Western diet, but not high fat diet, causes derangements of fatty acid metabolism and contractile dysfunction in the heart of Wistar rats.

Obesity and diabetes are associated with increased fatty acid availability in excess of muscle fatty acid oxidation capacity. This mismatch is implicated in the pathogenesis of cardiac contractile dysfunction and also in the development of skeletal-muscle insulin resistance. We tested the hypothesis that 'Western' and high fat diets differentially cause maladaptation of cardiac- and skeletal-muscle fatty acid oxidation, resulting in cardiac contractile dysfunction. Wistar rats were fed on low fat, 'Western' or high fat (10, 45 or 60% calories from fat respectively) diet for acute (1 day to 1 week), short (4-8 weeks), intermediate (16-24 weeks) or long (32-48 weeks) term. Oleate oxidation in heart muscle ex vivo increased with high fat diet at all time points investigated. In contrast, cardiac oleate oxidation increased with Western diet in the acute, short and intermediate term, but not in the long term. Consistent with fatty acid oxidation maladaptation, cardiac power decreased with long-term Western diet only. In contrast, soleus muscle oleate oxidation (ex vivo) increased only in the acute and short term with either Western or high fat feeding. Fatty acid-responsive genes, including PDHK4 (pyruvate dehydrogenase kinase 4) and CTE1 (cytosolic thioesterase 1), increased in heart and soleus muscle to a greater extent with feeding a high fat diet compared with a Western diet. In conclusion, we implicate inadequate induction of a cassette of fatty acid-responsive genes, and impaired activation of fatty acid oxidation, in the development of cardiac dysfunction with Western diet.

A conditional Mdm2 allele shows the importance of Mdm2 in heart development

Over 50% of sporadic tumors in humans have a p53 mutation highlighting its importance as a tumor suppressor. Considering additional mutations in other genes involved in p53 pathways, every tumor probably has mutant p53 or impaired p53-mediated functions. In response to a variety of cellular and genotoxic stresses, p53, mainly through its transcriptional activity, induces pathways involved in apoptosis and growth arrest. In these circumstances and under normal situations, p53 must be tightly regulated. Mdm2 is an important regulator of p53. Mdm2 inhibits p53 function by binding and blocking its transactivation domain. In addition, Mdm2 helps target p53 for degradation through its E3 ligase activity. Mdm2 null mice are embryonic lethal due to apoptosis in the blastocysts. However, a p53 null background rescues this lethality demonstrating the importance of the p53-Mdm2 interaction, particularly during development. The lethality of the Mdm2 null mouse prior to implantation limits the ability to investigate the role of Mdm2 in regulating p53 in a temporal and tissue specific manner. Does p53 need to be regulated in all tissues throughout the life of a mouse? Does Mdm2 always have to regulate it? To address these questions, we created a conditional Mdm2 allele. The conditional allele, Mdm2FM, in the presence of Cre recombinase results in the deletion of exons 5 and 6 of Mdm2 (most of the p53 binding domain) and represents a null allele. ^ The Mdm2FM allele was crossed with a heart muscle specific Cre expressing mouse (α-myosin heavy chain promoter driven Cre) to ask whether Mdm2 acts as a negative regulator of p53 in the heart. The heart is the most prominent organ early in embryogenesis and is shaped by cell death and proliferation. p53 does not appear to be active in the heart in response to some types of stress, so it remained to be determined if it has to be regulated in normal heart development. Loss of Mdm2 in the heart results in heart defects as early as E9.5. Loss of Mdm2 results in stabilized p53 and apoptosis. This apoptosis leads to a thinning of the myocardial wall particularly in the ventricles and abnormal ventricular structure. Eventually the abnormal heart fails resulting in lethality by E13.5. The embryonic lethality is rescued in a p53 null background. Thus, Mdm2 is important in regulating p53 in the development of the heart. ^

Activation of calcineurin in human failing heart ventricle by endothelin-1, angiotensin II and urotensin II

