Bottom water oxygenation history in southeastern Arabian Sea during the past 140 ka: Results from redox-sensitive elements

The concentrations of multiple redox-sensitive elements such as Re, U, Mo, Cd, V, Sb, and Tl were determined in sediments from the southeastern Arabian Sea (9°21′N: 71°59′E) to understand the bottom water oxygenation history throughout the past 140 ka. The enrichment of redox-sensitive elements (Re, U, Cd and Sb) above average crustal abundances suggests that the Last Glacial Maxima (17.48 ka), stadials of Marine Isotope Stage (MIS)-5 (5b and 5d) and Glacial Termination (GT)-II (133 ka) were associated with suboxic bottom water conditions. Sediments deposited during these suboxic conditions show the highest Re content (up to 54 ppb normalized to a carbonate free basis) which is highly enriched over average continental crust (0.4 ppb) and these sediments appear to be the major sink for the global mass balance estimation. Marine Isotope Stages 1, 3, 4 and interstadials of MIS-5 (5a, 5c & 5e) were all associated with near-oxic conditions. Overall, the lack of enrichment of Mo and V above crustal abundance, and a high Re/Mo (ppm/ppm) ratio (avg. 18.2 × 10^− 3) suggest that sediments of the southeastern Arabian Sea never contained free H₂S during the last 140 ka. These changes in the bottom water oxygen content can be related to the oceanic circulation pattern during this time and in part are reflected in relationships between the timing of redox changes and paleoproductivity proxies.     

Linkages between surface and deep circulations in the southern Japan Sea during the last 27,000 years: Evidence from planktic foraminiferal assemblages and stable isotope records

We analyzed planktic foraminiferal assemblages, oxygen and carbon isotope records, and the presence or absence of laminations to reconstruct the paleoenvironments of the southern Japan Sea since the last glacial period. Data were collected from two well-dated cores. One core (water depth 999 m) included thinly laminated mud layers, the other (water depth 283 m) contained nonlaminated sediments. Tephrochronology and accelerator mass spectrometry ¹⁴C dating of 14 horizons revealed that the two cores contained continuous records of the last 27 cal kyr. A total of 13 planktic foraminiferal species belonging to six genera were identified in down-core samples. The typical indicators of the Tsushima Current water, Globigerinoides ruber, Neogloboquadrina dutertrei, Pulleniatina obliquiloculata, Globigerinoides tenellus, and Globigerinita glutinata occurred since 9.3 cal kyr BP. Neogloboquadrina incompta, which was the dominant species in the Tsushima Current region of the modern Japan Sea, first occurred at 8.2 cal kyr BP and dominated the assemblage since 7.3 cal kyr BP. These results clearly indicate that the warm Tsushima Current started to inflow into the Japan Sea at 9.3 cal kyr BP, and the modern surface conditions in the southern Japan Sea were essentially established at 7.3 cal kyr BP. Our data and comparison of the presence or absence of laminated sediments in three locations from the southern Japan Sea suggest that deep circulation during the deglacial period was weaker than that at present. In addition, deep circulation in the modern Japan Sea, which supplies oxygen-rich water to the entire basin, started probably in association with the first inflow of the Tsushima Current beginning at 9.3 cal kyr BP.     

Subtropical Front fluctuations south of Australia (45°09′S, 146°17′E) for the last 130 ka years based on calcareous nannoplankton

