Replica filter assay of human beta-adrenergic receptors expressed in E.coli

We have developed a replica filter assay that permits the direct identification of bacterial colonies expressing membrane receptors. E.coli transformed with appropriate phage or plasmid vectors containing human beta-adrenergic receptor cDNAs were grown on LB/agar plates. Bacterial colonies transferred onto nitrocellulose filters showed specific [125I]-iodocyanopindolol binding. beta-adrenergic receptors expressed in bacteria retained their pharmacological properties when transferred onto filters. This strategy, which is considerably simplified and more rapid compared to similar methods based upon expression of receptor genes in eukaryotic cells, may be a useful tool for cloning membrane receptors.     

Functional Properties of the Retinal Glutamate Transporters GLT-1c and EAAT5

In the mammalian retina, glutamate uptake is mediated by members of a family of glutamate transporters known as “excitatory amino acid transporters (EAATs).” Here we cloned and functionally characterized two retinal EAATs from mouse, the GLT-1/EAAT2 splice variant GLT-1c, and EAAT5. EAATs are glutamate transporters and anion-selective ion channels, and we used heterologous expression in mammalian cells, patch-clamp recordings and noise analysis to study and compare glutamate transport and anion channel properties of both EAAT isoforms. We found GLT-1c to be an effective glutamate transporter with high affinity for Na⁺ and glutamate that resembles original GLT-1/EAAT2 in all tested functional aspects. EAAT5 exhibits glutamate transport rates too low to be accurately measured in our experimental system, with significantly lower affinities for Na⁺ and glutamate than GLT-1c. Non-stationary noise analysis demonstrated that GLT-1c and EAAT5 also differ in single-channel current amplitudes of associated anion channels. Unitary current amplitudes of EAAT5 anion channels turned out to be approximately twice as high as single-channel amplitudes of GLT-1c. Moreover, at negative potentials open probabilities of EAAT5 anion channels were much larger than for GLT-1c. Our data illustrate unique functional properties of EAAT5, being a low-affinity and low-capacity glutamate transport system, with an anion channel optimized for anion conduction in the negative voltage range.     

Modulation of endothelial cell proliferation,adhesion, and motility by recombinant heparin-binding domain and synthetic peptides from the type I repeats of thrombospondin

Thrombospondin is an inhibitor of angiogenesis that modulates endothelial cell adhesion, proliferation, and motility. Synthetic peptides from the second type I repeat of human thrombospondin containing the consensus sequence -Trp-Ser-Pro-Trp- and a recombinant heparin binding fragment from the amino-terminus of thrombospondin mimic several of the activities of the intact protein. The peptides and heparin-binding domain promote endothelial cell adhesion, inhibit endothelial cell chemotaxis to basic fibroblast growth factor (bFGF), and inhibit mitogenesis and proliferation of aortic and corneal endothelial cells. The peptides also inhibit heparin-dependent binding of bFGF to corneal endothelial cells. The antiproliferative activities of the peptides correlate with their ability to bind to heparin and to inhibit bFGF binding to heparin. Peptides containing amino acid substitutions that eliminate heparin-binding do not alter chemotaxis or proliferation of endothelial cells. Inhibition of proliferation by the peptide is time-dependet and reversible. Thus, the antiproliferative activities of the thrombospondin peptides and recombinant heparin-binding domain result at least in part from competition with heparin-dependent growth factors for binding to endothelial cell proteoglycans. These results suggest that both the Trp-Ser-Xaa-Trp sequences in the type I repeats and the amino-terminal domain play roles in the antiproliferative activity of thrombospondin.     

Mast cell-dependent amplification of an immunologically nonspecific inflammatory response. Mast cells are required for the full expression of cutaneous acute inflammation induced by phorbol 12-myristate 13-acetate

Mast cells clearly are critical for the expression of some IgE-dependent responses, but their roles in other forms of inflammation are uncertain. We previously described a new model system for defining the unique contribution of mast cells to biologic responses in vivo, genetically mast cell-deficient WBB6F1-W/Wv mice that have undergone selective local repair of their mast cell deficiency by the injection of IL-3-dependent cultured mast cells derived from the congenic normal (WBB6F1-+/+) mice. Using this approach, we analyzed the contribution of mast cells to the acute inflammation induced by the epicutaneous application of PMA. Even though PMA can activate a wide variety of cell types that may contribute to acute inflammation, we found that mast cells were required for the full expression of the tissue swelling and leukocyte infiltration associated with the response to the agent in vivo. Thus, in WBB6F1-W/Wv mice selectively reconstituted with dermal mast cells by intradermal injection of cultured WBB6F1-+/+ mast cells into the left ear only, PMA induced approximately twice the tissue swelling and neutrophil infiltration in the mast cell-reconstituted left ears as in the contralateral control ears. This represents the first use of W/Wv mice locally reconstituted with mast cells to confirm the hypothesis that mast cells can represent an important amplification mechanism in acute inflammatory responses of nonimmunologic origin. It also defines a model system that may be generally useful for investigating mast cell-dependent and -independent aspects of acute inflammatory responses.     

