Direct Cause-effect Relationship Research Articles

Effect of Small-Scale Turbulence on the Physiology and Morphology of Two Bloom-Forming Cyanobacteria.

The main goal of the present work is to test the hypothesis that small-scale turbulence affected physiological activities and the morphology of cyanobacteria in high turbulence environments. Using quantified turbulence in a stirring device, we conducted one set of experiments on cultures of two strains of cyanobacteria with different phenotypes; i.e., unicellular Microcystis flos-aquae and colonial Anabaena flos-aquae. The effect of small-scale turbulence examined varied from 0 to 8.01×10−2 m2s-3, covering the range of turbulence intensities experienced by cyanobacteria in the field. The results of photosynthesis activity and the cellular chlorophyll a in both strains did not change significantly among the turbulence levels, indicating that the potential indirect effects of a light regime under the gradient of turbulent mixing could be ignored. However, the experiments demonstrated that small-scale turbulence significantly modulated algal nutrient uptake and growth in comparison to the stagnant control. Cellular N and C of the two stains showed approximately the same responses, resulting in a similar pattern of C/N ratios. Moreover, the change in the phosphate uptake rate was similar to that of growth in two strains, which implied that growth characteristic responses to turbulence may be dependent on the P strategy, which was correlated with accumulation of polyphosphate. Additionally, our results also showed the filament length of A. flos-aquae decreased in response to high turbulence, which could favor enhancement of the nutrient uptake. These findings suggested that both M. flos-aquae and A. flos-aquae adjust their growth rates in response to turbulence levels in the ways of asynchronous cellular stoichiometry of C, N, and P, especially the phosphorus strategy, to improve the nutrient application efficiency. The fact that adaptation strategies of cyanobacteria diversely to turbulence depending on their physiological conditions presents a good example to understand the direct cause—effect relationship between hydrodynamic forces and algae.

“Excess” Vo2

During whole-body physical activity (e.g. cycling) exercise capacity is reduced by an “excess” in oxygen cost (VO2) relative to power output (PO) (i.e. higher VO2/PO ratio) that appears above the lactate threshold (LT). This loss of muscle efficiency, of which type I fibers fatigue and/or increased type II fibers recruitment are putative causes, impairs exercise tolerance. PURPOSE: We tested the hypothesis that a strength training intervention (ST), by increasing maximal force (Fmax) and reducing the recruitment of high-threshold motor units at a given exercise intensity will reduce the “excess” VO2 during a cycling incremental exercise. METHODS: 16 young healthy males were randomly assigned to a control (C) and a strength-training (ST) group (three, one-hour sessions per week). Pre and Post a 5-weeks intervention, VO2/PO relationship during an incremental test to exhaustion was modelled using a double-linear fit: the slopes of the VO2/PO relationship below (S1) and above (S2) the LT were calculated. Peak power deficit ([[Unsupported Character - Symbol Font ]]PO) was calculated as: (maximal aerobic power as estimated based on VO2max and VO2/PO ratio below LT) – (experimentally attained POmax). Parameters were compared using two-way (time, group) MANOVA. RESULTS: Regarding the ST group: Fmax significantly increased (15 ± 5% for squat) while VO2max and POmax did not change (overall mean 3317 ± 405 mlmin−1 and 318 ± 31 watt respectively). A significant “excess” VO2 was present Pre (S2 significantly higher than S1: 9.6 ± 1.4 vs 7.4 ± 1.1 mlmin−1W−1) and disappeared Post training (S2 not different from S1: 7.7 ± 0.7 vs 7.4 ± 0.4 mlmin−1W−1) along with a significant reduction in [INCREMENT]PO (30 ± 20 vs 8 ± 5 W). No changes were detected for the C group. CONCLUSIONS: In agreement with our hypothesis, ST significantly reduced the “excess” VO2 during a cycling incremental exercise. Although further studies are warranted to identify a direct cause-effect relationship, this finding support a role of ST in improving aerobic exercise capacity through an attenuation of muscle inefficiency in the heavy-exercise domain.

