A high affinity interaction of plasminogen with fibrin is not essential for efficient activation by tissue-type plasminogen activator

Fibrin (Fn) enhances plasminogen (Pg) activation by tissue-type plasminogen activator (tPA) by serving as a template onto which Pg and tPA assemble. To explore the contribution of the Pg/Fn interaction to Fn cofactor activity, Pg variants were generated and their affinities for Fn were determined using surface plasmon resonance (SPR). Glu-Pg, Lys-Pg (des(1-77)), and Mini-Pg (lacking kringles 1-4) bound Fn with K(d) values of 3.1, 0.21, and 24.5 μm, respectively, whereas Micro-Pg (lacking all kringles) did not bind. The kinetics of activation of the Pg variants by tPA were then examined in the absence or presence of Fn. Whereas Fn had no effect on Micro-Pg activation, the catalytic efficiencies of Glu-Pg, Lys-Pg, and Mini-Pg activation in the presence of Fn were 300- to 600-fold higher than in its absence. The retention of Fn cofactor activity with Mini-Pg, which has low affinity for Fn, suggests that Mini-Pg binds the tPA-Fn complex more tightly than tPA alone. To explore this possibility, SPR was used to examine the interaction of Mini-Pg with Fn in the absence or presence of tPA. There was 50% more Mini-Pg binding to Fn in the presence of tPA than in its absence, suggesting that formation of the tPA-Fn complex exposes a cryptic site that binds Mini-Pg. Thus, our data (a) indicate that high affinity binding of Pg to Fn is not essential for Fn cofactor activity, and (b) suggest that kringle 5 localizes and stabilizes Pg within the tPA-Fn complex and contributes to its efficient activation.     

Role of secretory carrier membrane protein SCAMP2 in granule exocytosis

In secretory carrier membrane proteins (SCAMPs), the most conserved structural segment is between transmembrane spans 2 and 3, facing the cytosol. A synthetic peptide, CWYRPIYKAFR (E peptide), from this segment of SCAMP2 potently inhibits exocytosis in permeabilized neuroendocrine (PC12) cells. E peptide blocked discharge of (35)S-labeled secretogranin with the same structural selectivity and potency as observed for hexosaminidase secretion in mast cells. SCAMPs 1 and 2 are concentrated primarily on intracellular membranes in PC12 cells. Both, however, are found on plasma membranes, but neither is present on large dense-core vesicles. Yet, large dense-core vesicles marked by secretogranin attach to plasma membranes at foci containing SCAMP2 along with syntaxin1 and complexin at putative cell-surface docking/fusion sites. Regulated overexpression of SCAMP2 with point mutations in its E peptide but not of normal SCAMP2 caused dose-dependent inhibition of depolarization-induced secretion. The SCAMP2 mutants also inhibited secretion stimulated by elevated calcium. Inhibition was largely overcome by adding lysophosphatidylcholine to the medium at concentrations that do not otherwise affect secretion. Although overexpression of normal or mutant SCAMP2 slightly inhibits endocytosis, this effect does not appear to be related to the specific effect of the mutant SCAMP on stimulated exocytosis. Thus, SCAMP2 not only colocalizes with fusion sites but also appears to have an essential function in granule exocytosis through actions mediated by its E peptide-containing domain.     

Predictive markers for the early prognosis of dengue severity: A systematic review and meta-analysis

