宽体金线蛭消化道的组织学观察

运用解剖学和组织学方法对宽体金线蛭消化道的结构进行了组织学研究。结果表明,宽体金线蛭的嗉囊向两侧伸出11对侧盲囊,第6对侧盲囊狭长并延伸到直肠两侧;咽主要由黏膜层、肌层和外膜构成,外膜几乎不可见;食道、嗉囊、肠和直肠管壁由黏膜层、黏膜下层、肌层和浆膜构成;咽和直肠的上皮具纹状缘。除肠外,其他消化道的上皮细胞均无发达的纤毛,且黏膜上皮皆为单层柱状上皮;除肠和直肠外,腺体及导管较少;直肠的黏膜肌层为内环外纵两层,其他各部均为纵行肌一层;消化道各部黏膜下层较发达;外膜为浆膜,与黏膜下层分界不明显。     

宽体金线蛭嗜水气单胞菌感染的病原检验

对河北某宽体金线蛭（Whitmania pigra Whitman）养殖场所养殖的宽体会线蛭发生的病害,进行了发病情况、临床表现、病理变化等方面的枪验。同时,择代表菌株进行了16S rRNA基因的分子鉴定,测定了16S rRNA基因序列、分析了相关细菌相应序列的同源性、构建了系统发生树。结果表明所检病例为由嗜水气单胞菌（Aeronmnas hydrophila）所引起的感染。分离后做纯培养的10株嗜水气申胞菌均为同种血清型菌株;代表菌株对健康宽体金线蛭的人工感染试验表明了相应的原发病原学意义;药敏试验结果显示,对供试37种抗菌药物中的头孢噻肟等高度敏感、对链霉素等敏感、对苯唑青霉素等耐药。     

肠道菌群失衡与乳糜泻:重要性及可能机制

乳糜泻(Celiac disease,CeD)是基因易感人群摄入麸质后所发生的一种自身免疫性肠道疾病.越来越多证据表明,"第二人类基因组"——肠道菌群参与了CeD的发生与发展.相对于健康人群,CeD患者的肠道菌群多样性虽然增高,但有益菌减少,促炎细菌增多,并伴随菌群功能及代谢状态的改变.然而,这种菌群失衡是如何发生的,...     

Isolation and characterization of microsatellite loci for the analysis of genetic diversity in Whitmania pigra

The objective of this study was to isolate microsatellite loci to analyze the genetic diversity of Whitmania pigra. Four new microsatellite markers of W. pigra were developed from an enriched library and ten from a modified SAMPL assay. A total of 127 alleles were detected, with an average of 9.1 alleles per locus. The expected heterozygosity (He) of each microsatellite locus varied from 0.451 to 0.857, with an average of 0.688. The polymorphism information content (PIC) of each microsatellite locus ranged from 0.361 to 0.838, with an average of 0.640. Analysis of molecular variance showed that the main variation component existed within the populations (81.64%) rather than among the populations (18.36%). Phylogenetic tree for 15 populations of Hirudo using the NJ method by MEGA 5.1 software were divided into two major clusters. These microsatellite markers will contribute to research on the individual identification, genetic diversity, population structure, genome mapping and conservation biology of Hirudo.     

Multiple cellular responses to serotonin contribute to epithelial homeostasis

Epithelial homeostasis incorporates the paradoxical concept of internal change (epithelial turnover) enabling the maintenance of anatomical status quo. Epithelial cell differentiation and cell loss (cell shedding and apoptosis) form important components of epithelial turnover. Although the mechanisms of cell loss are being uncovered the crucial triggers that modulate epithelial turnover through regulation of cell loss remain undetermined. Serotonin is emerging as a common autocrine-paracine regulator in epithelia of multiple organs, including the breast. Here we address whether serotonin affects epithelial turnover. Specifically, serotonin's roles in regulating cell shedding, apoptosis and barrier function of the epithelium. Using in vivo studies in mouse and a robust model of differentiated human mammary duct epithelium (MCF10A), we show that serotonin induces mammary epithelial cell shedding and disrupts tight junctions in a reversible manner. However, upon sustained exposure, serotonin induces apoptosis in the replenishing cell population, causing irreversible changes to the epithelial membrane. The staggered nature of these events induced by serotonin slowly shifts the balance in the epithelium from reversible to irreversible. These finding have very important implications towards our ability to control epithelial regeneration and thus address pathologies of aberrant epithelial turnover, which range from degenerative disorders (e.g.; pancreatitis and thyrioditis) to proliferative disorders (e.g.; mastitis, ductal ectasia, cholangiopathies and epithelial cancers).     

