (Picea abies (L.) Karst.) forest in northern Sweden was measured at the shoot (NSE), tree (NTE) and ecosystem levels (NEE) by means of shoot cuvettes, whole-tree chambers and the eddy covariance technique, respectively. We compared the dynamics of gross primary production (GPP) at the three levels during the course of a single week. The diurnal dynamics of GPP at each level were estimated by subtracting half-hourly or hourly model-estimated values of total respiration (excluding light-dependent respiration) from net CO(2) exchange. The relationship between temperature and total respiration at each level was derived from nighttime measurements of NSE, NTE and NEE over the course of 1 month. There was a strong linear relationship (r2 = 0.93) between the hourly estimates of GPP at the shoot and tree levels, but the correlation between shoot- and ecosystem-level GPP was weaker (r2 = 0.69). However, the correlation between shoot- and ecosystem-level GPP was improved (r2 = 0.88) if eddy covariance measurements were restricted to periods when friction velocity was > or = 0.5 m s(-1). Daily means were less dependent on friction velocity, giving an r2 value of 0.94 between shoot- and ecosystem-level GPP. The correlation between shoot and tree levels also increased when daily means were compared (r2 = 0.98). Most of the measured variation in carbon exchange rate among the shoot, tree and ecosystem levels was the result of periodic low coupling between vegetation and the atmosphere at the ecosystem level. The results validate the use of measurements at the shoot and tree level for analyzing the contribution of different compartments to net ecosystem CO2 exchange.

Carbon Dioxide↗
PubMed2001

Pattern of distribution and prognostic value of angiogenesis in pancreatic duct carcinoma: a semiquantitative immunohistochemical study of 45 patients.

In specimens obtained from resected pancreata, the intratumoral microvessel density (IMD), the proliferation rate of the neoplastic parenchymal cells, and their p53 protein expression were assessed. The sources of errors were great in the measurements of the IMD. This statement can be illustrated by the finding that when the IMD was calculated by manual counting in five areas of intense neovascularization (hot spot regions), using x200 and x400 magnifications, the numbers of microvessels per square millimeter were 65+/-23 and 106+/-8, respectively, which reflects a significant difference. Two patterns of microvessel distribution could be identified: one with hot spots only in the stroma (n = 19) and one in which the hot spots were located in areas of neoplastic parenchyma (including its stroma) (n = 26). The IMD was significantly greater in the latter group. There was no general correlation of neoplastic disease with the IMD. However, when a scoring system was used to assess the angiogenesis, hot spots in areas of neoplastic parenchyma were associated with a greater proliferation rate of the tumor cells, and with a short length of survival of the patients from their neoplastic disease.

Aged↗
PubMed2001

Coiling phagocytosis of Borrelia burgdorferi by primary human macrophages is controlled by CDC42Hs and Rac1 and involves recruitment of Wiskott-Aldrich syndrome protein and Arp2/3 complex.

Lyme borreliosis is a multisystemic disorder primarily affecting the skin, nervous system, and joints. It is caused by the spirochete Borrelia burgdorferi sensu lato and is transmitted via ticks of the Ixodidae family. Persistence of borreliae within macrophages has been implicated in the often chronic history of borreliosis. The uptake of B. burgdorferi by professional phagocytes occurs predominantly by coiling phagocytosis, a host cell-driven process in which single pseudopods wrap around and engulf the spirochetes. In the present study, we investigated the molecular machinery and the signal transduction pathways controlling the formation of these unique uptake structures. We found that the phagocytosis of borreliae by primary human macrophages is accompanied by the formation of f-actin-rich structures, which in their morphological organization correspond well to the earlier described coiling pseudopods. Further experiments revealed that Wiskott-Aldrich Syndrome protein and Arp2/3 complex, major regulators of actin polymerization, are also recruited to these sites of actin accumulation. In addition, inhibition of an upstream regulator of Wiskott-Aldrich Syndrome protein, the Rho-family GTPase CDC42Hs, greatly inhibited the occurrence of borrelia-induced phagocytic uptake structures. Inhibition of Rac1, another Rho family GTPase, had a less-pronounced inhibitory effect, while blocking of Rho activity showed no discernible influence. These results suggest that basic mechanisms of actin polymerization that control other types of phagocytosis are also functional in the formation of the morphologically unique uptake structures in coiling phagocytosis. Our findings should enhance the understanding of the infection process of B. burgdorferi and contribute to devising new strategies for countering Lyme disease.