BackgroundPredictive markers represent a solution for the proactive management of severe dengue. Despite the low mortality rate resulting from severe cases, dengue requires constant examination and round-the-clock nursing care due to the unpredictable progression of complications, posing a burden on clinical triage and material resources. Accordingly, identifying markers that allow for predicting disease prognosis from the initial diagnosis is needed. Given the improved pathogenesis understanding, myriad candidates have been proposed to be associated with severe dengue progression. Thus, we aim to review the relationship between the available biomarkers and severe dengue.MethodologyWe performed a systematic review and meta-analysis to compare the differences in host data collected within 72 hours of fever onset amongst the different disease severity levels. We searched nine bibliographic databases without restrictive criteria of language and publication date. We assessed risk of bias and graded robustness of evidence using NHLBI quality assessments and GRADE, respectively. This study protocol is registered in PROSPERO (CRD42018104495).Principal findingsOf 4000 records found, 40 studies for qualitative synthesis, 19 for meta-analysis. We identified 108 host and viral markers collected within 72 hours of fever onset from 6160 laboratory-confirmed dengue cases, including hematopoietic parameters, biochemical substances, clinical symptoms, immune mediators, viral particles, and host genes. Overall, inconsistent case classifications explained substantial heterogeneity, and meta-analyses lacked statistical power. Still, moderate-certainty evidence indicated significantly lower platelet counts (SMD -0.65, 95% CI -0.97 to -0.32) and higher AST levels (SMD 0.87, 95% CI 0.36 to 1.38) in severe cases when compared to non-severe dengue during this time window.ConclusionThe findings suggest that alterations of platelet count and AST level—in the first 72 hours of fever onset—are independent markers predicting the development of severe dengue.     

Neurotransmitter alterations in embryonic succinate semialdehyde dehydrogenase (SSADH) deficiency suggest a heightened excitatory state during development

Background  

SSADH (aldehyde dehydrogenase 5a1 (Aldh5a1); γ-hydroxybutyric (GHB) aciduria) deficiency is a defect of GABA degradation in which the neuromodulators GABA and GHB accumulate. The human phenotype is that of nonprogressive encephalopathy with prominent bilateral discoloration of the globi pallidi and variable seizures, the latter displayed prominently in Aldh5a1^-/- mice with lethal convulsions. Metabolic studies in murine neural tissue have revealed elevated GABA [and its derivatives succinate semialdehyde (SSA), homocarnosine (HC), 4,5-dihydroxyhexanoic acid (DHHA) and guanidinobutyrate (GB)] and GHB [and its analogue D-2-hydroxyglutarate (D-2-HG)] at birth. Because of early onset seizures and the neurostructural anomalies observed in patients, we examined metabolite features during Aldh5a1^-/- embryo development.     

MPTP as a Mitochondrial Neurotoxic Model of Parkinson's Disease

1-Methy-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a potent neurotoxin extensively used to model Parkinson's disease (PD). A cascade of deleterous events, in which mitochondria play a pivotal role, drives MPTP neurotoxicity. How mitochondria are affected by MPTP and how their defect contributes to the demise of dopaminergic neurons in this model of PD are discussed in this review.     

The Interaction of Heat and Smoke in the Release of Seed Dormancy in Seven Species from Southwestern Western Australia

Exposure to high temperatures (40–60 °C) over severaldays to months (simulating summer soil conditions) or to extremelyhigh temperatures (80–120 °C) for periods rangingfrom minutes to several days (simulating the heat of an extremefire) promoted germination in five (including one legume species)of the seven species tested from southwestern Australia. Heat,a collective term for high temperature (HT) and extremely hightemperature (EHT), has previously been used to promote germinationin species with impermeable seed coats (many of which are legumes).If heat is found to promote germination in species with permeableseed coats, it could be of use in the release of dormancy forcommercial development of native plants. Here we report thatelevated storage temperatures (50 °C for 45 and 90 d or60 °C for 45 d) and EHT (100 °C for 3 h and 120 °Cfor 30 min) alone, and in addition to smoke, directly promotegermination of the refractory species Actinotus leucocephalus,Anigozanthos manglesii, Gompholobium knightianum, Loxocaryastriatus and Stylidium affine. Germination of Sowerbaea laxifloraseed was not improved with heat alone but was improved by thecombination of heat and smoke. Seed of Schoenus unispiculatusdid not germinate in response to any of the treatments. Interactionsbetween the effect of temperature, the duration of heat exposureor smoke were detected in all species. Whilst most species demonstratedan interaction between heat and time, not all species were affectedby smoke alone. This was illustrated by an interaction betweensmoke and HT found only in Actinotus leucocephalus, Anigozanthosmanglesii and Stylidium affine or smoke and EHT in A. manglesiiandS. affine . Smoke and exposure time to heat influenced thegermination of Actinotus leucocephalus,Anigozanthos manglesiiand L. striatus in response to HT and only S. affine appearedto demonstrate an interaction between smoke and EHT. The variationsfound in the interactions between treatments suggest that germinationevents occur over a range of conditions both spatially and temporallywhich may facilitate seedling survival and limit competitionbetween emergents. Copyright 2001 Annals of Botany Company Smoke, heat, fire, seedbank, seed dormancy, seed germination, Western Australia     

