Timing and magnitude of early Aptian extreme warming: Unraveling primary δO variation in indurated pelagic carbonates at Deep Sea Drilling Project Site 463, central Pacific Ocean

In order to elucidate early Aptian marine paleotemperature evolution across the period of enhanced organic carbon (C_org)-burial [Oceanic Anoxic Event (OAE) 1a], stable isotope analyses were performed on pelagic limestones at Deep Sea Drilling Project Site 463, central Pacific Ocean. The δ¹⁸O data exhibit a distinct anomaly by ~ − 2‰ spanning the OAE 1a interval (i.e., a ~ 6 m-thick, phytoplanktonic C_org-rich unit constrained by magneto-, bio- and δ¹³C stratigraphy). Elucidation of paleotemperature significance of the δ¹⁸O shift is made by taking account of recent Sr/Ca evidence at the same section, which revealed that geochemical signals in carbonate-poor lithologies are relatively unaltered against burial diagenesis. By discriminating δ¹⁸O values from carbonate-poor samples (CaCO₃ contents = 5–30 wt.%), it appears that an abrupt rise in sea-surface temperatures (SSTs) by 8 °C (= − 1.7‰ shift in δ¹⁸O) occurred immediately before OAE 1a, whereas a cooling mode likely prevailed during the peak C_org-burial. In terms of its stratigraphic relationship as to the C_org-rich interval and to a pronounced negative δ¹³C excursion, as well as its timescale, the observed SST rise resembles those associated with the Paleocene–Eocene thermal maximum and, more strikingly, Jurassic Toarcian OAE. This observation is consistent with the hypothesis that these paleoenvironmental events were driven by a common causal mechanism, which was likely initiated by the greenhouse effect via massive release of CH₄ or CO₂ from the isotopically-light carbon reservoir and terminated by a negative productivity feedback.     

Pleistocene paleoenvironmental evolution at continental middle latitude inferred from carbon and oxygen stable isotope analysis of ostracodes from the Guadix-Baza Basin (Granada, SE Spain)

A representative paleoenvironmental reconstruction of continental middle latitude from ca. 2 my to the upper part of Middle Pleistocene (279 ± 77 ky) was obtained from the carbon and oxygen stable isotopes analyzed in ostracode shells (Cyprideis torosa) recovered in the Guadix-Baza Basin (SE Spain), an intramontaneous closed depression filled by alluvial and lacustrine sediments. This study was performed along a 356-m-thick composite section, dated previously by paleomagnetism and the amino acid racemization method. δ¹³C and δ¹⁸O profiles reflected changes in temperature, the evaporation/infill ratio in the water bodies and the amount of rain. δ¹³C is also affected by changes in plant biomass: periods with high δ¹³C and δ¹⁸O values are associated with warm and dry regimes, and with less vegetation, which, in some cases, coincide with the development of displacive gypsum crystals, whereas low δ¹³C and δ¹⁸O values correlate with cold and humid episodes, which cause more vegetation biomass and, therefore, increasing the input of isotopically light carbon. Intermediate δ¹⁸O values are linked to temperate dry or humid episodes when they coincide with high or low δ¹³C values, respectively. 86 paleoclimatic events were distinguished in the Pleistocene record from the δ¹³C and δ¹⁸O profiles. From both the statistical analysis of the geochemical data and the geological observations, four Cold and Humid Long Periods (low δ¹⁸O) and four Warm and Dry Long Periods (high δ¹⁸O) were defined. This differs with respect to the paleoclimatological behavior established for the Northern Hemisphere where during cold periods (glacial), no water was available while permafrost conditions persisted, whereas in warm episodes (interglacial), higher precipitation rates occurred. Good correspondences between the Guadix-Baza Basin paleoclimatic record and a marine oxygen-isotope sequence, two continental cores and other long Mediterranean paleoenvironmental records (pollen sequences from Israel) were found, which suggested that climate changes in the Guadix-Baza Basin were in tune with global climatic changes.     

