Hypotonic challenge modulates cell volumes differently in the superficial zone of intact articular cartilage and cartilage explant

The objective of this study was to evaluate the effect of sample preparation on the biomechanical behaviour of chondrocytes. We compared the volumetric and dimensional changes of chondrocytes in the superficial zone (SZ) of intact articular cartilage and cartilage explant before and after a hypotonic challenge. Calcein-AM labelled SZ chondrocytes were imaged with confocal laser scanning microscopy through intact cartilage surfaces and through cut surfaces of cartilage explants. In order to clarify the effect of tissue composition on cell volume changes, Fourier Transform Infrared microspectroscopy was used for estimating the proteoglycan and collagen contents of the samples. In the isotonic medium (300 mOsm), there was a significant difference (p < 0.05) in the SZ cell volumes and aspect ratios between intact cartilage samples and cartilage explants. Changes in cell volumes at both short-term (2 min) and long-term (2 h) time points after the hypotonic challenge (180 mOsm) were significantly different (p < 0.05) between the groups. Further, proteoglycan content was found to correlate significantly (r ² = 0.63, p < 0.05) with the cell volume changes in cartilage samples with intact surfaces. Collagen content did not correlate with cell volume changes. The results suggest that the biomechanical behaviour of chondrocytes following osmotic challenge is different in intact cartilage and in cartilage explant. This indicates that the mechanobiological responses of cartilage and cell signalling may be significantly dependent on the integrity of the mechanical environment of chondrocytes.     

Podocalyxin as a Prognostic Marker in Gastric Cancer

Background

Podocalyxin-like 1 (PODXL) is a cell-adhesion glycoprotein associated with aggressive tumor phenotype and poor prognosis in several forms of cancer. The aim of this study was to investigate PODXL expression in gastric cancer by use of two different antibodies.

Methods

By tumor-tissue microarrays and immunohistochemistry we evaluated PODXL expression in tumor specimens from 337 patients who underwent surgery for gastric adenocarcinoma at Helsinki University Hospital. We used two different antibodies: HPA2110, which is a polyclonal antibody and an in-house monoclonal antibody called HES9, to investigate the association of PODXL expression with clinicopathologic variables and patient survival.

Results

PODXL staining was positive by the polyclonal antibody in 153 (57.5%) cases and by the monoclonal antibody in 212 (76%). Polyclonal antibody expression was associated with intestinal cancer type (p<0.001). Monoclonal antibody staining was associated with age over 66 (p = 0.001), with intestinal cancer (p<0.001), and with small tumor size (≤ 5 cm; p = 0.024). Both antibodies were associated with high S-phase fraction (p = 0.022; p = 0.010), and high tumor proliferation index (Ki-67; p = 0.003; p = 0.001). PODXL positivity by the polyclonal antibody indicated reduced gastric-cancer-specific 5-year survival of 24.0% (95% CI 16.9–31.1), compared to 43.3% (95% CI 33.7–52.9) for patients with PODXL negativity (p = 0.001). The result remained significant in multivariable analysis (HR = 3.17; 95% CI 1.37–7.34, p = 0.007).

Conclusion

In gastric cancer, PODXL expression by the polyclonal antibody HPA2110 is an independent marker of poor prognosis.     

Poly-l-glutamic acid derivatives as multifunctional vectors for gene delivery. Part B. Biological evaluation

Cationic polymers, such as poly-l-lysine (pLL) and polyethyleneimine (pEI), are receiving growing attention as vectors for gene therapy. They form polyelectrolyte complexes with DNA, resulting in a reduced size of the DNA and an enhanced stability toward nucleases. The major disadvantages of using both polymers for in vivo purposes are their cytotoxicity and, in the case of pEI, the fact that it's not biodegradable. In this work, we investigated the interaction between a series of cationic, glutamic acid based polymers and red blood cells. The MTT test was used to investigate the cytotoxicity of the complexes. The ability of the polymers to stabilize DNA toward nucleases was investigated. Transfection studies were carried out on Cos-1 cells. The results from the haemolysis studies, the haemagglutination studies, and the MTT assay show that the polymers are substantially less toxic than pLL and pEI. The polymers are able to protect the DNA from digestion by DNase I. The transfection studies show that the polymer-DNA complexes are capable of transfecting cells, most of them with poor efficiency compared to pEI-DNA complexes.     

