Mineralogy and geochemistry at DSDP Leg 64 Holes

At DSDP Site 477, late Quaternary diatomaceous muds and delta-derived silty-sand turbidites at 2000 meters water depth have been extensively and progressively altered by a deep-seated heat source beneath a sill. Bulk petrologic and microprobe analyses have identified a crudely zoned paragenesis within 260 meters sub-bottom which ranges from unaltered to slightly altered oozes (0-50 m), anhydrite-dolomite claystones (105-125 m), illite-chlorite-pyrite claystones (125-140 m), chlorite-pyrite-calcite-carbonaceous claystones with traces of K-feldspar, albite, epidote (140-190 m), and chlorite-epidote-quartz-albite-pyrrhotite-sphene sandstone (190-260 m). Several petrologic features suggest rapid processes of ocean floor metamorphism: (1) friable and porous textures, (2) abundant relict grains with overgrowths, (3) idiomorphic habits on epidotes, feldspars, and quartz, and (4) a steep gradient in levels of alteration. Many aspects of this hydrothermal assemblage are similar to hydrothermally metamorphosed sandstones of the Cerro Prieto, Mexico, geothermal area.

Bulk composition and clay mineralogy at DSDP Legs 56 and 57

Altogether 513 samples from sediments of Cretaceous to Pleistocene age from DSDP Legs 56 and 57 were examined by x-ray methods. The main constituents are clay minerals, quartz, feldspar, opaline silica, and volcanic glass. The sediment composition reflects the position of the sites in relation to the main source area, the Japanese Island Arc. For example, relatively coarse-grained material rich in quartz and feldspar was deposited closest to the islands, whereas finer-grained material rich in clay minerals (mainly smectite and illite, with lesser amounts of kaolinite and chlorite) was deposited farther seaward. Vertical fluctuations in the composition of the sediments show the same trend in all sites and are caused mainly by a fluctuating contribution of biogenic silica with time. A trend reversal in the chlorite/kaolinite ratio at Site 438 supports the conclusion that the subsidence of the Oyashio ancient landmass took place during the middle Miocene. That ratio also indicates a northwest drift in the position of Site 436 by sea floor spreading. Oscillations of the illite/smectite ratio during the Pleistocene at Site 436 show the variations of climate during this period. During early diagenesis potassium is fixed in smectite. With increasing depth of burial a smectite-illite mixed layer is formed, with increasing illite layering. At Sites 434, 440, and 441, stepwise changes confirm intensive tectonic process at the midslope terrace and the lower inner slope of the Japan Trench.

Mineralogy and major-element chemistry of volcanic ash of ODP Site 131-808

Mineralogical and major-element compositions of 72 samples of volcanic ash, recovered from Site 808 at Nankai Trough during Leg 131, were analyzed in relation to the early diagenetic alteration. Alteration products are first observed at the following depths: smectite, 200 mbsf; clinoptilolite, 646 mbsf; and analcite, 810 mbsf. Glass decomposition dominates over authigenic mineral formation between 200 and 550 mbsf in the sediment column, whereas mineral formation becomes dominant below 550 mbsf. Based on the X-ray diffraction patterns, a broad and asymmetric peak of 15A suggests a presence of illite/smectite (I/S) mixed-layered minerals in a sample from 646 mbsf. I/S mixed-layered mineral formation, however, rarely occurs even at the bottom of the sediment column (1290 mbsf) at 120° C. This is possibly because zeolite (especially clinoptilolite) formed in the ash interferes with illite formation in the smectite. The formation of alteration minerals affects the major-element chemistry of the ash and the interstitial waters. H4SiO4 concentrations in interstitial waters increase during glass decomposition and decrease with smectite and clinoptilolite formation. K is removed from interstitial water into smectite and/or clinoptilolite. Mg is fixed into smectite (and/or chlorite).

