Three-dimensional myocardial strain correlates with murine left ventricular remodelling severity post-infarction.

Heart failure continues to be a common and deadly sequela of myocardial infarction (MI). Despite strong evidence suggesting the importance of myocardial mechanics in cardiac remodelling, many MI studies still rely on two-dimensional analyses to estimate global left ventricular (LV) function. Here, we integrated four-dimensional ultrasound with three-dimensional strain mapping to longitudinally characterize LV mechanics within and around infarcts in order to study the post-MI remodelling process. To induce infarcts with varying severities, we separated 15 mice into three equal-sized groups: (i) sham, (ii) 30 min ischaemia-reperfusion, and (iii) permanent ligation of the left coronary artery. Four-dimensional ultrasound from a high-frequency small animal system was used to monitor changes in LV geometry, function and strain over 28 days. We reconstructed three-dimensional myocardial strain maps and showed that strain profiles at the infarct border followed a sigmoidal behaviour. We also identified that mice with mild remodelling had significantly higher strains in the infarcted myocardium than those with severe injury. Finally, we developed a new approach to non-invasively estimate infarct size from strain maps, which correlated well with histological results. Taken together, the presented work provides a thorough approach to quantify regional strain, an important component when assessing post-MI remodelling.

Steroid-Refractory Autoimmune Myocarditis after Pembrolizumab Therapy: Failure of Equine Anti-Thymocyte Globulin to Prevent Heart Failure.

While immune checkpoint inhibitors (ICIs) are improving outcomes for many cancers, they can have severe adverse effects. Though cardiac immune-related adverse effects (irAEs) are rare, they have considerable morbidity and mortality. Prior case studies have demonstrated successful treatment of ICI induced autoimmune myocarditis with a variety of immunosuppressive regimens. This case describes steroid-refractory autoimmune myocarditis after treatment with pembrolizumab. Treatment with equine anti-thymocyte globulin, a regimen previously documented to reverse ICI induced autoimmune myocarditis, temporarily improved clinical status and cardiac biomarkers, however eventually failed to prevent progression to heart failure and cardiovascular death. This case highlights the importance of early stress-dose steroids, identifies troponin as a potential marker of treatment response, and underscores the value of collaboration between oncology and cardiology for optimal management.

Hematopoietic stem cell transplant-associated thrombotic microangiopathy: current paradigm and novel therapies.

Hematopoietic stem cell transplantation-associated thrombotic microangiopathy (TA-TMA) remains a difficult complication to address due to its high mortality rate, lack of standard diagnostic criteria and limited therapeutic options. Underscoring this challenge is the complex pathophysiology involved and multiple contributing factors that converge on a final pathway involving widespread endothelial injury and complement activation. In addressing our current understanding of TA-TMA, we highlight the risk factors leading to endothelial damage and a pathophysiological cascade that ensues. We have also compared the different definition criteria and biomarkers that can enable early intervention in TA-TMA patients. Current first-line management includes discontinuation or alteration of the immunosuppressive regimen, treatment of co-existing infectious and GVHD, aggressive hypertension control and supportive therapy. We discuss current pharmacological therapies, including newer agents that target the complement cascade and nitric oxide pathways.

Wake-up Strokes Are Similar to Known-Onset Morning Strokes in Severity and Outcome.

BACKGROUND: Stroke symptoms noticed upon waking, wake-up stroke, account for up to a quarter of all acute ischemic strokes. Patients with wake-up stroke, however, are often excluded from thrombolytic therapy. METHODS: Using our prospectively collected stroke registry, wake-up stroke and known-onset morning strokes were identified. Wakeup stroke was defined as a patient who was asleep >3 hours and first noted stroke symptoms upon awakening between 0100 and 1100. Known-onset morning stroke was defined as a patient who had symptom onset while awake during the same time interval. We compared wake-up stoke to known-onset morning stroke with respect to patient demographics, stroke severity, etiology and outcomes. RESULTS: One-quarter of patients with acute ischemic strokes (391/1415) had documented time between 0100 and 1100 of symptom onset: 141 (36%) wake-up strokes and 250 (64%) known-onset morning strokes. No difference in baseline characteristics, stroke severity, stroke etiology, neurologic deterioration, discharge disposition or functional outcome was detected. Known-onset morning stroke patients were significantly more likely to get thrombolytic therapy and have higher risk of in-hospital mortality. Wake-up stroke patients tended to be older, have higher diastolic blood pressure and have longer length of hospital stay. DISCUSSION: While patients with wake-up stroke were similar to patients with known-onset morning stroke in many respects, patients with known onset morning stroke were significantly more likely to get treated with thrombolytic therapy and have higher in-hospital mortality.

