Mechanistic studies on carboxypeptidase a from goat pancreas — part II: Evidence for carboxyl group

Studies with substrate analogues and the pH optimum indicated the involvement of carboxyl group in the active site of goat carboxypeptidase A. Chemical modification of the enzyme with 1-cyclohexyl-3-(2-morpholinoethyl) carbodiimide methoI -p-toluene sulphonate, a carboxyl specific reagent, led to loss of both esterase and peptidase activities. Protection studies showed that this carboxyl group was in the active site and was protected by Βp-phenylpropionic acid and glycyl-L-tyrosine. Kinetic studies also confirmed the involvement of carboxylic group because the enzyme modification with water soluble carbodiimide was a two step reaction which excluded the possibility of tyrosine or lysine which are known to give a one step reaction with this reagent     

Pulmonary neuroendocrine cells sense succinate to stimulate myoepithelial cell contraction

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Mechanical forces: The missing link between idiopathic pulmonary fibrosis and lung cancer

Patients with idiopathic pulmonary fibrosis (IPF) have a high risk of developing lung cancer compared with the general population. The morbidity of lung cancer in IPF patient ranges from 3% to 22%, and in some cases exceeds 50%, and these patients have a reduced survival time. However, the mechanisms through which IPF increases the morbidity and mortality in lung cancer remain unclear.By carefully analyzing the pathological features of these two diseases, we uncovered that, first, similar to IPF, lung carcinomas are more frequently found in the peripheral area of the lungs and, second, lung cancers tend to develop from the honeycomb areas in IPF. In accordance with the above pathological features, due to the spatial location, the peripheral areas of the lung experience a high stretch force because the average distance between adjacent alveolar cells in this area tends to be larger than that at the central lung when inflated; furthermore, the honeycomb areas, comprised of condensed fibrous tissue, are characterized by increased stiffness. Both of these pathological features of lung cancer and IPF are coincidentally related to abnormal mechanical forces (stretch and tissue stiffness). Therefore, we believe that the aberrant mechanical forces that are generated in the lung with IPF may contribute to the onset and progression of lung cancer.In this review, we discuss the possible effects of mechanical forces that are generated in IPF on the initiation and progression of lung cancer from the perspective of the hallmarks of cancer, including proliferation, metastasis, angiogenesis, cancer stem cells, immunology, epigenetics, and metabolism, so as to advance our understanding of the pathogenesis of IPF-related lung cancer and to harness these concepts for lung cancer mechanotherapies.     

The protective effects of MSC‐EXO against pulmonary hypertension through regulating Wnt5a/BMP signalling pathway

The aim of the study was to explore the mechanism of mesenchymal stem cell‐derived exosomes (MSC‐EXO) to protect against experimentally induced pulmonary hypertension (PH). Monocrotaline (MCT)‐induced rat model of PH was successfully established by a single intraperitoneal injection of 50 mg/kg MCT, 3 weeks later the animals were treated with MSC‐EXO via tail vein injection. Post‐operation, our results showed that MSC‐EXO could significantly reduce right ventricular systolic pressure (RVSP) and the right ventricular hypertrophy index, attenuate pulmonary vascular remodelling and lung fibrosis in vivo. In vitro experiment, the hypoxia models of pulmonary artery endothelial cell (PAEC) and pulmonary vascular smooth muscle cell (PASMC) were used. We found that the expression levels of Wnt5a, Wnt11, BMPR2, BMP4 and BMP9 were increased, but β‐catenin, cyclin D1 and TGF‐β1 were decreased in MSC‐EXO group as compared with MCT or hypoxia group in vivo or vitro. However, these increased could be blocked when cells were transfected with Wnt5a siRNA in vitro. Taken together, these results suggested that the mechanism of MSC‐EXO to prevent PH vascular remodelling may be via regulation of Wnt5a/BMP signalling pathway.     

PET-CT在非完全实性肺结节中的应用价值

肺癌在中国恶性肿瘤的发病率位居第一,随着低剂量薄层CT在肺癌筛查中的广泛应用,临床发现更多表现为非完全实性结节的肺腺癌,目前众多研究使CT影像学特征和肺腺癌病理的关系得到更进一步的认知,虽然CT能对部分非完全实性结节做出定性和定位诊断,但仍有部分非完全实性结节诊断困难,PET-CT结合了病灶的代谢信息和精确的定位信息,从而提高对肺部结节诊断的敏感性、特异性、准确性,综合多个文献PET-CT在非完全实性结节中的诊断分期价值较CT无明显提升,却在评估预后和制定合适手术方案上可以起到一定的作用,本文就PET-CT在SSN中的应用价值进行阐述。     

Bronchoalveolar lavage in an immunosuppressed rabbit model of invasive pulmonary aspergillosis

A rabbit model of invasive aspergillosis has been used to investigate the pathogenesis of Aspergillus infection in the immunosuppressed host. The animals received hydrocortisone daily and a single dose of cyclophosphamide 2 days prior to intratracheal instillation of conidia from Aspergillus fumigatus. Bronchoalveolar lavage (BAL) was performed in 3 infected and 2 control saline treated animals sacrificed on days 1, 2, 4, 7 and 10 following inoculation. Infective load within the lung was quantified using an assay for chitin which is an important component of fungal cell walls (in particular the hyphal cell wall) and is not present in vertebrate tissue. The total BAL white cell count did not discriminate between infected and saline treated animals and Aspergillus was cultured from one lavage specimen only. Infected animals developed a marked neutrophil alveolitis by day 2 in contrast to a near total absence of neutrophils in the lavages of the control animals. Phagocytosis of conidia by alveolar macrophages was prominent but did not prevent progressive infection as confirmed by measurement of lung chitin. This pattern of cellular response within the alveolar airspace reflects the complex nature of the response to Aspergillus infection in the immunosuppressed host.     