Effects of weather and hunting on wild reindeer population dynamics in Hardangervidda National Park

Wild reindeer have a range that extends across the circumpolar region. In the last few decades, however, populations of wild reindeer have been on the decline. The reasons for these declines are poorly understood, but are suggested to be linked to both local and global climatic factors, disease, and human interference. Hardangervidda plateau in Norway is home to the largest wild reindeer population in Europe, and is at the southern end of its European range. This population is therefore of particular importance, particularly in the light of climate change. We investigated how weather and hunting have affected the wild reindeer population in Hardangervidda over the last two decades. Our findings suggest that the wild reindeer population in Hardangervidda is most affected by winter temperature and hunting, where colder temperatures and lower harvest rates typically result in higher growth rates. We did not find significant evidence for linear density dependence. Our results show trends across Hardangervidda, and give an indication of how region-wide weather and hunting pressure can affect the wild reindeer population. As new data emerge, future investigations should look into the existence and nature of density dependence and the influence of other weather and human disturbance related factors.     

Role of two sequence motifs of mesencephalic astrocyte-derived neurotrophic factor in its survival-promoting activity

Mesencephalic astrocyte-derived neurotrophic factor (MANF) is a prosurvival protein that protects the cells when applied intracellularly in vitro or extracellularly in vivo. Its protective mechanisms are poorly known. Here we studied the role of two short sequence motifs within the carboxy-(C) terminal domain of MANF in its neuroprotective activity: the CKGC sequence (a CXXC motif) that could be involved in redox reactions, and the C-terminal RTDL sequence, an endoplasmic reticulum (ER) retention signal. We mutated these motifs and analyzed the antiapoptotic effect and intracellular localization of these mutants of MANF when overexpressed in cultured sympathetic or sensory neurons. As an in vivo model for studying the effect of these mutants after their extracellular application, we used the rat model of cerebral ischemia. Even though we found no evidence for oxidoreductase activity of MANF, the mutation of CXXC motif completely abolished its protective effect, showing that this motif is crucial for both MANF''s intracellular and extracellular activity. The RTDL motif was not needed for the neuroprotective activity of MANF after its extracellular application in the stroke model in vivo. However, in vitro the deletion of RTDL motif inactivated MANF in the sympathetic neurons where the mutant protein localized to Golgi, but not in the sensory neurons where the mutant localized to the ER, showing that intracellular MANF protects these peripheral neurons in vitro only when localized to the ER.The prosurvival proteins that actively keep the cells alive function as a counterbalance to the prodeath programs of the cell and are thereby essential players in morphogenesis and adult tissue homeostasis. Such survival-promoting proteins are also potential candidates for the treatment of pathological conditions, especially in the nervous system where the lost neurons are only rarely replaced by new ones. Some prosurvival proteins act extracellularly. For example, neurotrophic factors (NTFs) are secreted proteins that bind the cognate receptors on the surface of the cells, thereby triggering prosurvival signaling cascades.^{1, 2, 3} Other prosurvival proteins, such as Akt kinase, antiapoptotic Bcl2 family members, inhibitor of apoptosis (IAP) proteins and so on are not secreted and protect the cells intracellularly. A new family of survival-promoting proteins has recently been described⁴ that can act in both ways. This family consists of two proteins, mesencephalic astrocyte-derived neurotrophic factor (MANF)⁵ and cerebral dopamine neurotrophic factor (CDNF).⁶ Both factors, when delivered into the extracellular space of the brain or applied via viral vectors potently antagonize neurological damage in the rodent models of Parkinson''s disease. MANF is also protective against cerebral ischemia^{6, 7, 8, 9, 10} and prevents degeneration of Purkinje cells in spinocerebellar ataxia.¹¹ In these experiments, MANF and CDNF halted the death of the neurons and also stimulated regrowth of the dopaminergic fibers, acting thus as typical NTFs. On the other hand in non-neuronal cells, MANF was also shown to be a resident protein of the endoplasmic reticulum (ER) protecting the cells intracellularly against ER stress.^{12, 13, 14, 15, 16, 17}In line with its role in counteracting cell death, MANF promotes pancreatic β-cell proliferation and survival in vivo, and lack of MANF leads to chronic unfolded protein response (UPR) activation in pancreatic islets.¹⁸ We have also shown that microinjected intracellular MANF protects cultured sympathetic neurons of the superior cervical ganglion (SCG) against apoptosis-inducing toxins, whereas it does not protect or bind these neurons when applied to the culture medium.¹⁹ Thus, MANF can protect the neurons when applied extracellularly (at least in vivo) and intracellularly. Of note, MANF also has both intra- and extracellular activities on the pancreatic β cells.¹⁸ However, the mechanisms of intra- and extracellular action of MANF are currently not well defined.Structurally MANF consists of amino- (N) terminal saposin-like domain and carboxy-(C) terminal SAP domain-like domain that are connected by a flexible linker.^{19, 20} From the amino-acid sequence and structure, two potentially functional motifs can be distinguished in the carboxy-terminal domain of MANF (C-MANF).^{19, 20} First, a conserved^{21, 22} CXXC motif (CKGC) was found in the loop connecting the helices α7 and α8 where two cysteines were connected with a disulfide bond. The CXXC motif is found in the active center of the enzymes of thiol-disulfide oxidoreductase superfamily.²³ Second, a conserved RTDL sequence belonging to the class of KDEL-like ER retention signal²⁴ is found at the very end of C terminus of MANF^{19, 20} and is shown to be required for its retrieval from the Golgi to ER.^{15, 16, 25} The role of the RTDL motif in the survival-promoting activity of MANF has not been studied.In this study, we set up to investigate the importance of these motifs of MANF for its survival-promoting activity both in the intracellular in vitro as well as extracellular in vivo paradigms. We mutated the CXXC and RTDL motifs and tested the activity of the mutants by microinjecting plasmid DNAs encoding the mutant proteins into apoptotic sympathetic SCG neurons, our validated model for testing the neuroprotective bioactivity of MANF,^{19, 21} and sensory dorsal root ganglion (DRG) neurons. Subcellular localization of the MANF mutants was also studied in the same neurons. We show that the CXXC motif is critically required for the survival-promoting activity of MANF, as mutation of this motif prevents MANF from being neuroprotective in both types of neurons in vitro and also in the in vivo rat model of cerebral ischemia. In addition, we show, using the same in vivo model, that the RTDL motif is not required for the neuroprotective activity of extracellularly applied MANF. However, intracellularly the mutant without RTDL motif was inactive only when it was not retrieved to the ER.     