1 The calcineurin (CaN) enzyme-transcriptional pathway is critically involved in hypertrophy of heart muscle in some animal models. Currently there is no information concerning the regulation of CaN activation by endogenous agonists in human heart. 2 Human right ventricular trabeculae from explanted human ( 14 male/2 female) failing hearts were set up in a tissue bath and electrically paced at 1Hz and incubated with or without 100 nM endothelin-1 (ET-1), 10 mu M, angiotensin-II (Ang II) or 20 nM human urotensin-II (hUII) for 30 min. Tissues from four patients were incubated with 200 nM tacrolimus (FK506) for 30 min and then incubated in the presence or absence of ET-1 for a further 30 min. 3 ET-1 increased contractile force in all 13 patients (P < 0.001). Ang II and hUII increased contractile force in three out of eight and four out of 10 patients but overall nonsignificantly (P > 0.1). FK506 had no effect on contractile force (P = 0.12). 4 ET-1, Ang II and hUII increased calcineurin activity by 32, 71 and 15%, respectively, while FK506 reduced activity by 34%. ET-1 in the presence of FK506 did not restore calcineurin activity (P = 0.1). 5 There was no relationship between basal CaN activity and expression levels in the right ventricle. Increased levels of free phosphate were detected in ventricular homogenates that were incubated with PKC epsilon compared to samples incubated without PKCe. 6 Endogenous cardiostimulants which activate G alpha q-coupled receptors increase the activity of calcineurin in human heart following acute (30 min) exposure. PKC may contribute to this effect by increasing levels of phosphorylated calcineurin substrate.

The molecular mechanisms utilised by mesenchymal stem cells in migration to acute myocardial infarction

Heart damage caused by acute myocardial infarction (AMI) is a leading cause of death and disability in Australia. Novel therapies are still required for the treatment of this condition due to the poor reparative ability of the heart. As such, cellular therapies that assist in the recovery of heart muscle are of great current interest. Culture expanded mesenchymal stem cells (MSC) represent a stem and progenitor cell population that has been shown to promote tissue recovery in pre-clinical studies of AMI. For MSC-based therapies in the clinic, an intravenous route of administration would ideally be used due to the low cost, ease of delivery and relative safety. The study of MSC migration is therefore clinically relevant for a minimally invasive cell therapy to promote regeneration of damaged tissue. C57BL/6, UBI-GFP-BL/6 and CD44-/-/GFP+/+ mice were utilised to investigate mMSC migration. To assist in murine models of MSC migration, a novel method was used for the isolation of murine MSC (mMSC). These mMSC were then expanded in culture and putative mMSC were positive for Sca-1, CD90.2, and CD44 and were negative for CD45 and CD11b. Furthermore, mMSC from C57BL/6 and UBI-GFP-BL/6 mice were shown to differentiate into cells of the mesodermal lineage. Cells from CD44-/-/GFP+/+ mice were positive for Sca-1 and CD90.2, and negative for CD44, CD45 and CD11b however, these cells were unable to differentiate into adipocytes and chondrocytes and express lineage specific genes, PLIN and ACAN. Analysis of mMSC chemokine receptor (CR) expression showed that although mMSC do express chemokine receptors, (including those specific for chemokines released after AMI), these were low or undetectable by mRNA. However, protein expression could be detected, which was predominantly cytoplasmic. It was further shown that in both healthy (unperturbed) and inflamed tissues, mMSC had very little specific migration and engraftment after intravenous injection. To determine if poor mMSC migration was due to the inability of mMSC to respond to chemotactic stimuli, chemokine expression in bone marrow, skin injury and hearts (healthy and after AMI) was analysed at various time points by quantitative real-time PCR (qRT PCR). Many chemokines were up-regulated after skin biopsy and AMI, but the highest acute levels were found for CXCL12 and CCL7. Due to their high expression in infarcted hearts, the chemokines CXCL12 and CCL7 were tested for their effect on mMSC migration. Despite CR expression at both protein and mRNA levels, migration in response to CXCL12 and CCL7 was low in mMSC cultured on Nunclon plastic. A novel tissue culture plastic technology (UpCellTM) was then used that allowed gentle non-enzymatic dissociation of mMSC, thus preserving surface expression of the CRs. Despite this the in vitro data indicated that CXCL12 fails to induce significant migration ability of mMSC, while CCL7 induces significant, but low-level migration. We speculated this may be because of low levels of surface expression of chemokine receptors. In a strategy to increase cell surface expression of mMSC chemokine receptors and enhance their in vitro and in vivo migration capacity, mMSC were pre-treated with pro-inflammatory cytokines. Increased levels of both mRNA and surface protein expression were found for CRs by pre-treating mMSC with pro-inflammatory cytokines including TNF-á, IFN-ã, IL-1á and IL-6. Furthermore, the chemotactic response of mMSC to CXCL12 and CCL7 was significantly higher with these pretreated cells. Finally, the effectiveness of this type of cell manipulation was demonstrated in vivo, where mMSC pre-treated with TNF-á and IFN-ã showed significantly increased migration in skin injury and AMI models. Therefore this thesis has demonstrated, using in vitro and in vivo models, the potential for prior manipulation of MSC as a possible means for increasing the utility of intravenously delivery for MSC-based cellular therapies.