Actin-Related Protein 2↗
PubMed2001

Cisplatin induces the proapoptotic conformation of Bak in a deltaMEKK1-dependent manner.

In a panel of four human melanoma cell lines, equitoxic doses of cisplatin induced the proapoptotic conformation of the Bcl-2 family protein Bak prior to the execution phase of apoptosis. Because cisplatin-induced modulation of the related Bax protein was seen in only one cell line, a degree of specificity in the signal to Bak is indicated. Little is known about upstream regulation of Bak activity. In this study, we examined whether the apoptosis-specific pathway mediated by a kinase fragment of MEKK1 (DeltaMEKK1) is involved in the observed Bak modulation. We report that expression of a kinase-inactive fragment of MEKK1 (dominant negative MEKK [dnMEKK]) efficiently blocked cisplatin-induced modulation of Bak and cytochrome c release and consequently also reduced DEVDase activation and nuclear fragmentation. Accordingly, expression of a kinase-active MEKK1 fragment (dominant positive MEKK) was sufficient to induce modulation of Bak in three cell lines and to induce apoptosis in two of these. dnMEKK did not block cisplatin-induced c-Jun N-terminal kinase (JNK) activation, in agreement with a specifically proapoptotic role for the DeltaMEKK1 pathway. Finally, we show that reduction of Bak expression by antisense Bak reduced cisplatin-induced loss of mitochondrial integrity and caspase cleavage activity in breast cancer cell lines. In summary, we have identified Bak as a cisplatin-regulated component downstream in a proapoptotic, JNK-independent DeltaMEKK1 pathway.

Antineoplastic Agents↗
PubMed2000

The global carbon cycle: a test of our knowledge of earth as a system.

Motivated by the rapid increase in atmospheric CO2 due to human activities since the Industrial Revolution, several international scientific research programs have analyzed the role of individual components of the Earth system in the global carbon cycle. Our knowledge of the carbon cycle within the oceans, terrestrial ecosystems, and the atmosphere is sufficiently extensive to permit us to conclude that although natural processes can potentially slow the rate of increase in atmospheric CO2, there is no natural "savior" waiting to assimilate all the anthropogenically produced CO2 in the coming century. Our knowledge is insufficient to describe the interactions between the components of the Earth system and the relationship between the carbon cycle and other biogeochemical and climatological processes. Overcoming this limitation requires a systems approach.

Animals↗
PubMed2000

The polarization defect of Wiskott-Aldrich syndrome macrophages is linked to dislocalization of the Arp2/3 complex.

Wiskott-Aldrich syndrome (WAS) is an X-linked recessive disorder originally characterized by the clinical triad eczema, thrombocytopenia, and severe immunodeficieny, with recurrent bacterial and viral infections, indicating a profound immune cell defect. Such altered immune cells include monocytes, macrophages, and dendritic cells, which were reported to display disturbed cell polarization or chemotaxis. WAS is caused by mutations in the WAS protein (WASp), which is thought to organize the actin cytoskeleton through the Arp2/3 complex. Here we show that the Arp2/3 complex is an integral part of podosomes, actin-rich adhesion structures of macrophages, and that WAS macrophages fail to organize the Arp2/3 complex into podosomes. We also demonstrate that microinjection of a C-terminal acidic stretch of WASp into normal macrophages displaces Arp2/3 from podosomes and, in combination with chemoattractant stimulation of cells, induces a phenotype resembling the polarization-defective phenotype of stimulated WAS macrophages. These findings point to an important role of the Arp2/3 complex in polarization and migration of immune cells.

Actin-Related Protein 2↗
PubMed2000

Classification of human ovarian tumors using multivariate data analysis of polypeptide expression patterns.

