Spatiotemporal constraints on the force-dependent growth of focal adhesions

Focal adhesions (FAs) are the predominant mechanism by which cells mechanically couple to and exert traction forces on their extracellular matrix (ECM). It is widely presumed that FA size is modulated by force to mediate changes in adhesion strength at different levels of cellular tension. However, previous studies seeking correlations between force and FA morphology have yielded variable and often conflicting results. Here we show that a strong correlation between adhesion size and traction force exists only during the initial stages of myosin-mediated adhesion maturation and growth. For mature adhesions, no correlation between traction stress and size is observed. Rather, the tension that is sustained at mature adhesions is more strongly influenced by proximity to the cell edge, with peripheral adhesions transmitting higher tension than adhesions near the cell center. Finally, we show that mature adhesions can withstand sixfold increases in tension without changes in size. Thus, although a strong correlation between adhesion size and mechanical tension is observed during the initial stages of myosin-mediated adhesion maturation, no correlation is observed in mature, elongated adhesions. This work places spatiotemporal constraints on the force-dependent growth of adhesions and provides insight into the mechanical regulation of cell-ECM adhesion.     

Immunohistochemical detection of PPARgamma receptors in the human pituitary adenomas: correlation with PCNA

The occurrence of peroxisome proliferator-activated receptors gamma (PPARgamma) was investigated in 51 human pituitary adenomas and in 6 non-tumoral human pituitary tissue samples. Moreover, the correlation between PPARgamma and the proliferating cells nuclear antigen (PCNA)--immunocytochemical proliferation marker was evaluated. The receptors and PCNA were detected by immunohistochemical methods using the polyclonal anti-PPARgamma and the monoclonal anti-PCNA antibodies, respectively. PPARgamma were found in all examined tissues. The mean percentage of cells with positive nuclear reaction was 3-fold higher in pituitary adenomas in comparison with non-tumoral pituitary tissues. The strongest expression of PPARgamma was observed in somatotropinomas. Besides the nuclear reaction, which is typical for PPARgamma, positive immunostaining was also observed in the cytoplasm. It was clearly stronger in pituitary adenomas than in non-tumoral pituitary tissues. A slight, statistically insignificant tendency towards negative correlation between PPARgamma and PCNA was found in somatotropinomas, prolactinomas, corticotropinomas and gonadotropinomas. On the other hand, in null cell adenomas and "silent" corticotropinomas, a strong positve correlation between the expression of PPARgamma and PCNA was observed. The strong expression of PPARgamma in human pituitary adenomas and its possible involvement in control of cell proliferation in these tumors give a good reason for the attempts of their treatment with PPARgamma ligands.     

Lack of correlation between seminal and plasma HIV-1 viral loads is associated with CD4 T cell depletion in therapy-naïve HIV-1+ patients

The present study was conducted to investigate a possible correlation between plasma (PVL) and seminal viral load (SVL) on treatment-na?ve HIV-1-infected patients in Vitória, ES, Brazil. We also evaluated whether the progressive immunosuppression associated with HIV disease (as evidenced by declining CD4 T cell counts) has any impact on the correlation between PVL and SVL HIV-1. Viral load on paired blood and semen samples from 56 consecutive treatment-na?ve patients were evaluated and compared to CD4 cell counts. Viral load and T cell counts (cells/microl) were determined by NASBA and by flow cytometry, respectively. Overall, a strong positive correlation between PVL and SVL (rho = 0.438, p = 0.001) was observed. However, when patients were grouped according to their CD4 counts, this correlation was only significant among patients with CD4 counts > 200 cells/microl. Results presented here demonstrate the existence of a strong correlation between PVL and SVL on patients with CD4 cell counts > 200 cells/microl, suggesting that this association may correlate with disease progression.     