Temporal and spatial variability of the oxygen isotopic composition of massive corals from the South China Sea: Influence of the Asian monsoon

Coral colonies of Porites lutea and P. lobata were collected from areas to the east and south offshore of Hainan Island, South China Sea. Oxygen isotope ratios, ¹⁸O/¹⁶O, were analyzed along the major axis of growth at a resolution of 25–28 samples within an annual band from three colonies, giving data series lengths of 15, 20 and 30 years. Coral δ¹⁸O correlates well with sea surface temperature (SST) throughout most years, particularly when the Asian winter monsoon prevails over the region. Due to the same seasonal phases of SST and sea surface salinity (SSS), it is estimated that most of the seasonal features of coral δ¹⁸O are controlled by changes in SST with a significant contribution of SSS. This indicates the importance of temperature, as determined by the Asian winter monsoon, as a control on seasonal coral δ¹⁸O variations in the South China Sea. Given the fact that annual SSS maxima show minor inter-annual changes, the inter-annual change of annual coral δ¹⁸O maximum mainly reflects the SST induced by the winter monsoon. While the coral δ¹⁸O is mainly controlled by SST, deviations of the δ¹⁸O from SST correlate statistically with sea surface salinity, particularly for summer extreme events when SST reaches its annual maximum with minor inter-annual change. Therefore, we suggest that the inter-annual variation of the annual coral δ¹⁸O minima is mainly controlled by seawater composition. Seawater composition analysis indicates that its δ¹⁸O and salinity are simultaneously affected by freshwater inputs primarily from precipitation, which is mainly supplied by the Asian summer monsoon. Thus seasonal alternations of the winter and summer monsoon mainly control the coral δ¹⁸O, thereby allowing reconstruction of these monsoonal variables. The three coral records consistently reveal clear inter-decadal trends in δ¹⁸O — a gradual increase from 1968 to 1987, and a subsequent decrease from 1987 to 2003. These inter-decadal trends are roughly consistent with salinity changes — but not with temperature and precipitation, suggesting that seawater composition controlled by freshwater inputs from distant source areas, rather than from local precipitation, is responsible for the trends in seawater composition and coral δ¹⁸O over the last 30 years. Comparison of the three coral records indicates that spatial variations in coral δ¹⁸O coincide with variations in seawater salinity and local precipitation, but not with temperature. This confirms the dominant role of seawater composition, mainly controlled by monsoonal precipitation, on the spatial variability of coral δ¹⁸O in the South China Sea.     

Miocene to recent eolian dust record from the Southwest Pacific Ocean at 40° S latitude

A 14-meter long pelagic clay core recovered at Marlin Rise (40°00.531′S, 154°2.601′W; 4775 m water depth) in the Southwest Pacific Basin contains a record of eolian dust deposited since the early Miocene. Downcore analysis of detrital minerals reveals a dominantly eolian signature with relatively constant proportions of quartz, feldspar and illite and trace amounts of chlorite, kaolinite and smectite, consistent with a continental (loess-like) source region. Fish tooth Sr isotope stratigraphy reveals the base of the core to be 17.5 Ma, with low sedimentation rates (< 0.5 mm/kyr LSR) indicated for the interval 17.5 to 10 Ma; several hiatuses in deposition appear to be present upcore, but are beyond the age resolution of the fish teeth stratigraphy. These intervals are revealed as apparent discontinuities in the Sr isotope record, accompanied by pulses of anomalously rapid sedimentation at ~ 10 Ma, 6.7 Ma and 4.1 Ma. Bulk mass accumulation rates (MAR) are calculated at ~ 10 mg/cm²/kyr over the last 4 Myr, consistent with previously estimated Quaternary eolian flux rates to this part of the Pacific. Nd, Pb and Sr radiogenic isotopic compositions of the detrital mineral extract (< 38 µm) show no trends with age, while ⁴⁰Ar/³⁹Ar ages show an upcore younging trend (~180 Ma to ~150 Ma), in concert with a slight coarsening of eolian grain-size distributions. These ages likely reflect mixing of Mesozoic illite-dominated clay from at least two continental source areas: southeastern Australia (Murray–Darling Basin/Lake Eyre Basin) and New Zealand (South Island). The data indicate remarkable constancy of continental eolian sources exposed to weathering and dispersal at this latitude during the Neogene.     