Angiogenic responses are enhanced in mechanically and microscopically characterized, microbial transglutaminase crosslinked collagen matrices with increased stiffness.

During angiogenesis, endothelial cells (ECs) use both soluble and insoluble cues to expand the existing vascular network to meet the changing trophic needs of the tissue. Fundamental to this expansion are physical interactions between ECs and extracellular matrix (ECM) that influence sprout migration, lumen formation and stabilization. These physical interactions suggest that ECM mechanical properties may influence sprouting ECs and, therefore, angiogenic responses. In a three-dimensional angiogenic model in which a monolayer of ECs is induced to invade an underlying collagen matrix, angiogenic responses were measured as a function of collagen matrix stiffness by inducing collagen crosslinking with microbial transglutaminase (mTG). By biaxial mechanical testing, stiffer collagen matrices were measured with both mTG treatment and incubation time. Using two-photon excited fluorescence (TPF) and second harmonic generation (SHG), it was shown that collagen TPF intensity increased with mTG treatment, and the TPF/SHG ratio correlated with biaxially tested mechanical stiffness. SHG and OCM were further used to show that other ECM physical properties such as porosity and pore size did not change with mTG treatment, thus verifying that matrix stiffness was tuned independently of matrix density. The results showed that stiffer matrices promote more angiogenic sprouts that invade deeper. No differences in lumen size were observed between control and mTG stiffened matrices, but greater remodeling was revealed in stiffer gels using SHG and OCM. The results of this study show that angiogenic responses are influenced by stiffness and suggest that ECM properties may be useful in regenerative medicine applications to engineer angiogenesis.

Prevalence, sensitivity, and specificity of chronic cerebrospinal venous insufficiency in MS.

BACKGROUND: Chronic cerebrospinal venous insufficiency (CCSVI) was recently described in patients with multiple sclerosis (MS). A subject is considered CCSVI positive if ≥ 2 venous hemodynamic (VH) criteria are fulfilled. OBJECTIVE: To determine prevalence of CCSVI in a large cohort of patients with MS, clinically isolated syndrome (CIS), other neurologic diseases (OND), and healthy controls (HC), using specific proposed echo-color Doppler (ECD) criteria. METHODS: Transcranial and extracranial ECD were carried out in 499 enrolled subjects (289 MS, 163 HC, 26 OND, 21 CIS). Prevalence rates for CCSVI were calculated in 3 ways: first, using only the subjects for whom diagnosis was certain (i.e., borderline subjects were excluded); secondly, including the borderline subjects in the "no CCSVI" group; and finally, taking into account subjects who presented any of the VH criteria. RESULTS: CCSVI prevalence with borderline cases included in the "no CCSVI" group was 56.1% in MS, 42.3% in OND, 38.1% in CIS, and 22.7% in HC (p < 0.001). The CCSVI prevalence figures were 62.5% for MS, 45.8% for OND, 42.1% for CIS, and 25.5% for HC when borderline cases were excluded (p < 0.001). The prevalence of one or more positive VH criteria was the highest in MS (81.3%), followed by CIS (76.2%), OND (65.4%), and HC (55.2%) (p < 0.001). CCSVI prevalence was higher in patients with progressive than in nonprogressive MS (p = 0.004). CONCLUSIONS: Our findings are consistent with an increased prevalence of CCSVI in MS but with modest sensitivity/specificity. Our findings point against CCSVI having a primary causative role in the development of MS.

Haploinsufficiency of RanBP2 is neuroprotective against light-elicited and age-dependent degeneration of photoreceptor neurons.

Prolonged light exposure is a determinant factor in inducing neurodegeneration of photoreceptors by apoptosis. Yet, the molecular bases of the pathways and components triggering this cell death event are elusive. Here, we reveal a prominent age-dependent increase in the susceptibility of photoreceptor neurons to undergo apoptosis under light in a mouse model. This is accompanied by light-induced subcellular changes of photoreceptors, such as dilation of the disks at the tip of the outer segments, prominent vesiculation of nascent disks, and autophagy of mitochondria into large multilamellar bodies. Notably, haploinsufficiency of Ran-binding protein-2 (RanBP2) suppresses apoptosis and most facets of membrane dysgenesis observed with age upon light-elicited stress. RanBP2 haploinsufficiency promotes decreased levels of free fatty acids in the retina independent of light exposure and turns the mice refractory to weight gain on a high-fat diet, whereas light promotes an increase in hydrogen peroxide regardless of the genotype. These studies demonstrate the presence of age-dependent and RanBP2-mediated pathways modulating membrane biogenesis of the outer segments and light-elicited neurodegeneration of photoreceptors. Furthermore, the findings support a mechanism whereby the RanBP2-dependent production of free fatty acids, metabolites thereof or the modulation of a cofactor dependent on any of these, promote apoptosis of photoreceptors in concert with the light-stimulated production of reactive oxygen species.

