[Temporal and spatial variations and driving factors of phytoplankton in Yongjiang River estuary]. / ç”¬æ±Ÿå£æµ®æ¸¸æ¤ç‰©æ—¶ç©ºåˆ†å¸ƒç‰¹å¾åŠé©±åŠ¨å› å­.

To explore the temporal and spatial variations in phytoplankton community in small estuaries, we collected surface water samples from Yongjiang River estuary during wet, normal, and dry seasons and determined the main driving factors of phytoplankton community. A total of 358 species belonging to nine phyla and 123 genera were identified in all seasons. During wet, normal, and dry seasons, species number was 276, 154 and 151, and the abundance was (170.45±225.43)×103, (51.92±30.28)×103 and (31.65±12.79)×103 cells·L-1, respectively. Diatoms dominated the phytoplankton community, and the main dominant species were Cyclotella meneghiniana, Skeletonema costatum, and Paralia sulcata. Shannon diversity and Pielou evenness indices decreased from inside mouth to outside mouth in wet season, but there was no obvious spatial difference in normal season or dry season. Results of non-metric multidimensional scaling analysis and analysis of similarities showed that phytoplankton community composition differed significantly among different regions (inside, at and outside mouth) and different seasons. In wet season, phytoplankton abundance was significantly positively correlated with temperature, dissolved inorganic nitrogen, and dissolved reactive phosphorus, but significantly negatively correlated with salinity. In normal season, phytoplankton abundance was significantly negatively correlated with temperature. In dry season, it was not significantly correlated with environmental factors. Results of redundancy analysis showed that temperature, salinity, ammonium and dissolved reactive phosphorus explained the variations in phytoplankton community by 19.5%, 11.9%, 9.4% and 8.2%, respectively. These results revealed high dominance of diatoms and the main driving factors (temperature, salinity and nutrients) of phytoplankton community in Yongjiang River estuary.

Protective effect of microinjection of glutamate into hypothalamus paraventricular nucleus on chronic visceral hypersensitivity in rats.

Chronic visceral hypersensitivity (CVH) is a major pathophysiological feature of patients experiencing in irritable bowel syndrome (IBS) and other disorders with visceral pain. However, little is known about its regulation of the central nucleus. In this research, we investigated the protective effect of microinjection of glutamate into hypothalamus paraventricular nucleus (PVN) on CVH and its possible regulatory mechanism in rats. Visceral sensitivity was assessed by pain threshold, abdominal withdrawal reflex (AWR) score, and the abdominal external oblique muscle electromyography (EMG) amplitude. Pathological changes in colorectal mucosa were assessed using immunohistochemical, biochemical analysis and Western blot. Results showed that microinjection of different doses of glutamate into PVN reduced the visceral sensitivity in a dose-dependent manner. This effect can be reversed after chemical ablation of PVN or nucleus tractus solitarius (NTS) or pretreatment with the arginine vasopressin (AVP)-V1 receptor antagonist ([Deamino-pen1,val4,D-Arg8]-vasopressin) DPVDAV into NTS. The vagus discharge frequency was significantly reduced after the glutamate microinjection into PVN. Additionally, oxidation, proliferation and apoptosis in colorectal mucosa were related to the CVH regulations. These findings suggested that PVN and NTS are involved in the regulatory process of CVH and exert the protective effect on CVH, providing new ideas and therapeutic targets for CVH research.

Protective effect and mechanism of injection of glutamate into cerebellum fastigial nucleus on chronic visceral hypersensitivity in rats.

AIMS: We investigated the effects of chemical stimulation of cerebellum fastigial nucleus (FN) on the chronic visceral hypersensitivity (CVH) and its possible mechanism in rats. MAIN METHODS: We stimulated the FN by microinjecting glutamate into the FN, in order to explore whether the cerebellum fastigial nucleus played a role on CVH in rat. The model of CVH was established by colorectal distension (CRD) in neonatal rats. Abdominal withdrawal reflex (AWR) scores, pain threshold, and amplitude of electromyography (EMG) were used to assess the hyperalgesia. KEY FINDINGS: We showed that microinjection of l-glutamate (Glu) into the FN markedly attenuated hyperalgesia. The protective effect of FN was prevented by pretreatment with the glutamate decarboxylase inhibitor, 3-mercaptopropionic acid (3-MPA) into the FN or GABAA receptor antagonist, bicuculline (Bic) into the LHA (lateral hypothalamic area). The expressions of protein Bax, caspase-3 were decreased, but the expression of protein Bcl-2 was increased after chemical stimulation of FN. These results indicated that the FN participated in regulation of CVH, and was a specific area in the CNS for exerting protective effects on the CVH. In addition, LHA and GABA receptor may be involved in this process. SIGNIFICANCE: Our findings might provide a new and improved understanding of the FN function, and might show an effective treatment strategy for the chronic visceral hypersensitivity.