Pollen-based quantitative reconstructions of Holocene climate variability in NW Romania

A modern analogue technique is applied to two high-resolution pollen sequences from NW Romania to provide the first quantitative evidence for winter, summer and annual temperatures and for precipitation across the Holocene in this region.

The pollen-based climate reconstructions allow the identification of four main intervals: i) an early, less stable period between 11,700 and 11,200 cal. yr BP; (ii) generally stable conditions between 11,200 and 8300 cal. yr BP with winter and annual temperatures and precipitation higher than at present, and summer temperatures about the same; (iii) lower winter and annual temperatures, and higher summer temperatures and precipitation between 8000 and 2400 cal. yr BP; (iv) warmer winter and annual temperatures and lower precipitation for the last 2400 years, whereas summer temperatures became cooler at Steregoiu and remained stable at Preluca Tiganului.

The pollen-based climate reconstructions at the two sites show similar patterns in annual and winter temperatures and precipitation changes during the Holocene, but the trends appear to be less consistent for summer temperatures.

Our pollen-based reconstructions revealed several short-term climatic oscillations during the Holocene, the strongest of which occur between 10,300–10,100, 8300–8000, 6800–6400, 5100–4900, 4000–3600 and 3200–3000 cal. yr BP.     

Miocene phosphorites from the Murray Ridge, northwestern Arabian Sea

Phosphorites from the Murray Ridge, NW Arabian Sea comprise nodules, bioclasts, and bone fragments. The nodules are made up of a homogeneous, light-colored phosphate nucleus consisting of Rivulariacean filamentous cyanobacteria and a thin dark-grey colored phosphate cortex showing abundant microbial filaments and microborings. The bioclasts comprise of  14–14.5 Ma old planktonic foraminifers, accepted as the time of deposition. Spherical to ovoid-shaped apatite microparticles resembling fossil bacteria are distinct components in the bioclasts. Bone fragments exhibit apatite fillings. The nodules and bone fragments consist entirely of carbonate fluorapatite (CFA) with low Al, K, and Th concentrations suggesting absence of continental detritus. Shale-normalized REE patterns of the samples support a seawater-derived composition. The highly uniform initial _Nd values of − 4.8 to − 5.1 are interpreted as the seawater value at the onset of phosphatization  14 Ma ago. In contrast, ⁸⁷Sr/⁸⁶Sr ratios show a large range of 0.709055 to 0.709124 corresponding to unusually young stratigraphic ages of  1 to 3 Ma. The data are interpreted as evidence for post-depositional Sr exchange of the recrystallizing phosphorites with fluids isotopically not much different from modern seawater. It is concluded that the phosphorites formed under oxic, shallow-water conditions where microbial populations assimilated phosphorus primarily from seawater and mediated precipitation of CFA during early diagenesis at the sediment–water interface on different substrates.     

Conceptual model of seagrass die-off in Florida Bay: Links to biogeochemical processes

Seagrasses are recognized as important plant communities in coastal estuaries and lagoons across both tropical and temperate climes; thus, large-scale seagrass die-off events worldwide are of general concern. In Florida Bay, at the southern terminus of the Florida peninsula, seagrass die-off events up to 4000 ha have been reported and smaller scale mortality events are noted annually. In the present study, we examined several hypothesized causative factors (high temperature, hypersalinity, sulfide toxicity) of seagrass (Thalassia testudinum) mortality in Florida Bay. To test sulfide effects, in situ sulfide production was stimulated by applying a labile carbon source (glucose) to sulfate reducers in the sediment at five sites across the bay (northeastern, northcentral, and southwestern basins). During the one year study, high temperature (32–36 °C) and salinity (> 50 psu) were recorded in the bay associated with a regional drought. We also experienced major seagrass die-off events at two of our southwestern bay sites. These field conditions provided an excellent opportunity to closely examine cause–effect relationships among stressors and die-off events in the field, and verify results of our previous mesocosm experiments. Even though glucose amendments stimulated porewater sulfides in bay sediments (4–8 mmol L^− 1), no significant differences in biomass, short shoot density or final growth rates were found between control and glucose plots. In addition, the highest growth rates and shoot densities were concomitant with maximum water column salinity (> 50 psu) and temperature (32–36 °C), when porewater sulfides were also in the millimolar range. Large-scale seagrass mortality events, encompassing  50% of the entire meadow at one site, occurred at southwestern bay sites when plants were down regulating (slower growth and shoot density), probably in response to shorter day length and lower temperature (30–34 to 23–26 °C) from October, 2004 to January, 2005. Sulfate reduction rates (SRR) were also 2-fold higher in the southwestern (214–488 nmol cm^− 3 d^− 1) versus northcentral and northeastern (97–240 nmol cm^− 3 d^− 1) bay sites, possibly limited by labile carbon, which we found to stimulate SRR 3-fold in northeastern and northcentral bay sites (461–708 nmol cm^− 3 d^− 1) and 4-fold at southwestern bay sites (1211–2036 nmol cm^− 3 d^− 1). Based on a synthesis of the field data reported herein, our mesocosm experiments to date, and contributions by others, we present a conceptual model of seagrass die-off in Florida Bay outlining a cascade of stressors, stimulated by P enrichment, which leads to high O₂ consumption in the system triggering a seagrass die-off event.     

