[Platelet-derived growth factor].

When seeds deteriorate, they lose vigour and become more sensitive to stresses upon germination. Eventually seeds lose the ability to germinate. The factors which determine the rate of this ‘aging’ are the temperature and moisture content at which seeds are stored and an ill-defined parameter, seed quality. While it has been known for many years that manipulation of these factors influences the longevity of seeds, the precise interactions among them are so poorly understood as to preclude the prediction of longevity for a particular seed lot. Concepts from studies of materials and food stability can be applied to seed aging research, and this may help us take a more integrative approach to understanding the kinetics of seed deterioration. These concepts describe the physical environment of the seed matrix in response to changing water contents and temperature. Water activity models describe the state of water in the seed, while the glass models describe the state of the aqueous solution. Both models presume that changes of state affect the nature and kinetics of chemical reactions. Thus, the physical and chemical environment within the seed are inextricably linked.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S096025850000413X

Understanding the mechanisms and kinetics of seed aging

Objectives and methods: In idiopathic pulmonary fibrosis (IPF), proliferation of fibroblasts and increased matrix deposition result in pulmonary damage and respiratory insufficiency. We cultured human fibroblasts from lung biopsies of healthy adults and of three patients with IPF (histologically usual interstital pneumonitis, UIP) in order to compare proliferation ([3H]thymidine incorporation, cell count) and matrix protein expression (immune fluorescence, quantification of fibronectin synthesis using time-resolved immune fluorescence) of normal and UIP fibroblasts in response to various growth factors. Findings: The growth factors platelet-derived growth factor-BB (PDGF), epidermal growth factor (EGF), insulin growth factor-1 (IGF-1), insulin-like growth factor-2 (IGF-2), tumor necrosis factor α (TNFα), Transforming growth factor-β (TGFβ1), and fibroblast growth factor-2 (FGF-2) stimulate proliferation of normal lung fibroblasts significantly more than proliferation of UIP fibroblasts. Immunofluorescence reveals extensive expression of collagen I, collagen III, and fibronectin induced by serum, TGFβ1, and TNFα. This expression is more pronounced in UIP fibroblasts than in normal fibroblasts. Quantification of fibronectin synthesis reveals an enhanced fibronectin synthesis by UIP fibroblasts in response to PDGF, EGF, IGF-1, IGF-2, TNFα, TGFβ1, and FGF-2). Conclusions: Fibroblasts from normal and UIP lungs differ in their response to growth factors: Whereas normal fibroblasts show a predominantly proliferative response, UIP fibroblasts show an enhanced synthetic activity. Different fibroblast responses may contribute to progressive pulmonary fibrosis in patients with UIP.

Different effects of growth factors on proliferation and matrix production of normal and fibrotic human lung fibroblasts

Seeds are important to agriculture and conservation of plant biodiversity. In agriculture, seed germination performance is an important determinant of crop yield, in particular under adverse climatic conditions. Deterioration in seed quality is associated with the accumulation of cellular damage to macromolecules including lipids, protein, and DNA. Mechanisms that mitigate the deleterious cellular damage incurred in the quiescent state and in cycles of desiccation-hydration are crucial for the maintenance of seed viability and germination vigour. In early-imbibing seeds, damage to the embryo genome must be repaired prior to initiation of cell division to minimize growth inhibition and mutation of genetic information. Here we review recent advances that have established molecular links between genome integrity and seed quality. These studies identified that maintenance of genome integrity is particularly important to the seed stage of the plant lifecycle, revealing new insight into the physiological roles of plant DNA repair and recombination mechanisms. The high conservation of DNA repair and recombination factors across plant species underlines their potential as promising targets for the improvement of crop performance and development of molecular markers for prediction of seed vigour.

