Surface indentation and fluid intake generated by the polymer matrix of Bacillus subtilis biofilms.

Bacterial biofilms are highly structured, surface associated bacteria colonies held together by a cell-generated polymer network known as EPS (extracellular polymeric substance). This polymer network assists in adhesion to surfaces and generates spreading forces as colonies grow over time. In the laboratory and in nature, biofilms often grow at the interface between air and an elastic, semi-permeable nutrient source. As this type of biofilm increases in volume, an accommodating compression of its substrate may arise, potentially driven by the osmotic pressure exerted by the EPS against the substrate surface. Here we study Bacillus subtilis biofilm force generation by measuring the magnitude and rate of deformation imposed by colonies against the agar-nutrient slabs on which they grow. We find that the elastic stress stored in deformed agar is orders of magnitude larger than the drag stress associated with pulling fluid through the agar matrix. The stress exerted by the biofilm is nearly the same as the osmotic pressure generated by the EPS, and mutant colonies incapable of producing EPS exert much lower levels of stress. The fluid flow rate into B. subtilis biofilms suggest that EPS generated pressure provides some metabolic benefit as colonies expand in volume. These results reveal that long-term biofouling and colony expansion may be tied to the hydraulic permeability and elasticity of the surfaces that biofilms colonize.

[Correlation and mechanism between chronic kidney disease and periodontitis based on cross-sectional data].

Objective: To explore the correlation between periodontitis (PD) and chronic kidney disease (CKD) in adults, as well as the potential mechanisms involved. Methods: Data on PD and CKD from the National Health and Nutrition Examination Survey (NHANES) database between 1999 and 2014 were downloaded. Weighted univariate and multivariate logistic regression analyses were conducted to investigate the risk factors associated with PD and CKD, considering demographic and clinical indicators. Using publicly available genome-wide association study (GWAS) summary datasets for CKD and PD as outcome variables, as well as 731 immune cell phenotypes and 91 inflammatory proteins as exposure factors from the OPEN GWAS database, a two-sample Mendelian randomization (TSMR) analysis was performed using the inverse-variance weighted (IVW) method. Results: Seven demographic indicators including gender, age, race, education level, marital status, income, and health are related to the incidence of CKD and PD. Among them, the elderly (≥60 years old), poverty (poverty-income ratio <1.3), divorce or widowhood, and male ratio in the comorbidity group of CKD and PD [67.12% (833/1 241), 36.83% (457/1 241), 34.41% (427/1 241), and 57.78% (717/1 241) respectively] were significantly higher than those in the control group [23.71% (4 179/17 623), 29.17% (5 141/17 623), 18.16% (3 200/17 623), and 48.73% (8 587/17 623) respectively] (all P<0.001). Those with high educational level (university and above) and self-rated excellent health accounted for a relatively small proportion in the comorbidity group [14.10% (175/1 241) and 8.22% (102/1 241) respectively]. The prevalence of PD increased among individuals with abnormal renal function indices, including glomerular filtration rate, urine protein/creatinine ratio, serum creatinine, serum uric acid, and blood urea nitrogen. Univariate logistic regression analysis showed a positive correlation between the incidence of PD and CKD (OR=2.14, 95%CI: 1.90-2.42, P<0.001). Multivariate logistic regression analysis also indicated that PD and CKD were potential risk factors for each other (PD for CKD: OR=1.22, 95%CI: 1.07-1.40, P=0.004; CKD for PD: OR=1.19, 95%CI: 1.04-1.37, P=0.012). Furthermore, after adjusting the model based on demographic indicators, there was still a significant correlation between PD and CKD (P=0.010). Mechanistically, the results of the TSMR analysis support the existence of a common risk factor mediated by immune cells between CKD and PD, namely the expression of CD64 on multiple innate immune cells mediates the occurrence of CKD and PD. The absolute count of CD64+ monocytes is associated with an increased risk for both CKD (HR=1.11) and PD (HR=1.07), while same tendency showed in the absolute count of CD64+ neutrophils for CKD (HR=1.22) and PD (HR=1.23). Conclusions: There is a positive correlation between CKD and PD, particularly moderate to severe PD, and the shared pathogenesis involves CD64+ monocytes in the circulatory system. Targeted interventions focusing on CD64 molecules or monocyte subsets may be beneficial.

Porphyromonas gingivalis Promotes Oral Squamous Cell Carcinoma Progression in an Immune Microenvironment.