IL-10 is up regulated in early and transitional stages in vervet monkeys experimentally infected with Trypanosoma brucei rhodesiense

IL-10 has been suggested as a possible parameter for human African trypanosomiasis stage determination. However, conclusive experimental studies have not been carried out to evaluate this, which is a prerequisite before a potential test can be validated in humans for diagnostic purposes. We used the vervet monkey model of trypanosomiasis to scrutinize IL-10 in blood and cerebrospinal fluid (CSF). Five adult males were experimentally infected with T. b. rhodesiense. The infected animals became anemic and exhibited weight loss. Parasitemia was patent after 3 days and fluctuated around 3.7 × 10⁷ trypanosomes/ml throughout the experimental period. The total CSF white cell counts increased from pre-infection means around 3 cells/μl to a peak of 30 cells/μl, 42 days post-infection (DPI). IL-10 was not detectable (< 2 pg/ml) in serum prior to infection. IL-10 serum concentrations increased to 273 pg/ml 10 DPI coinciding with the first peak of parasitemia. Thereafter the levels declined to a mean value of 77 pg/ml 34 DPI followed by a significant rise to a second peak of 304 pg/ml (p < 0.008) 42 DPI. There was no detectable IL-10 in CSF. IL-10 synthesis is thus stimulated both in the early and transitional stages of experimental trypanosomiasis. That IL-10 is produced in early stage disease is an interesting finding unlikely to be detected in humans where it is difficult to determine the exact time of infection. The IL-10 peak observed on day 42 of infection might indicate onset of parasite neuroinvasion coinciding with a peak in white blood cell counts in the blood and CSF.     

A simple in-vitro 'wet-plate' method for mass production of Phytophthora nicotianae zoospores and factors influencing zoospore production

A simple in-vitro ‘wet-plate’ method for mass-producing Phytophthora nicotianae zoospores at ≥ 1.0 × 10⁶ zoospores/ml is described. Temperature critically affected zoospore production; 22 °C was optimum, while 36 °C was completely inhibitory. Zoospores being the most important propagule of P. nicotianae, temperature of recycled irrigation water may be manipulated to reduce diseases in irrigated nursery crops.     

The effect of intravenous PACAP38 on cerebral hemodynamics in healthy volunteers

PACAP38 is an endogenous peptide located in trigeminal perivascular nerve fibers in the brain. It reduces neuronal loss and infarct size in animal stroke models and has been proposed a candidate substance for human clinical studies of stroke. The effect on systemic hemodynamics and regional cerebral blood flow (rCBF) is not well understood. We here present the first study of the effect of PACAP38 on cerebral hemodynamics in humans.

PACAP (10 pmol kg^− 1 min^− 1) or placebo (0.9% saline) was infused for 20 min into 12 healthy young volunteers in a cross over, double blind study. rCBF was measured with SPECT and ¹³³Xe inhalation and mean blood flow velocity in the middle cerebral artery was measured with transcranial Doppler ultrasonography. End tidal partial pressure of CO₂ (P_etCO₂) and vital parameters were recorded throughout the 2 hour study period.