Minerals of bulk samples and clay fraction at DSDP Leg 80 Holes

At the request of the Leg 80 scientific party, selected samples of Cretaceous age were processed by X-ray diffraction at the mineralogy laboratories at the Ecole des Mines (Albian to Late Cretaceous samples) and at the Institut de Géologie at Dijon (Barremian samples). The results were used in developing the lithostratigraphy and sedimentology discussed in this volume by Rat et al. 1985 (doi:10.2973/dsdp.proc.80.140.1985) in their study of Barremian-Albian paleoenvironment, by Graciansky and Gillot in their study of Albian and Cenomanian limestones, and by Graciansky and Bourbon in their paleoenvironmental reconstructions for the Late Cretaceous chalks.

Mineral and chemical compositions of clay sediments from the Pacific Ocean, DSDP data

Mineral and chemical compositions, as well as conditions of formation of clay sediments in major structural elements of the Pacific Ocean floor with different ages are under consideration in the monograph. Depending on evolution of the region two ways of clay sediment formation are identified: terrigenous and authigenic. It is shown that terrigenous clay sediments predominate in marginal parts of the Pacific Ocean. Authigenic mineral formation occurring in the basal part of the sedimentary cover primarily results from removal of material from underlying basalts. This material is released during secondary alteration of the basalts due to their interaction with sea water, as well as with deep solutions.

Mineralogy, lithology and stable isotope composition of diagenetic siliceous rocks from ODP Leg 129 sites

Ocean Drilling Program Leg 129 recovered chert, porcellanite, and radiolarite from Middle Jurassic to lower Miocene strata from the western Pacific that formed by different processes and within distinct host rocks. These cherts and porcellanites formed by (1) replacement of chalk or limestone, (2) silicification and in-situ silica phase-transformation of bedded clay-bearing biosiliceous deposits, (3) high-temperature silicification adjacent to volcanic flows or sills, and (4) silica phase-transformation of mixed biosiliceous-volcaniclastic sediments. Petrologic and O-isotopic studies highlight the key importance of permeability and time in controlling the formation of dense cherts and porcellanites. The formation of dense, vitreous cherts apparently requires the local addition and concentration of silica. The influence of permeability is shown by two examples, in which: (1) fragments of originally identical radiolarite that were differentially isolated from pore-water circulation by cement-filled fractures were silicified to different degrees, and (2) by the development of secondary porosity during the opal-CT to quartz inversion within conditions of negligible permeability. The importance of time is shown by the presence of quartz chert below, but not above, a Paleogene hiatus at Site 802, indicating that between 30 and 52 m.y. was required for the formation of quartz chert within calcareous-siliceous sediments. The oxygen-isotopic composition for all Leg 129 carbonate- and Fe/Mn-oxide-free whole-rock samples of chert and porcellanite range widely from d18O = 27.8 per mil to 39.8 per mil vs. V-SMOW. Opal-CT samples are consistently richer in 18O (34.1 per mil to 39.3 per mil) than quartz subsamples (27.8 per mil to 35.7 per mil). Using the O-isotopic fractionation expression for quartz-water of Knauth and Epstein (1976) and assuming d18Opore water = -1.0 per mil, model temperatures of formation are 7°-26°C for carbonate-replacement quartz cherts, 22°-25°C for bedded quartz cherts, and 32°-34°C for thermal quartz cherts. Large variations in O-isotopic composition exist at the same burial depth between co-existing silica phases in the same sample and within the same phase in adjacent lithologies. For example, quartz has a wide range of isotopic compositions within a single breccia sample; d18O = 33.4 per mil and 28.0 per mil for early and late stages of fracture-filling cementation, and 31.6 per mil and 30.2 per mil for microcrystalline quartz precipitation within enclosed chert and radiolarite fragments. Similarly, opal-CT d101 spacing varies across lithologic or diagenetic boundaries within single samples. Co-occurring opal-CT and chalcedonic quartz in shallowly buried chert and porcellanite from Sites 800 and 801 have an 8.7 per mil difference in d18O, suggesting that pore waters in the Pigafetta Basin underwent a Tertiary shift to strongly 18O-depleted values due to alteration of underlying Aptian to Albian-Cenomanian volcaniclastic deposits after opal-CT precipitation, but prior to precipitation of microfossil-filling chalcedony.