Biological control of the exotic invasive snail Pomacea canaliculata with the indigenous medicinal leech Whitmania pigra

The apple snail Pomacea canaliculata has been an invasive species in China for decades and causes enormous losses to agriculture. The predation capability of the leech Whitmania pigra on P. canaliculata was studied for its economic benefit and potential application. In the present study, the leech W. pigra exhibited a strong predatory capacity in controlling P. canaliculata under both laboratory and field conditions, and it showed no bias towards consuming smaller snails during the experiments. More than 80% of the 80 snails (of which half had reached maturity) were preyed upon by 20 developing leeches (2–7?g) in miniature rice fields over a 15-day period, and the number of rice seedlings damaged by P. canaliculata was decreased in the presence of W. pigra. In a separate experiment, 15 developing snails were exposed to caged leeches and conspecific snails for four weeks. The food intake and growth of P. canaliculata were inhibited under the predation risk imposed by W. pigra, but the feeding rate, food conversion efficiency and survival of P. canaliculata were not conspicuously influenced.     

ClC-2 chloride channels contribute to HTC cell volume homeostasis

Membrane Cl(-) channels play an important role in cell volume homeostasis and regulation of volume-sensitive cell transport and metabolism. Heterologous expression of ClC-2 channel cDNA leads to the appearance of swelling-activated Cl(-) currents, consistent with a role in cell volume regulation. Since channel properties in heterologous models are potentially modified by cellular background, we evaluated whether endogenous ClC-2 proteins are functionally important in cell volume regulation. As shown by whole cell patch clamp techniques in rat HTC hepatoma cells, cell volume increases stimulated inwardly rectifying Cl(-) currents when non-ClC-2 currents were blocked by DIDS (100 microM). A cDNA closely homologous with rat brain ClC-2 was isolated from HTC cells; identical sequence was demonstrated for ClC-2 cDNAs in primary rat hepatocytes and cholangiocytes. ClC-2 mRNA and membrane protein expression was demonstrated by in situ hybridization, immunocytochemistry, and Western blot. Intracellular delivery of antibodies to an essential regulatory domain of ClC-2 decreased ClC-2-dependent currents expressed in HEK-293 cells. In HTC cells, the same antibodies prevented activation of endogenous Cl(-) currents by cell volume increases or exposure to the purinergic receptor agonist ATP and delayed HTC cell volume recovery from swelling. These studies provide further evidence that mammalian ClC-2 channel proteins are functional and suggest that in HTC cells they contribute to physiological changes in membrane Cl(-) permeability and cell volume homeostasis.     

Angiotensin receptors contribute to blood pressure homeostasis in salt-depleted SHR

This study evaluated the contribution of angiotensin peptides acting at various receptor subtypes to the arterial pressure and heart rate of adult 9-wk-old male conscious salt-depleted spontaneously hypertensive rats (SHR). Plasma ANG II and ANG I in salt-depleted SHR were elevated sevenfold compared with peptide levels measured in sodium-replete SHR, whereas plasma ANG-(1-7) was twofold greater in salt-depleted SHR compared with salt-replete SHR. Losartan (32.5 micromol/kg), PD-123319 (0.12 micromol. kg(-1). min(-1)), [d-Ala(7)]ANG-(1-7) (10 and 100 pmol/min), and a polyclonal ANG II antibody (0.08 mg/min) were infused intravenously alone or in combination. Combined blockade of AT(2) and AT((1-7)) receptors significantly increased the blood pressure of losartan-treated SHR (+15 +/- 1 mmHg; P < 0.01); this change did not differ from the blood pressure elevation produced by the sole blockade of AT((1-7)) receptors (15 +/- 4 mmHg). On the other hand, sole blockade of AT(2) receptors in losartan-treated SHR increased mean arterial pressure by 8 +/- 1 mmHg (P < 0.05 vs. 5% dextrose in water as vehicle), and this increase was less than the pressor response produced by blockade of AT((1-7)) receptors alone or combined blockade of AT((1-7)) and AT(2) receptors. The ANG II antibody increased blood pressure to the greatest extent in salt-depleted SHR pretreated with only losartan (+11 +/- 2 mmHg) and to the least extent in salt-depleted SHR previously treated with the combination of losartan, PD-123319, and [d-Ala(7)]ANG-(1-7) (+7 +/- 1 mmHg; P < 0.01). Losartan significantly increased heart rate, whereas other combinations of receptor antagonists or the ANG II antibody did not alter heart rate. Our results demonstrate that ANG II and ANG-(1-7) act through non-AT(1) receptors to oppose the vasoconstrictor actions of ANG II in salt-depleted SHR. Combined blockade of AT(2) and AT((1-7)) receptors and ANG II neutralization by the ANG II antibody reversed as much as 67% of the blood pressure-lowering effect of losartan.     