Increasing evidence has revealed a significant association between microorganisms and oral squamous cell carcinoma (OSCC). Porphyromonas gingivalis, the keystone pathogen in chronic periodontitis, is considered an important potential etiologic agent of OSCC, but the underlying immune mechanisms through which P. gingivalis mediates tumor progression of the oral cancer remain poorly understood. Our cohort study showed that the localization of P. gingivalis in tumor tissues was related to poor survival of patients with OSCC. Moreover, P. gingivalis infection increased oral lesion multiplicity and size and promoted tumor progression in a 4-nitroquinoline-1 oxide (4NQO)-induced carcinogenesis mouse model by invading the oral lesions. In addition, CD11b+ myeloid cells and myeloid-derived suppressor cells (MDSCs) showed increased infiltration of oral lesions. Furthermore, in vitro observations showed that MDSCs accumulated when human-derived dysplastic oral keratinocytes (DOKs) were exposed to P. gingivalis, and CXCL2, CCL2, interleukin (IL)-6, and IL-8 may be potential candidate genes that facilitate the recruitment of MDSCs. Taken together, our findings suggest that P. gingivalis promotes tumor progression by generating a cancer-promoting microenvironment, indicating a close relationship among P. gingivalis, tumor progression of the oral cancer, and immune responses.

Risk factors of postoperative complications after emergency repair of incarcerated groin hernia for adult patients: a retrospective cohort study.

PURPOSE: This study aimed to explore risk factors of postoperative complications for adult patients with incarcerated groin hernia (IGH). METHODS: From January 2010 to December 2017, consecutive patients undergoing emergency hernia repair for IGH in our center were retrospectively reviewed. Postoperative complications, such as surgical site infection, seroma, hernia recurrence and mortality, were investigated, with risk factors for such complications analyzed using univariate and multivariate regressions. RESULTS: Sixty-four patients were included, with 51 males and 13 females (mean age 65.1, range 25-98 years). Ten patients (15.6%) underwent resection of necrotic bowel and anastomosis. 43 patients (67.2%) received open tension-free herniorrhaphy with polypropylene mesh, whereas the rest (32.8%) received herniorrhaphy without mesh. The overall postoperative complication rate was 40.6% (26/64), with an incisional complication rate of 31.2% (20/64) and an infection rate of 6.2% (4/64). At a median follow-up of 32 months, hernia recurrence and mortality were recorded in five cases each (7.8%). Mesh repair was associated with decreased recurrence rate compared with non-mesh repair (2.3% vs. 19.0%, p = 0.019). Diabetes mellitus (OR 8.611, 95%CI 1.292-57.405; p = 0.026) was an independent risk factor of postoperative complications, together with chronic obstructive pulmonary disease (COPD; OR 14.365, 95%CI 1.652-127.767, p = 0.016), intestinal necrosis (OR 14.260, 95%CI 1.079-188.460, p = 0.044), and general anesthesia (OR 14.543, 95%CI 1.682-125.711, p = 0.015) as risk for incisional complications after surgery. CONCLUSIONS: Diabetes mellitus was an independent risk factor of postoperative complications for IGH, along with COPD, intestinal necrosis and general anesthesia associated with incisional complications. The use of polypropylene mesh did not increase infection or recurrence rate in this cohort.

Cleaved antitrypsin polymers at atomic resolution.

Alpha1-antitrypsin deficiency, which can lead to both emphysema and liver disease, is a result of the accumulation of alpha1-antitrypsin polymers within the hepatocyte. A wealth of biochemical and biophysical data suggests that alpha1-antitrypsin polymers form via insertion of residues from the reactive center loop of one molecule into the beta-sheet of another. However, this long-standing hypothesis has not been confirmed by direct structural evidence. Here, we describe the first crystallographic evidence of a beta-strand linked polymer form of alpha1-antitrypsin: the crystal structure of a cleaved alpha1-antitrypsin polymer.

Gel-impregnated pore membranes with mesh-size asymmetry for biohybrid artificial organs.

Membranes based on mechanically supported poly(vinyl alcohol) (PVA) hydrogels with mesh-size asymmetry were developed for potential application in biohybrid artificial organs. The pores of cellulose ester microfiltration membranes were impregnated with a PVA solution, which was lightly crosslinked with glutaraldehyde and then modified under a glutaraldehyde gradient to produce mesh-size asymmetry. Permeation experiments were performed with the resulting homogeneous and asymmetric gel-impregnated pore membranes (GIPMs). Creatinine (MW: 113), goat Fab (MW: 50 kD) and human IgG (MW: 150 kD) were used to simulate the molecular size of nutrients, therapeutic proteins, and immunological molecules, respectively. The transport properties of the GIPMs were compared to those of conventional ultrafiltration (UF) and dialysis membranes. Experimental results indicate that GIPMs with mesh-size asymmetry have thickness-normalized creatinine permeabilities that are slightly higher than those in cellulosic UF membranes but as much as 100% greater than those in polysulfone UF or cellulosic dialysis membranes. IgG permeabilities in the GIPMs are from 5 to 50 times lower than those in the UF membranes. Fab permeabilities are 6 to 40 times higher in the UF membranes than those in the GIPMs, but the required permeability for a therapeutic protein is application specific. GIPMs may also be suitable as an alternative for hemodialysis.