Sexual Behavior and Network Characteristics and Their Association with Bacterial Sexually Transmitted Infections among Black Men Who Have Sex with Men in the United States

Background

Black men who have sex with men (MSM) have a high prevalence of bacterial sexually transmitted infections (STIs), and individual risk behavior does not fully explain the higher prevalence when compared with other MSM. Using the social-ecological framework, we evaluated individual, social and sexual network, and structural factors and their association with prevalent STIs among Black MSM.

Methods

The HIV Prevention Trials Network 061 was a multi-site cohort study designed to determine the feasibility and acceptability of a multi-component intervention for Black MSM in six US cities. Baseline assessments included demographics, risk behavior, and social and sexual network questions collected information about the size, nature and connectedness of their sexual network. Logistic regression was used to estimate the odds of having any prevalent sexually transmitted infection (gonorrhea, chlamydia, or syphilis).

Results

A total of 1,553 Black MSM were enrolled in this study. In multivariate analysis, older age (aOR = 0.57; 95% CI 0.49–0.66, p<0.001) was associated with a lower odds of having a prevalent STI. Compared with reporting one male sexual partner, having 2–3 partners (aOR = 1.74; 95% CI 1.08–2.81, p<0.024) or more than 4 partners (aOR = 2.29; 95% CI 1.43–3.66, p<0.001) was associated with prevalent STIs. Having both Black and non-Black sexual partners (aOR = 0.67; 95% CI 0.45–0.99, p = 0.042) was the only sexual network factor associated with prevalent STIs.

Conclusions

Age and the number and racial composition of sexual partners were associated with prevalent STIs among Black MSM, while other sexual network factors were not. Further studies are needed to evaluate the effects of the individual, network, and structural factors on prevalent STIs among Black MSM to inform combination interventions to reduce STIs among these men.     

Sexual Networks and HIV Risk among Black Men Who Have Sex with Men in 6 U.S. Cities

Background

Sexual networks may place U.S. Black men who have sex with men (MSM) at increased HIV risk.

Methods

Self-reported egocentric sexual network data from the prior six months were collected from 1,349 community-recruited Black MSM in HPTN 061, a multi-component HIV prevention intervention feasibility study. Sexual network composition, size, and density (extent to which members are having sex with one another) were compared by self-reported HIV serostatus and age of the men. GEE models assessed network and other factors associated with having a Black sex partner, having a partner with at least two age category difference (age difference between participant and partner of at least two age group categories), and having serodiscordant/serostatus unknown unprotected anal/vaginal intercourse (SDUI) in the last six months.

Results

Over half had exclusively Black partners in the last six months, 46% had a partner of at least two age category difference, 87% had ≤5 partners. Nearly 90% had sex partners who were also part of their social networks. Among HIV-negative men, not having anonymous/exchange/ trade partners and lower density were associated with having a Black partner; larger sexual network size and having non-primary partners were associated with having a partner with at least two age category difference; and having anonymous/exchange/ trade partners was associated with SDUI. Among HIV-positive men, not having non-primary partners was associated with having a Black partner; no sexual network characteristics were associated with having a partner with at least two age category difference and SDUI.

Conclusions

Black MSM sexual networks were relatively small and often overlapped with the social networks. Sexual risk was associated with having non-primary partners and larger network size. Network interventions that engage the social networks of Black MSM, such as interventions utilizing peer influence, should be developed to address stable partnerships, number of partners, and serostatus disclosure.