Studies on atrophic change of soleus muscle and its countermeasures in suspended rat

In the environment of microgravity, the disused atrophy of skeletal muscle, especially leg's muscle, would occur. The three purposes of this study were: 1. To observe the dynamic changes of disused atrophy of skeletal muscle under simulated weightlessness; 2. To approach the mechanism of disused atrophy of muscle; 3. To approach the countermeasures for reducing the degree of atrophy of muscle.     

Successful predation of filamentous bacteria by a nanoflagellate challenges current models of flagellate bacterivory

Current models suggest that (i) filamentous bacteria are protected against predation by nanoflagellates, (ii) prey size is positively correlated with prey-predator contact probability, and (iii) contact probability is mainly responsible for size-selective predation by interception-feeding flagellates. We used five strains of filamentous bacteria and one bacterivorous nanoflagellate, Ochromonas sp. strain DS, to test these assumptions. The five strains, including one spirochete and four Betaproteobacteria strains, were isolated by the filtration-acclimatization method. All five strains possess flexible cells, but they differ in average cell length, which ranged from 4.5 to 13.7 micro m. High-resolution video microscopy was used to measure contact, capture, and ingestion rates, as well as selectivity of the flagellate feeding. Growth and feeding experiments with satiating and nonsatiating food conditions, as well as experiments including alternative well-edible prey, were performed. In contrast to predictions by current models, the flagellate successfully consumed all the tested filamentous strains. The ingestion rate was negatively correlated with bacterial length. On the other hand, the lengths of the filamentous bacteria were not positively correlated to the contact rate and capture rate but were negatively correlated to ingestion efficiency. In experiments including alternative nonfilamentous prey, the flagellates showed negative selection for filamentous bacteria, which was independent of food concentration and is interpreted as a passive selection. Our observations indicate that (i) size alone is not sufficient to define a refuge for filamentous bacteria from nanoflagellate predation and (ii) for the investigated filamentous bacteria, prey-predator contact probability could be more influenced by factors other than the prey size.     

Millimeter wave exposure reverses TPA suppression of gap junction intercellular communication in HaCaT human keratinocytes

The effect of 30.16 GHz millimeter wave (MMW) exposure at 1.0 and 3.5 mW/cm2 on gap junction intercellular communication (GJIC) was studied in cultured HaCaT keratinocytes, using the fluorescence recovery after photobleaching (FRAP) technique and laser confocal scanning microscopy to follow the intracellular movement of 5,6-carboxyfluorescein diacetate dye. While MMW exposure alone for 1 h at either 1.0 or 3.5 mW/cm2 did not affect GJIC, MMW exposure in combination with 5 ng/ml TPA treatment reversed TPA induced suppression of GJIC. Exposure at 1.0 mW/cm2 resulted in a partial reversal, and exposure at 3.5 mW/cm2 resulted in essentially full reversal of the TPA suppression.     

Cloning and expression of a putative transferrin cDNA of the spruce budworm, Choristoneura fumiferana

A spruce budworm (Choristoneura fumiferana) transferrin cDNA (CfTf) was isolated and cloned from a cDNA library that was constructed using mRNA from fifth to sixth instar larvae. CfTf cDNA encoded a predicted protein of 681 amino acids with a molecular mass of approximately 76 kDa. CfTf shared 72% and 74% identities at the amino acid level with transferrins of Manduca sexta and Bombyx mori, respectively. Like other transferrins, CfTf retains most of the N-terminal, iron-binding amino acid residues. Northern blot analyses indicated that CfTf mRNA was present at high levels after ecdysis, but that the expression level was low prior to ecdysis at the fourth-sixth instar stages. The highest level of CfTf expression was detected in the fat body. Relatively low levels of expression were detected in the epidermis and no expression was found in the midgut. Expression of CfTf mRNA could be induced by bacteria but not fungi. Expression of CfTf mRNA was suppressed by iron load.     