Calcareous nannoplankton assemblages from a Late Quaternary deep-sea core (GC07; 46°09′S, 146°17′E) south of Australia provide information on regional palaeoceanography and palaeoclimate changes in the Southern Ocean, in particular the movement of the Subtropical Front for the past 130 ka years. Marine Isotope Stages 1–5 are identified through changes in calcareous nannoplankton assemblages, supported by ¹⁴C dates, and oxygen isotope and %CaCO data.Two distinct assemblages are recognised: a warm water assemblage with higher abundances of Calcidiscus leptoporus, Emiliania huxleyi, Helicosphaera.carteri, Syracosphaera pulchra, Gephyrocapsa caribbeanica and Gephyrocapsa oceanica; and, a cold water assemblage with higher abundances of Gephyrocapsa muellerae and Coccolithus pelagicus. Alternation between these two assemblages downcore in GC07 reflect movement of the Subtropical Front across the location and can be correlated to Marine Isotope Stages (MIS) 1–5. Sediments with a cold water assemblage indicate the position of the Subtropical Front equatorward of the site when transitional to sub-antarctic waters were overlying the site. Conversely sediments with a warm water assemblage indicate the Subtropical Front was poleward of GC07 when warmer, subtropical waters were over the site. MIS 1 and 5 are interpreted as warmer than MIS 3 (based on species composition) with the Subtropical Front more poleward than for MIS 3. During MIS 3 the Subtropical Front is interpreted as adjacent to or immediately poleward of GC07. Some species including C. leptoporus and C. pelagicus show negative covariance and are considered to be reliable species in identifying glacial and interglacial intervals in this region.Comparison with established biostratigraphy based on calcareous nannoplankton showed the datum event for the reversal between E. huxleyi and G. muellerae of 73 ka in transitional waters is not applicable in this region. The reversal between these two species occurs between 48 and 30 cm downcore in GC07 with a ¹⁴C date of 11 020 year BP at 49–48 cm, i.e. the reversal event is younger than this date.     

Foraminiferal oxygen and carbon isotopes during the last 34 kyr off northern Japan, northwestern Pacific

Oxygen and carbon isotopes of foraminifera were analyzed in core PC4, water depth 1366 m, off northern Japan, near the east side of the Tsugaru Strait (130 m depth) between the open northwestern Pacific Ocean and the Japan Sea. At present, the site is at the confluence of the Tsugaru Warm Current which flows eastwards out of the Sea of Japan through the Tsugaru Strait, the subarctic Oyashio Current and the subtropic Kuroshio Current. During the Last Glacial Maximum (LGM), the Oyashio Current penetrated further to the South and outflow from the Japan Sea was restricted by glacio-eustatic sea level lowering.The isotopic values of the planktic foraminifer Neogloboquadrina pachyderma (sinistral) and the benthic foraminifer Uvigerina akitaensis reflect rapid millennial-scale paleoceanographic changes between 34 and 6 ka. Hydrographic changes during deglaciation were related to events at high northern latitudes, but Holocene hydrographic changes were dominated by local effects, such as the development of the outflow of the Tsugaru Warm Current. High values of planktic δ¹⁸O during the LGM reflect the southward advance of the Oyashio Current. These values decreased by 0.3‰ from 19.4 to 18.9 ka, then increased by 0.5‰ at 18 ka, with highest values between 17.5 and 15 ka. The δ¹⁸O oscillations between 19.4 and 15 ka may reflect millennial-scale warm–cold oscillations during Heinrich event 1. Planktic microfossil data indicate that cold Oyashio waters flowed from the northwestern Pacific into the Japan Sea via the Tsugaru Strait between 17 and 16 ka, consistent with the occurrence of the highest planktic δ¹⁸O values in core PC4. Planktic δ¹⁸O values rapidly decreased by 0.9‰ at 15 ka, possibly reflecting the effects of both a rapid increase in fresh water flux and rising temperatures in the subarctic North Pacific. During the Younger Dryas, cold event planktic δ¹⁸O values increased by 0.5‰, followed by a gradual decrease by 1‰ from the early to middle Holocene, reflecting a gradual increase in eastward outflow via the Tsugaru Strait with sea level rise. Both planktic and benthic foraminiferal δ¹³C values oscillated between 34 and 10 ka, at relatively large amplitudes (about 0.5‰), then remained relatively stable during the last 10 kyr. Several negative planktic and benthic ( − 0.7‰) δ¹³C excursions were present in sediment dated between the precipitation of secondary carbonates during episodic methane release possibly associated with methane release from continental margin sediments.     