PACAP38 decreased rCBF in all regions of interest (ROIs) by  3–10%, though not uniformly significant. P_etCO₂ decreased significantly during PACAP38 infusion compared to placebo (P = 0.032), peak decrease was 8.9 ± 3.8%. After correction for P_etCO₂, rCBF remained unchanged in most ROIs. Heart rate increased 61.9 ± 22.4% (P < 0.0001 vs. placebo).

These findings suggest that PACAP38 has no major direct effect on rCBF in healthy volunteers. The marked increase in heart rate and the reduction in rCBF caused by decreased P_etCO₂ are important dose-limiting factors to consider in future clinical studies.     

Stable isotopic variations in modern herbivore tooth enamel, plants and water on the Tibetan Plateau: Implications for paleoclimate and paleoelevation reconstructions

Stable isotope analyses of fossil teeth and other authigenic minerals have been used to reconstruct the paleoenvironment and paleoelevation of the Tibetan Plateau. The accuracy of such reconstructions is limited by the lack of a comprehensive modern comparative database from the region. We analyzed the carbon and oxygen isotopic compositions (δ¹³C and δ¹⁸O values) of tooth enamel from modern herbivores, the δ¹³C values of grasses and the δ¹⁸O values of water samples collected from various elevations within the Tibetan Plateau to examine their relationships with modern environment/elevation. The δ¹³C values of enamel samples from horses, yaks and goats display a narrow range of variation, with a mean of − 10.7 ± 1.4‰ (n = 301), indicating that these modern herbivores were feeding predominantly on C3 plants, consistent with the current dominance of C3 vegetation in the region. Some of the samples have δ¹³C values between − 7.3 and − 10‰. Although these higher δ¹³C values could suggest consumption of some C4 plants by the animals, the lack of significant seasonal δ¹³C variations within individual teeth indicates that these higher enamel δ¹³C values are due to consumption of C3 plants experiencing water stress and/or some CAM plants rather than C4 plants. Our data show that the conservative “cut-off” δ¹³C value for a pure C3 diet within the Tibetan Plateau should be − 8‰ for modern herbivores and − 7‰ (or even − 6.5‰) for fossils if the region was as arid in the past as today. In contrast to the small intra-tooth δ¹³C variations within individual teeth, serial enamel samples display large intra-tooth δ¹⁸O variations, reflecting seasonal variations in the δ¹⁸O of meteoric water. The mean δ¹⁸O values of tooth enamel from yaks and horses show a strong correlation with water δ¹⁸O values, confirming that the δ¹⁸O of tooth enamel from obligate drinker generally tracks the δ¹⁸O of meteoric water. Unfortunately, elevation alone cannot explain most of the variance in the δ¹⁸O of precipitation and tooth enamel, suggesting that quantitative reconstruction of the paleoelevation of the Tibetan Plateau using re-constructed δ¹⁸O values of paleo-meteoric water from fossil enamel or other oxygen-bearing minerals is not warranted. For a given environment, horses have the lowest enamel–δ¹⁸O values while goats display the highest enamel–δ¹⁸O values among the species studied. The large inter-species δ¹⁸O variations are likely due to differences in physiology and diet/drinking behavior of the animals. This underscores the importance of species-specific studies when interpreting δ¹⁸O data of fossil mammalian teeth in a stratigraphic sequence as a record of paleoclimate changes.     

Simulation of the molecular and electronic structure of heterofullerenes C55Y5 (Y=Si, Ge, Sn, B, Al, N, P, SiH, GeH, SnH) and their η-π-complexes with Li by the MNDO method