Cardiomyopathy classification : ongoing debate in the genomics era

Cardiomyopathies represent a group of diseases of the myocardium of the heart and include diseases both primarily of the cardiac muscle and systemic diseases leading to adverse effects on the heart muscle size, shape, and function. Traditionally cardiomyopathies were defined according to phenotypical appearance. Now, as our understanding of the pathophysiology of the different entities classified under each of the different phenotypes improves and our knowledge of the molecular and genetic basis for these entities progresses, the traditional classifications seem oversimplistic and do not reflect current understanding of this myriad of diseases and disease processes. Although our knowledge of the exact basis of many of the disease processes of cardiomyopathies is still in its infancy, it is important to have a classification system that has the ability to incorporate the coming tide of molecular and genetic information. This paper discusses how the traditional classification of cardiomyopathies based on morphology has evolved due to rapid advances in our understanding of the genetic and molecular basis for many of these clinical entities.

Cetuximab plus chemotherapy in patients with advanced non-small-cell lung cancer (FLEX) : an open-label randomised phase III trial

Background: Use of cetuximab, a monoclonal antibody targeting the epidermal growth factor receptor (EGFR), has the potential to increase survival in patients with advanced non-small-cell lung cancer. We therefore compared chemotherapy plus cetuximab with chemotherapy alone in patients with advanced EGFR-positive non-small-cell lung cancer. Methods: In a multinational, multicentre, open-label, phase III trial, chemotherapy-naive patients (≥18 years) with advanced EGFR-expressing histologically or cytologically proven stage wet IIIB or stage IV non-small-cell lung cancer were randomly assigned in a 1:1 ratio to chemotherapy plus cetuximab or just chemotherapy. Chemotherapy was cisplatin 80 mg/m 2 intravenous infusion on day 1, and vinorelbine 25 mg/m 2 intravenous infusion on days 1 and 8 of every 3-week cycle) for up to six cycles. Cetuximab-at a starting dose of 400 mg/m 2 intravenous infusion over 2 h on day 1, and from day 8 onwards at 250 mg/m 2 over 1 h per week-was continued after the end of chemotherapy until disease progression or unacceptable toxicity had occurred. The primary endpoint was overall survival. Analysis was by intention to treat. This study is registered with ClinicalTrials.gov, number NCT00148798. Findings: Between October, 2004, and January, 2006, 1125 patients were randomly assigned to chemotherapy plus cetuximab (n=557) or chemotherapy alone (n=568). Patients given chemotherapy plus cetuximab survived longer than those in the chemotherapy-alone group (median 11·3 months vs 10·1 months; hazard ratio for death 0·871 [95% CI 0·762-0·996]; p=0·044). The main cetuximab-related adverse event was acne-like rash (57 [10%] of 548, grade 3). Interpretation: Addition of cetuximab to platinum-based chemotherapy represents a new treatment option for patients with advanced non-small-cell lung cancer. Funding: Merck KGaA. © 2009 Elsevier Ltd. All rights reserved.