Enfermedades sensibles al clima, Distrito Metropolitano de Quito, un análisis temporal en el periodo 2001-2010

En las últimas décadas, una serie de enfermedades han sido relacionadas con el cambio climático en diferentes partes del mundo, sin embargo establecer una relación directa causa-efecto entre clima y enfermedad no resulta sencillo. El presente estudio investigó la relación entre enfermedades sensibles al clima, variables climáticas y variables de contaminación atmosférica en el Distrito Metropolitano de Quito (DMQ). El diseño de estudio fue de tipo ecológico, se evaluó la evolución de enfermedades sensibles al clima en la zona urbana del DMQ a lo largo del periodo 2001 – 2010. Al analizar los resultados, se encontró un incremento en la ocurrencia de enfermedades relacionadas con la radiación solar, enfermedades respiratorias y enfermedades alérgicas. Las enfermedades respiratorias y alérgicas presentaron asociaciones positivas con variables climáticas y variables de contaminación atmosférica en el DMQ. Es muy probable que, en los próximos años, aquellas enfermedades como las respiratorias y alérgicas sean las más susceptibles al impacto del cambio climático en el DMQ.

MCL-1 dependency of cisplatin-resistant cancer cells

The selection of human cancer cell lines in cis-diamminedichloroplatinum(II) (CDDP, best known as cisplatin) is accompanied by stereotyped alterations that contribute to the acquisition of a CDDP-resistant state. Thus, CDDP resistance often leads to the upregulation of the DNA repair enzyme poly (ADP-ribose) polymerase-1 (PARP1) with the consequent intracellular accumulation of poly (ADP-ribose) (PAR)-modified proteins. Here we report another frequent alteration accompanying CDDP resistance, namely upregulation of the antiapoptotic BCL-2 family protein MCL-1. Six out of 8 CDDP resistant cancer cell lines manifested an increase in MCL-1 protein expression level, while only a minority of cell lines overexpressed BCL-2 or BCL-XL. BCL-XL was decreased in six out of 8 cancer cell lines. Importantly, MCL-1 overexpressing, CDDP resistant cells appear to be ‘addicted’ to MCL-1 because they died upon depletion of MCL-1 by RNA interference or pharmacological inhibition of MCL-1 expression by the BH3 mimetic obatoclax. Knockdown of PARP1 did not succeed in reducing MCL-1 expression, while depletion or inhibition of MCL-1 failed to affect the activity of PARP1. Hence, the two resistance mechanisms are not linked to each other by a direct cause-effect relationship. Importantly, CDDP-resistant, MCL-1 overexpressing human non-small cell lung cancers responded to monotherapy with obatoclax in vivo, in xenotransplanted mice, underscoring the probable therapeutic relevance of these findings.

Alcohol Abuse and Oral Cancer

Background: Various medical, psychiatric and social problems affecting abuser tend to overshadow their health. From an epidemiologic viewpoint, chronic of alcoholic beverages is associated with an increased risk for the upper gastrointestinal tract and tobacco and are regarded as the major risk factors for cancer. The objective of this presentation is to express different hypotheses proposed to explain how ethanol, via or systemic route, can act as a risk factor for the development of cancer. Methods: A web-based search for all types of articles published was initiated using Medline/PubMed, with the keywords such as oral cancer, alcohol consumption and prevention. The search was restricted to English articles published up to December 2013. Results: Various hypotheses have been proposed in the explanation for ethanol acting as a risk factor, locally or systemically, in the development of cancer. The main local effects of ethanol are: increase in mucosa permeability, action of acetaldehyde, and the role of retinoid and the most important systemic effects are: liver suppression and salivary gland dysfunction. Alcohol and tobacco are considered as two principal risk factors in the development of cancer. Ethanol itself is not carcinogenic. However, its first metabolite (acetaldehyde) has recently been shown to be a local carcinogen in humans. Establishing a direct cause-effect relationship between both entities turns out to be difficult. This is due to the frequent association of with other risk bearing practices such as cigarette smoking. The in contact with the mucosa is capable of producing an alteration in morphology characterized by an epithelial atrophy, which means an increase in the susceptibility of the said tissue against other carcinogenic chemicals. In this manner, it was suggested that ethanol is capable of increasing the penetration of carcinogens through the mucosa. Conclusion: A large body of evidence from epidemiological studies of different designs and conducted in different populations has consistently supported that is strongly associated with an increase in risk of and pharyngeal cancer.