Normal basilar artery structure and biaxial mechanical behaviour.

Much is known about cerebral vasospasm, a devastating sequela to ruptured intracranial aneurysms, yet underlying mechanisms remain unclear and clinical treatments have proven unsatisfactory. We have hypothesised that biochemical stimuli associated with the formation of extravascular blood clots dominate early maladaptive responses, leading to marked structural and functional changes in affected cerebral arteries. Before a precise picture of vasospasm can be obtained, however, we must understand better the structure and mechanical behaviour of normal cerebral arteries. Basilar arteries from rabbits were tested mechanically under biaxial loading conditions with and without active tone, segments were imaged using intravital nonlinear optical microscopy to quantify transmural orientations of fibrillar collagen, and passive mechanical data were fit with a four-fiber family stress-stretch relation. This constitutive model predicted well the overall mechanical behaviour and mean collagen fiber distributions, and thereby has promise to contribute to analyses of the biochemomechanics of cerebral vasospasm and similar cerebral pathologies. It is now time, therefore, to focus on mechanisms of vasospasm via mathematical models that incorporate growth and remodelling in terms of changes in the cross-linking and distributions of adventitial and medial collagen, primary contributors to the structural integrity of the arterial wall.

A theoretically-motivated biaxial tissue culture system with intravital microscopy.

Many cell types produce, remodel, and degrade extracellular matrix in response to diverse stimuli, including mechanical loads. Much is known about the molecular biology and biochemistry of the deposition and degradation of collagen, the primary structural constituent of the extracellular matrix in many tissues, yet there has been little modeling of the associated mechanobiology. For example, we do not have quantitative descriptions, or rules, for the kinetics of collagen turnover as a function of altered mechanical loading and we do not know what governs the orientation and pre-stretch at which new fibers are incorporated within extant tissue. In this paper, we use a constrained mixture theory for growth and remodeling of planar soft tissues to motivate a new experimental approach for investigating competing hypotheses on, for example, how new collagen is aligned by synthetic cells. In particular, because stress and strain fields can be homogeneous in a central region of a biaxially tested tissue, and because biaxial testing admits diverse protocols wherein equal stresses can be imposed in the presence of unequal strains or stresses can be maintained in the absence of strain, we report simulations that illustrate the potential utility of biaxial culture studies. Finally, we describe the associated design of a computer-controlled system that allows intravital microscopic quantification of collagen density, orientation, and cross-linking at various stages during the adaptation of a native tissue or the development of a tissue engineered equivalent, each subjected to well controlled biaxial loads.

Human melanoma cells expressing V600E B-RAF are susceptible to IGF1R targeting by small interfering RNAs.

The type 1 insulin-like growth factor receptor (IGF1R) is overexpressed by malignant melanomas compared with benign naevi, and mediates proliferation, motility and protection from apoptosis. However, the utility of IGF1R targeting as anti-cancer therapy may be limited by activating mutations in downstream signaling intermediates. We previously showed that IGF1R knockdown blocked survival of prostate cancer cells in which Akt activation was deregulated by PTEN loss. The current study investigated effects of IGF1R targeting in cells harboring activating RAS-RAF mutations, found in 70-80% of human melanomas. We assembled a panel of eight human melanoma cell lines: two expressing wild-type (WT) B-RAF and N-RAS, two with activating N-RAS mutations and four harboring V600E B-RAF. We also generated isogenic cell populations overexpressing WT or V600E B-RAF. Cells expressing V600E B-RAF were relatively resistant to apoptosis. However, IGF1R gene silencing was capable of inducing significant inhibition of survival, enhancement of apoptosis, and approximately two-fold sensitization to cisplatin and temozolomide. These effects were independent of mutation status and were associated with reduced activation of Akt and also, unexpectedly, of ERKs. These results support development of IGF1R targeting as therapy for melanoma, regardless of the presence of activating mutations in the RAS-RAF pathway.