Novel peptide inhibitors of angiotensin-converting enzyme 2

Angiotensin-converting enzyme 2 (ACE2), a recently identified human homolog of ACE, is a novel metallocarboxypeptidase with specificity, tissue distribution, and function distinct from those of ACE. ACE2 may play a unique role in the renin-angiotensin system and mediate cardiovascular and renal function. Here we report the discovery of ACE2 peptide inhibitors through selection of constrained peptide libraries displayed on phage. Six constrained peptide libraries were constructed and selected against FLAG-tagged ACE2 target. ACE2 peptide binders were identified and classified into five groups, based on their effects on ACE2 activity. Peptides from the first three classes exhibited none, weak, or moderate inhibition on ACE2. Peptides from the fourth class exhibited strong inhibition, with equilibrium inhibition constants (K(i) values) from 0.38 to 1.7 microm. Peptides from the fifth class exhibited very strong inhibition, with K(i) values < 0.14 microm. The most potent inhibitor, DX600, had a K(i) of 2.8 nm. Steady-state enzyme kinetic analysis showed that these potent ACE2 inhibitors exhibited a mixed competitive and non-competitive type of inhibition. They were not hydrolyzed by ACE2. Furthermore, they did not inhibit ACE activity, and thus were specific to ACE2. Finally, they also inhibited ACE2 activity toward its natural substrate angiotensin I, suggesting that they would be functional in vivo. As novel ACE2-specific peptide inhibitors, they should be useful in elucidation of ACE2 in vivo function, thus contributing to our better understanding of the biology of cardiovascular regulation. Our results also demonstrate that library selection by phage display technology can be a rapid and efficient way to discover potent and specific protease inhibitors.     

血管紧张素Ⅱ对模拟缺血心室肌细胞L-型钙通道的影响

实验研究了血管紧张素II（AngⅡ)对模拟缺血心室肌细胞L－型钙离子通道的作用,用胶原酶酶解法急性分离豚鼠心室肌细胞,以全细胞膜片钳方法记录心室肌细胞的L－型钙电流（ICa L.)。采用低氧,无糖,高乳酸和酸中毒综合方式模拟缺血液灌流,造成心室肌细胞的模拟缺血,并在缺血的基础上继续用含100mmol/A AngⅡ灌流细胞,观察AngⅡ对模拟缺血心室肌细胞钙离子通道的影响,实验结果显示,模拟缺血时ICa.L峰值电流明显减小,最大激活电压为0mV,AngⅡ能抵抗模拟缺血对ICa,L的抑制效应,使ICa,L峰值电流增大,并使最大激活电压左移至－10mV。     

ILPIP,a novel anti-apoptotic protein that enhances XIAP-mediated activation of JNK1 and protection against apoptosis

We have previously described a new aspect of the Inhibitor of Apoptosis (IAP) family of proteins anti-apoptotic activity that involves the TAK1/JNK1 signal transduction pathway (1,2). Our findings suggest the existence of a novel mechanism that regulates the anti-apoptotic activity of IAPs that is separate from caspase inhibition but instead involves TAK1-mediated activation of JNK1. In a search for proteins involved in the XIAP/TAK1/JNK1 signaling pathway we isolated by yeast two-hybrid screening a novel X chromosome-linked IAP (XIAP)-interacting protein that we called ILPIP (hILP-Interacting Protein). Whereas ILPIP moderately activates JNK family members when expressed alone, it strongly enhances XIAP-mediated activation of JNK1, JNK2, and JNK3. The expression of a catalytically inactive mutant of TAK1 blocked XIAP/ILPIP synergistic activation of JNK1 thereby implicating TAK1 in this signaling pathway. ILPIP moderately protects against interleukin-1beta converting enzyme- or Fas-induced apoptosis and significantly potentiates the anti-apoptotic activity of XIAP. In vivo co-precipitation experiments show that both ILPIP and XIAP interact with TAK1 and tumor necrosis factor receptor-associated factor 6. Finally, expression of ILPIP did not affect the ability of XIAP to inhibit caspase activation, further supporting the idea that XIAP protection against apoptosis is achieved by two separate mechanisms: one requiring JNK1 activation and a second involving caspase inhibition.     

Causal relationship between the loss of RUNX3 expression and gastric cancer

Runx3/Pebp2alphaC null mouse gastric mucosa exhibits hyperplasias due to stimulated proliferation and suppressed apoptosis in epithelial cells, and the cells are resistant to growth-inhibitory and apoptosis-inducing action of TGF-beta, indicating that Runx3 is a major growth regulator of gastric epithelial cells. Between 45% and 60% of human gastric cancer cells do not significantly express RUNX3 due to hemizygous deletion and hypermethylation of the RUNX3 promoter region. Tumorigenicity of human gastric cancer cell lines in nude mice was inversely related to their level of RUNX3 expression, and a mutation (R122C) occurring within the conserved Runt domain abolished the tumor-suppressive effect of RUNX3, suggesting that a lack of RUNX3 function is causally related to the genesis and progression of human gastric cancer.