Foraminiferal oxygen and carbon isotopes during the last 34 kyr off northern Japan,northwestern Pacific

Oxygen and carbon isotopes of foraminifera were analyzed in core PC4, water depth 1366 m, off northern Japan, near the east side of the Tsugaru Strait (130 m depth) between the open northwestern Pacific Ocean and the Japan Sea. At present, the site is at the confluence of the Tsugaru Warm Current which flows eastwards out of the Sea of Japan through the Tsugaru Strait, the subarctic Oyashio Current and the subtropic Kuroshio Current. During the Last Glacial Maximum (LGM), the Oyashio Current penetrated further to the South and outflow from the Japan Sea was restricted by glacio-eustatic sea level lowering.The isotopic values of the planktic foraminifer Neogloboquadrina pachyderma (sinistral) and the benthic foraminifer Uvigerina akitaensis reflect rapid millennial-scale paleoceanographic changes between 34 and 6 ka. Hydrographic changes during deglaciation were related to events at high northern latitudes, but Holocene hydrographic changes were dominated by local effects, such as the development of the outflow of the Tsugaru Warm Current. High values of planktic δ¹⁸O during the LGM reflect the southward advance of the Oyashio Current. These values decreased by 0.3‰ from 19.4 to 18.9 ka, then increased by 0.5‰ at 18 ka, with highest values between 17.5 and 15 ka. The δ¹⁸O oscillations between 19.4 and 15 ka may reflect millennial-scale warm–cold oscillations during Heinrich event 1. Planktic microfossil data indicate that cold Oyashio waters flowed from the northwestern Pacific into the Japan Sea via the Tsugaru Strait between 17 and 16 ka, consistent with the occurrence of the highest planktic δ¹⁸O values in core PC4. Planktic δ¹⁸O values rapidly decreased by 0.9‰ at 15 ka, possibly reflecting the effects of both a rapid increase in fresh water flux and rising temperatures in the subarctic North Pacific. During the Younger Dryas, cold event planktic δ¹⁸O values increased by 0.5‰, followed by a gradual decrease by 1‰ from the early to middle Holocene, reflecting a gradual increase in eastward outflow via the Tsugaru Strait with sea level rise. Both planktic and benthic foraminiferal δ¹³C values oscillated between 34 and 10 ka, at relatively large amplitudes (about 0.5‰), then remained relatively stable during the last 10 kyr. Several negative planktic and benthic (∼ − 0.7‰) δ¹³C excursions were present in sediment dated between the precipitation of secondary carbonates during episodic methane release possibly associated with methane release from continental margin sediments.     

1-Methoxy-, 1-deoxy-11-hydroxy- and 11-Hydroxy-1-methoxy-Δ-tetrahydrocannabinols: new selective ligands for the CB2 receptor

Three series of new cannabinoids were prepared and their affinities for the CB₁ and CB₂ cannabinoid recptors were determined. These are the 1-methoxy-3-(1′,1′-dimethylalkyl)-, 1-deoxy-11-hydroxy-3-(1′,1′-dimethylalkyl)- and 11-hydroxy-1-methoxy-3-(1′,1′-dimethylalkyl)-Δ⁸-tetrahydrocannabinols, which contain alkyl chains from dimethylethyl to dimethylheptyl appended to C-3 of the cannabinoid. All of these compounds have greater affinity for the CB₂ receptor than for the CB₁ receptor, however only 1-methoxy-3-(1′,1′-dimethylhexyl)-Δ⁸-THC (JWH-229, 6e) has effectively no affinity for the CB₁ receptor (K_i=3134±110 nM) and high affinity for CB₂ (K_i=18±2 nM).     

Sea surface environment inferred from planktonic foraminifera in the southern South China Sea since the last glacial period

Detailed analyses of planktonic foraminifera at Site 17964 from the southern South China Sea (SCS) disclose that warm-water species have a higher percentage during the Holocene, while temperate-water species have a higher content for the last glacial period. Therefore, the sea surface temperature (SST) is a main factor that affects the foraminiferal assemblage at this site. A remarkable faunal variation at Site 17964 is recognized for Pulleniatina obliquiloculata over the last glacial–interglacial periods: higher P. obliquiloculata content during the glacial period and abrupt drop at the beginning of Termination I (16.5–15 kyr B.P.). The characteristic P. obliquiloculata variation can be correlated with other sites in the southern SCS and thus can be adopted as a stratigraphic tool in the region. A detailed analysis of Orbulina universa shell morphometrics at Site 17964 shows the test size from 0.83 to 1.45 mm and the shell porosity up to 36.7%, much larger than those in the Indian and Atlantic Oceans, which indicates a warmer and less saline surface water in the equatorial–tropical western Pacific. The diameter and shell porosity of O. universa increased from the last glacial to the Holocene, corresponding to the increase of SST recorded by the U^k₃₇ alkenone index. A higher correlation coefficient (89%) between the O. universa test size and SST implies that intraspecific O. universa test size be used as an index of the sea surface temperature in the South China Sea.     

