Do 2 H and 18 O in leaf water reflect environmental drivers differently?

We compiled hydrogen and oxygen stable isotope compositions (δ2 H and δ18 O) of leaf water from multiple biomes to examine variations with environmental drivers. Leaf water δ2 H was more closely correlated with δ2 H of xylem water or atmospheric vapour, whereas leaf water δ18 O was more closely correlated with air relative humidity. This resulted from the larger proportional range for δ2 H of meteoric waters relative to the extent of leaf water evaporative enrichment compared with δ18 O. We next expressed leaf water as isotopic enrichment above xylem water (Δ2 H and Δ18 O) to remove the impact of xylem water isotopic variation. For Δ2 H, leaf water still correlated with atmospheric vapour, whereas Δ18 O showed no such correlation. This was explained by covariance between air relative humidity and the Δ18 O of atmospheric vapour. This is consistent with a previously observed diurnal correlation between air relative humidity and the deuterium excess of atmospheric vapour across a range of ecosystems. We conclude that 2 H and 18 O in leaf water do indeed reflect the balance of environmental drivers differently; our results have implications for understanding isotopic effects associated with water cycling in terrestrial ecosystems and for inferring environmental change from isotopic biomarkers that act as proxies for leaf water.

Inverse altitude effect disputes the theoretical foundation of stable isotope paleoaltimetry.

Stable isotope paleoaltimetry that reconstructs paleoelevation requires stable isotope (δD or δ18O) values to follow the altitude effect. Some studies found that the δD or δ18O values of surface isotopic carriers in some regions increase with increasing altitude, which is defined as an "inverse altitude effect" (IAE). The IAE directly contradicts the basic theory of stable isotope paleoaltimetry. However, the causes of the IAE remain unclear. Here, we explore the mechanisms of the IAE from an atmospheric circulation perspective using δD in water vapor on a global scale. We find that two processes cause the IAE: (1) the supply of moisture with higher isotopic values from distant source regions, and (2) intense lateral mixing between the lower and mid-troposphere along the moisture transport pathway. Therefore, we caution that the influences of those two processes need careful consideration for different mountain uplift stages before using stable isotope palaeoaltimetry.

How do precipitation events modify the stable isotope ratios in leaf water at Lhasa on the southern Tibetan Plateau?

Serving as a medium between source water and cellulose, leaf water contributes to the isotope ratios (δ18O, δ2H) of plant organic matter, which can be used for paleoclimate reconstruction. This study is the first to examine the diurnal variations in the δ18O and δ2H of leaf water on the southern Tibetan Plateau. The δ18O and δ2H of leaf water were relatively low when precipitation events occurred. In particular, 18O and 2H of leaf water became extremely depleted 5 h after the precipitation event. Our findings demonstrate that precipitation can modify the isotope ratios of leaf water from external and internal causes. First, precipitation events affect meteorological elements, lead to decreases in leaf transpiration, and immediately weaken the isotope enrichment of leaf water ('rapid effect' of precipitation). Second, precipitation events affect the internal plant-soil water cycle process, causing the plant to preferentially use deeper soil water, and the corresponding isotope ratios of leaf water exhibit extremely low values 5 h after precipitation events ('delay effect' of precipitation). This study suggests that researchers need to be cautious in separating the signals of precipitation and hydrological processes when interpreting isotope records preserved in tree-ring cellulose archives from the Tibetan Plateau.

Microbial diversity in the snow, a moraine lake and a stream in Himalayan glacier.

The microbial diversity and abundance in surface snow at different altitudes (5300 and 5504 m above sea level), a moraine lake and a glacial stream in the Yala Glacier on the southern slope of the Himalayas were investigated through a 16S rRNA gene clone library and flow cytometry approaches. Cell abundance in different habitats changed from 1.1 × 10(4) to 25 × 10(4) cells mL(-1), with the highest abundance in the moraine lake and the lowest abundance in the snow at 5504 m. Microbial communities in the snow were significantly different from those in the moraine lake and stream, although they were similar within snow and within the aquatic habitats. The two snow libraries were both dominated by Cyanobacteria, which accounted for about half of the total, followed by the Alphaproteobacteria and Firmicutes. The moraine lake and stream libraries were dominated by the Bacteroidetes and Betaproteobacteria, followed by the Actinobacteria. The results indicated that snow and water were highly diverse systems even in the same glacier. Microbial communities in the snow on the Yala Glacier were distinctly different from those in the East Rongbuk Glacier on the northern slope of Himalayas. However, microbes in the moraine lakes at two glaciers had similar community features. The snow habitat was easily affected by various environmental factors, while the aquatic habitats were comparatively stable in different glaciers.