From modeling the kinetics of cell enlargement to building tracheidograms of Larix gmelinii Rupr. (Rupr.) in the permafrost zone in Siberia

Boreal forest ecosystems are a crucial element in the global climate balance. In harsh environments functioning lateral meristems of trees are more regulated by the exogenous (included local climate) than endogenous factors. This information is encoded in the tree-ring structure which can be effectively decomposed by the process-based tree-ring growth simulations. Moreover, the process-based modeling can be used to describe non-linear processes linking climate variables with tree-ring formation. In this study, we applied the Vaganov-Shashkin model to simulate seasonal cell production and cell enlargement of Larix gmelinii Rupr. (Rupr.) growing in the permafrost zone of Central Siberia. We developed a procedure for calculating the radial cell diameter based on specific Gompertz function combined with the “instantaneous tracheidogram” approach to estimate effectively seasonal cell production and timing of cell enlargement under climate control. Simulated cell number and cell size matched well with direct xylogenesis observations. The developed procedure demonstrate strong relationships between seasonal simulated growth rate and measured tracheid radial size (the average correlation is 0.64, $p$ < 0.01). A highly significant correlation ($p$ < 0.01) between simulated and observed cell profiles was obtained for 71% of the growing seasons over the period 1950–2011. The strong exponential relationship (R² = 0.67) was obtained between the day of the year (DOY) when cambial cell transfers into enlargement zone and simulated time intervals of cell enlargement. Based on the strong exponential relationship it was possible to reproduce the basic pattern of the observed tracheidograms over 1950–2011 with a systematic overestimation of final cell sizes at the beginning of the growing season, which will be possible to eliminate by using more anatomical data (trees) and longer period. The proposed approach of simulating intra-annual cell dynamics (cell production) has a great potential for studying how climate affects tree-ring formation.     

Non-thermal control of cell thermostability

A survey of literature is made which indicates that various non-thermal influences may significantly affect cell thermostability in both directions. Therefore, special precautions should be taken to be sure that the observed changes in cell thermostability really represent strong negative correlation between the thermostability and the resting membrane potential levels in cells. This correlation implies that changes in cell thermostability, irrespectively of their origin (including those which account for thermal adaptation), are due to changes in the ionic asymmetry and permeability of cells.     

Neutralization of respiratory syncytial virus after cell attachment.

Little is known about the mechanisms of antibody-mediated neutralization of respiratory syncytial virus (RSV) which causes recurrent infections in human despite the virtually universal presence of neutralizing serum antibodies. Human serum neutralization titers showed strong correlation with post-cell-attachment neutralizing titers for both RSV-convalescent sera and control sera but showed less strong correlation with cell-attachment blocking titers. Neutralization was effective for the first 60 min of infection, indicating that immune serum-mediated neutralization of RSV infection largely involves inhibition of early events following cell attachment.     

Unravelling the complexity of T cell abnormalities in common variable immunodeficiency

We investigated several phenotypic and functional parameters of T cell-mediated immunity in a large series of common variable immunodeficiency (CVID) patients. We demonstrated that the vast majority of CVID patients presented multiple T cell abnormalities intimately related among them, the severity of which was reflected in a parallel loss of CD4+ naive T cells. A strong correlation between the number of CD4+ naive T cells and clinical features was observed, supporting the subgrouping of patients according to their number of naive CD4+ T lymphocytes. A reduced thymic output and disrupted CD4+ and CD8+ TCR repertoires paralleled the contraction of CD4+ naive T cell pools. The evaluation of activation markers and cytokine production indicated a strong T cell activation that was significantly related to the increased levels of T cell turnover and apoptosis. Finally, discrete genetic profiles could be demonstrated in groups of patients showing extremely diverse T cell subset composition and function. Naive CD4+ T cell levels were significantly associated with the switched memory B cell-based classification, although the concordance between the respective subgroups did not exceed 58.8%. In conclusion, our data highlight the key role played by the T cell compartment in the pathogenesis of CVID, pointing to the need to consider this aspect for classification of this disease.     

C1,C2-ether derivatives of the Amaryllidaceae alkaloid lycorine: Retention of activity of highly lipophilic analogues against cancer cells

As a continuation of the studies aimed at the development of new anticancer agents derived from the Amaryllidaceae alkaloid lycorine, 35 C1,C2-ether analogues of this natural product were synthesized. The compounds were evaluated for antiproliferative activities in vitro in a panel of tumor cell lines with varied levels of apoptosis resistance. A strong correlation between the compound lipophilicity and anticancer activity was observed, indicating that cell permeability properties must be an important determinant in the design of lycorine-based anticancer agents. A theoretical docking model, consistent with the experimental observations, is presented.     