The importance of safeguarding genome integrity in germination and seed longevity

Fibroblast migration, proliferation, extracellular matrix protein synthesis and degradation, all of which play important roles in inflammation, are themselves induced by various growth factors and cytokines. Less is known about the interaction of these substances on lung fibroblast function in pulmonary fibrosis. The goal of this study was to investigate the effects of PDGF alone and in combination with IL-1beta and TNF-alpha on the production of human lung fibroblast matrix metalloproteinases, proliferation, and the chemotactic response. The assay for MMPs activity against FITC labeled type I and IV collagen was based on the specificity of the enzyme cleavage of collagen. Caseinolytis and gelatinolytic activities of secreted proteinases were analyzed by zymography. Fibronectin in conditioned media was measured using human lung fibronectin enzyme immunoassay. Cell proliferation was measured by 3H-Thymidine incorporation assay. Cell culture supernatants were tested for PGE2 content by ELISA. Chemotactic activity was measured using the modified Boyden chamber. Matrix metalloproteinase assay indicated that IL-1beta, TNF-alpha and PDGF induced intestitial collagenase (MMP-1) production. MMP assay also indicated that IL-1beta and TNF-alpha had inhibitory effects on MMP-2,9(gelatinaseA,B) production. Casein zymography confirmed that IL-1beta stimulated stromlysin (matrix metalloproteinase 3; MMP-3) and gelatin zymography demonstrated that TNF-alpha induced MMP-9 production in human lung fibroblast, whereas PDGF alone did not. PDGF in combination with IL-1beta and TNF-alpha induced MMP-3 and MMP-9 activity, as demonstrated by zymography. PDGF stimulated lung fibroblast proliferation in a concentration-dependent manner, whereas IL-1beta and TNF-alpha alone had no effect. In contrast, the proliferation of human lung fibroblasts by PDGF was inhibited in the presence of IL-1beta and TNF-alpha, and this inhibition was not a consequence of any elevation of PGE2. PDGF stimulated fibroblast chemotaxis in a concentration-dependent manner, and this stimulation was augmented by combining PDGF with IL-1beta and TNF-alpha. These findings suggested that PDGF differentially regulated MMPs production in combination with cytokines, and further that MMP assay and zymography had differential sensitivity for detecting MMPs. The presence of cytokines with PDGF appears to modulate the proliferation and chemotaxis of human lung fibroblasts.

/pdf/differential-regulation-of-metalloproteinase-production-3d65ww59vz.pdf

Differential regulation of metalloproteinase production, proliferation and chemotaxis of human lung fibroblasts by PDGF, interleukin-1beta and TNF-alpha.

Chromosome integrity and DNA polymerase activity are negatively affected by improper storage of maize seeds. We have extended our studies on the effect of improper storage on DNA metabolism by analysing the effect of hot–dry and hot–humid conditions on DNA ligase activity. An assay to measure ligase activity was established by using linearized plasmid DNA as substrate and protein extracts from maize axes. Optimal conditions were established for the in vitro assay. Enzyme activity was importantly reduced under both storage conditions. Activity recovered 6–9 h after imbibition. A model for loss of viability and vigour due to damage of DNA metabolism is proposed.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0960258500000994

DNA ligase activity in deteriorated maize embryo axes during germination: a model relating defects in DNA metabolism in seeds to loss of germinability

Expression of a 2.8-kb PDGF-B/c-sis Transcript and Synthesis of PDGF-Like Protein by Human Lung Fibroblasts

Los estudios realizados durante los ultimos 20 anos en torno a una de las familias mas importantes de las proteinas de estres, la de las chaperonas, han descubierto un panorama inesperadamente diverso y complejo. Si bien desde un principio se sospecho que este tipo de proteinas estaria muy probablemente involucrado en la proteccion y supervivencia de la celula agredida, nunca se llegaron a imaginar las vastas implicaciones que este tipo de polipeptidos tiene en la fisiopatologia celular y su posible participacion en enfermedades humanas. Con base en el principio fundamental de interaccion polipeptido-polipeptido, la naturaleza ha involucrado a las proteinas de estres (Hsp90, Hsp70, Hsp60, etc.) en papeles aparentemente tan diferentes como los de las moleculas que auxilian al plegamiento de otros polipeptidos, transporte intracelular, acarreadoras de peptidos antigenicos, indicadoras de transformacion y muerte celular, inductoras de maduracion de celulas dendriticas y hasta, posiblemente, moleculas amortiguadoras del cambio genetico y moduladoras del desarrollo celular y de la evolucion

/pdf/proteinas-de-estres-elementos-basicos-en-la-homeostasis-3o241hb57j.pdf

Fernando Montiel

Papers

DNA ligase activity in deteriorated maize embryo axes during germination: a model relating defects in DNA metabolism in seeds to loss of germinability

Expression of a 2.8-kb PDGF-B/c-sis Transcript and Synthesis of PDGF-Like Protein by Human Lung Fibroblasts

Proteínas de estrés: elementos básicos en la homeostasis