Enhancement of the chemoprotective enzymes glucuronosyl transferase and glutathione transferase in specific organs of the rat by the coffee components kahweol and cafestol

The coffee components kahweol and cafestol (K/C) have been reported to protect the colon and other organs of the rat against the formation of DNA adducts by 2-amino-1-methyl-6-phenylimidazo[4,5-b] pyridine (PhIP) and aflatoxin B1. PhIP is a cooked-food mutagen to which significant human exposure and a role in colon cancer etiology are attributed, and, interestingly, such cancers appear to develop at a lower rate in consumers of coffees with high amounts of K/C. Earlier studies in rodent liver have shown that a key role in the chemopreventive effect of K/C is likely to be due to the potential of these compounds to induce the detoxification of xenobiotics by glutathione transferase (GST) and to enhance the synthesis of the corresponding co-factor glutathione. However, mutagens like PhIP may also be detoxified by UDP-glucuronosyl transferase (UDPGT) for which data are lacking regarding a potential effect of K/C. Therefore, in the present study, we investigated the effect of K/C on UDPGT and, concomitantly, we studied overall GST and the pattern of individual GST classes, particularly GST-θ, which was not included in earlier experiments. In addition, we analyzed the organ-dependence of these potentially chemopreventive effects. K/C was fed to male F344 rats at 0.122% in the chow for 10 days. Enzyme activities in liver, kidney, lung, colon, salivary gland, pancreas, testis, heart and spleen were quantified using five characteristic substrates and the hepatic protein pattern of GST classes α, μ, and π was studied with affnity chromatography/HPLC. Our study showed that K/C is not only capable of increasing overall GST and GST classes α, μ, and π but also of enhancing UDGPT and GST-θ. All investigated K/C effects were strongest in liver and kidney, and some response was seen in lung and colon but none in the other organs. In summary, our results show that K/C treatment leads to a wide spectrum of increases in phase II detoxification enzymes. Notably, these effects occurred preferentially in the well perfused organs liver and kidney, which may thus not only contribute to local protection but also to anti-carcinogenesis in distant, less stimulated organs such as the colon.

Mathematical models on the impact of noise and dyadic molecular structures on the properties of a cardiac myocyte

In cardiac myocytes (heart muscle cells), coupling of electric signal known as the action potential to contraction of the heart depends crucially on calcium-induced calcium release (CICR) in a microdomain known as the dyad. During CICR, the peak number of free calcium ions (Ca) present in the dyad is small, typically estimated to be within range 1-100. Since the free Ca ions mediate CICR, noise in Ca signaling due to the small number of free calcium ions influences Excitation-Contraction (EC) coupling gain. Noise in Ca signaling is only one noise type influencing cardiac myocytes, e.g., ion channels playing a central role in action potential propagation are stochastic machines, each of which gates more or less randomly, which produces gating noise present in membrane currents. How various noise sources influence macroscopic properties of a myocyte, how noise is attenuated and taken advantage of are largely open questions. In this thesis, the impact of noise on CICR, EC coupling and, more generally, macroscopic properties of a cardiac myocyte is investigated at multiple levels of detail using mathematical models. Complementarily to the investigation of the impact of noise on CICR, computationally-efficient yet spatially-detailed models of CICR are developed. The results of this thesis show that (1) gating noise due to the high-activity mode of L-type calcium channels playing a major role in CICR may induce early after-depolarizations associated with polymorphic tachycardia, which is a frequent precursor to sudden cardiac death in heart failure patients; (2) an increased level of voltage noise typically increases action potential duration and it skews distribution of action potential durations toward long durations in cardiac myocytes; and that (3) while a small number of Ca ions mediate CICR, Excitation-Contraction coupling is robust against this noise source, partly due to the shape of ryanodine receptor protein structures present in the cardiac dyad.

Patents, Ethics and Stem Cell Research : The Case of hESC Innovation in Australia, Europe and the United States