Enterocyte death and intestinal barrier maintenance in homeostasis and disease

The intestinal epithelium is the largest surface area of the body in contact with the external environment. This specialized single cell layer is constantly renewed and is a physical barrier that separates intestinal microbiota from underlying tissues, preventing bacterial infiltration and subsequent inflammation. Specialized secretory epithelial cell types such as Paneth cells and goblet cells limit bacterial adhesion and infiltration by secreting antibacterial peptides and mucins, respectively. Rapid cell renewal coincides with apical exfoliation of 'old' enterocytes without compromising epithelial barrier integrity. When the intestinal epithelium is inflamed barrier integrity can be compromised, due to uncontrolled death of enterocytes allowing bacterial infiltration. This review discusses the different mechanisms which regulate or affect intestinal barrier integrity under homeostatic and inflammatory conditions.     

Ultrastructure of electrical synapses between nociceptive and anterior pagoda neurons in the CNS of the leech (Whitmania pigra)

We have used electron microscopy to measure quantitatively the morphology of electrical synapses in a circuit that has been proposed to account for the positional discrimination of the leech. Injection of a presynaptic nociceptive sensory neuron and the postsynaptic anterior pagoda neuron with HRP showed gap junctions in the neuropil. After double labeling, La³⁺-treated ganglia revealed labeled gap junctions from 2.0 to 3.5 nm wide. Between the labeled axon terminals, there were innexons with diameters of 8 to 10 nm. The innexon's central pore diameter was 2 nm, and the mean of the center-to-center distance between two innexons was 30 nm. Except for the gap junction areas of nociceptive sensory neuron axon terminals, the other ultrastructural parameters measured by freeze fracture were similar to those of samples labeled with HRP and filled with La³⁺. These data suggested that the gap width, innexon diameter, and its central pore do not on their own account for the mechanism of positional discrimination, which may depend rather on the differences in distribution and number of gap junctions. Electronic Publication     

Innate immune signalling at the intestinal epithelium in homeostasis and disease

The intestinal epithelium-which constitutes the interface between the enteric microbiota and host tissues-actively contributes to the maintenance of mucosal homeostasis and defends against pathogenic microbes. The recognition of conserved microbial products by cytosolic or transmembrane pattern recognition receptors in epithelial cells initiates signal transduction and influences effector cell function. However, the signalling pathways, effector molecules and regulatory mechanisms involved are not yet fully understood, and the functional outcome is poorly defined. This review analyses the complex and dynamic role of intestinal epithelial innate immune recognition and signalling, on the basis of results in intestinal epithelial cell-specific transgene or gene-deficient animals. This approach identifies specific epithelial cell functions within the diverse cellular composition of the mucosal tissue, in the presence of the complex and dynamic gut microbiota. These insights have thus provided a more comprehensive understanding of the role of the intestinal epithelium in innate immunity during homeostasis and disease.     

IGFBP2 expressing midlobular hepatocytes preferentially contribute to liver homeostasis and regeneration

1. Download : Download high-res image (290KB)
2. Download : Download full-size image

     

Both Notch1 and Notch2 contribute to the regulation of melanocyte homeostasis

Notch signaling affects a variety of mammalian stem cells, but there has been limited evidence that a specific Notch molecule regulates adult stem cells. Recently, it was reported that the reduced Notch signaling initiated at the embryonic stage results in a gradual hair graying phenotype after birth. Here we demonstrate that the oral administration of a gamma-secretase inhibitor (GSI) to wild-type adult C57/Bl6 mice led to a gradual increase in gray spots, which remained unchanged for at least 20 weeks after discontinuing the GSI. In GSI-treated mice, there was a severe decrease in unpigmented melanocytes in the bulge/subbulge region where melanocyte stem cells are located. While we confirmed that Notch1+/-Notch2+/- double heterozygous mice with a C57/Bl6 background were born with a normal hair color phenotype and gradually turned gray after the second hair cycle, in the c-kit mutant Wv background, Notch1+/- and Notch2+/- mice had larger white spots on the first appearance of hair than did the Wv/+ mice, which did not change throughout life. Notch1+/-Notch2+/-Wv/+ mice had white hair virtually all over the body at the first appearance of hair and the depigmentation continued to progress thereafter. Using a neural crest organ culture system, GSI blocked the generation of pigmented melanocytes when added to the culture during the period of melanoblast proliferation, but not during the period of differentiation. These observations imply roles of Notch signaling in both development of melanocyte during embryogenesis and maintenance of melanocyte stem cells in adulthood, while the degree of requirement is distinct in these settings: the latter is more sensitive than the former to the reduced Notch signaling. Furthermore, Notch1 and Notch2 cooperates with c-kit signaling during embryogenesis, and they cooperate with each other to regulate melanocyte homeostasis after birth.     

