Composition, mineralization potential and release risk of nitrogen in the sediments of Keluke Lake, a Tibetan Plateau freshwater lake in China.

The lakes distributed in the Tibetan Plateau constitute a lake group with the highest altitude, largest lakes and largest area in the world and are important in global climate and environmental effects. Freshwater lakes in the Tibetan Plateau possess high ecological values and high vulnerability. The migration and transformation of nitrogen in sediments are critical to lake ecosystems, but information on sedimentary nitrogen in the freshwater lakes in the Tibetan Plateau is limited. A case study was conducted in Keluke Lake, China, to reveal the effects of sedimentary nitrogen on water quality in plateau freshwater lakes. Nitrogen speciation, mineralization potential and release flux were analysed through a sequential extraction method, waterlogged incubation experiment and Fick's first diffusion law, respectively. The content of total nitrogen (TN) was 1295.75-6151.69 mg kg-1, and 94.2% of TN was organic nitrogen (ON). The contents of three nitrogen fractions were in the order of hydrolysable nitrogen > residual nitrogen > exchangeable nitrogen. Ammonia nitrogen ( N H 4 + - N ) was the main mineralization product, and hydrolysable ON was the most significant contributor. The sediments showed a great mineralization potential, with a potentially mineralizable nitrogen value of 408.76 mg N kg-1 of sediment, that was mainly affected by hydrolysable ammonium nitrogen. The N H 4 + - N diffusion flux ranged from 24.14 to 148.75 mg m-2 d-1, and the sediments served as an internal nitrogen source. Nitrogen release from sediments was considerably influenced by exchangeable ammonia nitrogen. The sediments in Keluke Lake pose a potential nitrogen release risk and threaten the water quality of the lake. The total content, speciation, mineralization of ON and the release flux at sediment-water interface should be considered comprehensively to evaluate the effects of nitrogen in sediments to water quality.

Experience of 1000 patients who underwent hepatectomy for small hepatocellular carcinoma.

BACKGROUND: Recently, the implementation of screening programs using alpha-fetoprotein (AFP) and ultrasonography in high risk populations has identified increasing numbers of patients with small hepatocellular carcinoma (small HCC). The aim of this study was to summarize the authors' experience in patients who underwent hepatectomy for small HCC and the factors that influence or improve long term survival. METHODS: The study included 1000 patients who underwent hepatectomy for small HCC (< or = 5 cm) and compared them with 1366 patients who underwent hepatectomy for large HCC (> 5 cm) during the same period. A Cox proportional-hazards model was used for multivariate analysis of prognostic factors. RESULTS: Comparison between patients with small HCC (n = 1000 patients) and patients with large HCC (n = 1366 patients) revealed that those with small HCC had a higher resection rate (93.6% [1000 of 1068 patients] vs. 55.7% [1366 of 2451 patients]; P < 0.01), a higher curative resection rate (80.5% [805 of 1000 patients] vs. 60.7% [829 of 1366 patients]; P < 0.01), a lower operative mortality rate (1.5% [15 of 1000 patients] vs. 3.7% [50 of 1366 patients]; P < 0.01), better differentiation of tumor cells (Edmondson Grade 3-4; 14.9% vs. 20.1%; P < 0.01), a higher incidence of single nodule tumors (82.6% vs. 64.4%; P < 0.01), a higher proportion of well encapsulated tumors (73.3% vs. 46.3%; P < 0.01), a lower incidence of tumor emboli in the portal vein (4.9% vs. 20.8%; P < 0.01), and higher survival rates after undergoing resection (5 years: 62.7% vs. 37.1%; P < 0.01; 10 years: 46.3% vs. 29.2%; P < 0.01). No significant difference was found between survival after undergoing minor resection (n = 949 patients) or lobectomy (n = 51 patients) in patients with small HCC (P > 0.05). Reresection for subclinical recurrence or solitary pulmonary metastasis after small HCC resection was undertaken in 84 patients. CONCLUSIONS: Resection is still the modality of first choice for the treatment of patients with small HCC. Minor resection instead of lobectomy was the key to increasing resectability and decreasing operative mortality, and reresection for subclinical recurrence or solitary pulmonary metastasis was important approach to prolonging survival further.

[An immunohistochemical study of retinoblastoma].

Various immunohistochemical marders were detected in 27 specimens of human retinoblastoma by the avidin-biotin-peroxidase complex technique, using mono- and polyclonal antibodies. The glial markers, glial fibrillary acidic protein and Leu-7 were detected in the retinal tissue component and reactive perivascular glial cells in the tumor mass. In only 4 of the 27 specimens, Leu-7 was positive in the glial cells randomly interspersed among the tumor cells and not associated with blood vessels. The neuronal marker, neuron-specific enolase, stained strongly positive in undifferentiated tumor cells in most (21/27) of the specimens. Rhodopsin, the photoreceptor marker which exists only in the outer segments of photoreceptor cells, was detected in the fleurettes of 1 tumor and in the rosettes of 6 tumors, these results support the view that retinoblastoma is chiefly neuronal in nature with tendency to differentiate into photoreceptor cells and rarely into glial cells.

Orbital rhabdomyosarcoma. Immunohistochemical studies of seven cases.

An immunohistochemical analysis using a series of mono- and polyclonal antibodies against myoglobin, desmin, vimentin, actin, NSE, S-100 protein and keratin was done on alveolar rhabdomyosarcoma (3 cases), embryonal (3) and pleomorphic rhabdomyosarcoma of the orbit (1). All tumors were stained by monoclonal antibodies to desmin and vimentin, whereas 6 of the 7 cases were stained by myoglobin. The results indicate that desmin and vimentin are highly sensitive immunohistochemical markers for the diagnosis of rhabdomyosarcoma, especially in poorly differentiated ones.