Paraneoplastic neurological syndromes in lymphoid neoplasms: a clinical and laboratorial challenge.

Paraneoplastic neurological syndromes in lymphoid neoplasms: a clinical and laboratorial challenge.

Game-theoretic Model on a Cognitive Map and its Tolerance to Errors in Input Data

Some problems of complex control in the fields connected with public life (i.e., social-economic, political and other fields) include semistructured control object. Situation appears semistructured if the basic parameters have qualitative (not quantitative) nature, and their values are subjective expert evaluations. Cognitive maps serve to solve control problems for semistructured situations. Cognitive map is a model representing knowledge of the expert (or a group of experts) regarding situation; this model is described in the form of weighted directed graph. The nodes of cognitive map correspond to those concepts being employed to describe the situation. The concept may be treated as a variable (for instance, “national defence capacity”) which may have different values, such as “high,” “low” and so on. Weighted arc is interpreted as direct cause-effect relationship between two concepts. Suppose several decision-makers (agents) take part in the process of decision making in an semistructured situation given that the utility of each of them depends both on his self actions and the actions of the others, than interactions of the agents can be seen as a game on the cognitive map. In the game cognitive map represents a model of semistructured control object and clearly describe the dynamics of the situation. The use of cognitive maps in the game gives more detailed and visual modeling of the conflict environment in the form of simple causal links, so as to describe the goals and strategies of the agents in terms of the environment which makes it more convenient to model the real conflicts adequately. Since the input data for the model are expert evaluation prone to subjectiveness, it is necessary to estimate the tolerance of model results to errors in input data. Experts evaluate the “importance percentage” of a target concept compared the others target concepts and the weight of edges in cognitive map. The sign of edge weight indicates the type of the causal link and the value of edge weight indicates the strength of the causal link. In this paper we consider the problem of model tolerance to errors in input data and illustrate it on the material of conflict of interests between Russia and Norway in the Barents Sea.

Protein cross‐talk in CD133+ colon cancer cells indicates activation of the Wnt pathway and upregulation of SRp20 that is potentially involved in tumorigenicity

The cancer stem cell (CSC) theory represents a breakthrough in cancer research. We characterized the protein pattern of CSCs to identify specific intracellular pathways in this subpopulation of tumor cells. We studied colon CSCs using two different colon cancer cell lines: CaCo-2 and HCT-116. Putative CSCs were separated from non-CSCs by flow cytometry using CD133 as stemness marker. Total protein extracts of CD133+ cells were then compared to protein extracts of CD133- cells by 2D DIGE. The protein spots differentially expressed in the two subpopulations of cells were analyzed by mass spectrometry. Bioinformatics analysis of the identified proteins indicated alteration of two main processes: energy metabolism and the Wnt pathway. Interestingly, we observed upregulation of the splicing factor SRp20, a newly identified target gene of the Wnt/β-catenin pathway, and we demonstrated a direct cause-effect relationship between Wnt pathway activation and the increased SRp20 expression. Our results also show that SRp20 influences cell proliferation, which suggests it plays a role in the tumorigenicity of CD133+ cells. In conclusion, activation of the Wnt pathway in CD133+ cells and upregulation of SRp20, which is implicated in tumorigenesis, raises the possibility of a sequential series of molecular events occurring in connection with this process.