The complete mitochondrial genome sequence of Whitmania pigra (Annelida, Hirudinea): the first representative from the class Hirudinea

The mitochondrial genome is a significant tool for investigating the evolutionary history of metazoan animals. The currently available mitochondrial genome data in GenBank is limited to understand the detail evolutionary relationship among the metazoan animals, especially in the phylum Annelida. Here we present the mitochondrial gene organization, gene order and codon usage of the leech Whitmania pigra (Annelida), which is the first representative from the class Hirudinea. It is a circular molecule of 14,426bp, and encodes 13 protein-coding genes, 2 ribosomal RNA genes, and 22 transfer RNA genes. All 37 genes of W. pigra mitochondrial genome are transcribed from the same strand, which is identical to studied annelids, two echiurans, two sipunculans and many other lophotrochozoans. Five conserved gene clusters can be found in mitochondrial genomes of nine studied annelids, including (1) cox1-N-cox2; (2) cox3-Q-nad6-cob-W-atp6; (3) H-nad5-F-E-P-T-nad4L-nad4; (4) srRNA-V-lrRNA; and (5) nad3-S(1)-nad2. Compared with that of other studied annelids, translocations of transfer RNAs were found in the gene arrangement of W. pigra mitochondrial genome. Phylogenetic analysis strongly support that the species from Hirudinina and Oligochaeta form a monophyletic group Clitellata (BPM=100, BPP=100), which is consistent with previous research based on morphological and other molecular data. Both gene order data and amino acid sequences reveal that echiurans are derived annelids and sipunculans should be clustered with annelids and echiurans.     

Correlation of receptive field position of mechanosensory neurons and the strength of their connections to AP neurons in the CNS of the leech (Whitmania pigra)

An identified neuron of unknown function in the CNS of the leech, the anterior pagoda (AP) cell, receives multiple synaptic inputs from mechanosensory neurons that innervate the skin. Impulses in touch (T), pressure (P) and nociceptive (N) sensory cells on both sides of the ganglion produced electrical coupling potentials on both AP cells. Sensory cells with receptive fields contralateral to the cell body of the AP neuron always gave rise to larger synaptic potentials. In addition sensory cells supplying dorsal skin gave rise to larger synaptic potentials than those with lateral or ventral fields. It is suggested that integration by the AP cell can provide information about the position of mechanical stimuli impinging on the body wall of the animal.     

Hepatic inflammatory mediators contribute to intestinal damage in necrotizing enterocolitis

Necrotizing enterocolitis (NEC) is a common and devastating gastrointestinal disease of premature infants. Along with pathological effects in the ileum, severe NEC is often accompanied by multisystem organ failure, including liver failure. The aim of this study was to determine the changes in hepatic cytokines and inflammatory mediators in experimental NEC. The well-established neonatal rat model of NEC was used in this study, and changes in liver morphology, numbers of Kupffer cells (KC), gene expression, and histological localization of IL-18, TNF-alpha, and inducible nitric oxide synthase were evaluated. Intestinal luminal TNF-alpha levels were also measured. Production of hepatic IL-18 and TNF-alpha and numbers of KC were increased in rats with NEC and correlated with the progression of intestinal damage during NEC development. Furthermore, increased levels of TNF-alpha in the intestinal lumen of rats with NEC was significantly decreased when KC were inhibited with gadolinium chloride. These results suggest an important role of the liver and the gut-liver axis in NEC pathogenesis.     

Site‐specific contribution of Toll‐like receptor 4 to intestinal homeostasis and inflammatory disease

Toll‐like receptor 4 (TLR4) is a highly conserved protein of innate immunity, responsible for the regulation and maintenance of homeostasis, as well as immune recognition of external and internal ligands. TLR4 is expressed on a variety of cell types throughout the gastrointestinal tract, including on epithelial and immune cell populations. In a healthy state, epithelial cell expression of TLR4 greatly assists in homeostasis by shaping the host microbiome, promoting immunoglobulin A production, and regulating follicle‐associated epithelium permeability. In contrast, immune cell expression of TLR4 in healthy states is primarily centred on the maturation of dendritic cells in response to stimuli, as well as adequately priming the adaptive immune system to fight infection and promote immune memory. Hence, in a healthy state, there is a clear distinction in the site‐specific roles of TLR4 expression. Similarly, recent research has indicated the importance of site‐specific TLR4 expression in inflammation and disease, particularly the impact of epithelial‐specific TLR4 on disease progression. However, the majority of evidence still remains ambiguous for cell‐specific observations, with many studies failing to provide the distinction of epithelial versus immune cell expression of TLR4, preventing specific mechanistic insight and greatly impacting the translation of results. The following review provides a critical overview of the current understanding of site‐specific TLR4 activity and its contribution to intestinal/immune homeostasis and inflammatory diseases.