Chemistry and mineralogy of ODP Leg 124 sediment samples

From X-ray mineralogical studies and chemical analyses of the whole rocks and the fine fractions (<2 µm) of ten to fifteen samples at each site of ODP Leg 124, two major sources were identified in the sedimentary components of the Celebes and Sulu basins: (1) a terrestrial and continental contribution; (2) a volcanic influx that gives way to well-defined volcanic units or to a dilute contamination, consisting of coarse-grained minerals (Plagioclase, pyroxene, olivine, spinel) or a smectitic-rich fraction produced by the alteration of volcanic glasses and ashes. The continental signature increases the amount of quartz in the rocks and the phyllitic association is complex: micas, kaolinite, disordered interstratified clay-minerals. The chemical compositions of the bulk rocks and the fractions <2 µm are more potassic and aluminum-rich. The volcanic imprint depends on the grain-size and chemical properties of the components. Ca/Na contents highly variable compared to the K content of the bulk composition are due to the presence of coarse-grained volcanic Plagioclase. The fractions <2 µm are more magnesian than in the continental regime. The diagenesis is revealed by the crystallization of zeolites, the fixation of magnesium into the smectites that depletes the pore fluids in this element. Smectitization of the disordered interstratified clay minerals enriches the alkalinity of the pore fluids. Some deep formations of the Sulu Basin are affected by a thermal event, but no thermal event was recognized in the Celebes Basin.

Minerals, geochemistry and x-ray power characteristics at DSDP Sites 54-424, 60-458 and 60-459

Secondary minerals filling veins and vesicles in volcanic basement at Deep Sea Drilling Project Sites 458 and 459 indicate that there were two stages of alteration at each site: an early oxidative, probably hydrothermal, stage and a later, low-temperature, less oxidative stage, probably contemporaneous with faulting in the tectonically active Mariana forearc region. The initial stage is most evident in Hole 459B, where low-Al, high Fe smectites and iron hydroxides formed in vesicles in pillow basalts and low-Al palygorskite formed in fractures. Iron hydroxides and celadonite formed in massive basalts next to quartz-oligoclase micrographic intergrowths. Palygorskite was found in only one sample near the top of basement in Hole 458, but it too is associated with iron hydroxides. Palygorskite has previously been reported only in marine sediments in DSDP and other occurrences. It evidently formed here as a precipitate from fluids in which Si, Mg, Fe, and even some Al were concentrated. Experimental data suggest that the solutions probably had high pH and somewhat elevated temperatures. The compositions of associated smectites resemble those in hydrothermal sediments and in basalts at the Galapagos mounds geothermal field. The second stage of alteration was large-scale replacement of basalt by dioctahedral, trioctahedral, or mixed-layer clays and phillipsite along zones of intense fracturing, especially near the bottom of Holes 458 and 459B. The basalts are commonly slickensided, and there are recemented microfault offsets in overlying sediments. Native copper occurs in one core of Hole 458, but associated smectites are dominantly dioctahedral, unlike Hole 459B, where they are mainly trioctahedral, indicating nonoxidative alteration. The alteration in both holes is more intense than at most DSDP ocean crust sites and may have been augmented by water derived from subducting ocean crust beneath the fore-arc region.