Overhydration,Cardiac Function and Survival in Hemodialysis Patients

Background and objectives

Chronic subclinical volume overload occurs very frequently and may be ubiquitous in hemodialysis (HD) patients receiving the standard thrice-weekly treatment. It is directly associated with hypertension, increased arterial stiffness, left ventricular hipertrophy, heart failure, and eventually, higher mortality and morbidity. We aimed to assess for the first time if the relationship between bioimpedance assessed overhydration and survival is maintained when adjustments for echocardiographic parameters are considered.

Design, setting, participants and measurements

A prospective cohort trial was conducted to investigate the impact of overhydration on all cause mortality and cardiovascular events (CVE), by using a previously reported cut-off value for overhydration and also investigating a new cut-off value derived from our analysis of this specific cohort. The body composition of 221 HD patients from a single center was assessed at baseline using bioimpedance. In 157 patients supplemental echocardiography was performed (echocardiography subgroup). Comparative survival analysis was performed using two cut-off points for relative fluid overload (RFO): 15% and 17.4% (a value determined by statistical analysis to have the best predictive value for mortality in our cohort).

Results

In the entire study population, patients considered overhydrated (using both cut-offs) had a significant increased risk for all-cause mortality in both univariate (HR = 2.12, 95%CI = 1.30–3.47 for RFO>15% and HR = 2.86, 95%CI = 1.72–4.78 for RFO>17.4%, respectively) and multivariate (HR = 1.87, 95%CI = 1.12–3.13 for RFO>15% and HR = 2.72, 95%CI = 1.60–4.63 for RFO>17.4%, respectively) Cox survival analysis. In the echocardiography subgroup, only the 17.4% cut-off remained associated with the outcome after adjustment for different echocardiographic parameters in the multivariate survival analysis. The number of CVE was significantly higher in overhydrated patients in both univariate (HR = 2.46, 95%CI = 1.56–3.87 for RFO >15% and HR = 3.67, 95%CI = 2.29–5.89 for RFO >17.4%) and multivariate (HR = 2.31, 95%CI = 1.42–3.77 for RFO >15% and HR = 4.17, 95%CI = 2.48–7.02 for RFO >17.4%) Cox regression analysis.