MACMIC Reveals A Dual Role of CTCF in Epigenetic Regulation of Cell Identity Genes

Numerous studies of relationship between epigenomic features have focused on their strong correlation across the genome, likely because such relationship can be easily identified by many established methods for correlation analysis. However, two features with little correlation may still colocalize at many genomic sites to implement important functions. There is no bioinformatic tool for researchers to specifically identify such feature pairs. Here, we develop a method to identify feature pairs in which two features have maximal colocalization minimal correlation(MACMIC) across the genome. By MACMIC analysis of 3306 feature pairs in 16 human cell types,we reveal a dual role of CCCTC-binding factor(CTCF) in epigenetic regulation of cell identity genes. Although super-enhancers are associated with activation of target genes, only a subset of super-enhancers colocalized with CTCF regulate cell identity genes. At super-enhancers colocalized with CTCF, CTCF is required for the active marker H3 K27 ac in cell types requiring the activation,and also required for the repressive marker H3 K27 me3 in other cell types requiring repression. Our work demonstrates the biological utility of the MACMIC analysis and reveals a key role for CTCF in epigenetic regulation of cell identity. The code for MACMIC is available at https://github.com/bxia888/MACMIC.     

Effect of various glucose/glutamine ratios on hybridoma growth,viability and monoclonal antibody formation

Summary Cultivation of a model hybridoma cell line in Dulbecco's modification of Eagle's minimal essential medium (DMEM) at various glucose and glutamine levels showed that maxmium cell growth was obtained in a broad range of glucose/glutamine ratios of 0.6 to 6.0. A new parameter called the viability index is proposed to quantify cell viability. A strong correlation between viability index and monoclonal antibody (MAb) concentration was found at all glucose/glutamine ratios investigated.     

Influence of interferons on the repair of UV-damaged DNA

The capacity for nucleotide excision repair of a normal (WISH) and three tumour (MCF-7, HeLa, Namalva) cell lines treated with human recombinant interferons (hrIFN-alpha and hrIFN-gamma) was compared by the host cell reactivation assay. The cells were transfected with in vitro UV-damaged plasmid DNA (pEGFP-N1). The repair capacity was determined by measuring the fluorescence intensity of the expressed marker protein in total cell lysates. The correlation between the interferon-induced NO content and the suppressive effect of interferons on DNA repair was shown. The decrease of repair activity and NO induction by hrIFN-alpha were greatest in WISH, followed by MCF-7, Namalva and HeLa cells, whereas hrIFN-gamma was the best NO inducer and inhibitor for the repair of Namalva, followed by WISH, MCF-7 and HeLa cells. Our data clearly show that the two types of interferon have a strong inhibitory effect on the repair of UV-damaged DNA and this effect is cell type-dependent.     

Mutations within the first LSGGQ motif of Ste6p cause defects in a-factor transport and mating in Saccharomyces cerevisiae.

Mating between the two haploid cell types (a and alpha) of the yeast Saccharomyces cerevisiae depends upon the efficient secretion and delivery of the a- and alpha-factor pheromones to their respective target cells. However, a quantitative correlation between the level of transported a-factor and mating efficiency has never been determined. a-Factor is transported by Ste6p, a member of the ATP-binding cassette (ABC) family of transporter proteins. In this study, several missense mutations were introduced in or near the conserved LSGGQ motif within the first nucleotide-binding domain of Ste6p. Quantitation of extracellular a-factor levels indicated that these mutations caused a broad range of a-factor transport defects, and those directly within the LSGGQ motif caused the most severe defects. Overall, we observed a strong correlation between the level of transported a-factor and the mating efficiency of these strains, consistent with the role of Ste6p as the a-factor transporter. The LSGGQ mutations did not cause either a significant alteration in the steady-state level of Ste6p or a detectable change in its subcellular localization. Thus, it appears that these mutations interfere with the ability of Ste6p to transport a-factor out of the MATa cell. The possible involvement of the LSGGQ motif in transporter function is consistent with the strong conservation of this sequence motif throughout the ABC transporter superfamily.     

Methylamine facilitates demonstration of specific uptake of diphtheria toxin by CHO cell and toxin-resistant CHO cell mutants

We have measured the specific uptake of ¹²⁵I-labelled diphtheria toxin in the presence of methylamine by a number of cell lines with different sensitivities to diphtheria toxin. The results show a strong correlation between the toxin sensitivities of the cell lines and the amount of specific uptake. The specific association of labelled toxin with cells was clearly demonstrated even with CHO cells, a cell line with relatively low sensitivity. Thus, CHO cell mutants that are resistant to diphtheria toxin could be classified as toxin-binding or non-binding cells by this method.     