Nucleotide sequence of Suncus murinus immunoglobulin mu gene and comparison with mouse and human mu genes

RNA polymerase from the archaebacterium Sulfolobus acidocaldarius was chemically modified with AMP o-formylphenyl ester followed by reduction with borohydride. The modified protein catalyzes the labeling of its own largest subunit when incubated with [-³³P]UTP in the presence of poly[d(A-T)]. On cleaving of the labeled protein using cyanogen bromide, hydroxylamine or amino acid-specific endoproteinases for a very brief period, the pattern and size of the radioactive fragments formed are best explained by attachment of the label between Gly⁸⁴³ and Met⁸⁹⁵ of the largest subunit. In this region there exists a highly conserved sequence which is also found in other archaebacterial, eukaryotic and prokaryotic RNA polymerases. This suggests that the binding site for the initiating substrate of RNA polymerases has been conserved during evolution.     

Experimental pulmonary candidiasis

The initial interaction of Candida albicans with pulmonary tissue of B6D2/F₁ mice was investigated. The LD₅₀ for mice challenged intravenously (IV) was approximately 3 × 10⁵ yeasts, whereas the LD₅₀ by the intratracheal (IT) route was in excess of 10⁸ yeasts. Mice challenged IV died of progressive yeast growth in the kidneys. In contrast, mice challenged IT rapidly eliminated the entire inoculum by the first day after challenge. Resident pulmonary alveolar macrophages (PAM) killed upwards of 70% of C. albicans in an in vitro killing assay. At effector: target ratios favoring the effector cell population resident PAM were able to restrict the formation of yeast germ tubes to only 30% of the yeasts, whereas at equivalent ratios virtually all of the intracellular yeasts produced germ tubes. Evaluation of the ability of PAM, harvested from genetically different strains of inbred mice, to kill C. albicans in vitro showed that killing ability was a property of resident PAM from mice with the black 6 background. It was discovered that during the initial stages of infection in vivo, the expression of the F4/80 surface molecule was down regulated, and the expression of the Mac 1 surface molecule upregulated. There were no quantitative changes in expression of either Mac 2, Mac 3, Ly 5 or the 5C6 surface epitopes. Taken together, the data show that pulmonary tissue is quantitatively very resistant to C. albicans infection, because of the ability of resident PAM to rapidly phagocytize and kill yeasts. Killing of C. albicans by resident PAM may be a property of a subset of this mononuclear phagocyte population and was accompanied by alterations in the expression of surface molecules.Presented as part of the Everett S. Beneke Symposium in Mycology, May 27, 1988.     

Cobalt-substituted derivatives ofCarcinus hemocyanin

Summary Four derivatives ofCarcinus maenas hemocyanin containing Co(II) in the active site have been prepared under different experimental conditions. Two of them contain one Co(II) ion/active site and most probably represent isomeric forms containing Co(II) either in the fast-reacting or in the slow-reacting position within the active site. A third derivative contains two Co(II) ions active site, which reproduces the metal/protein stoichiometry of native hemocyanin. The fourth derivative is a metal hybrid form containing one Cu(I) ion and one Co(II) ion/active site. The derivatives have been characterized by absorption, circular dichroic and fluorescence spectroscopies. The results indicate that in all derivatives the metal is bound with a low coordination number, in agreement with the presence of three histidine residues/copper ion in the native protein. The two alternative metal-binding positions have different structures as shown by the different spectroscopic properties of the bound Co(II) ions. A marked hyperchromic effect on the optical absorption of Co(II) is observed as a result of the presence of a metal ion in the neighbouring metal-binding position in the active site.     

Lung burden of green nickel oxide aerosol and histopathological findings in rats after continuous inhalation

There are few inhalation studies of nickel carcinogenesis. In this study, Wistar male rats were exposed to green nickel oxide (NiO(G)) aerosols (mass median aerodynamic diameter, 0.6 μm) for 7 h/d, 5 d/wk for up to 12 mo. The average exposure concentration was controlled at 0.3 and 1.2 mg/m³ during the exposure. For histopathological examination and measurement of the nickel concentration in rat organs, the rats were sacrificed at 3, 6, and 12 mo of exposure and 8 mo clearance period following 12 mo of exposure. The nickel content in rat lungs that was observed up to 2.6 mg after 12 mo exposure, was proportional to the exposure concentration during the exposure. The clearance of the nickel from the lungs was very slow and the biological half time was determined 7.7 mo. Although the rats were exposed continuously to NiO(G), for 12 mo and kept for 8 mo clearance period, there were no malignant tumors in any of the exposed animals.