Are Phosphodiesterase Type 5 Inhibitors Associated with Vision‐Threatening Adverse Events? A Critical Analysis and Review of the Literature

Phosphodiesterase type 5 (PDE5) inhibitors are the first line drugs for treatment of erectile dysfunction. Sildenafil (Viagra(R)), tadalafil (Cialis(R)), and vardenafil (Levitra(R)) are from the same class of drugs that inhibit PDE5. Transient visual symptoms such as change in color perception and increased light sensitivity are well-known adverse effects of these drugs and occur in 3-11% of sildenafil users. Vision-threatening (serious) ocular complications, such as nonarteritic ischemic optic neuropathy and cilio-retinal artery occlusion have rarely been reported in PDE5 inhibitor users. To highlight and analyze the most recently published case literature on serious ocular complications of PDE5 inhibitors. Search of the peer-reviewed English literature was conducted using Medline. The following databases also were searched: Cumulative Index to Nursing and Allied Health Literature, Cochrane Library, Global Health, and MD Consult. The causality assessment of the reported adverse drug reactions was analyzed by applying both the World Health Organization (WHO) Probability Scale and the criteria utilized by the National Registry of Drug-Induced Ocular Side Effects. To scientifically and objectively find out if PDE5 inhibitors are associated with vision-threatening ocular complications. Eight case reports of serious PDE5 inhibitor-associated ocular complications were identified since January 2006 until February 2011. Case reports included cases of anterior and posterior nonarteritic ischemic optic neuropathy, central retinal vein occlusion, cilio-retinal artery occlusion, acute angle closure glaucoma and optic atrophy after sildenafil use. There is lack of conclusive evidence to indicate a direct cause-effect relationship between PDE5 inhibitor use and vision-threatening ocular events. Men who use PDE5 inhibitors appear to suffer vision-threatening complications at the same frequency as the general population. However, minor visual adverse effects occur in 3-11% of users and they are transient and reversible.

Matrix remodeling stimulates stromal autophagy, “fueling” cancer cell mitochondrial metabolism and metastasis

We have previously demonstrated that loss of stromal caveolin-1 (Cav-1) in cancer-associated fibroblasts is a strong and independent predictor of poor clinical outcome in human breast cancer patients. However, the signaling mechanism(s) by which Cav-1 downregulation leads to this tumor-promoting microenvironment are not well understood. To address this issue, we performed an unbiased comparative proteomic analysis of wild-type (WT) and Cav-1-/- null mammary stromal fibroblasts (MSFs). Our results show that plasminogen activator inhibitor type 1 and type 2 (PAI-1 and PAI-2) expression is significantly increased in Cav-1-/- MSFs. To establish a direct cause-effect relationship, we next generated immortalized human fibroblast lines stably overexpressing either PAI-1 or PAI-2. Importantly, PAI-1/2(+) fibroblasts promote the growth of MDA-MB-231 tumors (a human breast cancer cell line) in a murine xenograft model, without any increases in angiogenesis. Similarly, PAI-1/2(+) fibroblasts stimulate experimental metastasis of MDA-MB-231 cells using an in vivo lung colonization assay. Further mechanistic studies revealed that fibroblasts overexpressing PAI-1 or PAI-2 display increased autophagy (“self-eating”) and are sufficient to induce mitochondrial biogenesis/activity in adjacent cancer cells, in co-culture experiments. In xenografts, PAI-1/2(+) fibroblasts significantly reduce the apoptosis of MDA-MB-231 tumor cells. The current study provides further support for the “Autophagic Tumor Stroma Model of Cancer” and identifies a novel “extracellular matrix”-based signaling mechanism, by which a loss of stromal Cav-1 generates a metastatic phenotype. Thus, the secretion and remodeling of extracellular matrix components (such as PAI-1/2) can directly regulate both (1) autophagy in stromal fibroblasts and (2) epithelial tumor cell mitochondrial metabolism.

