Serum concentrations of gonadotropins and steroid hormones of Neophocaena phocaenoides asiaeorientalis in middle and lower regions of the Yangtze River

As a relatively isolated and unique freshwater population, the Yangtze finless porpoise (Neophocaena phocaenoides asiaeorientalis) is the most endangered subpopulation of this species. The objective of this study was to improve our understanding of their reproductive endocrinology by measuring (radioimmunoassay) serum concentrations of FSH, LH, estradiol (E-2), progesterone (P-4) and testosterone (T-2) in free-ranging animals. Blood samples were collected from 66 Yangtze finless porpoises (41 males and 25 females) captured in the middle and lower reaches of the Yangtze River. Based on significant variation of serum T-2 concentrations in males with body length (BL) > 138 cm, we inferred that they were mature; in these animals, there were significant seasonal variations in serum T-2 concentrations, with the highest concentrations in March and April (502.0 +/- 319.8 ng/dL, mean +/- S.D.) and the lowest in December (79.4 +/- 83.2 ng/dL). Serum T-2 concentrations positively correlated with serum concentrations of LH and weakly correlated with serum concentrations of E-2, whereas there was a significant negative correlation between serum LH and FSH concentrations in males > 138 cm. The smallest apparently pregnant female porpoise had a BL of 130 cm. Serum P-4 concentrations ranged from 13.2 to 112.4 ng/mL (43.9 +/- 28.3 ng/mL) in pregnant females, and fluctuated under 1.0 ng/mL in non-pregnant females with BL > 130 cm. Serum LH concentrations were significantly higher in non-pregnant females > 130 cm versus those females < 130 cm. To our knowledge, this is the first study of endocrine-related maturity and seasonal breeding characteristics of the Yangtze finless porpoise. (c) 2006 Elsevier Inc. All rights reserved.

The impact of planktivorous fishes on microcystin concentrations in Meiliang Bay, Lake Taihu, China

In an eight-month enclosure experiment in Meiliang Bay of Lake Taihu, a shallow subtropical lake in China, silver carp (Hypophthalmichthys molitrix) and bighead carp (Aristichthys nobilis) collectively reduced cyanobacterial biomass. Microcystin concentration was six times higher in the 0.35 km(2) control enclosure (without fish) than in two similar-sized enclosures that had been stocked with both carp species. Furthermore, toxic Microcystis spp. increased microcystin production when exposed to silver carp and bighead carp.

Effects of salt stress on carbohydrate metabolism in desert soil alga Microcoleus vaginatus Gom.

The effects of salt stress on carbohydrate metabolism in Microcoleus vaginatus Gom., a cyanobacterium isolated from desert algal crusts, were investigated in the present study. Extracellular total carbohydrates and exopolysaccharides (EPS) in the culture medium produced by M. vaginatus increased significantly during the growth phase and reached a maximum during the stationary phase. The production of extracellular carbohydrates also significantly increased under higher salt concentrations, which was attributed to an increase in low molecular weight carbohydrates. In the presence of NaCl, the production of cellular total carbohydrates decreased and photosynthetic activity was impaired, whereas cellular reducing sugars, water-soluble sugars and sucrose content and sucrose phosphate synthase activity increased, reaching a maximum in the presence of 200 mmol/L NaCl. These parameters were restored to original levels when the algae were transferred to a non-saline medium. Sodium and K+ concentrations of stressed cells decreased significantly and H+-ATPase activity increased after the addition of exogenous sucrose or EPS. The results suggest that EPS and sucrose are synthesized to maintain the cellular osmotic equilibrium between the intra- and extracellular environment, thus protecting algal cells from osmotic damage, which was attributed to the selective exclusion of cellular Na+ and K+ by H+-ATPase.