Expression and function of the ghrelin axis, including a novel preproghrelin isoform, in human breast cancer tissues and cell lines.

While oestrogen, progesterone and growth factors, including growth hormone (GH), are clearly implicated in the pathogenesis of breast cancer, there is now evidence that the newly described ghrelin axis is also involved. The aims of this study were to investigate the expression of the ghrelin axis in breast cancer tissues and cell lines and to examine the effect of ghrelin on breast cancer cell proliferation in vitro. Ghrelin and its functional receptor, the growth hormone secretagogue receptor (GHSR) type 1a, were expressed in normal breast tissue and breast cancer specimens and cell lines. In contrast, the truncated GHSR type 1b isoform was exclusively expressed in breast carcinoma, suggesting that it has potential as a diagnostic marker. Ghrelin treatment significantly increases the proliferation of the MDA-MB-435 and MDA-MB-231 breast cancer cell lines in vitro. In addition, we have described the expression of a human preproghrelin isoform, exon 3-deleted preproghrelin, which encodes mature ghrelin plus a novel C-terminal peptide. Quantitative RT-PCR was used to demonstrate that this mRNA isoform is highly expressed in the MDA-MB-435 metastatic breast cancer cell line relative to the benign MCF-10A breast epithelial cell line. The unique C-terminal peptide of exon 3-deleted preproghrelin is expressed in the glandular epithelium of breast cancer tissues, with high-grade carcinoma exhibiting the strongest immunoreactivity. The data presented here suggest that components of the ghrelin axis may represent novel markers for breast cancer and potential therapeutic targets.

Acute mediastinitis resulting from an unsuspected fish bone--case report.

Acute mediastinitis is a serious medical condition with a mortality rate from 30 to 40% or even higher. Early diagnosis with prompt and aggressive treatment is essential to prevent its rapid progression. Severe odynophagia and respiratory distress with positive neck or chest findings should raise suspicion of mediastinitis. We report a rare case of acute mediastinitis secondary to the unexpected migration of an impacted fish bone from the esophagus.

Socio-demographic and geographic indicators and distribution of tuberculosis in Hong Kong: a spatial analysis.

OBJECTIVE: To determine the socio-demographic and geographic indicators responsible for the distribution and transmission of tuberculosis (TB) in Hong Kong using geographical information system (GIS) technology. MATERIALS AND METHODS: All patients with bacteriologically proven TB over a period of 3 years (May 1999-April 2002) residing within Hong Kong Island were studied. Molecular characterisation of their sputum isolates by IS6110-based restriction fragment length polymorphism (RFLP) technique was performed. Socio-demographic data were derived from the 2001 Hong Kong population census. Geographic coordinates of patients' addresses were linked to the GIS; large street block groups (LSBGs) were the units of analysis. RESULTS: Of 2387 patients with bacteriologically confirmed TB, 2332 had valid addresses distributed in 430 LSBGs in Hong Kong Island. Of the five socio-demographic indicators studied, significant correlations were found between the rate of TB in an LSBG and low educational attainment, elderly population and low-income household, but not population density or unemployment. The five socio-demographic indicators were not different between LSBG with clustered cases and those with unique cases. CONCLUSION: Low educational attainment, old age and poverty were significant determinants of the rate of TB in different parts of Hong Kong, while none of the socio-demographic indicators was related to disease transmission.

Expression of the ghrelin axis in the mouse: an exon 4-deleted mouse proghrelin variant encodes a novel C terminal peptide.

Ghrelin, an n-octanoylated 28-amino-acid peptide capable of inducing GH secretion and food intake in humans and rats, is the endogenous ligand for the GH secretagogue receptor (GHS-R). Here we describe the expression and tissue distribution of the ghrelin/GHS-R axis in the mouse. We also report for the first time the identification of a novel mouse ghrelin mRNA variant in which there is a complete deletion of exon 4. Translation of this variant mRNA yields a protein containing ghrelin and an alternative C-terminal domain with a unique C-terminal peptide sequence. RT-PCR with primers specific for mouse ghrelin was used to demonstrate the mRNA expression of the full preproghrelin transcript and the exon 4-deleted variant in multiple mouse tissues. Real-time PCR was also employed to quantitate mRNA expression of ghrelin, the novel isoform and a previously reported ghrelin gene variant, ghrelin gene-derived transcript. We also demonstrated the tissue expression of the functional GHS-R in the mouse. Immunohistochemistry, employing antibodies raised against the mature human n-octanoylated ghrelin peptide and the putative C-terminal peptide encoded by the exon 4-deleted proghrelin variant, was used to demonstrate protein expression of ghrelin and the variant in multiple mouse tissues including stomach, kidney, and reproductive tissues. The coexpression of ghrelin and its receptor in a wide range of murine tissues suggests varied autocrine/paracrine roles for these peptides. Exon 4-deleted proghrelin, a novel mouse proghrelin isoform with a unique C-terminal peptide sequence, is also widely expressed in the mouse and thus may possess biological activity in these tissues.