Intraoperative Brainstem Auditory Evoked Potential Observations After Trigeminocardiac Reflex During Cerebellopontine Angle Surgery

The occurrence of trigeminocardiac reflex (TCR) is known to be a negative prognostic factor for hearing preservation in cerebellopontine angle tumor surgery. Our study was conducted to investigate brainstem auditory evoked potential (BAEP) changes after this reflex in cerebellopontine angle tumor surgery and to evaluate their impact on postoperative hearing function. Five of 102 consecutive patients had an intraoperative TCR (4.9%) and were retrospectively evaluated for the intraoperative BAEP changes after TCR and postoperative auditory function (7 to 10 d after surgery). One of the 5 patients was preoperatively deaf and therefore excluded from this analysis. Four patients with preoperative functional hearing developed one or more episodes of TCR. Intraoperative BAEP was maintained in 1 patient, whereas in 3 cases an acute intraoperative BAEP deterioration occurred within 2:04 to 3:27 minutes (mean 2:44 min) after TCR with increased wave latency, decreased wave amplitude, and even wave loss. Two patients had deteriorated BAEP waves until the surgical completion and were postoperatively deaf. Although no direct cause-effect relationship has yet been shown, we suggest TCR as an additional event that may cause BAEP changes. The observed BAEP alterations occurred minutes rather than seconds after the TCR incident leading to both temporary and permanent wave deterioration. This association of BAEP deterioration and TCR occurrence, however, remains yet to be proven justifying further study in the field.

Evaluation of a support intervention for senior secondary school English immersion

This paper reports on part of an evaluation of a 2-year program providing preparatory support for 430 Cantonese Chinese-native-speaking students switching from Chinese to English-medium instruction late in their secondary schooling, mainly because of aspiration to English-medium tertiary study. Focusing quantitatively and qualitatively on scientific English achievement, the paper addresses the content or cognitive–academic dimension, so far as underrepresented in English-as-foreign-language research, as is senior secondary school immersion itself. While no direct cause-effect relationship between the program and achievement levels was to be claimed, the observed differences between program participants and non-participants were ultimately minimal. Reasons proposed for the intervention’s outcome seemed mainly related to key stakeholders’ apparent limited awareness of cognitive–academic language and its development. The discussion identifies factors arguably crucial for support programs for senior secondary school academic study through English-as-foreign-language.

The influence of the lighting program on broiler activity and dust production

Among the factors influencing dust production on the farms, animal activity is probably the least studied. Animal activity is strongly affected by circadian rhythms and it is altered by the rearing conditions, especially the management of light and the feeding strategy. In this study, a broiler flock was evaluated until 35 d of age with the general objective of studying the factors influencing the production of dust, particularly the effect of animal activity, as affected by the lighting program. In an experimental room, 2 daily dark periods of 6 and 4 h with 158 birds divided in 12 groups, reared on wood shavings, were evaluated. A TEOM analyzer was used to measure dust concentrations, whereas animal activity was determined by observation of birds on video tapes. Animal activity was defined by an activity index, which was determined by direct evaluation of birds on video tapes. The animal activity index was closely related to the lighting program (0.084 and 0.556 during dark and light periods, respectively) and was maximum at wk 4 of the rearing period. The dust concentrations during light periods were on average 4 times higher than during dark periods, with a maximum average concentration of 2.82 mg x m(-3) during the last week of the cycle. Particulate matter emission was on average 2.08 mg x animal(-1) x hour(-1). Dust concentration increased linearly with bird weight and daily variations in dust production were characterized. As a result, a direct cause-effect relationship between animal activity and dust concentration was obtained (r(2) = 0.89).

Prolonged AICAR-induced AMP-kinase activation promotes energy dissipation in white adipocytes: novel mechanisms integrating HSL and ATGL