High-resolution sea surface temperature and salinity dynamics in the northern Okinawa Trough over the last 24 kyr

Based on the high-resolution Mg/Ca and oxygen isotope ratio (δ¹⁸O) of planktonic foraminifera Globigerinoides ruber, sea surface temperature (SST) and salinity (SSS) were reconstructed in Core PC-1 from the northern Okinawa Trough during the last 24 kyr. From the last glacial maximum to Holocene, SST varied from 20.2°C to 24.6°C. Millennial-scale climatic events of the SST during the last glacial, such as the Heinrich events, Bølling-Allerød warming, and Younger Dryas, have been identified, which are synchronous with the climate changes in the North Atlantic, suggesting a teleconnection between the northwestern Pacific and the North Atlantic. During the last 24 kyr, the SSS variation can be divided into three parts: (1) during 21–15.5 ka, there was a significantly low SSS; (2) during 15.5–11.7 ka, the SSS increased obviously; (3) since 11.7 ka, the SSS is relatively stable. In order to discuss the main factors influencing the SSS in the northern Okinawa Trough, the relative abundance of Pulleniatina obliquiloculata and the oxygen isotope difference between the northern and middle Okinawa Trough (Δδ¹⁸O_sw) have been used to indicate the intensity of the Kuroshio Current and Changjiang freshwater discharge, respectively. The Δδ¹⁸O_sw result shows that there is a large amount of Changjiang freshwater emptied into the northern Okinawa Trough during 18–15.5 ka, which is caused by the subtropical monsoon rain band lingering in the lower reaches of the Changjiang River drainage, supporting the Jet Transition Hypothesis. As the Kuroshio Current strengthened since 15.5 ka as indicated by the increased relative abundance of P. obliquiloculata, the variation of Kuroshio Current became the more important contribution to the SSS in the study region. The results of our study indicate that the key factor influencing the SSS in the northern Okinawa Trough is variable during the last 24 kyr.     

Use of a vinyl phosphonate analog of ATP as a rotationally constrained probe of the C5′---O5′ torsion angle in ATP complexed to methionine adenosyl transferase

An analog of adenosine 5′-triphosphate (ATP) was synthesized in which the C4′---C5′---O---P^α system is replaced by a trans C4′---CH=CH---P^α system. In the form of 1:1 complexes with Mg, this analog and its counterpart with a C4′---CH₂---CH₂---P^α system were linear competitive inhibitors, with respect to MgATP, of the MAT-II (normal tissue) and MAT-T (hepatoma tissue) forms of rat ATP: -methionine-S-adenosyltransferase (MAT); K_m(ATP)/K_i values ranged from 0.4 to 2.4. 2′-Deoxy-ATP was a weak substrate, K_m(ATP)/K_m = 0.035, of MAT-II and a weak competitive inhibitor, K_m(ATP)/K_i = 0.07, of MAT-T. These findings, together with interactions of the MAT forms with other substrates and inhibitors, indicate that binding of ATP to these transferases is accompanied by little rotation about the C5′---O5′ bond, and that C4′ and P^α are in a trans-type relationship in enzyme-bound ATP.     

Late Quaternary millennial-scale variability in pelagic aragonite preservation off Somalia