Eocene-Oligocene diatoms in the western Indian Ocean

The occurrence of diatom species in the Eocene-Oligocene sections of Ocean Drilling Program (ODP) Leg 115 sites and Deep Sea Drilling Project (DSDP) Sites 219 and 236 in the low-latitude Indian Ocean are investigated. Diatoms are generally rare and poorly preserved in the Paleogene sequences we studied. The best-preserved assemblages are found close to ash layers in early Oligocene sediments. The low-latitude diatom zonation established for the Atlantic region by Fenner in 1984 is fully applicable to the Paleogene sequences of the western Indian Ocean. Correlation of the diatom zones to the calcareous nannofossil stratigraphy of the sites places the Coscinodiscus excavatus Zone of Fenner within calcareous nannofossil Subzone CP16b. For the Mascarene Plateau and the Chagos Ridge, the times when the sites studied, together with the areas upslope from them, subsided to below the euphotic zone are deduced from changes in the relative abundance between the group of benthic, shallow-water species and Grammatophora spp. vs. the group of fully planktonic diatom species. The Eocene section of Site 707, on the Mascarene Plateau, is characterized by the occurrence of benthic diatoms (approximately 10% of the diatom assemblage). These allochthonous diatoms must have originated from shallow-water environments around volcanic islands that existed upslope from ODP Site 707 in Eocene times. In Oligocene and younger sediments of Sites 707 and 706, occurrences of benthic diatoms are rare and sporadic and interpreted as reworked from older sediments. This indicates that the area upslope from these two Mascarene Plateau sites had subsided below the euphotic zone by the early Oligocene. Only Grammatophora spp., for which a neritic but not benthic habitat is assumed, continues to be abundant throughout the Oligocene sequences. The area of the Madingley Rise sites (Sites 709-710) and nearby shallower areas subsided below the euphotic zone already in middle Eocene times, as benthic diatoms are almost absent from these Eocene sections. Only sites located on abyssal plains, and which intermittently received turbidite sediments (e.g., Sites 708 and 711), contain occasionally single, benthic diatoms of Oligocene age. The occurrence of the freshwater diatom Aulacosira granulata in a few samples of late early Oligocene and late Oligocene age at Sites 707, 709, and 714 is interpreted as windblown. Their presence indicates at least seasonally arid conditions for these periods in the source areas of eastern Africa and India. Three new species and two new combinations are defined: Chaetoceros asymmetricus Fenner sp. nov.; Hemiaulus gracilis Fenner, sp. nov.; Kozloviella meniscosa Fenner, sp. nov.; Cestodiscus demergitus (Fenner) Fenner comb, nov.; and Rocella princeps (Jouse) Fenner comb. nov.

Minerals of bulk samples and the fine-grained (<2-µm) fractions from DSDP Leg 67 Holes

Leg 67 sample sediments are mainly composed of biogenic carbonate and biogenic siliceous materials. Apart from calcite, crystallized minerals are scarce; however, they are better represented in sites near the continent and in all Quaternary sediments. These minerals are: quartz, feldspars, smectite, and, rarely, chlorite, dolomite, and zeolite.

Bulk and clay mineral composition of ODP Leg 189 sites

Bulk and clay mineral investigations were conducted on ~750 samples from four sites drilled during Ocean Drilling Program Leg 189 on the western Tasmanian margin (Site 1168), the South Tasman Rise (Sites 1170 and 1171), and the East Tasman Plateau (Site 1172). The mineralogy of the bulk sediment is very similar at all sites, and major changes coincide with the boundaries of the three main lithologic units described in the Leg 189 Initial Reports volume. The clay mineral assemblages show significant regional differences, but their major variations coincide at all sites and with major changes in regional tectonics and climate.

Valorización de subproductos agrícolas y forestales como sustratos de cultivo en el estado de Oaxaca (México)