Changes in the concentrations of size-fractioned iron and related environmental factors in the northeastern part of lake Dianchi (China)

To observe changes in the concentrations of size-fractionated iron and related environmental factors, experiments were conducted in the northeastern part of the shallow eutrophic lake Dianchi (China) from March 2003 to February 2004. Iron concentrations were measured for three size fractions: particulate iron (phi >0.22 mu m), colloidal iron (phi = 0.025-0.22 mu m) and soluble iron (phi < 0.025 mu m), and environmental factors (physicochemical and biological factors) were synchronously analyzed. Results showed that size-fractionated iron and the related environmental factors all varied with season. Colloidal iron accounted for only 5-9% of total iron, while particulate and soluble iron each accounted for 40-50% of total iron. The results suggested that size-fractionated iron can transform into each other, especially the highly reactive colloidal iron. Significant linear correlations were found between iron in different size fractions, and significant correlations were also obtained between chlorophyll a and environmental factors, such as TN, TP and secchi depth. No significant correlation between iron and chlorophyll a was found in this study.

Mercury concentrations in Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis) from Eastern Dongting Lake, China

Mercury concentrations in some key tissues (liver, kidney, small intestine, stomach, blubber and brain) of five Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis), accidentally died in the Eastern Dongting Lake of China between 1998 and 2004, were investigated using Atomic Fluorescent Spectrometry (AFS). Total mercury (T-Hg) concentrations ranged between 0.17 to 181 mu g g wet weight. and varied significantly in different tissues. Liver is the most preferable target organ for mercury accumulation. although the highest T-Hg concentrations were not found exclusively in liver, but also in kidney and small intestine in some individuals. Moreover, it was demonstrated that mercury concentrations increased positively with age of the animals. However, the highest T-Hg concentrations in liver and kidney were both found in a 2-month-old calf, which implied that the transfer efficiency of mercury from mothers to babies in Yangtze finless porpoise is remarkable. And what is more important, it seems that the Yangtze finless porpoise in Eastern Donating Lake had much higher T-Hg levels than those reported for other Phocoenidae species. To be noticed, the T-Hg was accumulated tremendously from aquatic environment to the Yangtze finless porpoise's liver, reaching a bioaccumulation factor (BAF) of 4.3x10(5) in the Eastern Donating Lake ecosystem.

Effect of CO2 concentrations on the activity of photosynthetic CO2 fixation and extracelluar carbonic anhydrase in the marine diatom Skeletonema costatum

The growth and activity of photosynthetic CO2 uptake and extracellular carbonic anhydrase (CA(ext)) of the marine diatom Skeletonema costatum were investigated while cultured at different levels of CO2 in order to see its physiological response to different CO2 concentrations under either a low (30 mumol . m(-2) . s(-1)) or high (210 mumol . m(-2) . s(-1)) irradiance. The changes in CO2 concentrations (4-31 mumol/L) affected the growth and net photosynthesis to a greater extent under the low than under the high light regime. CAext was detected in the cells grown at 4 mumol/L CO2 but not at 31 and 12 mumol/L CO2, with its activity being about 2.5-fold higher at the high than at the low irradiance. Photosynthetic CO2 affinity (1/K-1/2(CO2)) of the cells decreased with increased CO2 concentrations in culture. The cells cultured under the high-light show significantly higher photosynthetic CO2 affinity than those grown at the low-light level. It is concluded that the regulations of CA(ext) activity and photosynthetic CO2 affinity are dependent not only on CO2 concentration but also on light availability, and that the development of higher CA(ext) activity and CO2 affinity under higher light level could sufficiently support the photosynthetic demand for CO2 even at low level of CO2.

Effects of CO2 concentrations on the freshwater microalgae, Chlamydomonas reinhardtii, Chlorella pyrenoidosa and Scenedesmus obliquus (Chlorophyta)