In order to better understand Late Quaternary pelagic aragonite preservation in the western Arabian Sea we have investigated a high-resolution sediment core 905 off Somalia. Pteropod preservation is enhanced in times of reduced monsoon-driven productivity, indicated by low amounts of C_org and low barium to aluminium (Ba/Al) ratios. All periods corresponding to Heinrich events in the North Atlantic are represented by maxima in shell preservation of the common pteropod Limacina inflata (LDX values < 2, except for H5-equivalent with a poorer shell preservation, LDX > 2.66). Good shell preservation is also found during stadials at 52.1–53.2, 36, 33.2, and 31.9 ka. Relative abundance of pteropods and their fragments in the coarse fraction reaches maxima during Marine Isotope Stage (MIS) 5.2, during time-equivalents of Heinrich events 4–6 and in stadials at  53,  42.5, and 41.4 ka.On longer time scales, the pteropod abundance corresponds to the ‘Indo-Pacific carbonate preservation type’ with poor preservation during interglacials and better preservation during glacials. Late MIS 5 to early MIS 4 sections (84.1–64.8 ka) and the Late Holocene interval (6.5–0 ka) of core 905 contain only traces of pteropods. The early Holocene (9.2–6.5 ka) part is characterized by low pteropod amounts. Between 64.8 and 43.4 ka strong fluctuations occur and an intermediate average relative pteropod abundance is revealed. Between 43.4 and 9.2 ka the highest amounts in relative pteropod abundance in core 905 are observed. Besides the regional monsoonal influence on deepwater chemistry, changes in deepwater circulation occurring on glacial/interglacial and stadial/interstadial time scales might have affected pteropod preservation. However, it remains elusive whether 1) deep water formation in the Arabian Sea, 2) inflow of Glacial North Atlantic Intermediate Water or 3) change in water mass properties of the Circumpolar Deep Water (which is the water mass currently bathing this site) contributed to the observed pteropod preservation pattern.     

Reconstruction of Indian monsoon variability over the past 230,000 years: Planktic foraminiferal evidence from the NW Arabian Sea open-ocean upwelling area

We determined the faunal composition and total number of tests (#/g) of planktic foraminifera (> 125 μm) in core KH00-05 GOA 6 near Oman in order to decipher monsoon-induced variability of oceanographic productivity in the open-ocean upwelling area in the northwest Arabian Sea. The core contains a continuous record of sedimentation over the last 230 kyr, with the age model based on oxygen isotope and accelerator mass spectrometry ¹⁴C dates. We focused on species (Globigerina bulloides and Globigerinita glutinata) typical for SW monsoonal upwelling and species typical for NE monsoon conditions (Neogloboquadrina incompta, Neogloboquadrina dutertrei, Globigerinoides ruber, and Globigerinoides sacculifer). The changes in relative abundance of these monsoonal indicators suggest that the open-ocean upwelling area was dominated by the SW monsoon during interglacial periods, but by the NE monsoon during glacial periods.Increases in total test abundance during glacial periods confirmed that the NE monsoon rather than SW monsoon contributes largely to planktic foraminiferal productivity in this area. We argue that three types of circumstances resulted in high productivity, with nine high productivity events occurring at a 23-kyr frequency. The first type caused high productivity events at 102 and 199 ka (interglacial periods), characterized by the dominance of upwelling species, indicating high productivity during strong SW monsoons, correlated with high July insolation at 45° N. An exceptional high productivity event occurred at 37 ka during interglacial marine isotope stage (MIS) 3, with contributions from both SW and NE monsoons. The second type of high productivity event occurred at 61, 147, and 175 ka, during glacial periods, characterized by dominance of NE monsoon species, and correlated with low January insolation at 45° N. In addition, a high productivity event at 85 ka (interglacial period) also was induced by enhanced NE monsoons. The last two high productivity events occurred during transitional periods from glacial to interglacial (MIS 6/5.5 and 2/1), were characterized by the replacement of NE monsoon species with upwelling species, and corresponded to abrupt climate warming, suggesting that they are related to both accelerated SW monsoon systems and reduced NE monsoon systems.     

A new nonhydrolyzable reactive cGMP analogue, (Rp)-guanosine-3',5'-cyclic-S-(4-bromo-2,3-dioxobutyl)monophosphorothioate, which targets the cGMP binding site of human platelet PDE3A

The amino acids involved in substrate (cAMP) binding to human platelet cGMP-inhibited cAMP phosphodiesterase (PDE3A) are identified. Less is known about the inhibitor (cGMP) binding site. We have now synthesized a nonhydrolyzable reactive cGMP analog, Rp-guanosine-3′,5′-cyclic-S-(4-bromo-2, 3-dioxobutyl)monophosphorothioate (Rp-cGMPS-BDB). Rp-cGMPS-BDB irreversibly inactivates PDE3A (K_I = 43.4 ± 7.2 μM and k_cart = 0.007 ± 0.0006 min⁻¹). The effectiveness of protectants in decreasing the rate of inactivation by Rp-cGMPS-BDB is: Rp-cGMPS (K_d = 72 μM) > Sp-cGMPS (124), Sp-cAMPS (182) > GMP (1517), Rp-cAMPS (3762), AMP (4370 μM). NAD⁺, neither a substrate nor an inhibitor of PDE3A, does not protect. Nonhydrolyzable cGMP analogs exhibit greater affinity than the cAMP analogs. These results indicate that Rp-cGMPS-BDB targets favorably the cGMP binding site consistent with a docking model of PDE3A-Rp-cGMPS-BDB active site. We conclude that Rp-cGMPS-BDB is an effective active site-directed affinity label for PDE3A with potential for other cGMP-dependent enzymes.     