El presente trabajo aborda el aprovechamiento de algunos subproductos agrícolas (bagazo de maguey y fibra de coco) y forestales (corteza de pino) en el Estado de Oaxaca (Sur de México). El objetivo principal se centra en localizar, cuantificar y caracterizar estos con vistas a su aplicación como sustratos o componentes de sustratos en cultivos ornamentales, forestales y hortícolas, y a su uso como enmiendas en cultivos tipo. Así mismo se persigue reducir el uso de la turba y la tierra de monte como sustratos mayoritarios en la actualidad. Para la localización de los subproductos se utilizaron los datos de los registros parcelarios de los productores de coco para la obtención de copra (generadores de fibra de coco) de la región costa y de los productores de mezcal (generadores del residuo de bagazo de maguey) de la región valles centrales, así como las ubicaciones de los aserraderos forestales en el Estado de Oaxaca. Se emplea un Sistema de Información Geográfica (SIG) con una cartografía digitalizada de los elementos del medio (clima, geología y suelo), de los cultivos generadores (bagazo de maguey, fibra de coco y corteza de pino), de la agricultura protegida como receptora (tomate) y de la agricultura extensiva con cultivos receptores de enmienda (café, hule, limón, mango, palma de coco y maguey). La producción anual de los residuos se cartografía y cuantifica con los siguientes resultados: bagazo de maguey 624.000 t, fibra de coco 86.000 m3 y 72.000 t de corteza de pino. Mediante el estudio de las características de los suelos de los cultivos receptores y de los requerimientos de materia orgánica de cada cultivo se calcularon las necesidades totales de materia orgánica para cada suelo. Los resultados de las cantidades globales para cada cultivo en todo el Estado muestran una necesidad total de 3.112.000 t de materia orgánica como enmienda. Con los datos obtenidos y a través de un algoritmo matemático se realiza una propuesta de localización de dos plantas de compostaje (de bagazo de maguey y fibra de coco) y cuatro plantas de compostaje de corteza de pino. Con el fin de conocer los subproductos a valorizar como sustrato o componente de sustrato se caracteriza su composición física‐química, siguiendo Normas UNE‐EN, y se analizan mediante Resonancia Magnética Nuclear (RMN). Para el acondicionamiento de bagazo de maguey y la corteza de pino se realizaron ensayos de compostaje. Al final de 241 días la temperatura y la humedad de ambos procesos se encontraban en los rangos recomendados, indicando que los materiales estaban estabilizados y con calidad para ser utilizados como sustrato o componente de sustrato. Para la fibra de coco se realizó el proceso de molienda en seco de conchas de coco provenientes de la comunidad de Río Grande Oaxaca (Principal zona productora de copra en Oaxaca). Posteriormente se emplean los materiales obtenidos como componentes para sustratos de cultivo. Se estudia el compost de bagazo de maguey y siete mezclas; el compost de corteza de pino y ocho mezclas y la fibra de coco con tres mezclas. Estos sustratos alternativos permiten obtener mezclas y reducir el uso de la tierra de monte, turba, arcilla expandida y vermiculita, siendo por tanto una alternativa sostenible para la producción en invernadero. Se elaboraron mezclas especificas para el cultivo de Lilium hibrido asiático y oriental (siete mezclas), sustratos eco‐compatibles para cultivo de tomate (nueve mezclas), para la producción de planta forestal (siete mezclas) y para la producción de plántula hortícola (ocho mezclas). Como resultados más destacados del bagazo de maguey, corteza de pino y las mezclas obtenidas se resume lo siguiente: el bagazo de maguey, con volúmenes crecientes de turba (20, 30, 50 y 60 %) y la corteza de pino, con volúmenes de turba 40 y 60%, presentan valores muy recomendados de porosidad, capacidad de aireación, capacidad de retención de humedad y equilibrio agua‐aire. Para la fibra de coco, la procedente de Río Grande presenta mejor valoración que la muestra comercial de fibra de coco de Morelos. Por último se llevó a cabo la evaluación agronómica de los sustratos‐mezclas, realizando cinco experimentos por separado, estudiando el desarrollo vegetal de cultivos tipo, que se concretan en los siguientes ensayos: 1. Producción de Lilium asiático y oriental en cama para flor de corte; 2. Producción de Lilium oriental en contenedor para flor de corte; 3. Producción de plántula forestal (Pinus greggii E y Pinus oaxacana M); 4. Producción de tomate (Solanum lycopersicum L) y 5. Producción de plántula de tomate en semillero (Solanum lycopersicum L). En relación a la producción de Lilium hibrido asiático en cama los sustratos corteza de pino (CPTU 80:20 v/v), corteza de pino + sustrato comercial (CPSC 80:20 v/v) y corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV2 30:40:15:15 v/v) presentan los mejores resultados. Dichos sustratos también presentan adecuados resultados para Lilium hibrido oriental con excepción de la corteza de pino + turba (CPTU 80:20 v/v). En la producción de Lilium hibrido oriental en contenedor para flor de corte, además de los sustratos de CPSC y CPTAEV2, la mezcla de corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV 70:20:5:5 v/v) manifestó una respuesta favorable. En el ensayo de producción de plántulas de Pinus greggii E y Pinus oaxacana Mirov, las mezclas con corteza de pino+turba+arcilla expandida+vermiculita (CPTAEV2 30:40:15:15 v/v) y bagazo de maguey turba+arcilla expandida+vermiculita (BMTAEV2 30:60:5:5 v/v) son una alternativa que permite disminuir el empleo de turba, arcilla expandida y vermiculita, en comparación con el sustrato testigo de turba+arcilla expandida+vermiculita (TAEV 60:30:10 v/v). En la producción de tomate (Solanum lycopersicum L) frente a la utilización actual del serrín sin compostar (SSC), las mezclas alternativas de bagazo de maguey+turba (BMT 70:30 v/v), fibra de coco de Río Grande (FCRG 100v/v) y corteza de pino+turba (CPT 70:30 v/v), presentaron los mejores resultados en rendimientos. Así mismo, en la producción de plántulas de tomate las dos mezclas alternativas de bagazo de maguey+turba+ arcilla expandida+vermiculita (BMTAEV5 50:30:10:10 v/v) y (BMTAEV6 40:40:10:10 v/v) presentaron mejores resultados que los obtenidos en la mezcla comercial (Sunshine 3), mayoritariamente utilizada en México en la producción de plántula de tomate y hortícola. ABSTRACT This paper addresses the use of some agricultural products (maguey bagasse and coconut fiber) and forestry (pine bark) in the State of Oaxaca (southern Mexico). The principal purpose is to locate, quantify and characterize these with the idea of applying them as substrates or substrate components in ornamental crops, forestry, horticultural, and their use as crop amendments. On the other hand, the reduction of peat and forest soil as main substrates is pursued. For the location of the products, registry parcel data from copra producers (coconut fiber generators) of the coastal region and mescal producers (maguey bagasse residue generators) of the central valleys region, as well as the locations of forest mills in the State of Oaxaca. A Geographic Information System (GIS) with digital mapping of environmental factors (climate, geology and soil), crop generators of residues (maguey bagasse, coconut and pine bark) receptors of amendments such as protected agriculture (tomato) and extensive agriculture crops (coffee, rubber, lemon, mango, coconut and agave). The annual production of waste is mapped and quantified with the following results: 624,000t maguey bagasse, coconut fiber 72,000 m3 and 86,000 t of pine bark. Through the study of receiving crops soils properties of and organic matter requirements of each crop, total needs of organic matter for each soil were estimated. The results of the total quantities for each crop across the state show a total of 3,112,000 t of organic matter needed as amendment. Using that data and a mathematical algorithm, the location of two composting plants (agave bagasse and coconut fiber) and four composting plants pine bark was proposed. In order to know the by‐products that were going to be used as substrates or substrate components, their physical‐chemical composition was analyzed following UNE‐EN technics. Furthermore they were analyzed by Nuclear Magnetic Resonance (NMR). For conditioning of maguey bagasse and pine bark, composting essays were conducted. At the end of 241 days the temperature and humidity of both processes were at the recommended ranges, indicating that the materials were stabilized and had reached the quality to be used as a substrate or substrate component. Coconut shells from the community of Rio Grande Oaxaca (Main copra producing area in Oaxaca) were put through a process of dry milling. Subsequently, the obtained materials were used as components for growing media. We studied the maguey bagasse compost and seven mixtures; the pine bark compost and eight blends and coconut fiber with three mixtures. These alternative substrates allow obtaining mixtures and reduce the use of forest soil, peat, vermiculite and expanded clay, making it a sustainable alternative for greenhouse production. Specific mixtures were prepared for growing Lillium, Asian and eastern hybrids (seven blends), eco‐compatible substrates for tomato (nine mixtures), for producing forest plant (seven mixtures) and for the production of horticultural seedlings (eight mixtures). Results from maguey bagasse, pine bark and mixtures obtained are summarized as follows: the maguey bagasse, with increasing volumes of peat (20, 30, 50 and 60%) and pine bark mixed with 40 and 60% peat by volume, have very recommended values of porosity, aeration capacity, water retention capacity and water‐air balance. Coconut fiber from Rio Grande had better quality than commercial coconut fiber from Morelos. Finally the agronomic evaluation of substrates‐mixtures was carried out conducting five experiments separately: 1. Production of Asiatic and Eastern Lilium in bed for cut flower, 2. Production of oriental Lillium in container for cut flower, 3.Production of forest seedlings (Pinus greggii E and Pinus oaxacana M), 4. Production of tomato (Solanum lycopersicum L) and 5. Tomato seedling production in seedbed (Solanum lycopersicum L). In relation to the production of hybrid Asian Lilium in bed, pine bark substrates (CPTU 80:20 v/v), pine bark + commercial substrate (CPSC 80:20 v/v) and pine bark + peat + expanded clay + vermiculite (CPTAEV2 30:40:15:15 v/v) showed the best results. Such substrates also have adequate results for Lilium Oriental hybrid except pine bark + peat (CPTU 80:20 v / v). In the production of Lilium oriental hybrid container for cut flower, besides the CPSC and CPTAEV2 substrates, the mixture of pine bark + peat + vermiculite expanded clay (CPTAEV 70:20:5:5 v / v) showed a favorable response. In the production of Pinus greggii E and Pinus oaxacana Mirov seedlings trial, mixtures with pine bark + peat + expanded clay + vermiculite (CPTAEV2 30:40:15:15 v/v) and maguey bagasse+ peat+ expanded clay + vermiculite (BMTAEV2 30:60:5:5 v / v) are an alternative which allows reducing the use of peat, vermiculite and expanded clay in comparison with the control substrate made of peat + expanded clay+ vermiculite (60:30 TAEV: 10 v/v). In the production of tomato (Solanum lycopersicum L), alternative mixes of maguey bagasse + peat (BMT 70:30 v/v), coconut fiber from Rio Grande (FCRG 100 v / v) and pine bark + peat (CPT 70:30 v / v) showed the best results in yields versus the current use of sawdust without compost (SSC). Likewise, in the production of tomato seedlings of the two alternative mixtures maguey bagasse + peat expanded clay + vermiculite (BMTAEV5 50:30:10:10 v/v) and (BMTAEV6 40:40:10:10 v/v) had better results than those obtained in the commercial mixture (Sunshine 3), mainly used in Mexico in tomato seedling production and horticulture.