Embryonic stem cells offer potentially a ground-breaking insight into health and diseases and are said to offer hope in discovering cures for many ailments unimaginable few years ago. Human embryonic stem cells are undifferentiated, immature cells that possess an amazing ability to develop into almost any body cell such as heart muscle, bone, nerve and blood cells and possibly even organs in due course. This remarkable feature, enabling embryonic stem cells to proliferate indefinitely in vitro (in a test tube), has branded them as a so-called miracle cure . Their potential use in clinical applications provides hope to many sufferers of debilitating and fatal medical conditions. However, the emergence of stem cell research has resulted in intense debates about its promises and dangers. On the one hand, advocates hail its potential, ranging from alleviating and even curing fatal and debilitating diseases such as Parkinson s, diabetes, heart ailments and so forth. On the other hand, opponents decry its dangers, drawing attention to the inherent risks of human embryo destruction, cloning for research purposes and reproductive cloning eventually. Lately, however, the policy battles surrounding human embryonic stem cell innovation have shifted from being a controversial research to scuffles within intellectual property rights. In fact, the ability to obtain patents represents a pivotal factor in the economic success or failure of this new biotechnology. Although, stem cell patents tend to more or less satisfy the standard patentability requirements, they also raise serious ethical and moral questions about the meaning of the exclusions on ethical or moral grounds as found in European and to an extent American and Australian patent laws. At present there is a sort of a calamity over human embryonic stem cell patents in Europe and to an extent in Australia and the United States. This in turn has created a sense of urgency to engage all relevant parties in the discourse on how best to approach patenting of this new form of scientific innovation. In essence, this should become a highly favoured patenting priority. To the contrary, stem cell innovation and its reliance on patent protection risk turmoil, uncertainty, confusion and even a halt on not only stem cell research but also further emerging biotechnology research and development. The patent system is premised upon the fundamental principle of balance which ought to ensure that the temporary monopoly awarded to the inventor equals that of the social benefit provided by the disclosure of the invention. Ensuring and maintaining this balance within the patent system when patenting human embryonic stem cells is of crucial contemporary relevance. Yet, the patenting of human embryonic stem cells raises some fundamental moral, social and legal questions. Overall, the present approach of patenting human embryonic stem cell related inventions is unsatisfactory and ineffective. This draws attention to a specific question which provides for a conceptual framework for this work. That question is the following: how can the investigated patent offices successfully deal with patentability of human embryonic stem cells? This in turn points at the thorny issue of application of the morality clause in this field. In particular, the interpretation of the exclusions on ethical or moral grounds as found in Australian, American and European legislative and judicial precedents. The Thesis seeks to compare laws and legal practices surrounding patentability of human embryonic stem cells in Australia and the United States with that of Europe. By using Europe as the primary case study for lessons and guidance, the central goal of the Thesis then becomes the determination of the type of solutions available to Europe with prospects to apply such to Australia and the United States. The Dissertation purports to define the ethical implications that arise with patenting human embryonic stem cells and intends to offer resolutions to the key ethical dilemmas surrounding patentability of human embryonic stem cells and other morally controversial biotechnology inventions. In particular, the Thesis goal is to propose a functional framework that may be used as a benchmark for an informed discussion on the solution to resolving ethical and legal tensions that come with patentability of human embryonic stem cells in Australian, American and European patent worlds. Key research questions that arise from these objectives and which continuously thread throughout the monograph are: 1. How do common law countries such as Australia and the United States approach and deal with patentability of human embryonic stem cells in their jurisdictions? These practices are then compared to the situation in Europe as represented by the United Kingdom (first two chapters), the Court of Justice of the European Union and the European Patent Office decisions (Chapter 3 onwards) in order to obtain a full picture of the present patenting procedures on the European soil. 2. How are ethical and moral considerations taken into account at patent offices investigated when assessing patentability of human embryonic stem cell related inventions? In order to assess this part, the Thesis evaluates how ethical issues that arise with patent applications are dealt with by: a) Legislative history of the modern patent system from its inception in 15th Century England to present day patent laws. b) Australian, American and European patent offices presently and in the past, including other relevant legal precedents on the subject matter. c) Normative ethical theories. d) The notion of human dignity used as the lowest common denominator for the interpretation of the European morality clause. 3. Given the existence of the morality clause in form of Article 6(1) of the Directive 98/44/EC of the European Parliament and of the Council of 6 July 1998 on the legal protection of biotechnological inventions which corresponds to Article 53(a) European Patent Convention, a special emphasis is put on Europe as a guiding principle for Australia and the United States. Any room for improvement of the European morality clause and Europe s current manner of evaluating ethical tensions surrounding human embryonic stem cell inventions is examined. 4. A summary of options (as represented by Australia, the United States and Europe) available as a basis for the optimal examination procedure of human embryonic stem cell inventions is depicted, whereas the best of such alternatives is deduced in order to create a benchmark framework. This framework is then utilised on and promoted as a tool to assist Europe (as represented by the European Patent Office) in examining human embryonic stem cell patent applications. This method suggests a possibility of implementing an institution solution. 5. Ultimately, a question of whether such reformed European patent system can be used as a founding stone for a potential patent reform in Australia and the United States when examining human embryonic stem cells or other morally controversial inventions is surveyed. The author wishes to emphasise that the guiding thought while carrying out this work is to convey the significance of identifying, analysing and clarifying the ethical tensions surrounding patenting human embryonic stem cells and ultimately present a solution that adequately assesses patentability of human embryonic stem cell inventions and related biotechnologies. In answering the key questions above, the Thesis strives to contribute to the broader stem cell debate about how and to which extent ethical and social positions should be integrated into the patenting procedure in pluralistic and morally divided democracies of Europe and subsequently Australia and the United States.