Large amounts of data on quantitative gene expression are generated by procedures such as 2-DE analysis of proteins or cDNA microarrays. Quantitative molecular variation may potentially be used for the development of methods for the classification of tumors. We used here the statistical concepts of principal components analysis (PCA) and partial least square analysis (PLS) in an attempt to type ovarian tumors. Using a set of 170 polypeptides, 22 tumors were used to establish a model ("learning set") for classification into 3 groups (benign/borderline/malignant). Eighteen tumors were then used to test the model. Six of 8 carcinomas and 3 of 4 borderline tumors were correctly classified. Two of 6 benign lesions were correctly classified, 3 were classified as borderline and 1 as carcinoma. We conclude that it may be possible to classify tumors according to their constitutive protein expression profile using multivariate analysis, thus making classification by artificial intelligence a future possibility.

Breast Neoplasms↗
PubMed2000

Identification of gel-separated tumor marker proteins by mass spectrometry.

Two-dimensional gel electrophoresis with subsequent analysis by mass spectrometry was applied to study differences in protein expression between benign and malignant solid tumors from human beast, lung and ovary cells. Cells from freshly resected clinical material were lysed and the extracts were subjected to isoelectric focusing with immobilized pH gradients followed by second-dimensional separation on 10-13% sodium dodecyl sulfate (SDS)/polyacrylamide gels. Polypeptides were identified using matrix-assisted laser desorption/ionization and electrospray ionization mass spectrometry after in-gel protein digestion. Some of the upregulated polypeptides in malignant cells are of potential importance as markers of tumor proliferation. Twenty such proteins were identified, ten constituting novel identifications and ten sequence verifications of previously gel-matched proteins. The proteins identified span a wide range of functions, but several cases of protein truncation were found. Truncated forms of cytokeratins 6D and 8, and of cathepsin D were identified. Truncated froms of these over-expressed proteins support the presence of proteolytic processing steps in tumor material. The protein processing and the difference between protein and mRNA abundancies in tumors of different malignancy and origin suggest that studies at the protein level are important for an understanding of tumor phenotypes.

Biomarkers, Tumor↗
PubMed2000

Cancer proteomics: from identification of novel markers to creation of artifical learning models for tumor classification.

Studies of global protein expression in human tumors have led to the identification of various polypeptide markers, potentially useful as diagnostic tools. Many changes in gene expression recorded between benign and malignant human tumors are due to post-translational modifications, not detected by analyses of RNA. Proteome analyses have also yielded information about tumor heterogeneity and the degree of relatedness between primary tumors and their metastases. Results from our own studies have shown a similar pattern of changes in protein expression in different epithelial tumors, such as decreases in tropomyosin and cytokeratin expression and increases in proliferating cell nuclear antigen (PCNA) and heat shock protein expression. Such information has been used to create artificial learning models for tumor classification. The artificial learning approach has potential to improve tumor diagnosis and cancer treatment prediction.

Biomarkers, Tumor↗
PubMed2000

Inhibition of extracellular signal-regulated kinase 1/2 activity of the breast cancer cell line MDA-MB-231 leads to major alterations in the pattern of protein expression.

Biochemical and genetic strategies have implied that aberrant signaling in the extracellular signal-regulated kinase (ERK)/mitogen-activated protein (MAP) kinase pathway contributes significantly to transformed phenotypes. Using PD98059, an inhibitor of the ERK-kinase MEK1, we have here assessed the effects of ERK inhibition on the pattern of protein expression in the metastatic human breast cancer cell line MDA-MB-231. At a concentration of inhibitor which did not significantly affect cell growth, PD98059 induced large changes in the expression of MDA-MB-231 polypeptides. The majority of these changes were due to decreased expression of low-abundance proteins. Decreases of more abundant proteins such as glutathione-S-transferase pi, hsp80 and hsp100 were also recorded. The levels of a few proteins increased, among them cytokeratin 8. We conclude that PD98059 treatment of MDA-MB-231 cells induces large changes in protein expression.

Breast Neoplasms↗
PubMed2000

Increased apoptosis and increased clonogenic survival of 12V-H-ras transformed rat fibroblasts in response to cisplatin.