Electrical stimulation of neonatal cardiomyocytes results in the sequential activation of nuclear genes governing mitochondrial proliferation and differentiation

Electrical stimulation of neonatal cardiac myocytes produces hypertrophy and cellular maturation with increased mitochondrial content and activity. To investigate the patterns of gene expression associated with these processes, cardiac myocytes were stimulated for varying times up to 72 hr in serum-free culture. The mRNA contents for genes associated with transcriptional activation [c-fos, c-jun, JunB, nuclear respiratory factor 1 (NRF-1)], mitochondrial proliferation [cytochrome c (Cyt c), cytochrome oxidase], and mitochondrial differentiation [carnitine palmitoyltransferase I (CPT-I) isoforms] were measured. The results establish a temporal pattern of mRNA induction beginning with c-fos (0.25–3 hr) and followed sequentially by c-jun (0.5–3 hr), JunB (0.5–6 hr), NRF-1 (1–12 hr), Cyt c (12–72 hr), and muscle-specific CPT-I (48–72 hr). Induction of the latter was accompanied by a marked decrease in the liver-specific CPT-I mRNA, thus supporting the developmental fidelity of this pattern of gene regulation. Consistent with a transcriptional mechanism, electrical stimulation increased c-fos, β-myosin heavy chain, and Cyt c promoter activities. These increases coincided with a rise in their respective endogenous gene transcripts. NRF-1, cAMP response element, and Sp-1 site mutations within the Cyt c promoter reduced luciferase expression in both stimulated and nonstimulated myocytes. Mutations in the NRF-1 and CRE sites inhibited the induction by electrical stimulation (5-fold and 2-fold, respectively) whereas mutation of the Sp-1 site maintained or increased the fold induction. This finding is consistent with the appearance of NRF-1 and fos/jun mRNAs prior to that of Cyt c and suggests that induction of these transcription factors is a prerequisite for the transcriptional activation of Cyt c expression. These results support a regulatory role for NRF-1 and possibly AP-1 in the initiation of mitochondrial proliferation.