Synergism of cimetidine with anti-malarial agents.

The histamine type-2 receptor antagonist and cytochrome P450 inhibitor cimetidine was examined for its antimalarial properties in the presence or absence of chloroquine or pyrimethamine. When used alone, cimetidine displayed little activity against a number of Plasmodium falciparum clones in vitro, with an IC50 of 300-700 microM. The compound was found to be highly synergistic in combination with chloroquine and also displayed a degree of synergism when used in combination with pyrimethamine. These synergistic effects were independent of the chloroquine- or pyrimethamine-resistance status of the clones. The cytochrome P450 inhibitor proadifen displayed weak synergism or antagonism with chloroquine, depending on the clone tested, and clear antagonism with pyrimethamine. The results with proadifen indicate that cimetidine was exerting its synergistic activity via a mechanism distinct from inhibition of cytochrome P450. Additional experiments have demonstrated that cimetidine interferes with neither plasmodial sterol metabolism nor heme polymerization.

Experimental study of growth of trabecular cells on the filters and hydraulic conductivity.

OBJECTIVES: To search the method of culturing human trabecular cells (HTC) on a filter support so as to provide a model to study the hydraulic conductivity of HTC in vivo. METHODS: The third passage of HTC was cultured on a nylon filter; after that we measured the rate of different irrigations through the filter with HTC [Lp, microliter/(min.mm Hg.cm2)]. RESULTS: HTC could continuously grow on the filters. The normal Lp was 10.45 microliters/(min.mm Hg.cm2). Irrigated by the solution of epinephrine (EPI) or dexamethasone (DEX), Lp of HTC were higher than that in controls of the same cultural time, while after being exposed to DEX for a few days, Lp was significantly decreased. CONCLUSIONS: (1) More information of hydraulic conductivity and effects of pharmacologic agents on HTC could be got from the dynamic filtery model; (2) EPI could improve the conductivity of HTC while DEX could have the same effect in early period.

A new antigen retrieval method using citraconic anhydride for immunoelectron microscopy: localization of surfactant pro-protein C (proSP-C) in the type II alveolar epithelial cells.

In the attempt to develop a pre-embedding immunoelectron microscopic method with improved ultrastructral morphology, we examined an antigen retrieval (AR) method using citraconic anhydride, and compared the effects of glutaraldehyde fixation with routine paraformaldehyde fixation in the pre-embedding immunoelectron microscopic method with reference to the localization of surfactant-associated pro-protein C (proSP-C) in the lung. The glutaraldehyde-fixed tissues were immunostained after AR in 0.05% citraconic anhydride solution, pH 7.4, at 98 degrees C for 60 min. In routine pre-embedding immunoelectron microscopic method using paraformaldehyde fixation, proSP-C positive products were distributed sporadically in the type II alveolar epithelial cells. In glutaraldehyde-fixed tissues without the AR method, proSP-C products were not detected, however after AR in citraconic anhydride proSP-C positive products were distributed specifically, in rough endoplasmic reticulum membranes, Golgi complex membranes, multivesicular bodies and osmiophilic lamellar bodies. The positive proSP-C products also showed lattice-like structures in the alveoli. Thus, the present AR method provides successful pre-embedding immunoelectron microscopy of glutaraldehyde-fixed tissues.

Cell-binding peptides conjugated to poly(ethylene glycol) promote neural cell aggregation.

We have developed a method for promoting cell aggregation with bifunctional macromolecules synthesized by coupling cell-binding peptides to an inert, water-soluble polymer. The peptides Arg-Gly-Asp (RGD) and Tyr-Ile-Gly-Ser-Arg (YIGSR) were conjugated through their amino termini to both ends of linear poly(ethylene glycol) (PEG), producing bifunctional hybrid polymers: RGD-PEG-RGD and YIGSR-PEG-YIGSR. RGD-PEG-RGD promoted aggregation of mechanically-dissociated fetal brain cells, pheochromocytoma cells (PC12), and neuroblastoma cells maintained in rotation culture at 37 degrees C. Enhanced aggregation was noticeable within 10 minutes and became more pronounced over the next several hours: after 7-9 hours, the mean aggregate volume was up to 10 times larger than the mean volume produced in suspensions containing unmodified PEG. Similar results were obtained with YIGSR-PEG-YIGSR and PC12 cells. Enhancement in aggregation correlated with the ability of soluble RGD or YIGSR to inhibit cell adhesion to surfaces coated with laminin or fibronectin. This method for promoting aggregation may be useful for large scale culture of anchorage dependent cells, eliminating the need for microcarriers. In addition, aggregates formed by this method may be suitable for use in artificial organs or as cell transplants for tissue regeneration.