The profound effects of microcystin on cardiac antioxidant enzymes, mitochondrial function and cardiac toxicity in rat

Deaths from microcystin toxication have widely been attributed to hypovolemic shock due to hepatic interstitial hemorrhage, while some recent studies suggest that cardiogenic complication is also involved. So far, information on cardiotoxic effects of MC has been rare and the underlying mechanism is still puzzling. The present study examined toxic effects of microcystins on heart muscle of rats intravenously injected with extracted MC at two doses, 0.16LD(50) (14 mu g MC-LReq kg(-1) body weight) and 1LD(50) (87 mu g MC-LReq kg(-1) body weight). In the dead rats, both TTC staining and maximum elevations of troponin I levels confirmed myocardial infarction after MC exposure, besides a serious interstitial hemorrhage in liver. In the 1LD(50) dose group, the coincident falls in heart rate and blood pressure were related to mitochondria dysfunction in heart, while increases in creatine kinase and troponin I levels indicated cardiac cell injury. The corresponding pathological alterations were mainly characterized as loss of adherence between cardiac myocytes and swollen or ruptured mitochondria at the ultrastructural level. MC administration at a dose of 1LD(50) not only enhanced activities and up-regulated mRNA transcription levels of antioxidant enzymes, but also increased GSH content. At both doses, level of lipid peroxides increased obviously, suggesting serious oxidative stress in mitochondria. Simultaneously. complex I and III were significantly inhibited, indicating blocks in electron flow along the mitochondrial respiratory chain in heart. In conclusion, the findings of this study implicate a role for MC-induced cardiotoxicity as a potential factor that should be considered when evaluating the mechanisms of death associated with microcystin intoxication in Brazil. (C) 2009 Elsevier Ireland Ltd. All rights reserved.

EST-based identification of genes expressed in the hypothalamus of male orange-spotted grouper (Epinephelus coioides)

The orange-spotted grouper, Epinephelus coioides, is an important marine aquaculture fish, but its large-scale aquaculture has been hindered by the rarity of natural males because it is a protogynous hermaphroditic fish. Hypothalamus-pituitary-gonad is an important endocrine axis in regulating reproduction and sex differentiation. To reveal the molecular mechanism of hypothalamic physiological functions, we performed he studies on identification of genes expressed in the hypothalamus of male orange-spotted grouper using EST and RT-PCR strategy. A total of 1006 ESTs were sequenced, and 402 (39.96%) clones were identified as known genes and 604 (60.04%) as unknown genes. The 402 clones of known gene products represent transcripts of 18 1 genes. Moreover, the expression patterns of 26 unknown genes were analyzed in various tissues, such as liver, kidney, spleen, fat, heart, muscle, pituitary, hypothalamus, telencephalon, cerebellum, midbrain, medulla oblongata, ovary and testes. Five different categories of expression patterns were observed from them. Several unknown ESTs, such as DN551996, DN551998, DN552082, and DN552070, were detected to be hypothalamus-specific, brains-specific, or hypothalamus and gonad-specific genes. Interestingly, DN551996, not only exhibiting expression differences between ovary and testis, but also showing sex-dependent differences in hypothalamus of grouper, might play significant role in grouper reproduction or sex inversion. Further functional studies on these genes will provide more information on molecule regulation mechanism of sex inversion in groupers. (c) 2006 Elsevier B.V All fights reserved.