This study was designed to investigate the effects of prolonged activation of AMP-activated protein kinase (AMPK) on lipid partitioning and the potential molecular mechanisms involved in these processes in white adipose tissue (WAT). Rat epididymal adipocytes were incubated with 5'-aminoimidasole-4-carboxamide-1-beta-d-ribofuranoside (AICAR;0.5 mM) for 15 h. Also, epididymal adipocytes were isolated 15 h after AICAR was injected (i.p. 0.7 g/kg body weight) in rats. Adipocytes were utilized for various metabolic assays and for determination of gene expression and protein content. Time-dependent in vivo plasma NEFA concentrations were determined. AICAR treatment significantly increased AMPK activation, inhibited lipogenesis, and increased FA oxidation. This was accompanied by upregulation of peroxisome proliferator-activated receptor (PPAR)alpha, PPARdelta, and PPARgamma-coactivator-1alpha (PGC-1alpha) mRNA levels. Lipolysis was first suppressed, but then increased, both in vitro and in vivo, with prolonged AICAR treatment. Exposure to AICAR increased adipose triglyceride lipase (ATGL) content and FA release, despite inhibition of basal and epinephrine-stimulated hormone-sensitive lipase (HSL) activity. Here, we provide evidence that prolonged AICAR-induced AMPK activation can remodel adipocyte metabolism by upregulating pathways that favor energy dissipation versus lipid storage in WAT. Additionally, we show novel time-dependent effects of AICAR-induced AMPK activation on lipolysis, which involves antagonistic modulation of HSL and ATGL.

Bottom Up: A Modular View of Immunology

In this issue of Immunity, Chaussabel et al. (2008) apply an inductive approach to pathway discovery identifying modular units that govern human immune biology.

The medical and surgical management of pseudoexfoliation glaucoma.

Pseudoexfoliation (PXF) glaucoma is classically diagnosed by slit lamp visualization of white powdery deposits (PXF material) in a bull’s eye configuration on the lens capsule. PXF glaucoma is the most common form of open-angle worldwide with an identifiable etiology.1 The presence of PXF material is associated with an increased risk of developing glaucoma, but can be present in the eye without associated glaucoma. This disorder also has an association with narrow angles secondary to zonular weakness, increased rate and risk of cataract formation, and increased risk of complications during cataract extraction associated with zonular dehiscence. PXF glaucoma’s primary manifestations and morbidity are ocular. However, PXF is a systemic condition with PXF material present throughout the body. The presence of PXF material has been weakly associated with cardiovascular and cerebrovascular morbidity and sensorineural hearing loss.2–10 Unlike PXF and glaucoma, a direct cause-effect relationship remains to be clearly established between the presence of PXF material and the aforementioned systemic associations. PXF syndrome was first described by Lindbergh in the year 1917, followed by Vogt, and initially termed “glaucoma capsulare.” The classic white flaky dandrufflike material was initially thought to originate from the lens capsule.11 Immunohistologic and electron microscopy studies suggest the PXF material deposited on the lens capsule and throughout the anterior segment of the eye (ie, the angle, corneal endothelium, etc.) is a product of abnormal extracellular matrix material metabolism.1 PXF is distinct from true exfoliation syndrome observed in glass blowers, where a schisis of the anterior lens capsule occurs. Recent molecular and genetic studies have revealed clues as to the molecular pathogenesis of PXF material formation and the association of PXF with the extracellular matrix and cellular metabolism.12,13 This paper reviews current concepts in the medical and surgical management of PXF glaucoma.

Hemolytic uremic syndrome in an infant following Bordetella pertussis infection

Reported here is the case of a 6-week-old female infant with a severe Bordetella pertussis infection requiring supportive pressure-positive ventilation in the intensive care unit. After being discharged from the intensive care unit, she developed hemolytic anemia, thrombocytopenia and acute renal failure, which suggested a diagnosis of hemolytic uremic syndrome. The clinical outcome was favorable with no renal consequences. This case suggests there may be a direct cause-effect relationship between B. pertussis infection and hemolytic uremic syndrome.

Secondary prevention of work-related upper extremity disorders: recommendations from the annapolis conference