UK37沉积地层记录:三门湾海表温度(SST)和EI Ni(n)o现象及其对大型底栖动物生命活动的影响

应用U^K37估算三门湾（1916～2003年）表层海水温度,SST波动范围在15．97～18．00℃之间,年平均为17．03℃,此计算值比当年实测海水全年平均温度低3．52℃,与秋季海水实测温度相接近。研究显示出,三门湾的EINino事件在大尺度上与东太平洋一样,均受制于气候影响因素,但在变化尺度上又受到地理位置和地方性气候（季风）的影响,事件在形式和年代上相互对应,但其颤动幅度远不如东太平洋强烈。同时通过比较EINino期间（2003／2002）和非EINino期间（2006／2005）大型底栖生物的群落结构变动信号、生物量、栖息密度以及物种多样性等,研究显示出三门湾若干大型底栖生物对EINino事件产生响应迹象,若干大型底栖生物对EINino的响应主要是通过海洋环流的影响来体现生命和生态效应的,主要表现在改变了底栖生物种类数和多样性、以及生命活动及栖息密度分布模式。在EINino影响下,台湾暖流人侵势力加强,2003／2002年底栖生物群落种类数减少与海流人侵及盐度密切相关;通过与同海域浮游动物对比研究,三门湾海域浮游动物和底栖生物对EINino的生态响应均较大,前者可能与三门湾海域水域较浅,外海暖水从底部人侵改变水温和盐度,直接影响底栖生物的生态环境,致使种类数大大减少有关;而后者由于人侵暖水强度增大,携带大量暖水性浮游动物,呈现出在EINino时期浮游动物种类数、生物量和丰度有偏高趋势。     

Using species-specific paleotemperature equations with foraminifera: a case study in the Southern California Bight

Species-specific paleotemperature equations were used to reconstruct a record of temperature from foraminiferal δ¹⁸O values over the last 25 kyr in the Southern California Bight. The equations yield similar temperatures for the δ¹⁸O values of Globigerina bulloides and Neogloboquadrina pachyderma. In contrast, applying a single paleotemperature equation to G. bulloides and N. pachyderma δ¹⁸O yields different temperatures, which has been used to suggest that these species record the surface-to-thermocline temperature gradient. In Santa Barbara Basin, an isotopically distinct morphotype of G. bulloides dominates during glacial intervals and yields temperatures that appear too cold when using a paleotemperature equation calibrated for the morphotype common today. When a more appropriate paleotemperature equation is used for glacial G. bulloides, we obtain more realistic glacial temperatures. Glacial–interglacial temperature differences (G–I ΔT) calculated in the present study indicate significant cooling (8–10°C) throughout the Southern California Bight during the last glacial maximum (LGM). The magnitude of glacial cooling varies from 8°C near the middle of the Southern California Bight (Tanner Basin and San Nicolas Basin) to 9°C in the north (Santa Barbara Basin) and 9.5–10°C in the south (Velero Basin and No Name Basin). Our temperature calculations agree well with previous estimates based on the modern analog technique. In contrast, studies using N. pachyderma coiling ratios, U^k′₃₇ indices, and transfer functions estimate considerably warmer LGM temperatures and smaller G–I ΔT.     