Quantum phase transition in a common metal.

The classical theory of solids, based on the quantum mechanics of single electrons moving in periodic potentials, provides an excellent description of substances ranging from semiconducting silicon to superconducting aluminium. Over the last fifteen years, it has become increasingly clear that there are substances for which the conventional approach fails. Among these are certain rare earth compounds and transition metal oxides, including high-temperature superconductors. A common feature of these materials is complexity, in the sense that they have relatively large unit cells containing heterogeneous mixtures of atoms. Although many explanations have been put forward for their anomalous properties, it is still possible that the classical theory might suffice. Here we show that a very common chromium alloy has some of the same peculiarities as the more exotic materials, including a quantum critical point, a strongly temperature-dependent Hall resistance and evidence for a 'pseudogap'. This implies that complexity is not a prerequisite for unconventional behaviour. Moreover, it should simplify the general task of explaining anomalous properties because chromium is a relatively simple system in which to work out in quantitative detail the consequences of the conventional theory of solids.

Oxidative dehydrogenation on the alpha-carbon of 4-pyridylacetonitrile complexes of pentaammineruthenium(II).

The oxidation of Ru(NH(3))(5)NCCH(2)py(2+) in 0.10 M HCl turns the solution from yellow to greenish blue with an absorption at lambda = 791 nm. The absorbance reaches its maximum value when the complex undergoes a two-electron oxidation. The IR and (1)H NMR spectra of the product indicate that the metal center remains as Ru(II) and that the ligand is oxidized. The (13)C NMR spectral results suggest that the oxidation product is [(NH(3))(5)RuNCC(pyH)C(pyH)CNRu(NH(3))(5)](ClO(4))(6). Cyclic voltammetry of the product solution also indicates that the oxidation proceeds in two one-electron steps corresponding to [Ru(III),Ru(II)] + e(-) <= => [Ru(II),Ru(II)] and [Ru(III),Ru(III)] + e(-) <= => [Ru(III),Ru(II)]. The structure of the product in deprotonated form [(NH(3))(5)RuNCC(py)C(py)CNRu(NH(3))(5)](ClO(4))(4)(H(2)O)(2) was determined crystallographically. [(NH(3))(5)RuNCC(py)C(py)CNRu(NH(3))(5)](ClO(4))(4)(H(2)O)(2) crystallizes in the orthorhombic Pbca space group with cell constants a = 13.7138 (16) A, b = 15.7553 (18) A, c = 17.831(2) A, and Z = 4. A mechanism for the oxidation has been proposed on the basis of the kinetic studies in the region of 0.01-0.20 M acid concentrations.

Crystal structure of the Acidaminococcus fermentans 2-hydroxyglutaryl-CoA dehydratase component A.

Acidaminococcus fermentans degrades glutamate via the hydroxyglutarate pathway, which involves the syn-elimination of water from (R)-2-hydroxyglutaryl-CoA in a key reaction of the pathway. This anaerobic process is catalyzed by 2-hydroxyglutaryl-CoA dehydratase, an enzyme with two components (A and D) that reversibly associate during reaction cycles. Component A (CompA), a homodimeric protein of 2x27 kDa, contains a single, bridging [4Fe-4S] cluster and uses the hydrolysis of ATP to deliver an electron to the dehydratase component (CompD), where the electron is used catalytically. The structure of the extremely oxygen-sensitive CompA protein was solved by X-ray crystallography to 3 A resolution. The protein was found to be a member of the actin fold family, revealing a similar architecture and nucleotide-binding site. The key differences between CompA and other members of the actin fold family are: (i) the presence of a cluster binding segment, the "cluster helix"; (ii) the [4Fe-4S] cluster; and (iii) the location of the homodimer interface, which involves the bridging cluster. Possible reaction mechanisms are discussed in light of the close structural similarity to members of the actin-fold family and the functional similarity to the nitrogenase Fe- protein.