Efforts to improve the secondary prevention of work-related upper extremity (WRUE) symptoms continue to present a challenge. As with many occupational musculoskeletal pain disorders no single, direct cause-effect relationship exists among specific exposures, pathologic processes, and symptoms. The field has yet to create truly effective and efficient interventions for these problems that are based on current epidemiological and clinical knowledge. A working conference was held in Annapolis, Maryland on September 23rd and 24th, 2005 with leaders in research and application related to upper extremity disorders to address this challenge. The intent of the meeting was to review "state of the art" evidence in epidemiology and intervention research in order to develop suggestions regarding next steps in intervention research and application. On day 2 a number of stakeholders were present to discuss what they perceived as the missing pieces in both epidemiological research and applied intervention research in order to generate more effective workplace interventions. The papers in this series of the Journal of Occupational Rehabilitation indicate that scientifically sound progress has been made over the past decade in identifying ergonomic, workplace psychosocial, and individual factors in both the etiology and exacerbation of these symptoms/disorders. However, there is a gap between this knowledge and the development and practical implementation of comprehensive interventions for these problems. The conference also highlighted the paucity of economic analyses of the impact of these disorders as well as the economic study of the impact of intervention. Approaches for such evaluations were presented and are included in this special section of the journal. This series of papers and the summary of the invited group's discussions provided in this paper clearly emphasize the need for innovative ways to think about these problems and specific research topics that can help translate this knowledge into effective secondary prevention efforts.

Haemolytic uraemic syndrome is an immune‐mediated disease: role of anti‐CD36 antibodies

Haemolytic uraemic syndrome (HUS) is a disorder in which platelet microthrombi are formed that have a particular propensity to deposit in the kidney microvasculature, resulting in impaired renal function and thrombocytopenia. The mechanism of formation of these microthrombi is not known. In this study, we showed that plasma from five adult and six paediatric cases of HUS caused aggregation and release of adenosine triphosphate from normal platelets. The plasma reacted against platelet lysate in a protein blot and all samples showed reactivity against a band at 88 kDa, corresponding to the membrane antigen CD36. This was confirmed by probing with Mo91, a monoclonal antibody to CD36. CD36 was also identified in the immune complex formed by incubation of patient plasmas with normal platelet lysate. In other studies, bands of 32 and 7.7 kDa were obtained when purified verotoxin was protein blotted and probed with either patient plasma or with anti-CD36 antibody Mo91 suggesting structural homologies between CD36 and verotoxin. While a direct cause-effect relationship is not yet established, the data support the concept of an immunological pathogenesis for HUS and suggest that molecular mimicry involving one or both of the homologous domains in membrane-bound CD36 and verotoxin lead to the development of antibodies capable of inducing the pathophysiological events characteristic of HUS.

Silencing heat shock factor 1 by small interfering RNA abrogates heat shock-induced cardioprotection against ischemia–reperfusion injury in mice

Induction of heat shock factor 1 (HSF1) is known to associate with cellular response to divergent pathophysiological stresses including whole body hyperthermia (WBH) and ischemia-reperfusion. However, a direct cause-effect relationship between HSF1 activation and cytoprotection induced by myocardial preconditioning has not been conclusively established, mainly due to the limitations of available experiment tools. In the present studies, we used a novel approach to block HSF1 with small interfering RNA (siRNA) technique in vivo. Male adult ICR mice were treated intraperitoneally with amine (vehicle) or siRNA specific to HSF1 (siRNA-HSF1). Three days later, WBH preconditioning protocol (rectal temperature 42 °C for 15 min) was applied to these mice under light anesthesia. WBH preconditioning resulted in 2.7-fold and 3.4-fold increase in cardiac HSF1 mRNA and protein expression respectively 2 hours after WBH, which was inhibited in the siRNA-treated mice. The silencing effect of siRNA on HSF1 was associated with complete loss of the infarct- limiting protection by WBH preconditioning after 48 hours. Pretreatment with siRNA-HSF1 had no effect on infarct size in the sham control animals as compared with the amine-treated group. DNA micro-array analysis revealed that siRNA-HSF1 caused a general inhibition on multiple members of HSP family, except Hsp32, Hsp47 and Hsp60. In addition, the silencing effect of siRNA on HSF1 and HSPs gene expression was transient and its inhibitory effect disappeared by 10 days after treatment. siRNA-HSF1 also impaired the thermotolerance of the heat shocked mice as indicated by higher mortality following WBH. For the first time, we have applied siRNA technique in the field of myocardial preconditioning to demonstrate HSF1 activation as an essential step in WBH preconditioning against cardiac ischemia-reperfusion injury.