Qualitative estimates of the relative stability of hypothetical heterofullerenes C₅₅Y₅ (Y=Si, Ge, Sn, B, Al, N, P, SiH, GeH, SnH) and some η⁵-π-complexes LiC₅₅Y₅ were carried out by the MNDO method. Atoms Y (or groups XH) are assumed to substitute those C atoms in fullerene C₆₀ which are located at the -positions of a separated pentagonal face (pent^*) of this polyhedral molecule. It is shown that the spin densities in radicals C₅₅Y₅ (Y=SiH, GeH, SnH, B, Al, N, P) are localized on the separated pentagon atoms and the Li-pentagonal face (Li-pent^*) bonds in η⁵-π-complexes of these radicals with the Li atom are considerably stronger than Li-pent^* bonds in complexes [η⁵-π-LiC₆₀]⁺ and [η⁵-π-LiC₆₀] of unsubstituted C₆₀. In addition, it is established that the Li-pent^* bond energies in η⁵-π-complexes LiC₅₅B₅ and LiC₅₅Al₅ exceed the energy of the Li-pent^* bond in the η⁵-π-complex LiC₆₀H₅ studied earlier. In contrast, the energies of similar bonds for Y=N, P are close to the energy of the Li-pent^* bond in the η⁵-π-complex LiC₆₀H₅.     

A 36,000-yr vegetation history from the Peloncillo Mountains, southeastern Arizona, USA

A 36,200 cal yr B.P. vegetation history was developed from macrofossils and pollen from 55 packrat middens from 1287 to 1442 m elevation in the Peloncillo Mountains of southeasternmost Arizona, USA. Today, these elevations are dominated by semidesert grassland with a mixture of Chihuahuan and Sonoran Desert shrubs, including an eastern disjunct population of jojoba (Simmondsia chinensis). From 36,200 to 15,410 cal yr B.P., rocky areas just above large, pluvial lakes that occupied what are now dry playas supported Pinus edulis, Juniperus osteosperma, Juniperus cf. coahuilensis, Quercus cf. turbinella and a rich understory of summer-flowering C₄ annuals and grasses, indicating abundant summer rains and mild winters. After  15,410 cal yr B.P., P. edulis declined in abundance and disappeared briefly at 13,925 cal yr B.P., coincident with expansion of more xeric species and paleohydrological evidence for regional aridity during the Bølling–Allerød warm interval. P. edulis rebounded briefly during the Younger Dryas at 12,405 cal yr B.P. before disappearing along with other mesic woodland species sometime after 12,100 cal yr B.P. The few middens dating from the early to middle Holocene (10,000–4000 yr B.P.) indicate wetter conditions than today at 7790 cal yr B.P. followed by a general drying trend. The 35 middens from the late Holocene detail the sequential arrival of desertscrub species as vegetation became more modern in character.     

Interactions between thiamine and large anions. Crystal structures of (H-thiamine)[Pt(SCN)4] · 3H2O and (H-thiamine)[Pt(SCN)6] · H2O

The reaction of thiamine with K₂Pt^IICl₄ and with Pt^IVCl₄ in the presence of excess NaSCN in aqueous solution gave thiamine salts, (H-thiamine)[Pt(SCN)₄] · 3H₂O (1) and (H-thiamine)[Pt(SCN)₆] · H₂O (2), respectively, structures of which have been determined by X-ray diffraction. The thiamine molecule adopts the usual F conformation in each salt. In 1, [Pt(SCN)₄]²⁻ ions act as large planar spacers in the crystal lattice and interact scarcely with thiamine, except for a hydrogen bonding with the terminal hydroxy O(5γ). Instead, water molecules form two types of host–guest-like interactions with the pyrimidine and the thiazolium moieties of a thiamine molecule, one being a C(2)–Hwaterpyrimidine bridge and the other being an N(4′)–Hwaterthiazolium bridge. In 2, despite the much larger ion size, octahedral [Pt(SCN)₆]²⁻ ions form a C(2)–Hanionpyrimidine bridge and an N(4′)–Hanionthiazolium bridge. An additional hydrogen bonding between the anion and the terminal O(5γ) of thiamine creates a hydrogen-bonded macrocyclic ring {thiaminium–[Pt(SCN)₆]²⁻}₂, a supramolecule.     