Mutationally activated Ras is involved in tumor progression and likely also in drug resistance. Using survival, viability and apoptosis assays, we have here compared the cisplatin sensitivities of FR3T3 rat fibroblasts and a 12V-H-ras transformed subline (Ras2:3). Around 24 h after cisplatin treatment Ras2:3 cells showed higher apoptosis levels and lower viability than FR3T3. This increased sensitivity correlated with weaker cisplatin-induced activation of Jun N-terminal kinase (JNK). In contrast to apoptosis assays, colony formation assays showed that Ras2:3 were more resistant to cisplatin than were FR3T3. This was partly due to the increased cisplatin sensitivity of FR3T3 seeded at low densities, as required in colony formation assays. In addition, Ras2:3 cisplatin survivors had a higher relative proliferative capacity. Cell cycle analyses showed that FR3T3 cells initially responded with a dose-dependent G2 arrest, while Ras2:3 accumulated in S-phase. Experiments with an anti-apoptotic mutant of MEKK1 suggested that the apoptotic response of Ras2:3 cells is not specific to the S-phase fraction. In summary, the cisplatin response of ras-transformed fibroblasts is distinct from that of parental cells, in that they show increased apoptosis, a different cell cycle response and increased post-treatment proliferative capacity. The results illustrate the need to carefully consider methods and protocols for in vitro studies on chemotherapy sensitivity.

Animals↗
PubMed2000

Identification of SopE2 from Salmonella typhimurium, a conserved guanine nucleotide exchange factor for Cdc42 of the host cell.

Salmonella typhimurium translocates effector proteins into host cells via the SPI1 type III secretion system to induce responses such as membrane ruffling and internalization by non-phagocytic cells. Activation of the host cellular RhoGTPase Cdc42 is thought to be a key event during internalization. The translocated Salmonella protein SopE is an activator for Cdc42. Because SopE is absent from most S. typhimurium strains it remains unclear whether all S. typhimurium strains rely on activation of Cdc42 to invade host cells. We have identified SopE2, a translocated effector protein common to all S. typhimurium strains. SopE2 is a guanine nucleotide exchange factor for Cdc42 and shows 69% sequence similarity to SopE. Analysis of S. typhimurium mutants demonstrated that SopE2 plays a role in recruitment of the actin-nucleating Arp2/3 complex to the membrane ruffles and in efficient host cell invasion. Transfection experiments showed that SopE2 is sufficient to activate host cellular Cdc42, to recruit the actin-nucleating Arp2/3 complex and to induce actin cytoskeletal rearrangements and internalization. In conclusion, as a result of SopE2 all S. typhimurium strains tested have the capacity to activate Cdc42 signalling inside host cells which is important to ensure efficient entry.

Actin-Related Protein 2↗
PubMed2000

Polypeptide expression in prostate hyperplasia and prostate adenocarcinoma.

Cells were collected from prostate hyperplasias (n = 6) and prostate carcinomas (n = 6) and subjected to two-dimensional gel electrophoresis (2-DE). The resulting polypeptide patterns were analysed with the PDQUEST computer software. Malignant tumors showed significant increases in the level of expression of proliferating cell nuclear antigen (PCNA), calreticulin, HSP 90 and pHSP 60, oncoprotein 18(v), elongation factor 2, glutathione-S-transferase pi (GST-pi), superoxide dismutase and triose phosphate isomerase. In addition, decreases in the levels of tropomyosin-1 and 2 and cytokeratin 18 were observed in prostate carcinomas compared to prostate hyperplasias. This pattern of alterations is similar to that observed in other carcinomas in our previous studies. All malignant tumors showed simultaneous alterations in 5 or more of 9 markers studied, whereas only one case of benign hyperplasia showed alterations in 5 markers. The EST-data base for prostate tumors available from NCI (CGAP) was searched for the expression of the mRNAs corresponding to proteins identified in our gels. Large differences in the relative expression of mRNAs and proteins were observed. Our data show alterations in the pattem of polypeptide expression in prostate carcinomas which are similar to those observed in other carcinomas.

Adenocarcinoma↗