Organic contamination in online laser-based plant stem and leaf water isotope measurements for pre-extracted samples.

Water stable isotopes have been widely used as natural tracers to investigate soil-plant-atmosphere interactions. Recent developments in induction module cavity ring-down spectroscopy (IM-CRDS) have made it possible to rapidly complete isotope analyses, and to combust co-extracted organic compounds at the same time. However, the agreement between IM-CRDS and isotope ratio mass spectrometry (IRMS) analyses has generally been poor and was primarily attributable to spectral interference of IM-CRDS. Here we evaluated the impacts of organic contamination on the isotope ratios using IM-CRDS with two different methods. No spectral interference was observed for solid samples measured directly by IM-CRDS, whereas clear organic contamination occurred in isotope analyses for pre-extracted plant stem and leaf samples. Our results demonstrate that IM-CRDS can fully combust co-extracted organic compounds by in-line oxidation in the direct measurement of solid samples, although this may not guarantee that the IM-CRDS can obtain better isotopic data than IRMS. It may be risky to evaluate the performance of IM-CRDS by measuring pre-extracted water samples because cryogenic vacuum distillation is likely to introduce extra organic compounds, which may not be fully removed during subsequent IM-CRDS measurement. In addition, spectral variables are useful for post-processing corrections.

Atmospheric transport and accumulation of organochlorine compounds on the southern slopes of the Himalayas, Nepal.

Studies have been devoted to the transport and accumulation of persistent organic pollutants (POPs) in mountain environments. The Himalayas have the widest altitude gradient of any mountain range, but few studies examining the environmental behavior of POPs have been performed in the Himalayas. In this study, air, soil, and leaf samples were collected along a transect on the southern slope of the Himalayas, Nepal (altitude: 135-5100 m). Local emission occurred in the lowlands, and POPs were transported by uplift along the slope. During the atmospheric transport, the HCB proportion increased from the lowlands (20%) to high elevation (>50%), whereas the proportions of DDTs decreased. The largest residue of soil POPs appeared at an altitude of approximately 2500 m, and may be related to absorption by vegetation and precipitation. The net deposition tendencies at the air-soil surface indicated that the Himalayas may be a 'sink' for DDTs and PCBs.

[Expression and prognostic value of proliferating cell nuclear antigen in hepatocellular carcinoma patients received preoperative transcatheter arterial chemoembolization].

BACKGROUND & OBJECTIVE: Proliferating cell nuclear antigen (PCNA) could indicate cell proliferation of hepatocellular carcinoma (HCC), while the impact of preoperative transcatheter arterial chemoembolization (TACE) on cell proliferation of HCC is still uncertain. This study was to investigate the expression and prognostic value of PCNA in HCC patients underwent preoperative TACE. METHODS: The expression of PCNA in 91 specimens of HCC with preoperative TACE (TACE group) and 50 specimens of HCC without preoperative TACE (non-TACE group) was detected by immunohistochemistry. The expression of PCNA between the 2 groups after stratification were compared. Correlation of PCNA expression to tumor recurrence was analyzed. RESULTS: PCNA was expressed in cell nuclei. The positive rates of PCNA were 67.0% in TACE group and 66.0% in non-TACE group (P>0.05). In patients with disseminated nodules, portal vein invasion and poorly differentiated tumor, the positive rates of PCNA were significantly lower in TACE group than in non-TACE group, respectively. In patients who underwent curative resection after preoperative TACE, the positive rates of PCNA were significantly higher in recurrence group than in non-recurrence group (77.8% vs. 47.1%, P<0.05). The 1-, 3-, and 5-year disease-free survival rates were significantly higher in PCNA-negative group than in PCNA-positive group (83.2% vs. 55.8%, 62.1% vs. 31.8%, and 53.2% vs. 23.6%, P<0.01). CONCLUSIONS: Preoperative TACE inhibit cell proliferation of the HCC with disseminated nodules, portal vein invasion or poor differentiation. The expression of PCNA is closely correlated to postoperative recurrence of HCC patients who underwent preoperative TACE.