Quantification of some active compounds in air samples at pharmaceutical workplaces by HPLC

Workers involved in the manufacture of drug substances may be exposed to active pharmaceuticals by inhalation of drug dusts or droplets which has been considered the main exposure route. The proposed HPLC method allowed to determine sulpiryde, hydroxyurea and dyprophylline in the concentration range of 0.01–0.187 mg/m³, 0.001–0.08 mg/m³ and 0.01–0.40 mg/m³ for sulpiryde, hydroxyurea and dyprophylline, respectively, when 480 L of air sample was collected on the glass fibre filters. Sulpiryde was extracted with a solvent system consisting of acetonitrile–phosphate buffer at pH 3 (85:15, v/v), while the best efficiency of extraction for hydroxyurea and dyprophylline was achieved using water. HPLC analysis of sulpiryde with fluorescence detection was more sensitive (LOD = 3.1 μg/L) in comparison with UV detection (LOD = 84.4 μg/L).     

A substitutive substrate for measurements of beta-ketoacyl reductases in two fatty acid synthase systems

Bacterial β-ketoacyl-ACP reductase (FabG) and the β-ketoacyl reductase domain in mammalian fatty acid synthase (FAS) have the same function and both are rendered as the novel targets for drugs. Herein we developed a convenient method, using an available compound ethyl acetoacetate (EAA) as the substitutive substrate, to measure their activities by monitoring decrease of NADPH absorbance at 340 nm. In addition to the result, ethyl 3-hydroxybutyrate (EHB) was detected by HPLC analysis in the reaction system, indicating that EAA worked effectively as the substrate of FabG and FAS since its β-keto group was reduced. Then, the detailed kinetic characteristics, such as optimal ionic strength, pH value and temperature, and kinetic parameters, for FabG and FAS with this substitutive substrate were determined. The K_m and k_cat values of FabG obtained for EAA were 127 mM and 0.30 s^− 1, while those of this enzyme for NADPH were 10.0 μM and 0.59 s^− 1, respectively. The corresponding K_m and k_cat values of FAS were 126 mM and 4.63 s^− 1 for EAA; 8.7 μM and 4.09 s^− 1 for NADPH. Additionally, the inhibitory kinetics of FabG and FAS, by a known inhibitor EGCG, was also studied.     

Ordovician meteoric carbon and oxygen isotopic values: implications for the latitudinal variations of ancient stable isotopic values

Columnar and clear blocky calcite cement from a Middle Ordovician carbonate succession in east Tennessee is interpreted as meteoric in origin. Columnar and clear blocky calcite from this succession does not show extremely large ¹³C depletions reported from meteoric phases of younger rocks. Meteoric fluid δ¹⁸O values calculated from clear blocky calcite are 2 to 3‰ more negative than approximately coeval sea water; a relationship typical of modern, low-latitude, coastal meteoric water. Comparison with meteoric δ¹⁸O values from Ordovician units elsewhere suggests that the geographic distribution of these values may be broadly similar to that observed today. Therefore, we tentatively suggest that geographic distribution of meteoric δ¹⁸O values during both icehouse and greenhouse eras are similar.     

Relationship of environmental changes in central Sri Lanka to possible prehistoric land-use and climate changes

A radiocarbon-dated pollen-analysed peat sequence from the Horton Plains (> 2000 m a.s.l.), in central Sri Lanka, together with physical and chemical parameters (organic carbon, mineral magnetics, carbon isotopes and phytoliths), indicates major environmental changes during the last 24,000 years. The results suggest that a mobile life form, i.e. a hunter–forage culture, predominated in an open landscape, associated with xerophytic vegetation, e.g. Chenopodium spp. at  17.5 ka BP. Incipient management of cereal plants and slash-and-burn techniques seem to have prevailed between 17.5 and 13 ka BP, which was indigenous and associated with grazing. Evidence of systematic cereal cultivation in the form of oat and barley pollen grains is found from the late Pleistocene ( 13 ka BP). This is the earliest evidence of farming activities noted in Sri Lanka as well as in south Asia. After 13 ka BP, cereal cultivation was associated with an increase in humidity. With a later abrupt increase in aridity, agricultural land-use decreased from  8 to  3.6 ka BP, when the area appears to have been almost deserted. After a severe middle Holocene arid phase (i.e. 5.4–3.6 ka BP), the agricultural activity with a limited extension was again initiated by  2.9 ka BP. During the next  900 years, cultivation ceased allowing the upper montane rain forest to dominate. Between 0.2 and 0.15 ka BP, new phases of agricultural activities were undertaken and potato cultivation took place lately, between 1950 and 1969 AD.