Non-CpG methylation is prevalent in embryonic stem cells and may be mediated by DNA methyltransferase 3a

Current evidence indicates that methylation of cytosine in mammalian DNA is restricted to both strands of the symmetrical sequence CpG, although there have been sporadic reports that sequences other than CpG may also be methylated. We have used a dual-labeling nearest neighbor technique and bisulphite genomic sequencing methods to investigate the nearest neighbors of 5-methylcytosine residues in mammalian DNA. We find that embryonic stem cells, but not somatic tissues, have significant cytosine-5 methylation at CpA and, to a lesser extent, at CpT. As the expression of the de novo methyltransferase Dnmt3a correlates well with the presence of non-CpG methylation, we asked whether Dnmt3a might be responsible for this modification. Analysis of genomic methylation in transgenic Drosophila expressing Dnmt3a reveals that Dnmt3a is predominantly a CpG methylase but also is able to induce methylation at CpA and at CpT.

Latent N-methyl-D-aspartate receptors in the recurrent excitatory pathway between hippocampal CA1 pyramidal neurons: Ca(2+)-dependent activation by blocking A1 adenosine receptors.

When performed at increased external [Ca2+]/[Mg2+] ratio (2.5 mM/0.5 mM), temporary block of A1 adenosine receptors in hippocampus [by 8-cyclopentyltheophylline (CPT)] leads to a dramatic and irreversible change in the excitatory postsynaptic current (EPSC) evoked by Schaffer collateral/commissural (SCC) stimulation and recorded by in situ patch clamp in CA1 pyramidal neurons. The duration of the EPSC becomes stimulus dependent, increasing with increase in stimulus strength. The later occurring component of the EPSC is carried through N-methyl-D-aspartate (NMDA) receptor-operated channels but disappears under either the NMDA antagonist 2-amino-5-phosphonovaleric acid (APV) or the non-NMDA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). These findings indicate that the late component of the SCC-evoked EPSC is polysynaptic: predominantly non-NMDA receptor-mediated SCC inputs excite CA1 neurons that recurrently excite each other by predominantly NDMA receptor-mediated synapses. These recurrent connections are normally silent but become active after CPT treatment, leading to enhancement of the late component of the EPSC. The activity of these connections is maintained for at least 2 hr after CPT removal. When all functional NMDA receptors are blocked by dizocilpine maleate (MK-801), subsequent application of CPT leads to a partial reappearance of NMDA receptor-mediated EPSCs evoked by SCC stimulation, indicating that latent NMDA receptors are recruited. Altogether, these findings indicate the existence of a powerful system of NMDA receptor-mediated synaptic contacts in SCC input to hippocampal CA1 pyramidal neurons and probably also in reciprocal connections between these neurons, which in the usual preparation are kept latent by activity of A1 receptors.