In order to investigate the possible impacts of increased atmospheric CO2 levels on algal growth and photosynthesis, the influence of CO2 concentration was tested on three planktonic algae (Chlamydomonas reinhardtii, Chlorella pyrenoidosa, and Scenedesmus obliquus). Increased CO2 concentration enhanced significantly the growth rate of all three species. Specific growth rates reached maximal values at 30, 100, and 60 muM CO2 in C. reinhardtii, C pyrenoidosa, and S. obliquus, respectively. Such significant enhancement of growth rate with enriched CO2 was also confirmed at different levels of inorganic N and P, being more profound at limiting levels of N in C pyrenoidosa and P in S. obliquus. The maximal rates of net photosynthesis, photosynthetic efficiency and light-saturating point increased significantly (p<0.05) in high-CO2-grown cells. Elevation of the CO2 levels in cultures enhanced the photoinhibition of C. reinhardtii, but reduced that of C pyrenoidosa and S. obliquus when exposed to high photon flux density. The photo-inhibited cells recovered to some extent (from 71% to 99%) when placed under dim light or in darkness, with better recovery in high-CO2-grown C. pyrenoidosa and S. obliquus. Although pH and pCO(2) effects cannot be distinguished from this study, it can be concluded that increased CO2 concentrations with decreased pH could affect the growth rate and photosynthetic physiology of C. reinhardtii, C. pyrenoidosa, and S. obliquus.

Moisture content in Dall's porpoise (Phocoenoides dalli) tissues: a reference base for conversion factors between dry and wet weight trace element concentrations in cetaceans

Concentration of trace elements measured by dry weight basis has become more commonly used in recent studies on cetaceans than wet weight basis, which was used more in earlier studies. Because few authors present moisture content data in their papers, it is difficult to compare the concentrations of trace elements between various studies. Therefore, we felt that it would be useful if a reference conversion factor (CF) for tissue types could be found to convert between wet weight and dry weight data on trace element concentrations. We determined the moisture contents of 14 tissues of Dall's porpoise (Phocoenoides dalli), and then, calculated the CF values for those tissues. Because the moisture content of each tissue differs from other tissues, it is necessary to use a specific CIF for each tissue rather than a general CF for several tissues. We have also found that CIF values for Dall's porpoise tissues are similar to the same tissues in other cetaceans. Therefore CF values from Dall's porpoise can be reliably used to convert between wet and dry weight concentrations for other cetacean tissues as reference data. (C) 2002 Elsevier Science Ltd. All rights reserved.

Effects of desiccation and CO2 concentrations on emersed photosynthesis in Porphyra haitanensis (Bangiales, Rhodophyta), a species farmed in China

The effects on photosynthesis of CO, and desiccation in Porphyra haitanensis were investigated to establish the effects of increased atmospheric CO2 on this alga during emersion at low tides. With enhanced desiccation, net photosynthesis, dark respiration, photosynthetic efficiency, apparent carboxylating efficiency and light saturation point decreased, while the light compensation point and CO2 compensation point increased. Emersed net photosynthesis was not saturated by the present atmospheric CO2 level (about 350 ml m(-3)). and doubling the CO2 concentration (700 ml m(-3)) increased photosynthesis by between 31% and 89% at moderate levels of desiccation. The relative enhancement of emersed net photosynthesis at 700 ml m(-3) CO2 was greater at higher temperatures and higher levels of desiccation. The photosynthetic production of Porphyra haitanensis may benefit from increasing atmospheric CO2 concentration during emersion.

Relationship between tissue concentrations of polycyclic aromatic hydrocarbons and DNA adducts in green-lipped mussels (Perna viridis)

Green-lipped mussels (Perna viridis) were collected from a site in Hong Kong which is relatively free from polycyclic aromatic hydrocarbon (PAH) contamination, and maintained in situ at this and three other sites with different degrees of PAH contamination. The transplanted mussels were retrieved after a 30-day field exposure. DNA adducts in the gill tissues were quantified, and tissue concentrations of benzo[a]pyrene as well as total PAHs (with potential carcinogenicity) determined for individual mussels. Results indicate that (1) tissue concentration of PAHs and adduct levels in mussels collected from a single site can be highly variable; and (2) adduct levels were related to tissue concentrations of benzo[a]pyrene as well as total PAHs of individual animals.