[The value of TissueLink hemostatic sealer in hepatectomy for hepatocellular carcinoma].

BACKGROUND & OBJECTIVE: Managing the liver stumps reliably is an important guarantee for the accomplishment of hepatectomy. This study was to explore the value of TissueLink hemostatic sealer in hepatectomy for hepatocellular carcinoma (HCC), and evaluate its effects in extending incisal edge and reducing recurrence rate. METHODS: TissueLink hemostatic sealer was used on the liver stumps during hepatectomy for 20 patients (study group); whereas, conventional suturing of the vessels and bile ducts was performed in 28 patients (control group). Peri-operative serum alanine aminotransferase (ALT), total bilirubin, hospitalization period and complication occurrence were observed and compared. RESULTS: The amount of operative bleeding and the amount of post-operative abdominal cavity drainage were significantly lower in study group than in control group [(412.50+/-122.34) ml vs. (530.36+/-151.13) ml, P=0.006; (285.50+/-43.59) ml vs. (347.86+/-67.62) ml, P=0.001]. Three and 7 days after operation, serum ALT levels were significantly lower in study group than in control group [(152.36+/-93.32) U/ml vs. (246.19+/-159.85) U/ml, P=0.015; (56.63+/-21.59) U/ml vs. (96.46+/-47.97) U/ml, P=0.009]; serum total bilirubin levels were significantly lower in study group than in control group [(25.93+/-9.63) micromol/L vs. (40.12+/-16.54) micromol/L, P=0.004; (17.25+/-7.22) micromol/L vs. (39.63+/-19.06) micromol/L, P=0.001]. Hospitalization period was significantly shorter in study group than in control group [(10.5+/-1.5) days vs. (12.9+/-2.8) days, P=0.002]. The occurrence rate of complications was lower in study group than in control group. On CT image after operation, an annular zone of necrosis in the liver was found in most patients of study group. CONCLUSIONS: TissueLink hemostatic sealer is a safe device to manage the liver stumps in hepatectomy. It has less damage on liver function after operation, and can shorten hospitalization period and reduce the occurrence of post-operative complications.

[Expression and clinical significance of VEGF and MMP-9 in hepatocellular carcinoma].

BACKGROUND & OBJECTIVE: Vascular endothelial growth factor (VEGF) and matrix metalloproteinase-9 (MMP-9) are related to invasiveness, angiogenesis, and prognosis of malignancies. However, the reports on the results of VEGF and MMP-9 in estimating the prognosis of hepatocellular carcinoma (HCC) patients are different. This study was to investigate the expression and clinical value of VEGF and MMP-9 in HCC patients. METHODS: The expression of MMP-9 and VEGF in 80 specimens of HCC was detected by immunohistochemistry. Of the 80 patients, 48 had tumor recurred within 2 years after operation. Correlations of the expression of MMP-9 and VEGF to clinicopathologic features were analyzed. Cox regression model was used to analyze the recurrence risk factors after hepatectomy. RESULTS: MMP-9 and VEGF were expressed in cytoplasm. The positive rates of MMP-9 and VEGF were significantly higher in recurrent group than in non-recurrent group (50.0% vs. 15.6%, and 87.5% vs. 59.4%, P<0.05). The expression of MMP-9 was positively correlated to that of VEGF (rs=0.36, P<0.01), and both were positively correlated to recurrence of HCC (P<0.01). The 1-, 2-, and 3-year tumor-freely survival rates were significantly higher in VEGF-negative group than in VEGF-positive group (85.7% vs. 58.0%, 71.4% vs. 38.9%, and 66.3% vs. 33.9%, P <0.01), and were significantly higher in MMP-9-negative group than in MMP-9-positive group (72.4% vs. 50.0%, 63.8% vs. 14.1%, and 55.5% vs. 14.1%,P <0.01). Multivariate analysis revealed that preoperative disseminated nodules, tumor micrometastasis, and the expression of MMP-9 and VEGF were independent recurrence risk factors. CONCLUSION: The expression of MMP-9 and VEGF in HCC tissues is closely correlated to the recurrence of HCC after hepatectomy, and could be used to estimate the risk of postoperative recurrence of HCC.