Xenon accumulation in the red blood cell. A process altered by suppressors of the membrane active transport function

Xenon passage across the erythrocyte membrane was investigated by performing several types of tests. The effects of some enzyme inhibitors (ouabain, NaF, dinitrophenol, low temperature), representing various modifications of the mentioned transport phenomenon, led to the conclusion of the existence of a strong correlation between the cellular energetic metabolism (and, hence, the energy supply for membrane processes) and the xenon accumulation into the erythrocyte. The experimental data obtained indicate that the xenon concentration in the cell water exceeds the concentration in the incubation solution by about 20 %. The metabolic inhibitors practically equalise the xenon concentrations in the cell water and in the surrounding medium. The possible theoretical consequences of these facts are taken into account and analysed.     

Expression of vascular endothelial growth factor in the progression of cervical neoplasia and its relation to angiogenesis and p53 status

OBJECTIVE: To evaluate vascular endothelial growth factor (VEGF) expression in the successive steps of cervical neoplasia and to determine its correlation with angiogenesis and p53 status. STUDY DESIGN: Immunohistochemical staining with a VEGF monoclonal antibody was performed on a total of 161 cervical specimens representing 12 normal epithelium, 33 cervical intraepithelial neoplasia (CIN) 1, 30 CIN 3 and 86 squamous cell carcinomas. Microvessels were immunohistochemically labeled with an antibody to CD34. Computerized image analysis was used to evaluate microvessel density (MVD). p53 Status was determined by immunohistochemistry and direct sequencing of exons 5-8 of the p53 gene. RESULTS: VEGF expression progressively increased along the continuum from normal epithelium to squamous cell carcinoma (P < .05). MVD increased significantly with cervical neoplasia progression, from normal epithelium, through CIN, to squamous cell carcinoma (P < .001). A strong correlation was observed between VEGF expression and MVD (P < .001). p53 Protein expression was not detected in the normal epithelium or in CIN 1, while 3 (10%) of 30 CIN 3 and 28 (33%) of 86 squamous cell carcinomas were positive for p53. VEGF expression correlated statistically with p53 protein expression (P < .001). In double VEGF- and p53-stained sections, the 2 markers were generally expressed in the same tumor cells. Of the 4 p53 gene mutations, 3 exhibited strong VEGF expression, and 1 exhibited moderate VEGF expression. VEGF expression did not correlate significantly with outcome variables in patients with squamous cell carcinoma. CONCLUSION: Our results suggest that VEGF expression is involved in the promotion of angiogenesis in cervical neoplasia and that p53 is likely to be involved in the regulation of VEGF expression.     

Studies on the Growth in Culture of Plant Cells: II. CHANGES IN RESPIRATION RATE AND NITROGEN CONTENT ASSOCIATED WITH THE GROWTH OF ACER PSEUDOPLATANUS L. CELLS IN SUSPENSION CULTURE

Changes in nitrogen content and in respiration rate have beeninvestigated in cell suspension cultures of Acer pseudoplatanus.Nitrogen content and rate of oxygen uptake rise sharply earlyin the period of culture, during which there is no significantincrease in dry weight and only a small increase in cell number.During the subsequent period of rapid cell division there isa decline in both respiration rate and nitrogen content permg dry weight or per cell. Pronounced rises in respiration rateand cell nitrogen therefore occur prior to the period of rapidcell division. The strong correlation between nitrogen contentand oxygen consumption suggests that the respiration rate ismuch more closely related to changes in protein content thanto changes in cell number, dry weight, or packed-cell volume.     

On the inadequacy of quinquennial data for analyzing the paternal age effect on Down's dyndrome rates

Summary Investigations of the influence of paternal age on the rate of Down's syndrome are complicated by the high correlation between parental ages and the strong dependence of the incidence rate upon maternal age. Two possible approaches to isolating an independent paternal age effect are shown to lead to erroncous results if based on data by quinquennial age intervals rather than by single-year intervals. For a multiple regression method the discrepancy can be removed by using the mean maternal and mean paternal age within each quinquennial cell. Failure to do so results in an artifactual paternal age effect.