盐和有机物对氨基酸热力学性质的影响-NaCl氨基酸-葡萄糖-水体系

在278.15-318.15范围内，本文测定了以下四个无液接电池的电动势：Pt,H_2(g, 1 atm)|HCl(m)、X Mass% Glucose-H_2O|Ag-AgCl (A) Pt,H_2 (g, 1 atm)|G(m_1), HGCl (m_2), X Mass% Glucose-H_2O|Ag-AgCl (B) Pt,H_2 (g, 1 atm) |HCl (m), NaCl (M-m), X Mass% Glucose-H_2O|Ag-AgCl (C) Pt,H_2 (g, 1 atm)|G(m_1), HGCl (m_2), NaCl (M-m), X Mass% Glucose-H_2O|Ag-AgCl (D) 其中G为中性甘氨酸，NH_3CH_2COO~-, HGClm为甘氨酸的盐酸盐，为相应电解质的质量摩尔浓度，X为葡萄糖在葡萄糖-水混合溶剂中的质量百分数，M为恒定的离子强度且M = 1.0mol/kg。并且测定了Glucose-H_2O的密度和介电常数。利用传统的D-H公式外推法和基于Pitzer理论的多项式逼近法分别确定了电池的标准电动势E°_3、E°_3，以及甘氨酸的一级热力学解离1.0mol/kg）-葡萄糖-水-HCl的HCl无限稀释溶液为参考态，并将两种方法得到的结果作了比较。甘氨酸的一级热力学解离常数符合Harned-Robinson方程：pK = A_1/T + A_2 + A+3 T 本文讨论了盐和有机物对pK_1的影响，并根据前人及我们的工作，指出在极性质子溶剂中和在极性非质子溶剂中的pK_1对1/D作图，分别得到直线和曲线。同时讨论了混合溶剂中甘氨酸的一级解离过程的各个热力学量ΔG°，ΔH°，ΔS°，ΔCp°，并讨论HCl的迁移性质和有机物葡萄糖、盐对它们的影响。最后将不同混合溶剂中甘氨酸解离过程的迁移能，迁移熵等作了比较。

CeCl_3在NaCl溶液中对LC_4铝合金的缓蚀作用

本工作研究了CeCl_3在NaCl溶液中对LC_4铝合金（Al-Zn5.0/7.0-Mg1.3/2.8-Cu1.4/2.0-Cr0.10/0.25)的缓蚀作用。LC_4铝合金在NaCl溶液中腐蚀严重，腐蚀过程中有氢气析出，许多产物沉积在溶液底部，去膜后，光学显微显示，试样表面有很深的腐蚀坑。铝合金表面有很多缺陷，无氧化膜覆盖的铝成为活性中心，在NaCl溶液中做为阳极，铝合金中活性较低的杂质组分（如金属间化合物），突出氧化膜，在NaCl溶液中做为阴极，铝合金表面活性中心交替发生点蚀，腐蚀加重。LC_4铝合金在NaCl溶液中腐蚀的阴极去极化过程是氧的去极化。活性中心铝自溶解析氢，Cl~-在活性中心吸附，促进铝阳极溶解，氧去极化的慢步聚有扩散、吸附、电化学反应，控制步骤是扩散和吸附。LC_4铝合金在CeCl_3+NaCl溶液中腐蚀速度很底，腐蚀过程中极少有氢气极出，去膜后，光学显微显示，试样表面仍很均一，没有点蚀的迹象，Ce(+3)在阴极相表面吸附、沉积，阻碍氧的吸附，抑制阴极氧还原，降低腐蚀速度，铝腐蚀产生的H_2O_2可将Ce(+3)氧化到Ce(+4)，生成CeO_2：2Ce(OH)_3 + H_2O_2 = 2CeO_2 + 4H_2O在阴极相表面，H_2O_2将Ce(+3)氧化到Ce(+4)，消耗H_2O_2，消除H_2O_2对铝腐蚀的加速作用，进一步减慢活性中心铝阳极溶解的速度。LC_4铝合金在LaCl_3+NaCl溶液中的腐蚀速度下降，但局部腐蚀仍较严重，对析氢并无明显影响。La(+3)在阴极相表面吸附、沉积后，阻碍氧的吸附，抑制阴极氧还原，降低腐蚀速度，La(+3)不影响铝腐蚀产生的H_2O_2还原为OH~-的过程，H_2O_2对铝腐蚀的加速作用继续存在，不影响点蚀的孕育、发展，点蚀孔内铝自溶解析氢过程也不会受到影响。