Charakterystyka ekspresji receptorów scavenger w błonach komórkowych monocytów ludzkich u pacjentów z chorobą niedokrwienną serca

Wydział Biologii: Instytut Biologii Eksperymentalnej

Troubles du rythme cardiaque dans les modèles murins transgéniques

Thèse en cotutelle avec Université de Nantes - Pays de La Loire - France (2005-2010)

Matrix metalloproteinases cleave the beta(2)-adrenergic receptor in spontaneously hypertensive rats

Rodrigues SF, Tran ED, Fortes ZB, Schmid-Schonbein GW. Matrix metalloproteinases cleave the beta(2)-adrenergic receptor in spontaneously hypertensive rats. Am J Physiol Heart Circ Physiol 299: H25-H35, 2010. First published April 9, 2010; doi:10.1152/ajpheart.00620.2009.-We recently observed the enhanced serine and matrix metalloproteinase (MMP) activity in the spontaneously hypertensive rat (SHR) compared with its normotensive Wistar-Kyoto (WKY) rat and the cleavage of membrane receptors in the SHR by MMPs. We demonstrate in vivo that MMP-7 and MMP-9 injection leads to a vasoconstrictor response in microvessels of rats that is blocked by a specific MMP inhibitor (GM-6001, 1 mu M). Multiple pathways may be responsible. Since the beta(2)-adrenergic receptor (beta(2)-AR) is susceptible to the action of endogenous MMPs, we hypothesize that MMPs in the plasma of SHRs are able to cleave the extracellular domain of the beta(2)-AR. SHR arterioles respond in an attenuated fashion to beta(2)-AR agonists and antagonists. Aorta and heart muscle of control Wistar rats were exposed for 24 h (37 C) to fresh plasma of male Wistar and WKY rats and SHRs with and without doxycycline (30 mu M) and EDTA (10 mM) to reduce MMP activity. The density of extracellular and intracellular domains of beta(2)-AR was determined by immunohistochemistry. The density of the extracellular domain of beta(2)-AR is reduced in aortic endothelial cells and cardiac microvessels of SHRs compared with that of WKY or Wistar rats. Treatment of the aorta and the heart of control Wistar rats with plasma from SHRs, but not from WKY rats, reduced the number of extracellular domains, but not intracellular domains, of beta(2)-AR in aortic endothelial cells and cardiac microvessels. MMP inhibitors (EDTA and doxycycline) prevented the cleavage of the extracellular domain. Thus MMPs may contribute to the reduced density of the extracellular domain of beta(2)-AR in blood vessels and to the increased arteriolar tone of SHRs compared with normotensive rats.

Problem-based learning and masculinities : unique opportunities for Mr. Fix It? Well, maybe

I watched a smoker of 30 years being admitted to the Coronary Care unit following an acute Myocardial Infarction (heart attack). The message from the male clinician was simple, accurate, but somewhat behaviourist: " the death of part of your heart muscle is the result of your smoking, if you don’t stop smoking the damage will continue and you will die." A global, proactive and humanistic consultation demonstrating an understanding of the man’s addiction to a legal and accessible drug and illuminating prevention strategies may have been more appropriate. Maybe the interaction was about competing masculinities, the risk taker and the problem solver. The irony? As I left the hospital that night I observed the same clinician strategically positioned in a secluded hospital doorway drawing heavily on a cigarette. Hypocrite? No, invincible late 20’s male? Maybe. Smoking was someone else’s problem – at least today.

In my 16 years as a clinician such scenarios are common. Clinical practice based predominantly on problem solving potentiates hegemonic masculine approaches to treating men in clinical practice, often justified by limited health resources and increasing patient acuity. Ironically, Problem-based Learning (PBL) curriculums commonly used in health sciences higher education encourages, nurtures and rewards such problem solving approaches. As a teaching academic with current clinical practice it occurs to me that health science education and PBL has an opportunity if not obligation to empower clinicians to establish holistic approaches to male health presentations.

This paper explores the interconnections of Problem-based Learning (PBL) curriculums, health promotion, male nurses’ health-related behaviours and the implications and specificities of masculinity. The pilot study offers an insight into the perceptions of three male nurses that completed undergraduate nursing studies in PBL curriculums. The data obtained introduces some connections that could be illuminated by further research.