Environmental changes clarified by pollen and diatom proxy records in the sedimentary archive of the northwestern Japan Sea during last 21.0 kyr

High-temporal resolution pollen and diatom records from the northwestern Japan Sea document environmental changes over the last 21.0 kyr. Vegetation and climate changes were evaluated using the forest-steppe (SFI) and the pollen temperature (T_p) indices. The highest SFI occurred between ca. 21.0 ka and 16.6 ka and indicates the presence of a relatively dry climate and large areas of forest-steppe in the region. Boreal forests covered the mountain slopes. The broad-leaved trees survived in refugia located in lower mountain belts. Beginning ca. 16.6 ka, SFI decreases, while T_p increases, especially between ca. 11.0 ka and 5.7 ka. However, variations in these indices indicate fluctuating climates during the deglaciation. Significant vegetation changes occurred in the Holocene. Mixed deciduous forests with a predominance of Quercus became widely present beginning ca. 9.8 ka. The area of forest-steppe was reduced occurring only in local habitats. Pinus became one of the most common taxa in the forest ca. 5.3 ka. The geographic features of the coring area have determined in the past the persistence throughout the record of cold-water diatom flora. Cold-water diatoms have dominated in both cool and warm intervals; however, a small increase in the percentage and species diversity of warm-water diatoms was noted for warming. Low sea level during the Last Glacial Maximum (LGM) and early Holocene changed the general patterns in the sea circulation and in the vectors of the longshore currents, which transported the waters formed in the shallow areas of the northeastern and northern parts of the Japan Sea. A slight increase in sublittoral benthic diatoms indicates a lowered sea level during the LGM. The increase in sublittoral planktonic diatoms reflects a gradual rise in sea level during the Bølling–Allerød (BA) and Younger Dryas (YD). A greater component of oceanic diatom species at Holocene indicates the inflow of Pacific waters across both the Tsushima and Tsugaru straits. This study of pollen and diatom records demonstrates a clear response to climatic fluctuations and sea level changes in the Japan Sea during the Late Pleistocene and Holocene.     

Effects of 4-acetamido-4′-isothiocyano-2,2′-disulfonic stilbene on ion transport in turtle bladders

The disulfonic stilbene (4-acetamido-4′-isothiocyano-2,2′-disulfonic stilbene) is found to be more potent than acetazolamide as an anion transport inhibitor in the turtle bladder, but less potent than acetazolamide as a carbonic anhydrase inhibitor. The anion-dependent (HCO₃^-−, Cl⁻) moeity of the short-circuiting current is eliminated by 4-acetamido-4′-isothiocyano-2,2′-disulfonic stibene, but only after its addition to the serosal bathing fluid. Whereas 4-acetmido-4′-isothiocyano-2,2′-disulfonic stilbene has no effect om Na⁺transport across the bladder, it is more potent than ouabain as an inhibitor of microsomal (Na⁺+K⁺)-ATPase of both turtle bladder and eel electric organ.     

3-(1′,1′-Dimethylbutyl)-1-deoxy-Δ-THC and related compounds: synthesis of selective ligands for the CB2 receptor

The synthesis and pharmacology of 15 1-deoxy-Δ⁸-THC analogues, several of which have high affinity for the CB₂ receptor, are described. The deoxy cannabinoids include 1-deoxy-11-hydroxy-Δ⁸-THC (5), 1-deoxy-Δ⁸-THC (6), 1-deoxy-3-butyl-Δ⁸-THC (7), 1-deoxy-3-hexyl-Δ⁸-THC (8) and a series of 3-(1′,1′-dimethylalkyl)-1-deoxy-Δ⁸-THC analogues (2, n=0–4, 6, 7, where n=the number of carbon atoms in the side chain−2). Three derivatives (17–19) of deoxynabilone (16) were also prepared. The affinities of each compound for the CB₁ and CB₂ receptors were determined employing previously described procedures. Five of the 3-(1′,1′-dimethylalkyl)-1-deoxy-Δ⁸-THC analogues (2, n=1–5) have high affinity (K_i=<20 nM) for the CB₂ receptor. Four of them (2, n=1–4) also have little affinity for the CB₁ receptor (K_i=>295 nM). 3-(1′,1′-Dimethylbutyl)-1-deoxy-Δ⁸-THC (2, n=2) has very high affinity for the CB₂ receptor (K_i=3.4±1.0 nM) and little affinity for the CB₁ receptor (K_i=677±132 nM).

Scheme 3. (a) (C₆H₅)₃PCH₃⁺ Br⁻, n-BuLi/THF, 65°C; (b) LiAlH₄/THF, 25°C; (c) KBH(sec-Bu)₃/THF, −78 to 25°C then H₂O₂/NaOH.     