Recognition of protein folds via dipolar couplings

Alignment of proteins in dilute liquid crystalline medium gives rise to residual dipolar couplings which provide orientational information of vectors connecting the interacting nuclei. Considering that proteins are mainly composed of regular secondary structures in a finite number of different mutual orientations, main chain dipolar couplings appear sufficient to reveal structural resemblance. Similarity between dipolar couplings measured from a protein and corresponding values computed from a known structure imply homologous structures. For dissimilar structures the agreement between experimental and calculated dipolar couplings remains poor. In this way protein folds can be readily recognized prior to a comprehensive structure determination. This approach has been demonstrated by showing the similarity in fold between the hitherto unknown structure of calerythrin and sarcoplasmic calcium-binding proteins from Nereis diversicolor and Branchiostoma lanceolatum with known crystal structures.     

The driving force behind genomic diversity

Eukaryote genomes contain excessively introns, intergenic and other non-genic sequences that appear to have no vital functional role or phenotype manifestation. Their existence, a long-standing puzzle, is viewed from the principle of increasing entropy. According to thermodynamics of open systems, genomes evolve toward diversity by various mechanisms that increase, decrease and distribute genomic material in response to thermodynamic driving forces. Evolution results in an excessive genome, a high-entropy ecosystem of its own, where copious non-coding segments associate with low-level functions and conserved sequences code coordinated activities. The rate of entropy increase, equivalent to the rate of free energy decrease, is identified with the universal fitness criterion of natural selection that governs populations of genomic entities as well as other species.     

Development of Barrett's esophagus after 'spontaneous' healing of atrophic corpus gastritis

We report here the case of a 58-year-old asymptomatic male smoker who had a gastroscopy performed in 1990 because of a low serum pepsinogen I level (16 microg/l). The patient had severe atrophic corpus gastritis and elevated Helicobacter pylori antibody titers, but no histologic evidence of the bacteria. Additionally, a hiatal hernia without esophagitis was seen. He was followed up endoscopically because of the atypical changes (indefinite for dysplasia) in addition to atrophic gastritis in some of the gastric biopsy samples. During the follow-up period, H. pylori antibody titers declined to normal levels without eradication therapy, and atrophic gastritis healed. The patient developed first erosive esophagitis, and, 5 years later, a 3-cm-long Barrett's esophagus was detected.     

Retina-specific gene expression and improved DNA transfection in WERI-Rb1 retinoblastoma cells

We have studied retina-specific gene expression and gene promoter activity in WERI-Rb1 retinoblastoma cells. In general, the expression of endogenous genes matched the efficiency of promoter activity of the transfected gene: interphotoreceptor retinoid binding protein and phosphodiesterase-beta mRNAs and reporter activities were readily detected while other retina-specific messages were at or below the detection limit in WERI-Rb1 cells. Phosphodiesterase-beta promoter appeared active in all six cell lines tested. The viral SV40 promoter is very weak in WERI-Rb1 cells, which has implications for its use in gene constructs targeted to the photoreceptors. Our results also show that polyethyleneimine 25 is an efficient and simple carrier for DNA. The optimized transfection conditions permit the use of 24-well plates and low amounts of DNA for improved analysis of promoter activities, as compared to previous studies. Our results are expected to facilitate further research on retina-specific gene expression.     

Natural distribution

Log-normal distributions describe data from diverse disciplines of science. However, the fundamental basis of log-normal distributions is unknown. We suggest that the skewed distributions are outcomes of natural processes i.e. they result from the principle of increasing entropy. Fluctuations during the course of evolution toward more probable states yield multiplicative variations about the mean. The non-linear dispersion of thermodynamic states, i.e. matter and energy defined by chemical potentials, underlies the skew. Cumulative curves of skewed distributions without integrable analytical forms are characteristic of natural processes.