RESUMEN
Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.
Asunto(s)
Ecosistema , Peces , Biología Marina , Animales , Arqueología , Bacterias , Cnidarios , Conservación de los Recursos Naturales , Eutrofización , Sedimentos Geológicos , Humanos , Algas Marinas , Mariscos , Factores de TiempoRESUMEN
Human tumors and tumor cell lines were analyzed for the presence of mRNA coding for transforming growth factors alpha and beta (TGF-alpha and -beta) and the epidermal growth factor receptor. TGF-alpha mRNA was not detectable in hematopoietic tumor cell lines but was found in a variety of solid tumor cells, particularly carcinomas. Many of the tumors that contained TGF-alpha mRNA also expressed high levels of epidermal growth factor receptor mRNA. The concentration of TGF-alpha in the media of several tumor cell lines did not necessarily correlate with TGF-alpha mRNA levels, as a substantial fraction of TGF-alpha can remain cell associated. The levels of TGF-beta mRNA in tumor cell lines and tumor specimens were variable, but higher in tumors than in the adjacent normal tissues.
Asunto(s)
Receptores ErbB/genética , Neoplasias/metabolismo , Péptidos/genética , ARN Mensajero/genética , Línea Celular , Femenino , Humanos , Hibridación de Ácido Nucleico , ARN Mensajero/biosíntesis , Valores de Referencia , Factores de Crecimiento TransformadoresRESUMEN
Murine peritoneal exudate cells (PEC) treated with murine recombinant interferon-gamma (IFN-gamma) (greater than 99% estimated purity), or concanavalin A-stimulated spleen cell supernatants developed tumoricidal properties (macrophage activation factor [MAF] activity). MAF activity was found to occur with treatments of 10 U/ml IFN-gamma, and at levels as low as 1 U/ml IFN-gamma if a second signal (5 ng/ml endotoxin) was present in the MAF assay. Endotoxin (lipopolysaccharide [LPS]) alone at these levels failed to induce MAF; induction of MAF was observed at 1,000-fold greater levels. The ability of IFN-gamma to stimulate murine PEC was species specific. Various sources of materials that displayed MAF activity, including supernatants from interleukin 2-dependent cloned cytotoxic murine T lymphocyte lines that did not display detectable antiviral activity, were neutralized by antibody raised and affinity purified against recombinant IFN-gamma. Thus, IFN-gamma, although never detectable by antiviral assays, appears to be present in many lymphokine preparations and has potent macrophage activation capability.
Asunto(s)
Interferón gamma/fisiología , Linfocinas/fisiología , Activación de Macrófagos , Animales , Líquido Ascítico/inmunología , Línea Celular , Citotoxicidad Inmunológica , Femenino , Cobayas , Humanos , Interferón gamma/biosíntesis , Interferón gamma/inmunología , Cinética , Activación de Linfocitos , Linfocinas/biosíntesis , Linfocinas/inmunología , Factores Activadores de Macrófagos , Masculino , Ratones , Ratones Endogámicos C57BL , Pruebas de Neutralización , Conejos , Linfocitos T/inmunologíaRESUMEN
The shells of large benthic foraminifera contain a record of seasonal temperature ranges and life history stages. Marginopora vertebralis and Cyclorbiculina compressa show distinct differences in life history, growth rate history, and life-span, as reflected in stable isotope patterns within their shells.
RESUMEN
The California mussel Mytilus californianus records with high fidelity annual temperature variations of nearshore waters in the oxygen isotope composition of its shell. The onset and termination of upwelling events (and metabolic activity) are recorded in the associated carbon isotope signal, and the magnitude and timing of upwelling can be estimated. The method has implications for studying the history of upwelling and the life history of living and fossil mollusks and for analyzing shell midden deposits.
RESUMEN
The oxygen and carbon isotopic signals of planktonic Foraminifera from closely spaced samples from two box cores taken in the western equatorial Pacific change through the glacial-to-Holocene transition as a result of several factors, one of which is the Holocene dissolution pulse starting about 12,000 years ago and reaching full force shortly after. The onset of dissolution comes shortly after the maximum rate of deglaciation but well before the maximum drop in fertility in upper waters. The effect of dissolution is 20 to 30 percent of the amplitude of isotopic change in Globigerinoides sacculifer, at the depth of the present lysocline.
RESUMEN
Seismic reflection profiles and the structure of sediments in box cores from Ontong-Java Plateau indicate large-scale land sliding and sediment flow processes, respectively. The topographic morphology of sliding and slumping is depth- dependent, suggesting control by dissolution processes.
RESUMEN
The diversity of a planktonic foraminiferal assemblage on the ocean floor depends on the state of preservation of that assemblage. As dissolution progresses, species diversity (number of species in the assemblage) decreases, but compound diversity (based on relative species abundance) first increases and then decreases; species dominance first decreases and then increases. The reason for these changes is that the species most susceptible to solution deliver moresediment to the ocean floor than do species with solution-resistant shells, possibly because the more soluble tests are produced in surface waters, where growth and production are greatest.
RESUMEN
Radiolarian skeletons were placed at several depths on the taut mooring wire of a buoy in the central Pacific for 4 months. Recent radiolarian sediment dissolved at appreciable rates at depths shallower than 2000 meters; solution was greatest near the surface and decreased with depth. This pattern correlates with bathymetric distributions of dissolved silicon and of temperature. Siliceous Radiolaria from planktonic samples appeared to dissolve about eight times faster than those from sediment. Tripyleans seemed to be less resistant than polycystins. Acantharia dissolved completely at all depths.
RESUMEN
In a study of the rate of production of four species of planktonic Foraminifera in the region of the California Current it was found that their life spans are of the order of 1 month. Reproduction seems to take place mainly in the upper hundred meters. Results are in contrast to previous evidence presented in favor of yearly life cycles and maturing at great depth in other species of planktonic Foraminifera.
Asunto(s)
Ecología , Eucariontes/crecimiento & desarrollo , Biología Marina , Plancton/crecimiento & desarrolloRESUMEN
Samples of foraminiferal ooze were exposed to ocean water at various depths for 4 months, attached to the taut wire of a buoy in the central Pacific. Appreciable solution took place below 1000 meters and increased rapidly below 3000 meters and below 5000 meters. The fact that samples from different locations appear to dissolve at different rates suggests that the previous history of a sample determines its solubility. Solution is selective; it changes species composition, size distribution, content of damaged shells, and average particle weight of an assemblage.