Thyroid hormone: Aldosterone antagonism in cultured epithelial cells

Thyroid hormone (T₃) has been demonstrated to inhibit the action of aldosterone on sodium transport in toad urinary bladder and rat kidney. We have exammined the effect of T₃ on aldosterone action and specific nuclear binding in cultured epithelial cells derived from toad urinary bladder. In cell line TB6-C, addition of 5·10⁻⁸ M T₃ to culture media for up to 3 days results in no change in short-circuit current or transepithelial resistance. This concentration of T₃ completely inhibits the maximal increase in short-circuit current in response to 1·10⁻⁷ M aldosterone. The inhibition can be demonstrated with 18 h preincubation or with simultaneous addition of T₃ and aldosterone. The half-maximal concentration for the inhibition of the aldosterone effect is approx. 5·10⁻⁹ M T₃. T₃ has no effect on cyclic AMP-stimulated short-circuit current in these cells. The effect of T₃ on nuclear binding of [³H]aldosterone was examined using a filtration assay with data analysis by at least-squares curve-fitting program. Best fit was obtained with a model for two binding sites. The dissociation constants for the binding were K′_d1 = (0.82 ± 0.36)·10⁻¹⁰ M and K′_d2 = (3.2±0.60)·10⁻⁸ M.The half-maximal concentration for aldosterone-stimulated sodium transport in these cells is approx. 1·10⁻⁸ M. Analysis of nuclear aldosterone binding in cells preincubated for 18 h with 5·10⁻⁸ M T₃ showed a K′_d1 = (0.15 ± 0.10)·10⁻¹⁰ M and K′_d2 = (3.5 ± 0.10)·10⁻⁸ M. We conclude that T₃ i action of aldosterone on sodium transport at a site after receptor binding in the nucleus.     

Sea surface temperature changes during May and August in the western Arabian Sea over the last 22 kyr: Implications as to shifting of the upwelling season

In the western Arabian Sea (WAS), the highest seasonal sea surface temperature (SST) difference presently occurs between May and August. In order to gain an understanding on how monsoonal upwelling modulates the SST difference between these two months, we have computed SST for the months of May and August based on census counts of planktonic foraminifers by using the artificial neural network (ANN) technique. The SST difference between May and August exhibits three distinct phases: i) a moderate SST difference in the late Holocene (0–3.5 ka) is attributable to intense upwelling during August, ii) a minimum SST difference from 4 to 12 ka is due to weak upwelling during the month of August, and iii) the highest SST difference during the last glacial interval (19 to 22 ka) with high Globigerina bulloides % could have been caused by the occurrence of a prolonged upwelling season (from May through July) and maximum difference in the incoming solar radiation between May and August. Overall, variations in the SST difference between May and August show that the timing of intense upwelling in the Western Arabian Sea over the last 22 kyr has been variable over the months of June, July and August.     

Hydroxylation of naringin by Trichoderma harzianum to dramatically improve its antioxidative activity

Transforming naringin using the mycelium of Trichoderma harzianum CGMCC 1523 produces two metabolites, 3′,4′,5,7-tetrahydroxy flavanone-7-rhamnoglucoside (3′-OHN) and 3′,4′,5′,5,7-pentahydroxy flavanone-7-rhamnoglucoside (3′,5′-DOHN), both of which were characterized by ESI–MS, ¹H NMR and ¹³C NMR analyses. The time course of the biotransformation by T. harzianum showed that 3′-OHN and 3′,5′-DOHN appeared simultaneously at 6 h, and the conversion yield (32.6%) of 3′,5′-DOHN was higher (10.6%) than that of 3′-OHN at 56 h. The optimal biotransformation temperature was 30 °C, the optimal pH was 5.0, and the optimal concentration of naringin was 400 mg/l. The bigger volume of biotransformation mixture and lower shaking speed did not favor hydroxylation reactions. The radical scavenging activity of naringin at 2000 μM was 11.1%, whereas activity of 3′-OHN at 100 μM could reach 38.4%, which is 68.6 times more than naringin. Antioxidative activity of 3′,5′-DOHN was increased 13.5% at 100 μM compared to 3′-OHN.