Conclusions

The study shows that the hydration status is associated with the mortality risk in a HD population, independently of cardiac morphology and function. We also describe and propose a new cut-off for RFO, in order to better define the relationship between overhydration and mortality risk. Further studies are needed to properly validate this new cut-off in other HD populations.     

Non-Adrenergic Vasopressors in Patients with or at Risk for Vasodilatory Shock. A Systematic Review and Meta-Analysis of Randomized Trials

Introduction

Hypotensive state is frequently observed in several critical conditions. If an adequate mean arterial pressure is not promptly restored, insufficient tissue perfusion and organ dysfunction may develop. Fluids and catecholamines are the cornerstone of critical hypotensive states management. Catecholamines side effects such as increased myocardial oxygen consumption and development of arrhythmias are well known. Thus, in recent years, interest in catecholamine-sparing agents such as vasopressin, terlipressin and methylene blue has increased; however, few randomized trials, mostly with small sample sizes, have been performed. We therefore conducted a meta-analysis of randomized trials to investigate the effect of non-catecholaminergic vasopressors on mortality.

Methods

PubMed, BioMed Central and Embase were searched (update December 31^st, 2014) by two independent investigators. Inclusion criteria were: random allocation to treatment, at least one group receiving a non-catecholaminergic vasopressor, patients with or at risk for vasodilatory shock. Exclusion criteria were: crossover studies, pediatric population, non-human studies, studies published as abstract only, lack of data on mortality. Studied drugs were vasopressin, terlipressin and methylene blue. Primary endpoint was mortality at the longest follow-up available.

Results

A total of 1,608 patients from 20 studies were included in our analysis. The studied settings were sepsis (10/20 studies [50%]), cardiac surgery (7/20 [35%]), vasodilatory shock due to any cause (2/20 [19%]), and acute traumatic injury (1/20 [5%]). Overall, pooled estimates showed that treatment with non-catecholaminergic agents improves survival (278/810 [34.3%] versus 309/798 [38.7%], risk ratio = 0.88, 95% confidence interval = 0.79 to 0.98, p = 0.02). None of the drugs was associated with significant reduction in mortality when analyzed independently. Results were not confirmed when analyzing studies with a low risk of bias.

Conclusions

Catecholamine-sparing agents in patients with or at risk for vasodilatory shock may improve survival. Further researches on this topic are needed to confirm the finding.     

Acute Modulation of Brain Connectivity in Parkinson Disease after Automatic Mechanical Peripheral Stimulation: A Pilot Study

Objective

The present study shows the results of a double-blind sham-controlled pilot trial to test whether measurable stimulus-specific functional connectivity changes exist after Automatic Mechanical Peripheral Stimulation (AMPS) in patients with idiopathic Parkinson Disease.

Methods

Eleven patients (6 women and 5 men) with idiopathic Parkinson Disease underwent brain fMRI immediately before and after sham or effective AMPS. Resting state Functional Connectivity (RSFC) was assessed using the seed-ROI based analysis. Seed ROIs were positioned on basal ganglia, on primary sensory-motor cortices, on the supplementary motor areas and on the cerebellum. Individual differences for pre- and post-effective AMPS and pre- and post-sham condition were obtained and first entered in respective one-sample t-test analyses, to evaluate the mean effect of condition.

Results

Effective AMPS, but not sham stimulation, induced increase of RSFC of the sensory motor cortex, nucleus striatum and cerebellum. Secondly, individual differences for both conditions were entered into paired group t-test analysis to rule out sub-threshold effects of sham stimulation, which showed stronger connectivity of the striatum nucleus with the right lateral occipital cortex and the cuneal cortex (max Z score 3.12) and with the right anterior temporal lobe (max Z score 3.42) and of the cerebellum with the right lateral occipital cortex and the right cerebellar cortex (max Z score 3.79).

Conclusions

Our results suggest that effective AMPS acutely increases RSFC of brain regions involved in visuo-spatial and sensory-motor integration.

Classification of Evidence

This study provides Class II evidence that automatic mechanical peripheral stimulation is effective in modulating brain functional connectivity of patients with Parkinson Disease at rest.

Trial Registration

Clinical Trials.gov NCT01815281